Typical Prokaryotic CellTypical Prokaryotic Cell

ProkaryoticProkaryoticCell Cell StructuresStructures

Functions of Cell Functions of Cell MembraneMembrane

1. Selective barrier (selectively 1. Selective barrier (selectively permeable)permeable)

2. Secretes exoenzymes2. Secretes exoenzymes amylasesamylases lipaseslipases peptidasespeptidases

Functions of Cell Functions of Cell MembraneMembrane

3. E.T.S. is located here3. E.T.S. is located here 4. Enzymes for cell wall synthesis4. Enzymes for cell wall synthesis 5. If photosynthesis, enzymes are located 5. If photosynthesis, enzymes are located

on membranous structures called on membranous structures called thylakoidsthylakoids

6. Mesosomes - invagination of cell 6. Mesosomes - invagination of cell membrane attached to DNA membrane attached to DNA (Binary (Binary Fission)?Fission)?

Cyt

op

lasm

ic M

emb

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Mem

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Movement across membrane for many substances is controlled by membrane proteins.

Escherichia coli has >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 concentration gradient & no energy expended)

Active Transport (against concentration gradient & energy expended)

Sim

ple

Dif

fusi

on

- O

smo

sis

Sim

ple

Dif

fusi

on

- O

smo

sis

Cyt

op

lasm

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emb

ran

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pla

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Mem

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Pro

tein

-Med

iate

d T

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spo

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edia

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Tra

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Act

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Tra

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Act

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Tra

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The Prokaryotic Cell WallThe Prokaryotic Cell Wall

Determines cell shape.

Prevents osmotic lysis.

In some cases recognized by host immune system.

Target for antibiotics.

Part of cell envelope.

In Bacteria, composed of

Peptidoglycan.

Cell WallCell Wall

Main structural component - Main structural component - PeptidoglycanPeptidoglycan

PeptidoglycanPeptidoglycan repeating dissacharide unitsrepeating dissacharide units polypeptidespolypeptides

Gram-Pos vs. Gram-NegGram-Pos vs. Gram-Neg

Budowa mureinyBudowa mureiny

Budowa mureinyBudowa mureiny

Gram-Positive Cell Gram-Positive Cell EnvelopeEnvelope

Gra

m-N

eg

ati

ve C

ell

Gra

m-N

eg

ati

ve C

ell

En

velo

pe

En

velo

pe

cell wall

endotoxin

Gram-Negative Cell Gram-Negative Cell EnvelopeEnvelope

Periplasm: Site of preliminary

nutrient degradation.

LPS: Protection from antibiotics such as

penicillin plus against certain toxins.

Lip

op

oly

sacch

ari

de

Lip

op

oly

sacch

ari

de

(LP

S)

(LP

S) Lipid A =

Endotoxin

Carbohydrate has negative charge and provides protection

against some antibiotics & some

toxins (e.g., detergents).

Mycoplasma

Mycoplasma lack C

ell

lack C

ell

Walls

Walls

Note: Pleomorphic

Mycoplasma pneumoniae causes “Walking Pneumonia”

Prokaryotic Cell StructureProkaryotic Cell Structure

Glycocalyx - term to describe substances Glycocalyx - term to describe substances that surround bacterial cellsthat surround bacterial cells

1. Capsule1. Capsule if substance is organized and firmly attached if substance is organized and firmly attached

to cell wallto cell wall

2. Slime Layer2. Slime Layer if substance is unorganized and loosely if substance is unorganized and loosely

attached to cell wallattached to cell wall

Function of Capsule

1. Contribute to Virulence of bacteria by preventing phagocytosis by WBC’s

A. Streptococcus pneumoniae

B. Bacillus anthracis

Functions of CapsulesFunctions of Capsules

2. Prevents drying out or dessication2. Prevents drying out or dessication

3. Allows bacteria to adhere to various 3. Allows bacteria to adhere to various surfacessurfaces Streptococcus mutans - Streptococcus mutans - enamel on teeth to enamel on teeth to

cause dental carriescause dental carries Klebseilla pneumoniaeKlebseilla pneumoniae - attaches to - attaches to

respiratory tractrespiratory tract

Gly

cocaly

Gly

cocaly

xxProtection (e.g.,

Streptococcus pneumoniae from

phagocytosis)

Attachment (e.g., Streptococcus

mutans causing dental plaques)

Cap

su

le

Cap

su

le

Sta

inin

gS

tain

ing

Capsules are more regular and gelatinous.

Slime Layers are less regular and

more diffuse.

Fla

gellar

Fla

gellar

Arr

an

gem

en

tsA

rran

gem

en

ts

also “atrichous”

e.g., E. coli

Polar Flagellu

m

Ch

em

ota

xC

hem

ota

xisis

Also Phototaxis,

etc.

Fimbriae (a kind of Fimbriae (a kind of pilli)pilli)

Tips are Adhesins, used to adhere, e.g.,

to animal tissues

MotilityMotility

Almost all Almost all SpiralSpiral bacteria arebacteria are motilemotile

About 1/2 ofAbout 1/2 of BacilliBacilli areare motilemotile

Almost allAlmost all Cocci Cocci are are non-motilenon-motile

Axial Filament - found only in spirochetes (flexible spirals)

Treponema pallidum

FimbriaeFimbriae

Filamentous appendages that are Filamentous appendages that are shorter, straighter and more numerous shorter, straighter and more numerous that flagellathat flagella

found mostly in Gram (-) Bacteriafound mostly in Gram (-) Bacteria

used for attachment not motilityused for attachment not motility

E. coli (pathogenic)

Nuclear area (nucleoid)Nuclear area (nucleoid)

1 circular chromosome (ccDNA)1 circular chromosome (ccDNA) attached to a mesosomeattached to a mesosome

segragation of DNA during Binary Fissionsegragation of DNA during Binary Fission

PlasmidsPlasmids

Small circular, extra-chromosomal pieces Small circular, extra-chromosomal pieces of DNAof DNA

5 to 100 genes 5 to 100 genes Code for auxiliary metabolic functions:Code for auxiliary metabolic functions:

antibiotic resistanceantibiotic resistance penicillasepenicillase

production of toxinsproduction of toxins E. coliE. coli 0157:H7 0157:H7

Ribosomes - Ribosomes - protein protein synthesissynthesis

Prokaryotic RibosomeProkaryotic Ribosome

70 S70 S 50 S50 S 30 S30 S

Eukaryotic Eukaryotic RibosomesRibosomes

80 S80 S 60 S60 S 40 S40 S

Selective ToxicitySelective Toxicity

Some antibiotics are aimed at the 70 S Some antibiotics are aimed at the 70 S ribosomes of bacterial cellsribosomes of bacterial cells

Streptomycin, Neomycin, Erythromycin Streptomycin, Neomycin, Erythromycin and Tetracycline work by inhibiting and Tetracycline work by inhibiting protein synthesis by disrupting the 70 S protein synthesis by disrupting the 70 S ribosomeribosome

Endospores - Endospores - formed under formed under periods of environmental periods of environmental stressstress

Only found in Gram (+) BacteriaOnly found in Gram (+) Bacteria BacillusBacillus

Bacillus cereusBacillus cereus Bacillus anthracisBacillus anthracis

ClostridiumClostridium Clostridium tetaniClostridium tetani Clostridium botulinumClostridium botulinum Clostridium perfringensClostridium perfringens

EndosporesEndospores

Extremely resistant to heat, cold, Extremely resistant to heat, cold, chemicals, lack of water, etc.chemicals, lack of water, etc.

Most vegetative bacterial cells are killed Most vegetative bacterial cells are killed at temps. above 70 C (160 F)at temps. above 70 C (160 F) Endospores can survive boiling water for several hours (some Endospores can survive boiling water for several hours (some

for as long as 20 hours)for as long as 20 hours)

EndosporesEndospores

Spores can remain viable for weeks, Spores can remain viable for weeks, months, yearsmonths, years

Thermoactinomyces vulgarisThermoactinomyces vulgaris spores found in Minnesota were 7,500 spores found in Minnesota were 7,500

years old and still germinatedyears old and still germinated

En

dosp

or

En

dosp

or

es

es

Form inside of vegetative cells (hence “endo”).

Highly resistant to heat, U.V.,

desiccation, etc.

Characteristic of many soil bacteria, e.g., Bacillus spp. & Clostridium spp.