Prokaryotic Growth Flashcards
(37 cards)
Prokaryotic cells divide by what process?
Binary Fission
What is the Generation time?
Time it takes for population to double (varies among species)
How can bacterial population growth be calculated (formula)?
Nt = N0 x 2n
(Nt ) number of cells in population
(N0 ) original number of cells in the population
(n) number of divisions
How are Biofilms Formed?
- Attachment~ Formation begins when planktonic bacteria attach to surfaces
- Expansion~ Other bacteria attach and grow on initial layer
- Maturation/ Resistance~ Secretion of slime layer (glycocalyx)
What are some characteristics of biofilms?
- Complex, channels for diffusion and exchange of nutrients, gases etc.
- Resistant to antimicrobial agents
- Persistent
What is a pure culture?
A population of organisms descended from a single cell and therefore separated from all other species
Why do we seek pure cultures in the lab?
Prokaryotes in the environment grow in close association with many different species, but this is too hard to study, so we isolate them.
Which scientist tried potatoes and gelatin as mediums before discovering agar?
Koch
What does growth within a batch system involve?
No new input of nutrient and no release of waste
What pattern does a population of cells follow?
A growth curve
What are the 5 growth curve stages?
- Lag stage
- Exponential or log stage
- Stationary stage
- Death stage
- Phase of prolonged decline
What features characterize the Lag Phase on a growth curve?
- Number of cells does not increase
2. Cells prepare for growth (“tooling up”)
What features characterize the Log Phase on a growth curve?
- Period of exponential growth (Doubling of population with each generation)
- Early~ Produce primary metabolites (Compounds req’d for growth)
- Late~ Synthesize secondary metabolites
(Used to enhance survival, ex antibiotics)
What features characterize the Stationary Phase on a growth curve?
- Overall population remains relatively stable
- Cells exhausted nutrients
- Cell growth = cell death
- Dying cell supply metabolites for replicating cells
What features characterize the Death Phase on a growth curve?
- Total number of viable cells decreases
2. Decrease at constant rate
What features characterize the Phase of Prolonged Decline on a growth curve?
- Once nearly 99% of all cells dead
- Marked by very gradual decrease in viable population
- Phase may last months or years
How much Oxygen do Obligate aerobes require for growth?
Absolute requirement for oxygen
~ Use for energy production
How much Oxygen do Obligate anaerobes require for growth?
No multiplication in presence of oxygen
~ May cause death
How much Oxygen do Facultative anaerobes require for growth?
Grow better with oxygen but can grow in absence of oxygen
How much Oxygen do Microaerophiles require for growth?
Require oxygen in lower concentrations
~ Higher concentration inhibitory
How much Oxygen do Aerotolerant anaerobes
require for growth?
Indifferent to oxygen, grow with or without
~ Do not use oxygen to produce energy
Which bacteria can’t synthesize their own macromolecules?
fastidious bacteria
Which “trophes” use organic carbon as nutrient source
Heterotrophs
Which “trophs” use inorganic carbon (CO2) as carbon source?
Autotrophs
