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Environmental
Microbiology

1

Microbial Communities and Ecosystem
Ecological hierarchy of microorganisms:
Ecosystem
↑
Community
↑
Guild
↑
Population
↑
Individual
Guild: Populations that use the same resources are called guild
...
Guilds are defined
according to their locations, attributes or activities of their component species
...

Community: It is the highest biological unit in an ecological hierarchy made up of individual and populations
...

Habitat: Populations within a community interact with each other in an integrated manner
...

Population: A population consists of individuals of the same species that live, interact and migrate through the same
niche and habitat
...

Criteria of population:
1
...

3
...


The organisms are of the same kind
...

The population is the structural component of an ecosystem which develops and maintains itself by
reproduction i
...
, it is a self-regulating system
...


Niche: The functional role of an organism within an ecosystem; the combined description of the physical habitat,
functional role and interactions of the microorganisms occurring at a given location is called niche
...

Population selection within communities:
•
•

r strategies
k strategies

r = rate of increase in population
k = carrying capacity of the environment

2

r strategies
Characteristics:
1
...

3
...

5
...


Dominates in resourceful environment
Occurs at low population density / uncrowded condition
High reproduction rate
Unstable environment where change is unpredictable
Subject to extreme fluctuations
When resources scarce, population crash (i
...
rapid reduction in growth rate)
...


Example: Saccharomyces, Pseudomonas, Archeae, Aspergillus, Bacillus etc
...

2
...

4
...

6
...

Differences between r and k strategies:

5
...


r strategies
Dominates in resourceful environment
...

High reproduction rate
...

Subject to extreme fluctuations
...


7
...


7
...

9
...

Example:
Saccharomyces,
Pseudomonas,
Archeae, Aspergillus, Bacillus etc
...

9
...

2
...

4
...

2
...

4
...

6
...

Occurs at high population density
...

Relatively stable environment where change is
predictable
...

Normally resources do not scarce and
population also do not crash
...

Have physiological adaptations
...


Succession within microbial communities
Succession: It is the process of orderly, sequential change in the species structure in a community over time
...

Primary succession: Colonization of a virgin habitat is called primary succession
...
All pioneer organisms must be able to reach the virgin environment, so a common feature of pioneer
microorganisms is effective dispersal mechanisms
...

Example: The gastrointestinal tract of newborn animals
...
It is the consequence of some catastrophic event that has disrupted and altered the course
of primary succession
...
They may
extend the regions of pioneers or replace them
...

Autotrophic succession: When gross production (P) exceeds the rate of community respiration (R), organic matter
accumulates
...

Autotrophic succession occurs in cases where

𝑃
𝑅

is initially greater than 1
...
As the
occurring
...

Properties:
1
...

3
...


An autotrophic succession of microorganisms occurs in environments largely devoid of organic matter when
there is a non-limiting supply of solar energy
...

In autotrophic succession within a mineral environment, such as on bare rock, the photosynthetic pioneer
organisms have minimal nutritional requirements and high tolerance to adverse environmental conditions
...
Terrestrial cyanobacteria
and lichens are good examples of pioneers in this type of environment
...
Succession in such a situation is called heterotrophic succession
...

Characteristics:
1
...

3
...

5
...

Heterotrophic succession is usually temporary, because it culminates in the extinction in the community when
the stored energy supply is exhausted
...
For example, the microbial communities on a fallen log disappear after the log is completely
decomposed
...
e
...

Pioneers in a heterotrophic succession need to have above all, high metabolic and growth rates in order to stay
ahead of secondary invaders
...


2
...

4
...

𝑃
Autotrophic succession occurs in cases where
𝑅
> 1
...

It is usually not temporary
...

2
...

4
...

Heterotrophic succession occurs in cases where
𝑃
< 1
...

It is usually temporary
...

6
...


The energy flow through the system does not
decrease with time
...

Example: Terrestrial cyanobacteria, Lichens
...

6
...


The energy flow through the system decreases
with time
...

Example: Gut community is an example of
heterotrophic succession
...


Sterilized natural detritus particles are placed in seawater or freshwater inoculated with a small amount of
natural detritus
↓
Bacterial occur in small numbers on the particles after 6 – 8 hours and reach their maximal numbers after 15 –
150 hours
...

↓
Small zoofalgellates appear about 20 hours after inoculation and reach maximal population sizes after 100 –
200 hours and reach maximal numbers at 200 – 300 hours
...

↓environmental factors
Decomposition of some of the nitrogen poor plant polymers and their partial replacement with nitrogen-rich
microbial biomass
...


Nitrifying bacterial populations decrease in forest ecosystem in climax community resulting in accumulation
of ammonium
↓
Ammonium leaches less from soil that favors the growth of plants and non-nitrifying bacteria
...


Gastrointestinal tract is first colonized by Bifidobacterium and Lactobacillus
↓
This favours growth of facultative anaerobes such as E
...

↓
Bacterial adherence and colonization (monolayer)
↓
Continue growth to produce thick layer
↓
New bacteria invade to establish a community with multiple populations
↓
Some bacteria produce exopolysaccharide that provides interface between cell and the environment, facilitates
microniches and influence the susceptibility of bacteria to stress
↓
Eukaryotic microbes such as algae and protozoa, amoeba, flagellates, ciliates, diatoms then invade the biofilm
...

Homeostasis and secondary succession

5

Homeostasis: It is a compensating mechanism that acts to maintain steady state conditions, by a variety of control
mechanisms to counteract perturbations that would upset this steady state
...

2
...


Accumulation of nitrite or H2S in the ecosystem leads to the increase in population that use nitrite or H2S
...

A metabolic niche filled by mesophiles in summer may be occupied by psychrophilic population in winter,
which leads to the concept of thermal niche
...
This leads to algal bloom formation
...

↓
As the ice melts, the habitat is removed, ending community succession
...

↓
During the winter, pigmented bacterial populations also disappear from the surface waters, but some algal and
pigmented bacterial populations survive in the sediment
...

With the return of sufficient sunlight in the spring, algae colonize under the ice and the process repeats itself
...
This leads to initiate new succession, called secondary succession
...

2
...

Restore initial community when alien microbes enter, such as when alien microbes enter the gastrointestinal
tract on food
...
Example: Antibiotic
resistance
...
There are 3 types of conjugation
...
F+ conjugation
2
...
Hfr (high frequency recombination) conjugation
...

Transduction: Bacteriophage mediated DNA transfer is called transduction
...


In hypersaline ‘evaporite flats’ (mat like structure) of tropical seashores:
• Cyanobacteria, Nostoc, Anabaena, Oscillatoria, Spirulina are the primary producers in oxygenic
upper level
...

Photosynthetic product is converted to H2S by sulfate reducers
...

Cyanobacteria has filaments with exopolysaccharide sheath which serves the following functions:
6

2
...

Give the cohesion to the mat
...

Prevent disintegration
...

Prevent drying out during low-tide
...
They excrete mucopolysaccharide sheath for trichomes
...
This film protects the mat and stabilizes the sand
...
Associated with the mats are filamentous cyanobacteria, some can fix
nitrogen
...


7

Effect of Abiotic Factors on Microorganisms
Two theories or principles:
1
...
Shelford’s law of tolerance
Leibig’s law of the minimum: Justus Leibig recognized that like atoms in a molecule, elements in a living organism
are present in distinct proportions
...

Significance: In any given ecosystem, there will be some limiting nutritional factor
...
Leibig’s law of the
minimum applies to microorganisms just as it applies to plants and animals
...

In given ecosystem, the growth of one microbial population may be limited by concentrations of available phosphorus,
and adding nitrogen will not permit additional growth of that population
...


Shelford’s law of tolerance: The occurrence and abundance of organisms in an environment are determined not only
by nutrients but also by various physiocochemical factors such as temperature, redox potential, pH and many others
...

It states that for survival and growth each organism requires a complex set of conditions
...

In essence, Shelford’s law says that there are bounds for environmental factors above and below which microorganisms
cannot grow and survive
...
Consequently, psychrophilic
microorganisms cannot grow in ecosystems with high temperature; obligately halophilic microbes cannot grow in
freshwater lakes; and so forth
...

Differences between autecology and synecology:
Autecology
1
...

2
...

3
...


Synecology
1
...

2
...

3
...
It can even be the study of an
ecosystem
...
Synecology is complex, philosophical and deductive
...
Autecology is comparatively simple, experimental and
inductive
...
Autecology studies can be accommodated in a
laboratory setup and data is interpreted using
conventional mathematical tool
...
Synecology studies refer to the interaction of a whole
system and that cannot be accommodated in a laboratory
setup as the system is naturally formed after interactions
of hundreds of years such as a forest ecosystem
...
Example: Study of sterile grassland ecosystem
(including all the species of communities)
...
Example: Study of Zebra population in relation to its
environment (may be factors like rainfall, hunting, lion
population etc
...

8

Some important considerations in examining tolerance factors:
•

•
•

The tolerance range found in the lab in autecological studies is typically broader than that actually exists in
nature because synecological interactions (competition, predation, parasitism are absent in the autecological
studies
...

Most studies record the average condition but fail to consider the microhabitats
...

o Population interaction can alter the environment in such a way that allow other microbes’ growth,
such as nitrogen fixation and prevent other microbes’ growth such as acid secretion
...
e
...

Example:
1
...

3
...

Water or any nutrient may bound and become unavailable for microbial uptake which prevents growth
...

• Nitrogen gas cannot be used
...

• Iron in oxidized form (Fe3+) is insoluble and unavailable
...


Some prefixes:
Eury: Have wide tolerance range
...

Steno: Have narrow tolerance range
...

Some microbes grow optimally at extreme environment such as salt pond, hot spring, desert soil
...
In less severe condition, nutrient and population interaction do the selection in population establishment
in a community
...
They are•
•
•
•
•
•
•
•
•
•
•
•
•

Temperature
Radiation
Pressure
Salinity
Water activity
Movement
Diffusion
Adsorption and surface tension
Hydrogen ion concentration
Redox potential
Magnetic force
Organic compounds
Inorganic compounds

Temperature

9

Optimum growth temperature: Temperature at which microbes exhibit their highest growth rate and reproduction
rate is called optimum growth temperature
...

Minimum growth temperature: Temperature below which microbes are metabolically inactive is called minimum
growth temperature
...

Classification of microbes according to their tolerance to various temperature:
•

•
•
•

Psychrophiles: They grow at temperatures <0-<200 C
...
These organisms can be killed at room
temperature or by brief warming e
...
, Vibrio, Pseudomonas, Bacillus psychrophiles etc
...

Thermophiles: They grow at temperatures 40-<800 C
...
Some hyperthermophiles have been reported with
growth temperature optima at 1050 C and no growth below 850 C
...

2
...


To maintain the integrity and fluidity of cell membrane
...

Low temperature freezes or gels the cell membrane, shuts down protein synthesis in mesophile, resulting in
interruption of vital function
...
In psychrophiles, high proportion of unsaturated fatty acids and/or short chain length lipid keeps the membrane
flexible at low temperature
...
In thermophiles1
...

2
...

3
...

4
...

5
...

6
...
In some Archaea, ether bond and branching of the hydrocarbon chain raises
the heat resistance of the cell membrane
...

Hyperthermophiles are mainly Archaea, Sulfolobus, Desulfolobus, Pyrococcus, Staphylothermus
...

Natural habitat for thermophiles: Volcanic salfatara, submarine thermal vent, hot springs
...

Plants, animals excluded over 500 C
...

10

•

Cyanobacteria excluded above 900 C
...

Optimum: 800 C – 1100 C
...
Endospore,
cyst, sclerotia of fungi and other resting stages occur in unfavourable temperature
...
This is the basis for refrigeration or freezing in
food industry
...
This is the basis for –
a
...


Reservation of food products but main concern is spoilage and disease
...


Effect of temperature on microbial activity: High temperature in general leads to –
1
...


3
...

Higher enzymatic activity
...

• Less contamination problem
• Source of heat resistant enzymes protease and lipase used in detergent industry
...

Slower generation time because they need to perform a large amount of repair mechanism (for example,
replacing denatured enzyme), so less advantageous for producing single cell protein or antibiotic
...

Radiation: Radiation is the emission or transmission of energy in the form of waves or particles through space or
through a material medium
...

Ionizing radiation: Radiations are designated as ionizing radiations if their interactions with matter produces unstable
ions and free radicals that interact with living matter in a destructive manner e
...
, γ rays and X rays
...

2
...

High level exposure causes extensive DNA fragmentation and destroy the nucleic acid and enzymes
...


Main challenges:
•
•
•

Ionizing radiations are highly penetrating
...

High level exposure causes extensive DNA fragmentation and destroy the nucleic acid and enzymes
...


Adaptive mechanisms:
•

Bacterial endospores are highly resistant to gamma radiation; it takes
...
4 million rads (Mrads) to effect a 90%
kill, whereas one tenth of this dose effects the same percentage kill in most vegetative bacteria
...


Non-ionizing radiation: Ultraviolet light basically causes non-ionizing radiation
...
The wavelength of UV radiation is 100-380 nm, but the most
germicidal wavelength is 260 nm, which is also the absorption maximum of DNA
...


Adaptation mechanism:
•

•

Slow repair: UV-damaged DNA can be repaired enzymatically by excision of the damaged portions, but this
process requires time
...

High visible light: Visible light has a reactivation effect on UV-damaged cells
...
In addition, visible light triggers a
DNA repair mechanism that is, paradoxically, not triggered by the more damaging UV radiation
...


Visible light radiation:
Wavelength: 320 nm (violet)- 800 nm (red)
Quality of light in a habitat depends on•
•
•

Obstructions
Absorption
Scattering

together called extinction

Extinction is high in ecosystem with suspended particles
...

2
...


Intensity of light influences the photosynthetic rate
...

Some microbes show phototactic behavior, by moving towards or away from a light source
...

Light also affects circadian rhythms in some eukaryotic microbes
...

Note: Circadian rhythm: Noting or pertaining to rhythmic biological cycles recurring at approximately 24-hour
intervals
...

Pressure
Pressure is of three types:
1
...


Atmospheric pressure
Hydrostatic pressure and

12

3
...


Atmospheric pressure: Atmospheric pressure is the pressure exerted by the weight of the air column, which
at the surface of the earth (sea level) is approximately 1 atmosphere (atm; 760 mmHg, or 101
...

In general, changes in atmospheric pressure do not affect microorganisms
...


2
...
A 10m
water column over a 1 cm2 area weighs 1 kg and exerts about 1 atm pressure
...
That means, atmospheric pressure at sea level is 1 atm and
the pressure at 10m is approximately 2 atm
...
Higher hydrostatic pressure inhibits the growth of terrestrial and shallow water
organisms
...
Growth rate declines as pressure increases
...

• Barotolerant: They tolerate elevated pressure up to certain limits without a decline in growth
...
Bacteria retrieved from a depth greater than 6000 m are predominantly barophilic
...
Most barophiles grow in
darkness, very UV sensitive and lack many mechanisms of DNA repair
...


High hydrostatic pressure damage:
1
...

3
...

Inhibits membrane transport function
...


Adaptation mechanism:
Barophilic microbes might have the proper tertiary enzyme structure only at high pressure and would not function well
at low pressure
...

3
...
In biological
systems, the solvent is typically water
...
Osmotic pressure results from the differences in
solute concentrations on opposite sides of a semipermeable membrane
...

A cell’s surrounding environment can be of three types:
Env
Hypotonic: Lower solute concentration than inside the cell
...


0
0 0

0

0

0

0

0

0

0
0

Isotonic: Equal solute concentration of cell and the surrounding
environment
...


cell

Hypotonic habitat: Includes freshwater, rainwater, distilled water
...
Majority
of microbes can withstand hypotonic habitat
...

Adaptive mechanism:
1
...


Rigid cell wall of bacteria and other microbes pushes back excess water
...

Contractile vacuoles of some protozoa pump out excess water
...
Hypertonic habitat: Includes honey, nectar, sugar syrup
...
Fewer microbes can
withstand hypertonic habitat
...
So cells dehydrate and shrivel
...

1
...


The osmotic pressure of concentrated sugar solutions tends to dehydrate microbial cells
...
These are low molecular weight organics such as glycerol, various sugars, glumate, glycine betaine
and similar compounds
...

The enzymes of osmotolerant and osmophilic microorganisms are capable of functioning in the presence of
high solute concentrations of the environment i
...
, low solute concentrations of the cell
...
Their enzymes function suboptimally at low solute concentrations
(of the cell) resulting in optimal growth at water activities below 0
...


14

3
...


Classification of microbes living in hypertonic habitat:
•
•

Osmotolerant: They tolerate high concentration of solute (usually sugar)
...

Osmophile: They prefer high concentration of solute (usually sugar)
...


These may cause spoilage of food preserves, syrups
...

Halotolerant: They tolerate high salt concentration
...

Challenges faced by non-halotolerant:
1
...


Cells dehydrate in hypertonic salt environment
...


Adaptation mechanisms:
1
...

3
...


Exclude high and toxic Na+
...

The obligate halophile, Halobacterium achieves osmotic balance with high intracellular potassium chloride
(KCl)
...

Some have bacteriorhodopsin bilayer cell membrane, which pumps out H+ in exchange of K+/Na+
...

Water is vital for growth and survival
...
Water activity can be decreased not only by solutes (osmotic forces) but also by absorption to solid
surfaces (matric forces)
...
0
...
Most microorganisms require aw values above 0
...
60
...

Xerotolerant: Xerotolerant means tolerant of dry condition
...
They exhibit
greater tolerance to desiccation
...

Challenges faced by non-xerotolerant microbes:
1
...

3
...

Fragment nucleic acid
...


Adaptation mechanisms to survive in low water activity environment:
1
...

3
...

Synthesis of non-reducing sugars trehalose and sucrose
...
Thus denaturation of protein is prevented
...

15

4
...
They tend to be in moisture equilibrium with
the surrounding environment
...

• Rock matrix: The uppermost 1 – 3 mm of rock is microbe – free, next few mm is colonized by
microbes, known as endolithic microbes
...
In hot deserts, the only endolithic microbes are cyanobacteria
...

In cold deserts, polar endolithic communities include lichen, fungi and algae association, but are
found as segregated bands within rock matrix (normal lichens are integrated, thalliod)
...
Endolithic lichen
activity results in the mobilization of iron compounds in the rock and exfoliative weathering pattern,
causing a general erosion of the rock over geologic time periods
...

One study shows their turnover time around 20,000 years
...
Of equal importance is the role of
movement in importing and distributing nutrients for microbial growth and in removing metabolic by – products
...

Some ecosystems are characterized by extensive flow, such as in rivers, or by turbulence, such as in oceans
...
Ecosystems with extensive flow or turbulence
have greater mixing capacity
...
Even in quiescent and static systems, thermal convection, evapotranspiration and leaching move
materials
...
Diffusion results in a spreading out of a
substance from its source, lowering concentration
...
The molecular weight of the solute and the viscosity (flow characteristics) of the solvent determine in part
the ability of a solution to diffuse through an ecosystem
...
Gaseous molecules with low specific gravities, for example tend to rise,
generally moving upward through aquatic ecosystems
...

The movement of gases along thermal gradients results in turbulence and mixing
...
Porosity refers to the number and volume of
pores in a soil or sediment particle matrix
...
Diffusion of materials occur through the pores, and exchange rates between material in interstitial
spaces and external sources affect diffusion rates and the availability of materials essential for microbial growth and
activity
...
Adsorption may bind materials to particles, decreasing availability
...

2
...

If the substance is an essential nutrient, this can decrease productivity
...

In some cases, adsorption is essential for microbial reproduction
...

Mechanism of adsorption:
1
...

3
...

In some cases, proteins known as lectins mediate attachment
...


Hydrogen ion concentration
Microbes generally cannot tolerate extreme pH, because pH affect directly and indirectly
...

Indirect effect of pH:
pH influences –
•
•
•

The solubility of CO2, influencing the rate of photosynthesis
...

The mobility of heavy metals, such as copper, which is toxic to microbes
...
Some microbes are acidophilic and some are
alkaliphilic
...

2
...

Cell components are hydrolyzed
...

Acidotolerant and acidophiles:
Most fungi are acidotolerant, most bacteria are not, except Lactobacillus, which is used in preparation of silage and
fermentation of foods
...

Habitat: Hot, acido coal refuse piles
...
00 but prefer neutral pH
...

Habitat: Saline lakes with high pH
...
So they are
used in detergents to remove fat and protein based stains
...
Some microbes are active only in oxidizing environment, others are active only in reducing
environment
...
Facultative anaerobes can operate over a wide range of Eh values
...
At high Eh, iron and manganese exist in their trivalent and tetravalent
form respectively
...
At low Eh, these metals exist in bivalent
form, that are soluble and readily available
...
So in those places Eh is usually negative
...
Some bacteria, however, exhibit magnetotaxis, motility directed by a
geomagnetic field
...
Magnetotactic bacteria contain dense inclusion bodies, which may impart a magnetic moment upon the cell
...
The magnetic iron is the form of either
magnetite (Fe3O4) or greigite (Fe3S4)
...
These allow
cells to orient themselves in magnetic fields and actively move by flagellar motion toward one of the magnetic poles
...

Experimentation on a pure culture of magnetotactic bacterium Aquaspirrilium magnetotacticum revealed that even in a
pure culture some bacteria are attracted to the north and others to the south magnetic pole
...
However, the ecological value of
magnetotactic orientation for microorganisms, if any, remains to be determined
...
In aquatic ecosystems,
the chemical oxygen demand (COD) is often used to indirectly measure the amount of organic compounds in water
...

Classification of microbes:
1
...


Copiotrophs: Bacteria growing on high nutrient concentrations, such as sewage lagoons
...
High nutrient concentration is inhibitory microbes
...

2
...

They are usually small spheres, slender rods or envelope – appendaged bacteria that have high surface area for
uptake of nutrients
...
These are gliding
Gram negative bacteria growing on rotting plant materials or animal waste
...

↓
Binary fission ceases
...

↓
Myxospores are formed within it
...
It is capable of surviving prolonged periods of starvation
...

Organic compounds as inhibitors:
Some metabolic products are toxic to microbial populations when they accumulate
...
Some microbes excrete allelopathic substances which affect growth, health, behavior or population
dynamics of other species
...

Inorganic compounds:
Many are essential as nutrients, many are toxic and inhibitors of microbial growth
...
Heavy metals: Some heavy metals are required in trace amounts as nutrients, but can become strongly
inhibitory to microbes at very low concentrations
...

• Low pH of the environment mobilizes them
...

2
...

4
...

Impermeability to or reduced transport across cell membrane
...

Synthesis of special metal – binding compounds such as metallothioneins
...


Habitat: Seawater, industrial pollution of water bodies
...
Oxygen and its reactive forms: Molecular O2 is essential for aerobes but inhibitory to anaerobes
...

Toxic forms of O2 and their mechanism of toxicity:
1
...

More toxic
ii
...

iii
...

iv
...

2
...

In the upper atmosphere, O* is formed photochemically and reacts with O2 to produce O3
...

It is a strong oxidizing agent killing microbes
...

Sometimes used as a sterilizing agent in some water treatment process
...
Superoxide anion (O2- )
Characteristics:
i
...

ii
...

4
...

Adaptation to toxic forms of O2 or reactive oxygen species (ROS): Various enzymes convert ROS into less
toxic forms
...

b
...


O2 H 2 O2
H 2 O2

𝑠𝑢𝑝𝑒𝑟𝑜𝑥𝑖𝑑𝑒 𝑑𝑖𝑠𝑚𝑢𝑡𝑎𝑠𝑒 (𝑆𝑂𝐷)

→

𝑐𝑎𝑡𝑎𝑙𝑎𝑠𝑒

→

𝑝𝑒𝑟𝑜𝑥𝑖𝑑𝑎𝑠𝑒

→

H 2 O 2 + O2

H 2 O + O2
H2O

Bacterial enzymes that protect the cell from ROS:
Microorganism
Aerobe
Facultative anaerobe
Microaerophile
Obligate anaerobe

Catalase
+
+
-

Superoxide dismutase
+
+
+
-

5
...

CO2 is required for autotrophic and heterotrophic metabolism
...

CO strongly inhibits microbial respiration pathway by blocking electron transport
...
Nitrogen
Only nitrogen fixing bacteria are able to convert gaseous nitrogen into combined forms of nitrogen such as
ammonium, nitrate and nitrite
...

7
...
High
concentration of phosphate is inhibitory
...

9
...

11
...
SO2 and H2S are toxic
...

Chloride: Chloride is needed for maintenance of membrane function
...

Silicon: Diatoms, silicoflagellates and radiolaria require silicone for building cell wall structures
...


2
...


4
...


When collecting soil samples, microbiologists often do not use aseptic technique but pragmatically rely on a
shovel and pail because of the abundance of microorganisms in the soil relative to possible contaminants from
air or nonsterile containers
...
The soil corer, a hand- or motordriven hollow tube with a sharp cutting edge, is used with or without a liner to hold the core of collected soil
...

The Cholodny-Rossi buried sample technique has been used extensively in the sampling and observation
enumeration of microorganisms in soils and sediments
...
Assuming that the clean glass slide surface is nonselective and acts like the surface of
mineral particles in soil, the types and proportions of the organisms that adhere to the slide can be considered
representative of the soil community in general
...

Observation of the retrieved grids with the electron microscope reveals more microbial morphological detail
than light microscopy can
...


Water samples
Various methods have been used to collect water samples and analyze the microbial populations in them
...

1
...

3
...


5
...


Nansen and VanDorn sampling bottles: Water samples collected for enumeration of algae and/or protozoa
are often collected with Nansen and VanDorn sampling bottles, but these devices are not suitable for
bacteriological sampling because they cannot be sterilized
...

The planktonic organisms may be funneled into collection bottles, where they are concentrated
...
After the device is lowered to the desired depth, a weighted messenger is sent down the
line to break the glass inlet tube, allowing the water to enter the flask or bulb
...
The sampling bag is mounted on a spring-loaded holder and lowered to the desired depth
...

Specialized sampling devices are also required for collecting water samples from great depths because of
decompression problems during recovery; devices have been designed to open at a specific depth, allow a
sample to enter, and close again in order to maintain the appropriate pressure during recovery
...
Grab samplers: For collecting sediment samples from marine or fresh water ecosystems, a variety of grab
samplers are used
...

2
...
It recovers sediment in a relatively undisturbed state
...
Core samplers: Core samplers are used to prevent compression of the sample so that the vertical stratification
of the microbial community can be preserved
...
Divers and submersibles can be used for remote sampling
...
Membrane filter: Air samples are most often collected by forcing a measured volume of air through a
collection device called membrane filter
...

2
...

Biological samples:
1
...

3
...


Retrieving microorganisms from plants and animals involves collecting a vital fluid such as sap or blood;
dissecting to recover a particular tissue, such as liver; collecting excreted products, such as fecal matter; or
sampling a surface tissue
...

Microorganisms can be recovered from plant surfaces by washing with sterile solutions, from the oral cavity
by scraping and washing tooth surfaces, and from human skin by swabbing
...

In some other cases, the tissue or cells may be preserved together with the associated microorganisms
...
Such approaches are useful when considering associations between microbial populations, such as
between phage and bacteria, as well as when examining associations between plants or animals and
microbiota
...
They may require concentration, dilution or enrichment
...

1
...
Example: Membrane filtration
method
...


Dilution: This technique is applicable when the number of microbes is too high
...


3
...
g
...


23

Non – Cultural microorganisms
It is likely that fewer than 1% of bacteria can be cultured in the laboratory using conventional culturing techniques
...
They may require some factors that was in the environment
but not provided in the laboratory
...
Methods and
techniques have been developed to detect these microorganisms in the environment
...
Lipid profile analyses
2
...

1
...


Plating procedures: The classical approaches for detecting microorganisms are to place viable microbial cells
onto a solid medium
...
The plate is then incubated under conditions
that fever the growth of those microbes so that their phenotypes can be observed
...


1
...
The lipid composition of cytoplasmic membranes of diverse microorganisms vary
...
By examining the profiles of lipids, microbial species can be identified
...

2
...
The full process of
FAME analysis consists of the esterification of lipids and the injection, separation, identification and
quantitation of fatty acid methyl esters by gas chromatography
...
Fatty acid methyl esters are identified by comparisons of
their retention times with those of individual purified standards or well-characterized lipids that have been
previously described
...

Molecular detection: The greatest advances in microbial ecology in the last few years have come from the application
of molecular methods to the detection of microorganisms in environmental samples
...
Many of these methods rely on amplification of molecular signature sequences and their detection by
hybridization techniques, especially using oligonucleotide probes
...
The phylogenetic relationships of bacteria, archaea
and eukaryotic microorganisms can also be determined using gene probes and molecular analyses, giving rise to new
perspectives on the natural microbial world
...

2
...

4
...


Nucleic acid recovery
Gene probe detection
Amplification of DNA- The Polymerase Chain Reaction (PCR)
Genetic fingerprinting
Receptor genes

They are discussed below:
1
...
This usually
involves extensive purification to remove proteins, humic aids and other compounds that would interfere with
analysis of the nucleic acids
...
Two approaches have been used to recover DNA and RNA from environmental
samples; isolation of microbial cells followed by cell lysis and nucleic acid purification (cell extraction) and
direct lysis of microbial cells in the environmental matrix followed by nucleic acid purification (direct
extraction)
...

2
...
With the use of gene probes, specific microbial populations can be detected in environmental samples
...
Hybridization of the gene probe is diagnostic of the
presence of a specific microbial population
...

3
...
It
permits the in vitro replication of defined sequences of DNA
...
By exponentially amplifying a target sequence, PCR
significantly changes the probability of detecting rare sequences in heterologous mixtures of DNA
...
Genetic fingerprinting: The interrelationships of microbial strains from various habitats can be studied by
analyzing their DNA to reveal a ‘genetic fingerprint’
...
Such analyses of genes for ribosomal RNAs
are used to determine phylogenetic relationships
...
Lunge et al
...

5
...
A genetic marker is a genetic element that permits the detection of an unrelated biological
function
...
They can detect microbial activities in natural samples even

25

when there are complex interactions among microbial populations
...


Determination of microbial numbers

Techniques of determination of microbial numbers:
Direct count procedures:
•
•

Microscopic count methods
Particle count methods

Viable count procedures:
•
•
•

Plate count and related methods: Selective and Differential viable culture methods
Colony hybridization
Most probable number

They are discussed below:
Direct count procedures:
•

Microscopic count methods: Microorganisms can be counted by direct microscopic observations
...
There are, however, several major drawbacks to direct observational methods,
including the inability to distinguish living from dead microorganisms, the underestimation of microorganisms
in samples containing high amounts of background debris, and the inability to perform further studies on the
observed microorganisms
...
A variety of counting chambers that hold specified volumes, such as
a hemocytometer or Petroff-Hauser chamber, can be used for counting cells
...
The Coulter counter electronically measures the number of particles within a fixed
size range
...
The
problem with Coulter counter analysis is that small nonliving particles are counter together with
microorganisms, which has limited the method’s usefulness
...


Viable count procedures: There are two basic approaches to viable count procedures1
...

3
...
All viable count
procedures are selective for certain microorganisms; the degree of selectivity varies with the particular viable count
procedure
...
The problems lie in the misuse of the method and the interpretation
of the result
...


26

1
...
Agar is most often used as
the solidifying agent because most bacteria lack the enzymes necessary for depolymerizing agar
...
Surface spread method: In this method, dilutions of samples are spread on the top of the agar
...
Pour plate method: In this method, the sample suspension is mixed with the agar just before the plates
are poured
...
Roll tube method: It is used for enumeration of obligate anaerobes, is an extension of the pour plate
method
...
It is assumed that each
colony originated from a single bacterial cell
...
Tubes with too many colonies cannot be counted accurately
because one colony may represent more than one original bacterium
...

5
...
These media are both selective and differential
...
They differentiate bacteria capable
of utilizing lactose by formation of characteristically colored colonies
...
Estimates of coliform counts determined in this manner are often used as an indicator
of water quality and for quality control in the food industry
...

Colony hybridization: Colony hybridization is an application of nucleic acid hybridization that is combined
with conventional environmental microbiological sampling and viable plating procedures
...
The colonies or phage containing plaques are then lysed by alkaline or enzymatic
treatment, after which hybridization is conducted
...
Growth on the isolation medium increases the number of copies of the target gene to a level
detectable by a gene probe
...
Measurement of
biomass is used to determine the standing crop of a population and the transfer of energy between trophic levels within
an ecosystem
...
Unfortunately, the direct measurements of microbial biomass, such as by filtration
and dry weight or by centrifugation and packed cell volume measurements as practiced or pure cultures, are rarely
applicable to environmental samples
...
Consequently, the determination of microbial biomass is often imprecise
...


2
...
Ideally, all the microbial biomass to be
determined should have the same quantity of the biochemical being assayed, so that there is a direct correlation
between the amount of the biochemical measured and the biomass of microorganisms
...
These two conditions are rarely, if ever,
met, so the results of quantifying a particular biochemical must be extrapolated with caution in order to
estimate the biomass of microorganisms that are present
...
A
factor of 250 – 286 is often used for conversion of ATP to cellular carbon for aquatic samples
...

2
...

4
...

6
...
g
...


28

Microbiology of Potable Water
Potable water: Water that is free of disease producing microorganisms and chemical substances harmful to health is
called potable water
...

Non-potable or contaminated water: Water that is contaminated with domestic or industrial wastes is called nonpotable or polluted water
...

2
...


Physical examination
Chemical examination and
Microbiological examination

They are discussed below:
1
...


3
...

Microbiological examination: Water can be contaminated with harmful microbes through –
i
...

Illegal or leaky sanitary sewer connection
iii
...

Floodwaters and surface runoff

Presence of pathogens is determined indirectly by testing for indicator organisms
...
This kind of pollution
means that any pathogenic microorganism that occur in the intestinal tract of these animals is or may be present in the
water
...
g
...
or environment
e
...
, swimming pool
...
coli is an indicator microorganism
...
coli) is the major species in the fecal coliform group
...
coli is generally not found growing and reproducing in the environment
...
coli is considered to be the species of coliform bacteria that is the best indicator of fecal pollution and
the possible presence of pathogens
...

2
...

4
...


It is present in polluted water and absent from unpolluted (potable) water
...

The quantity of indicator organism correlates with the amount of pollution
...

It has uniform and stable properties
...

7
...


It is generally harmless to humans and other animals
...

It is easily detected by standard laboratory techniques
...

2
...
As a result, they
could be missed in sample submitted to the laboratory
...


Number of indicator bacteria commonly found in human feces:
•
•
•
•
•
•

Indicator organisms
Bacteroides spp
...

Clostridium perfringens
Coliforms
Fecal
Non-fecal
Fecal streptococci

Cells per gram of feces (wet weight)
107 – 1011
107 – 1011
103 – 1010
106 – 109
107 – 109
105 – 108

Classification of indicator organism:
Major:
1
...


Coliforms: 2 groups- Total coliform (TC) and Fecal coliform (FC)
...
Coliform as indicator organism:
There are two principle group of coliform bacteria:
Total coliform
By definition, the total coliform (TC) group comprises all
aerobic and facultative anaerobic, Gram negative, nonspore forming, rod shaped bacteria that ferments lactose
and forms acid within 48 hours at 350 C
...

Ferment lactose with the production of acid and gas
within 24-48 hours at 350 C
...
50 C
...

Exclusively fecal in origin
...
5±0
...


Standard value of TC and FC in drinking water recommended by various authorities
•
•

0 – 10 total coliform cfu/100 ml of drinking water
<1 fecal coliform cfu/100 ml of drinking water

30

•

•

Total coliforms can be used as indicator organisms for monitoring the efficacy of water treatment and
disinfection process
...

Total coliform can also be used as a reasonable indication of the presence of pathogenic bacteria
...
They also
respond to the environment, water and wastewater treatments similarly to many pathogens
...
Fecal Streptococci as Indicator Organism
They are Gram positive cocci, occurring in short chains and are mostly found in the intestines of man and
other warm blooded animals
...

ii
...

iv
...

Presence in wastewaters and known polluted waters
...

Persistence without multiplication in the environment
...
liquefacines occur in both polluted and unpolluted environments and are
indistinguishable from true fecal Streptococci
...

The ratio of FC to FS has been proposed as an indicator if the origin of the fecal contamination (human vs
animal)
...
7 suggests animal (wild and
domestic) fecal pollution
...
Clostridium perfringens as indicator organism
It is a Gram positive, anaerobic, spore forming rod shaped bacterium
...
Because it is spore forming organism, it can be used as
an indicator of occasional or intermittent pollution or of previous pollution of water
...

ii
...

Type A Clostridium perfringens from human feces may also grow in the soil
...
Pseudomonas aeruginosa as an indicator organism
31

It is a Gram negative, aerobic, non-spore forming rod shaped bacterium
...
g
...
It is found in small number in the
feces of healthy people and it is resistant to chemical disinfection
...


5
...
Staphylococcus
aureus might be used as an indicator of water quality to address skin infections rather than gastrointestinal
infections because –
•
•

It shows resistance to marine and chlorinated swimming pool waters
...


Other proposed fecal indicators:
•
•
•

Bifidobacterium
Bacteroides spp
...
g
...


Bacteriological examination of water for potability
Steps to be followed when a water sample is submitted for bacteriological examination:
1
...

3
...

5
...

The sample must be representative of the supply from which it is taken
...

The sample should be tested as promptly as possible after collection
...


The routine bacteriological procedure consists of –
1
...


A standard plate count to determine the number of bacteria present
Tests to reveal the presence of fecal indicator bacteria
...
The most probable number method (MPN)
b
...


Standard plate count: It reflects the load of general aerobic bacteria in the water system
...
Plate counts
are also useful in determining the efficiency of operations for removing or destroying microorganisms e
...

sedimentation, filtration and chlorination
...
Tests to reveal the presence of coliform bacteria:
Most probable number method (MPN)
MPN analysis is a statistical method
...

The method is based on the fact that the greater the number of bacteria, the more dilution is needed to reduce
the density to the point at which no bacteria are left to grow in the tubes in a dilution series
...
The pattern of (+) and (–) scores are then interpreted with appropriate
statistical table to obtain the MPN of microorganisms per volume of sample
...
Presumptive test
2
...
Completed test
They are discussed below:
1
...

3
...
If the presumptive test is negative, no further testing is performed and the water source is
considered microbiologically safe
...

Confirmed test: Some microorganisms other than coliforms also produce acid and gas from lactose
fermentation
...

Completed test: Since some of the positive results from the confirmatory test may be false, it is
desirable to do completed tests
...


Types of analysis
Total coliforms (incubated at 350C)
Fecal coliforms (incubated at 44
...
20C
Fecal streptococci (incubated at 350C)

Medium
Lactose or lauryl tryptose broth
EC medium
Azide dextrose broth

Positive reaction
Gas and/or acid
Gas and/or acid
Growth

Advantages:
i
...

ii
...

iii
...


34

iv
...


Sample toxins are diluted
It is an effective method of analyzing several samples such as sediments, sludge, mud, etc
...

ii
...

iv
...


2
...


It quantifies numbers of bacteria by filtering water, growing bacteria and counting; all organisms that
produce a dark colony (generally purplish green) with a metallic sheen within 24 hours at 350C of
incubation on M-endo medium
...

It is used for testing water that are supposedly not contaminated e
...
tap water, raw water (it can
identify a specific indicator)
...
Known volume of water is filtered through a filter (0
...

2
...

3
...

4
...
coli
• Red colonies indicate other total coliform bacteria
• E
...

Types of analysis
Total coliform (incubated at 350C)
Fecal coliform (incubated at 44
...
20C)
Fecal streptococci (incubated at 350C)

Medium
m Endo agar
m FC
m Enterococcus

Advantages:
1
...


Larger volume of sample can be processed
...


Disadvantages:
1
...


35

Positive reaction
Colonies with metallic green sheen
Pale to deep blue colonies
Pink to deep red colonies

Sewage treatment
Sewage: Sewage or wastewater includes all the water from a household that is used for washing and toilet waste
...
Sewage is mostly water and little
particulate matter, only 0
...

Sewage treatment: Sewage treatment is the process of removing contaminants from wastewater to produce
environmentally safe treated wastewater
...

Purpose of sewage treatment: The purpose of sewage treatment is to reduce –
1
...

3
...


Suspended solids
Biodegradable organic compounds (specifically BOD)
Pathogens
Nutrients, such as nitrates and phosphates

Stages in a typical sewage treatment:
Principally four stages:
1
...

3
...

5
...


Primary sewage treatment: It is a mechanical process
...

• Settling chamber:
a
...
) are screened out by bar screen
...
Grit chamber removes sand, grit, stones, broken glass etc
...
Floating debris is shredded and ground
...
Skimmers remove floating oil and grease
...
After that sewage treatment proceeds through sedimentation tank, where it is held for several
hours to allow more suspended particles to settle out
...

b
...

c
...

d
...
Some digestion of sludge and dissolved organic matter
occur during holding time
...

e
...

2
...

It is predominantly biological
...

Removes most of the dissolved organic matter and reduces BOD
...

Sewage undergoes strong aeration to encourage growth of aerobic bacteria and other microbes that
oxidize dissolved organic matter to CO2 and H2O (mineralization)
...

a
...

o Effluent from primary treatment is aerated in a large aeration tank
...
g
...

Protozoa, small animals, filamentous bacteria and fungi are attached to the flocks
...
During this time, a part of the organic
matter is mineralized and another part is converted into microbial biomass
...

Some flock materials or activated sludge are used as incubation for the next batch (hence the
name of the process) and the rest is sent to the sludge digester
...


Advantages:
i
...

ii
...

iii
...

iv
...

v
...
coli,
Enteroviruses etc
...

ii
...

Operation is troublesome
...
Trickling filters:
• It is a common method
...

• The bed is designed in such a way that air can circulate throughout the bed
...
As a result, BOD
reduces
...

Advantages:
i
...

iii
...

Removes 80 – 85% BOD
...


Disadvantages:
i
...

iii
...


Less effective than activated sludge system
...

Make nuisance to nearby residence
...


Combination of primary and secondary treatments reduce original BOD of sewage by 80 – 90%
...


Disinfection and release: Treated sewage is disinfected usually by chlorination, before being discharged
...

4
...
An anaerobic sludge digester is designed to encourage the growth of anaerobic bacteria especially
methane producing bacteria that degrade these organic solids to soluble substances and gases
mostly CH4 (60 – 70%) and CO2 (20 – 30%)
...


The digester contains high amounts of suspended organic matter
...

c
...

d
...
g
...
Reactions are usually heated at 35 – 370 C for optimal performance
...
Control is necessary for pH to stay within 6
...
0 with pH 7
...

Stages: Essentially 3 stages:
a
...

b
...

c
...
Acetic acid is also split to methane and
CO2 by methanogens
...

ii
...

Sludge contains soil – conditioning materials e
...
humans and mulch and can be used as a
fertilizer
...


i
...

ii
...

Tertiary sewage treatment: It is additional treatment beyond secondary sewage treatment
...

• The effluent from secondary treatment contains impurities, such as some residual BOD, 50% of the
original nitrogen and 70% of the original phosphorous
...


Process:
a
...

b
...

c
...
Some system encourages denitrifying
bacteria to form nitrogen gas
...
Finally, the purified water is chlorinated
...


ii
...
So additional
treatment might necessary
...


Advantage: Produces water that is almost suitable for drinking
...

Some other systems of sewage treatment:
1
...


Oxidation pond or Lagoon
Rotating biological contractor

They are discussed below:
38

1
...
Oxygen is supplied from the air but release of O 2 during photosynthesis by alga Chlorella provides
additional source of O2
...

Inexpensive to build and operate
...

Have a large holding capacity
...

ii
...


2
...

Creates odor problem
...


Rotating biological contractor (RBC): It is aerobic secondary sewage treatment process
...

Characteristics:
i
...

ii
...

iii
...

iv
...

v
...

Advantages:
i
...

iii
...

It is efficient and stable in operation
...


Disadvantages:
i
...


39

Short Notes
BOD
Biochemical Oxygen Demand or Biological Oxygen Demand (BOD) is the amount of dissolved O 2 needed by aerobic microbes
to break down organic matter in water
...
To simply put, the higher
the BOD, the higher the organic pollution in a sample
...

Unit of measurement: mg/L of O2 consumed in 5 days at a constant temperature of 200 C in the dark
...
But this O2 is also needed by fish and other
organisms in the lake
...

Methods:
•
•

Method 1: This is the most common method
...

Method 2: This method involves the incubation of a water sample that is diluted with de-ionized water saturated with
O2
...
e
...


These tests represent standard laboratory procedures usually referred to as the BOD 5 test
...
Succession may be
of primary and secondary
...

Biofilm development starts when a solid surface is immersed in an aqueous environment and organic molecules absorb,
forming a macromolecular conditioning film
...

↓
Form complex biofilm community which is highly resistant to outside disturbances
...

Septic tank
A septic tank is a chamber made of concrete, fiberglass, PVC or plastic through which domestic wastewater (sewage) flows for
primary treatment
...
They break down waste, leaving water clean enough to safely percolate down
into the earth
...
Some live in the tank, but most do their work
in the drain field
...


All waste flows to the septic tank
...


Watery waste, called effluent, fills most of the tank
...

3
...
Sludge is composed of inorganic solids and the byproducts of bacterial digestion
...
A layer of scum floats to the top
...

5
...
Greases and oils float to the top
...

6
...

7
...

8
...

9
...

10
...

11
...

12
...

Maintenance: The following items should never be flushed down the drain or toilet:
•
•
•
•
•
•
•
•
•
•
•
•

Food waste
Fat, oil and grease
Plastic bags
Nappies
Sanitary towels, including tampons, applicators and wrappers
Cotton buds
Condoms
Bandages and plasters
Baby wipes
Medicines, needles and syringes
Cleaning wipes
Razor blades

These items will block the inlet and outlet pipes, and also disrupt the biological separation process taking place within the tank
itself
...

2
...

4
...


Simple and robust technology
...

Low operating costs
...

Small land area is required
...

2
...


Low reduction in pathogens, solids and organics
...

Effluent and sludge require further treatment and/or appropriate discharge
...

2
...


Bacteria
Virus
Parasites

They are discussed below;
1
...

•
Shigella: These highly contagious bacteria can dwell in lakes, ponds and beaches and cause a huge amount
of illnesses every year
...


3
...

Legionella: These bacteria infect the airways, not the gut and can be transmitted by the warm, steamy air of
hot tubs
...
Waterborne outbreaks are
documented by rotavirus
...

•
Norovirus: The virus can spread via contact with the fecal matter of infected people, which can contaminate
surfaces, food and water
...

Parasites:
•
Cryptosporidium: This diarrhea inducing parasite is often transmitted via swimming pools and water
playgrounds
...

o
Entry is through nose
...


Water supply and sanitation in Bangladesh
Water supply is the provision of water usually via a system of pumps and pipes
...

Water supply and sanitation in Bangladesh is characterized by a number of achievements and challenges
...

In 2004, 98% population have access to an improved water source, a very high level for a low income country
...
However, in 1993, it was discovered that
groundwater, the source of drinking water for 97% of the rural population and a significant share of the urban population, is in
many cases naturally contaminated with arsenic
...

Maximum permissible arsenic limit for Bangladesh is 0
...
01% mg/L

Microbial communities in nature
Examples:
3
...

•
Below is purple anoxigenic phototrophic bacteria and underneath black layer of sulfate reducers
...
H2S is used by purple sulfur bacteria
...


iv
...

v
...

vi
...

In the South Western US, ‘Desert crust’ is composed of cyanobacterial mats, where they are the primary producers
...
In dry weather, it forms a brittle film over desert sand
...
In moist weather, trichomes slide out, spread and secrete new sheath
material
...
This ‘desert crust’ sterilizes
the desert sand and pave the way for the succession of lichen and moss
...

Challenges faced by non-xerotolerant microbes:
4
...

6
...

Fragment nucleic acid
...


Adaptation mechanisms to survive in low water activity environment:
5
...

7
...


Undergoes dormant stage such as production of spores
...
Upon desiccation these sugars form a non-crystalline glass
or gum phase, that is hydrogen bonded to the protein
...

Production of gelatinous exopolysaccharide in the form of sheath, capsule and slime as desiccation protectant
...
They tend to be in moisture equilibrium with the surrounding
environment
...

•
Rock matrix: The uppermost 1 – 3 mm of rock is microbe – free, next few mm is colonized by microbes,
known as endolithic microbes
...
In hot deserts, the only endolithic microbes are cyanobacteria
...

In cold deserts, polar endolithic communities include lichen, fungi and algae association, but are found as
segregated bands within rock matrix (normal lichens are integrated, thalliod)
...
Endolithic lichen activity results in the
mobilization of iron compounds in the rock and exfoliative weathering pattern, causing a general erosion of
the rock over geologic time periods
...
One study shows their turnover time
around 20,000 years
...
g
...

Damages caused by ionizing radiation:
3
...


Low level radiation causes mutation
...
As a result, the
microbes are killed
...

Low level radiation causes mutation
...
As a result, the
microbes are killed
...
3-
...


43

•

Highly efficient DNA repair mechanisms of some bacteria make them extremely radiation resistant like Deinococcus
radiodurans
...

5
...


Higher metabolic activity, such as increased O2 consumption
...

These two are advantageous in –
•
Composting
•
Depolymerization, fermentation, methanogenesis
...

•
Source of amylase and cellulase in food, fermentation and textile industry
...


Adaptation of hyperthermophiles
Hyperthermophiles: They grow at temperatures 80-1000 C
...

Example: Hyperthermophiles are mainly Archaea, Sulfolobus, Desulfolobus, Pyrococcus, Staphylothermus
...

Main challenges of tolerating extreme temperature:
4
...


To maintain the integrity and fluidity of cell membrane
...


Adaptation mechanisms:
7
...

8
...

9
...

10
...

11
...

12
...
In some Archaea, ether bond and branching of the hydrocarbon chain raises the
heat resistance of the cell membrane
...


Health impacts of inadequate sanitation and importance of sanitation
The World Health Organization defines the term "sanitation" as follows:
Sanitation generally refers to the provision of facilities and services for the safe disposal of human urine and feces
...


44

Inadequate sanitation is the lack of improved facilities (toilets, conveyance and treatment systems) and hygiene practices (for
example, hand washing, proper water handling, personal hygiene and so on) that exposes people to human excreta and thus
to disease causing fecal – oral pathogens through different transmission pathways
...

2
...

4
...

6
...

Poor sanitation is linked to transmission of diseases such as cholera, diarrhea and dysentery
...

Leads to malnutrition and stunting especially in small children
...

Has a major impact on the quality of life of people with AIDS and the quality of life of those around them
...

2
...

4
...

6
...

8
...

To reduce the severity and impact of malnutrition
...

To promote school attendance: Girls’ school attendance is particularly boosted by the provision of separate sanitary
facilities
...

To reduce water treatment costs
...

To strength tourism
...
What is thermal death time (TDT)?
Thermal death time (TDT): Thermal death time is how long it takes to kill a specific bacterium at a specific temperature
...
g
...


Why safe water is essential and what is its importance
Safe water is essential because –
1
...

3
...


Without safe drinking water humans cannot survive and eventually die of diseases
...

Many of the 10 million child deaths a year due to unsafe water and lack of sanitation
...


Importance of safe water:
1
...

3
...

5
...

7
...

Our brain is made up of 95% water and blood 82%
...

Water helps remove dangerous toxins from our body
...

Water helps regulate our body temperature
...


45



---