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Introduction to Microbiology

5/23/16 3:27 PM

Microoganisms – single-celled microscopic organisms + viruses
• Independent entities that carry out life processes independently of
other cells, unlike plants and animal cells (require multicellular
structures)
• Support all other forms of life, serve as good models for scientific
discovery
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2 – Microbial Cells
• cell – dynamic and fundamental unit of life
o cell wall – structural strength
o membrane – defines cell compartment, prevents leakage,
maintains correct amounts of materials (selectively
permeable)
o communicate, move, exchange materials
• Properties of Cellular life
o Metabolism – uptake of nutrients from their environment,
transformation of these materials into new materials/wastes;
these transformations produce energy that can be used to
fuel other cellular processes, form new structures

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Cells
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§ The final metabolic goal of any cell is to make 2 cells
Growth – increase in cell number from cell division
Evolution – process of descent with change in which genetic
variants are chosen based on reproductive fitness
§ Slow process but can occur quickly in microbes
ú i
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antibiotic resistance
§ overarching theme in bio
motility – the ability to move/propel itself
§ allows escape from bad conditions/danger, find new
resources
differentiation – process by which cells become specialized
for growth, dispersal, or survival
§ may be triggered by chemical signals
communication – ability to send and receive signals
between cells, and perform appropriate activities
yellow = all cells
pink = some
as Biochemical Catalysts and as Genetic Entities
Carry out chemical reactions = catalyst
DNA replication, transcription, translation = genetic coding
devices
§ Enzymes – proteins that perform catalytic machinery
(provide energy and compounds for all cellular
components)
§ Genome – the set of all genes in an organism

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ecosystem - the collection of all living organisms with the physical
and chemical components of their environment
o aquatic = oceans, ponds, lakes, streams, ice, hot springs
o terrestrial = soil, deep subsurface
o other organisms
o Microorganisms excrete waste products into their
environment, and remove nutrients from their environment
§ Metabolic activities may change their ecosystems
ú
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Aerobic bacteria may remove all oxygen from an
environment à anoxic

Microbial ecology – studies interactions between
microorganisms, animals, plants, and the global
ecosystem

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6 billion years old
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6 billion years – Earth was anoxic (no
oxygen present):
ú gases present: carbon dioxide, nitrogen, others

only anaerobic microorganisms could survive
• methanogens – produce methane
§ Within Earth’s first billion years of existence, organisms
that could harvest energy from sunlight evolved
(phototrophs)
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The extent of Microbial Life
o Estimated 2
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5 – The Impact of Microorganisms on Humans
• Microorganisms as Agents of Disease
o Most progress in discovering the causes of infectious diseases
in the beginning of the twentieth century
o Pathogens – microorganisms that cause infectious diseases
§ Children, elderly highly vulnerable
§ 100 years ago, infectious diseases were the most
common causes of death
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ú Better sanitation, health practices
ú Antibiotics
§ Still major threats in developing countries
ú Malaria
ú Diarrhea

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ú Cholera
ú TB
ú Measles
ú African sleeping sickness
ú Pneumonia
ú Ebola
ú Bird/swine flu
§ Bioterrorism
o Most microorganisms pose no threat to human life/are
beneficial
Microorganisms, Digestive processes, and Agriculature
o Microorganisms cycle nutrients, and contribute to agriculture
...
coli
§ Salmonella – infected meat, fruits, veggies
Microorganisms and Food, Energy, and the Environment
o Biofuels are produced by some microorganisms
§ Natural gas = anaerobic degradation by methanogenic
organisms
§ Ethyl alcohol = ethanol = fermentation of glucose

o Microbial bioremediation
§ When microorganisms are used to clean up human
pollution
o Industrial microbiology
§ Commercially valuable products produced
o Biotechnology
§ Genetic engineering…
o Genomics – science of the identification and analysis of
genomes
§ Helps identify genes that code for proteins of interest

Pathways of Discovery in Microbiology

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7 – Pasteur and the Defeat of Spontaneous Generation
• Louis Pasteur was BOSS
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Spontaneous generation
o Spontaneous generation – idea from biblical times, that
food microorganisms could spring forth from nonliving
materials
§ Pasteur hated this idea, and believed that
microorganisms were involved in putrefying materials
§ Sterile – food/media protected from further
contamination
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Experiment
ú Nonsterile liquid media in flask, neck sterilized
with heat
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8 – Koch, Infectious Disease, and Pure Culture Microbiology
• The Germ Theory of Disease and Koch’s Postulates
o Robert Koch
§ German physician
§ Experiments
ú Cause of disease
• Small amount of blood from diseased mouse
injected into healthy mouse
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9 – The Rise of Microbial Diversity

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Martinus Beijerinck and the Enrichment Culture
o Enrichment culture technique – developed my professor
and Dutch botanist; method in which microorganisms were
isolated from natural samples using nutrients and incubation
conditions
o Isolated many soil and aquatic microorgnaisms
§ Tobacco mosaic disease – concept of a virus
§ Sulfate-reducing, sulfur oxidizing bacteria = bacterial
metabolic groups
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Sergei Winogradsky, Chemolithotrophy, and Nitrogren Fixation
o Chemolithotrophy – concept in which inorganic compounds
(without carbon) are oxidized to yield energy
§ These obtained carbon from carbon dioxide
§ Autotrophs
§ First isolated nitrogen fixing bacterium
ú Clostridium pasteurianum

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