answer from the powerpoint

Chapter 2

Microbes

Public Health 4030

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8/30/2017 Ch. 02 - Microbes 2

https://www.ksl.com/?sid=45604010&nid=148&title=ecoli-detected-in-areas-at-utah-lake

• Weber County Dairy – Campylobacter infection – Diarrhea, cramping, abdominal pain, fever, bloody

diarrhea – most people recover after 10 days – Infections often associated with unpasteurized

dairy products, contaminated water, poultry, and produce • Infection in cow udder or milk is contaminated with

manure 8/30/2017 Ch. 02 - Microbes 3

Some Basic Biological Principles

• Cell first coined by Robert Hooke in 1665

• Cell Theory (Schleiden, Schwann and Virchow)

– The cell is the fundamental unit of all organisms.

– All organisms are unicellular or multicellular.

– All cells are fundamentally alike in structure and

metabolism.

• Spontaneous generation was eventually displaced

by the notion that “life begets life”

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What Makes a Microbe?

• Microbe is a term of convenience—microscopic size

and unicellularity are not absolute characteristics of

microbes like fungi (some bacteria are macroscopic).

Figure 02.04A: Levels of biological organization.

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Even multicellular microbes lack the organization found

in the tissues of plants and animals.

Figure 02.04B: Multicellular levels of cellular organization.

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1) Size

BIGGER 8/30/2017 7

1) Size

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2) Metabolic Diversity

• Cells obtain energy through metabolism, capturing it in

the high-energy bonds in ATP, adenosine triphosphate.

– Heterotrophs must metabolize complex organic molecules

(food) as a source of energy and carbon.

– Autotrophs do not use organic molecules as an energy source

and can use an inorganic source of carbon (CO2).

• Photosynthetic autotrophs obtain energy directly from the

sun.

– Such microbes produce most of our oxygen (O2)

• Chemosynthetic autotrophs obtain their energy from

inorganic compounds.

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Heterotrophs depend

upon autotrophs for

the organic

molecules they

metabolize for their

energy needs.

Figure 02.01: A pathway map showing heterotroph dependency on autotrophs and the autotrophs’ energy sources.

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• Microbes have diverse requirements for O2.

– Aerobes require O2 for metabolism.

– Anaerobes do not use O2 for metabolism. Some can

tolerate O2 but others are killed by it.

– Facultative anaerobes grow better in the presence of

O2, but they can grow in its absence.

Bacteria suspected of being

anaerobes must be transported

and cultured under anaerobic

conditions (GasPak).

2) Requirement for Oxygen

Figure 02.02: Culturing anaerobic bacteria.

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no internal compartments

(bound by membranes)

3) Prokaryote vs. Eukaryote

membrane-bound compartments

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Microbial Evolution and Diversity

• Bacteria were the first life-forms on Earth

– Discovered fossilized bacteria in stromatolites (3.5 byo)

– Early atmosphere devoid of oxygen

– Photosynthetic microbes evolved to use sunlight, water, and

carbon dioxide to produce oxygen and carbohydrates (2 byo)

• Taxonomy (science of classifying living species)

– Linnaeus (1700s) classified all organisms as plant or animal

– Haeckel (1866) had 3-kingdoms: animals, plants, and Protists

– Whittaker (1969) proposed 5-kingdom system

– Woese, et al. (1990), 3-domains; Bacteria, Archaea, and

Eucarya, based on comparisons of rRNA sequences

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Whittaker’s five-kingdom classification system.

Figure 02.06: Whittaker’s five-kingdom system.

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Woese’s three-domain classification system.

Figure 02.07: Woese’s three-domain system.

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Prions

• Prions (like mad cow disease, scrapie, etc.)

– Acellular

– Infectious protein particles

– No genome (lack DNA or RNA)

– Submicroscopic

– Reproduce in a unique way—an

infectious prion protein physically

interacts with a normal protein,

converting it to the infectious form

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Viruses

• Viruses (like HIV/AIDS, measles, rabies, etc.)

– Acellular

– Genome RNA or DNA

– Obligate intracellular parasite (needs living cell to replicate)

– Submicroscopic (need electron microscope to see them)

Figure 02.12: TEM of Variola viruses.

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Bacteria • Bacteria (like Escherichia coli, etc.)

– Unicellular

– Procaryotes

– Microscopic (with few exceptions)

– DNA genome, replicate by binary fission (asexual)

– Cell wall (except mycoplasmas)

– Some motile by one or more flagella

– Metabolism, heterotrophs and autotrophs

– Important human pathogens, most beneficial or harmless

Figure 02.13: Lactobacillus bacteria.

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Protozoans • Protozoans (like malaria,

leishmaniasis, etc.)

– Unicellular

– Eucaryotic

– Microscopic

– DNA genome, asexual or sexual replication

– No cell wall

– Some motile by flagella, cilia or pseudopods

– Metabolism, heterotrophs

– Important human pathogens, most are harmless

Figure 02.14: Giardia lamblia protozoan.

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Algae

• Algae (like dinoflagellates, diatoms, etc.)

– Unicellular or multicellular

– Eucaryotic

– Microscopic (unicellular only)

– DNA genome, asexual replication

– Cell wall

– Metabolism, photoautotrophs

– Not infectious, some produce

neurotoxin harmful to marine life or

humans who eat toxin-containing fish

or shellfish (red tide bloom)

Figure 02.15: Freshwater diatoms.

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Fungi • Fungi (yeast or molds, etc.)

– Unicellular (yeast) or multicellular (molds)

– Eucaryotic

– Microscopic (yeast only)

– DNA genome, asexual or sexual replication

– Cell wall

– Non-motile

– Metabolism, heterotrophs

– Usually harmless or even beneficial, but a relative few are pathogenic for humans

Figure 02.16: Two mushrooms growing on a stump.

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Relatively few microbes cause infectious

diseases.

(much less than 0.1%)

Most are beneficial to our

health and survival.

(See Chapter 3, Krasner & Shors (not required reading)

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• Exploited to produce foods.

• Used to make products (drugs, chemicals, biotechnology) and energy sources (biofuels).

• Used for bioremediation to clean-up environmental pollutants.

Microbes are beneficial to society

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