Lecture 3 - Structure and function of bacteria Flashcards
What is the capsule composed of and how can it be protected
Polysaccharides or polypeptide (called slime layer or glycocalix) which is a sticky layer of goo on outside.
It can prevent desiccation and prevent phagocytosis as the slime capsule can hide the bacteria from the immune system a bit more
What does plaque (e.g.streptococcus mutans) stick to teeth
The sticky capsule
Describe a biofilm
Community of microorganisms stuck together in a goo so they stick to a surface. They function as a unit.
Describe issues with bio films
Hard to control, more resistant to cleaning and antibiotics.
Name and describe the 4 types of flagella
Monotrichous - single polar flagellum
Lophotrichous - two or more at one/both ends
Amphitrichous - single polar flagellum at each end
Peritrichous- disturbed over entire cell
Describe a typical prokaryotic cell
Cytoplasm, nucleoid, ribosomes, cytoplasmic membrane, cell wall, capsule, flagella
In gram negative or gram positive bacteria does the flagellum spin anti-clockwise to move forward?
Gram negative
What are the 3 rings called in the flagellum that penetrate the cell wall (from lipid layer to inner membrane)
L (lipid)
P (peptidoglycan)
M (membrane -inner)
Which way would gram negative bacteria spin their flagellum to move backwards
Clockwise
What is the process called of a bacterial cell undergoing motility and describe the process
Run and tumble.
Run - moving forward towards with bundled flagella
Tumble - flagella pushed apart from clockwise rotation until aware of direction to travel
Run again in direction
What are the two types of Chemotaxis and describe the
Positive Chemotaxis - movement towards a molecule
Negative - movement away from a molecule
What is the difference between fimbrae and pili
Fimbrae - early attachment structure, have hooks so organisms moved through the body with food use fimbrae to grapple on side of gut
Pili- join 2 cells together. Bacteria can undergo a form of sexual recombination of genome through pilus (whereas normally clone) give to DNA to another cell
How many fimbrae are there compared to pili
Fimbrae many fibres whereas pili one to two per cell
What protein is pili made of
Pillin
List two functions of the cell wall in gram negative and positive bacteria
Prevent osmotic rupture and contributes to disease mechanisms
What are the repeating subunits that form peptidoglycan
NAG - N-acetylglucosamine
NAM - N-acetylmuramic acid
What does the outer membrane of the gram negative bacteria have
Lipopolysaccharide sticking up - endotoxins which trigger the immune system to give certain presentations of gram negatives infection. Also has a porin protein
What is the LPS made of
LIPID A and O polysaccharide
How much of bacterial cells are water
70%
What is the internal matrix of the cell (cytoplasm) composed of and what other things are contained within the cytoplasm
80% H2O
Proteins, COH, lipids
Other things - inclusion bodies (store things), DNA, ribosomes
How is the genome split in bacteria
Chromosomes and plasmid (replicate independently of genome) which is transferable.
What is conjugation?
Pilus is link where copied plasmid can go through so both cells have plasmid
What is transformation?
Transfer genetic info without the bacterial cell being in the environment. When cells die they tend to lyse - bacterial cells take up DNA when naked DNA bind to cell wall and taken up by bacteria.
What is transduction
VIRUSES Take DNA from one cell and put it in another.
What is horizontal gene transfer
Bacterial genome influenced by environment leads to changes e,g. Plasmid and genetic lineage taken up by surrounding cells e.g. Lecturer give us info
What is vertical Lineage
Bacterial cells give info to offspring e,g, lecturer give info to his children
What is the total S for the ribosomes in prokaryotes and eukaryotes
70s prokaryotes
80s eukaryotes
What antibiotics target ribosomes
Streptomycin
Neomycin
Tetracyclines
Name the inclusion body that stores phosphates if there is a loss of them
Volutin
On what type of bacteria do endospores occur and give examples
Gram positive
Clostridium and bacillus
At what 4 positions can the endospore form
Terminally (at one end)
Sub terminally (near one end)
Centrally
Size (same size as cell so doesn’t make it swell)
Is sporulation a replicative process
No the cell undergoes sporulation to protect the cell from a harsh environment
1 cell = 1 endospore
Describe the process of sporulation
1- Take a big bit of genome and move it to one Side of cell
2- begin to grow membrane around it so forms a forespore
3- start to protect it layer it in coats of peptidoglycan so if environment gets harsh then it is protected.
4- when environment gets better the cell starts to grow out and it’s called germination.
5- water gets into cell so spore swims away
Describe the process of germination
1- germination 2- swelling 3- shedding of spore wall 4- outgrowth of vegetative cell 5- cell division
Compare exotoxins and endotoxins
Exotoxins - gram + bacteria, produced inside bacteria as part of growth and released from cell
Endotoxins - part of gram - cell wall.
Describe the structure of exotoxins and their features
Protein molecules - have active (a group) subunit and binding (b group) subunit so SPECIFIC
MAINLY GRAM +
- soluble in blood
- rapid transmission
- rapid onset of symptoms
Give two examples of exotoxin producers
Clostridium botulinum - inhibits release of acetylcholine (toxin bind to other side, muscle flaccid and paralysis)
Clostridium tetani - inhibits removal of acetylcholine (spasmic paralysis, tetanus toxin blocks other side, fits and spasms and die)
Describe the structure of endotoxins and their features
Outer cell wall of gram -.
Lipid portion of LPS - lipid A
Released on cell lysis
Symptoms, same regardless of species
- severity can vary
- fever, weakness, general aches, shock.
Cause immune system to go into panic
General
