Bacterial Cell Structures

What does binary fission require?

ATP

What are the 4 stages of binary fission

Parent cell, DNA replication, Cytoplasm divides, Two daughter cells

What does the doubling time/generation time refer to?

the time required for the amount in a colony to double

What are the advantages of binary fission?

-Widely dispersed populations can still reproduce
-Cells are identical to their parents and should survive well if conditions don't change

-Rapid reproduction

What are the disadvantages of binary fission

-Cells are identical to parents and so are vulnerable to the same environmental stresses
-Unchanging cells may be slow to take advantage of new energy and nutrition sources

How many bacteria are in a cm² of a human?

10^8 bacteria/cm 2

What is pathogenesis

the mechanism/s a microbe uses to cause a disease state

What is virulence

The relative ability for a microbe to cause disease

What is infection?

refers to the replication of a pathogen in or on its host

What is disease

occurs when specific signs/symptoms are associated with infection

What are virulence factors?

Cell surface or secreted factors which give them a survival advantage in the host

What are primary pathogens?

tend to produce disease readily in healthy hosts

What are opportunistic pathogens?

generally only cause disease when they gain entry to an unusual site or when the host has a weakened immune system (immunocompromised)

What is a carrier?

Infected but not diseased

What is the bacterial capsule?

An outer layer of polysaccharides that covers the cell wall of many different bacterial species

What is the function of the bacterial capsule

• protect bacteria from toxic compounds and desiccation

• allow bacteria to adhere to surfaces

• help bacteria escape the immune system of the host

What is chemotaxis

rapid movement of bacterial cells
towards more desirable environments or
away from those less desirable

What are the 3 working parts of a flagellum

• the basal body working as a rotary motor
• the filament as a screw propeller
• the hook as a universal joint connecting the
filament to the motor

What’s positive chemotaxis?

toward a higher concentration of a chemical stimulus.

What’s negative chemotaxis

away from a higher concentration of a chemical stimulus

What are bacterial fimbriae?

Short, hair-like protein structures on the surface of bacteria that help them attach to surfaces or host cells

What are adhesins

The hair like proteins that sit at the end of fimbriae

What’s an epithelial cell?

forms the protective layers covering body surfaces and lining internal organs and cavities.

What is the role of adhesin molecules

allow bacteria to adhere to host cells by docking, like a lock and key

What is the bacterial endospore?

a highly resistant cell to preserve
the cell's genetic material in times of extreme stress

Which two bacterial genera produce endospores?

Bacillus and Clostridium

What does the endospore consist of?

genome, cytoplasm, specialised coating

What are cytotoxins, neurotoxins, enterotoxins and super antigens?

exotoxins

What are cytotoxins?

cause cell lysis/bursting

What are neuerotoxins?

affect neurotransmitter release

What are enterotoxins?

cause electrolyte imbalance in the gut

What are superantigens?

cause an excessive immune response

Whats an example of cytotoxins

– Gas gangrene caused by Clostridium perfringens.
– The bacterial infection produces toxins that release gas and cause tissue death

What’s an example of neuerotoxins

Tetanus, botulism caused by Clostridium species

Whats an example of a disease casued by enterotoxins?

Food poisoning, diarrhoea

Whats an example of a disease caused by superantigens?

Toxic shock

How does botox work?

A protein exotoxin that actively interferes with nerve signalling

Why is LPA a virulence factor?

elicits an inflamtory response

Where is LPA found?

In the cell wall of gram negative bacteria

How does the capsule hide the c3b markers?

acts as a physical barrier

What does a c3b marker do?

a complement protein

causes cell destruction

How are fimbria bacterial infections treated?

release molecules that mimic the surface structures the bacteria would bind to

similar to agglutination

How do endotoxins differ from exotoxins

endotoxins are lipid A within the cell wall

exotoxins are produced and secreted

What do Clostridial exotoxins do (tetanus)

-Continual release of acetylcholine
-Increasing stiffness of the muscles due to spasms

What do Botulism toxins do

• Blocks release of acetylcholine (responsible for muscle contractions)
• Causes flaccid paralysis

Why do some bacteria not cause disease?

Irrelevant virulence factors

Immune system keeps quantity appropriate

Not infectious in the body part they are colonising

What is the bacterial capsule

an outer layer of polysaccharides

Where does the bacterial capsule cover

the cell wall

Which receptors on the cell membrane tag for phagocytosis?

C3b

How do flagella move in order to achieve a straight line?

unidirectionally

What is on the end of fibrae?

adhesins

How do adhesins work

via lock and key mechanism with epithelial cells

What two genus procure endospores?

Bacillus and Clostridium

Can exotoxins travel?

Yes, to far away from the site of infection

What is responsible for muscle contraction?

Acetylcholine

What disease does Clostridium tetani cause?

tetanus

What disease does Clostridium botulinum cause

botulisim

What is the mechanism of tetanus disease

continual release of acetylcholine

What is the mechanism of botulism disease

blocks release of acetylcholine

How does botox work?

blocks release of acetylcholine via neurotoxins