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’

Bacteria 2

Classification based upon anatomical features

3 common shapes

Some unusual shapes also:

Bacteria 3

Classification based upon anatomical features

Other unusual bacteria

Spirochetes

Cell wall-less

Stalked

Filamentous

Myxobacteria fruiting bodies Streptomyces

Bacteria 4

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

Bacteria 5

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

Bacteria 6

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

Bacteria 7

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)

Bacteria 8

Cell Membrane Structure

Phospholipid bilayers

Membrane proteins

Membrane fluidity

Membranes ofthermophilic archaebacteria

Bacteria 9

Bacterial Flagella

Prokaryotic vs eukaryotic

Arrangementsmonotrichous

lopho-

amphi-

peri-

How do we know movementis rotational?

Bacterial Flagella

Bacteria 10

How do flagellatedbacteria move?

‘Run and Tumble’ patternChromatium motility

Bacteria 11

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

Axial filaments

Outer sheath

Motility

Borrelia Movement

Bacteria 12

Fimbriae and Pili

Fimbriae adhesion to surfaces

Pili (pilus)genetic recombination

other functions?

Bacteria 13

The glycocalyx

Functionsadherencevirulenceprevent desiccation

Composition

Capsule layersvs

Slime layers“xantham gum”(Xanthomonas)

Strep Pneumo

Bacteria 14

Endospores

Formation and regrowth

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

Magnetotactic bacteria-- possess magnetosomes

Endospore formation

Magnetotactic Bacteria