4. Microbial Growth Flashcards by Lisa Chueh

most bacterial and archaeal cells reproduce by

binary fission
divide into 2, one chromosome

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reproductive strategies of bacteria and archaea

some budding, filamentous

all must replicate and segregate the genome prior to division

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increase in cellular constituents that may result in:

-increase in cell number
-increase in cell size

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growth refers to

population growth rather than growth of individual cells

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batch culture

-inoculate
-start with set amount
-limited time of microbe growth

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continuous culture

-culture with broth
-always be replenished with fresh nutrients
-no distinct growth curve

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batch culture growth curve

lag phase
exponential phase
stationary phase
death phase
long term stationary phase

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lag phase

cells acclimating to the environment

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exponential growth

steady growth

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stationary phase

plateau
number of cells dividing = number of cells dying

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continuous culture of microorganisms

growth in an open system
-continual provision of nutrients
-continual removal of wastes

maintains cells in log phase at a constant biomass concentration for extended periods

achieved using a continuous culture system
-constant supply of cells in exponential phase growing at a known rate
-study of microbial growth at very low nutrient concentrations, close to those present in natural environment
-study of interactions of microbes under conditions resembling those in aquatic environments
-food and industrial microbiology

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chemostats and turbidostats:

continually grow cells at a steady rate

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chemostat

rate of incoming medium = rate of removal of medium from vessel

an essential nutrient is in limiting quantities
most stable and effective at lower dilution rates

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turbidostat

regulates flow rate of media through vessel to maintain predetermined turbidity or cell density
dilution rate varies
contains all nutrients in excess
operates best at high dilution rates

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generation (doubling) time

-time required for the population to double in size
-varies depending on species of microorganism and environmental conditions
-range from 10 minutes for some bacteria to days for some eukaryotes

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mathematics of growth equation

x(2^n)

x= # of starting cells
n= # of generations

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extremophiles

grow under harsh conditions that would kill most other organisms

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categories of extremophiles

salt/ solute
temperature
pH
oxygen
pressure conditions

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in hypotonic solutions, microbes

reduce osmotic concentration of cytoplasm

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in hypertonic solutions, microbes

increase internal solute concentration with compatible solutes to increase their internal osmotic concentration

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halophiles

grow optimally in the presence of NaCl or other salts at a concentration above about 0.2 M

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extreme halophiles

-require salt concentrations between 3M and 6.2 M
-extremely high concentrations of potassium
- cell wall, proteins, and plasma membrane require high salt to maintain stability and activity

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nonhalophile

less than 0.2 M

moderate halophile

above 0.2 M will grow but reaches threshold at around 2M before it starts to go down

halotolerant

will not grow but tolerates it before it starts to go down

acidophiles

growth optimum between pH 0 and 5.5

neutrophiles

growth optimum between pH 5.5 and 8

alkalophiles

growth optimum between pH 8 and 11.5

pH preference of microorganisms most bacteria and protists are

neutrophiles

pH preference of microorganisms most fungi prefer

more acidic surroundings, about pH 4 to 6 photosynthetic protists also seem to favor slight acidity

pH preference of microorganisms many archaea are

acidophiles

pH preference of microorganisms alkaliphiles are

distributed among all three domains of life

temperature

microbes cannot regulate their internal temperature enzymes have optimal temperature at which they function optimally high temperatures may inhibit enzyme functioning and be lethal organisms exhibit distinct cardinal growth temperatures -minimal -maximal -optimal

psychrophiles

-10 to 20 celsius can still cause disease- slow

psychrotrophs

0 to 35 RT AROUND 20 listeria (dairy meat/ cheese)

mesophiles

20 to 45 human pathogens

thermophiles

45 to 85 celsius

hyperthermophiles

85 to 113 above boiling would have to apply pressure 140- bonds in biological bonds start to break down, no life above this

adaptations of thermophiles

protein structure stabilized by a variety of means -more H bonds -more proline -more chapterones membrane stabilized by variety of means -more saturated, more branched and higher molecular weight lipids -ether linkages (archaeal membranes)

growth in presence of different oxygen concentrations depends on

a microbes metabolic processes ETC terminal acceptor used

aerobe

grows in presence of atmospheric oxygen which is 20%

obligate aerobe

requires O2 -O2 is an electron acceptor

anaerobe

grows in the absence of O2 *anything but O2 can act as an electron acceptor *aerobic respiration

obligate anaerobe

usually killed in presence of O2

microaerophile

requires 2 to 10% O2 little love air

facultative aerobes

do not require O2 but grow better in its presence *O2 has most potential to grow ATP *can respire/ ferment aero/ anaero

aerotolerant anaerobes

grow with or without O2 *ferments *grows evenly throughout

aerobes produce protective enzymes. for example, catalase

breaks down hydrogen peroxide into O2 and H2O

barotolerant

adversely affected by increased pressure but not as severely as nontolerant organisms

barophilic (peizophilic) organisms

require or grow more rapidly in the presence of increased pressure change membrane fatty acids to adapt to high pressures

most microbes grow ...

attached to surfaces (sessile) rather than free floating (planktonic)

biofilm

attached microbes are members of complex, slime enclosed communities called a ubiquitous in nature in water can be formed on any conditioned surface

biofilm formation

microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA to form the extracellular polymeric substance (EPS) --> very sticky cell to cell signaling starts EXOPOLYMER PRODUCTION additional polymers are produced as microbes reproduce and biofilm matures

heterogeneity in biofilms

differences in metabolic activity and locations of microbes fast growers (may be impermeable to disinfectants, antibiotics, antimicrobials) vs slow growers

the EPS and change in attached organisms' physiology

protect microbes from harmful agents when formed on medical devices, such as implants, illness can result organism sloughing can contaminate water phase above biofilm such as in a drinking water system

bacterial cells in biofilms communicate in a density-dependent manner called

quorum sensing

-produce small proteins that increase in level as microbes replicate and convert a microbe to a competent state -DNA uptake occurs, bacteriocins are released