Control of Prokaryotic Growth Flashcards
Most bacterial cells divide via
binary fission
Describe binary fission
- cell elongation
- central septum formation
- cell wall formation occurs intercalatorially
- cells separate
Describe the products of binary fission
one bacterial cell has equal products under binary fission: 2 genetically identical daughter clones
Describe budding
- simple budding
- budding from hyphae
- unequal products in division
- cell wall formation is not intercalatory, but polar
Give examples of cells exhibiting simple budding
- Pirellula
- Blastobacter
Give examples of cells exhibiting budding from hyphae
- Hyphomicrobium
- Rhodomicrobium
- Pedomicrobedium
Describe Caulobacter formation
- relies on unequal products post-division
- stalks produce differentiated swimmer cells while the stalk itself holds fast
What is Caulobacter
a stalked organism
Give an example of unequal products formation
- when a cell undergoes polar growth without differentiation of cell size (without elongating first)
- occurs in the Rhodopseudomonas, the Nitrobacter and the Methylosinus
What is the adaptation of efficient cell division in bacteria?
exponential growth
One bacterial cell can divide into … after 10 hours
1,048,576
How is bacterial growth rate calculated?
- measure logarithmic cell abundance per ml against time
- plotting this graphically to allow slope calculation (the rate of division)
- can also calculate g
What is g, in terms of bacterial cell division?
the mean generation time (time taken for cell abundance to double)
Why does bacterial culture growth occur in stages?
Because exponential growth is not sustainable in vitro
Describe the experimental set up for investigating bacterial culture growth
- culture inside of a culture vessel with room for a gaseous headspace
- overflow collected
- effluent microbial cells analysed
Describe the classification of stages of bacterial cell culture growth
- lag
- exponential
- stationary
- death phases
Describe the lag phase
- post-incodulation
- due to the change of growth conditions in minerals and nutrients
Describe the exponential phase
- relatively short
- where g is calculated
Describe exponential growth
- requires very rich media
- not always feasible
Describe the death phase
- often protracted
- can be replaced by a quiescent phase if resistance is horizontally acquired
How is bacterial abundance calculated?
- the viable organism count
- turbidity (via optical density)
Explain the inability of expontential growth to persist
- nutrients are limiting
Describe bacterial culture growth on sugar
- usually produce an acid
- toxifies the product, limiting growth by mutation induction
Describe bacterial culture growth on organic acid
tends to alkalise the media, resulting in slowed or arrested growth
How to set up experimentally to maximise the likelihood of prolonged exponential growth
- allow for fresh medium from a resevoir via a flow-rate regulatory mechanism
- sterile air or other necessary metabolic gases
When measuring g
dilution rate is directly proportional to growth rate
Describe the minimum for bacterial temperature
- undergo membrane gelling
- transport processes are so slow as to not facilitate growth
Describe bacteria at their optimum temperature
metabolism is at the maximum possible rate
Describe the maximum for bacterial temperature
- protein denaturation occurs
- cytoplasmic membrane collapse
- thermal lysis
Psychrophile Polaromonas vascuolata
optimum is 4 degrees Celsius
Mesophile Escherichia Coli
optimum is 39 degrees Celsius
Thermophile Geobacillus stearothermophilus
optimum is 60 degrees Celsius
Hyperthermophilic archaea Pyrolobus fumerii
optimum is 106 degrees Celsius
Describe Alkaliphiles
- prefer alkaline pHs (of greater than or equal to 8
- Chloroflexus aurantiacus
- Bacillus firmus
- archaea: Natronobacterium gregoryi