MCB Lecture 45 Intro to Bacteria II

Question 0

What are flagella made out of?

Answer 0

Flagellin protein

Question 1

Describe flagella

Answer 1

These are protein structures that protrude from the bacterium

Question 2

How is stereotyping of E. coli performed?

Answer 2

Two proteins, which are antigens, have many different variations, found on the surface of E. coli
These are O and H antigen.

By finding out the type, we can classify bacteria based on this

Question 3

What are the functions of pilli?

Answer 3

1. Adherence of bacteria to other cells, or to tissues in to host
2. Conjugation

Question 4

Where are pilli mostly found?

Answer 4

On Gram negative bacteria

Also found on G+ bacteria

Question 5

Describe the process of bacterial conjugation

Answer 5

1. There are two bacteria (can be unrelated)
2. Pilli from one connects to the other, forming a cytoplasmic bridge
3. The plasmid in one of the bacteria is replicated, and moves through the bridge to the other bacterium
4. The bridge degrades, and now both bacteria have a copy of the plasmid

Question 6

Conjugation can occur between two … bacteria

Answer 6

Completely unrelated

Question 7

What are the structures of capsules and slime layers?

Answer 7

These are complex protein layers found on some bacteria

Question 8

Describe how capsules and slime layers may be removed

Answer 8

Slime layers may be washed off, but capsules may not

Question 9

What are the functions of capsules?

Answer 9

1. Prevent dehydration

2. Prevent phagocytosis

Question 10

Describe how bacteria with capsules may be stained

Answer 10

They won’t take up the Gram stain
Instead, the background is stained, and so the bacteria are seen where there is no stain

This is called Negative Staining

Question 11

What are endospores?

Answer 11

These are resistant structures that bacteria can turn into under certain conditions

Question 12

Describe the life cycle of endospores

Answer 12

Bacteria
Harsh, desolating conditions –> endospore
Once again in a favourable environment –> Bacterium (germination)

Question 13

Describe how bacteria can resist sterilisation

How do we get around this?

Answer 13

They turn into endospores, which are really resistant to heat, pH and many chemical disinfectants
To get around this, we need to perform high pressure boiling in an autoclave

Question 14

Which two endospores forming bacteria are medically important?

Answer 14

1. Clostridium: tetanus. Spores enter the body when the individual treads on a rusty nail, and germinate
2. Bacillus anthracis

Question 15

How do bacteria divide?

Describe the features of this process

Answer 15

Binary fission

Question 16

How do bacteria derive nutrition?

Answer 16

1. Exoenzymes (digestive, hydrolytic enzymes) are secreted by the bacterium
2. The substrate is digested
3. Nutrients are taken across the cell wall into the bacterium by diffusion, active transport, or facilitated diffusion

Question 17

How do bacteria derive energy from nutrients?

Answer 17

Oxidise the nutrients to release energy in the form of ATP

Question 18

How can bacteria be classified based on their relationship with oxygen?

Answer 18

Depending on their relationship with oxygen, we put them into one of five groups

Question 19

What are strict aerobes?

Answer 19

These rely on oxygen to derive energy from their food

Question 20

What are strict anaerobes?

Answer 20

These die in the presence of oxygen

Question 21

What are facultative anaerobes?

Answer 21

These can oxidise their food either with or without oxygen

Question 22

What are aerotolerant anaerobes?

Answer 22

These oxidise their food anaerobic ally, but can tolerate oxygen

Question 23

What are microaerophiles?

Answer 23

These bacteria require very small amounts of oxygen to survive

Question 24

Describe how we may classify bacteria, based on the end product of metabolism

Answer 24

Depending on what sort of molecules they produce, we classify them

Eg. Lactic acid, ethanol

Question 25

What are the different types of culture media?

Answer 25

Liquid (broth) or solid agar

1. Selective
2. Indicator
3. Enriched

Question 26

What is the final electron acceptor in fermentation?

Answer 26

An organic compound

Question 27

What are some the ways that E. coli scavenges new genes?

Answer 27

Horizontal:

• plasmids
• transposons
• bacteriophages
• integrons
• pathogenicity islands