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Cell and Population Growth Part 2 (Bacterial Growth Curves (Log phase…
Cell and Population Growth Part 2
Bacterial Growth Curves
Lag phase
very little or no cell division, cell growth is lagging, cells are gathering nutrients needed to grow
short or long depending on amount of nutrients in the environment
Log phase
bacteria divide logarithmically, continues as long as resources are available
"K"=growth rate constant; max rate
balanced growth: early log phase, produces enough to grow, nothing stored, max efficiency
unbalanced growth: late log phase, lots of cells using up nutrients, starts to respond to stressors, stores nutrients
survival mode: endospore, antibiotics, heat shock proteins
Stationary phase
growth rate=death rate, available resources have been exhausted
Death phase
population decrease, dying cells can provide nutrients for other cells (not as steep as log phase)
Phase of prolonged decline
cells have changed
become more fit to live in harsh conditions
not an endospore
can last months or years
depict amount of bacteria in a population over time
Biofilms
Implications
medical- Streptococcus pneumoniae: in lungs, Candida albicans: fungi, in catheters, UTI
therapeutic- biofilms work together to respond to/resist conditions that would normally destroy them
communities of microbes bound by a thick matrix
not all bacteria form them, can just be part of the life cycle
multiple or just one species
free floating cells attach to desired surface, more cells attach and blend glycocalyx, gets too big and releases cells, not enough nutrients
Chemostat
allows study of bacteria in a specific phase over a long period of time as well as collection of metabolites deemed desireable
keep population at same size
keep environment how it would be in late log phase to collect antibiotics
