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Microbes in human welfare: Notes
Microbes are present everywhere – in soil, water, air, inside
our bodies and that of other animals and plants
...
Microbes are diverse–protozoa,
bacteria, fungi and microscopic plant viruses, viroids and also
prions that are proteinaceous infectious agents
...
But this should not
make you think that all microbes are harmful; several
microbes are useful to man in diverse ways
...

Micro-organisms such as Lactobacillus and others commonly
called lactic acid bacteria (LAB) grow in milk and convert it to
curd
...
A small amount of curd
added to the fresh milk as inoculum or starter contain
millions of LAB, which at suitable temperatures multiply, thus
converting milk to curd, which also improves its nutritional
quality by increasing vitamin B12
...
Similarly, the dough, which is used for making
bread, is fermented using baker’s yeast (Saccharomyces
cerevisiae)
...
‘Toddy’, a traditional
drink of some parts of southern India is made by fermenting
sap from palms
...
Cheese, is one
of the oldest food items in which microbes were used
...
For example, the large holes in ‘Swiss cheese’
are due to production of a large amount of CO2 by a
bacterium named Propionibacterium sharmanii
...


MICROBES IN INDUSTRIAL PRODUCTS:
Even in industry, microbes are used to synthesise a number of
products valuable to human beings
...
Production on an industrial scale,
requires growing microbes in very large vessels called
fermenters
...
For this purpose the same yeast
Saccharomyces cerevisiae used for bread-making and

commonly called brewer’s yeast, is used for fermenting
malted cereals and fruit juices, to produce ethanol
...

Wine and beer are produced without distillation whereas
whisky, brandy and rum are produced by distillation of the
fermented broth
...
Antibiotics are chemical substances, which are
produced by some microbes and can kill or retard the growth
of other (disease-causing) microbes
...
He found out that it was due to
a chemical produced by the mould and he named it Penicillin
after the mould Penicillium notatum
...
This antibiotic was
extensively used to treat American soldiers wounded in
World War II
...
Antibiotics have
greatly improved our capacity to treat deadly diseases such

as plague, whooping cough, diphtheria and leprosy, which
used to kill millions all over the globe
...

Chemicals, Enzymes and other Bioactive Molecules:
Microbes are also used for commercial and industrial
production of certain chemicals like organic acids, alcohols
and enzymes
...
Yeast
(Saccharomyces cerevisiae) is used for commercial
production of ethanol
...
Lipases are used in detergent formulations and
are helpful in removing oily stains from the laundry
...
This is
because the bottled juices are clarified by the use of
pectinases and proteases
...
Another bioactive molecule,
cyclosporin A, that is used as an immunosuppressive agent in
organ-transplant patients, is produced by the fungus
Trichoderma polysporum
...
It acts by competitively inhibiting
the enzyme responsible for synthesis of cholesterol
...

This municipal waste-water is also called sewage
...
Many of
which are pathogenic
...

Before disposal, hence, sewage is treated in sewage
treatment plants (STPs) to make it less polluting
...
This treatment is carried out
in two stages:
Primary treatment: These treatment steps basically involve
physical removal of particles – large and small – from the
sewage through filtration and sedimentation
...
Then the grit (soil and small pebbles) are
removed by sedimentation
...
The
effluent from the primary settling tank is taken for secondary
treatment
...

This allows vigorous growth of useful aerobic microbes into
flocs (masses of bacteria associated with fungal filaments to
form mesh like structures)
...

This significantly reduces the BOD (biochemical oxygen
demand) of the effluent
...
The sewage
water is treated till the BOD is reduced
...
The greater the BOD
of waste water, more is its polluting potential
...
This sediment is called activated
sludge
...
The
remaining major part of the sludge is pumped into large tanks
called anaerobic sludge digesters
...
During this digestion, bacteria
produce a mixture of gases such as methane, hydrogen
sulphide and carbon dioxide
...


MICROBES AS BIOCONTROL AGENTS:

Biocontrol refers to the use of biological methods for
controlling plant diseases and pests
...
These
chemicals are toxic and extremely harmful, to human beings
and animals alike, and have been polluting our environment
(soil, ground water), fruits, vegetables and crop plants
...

Biological control of pests and diseases: In agriculture, there
is a method of controlling pests that relies on natural
predation rather than introduced chemicals
...
The
more variety a landscape has, the more sustainable it is
...
Contrary to the ‘conventional’ farming practices
which often use chemical methods to kill both useful and
harmful life forms indiscriminately, this is a holistic approach
that seeks to develop an understanding of the webs of
interaction between the myriad of organisms that constitute
the field fauna and flora
...
Thus, the use of biocontrol measures will greatly
reduce our dependence on toxic chemicals and pesticides
...
This will
help develop appropriate means of biocontrol
...
An example of microbial biocontrol
agents that can be introduced in order to control butterfly
caterpillars is the bacteria Bacillus thuringiensis (often written
as Bt)
...
In the gut of the larvae, the toxin is released
and the larvae get killed
...
Because of
the development of methods of genetic engineering in the
last decade or so, the scientists have introduced B
...
Such plants are resistant
to attack by insect pests
...

A biological control being developed for use in the treatment
of plant disease is the fungus Trichoderma
...
They are effective biocontrol agents of several
plant pathogens
...
The majority of baculoviruses
used as biological control agents are in the genus
Nucleopolyhedrovirus
...
They have been shown to have no negative
impacts on plants, mammals, birds, fish or even on nontarget insects
...


MICROBES AS BIOFERTILISERS:
With our present day life styles environmental pollution is a
major cause of concern
...
Of course, we have
now realised that there are problems associated with the
overuse of chemical fertilisers and there is a large pressure to
switch to organic farming – the use of biofertilizers
...
The main sources of biofertilizers are bacteria, fungi
and cyanobacteria
...

These bacteria fix atmospheric nitrogen into organic forms,
which is used by the plant as nutrient
...

Fungi are also known to form symbiotic associations with
plants (mycorrhiza)
...
The fungal symbiont in these associations
absorbs phosphorus from soil and passes it to the plant
...

Cyanobacteria are autotrophic microbes widely distributed in
aquatic and terrestrial environments many of which can fix
atmospheric nitrogen, e
...
, Anabaena, Nostoc, Oscillatoria,
etc
...
Blue green algae also add organic matter to the
soil and increase its fertility
...




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