MCB Lecture 45 Intro to Bacteria II Flashcards
What are flagella made out of?
Flagellin protein
Describe flagella
These are protein structures that protrude from the bacterium
How is stereotyping of E. coli performed?
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
What are the functions of pilli?
- Adherence of bacteria to other cells, or to tissues in to host
- Conjugation
Where are pilli mostly found?
On Gram negative bacteria
Also found on G+ bacteria
Describe the process of bacterial conjugation
- There are two bacteria (can be unrelated)
- Pilli from one connects to the other, forming a cytoplasmic bridge
- The plasmid in one of the bacteria is replicated, and moves through the bridge to the other bacterium
- The bridge degrades, and now both bacteria have a copy of the plasmid
Conjugation can occur between two … bacteria
Completely unrelated
What are the structures of capsules and slime layers?
These are complex protein layers found on some bacteria
Describe how capsules and slime layers may be removed
Slime layers may be washed off, but capsules may not
What are the functions of capsules?
- Prevent dehydration
2. Prevent phagocytosis
Describe how bacteria with capsules may be stained
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
What are endospores?
These are resistant structures that bacteria can turn into under certain conditions
Describe the life cycle of endospores
Bacteria
Harsh, desolating conditions –> endospore
Once again in a favourable environment –> Bacterium (germination)
Describe how bacteria can resist sterilisation
How do we get around this?
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
Which two endospores forming bacteria are medically important?
- Clostridium: tetanus. Spores enter the body when the individual treads on a rusty nail, and germinate
- Bacillus anthracis
How do bacteria divide?
Describe the features of this process
Binary fission
How do bacteria derive nutrition?
- Exoenzymes (digestive, hydrolytic enzymes) are secreted by the bacterium
- The substrate is digested
- Nutrients are taken across the cell wall into the bacterium by diffusion, active transport, or facilitated diffusion
How do bacteria derive energy from nutrients?
Oxidise the nutrients to release energy in the form of ATP
How can bacteria be classified based on their relationship with oxygen?
Depending on their relationship with oxygen, we put them into one of five groups
What are strict aerobes?
These rely on oxygen to derive energy from their food
What are strict anaerobes?
These die in the presence of oxygen
What are facultative anaerobes?
These can oxidise their food either with or without oxygen
What are aerotolerant anaerobes?
These oxidise their food anaerobic ally, but can tolerate oxygen
What are microaerophiles?
These bacteria require very small amounts of oxygen to survive
Describe how we may classify bacteria, based on the end product of metabolism
Depending on what sort of molecules they produce, we classify them
Eg. Lactic acid, ethanol
What are the different types of culture media?
Liquid (broth) or solid agar
- Selective
- Indicator
- Enriched
What is the final electron acceptor in fermentation?
An organic compound
What are some the ways that E. coli scavenges new genes?
Horizontal:
- plasmids
- transposons
- bacteriophages
- integrons
- pathogenicity islands
