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Chapter 3:

Microscopy and

Cell Structure

http://www.siue.edu/~cbwilso/250graphics00.htmhttp://www.siue.edu/~cbwilso/250graphics00.htmhttp://www.siue.edu/~cbwilso/250graphics00.htmhttp://www.siue.edu/~cbwilso/250graphics00.htm

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Important Point:

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Typical Bacterial Shapes

Also Pleomorphic Bacteria, which vary in their shape(e.g., Corynebacterium).

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Typical Bacterial Arrangements

streptococci

sarcina

staphylococci

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Prokaryotic

Cell Structures

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Typical Prokaryotic Cell

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CytoplasmicMembrane

Movement across membrane for many substances

is controlled by membrane proteins.

Escherichia colihas >200 membrane proteins.

Many of these proteins are involved in transport

across membranes.

Others of these proteins allow a bacterium to sense

its surrounding environments(e.g., as in chemotaxis).

Movement is via:

Simple Diffusion (including osmosis)

Facilitated Diffusion (with concentrationgradient & no energy expended)

Active Transport (against concentration

gradient & energy expended)

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impleD

iffusion--Osm

osis

solute

molecules/ions

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rotein-MediatedTran

sport

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ActiveTra

nsport

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The Prokaryotic Cell Wall

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The Prokaryotic Cell Wall

Determines cellshape.

Prevents osmoticlysis.

In some casesrecognized by host

immune system.

Target for

antibiotics.

Part of cell

envelope.

In Bacteria,composed of

Peptidoglycan.

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Gram-Pos vs. Gram-Neg.

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Gram-Positive Cell Envelope

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Gram-NegativeCellEnv

elope

cell wall

endotoxin

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Gram-Negative Cell Envelope

Periplasm: Site

of preliminary

nutrient

degradation.

LPS: Protection fromantibiotics such as

penicillin plus against

certain toxins.

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Lipopo

lysacch

aride(LPS)

Lipid A =Endotoxin

Carbohydrate has

negative charge and

provides protectionagainst some

antibiotics & some

toxins (e.g.,

detergents).

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MycoplasmalackCellW

alls

Note:

Pleomorphic

Mycoplasma pneumoniae causesWalking Pneumonia

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Glycoc

alyx

Protection (e.g.,

Streptococcus

pneumoniae fromphagocytosis)

Attachment (e.g.,

Streptococcus

mutans causing

dental plaques)

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Ca

psuleS

taining

Capsules are more

regular andgelatinous.

Slime Layers areless regular and

more diffuse.

http://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htmhttp://www.umanitoba.ca/faculties/science/microbiology/wall/210_page/lab%204/lab_4.htm

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Bacteria Flagella (plural)

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Flage

llarArrangeme

nts

also atrichous

e.g.,E. coli

Polar

Flagellum

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Chemo

taxis

Also

Phototaxis,

etc.

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Pili (sing. Pillus)

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Fimbriae (a kind of pilli)

Tips are Adhesins,

used to adhere, e.g.,

to animal tissues

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Closed Circular Chromosome

Also Plasmids, which are

smaller, circular pieces of

DNA.

Plasmids usually

encodeexpendable

functions, e.g.,

antibiotic

resistance.

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Ribosomes: Sites of Translation

On order of 10,000

per cell!

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Endosp

ores

Form inside of

vegetative cells

(hence endo).

Highly resistant toheat, U.V.,

desiccation, etc.

Characteristic of

many soil bacteria,

e.g., Bacillusspp.& Clostridium spp.

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Link to Next Presentation

http://localhost/var/www/apps/Lectures%20post-compression%20except%20Black/nester04.ppt