Microbiology Microbiology is the study of microscopic organisms, referred to as microorganisms (microbes) - a diverse lot!

viruses

Microbiology

All microbes share the common characteristics of relatively rapid growth, ubiquitous distribution and smallness.

Single microbes are not visible to the naked human eye but are sometimes visible as colonies, consisting of groups of millions to billions individual microbes.

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Microorganisms are ubiquitous

Microorganisms are ubiquitous

Microorganisms are ubiquitous

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Microorganisms are ubiquitous

Microorganisms establish associations with other organisms

Bacteria are required for fermentation of sugars in ruminant animals

Bacteria are often associated with plant

roots

Microorganisms established associations with other organisms

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Microorganisms established associations with other organisms

Scleractinian corals contain symbiotic dinoflagellate algae (zooxanthallae) inside their tissues

Microorganisms establish associations with other organisms that may be

Beneficial

Eg. Rhizobacteria associated with soybean plant roots Bacteria fix nitrogen that can then be used by the plant

Microorganisms establish associations with other organisms that may be

Harmful

Cotton diseased seedlings

Cotton Healthy seedlings

The fungal pathogen

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The importance of microbes The Importance of Microorganisms Oldest form of life Largest mass of living material on Earth Carry out major processes for

biogeochemical cycles Can live in places unsuitable for other

organisms Other life forms require microbes to survive

The scope of Microbiology Microbiology covers both basic and

applied sciences:

1. understanding basic life processes of microbes and other organisms (model organisms)

2. application of the basic knowledge for the benefit of humankind and the environment

Microbes as model organisms Some advantages of using microorganisms as

model systems include:

1. Relatively simple organisation

2. Easy to grow, both small and large scale

3. Well-established, relatively simple genetic system

4. Availability of a large number of mutants for genetic studies

5. Relatively easy to manipulative biochemically and genetically

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Microbes as model organisms Escherichia coli (prokaryotic - bacteria, human

intestine)

Saccharomyces cerevisiae (eukaryotic, baker’s yeast)

Applied Microbiology Medical Microbiology e.g. pathology, epidemiology,

immunology Agricultural Microbiology e.g. soil microbiology, plant-

microbe interactions, rumen microbes Food Microbiology e.g. dairy products, baking, brewing,

fermented foods Industrial Microbiology e.g. fermentation, antibiotics,

enzymes, chemicals

Environmental Microbiology e.g. removal of toxic wastes, sewage treatment, water quality

Biotechnology e.g. vaccines (hepatitis B), gene technology (growth hormone, insulin)

Basic concepts in Microbiology Like all organisms, the cell is the fundamental unit of

microbial life. What is the exception?

The Cell: Cytoplasmic (cell) membrane Barrier that separates the inside of the cell from the

outside environment Cell wall Present in most microbes, confers structural strength

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Basic concepts in Microbiology Characteristics of microbial systems Metabolism: chemical transformation of nutrients Reproduction: generation of two cells from one Evolution: genetic changes in cells that are

transferred to offspring Differentiation: synthesis of new substances or

structures that modify the cell (only in some microbes?) Communication: generation of, and response to,

chemical signals (only in some microbes?) Movement: via self-propulsion, many forms in

microbes

Cellular properties

Basic concepts in Microbiology Microbial Growth is the increase in cell number of a

microbial species. Growth requires:

1) supply of energy and precursors by the catalytic machinery for the biosynthesis of all cell component and

2) the entire complement of genes (the genome) to replicates.

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Microbial environments Microbial ecosystems (e.g. marine ecosystem,

terrestrial ecosystem) consist of all of the living organisms together with the physical and chemical components of their environments

Microbial communities consist of various microbial populations

Each population is a group of cells derived from a single parental cell interacting in their immediate environment, called their habitat

Microbial environments

Microbial populations may interact with each other in beneficial, neutral or harmful ways

Environmental conditions (food resources, temperature, pH, oxygen etc) and microbial interactions will determine the diversity and abundance of microbial populations in their habitat

In return, ecosystems are greatly influenced by microbial activities, which change the physical and chemical properties of the habitat.

Life on Earth through the Ages

- Earth is 4.6 billion years old

- First cells appeared between 3.8 and 3.9 billion years ago

- The atmosphere was anoxic until ~2 billion years ago

- Metabolisms were exclusively anaerobic until evolution of oxygen- producing phototrophs

- Life was exclusively microbial until ~1 billion years ago

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Major microbial groups Bacteria, Archaea and Eukarya

The recent phylogenetic tree of life is based on molecular analysis (sequence comparison) of the ribosomal RNA genes of organisms

16S-rRNA for Bacteria & Archaea, 18S-rRNA for Eucarya

The tree shows three domains of organisms: Bacteria, Archaea and Eukarya

Last universal common ancestor (LUCA)

Microbial groups

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Microbial Group Size General characteristics

Bacteria 0.2-2µm Prokaryotic, unicellular, asexual reproduction

Virus 0.015-0.2 µm Obligate parasite, require living cells

Yeast 5-10µm Eukaryotic, unicellular, asexual/sexual reproduction

Fungi 2-10µm by several mm

Eukaryotic, multicellular, asexual/sexual reproduction

Protozoa 2-200µm Eukaryotic, unicellular, asexual/sexual reproduction

Algae 1µm by several cm

Eukaryotic, unicellular/multicellular, photosynthetic, asexual/sexual reproduction

Microorganisms impact on human life

• Microorganisms can be both beneficial and harmful to humans

• Emphasis is typically placed on harmful microorganisms (infectious disease agents, or pathogens)

• Many more microorganisms are beneficial than are harmful

• We will cover examples of both

Microorganisms as disease agents Control of infectious disease during last century

Microorganisms impact on human life

Microorganisms and Agriculture Many aspects of agriculture depend on microbial

activities Positive impacts nitrogen-fixing bacteria cellulose-degrading microbes in the rumen regeneration of nutrients in soil and water

Negative impacts diseases in plants and animals

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Microorganisms impact on human life

Microorganisms and Food Negative impacts Food spoilage by microorganisms requires

specialized preservation of many foods Positive impacts Microbial transformations (typically

fermentations) yield: dairy products (e.g., cheeses, yogurt,

buttermilk) other food products (e.g., sauerkraut,

pickles, leavened breads, beer)

Microorganisms impact on human life

Microorganisms, Energy, and the Environment The role of microbes in biofuels production For example, methane, ethanol, hydrogen

The role of microbes in cleaning up pollutants (bioremediation)

Bugs feed on pollutants

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Microorganisms impact on human life

Microorganisms and Their Genetic Resources Exploitation of microbes for production of

antibiotics, enzymes, and various chemicals Genetic engineering of microbes to generate

products of value to humans, such as insulin (biotechnology)

Microbiology as a Career Clinical medicine Research and development – pharmaceutical,

chemical/biochemical, biotechnology Microbial monitoring in food and beverage

industries, public health, government

The role of the infinitely small in nature is infinitely

large” – Louis Pasteur

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