Control of prokaryotic growth Flashcards
What is mean generation time (g)?
time taken for a population of bacteria to double in number
How to calculate bacterial generation time (G)?
G=t/n
time elapse/number of generation
Generation time for E. coli in the lab
15-20 minutes
Whta is exponential growth?
As population size increases, growth rate increases ?
intercalatory definition
binary cell wall formation is intercalatory (new cell wall froms all the way around the cell as it grows)
Bacterial cell division that produces equal products
binary fission
Bacterial cell division that produces unequal products
4
- simple budding
- budding from hyphae
- cell division from a stalked organism
- polar growth w/o differentiation of cell size (grows at just one end - like hair just grows out ur head)
What are the four bacterial growth stages?
Lag, exponential growth, stationary, death
What is a bacterial continuous culture?
maintenance of a bacterial population at a constant density via flow of fresh medium in and old medium out.
What can cause a bacterial stationary phase?
lack of nutrients
accumulation of toxic by-products
Lag phase
initial time during life where cells are adjusting to new environment and are about to start exponential growth phase
Importance of buffers in bacterial growth media?
Buffer the pH despite bacteria producing their own acids as they grow
Names of bacteria depending on optimal pH for growth (3)
neutrophile
acidophile
alkaliphile
Names of bacteria depending on optimal NaCl (salt) concentration for growth (3)
nonhalophile
halotolerant
halophile
extreme halophile
osmophile
grow in high sugars
xerophiles
grow in dry conditions
How does making compatible solutes benefit bacteria?
allows them to grow when under osmotic stress
osmolytes
small organic compounds that influence properties of biological fluids
osmoprotectants/compatible solutes
small organic molecules (with low toxicity at high concentrations and neutral charge) that help cells survive extreme osmotic stress
Why are compatible solutes called ‘compatible’
compatible with cellular metabolism and biochemistry
obligate aerobe
requires oxygen
facultative aerobe
oxygen not required but grows better with it
microaerophilic aerobe
oxygen required but at levels lower than atmospheric
aerotolerant anaerobe
oxygen not required and growth no better when its present
obligate anaerobe
oxygen is harmful
Example of a compatible solute
glycine betaine in saltlake cyanobacteria
What is the bacterial stringent response?
signalling pathway that allows bacteria to effectively respond to nutrient starvation
What is the bacterial heat shock response pathway?
Increased transcription of heat shock genes to help cope with sudden increased damage to proteins
Rel A
enzyme that increases ppGpp synthesis
ppGpp
guanosine pentaphosphate alarmone produced in response to heat shock
ppGpp functions (2)
- reduces tRNA and rRNA synthesis
2. increases expression of amino acid biosynthetic pathways
What activates Rel A in the stringent response?
uncharged tRNAs entering ribosomal A site
Three main heat shock proteins
HSP70 (DnaK)
HSP60
HSP10
Dnak
heat shock chaperone protein that binds and refolds proteins
RpoH
sigma factor that regulates the heat shock response
sigma factor
promote RNA polymerases to attach to specific initiation sites
