Bacterial Growth and Division: L3A Flashcards
define growth
result of cell division and key to the life of a bacterium
binary fission
elongation of cell to twice original length, formation of partition that constricts cell into two daughter cells
generation time
time for one cell to generate to two cells
budding division:
formation of new daughter cell with mother cell retaining its identity
One generation of growth
- Macromolecules e.g proteins accumulate in cytoplasm
- Incorporated into cell wall, membrane, ribosomes enzymes and new DNA
- DNA replicates
- Cell elongates
- Semi-conservative, newly made DNA separates into two chromosomes
- Chromosomes move to opposite poles
- Septum forms in middle of elongated cell and it separates into two
Bacterial cell division stages?
stage 1: chromosome replication
stage 2: chromosome segregation
what is a divisome?
complex of cell proteins controlling the division
what do min proteins control?
FtsZ
what does bactoprenol transport when making new peptidoglycan?
new precursors across cytoplasmic membrane
what do autolysins do when making new peptidoglycan?
make gaps in the cell wall
what does bactoprenol interact with?
transglycosylases to insert precursors into cell wall
what is transpeptidation
Final step in peptidoglycan synthesis
what inhibits the transpeptidase
Penicillin
how does bacteria grow?
exponentially
name the stages of bacteria growth (graph)
LAG - adaptation
LOG - (exponential) cells dividing rapidly
STATIONARY - nutrients depletes, division = death rate
DEATH - waste metabolites build up, cells die
how do we use microscopy for microbial growth?
total cell count
how do we use colony counting for microbial growth?
viable bacterial numbers
what are the 3 method for bacterial growth?
spread plate, pour plate, micropipetting
what does spectrophotometry measure?
optical density
what are psychrophiles?
they grow at log temperatures (0-20)
what grows at midrange temperatures?
Mesophiles (20-40)
what are thermophiles?
grow at high temps +45
what grows at VERY high temperatures?
hypthermophiles - above 80
what do acidophilus have?
very stable cytoplasmic membranes destroyed at neutral pH
what do cytoplasmic membranes restrict?
proton entry
what do alkaliphiles have?
unique energy requirements and are killed at too low a pH
what pH must the internal environment be for bacteria
the same pH for all bacteria usually pH 4-9
what are halophiles?
Grown in high SALT concentrations, 6-15% NaCl
what are halotolerant?
Grow in high salt concentrations but prefer none, 1-6% NaCl
what are extreme halophiles?
Grow in very high salt concentrations - 15-30% NaCl
what are osmophiles?
grow in high SUGAR concentrations
what are xerophiles?
grow in dry environment
what are aerobes full of?
full of oxygen tension
what do microaerophiles use?
oxygen when it is present at a lower concentration than air
what do facultative aerobe grow without?
oxygen in the correct environment
what are anaerobes?
cannot respire oxygen
what are aerotolerant anaerobes?
can tolerate oxygen
what is an obligate anaerobe?
killed by oxygen
what is sporulation?
Survival tactic of some bacteria
describe facts about sporulation
- Metabolically inactive so dont need nutrients
- Highly resistant to heat, chemicals etc
- Spread by wins, animals, water, through the gut
what are factors of sporulation?
- Stress leads to the phosphorylation of sporulation factors
why are spores medically important?
- Major cause of hospital acquired diarrhoea
- Hard to eradicate
- Transmission and outbreaks hard to control
