Prokaryotic genomes and cell division Flashcards
Three characterisations of a plasmid
circular
small in comparison to prokaryotic chromosomes
replicate independently
R plasmids
typically confer antibiotic resistance
Plasmid incompatibility group
two plasmids from the same incompatibility group are incompatible with each other and they interfere with each others replication
tra genes
make a plasmid self transmissible
Where does chromosomal replication begin?
oriC (origin of replication)
hemimethylated DNA
only old strand is methylated
How are new DNA strands told apart from old DNA strand
absence of methyl groups
SeqA
binds to hemimethylated DNA and prevents DNAa from binding
What DNA can SesA bidn do
mature DNA
HDAa
ATPase that hydrolyses DNAa-ATP to DNAa-ADP
multiple replication forks
allow G to be 20 mins despite whole genome replication taking 40 mins
Where does replication of ColE1 plasmids occur?
at poles of cell, away from nucleoid
Fts proteins
important proteins involved in prokaryotic cell division
FtsZ
Tubulin homologue that self assembles to form a membrane-associated ring structure which is the cell division plane
Divisome
large protein complex in bacteria that mediates cell division
Zip A
anchor that connects and stabilises FtsZ ring to the cytoplasmic membrane
FtsA
recruits FtsZ and other divisome proteins
Helps FTsZ ring connect to cytoplasmic membrane
FtsI
facilitates synthesis of peptidoglycan in the division septum
FtsK
assists in chromosome separation
MinC
x
MinE
oscillates between cell poles, sweeping MinC and MinD aside as it does so causing the centre of the cell to have the lowest concentration of these proteins
Min System
System of proteins that prevent septation and polymersiation of FtsZ at poles; ensures division occurs mid cell.
Nucleoid occlusion
Defence mechanism that prevents chromosomes from being bisected by septum formation
MreB
protein in most rod shaped bacteria that forms bands perpendicular to the cell wall and directs peptidoglycan synthesis
Crescentin
Protein in Caulobacter which causes cell shape to curve by localising at the concave surface of the cell and associating helices of the crescentin filaments with the cytoplasmic side of the cell membrane
alphaproteobacteria
Lack MreB but still have polar growth
Polar growth or budding rather than intercalated growth (growth all the way round the cell wall rather than from one end specifically)
Bacteria with ? depend on Mreb
Lateral dispersed synthesis at multiple points on the cell wall
(lateral elongation)
MreB associated with what shape bacteria
rod shaped
Lack of MreB associated with what shape bacteria
coccoid
Bactoprenol
C55 alcohol that flips peptidoglycan monomer across hydrophobic cell layer
How does bactoprenal insert peptidoglycan monomers into the existing chain? (3)
- autolysins hydrolyse the glycosidic backbone of peptidoglycan
- Transglycosylases stitch in the new unit
- Transpeptidases link DAP to D-Ala to form cross link in transpeptidation reaction
Penecillin bacterial cell division target
transpeptidation
Actinomycin
antibiotic that inhibits transcription by attacking RNA polymerase
Streptomycin
antibiotic that inhibits translation
Beta lactamases
bacterial resistance proteins that break down penecillin
