bacteria1 chapter 5 classification of bacteria is ‘murky’ a “muddle in the middle” few...

Bacteria 1

Bacteria Chapter 5

Classification of bacteria is ‘murky’

A “Muddle in the Middle”Few distinctive characteristicsGenetically promiscuous

Traditional classification:anatomical featuresstaining characteristicsmetabolic properties

Newer approach

Genetic analysis

Bergey’s manual is the ‘Bible’

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Classification based upon anatomical features

3 common shapes

Some unusual shapes also:

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Classification based upon anatomical features

Other unusual bacteria

Spirochetes

Cell wall-less

Stalked

Filamentous

Myxobacteria fruiting bodies Streptomyces

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Classification based upon staining

Gram Positive vs Gram Negative

Hans Christian Gram -- 1884-- Crystal violet

Gram positive structure-- thick layer of peptidoglycan

Gram negative structure-- inner vs outer membranes-- lipopolysaccharides and endotoxins

Acid fast staining-- Mycobacterium

Penicillin action

Effect of penicillin

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Classification based upon metabolism -- will explore further later

Heterotrophic

AutotrophicPhotosynthetic bacteria

-- cyanobacteria -- purple sulfur bacteria

Chemoautotrophic

‘Metabolically defective’

Rickettsia

Chlamydia

Rocky Mountain Rocky Mountain Spotted fever wood tick R. rickettsii

Image from (and good source for more about Chlamydia)http://www.chlamydiae.com/docs/biology/biol_devcycle.asp

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Why are bacteria so small?Size affects ‘surface to volume’ ratio

Advantages of large S/V:diffusion ratesmetabolic ratesreproductive rates

Limits to size reduction?‘defective’ bacteria

Really big bacteria?-- Epulopiscium fishelsoni

Epulopiscium web sitehttp://www.micro.cornell.edu/cals/micro/research/labs/angert-lab/epulopiscium.cfm

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Why study Bacterial Cell Structure?Mechanisms of virulence

Drug development

Identification

Some cell exterior structurescell membrane (lipid bilayer)

cell wall (Gram-pos vs Gram-neg)

glycocalyx (capsule vs slime layer)

flagellum (prokaryotic vs eukaryotic)

pilus (adhesion vs sex)

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Cell Membrane Structure

Phospholipid bilayers

Membrane proteins

Membrane fluidity

Membranes ofthermophilic archaebacteria

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Bacterial Flagella

Prokaryotic vs eukaryotic

Arrangementsmonotrichous

lopho-

amphi-

peri-

How do we know movementis rotational?

Bacterial Flagella

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How do flagellatedbacteria move?

‘Run and Tumble’ patternChromatium motility

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Spirochetes -- very strange structure-- e.g., Borrelia, Treponema

Axial filaments

Outer sheath

Motility

Borrelia Movement

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Fimbriae and Pili

Fimbriae adhesion to surfaces

Pili (pilus)genetic recombination

other functions?

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The glycocalyx

Functionsadherencevirulenceprevent desiccation

Composition

Capsule layersvs

Slime layers“xantham gum”(Xanthomonas)

Strep Pneumo

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Endospores

Formation and regrowth

Special properties?-- desiccated-- DNA binding proteins-- Ca-dipicolinic acid

Magnetotactic bacteria-- possess magnetosomes

Endospore formation

Magnetotactic Bacteria