Structure of Bacteria Flashcards
What are the different cell morphology?
- Coccus
- Spirochete
- Rod
- Budding and appendages bacteria
- Spirillum
- Filamentous bacteria
What shape is coccus ?
Spherical shaped bacteria
What is an example of rod-shaped bacteria?
E.coli
What shape is spirillum bacteria?
Curved shaped bacteria
What shape is spirochete?
Cork screw shaped bacteria
How do measure cell size?
Surface area to volume ration
Does a larger S:V ratio have a faster or slower uptake of nutrients?
Faster
What does the cell wall of animal cells consist of?
Phospholipid bilayer, interspersed wit protein
What does the cell wall of plant cells consist of?
Phospholipid bilayer, mesh of cellulose surrounding it
What does the cell wall of bacterial cells consist of?
Gram-negative and Gram-positive both have phospholipid bilayer but differ in many ways
What is a cytoplasmic membrane?
Phospholipid bilayer - 1 glycerol attached via 2 hydroxyl groups to 2 fatty acids
How do phospholipid differ in characteristics?
Different molecules attached to polar head of another hydroxyl on the glyceral
What adds strength to a cytoplasmic membrane?
Hopanoids
What are essential for mycoplasmas?
Sterols
Why are sterols essential for mycoplasma?
Strengthen cell wall in bacteria
What bond do bacteria and eukary have in the phospholipid bilayers?
Ester linkage
What bond do archaea have in phospholipid bilayer?
Ether linkage
Describe the phospholipid bilayer of an archaea:
- Repeating units of isoprene
- Linked to form phytanyl
- 2 phytanyl can join at each other ends to form diglycerol tetraethers
What is better by having repeating units of isoprene in archaea than fatty acids in Bactria and eukary?
More robust
More stronger
Suit harsh conditions
What are peptidoglycan made up of?
N-acetylglucosamine
N-acetylmuramic acid
forms a tetra peptide
What are the N-acetylglucosamine and N-acetylmuramic acid bonded together by?
Glycosiding bond at B1,4 linkage
How much does peptidoglycan make up of the cell wall in Gram-positive bacteria?
90%
How much does peptidoglycan make up the cell wall in Gram-negative bacteria?
10%
What links the two tetrapeptides in a Gram-positive bacteria?
Pent-glycine bridge (DAP — d-Ala)
What links the two tetrapeptides in a Gram-negative bacteria?
Covalently bonded
What is peptidoglycan?
Mesh like layer which protects a bacteria cytoplasmic membrane
What type of Gram has a second bilayer?
Gram-negative
How is the second phospholipid bilayer in a gram-negative organised?
Asymmetrical
What does the second phospholipid bilayer in a gram negative consist of?
- O antigens
- Interspaced with proteins, porins
- Large polysaccharide components
What are O antigens?
Carbohydrate structure:
O-polysaccharides, corepolysaccharides and lipid A
Why do you phospholipid bilayer is have porins?
Allows transfer of molecules across a lipid bilayer
How do you describe bacteria with O-antigens?
Smooth bacteria
How do you describe bacteria without O-antigens?
Rough bacteria
What is the structure of a Gram-positive bacteria?
Large peptidoglycan
Phospholipid bilayer
What is the structure of a Gram-negative bacteria?
Small peptidoglycan
2x phospholipid bilayer
Give three cell surface structures of bacteria:
- Capsules
- Fimbriae and pili
- Flagellar
Describe a capsules:
- Can be polysaccharides or proteins
- role in pathogenesis and biofilm formation
Describe fimbriae and pili:
- proteinaceous, can be glycosylated
- role in pathogenesis, biofilms and conjunction
- Involved in twitching motility
What can a pilus be used for?
Transferring DNA from one cell to another
Describe a flagella:
Multimeric protein complex traversing both inner and outer membranes
What are the different localisation of flagella?
- Peritrichous
- Polar
- Lophotrichous
- Amphitrichous
How can bacteria move?
Using a flagella
How many times per second is the flagella rotating?
100 rotations per second
What is a reversible flagellum?
Flagellum can rotate in counterclockwise (Moves forwards) or clockwise (moves backwards)
What occurs to the cell is a bacteria that has a bundle of flagellum rotating counterclockwise direction?
Cell moves forwards
What happens if a bacteria has a bundle of flagellum which is rotating clockwise?
Bundle unravels and bacteria tumbles and turns – allows bacteria to move towards optimum environment
What are the components of a flagellum?
Helical filament and basal body connected by a hook
The hook in the flagellum is it flexible or constricted?
Flexible
A flagellum has a MS ring where is it located?
Cytoplasmic reticulum
A flagella has a C ring where is it located?
Cytoplasm
What type of rings are present in a gram negative flagellum?
L and P ring
What do L and P rings do you in gram negative flagellum?
Guide spinning rod through cell (do not spin)
Why does a gram positive bacteria have no L and P rings in their flagellum?
Lack of outer membrane
What is the role of Mot protein surrounded by an inner ring in the flagellum?
Anchors flagellum in cytoplasmic membrane
What is the role of Fli protein in the flagellum?
Axis motor switch via reversing the direction of rotation of flagellum
What are motors powered by?
Energy from protein gradient
Where does the protein gradient that powers the motor exist across?
Cytoplasmic membrane
How does the proton gradient provide energy for the motor of a flagellum?
- Proton concentration higher in periplasmic space than inside cell
- electrons flow down electrochemical gradient
- release energy as a flow
What the movement turns MS and C rings and rod in flagellum?
The movement of protons
