Microbiology Flashcards
What do bacteria have instead of a nucleus?
Nucleoid- DNA and associated proteins
No nuclear membrane
Co transcription and translation via DNA dependent RNA polymerase
How is the chromosome arranged in a bacteria?
Single circular chromosome organised by gyrases
What are DNA gyrases?
Essential bacterial enzymes that catalyses the DNA dependant negative super coiling of double stranded closed circular DNA (part of topsomerases)
What are extra chromosomal replications called?
Plasmids
Where do most biochemical processes take place in a prokaryote?
The cell membrane as tehre are no membrane bound organelles
How is energy generated in a bacterial cell?
Electrons are released from high energy compounds in the cytoplasm. They reach the membrane and are passed through a series of electron acceptors.
The energy released from this pumps H+ ions outside of the membrane producing an electrochamical gradient.
Inflow of protons generates ATP.
NB: This occurs on the surface of the cell- therefore if you damage the membrane you will damage/kill the bacteria
What is peptidoglycan made from?
2 Sugars NAM = N-acetyl muramic acid NAG = N-acetyl glucosamine and peptide bridges with 5 types of protein Repeated polysaccharide structure
Why do bacteria require a cell wall?
High osmotic pressure and concentrated cytoplasm
What is the target for penicillin?
Peptidoglycan cell wall
Describe the cell wall in a gram positive bacteria?
Thick multilayered peptidogylcan
Rope structure
Survive 8-10 atmospheres
Describe the cell wall in a gram negative bacteria?
Thin peptidoglycan layer
Survive 5-6 atmospheres
2 cell membranes (inner and outer)
Lipopolysaccharide extensively on outer membrane
What is the role of glycolipids?
Lipid A and core polysaccharide
Structural support but also as an antigen, bacterial toxin
What are flagella and fimbrae?
Proteinachious extensions
Which bacteria have flagella and what is the function?
Both gram positive and gram negative
Huge SA to help with attachment and adhesion of bacteria together
Some inject RNA and toxins
Useful for motility
What is a fimbrae/pillus and which bacteria have which one?
Non flagella proteinacious abhendage
Fibrae = gram positive
Pillus = gram negative (=> biofilm formation)
Used for adherence and sex in both
Where does prokaryotic protein synthesis take place and what are the features?
Cytoplasmic membrane
Co-transcription/translation
No polyadenylation of transcript (addition of poly A tails to mRNA)
Rapid => higher mutation rate
What is required for binary fission?
Food: C, H, O, N, Inorganic salts (metal), Trace elements (Zn, Cu, Mn, Ni) and vitamins (Folic acid and Niacin)
Specific temp, pH, osmotic protection and oxygen concentration
What are the 4 phases of binary fission?
1) Lag phase
2) Exponential phase
3) Stationary phase- all nutrients used up
4) Decline phase- bacteria die and produce toxins. No more nutrients
What is a bacteria called that works at low, high and body temp?
Low = Psycrophiles
High = Thermophiles
Body temp = mesophiles
What is the preferred pH and osmotic protection for human commensal bacteria?
- 8-7.2 pH
0. 85% NaCl
What is a microaerophile?
A bacterium which requires oxygen at a less than atmospheric pressure
Bacteria can sense there population density. T or F?
True
What is multicellularity?
Colony development and differentiation
What are planktonic cells?
Free flowing bacteria in suspension