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Bacterial Anatomy and Physiology Lecture Outline for Module 2

1. Interspecies Relationships between bacteria and Host

A. Compatibility of Relationships

i. Environmental Factors

• Physiological Variables

a. Temperature

OptimumGrowth

TemperatureMinimumGrowth

Temperature

MaximumGrowth

Temperature

NoGrowth

NoGrowth

IncreasingStress

IncreasingStress

GrowthRate

Effect of variations in physiological variables. Examples of such variables are Temperature (shown here) but alsopH, osmotic pressures, oxygen concentrations etc etc.

A General Growth Curve

Psychrophiles0°C - 25°C

Mesophiles25°C - 40°C

Thermophiles40°C-104°C

Temperature as a Physiological Variable

GrowthPotential / Rate

0°C 110°C

Microbiology FS – Bacterial Anatomy and Physiology Lecture Outline

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b. Nutrients

• Heamophilus infuenzae

c. pH

• Skin

• Stomach

• Vagina and Urethra are acidic

d. Oxygen requirements

• skin

• colon

pH as a Physiological Variable

GrowthPotential / Rate

1 2 3 4 5 6 7 8 9 10 11 12 13 14

NeutralIncreasing Acidity Increasing Alkalinity

Heavy Growth

Moderate Growth

Poor/No Growth

ObligateAerobes

ObligateAnaerobes

FacultativeAnaerobes

AerotolerantMicro-Aerophilic

Modified from Microbiology, 9th editionby Tortora, Funkd, and ‘’case

Very High Oxygen Concentration

Moderately High Oxygen Concentration

Moderate Oxygen Concentration

Low Oxygen Concentration

Very Low Oxygen Concentration

No Oxygen

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ii. Adhesion

• Mucous Membrane

a. Pili

b. Fimbriae

c. Capsule

iii. Penetration

a. Through skin, and blood

b. Mucous Membrane

B. Quality of Relationships

i. Mutualistic Relationship

a. Escherichia coli – make vitamin D

ii. Commensal Relationship

a. Staphylococcus Epidermidis

iii. Pathogenic Relationship

a. Streptococcus pyogenes

C. Changing the Quality of Relationship

2. Strategies for Reestablishment in new hosts – bacteria need means for transport

between potential hosts.

A. Forming Resistant States of Being – necessary for transient period

between host that may be environmentally hostile

i. Endospores

• i.e. Clostridium botulinum

EnvironmentalStress

Sporulation during

induces Germination

FavorableEnvironmental

Conditions

Endospore

“Vegetative Bacterium”

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ii. Cysts, ie, Giardia lamblia

iii. Elementary bodies, ie, Chlamydia sp.

Favorable EnvironmentalConditions

induce Excystment

Adverse EnvironmentalConditions

induce Encystment

Cyst Trophozoite

ReproductionDuring

EnvironmentallyFavorable Conditions

EB - Elementary Body ( ) (Highly infectious, low-metabolism)

RB - Reticulate Body ( ) (Non-infectious, highly metabolic)

EB

EB - adhesion

EB RB

RB EB

PersistantInfection

Cells of host release infectious EB. Dispersalis by coughing or bodyfluid transfer

New host receivesEB, which attaches to host cell

EB enterscell

EB turns into a RB.RB are not infectious,but may multiply quickly

RB reproduce

RB convert backto EB

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iv. Embryonated eggs (See Parasite Handout)

a. Ex. #1 – Paragonimus westermani (Lung Fluke)

b. Ex. #2 – Taeniarhynchus saginatus (Beef Tape Worm)

B. Employ another organism to make the transfer

i. Vector

a. Arthropods – ticks, mosquitoes, lice, flees, flies etc.

C. Effect Behavior

i. Rabies – virus is in saliva and effects behavior so that the host may

become aggressive and bite, thereby passing on the virus to new

host.

D. Flush bacteria out

i. Gastroenteritis – diarrhea allows for uncontrolled expulsion of

bacteria into environment, drinking water, food etc. Seen with

ecoli strains, colera.

Vector

Reservoir

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E. Take advantage of normal immune response

i. Coughing – common cold

F. Use bait

i. Trichinosis - Parasites form intermediate (larval states) in an

intermediate host, waiting for a host to eat the intermediate host

G. Avoid Host Immune Responses

i. Capsule - resists phagocytosis

ii. Live within host cells – avoidance

iii. Produce Leucocidins that kill white blood cells

As time permits 3. Endospores and their importance in pathogenesis