Microbial Growth
- bacterial growth
• exponential growth - doubles every generation >
in vitro microbe growth
• N = N x 2n • inoculum - bacteria being cultured in media
- N is original cells, n is number of generations • medium - collection of nutrients that support
• phases growth
- lag phase: small delay while acclimated • fastidious - hard to grow
- log phase: exponential growth • broths - liquid cultures
- stationary phase: not growing, not dying • selective media - favor growth of one particular
- decline phase: out of resources, dying organism, inhibit others
- open culture system • differential media - facilitate visual differentiation
• limiting factors of growth of microorganisms
- accumulation of waste products, depletion of - pH indicators, salts,
nutrients >
- manitol salt agar (MSA) - both selective, differential
• chemostat - constant flow of fresh medium, removal • pH indicator, mannitol sugar, high salt
of waste • inhibits growth of most bacteria (selective)
• cells continously growing, being removed • pH color change (differential)
physical requirements >
- viable plate counts - viable cells with grow and divide
• optimal conditions differ between species to make 1 colony, colonies are reflection of cell
- temp, pH, oxygen, osmolarity, hydrostatic pressure numbers
• humans are mesophiles; above thermophiles, below •
psychrophiles
> pH
-
• neutrophiles - pH 6.5-7.5
• acidophiles pH 0.0-5
• alkalinophiles pH 8-11.5
- osmotic pressure
• hypertonic conditions - cell shrivels up
• hypotonic conditions - cell takes in water
>
- NaCl concentration
• halophiles - require NaCl for growth, inhabit marine
environments
• halotolerants - tolerate increased, don't grow better
• extreme halophiles - grow better in lot of salt
• osmophiles - high sugar concentration
• xerofiles - dry environment
-oxygen use and tolerance
• obligate aerobe - oxygen required, growth on top of
tube
• faculatative anaerobe - both, greater in presence of
oxygen
• obligate anaerobe - only anaerobic growth, only on
bottom with no oxygen
• aerotolerant anaerobe - only anaerobic growth but
continues in presence of oxygen, growth throughout
• microaerophile - only aerobic with low concentration
of oxygen, growth in middle with small O2
- bacterial growth
• exponential growth - doubles every generation >
in vitro microbe growth
• N = N x 2n • inoculum - bacteria being cultured in media
- N is original cells, n is number of generations • medium - collection of nutrients that support
• phases growth
- lag phase: small delay while acclimated • fastidious - hard to grow
- log phase: exponential growth • broths - liquid cultures
- stationary phase: not growing, not dying • selective media - favor growth of one particular
- decline phase: out of resources, dying organism, inhibit others
- open culture system • differential media - facilitate visual differentiation
• limiting factors of growth of microorganisms
- accumulation of waste products, depletion of - pH indicators, salts,
nutrients >
- manitol salt agar (MSA) - both selective, differential
• chemostat - constant flow of fresh medium, removal • pH indicator, mannitol sugar, high salt
of waste • inhibits growth of most bacteria (selective)
• cells continously growing, being removed • pH color change (differential)
physical requirements >
- viable plate counts - viable cells with grow and divide
• optimal conditions differ between species to make 1 colony, colonies are reflection of cell
- temp, pH, oxygen, osmolarity, hydrostatic pressure numbers
• humans are mesophiles; above thermophiles, below •
psychrophiles
> pH
-
• neutrophiles - pH 6.5-7.5
• acidophiles pH 0.0-5
• alkalinophiles pH 8-11.5
- osmotic pressure
• hypertonic conditions - cell shrivels up
• hypotonic conditions - cell takes in water
>
- NaCl concentration
• halophiles - require NaCl for growth, inhabit marine
environments
• halotolerants - tolerate increased, don't grow better
• extreme halophiles - grow better in lot of salt
• osmophiles - high sugar concentration
• xerofiles - dry environment
-oxygen use and tolerance
• obligate aerobe - oxygen required, growth on top of
tube
• faculatative anaerobe - both, greater in presence of
oxygen
• obligate anaerobe - only anaerobic growth, only on
bottom with no oxygen
• aerotolerant anaerobe - only anaerobic growth but
continues in presence of oxygen, growth throughout
• microaerophile - only aerobic with low concentration
of oxygen, growth in middle with small O2
