Introduction to bacteria

What is the theory of spontaneous generation?

life arising from non life

What is a microbe?

How did Louis Pasteur disprove the spontaneous generation theory

The swan neck flask experiment

Who proposed germ theory?

Robert Koch

What are Koch’s postulates

The ‘rules’ of germ theory

• The germ must be present in all affected subjects

• It must be able to be grown in isolation

• Once reintroduced from isolation, the microbe should cause the same disease

• You should be able to re-isolate the microbe

What are the 2 kingdoms of prokaryotes?

Archaea and bacteria

What is the structure of prokaryotic DNA

haploid, circular DNA

How do bacteria asexually reproduce?

binary fission

What are the 2 potential structures in the prokaryotic genome?

circular chromosomes

small circular plasmid (1-5% of chromosome)

How many chromosomes can bacteria have?

1 or 2

What is a theta structure?

What is a cistron?

another word for a gene

What is an operon

a series of cistrons governed by a single operator and promoter

What is a polycistronic mRNA molecule?

What is horizontal gene transfer?

Donor cell DNA transfered to Recipient cell

Do horizontal gene transfers have to be between the same species?

No

What are the 3 main methods of horizontal gene tranfer?

Transformation, transduction, conjugation

What is transformation

Naked DNA from a ruptured cell is absorbed by an alive competent cell

What is condugation

the transfer of plasmid from one cell to another

What is competent bacteria?

bacteria which can undergo transformation by taking up DNA

Why can plasmids be conjugated?

hey often carry the genes that allow them to initiate and facilitate gene transfer

What is transduction?

When a bacteriophage incorporates bacteria A into its genome and then transfers it into bacteria B

How is peptidoglycan produced?

NAM is synthesized in the cytoplasm and binds to UDP

NAM is linked to bactoprenol

NAG is added to NAM

bactoprenol flips

NAM-NAG structures crosslink

bacterioprenol flips back

What catalyzes crosslinking in peptidoglycan formation?

transpeptidase

What binds during crosslinking in peptidoglycan formation?

Allenine

How does penicilin act?

inactivates transpeptidase

What is periplasm

What is lipopolysaccharide

What is lipid A

Released when a Gram-negative bacterium dies

Causes endotoxin shock (immune system overload)

Why doesn’t natural penicillin work in most Gram-negative infections?

It cannot pass through the outer membrane to irreversibly bind with transpeptidase

How does the gram stain work?

Stained purple with crystal violet

Alcohol removes stains from gram negatives

Re-stained pink/purple with safranin

What shape are cocus bacteria?

Spherical

What shape are bacillus bacteria?

rod shaped

What shape are vibrio bacteria?

comma shaped

What bacteria are named

Those which we can grow