4. Microbial Growth Flashcards
most bacterial and archaeal cells reproduce by
binary fission
divide into 2, one chromosome
reproductive strategies of bacteria and archaea
some budding, filamentous
all must replicate and segregate the genome prior to division
increase in cellular constituents that may result in:
-increase in cell number
-increase in cell size
growth refers to
population growth rather than growth of individual cells
batch culture
-inoculate
-start with set amount
-limited time of microbe growth
continuous culture
-culture with broth
-always be replenished with fresh nutrients
-no distinct growth curve
batch culture growth curve
lag phase
exponential phase
stationary phase
death phase
long term stationary phase
lag phase
cells acclimating to the environment
exponential growth
steady growth
stationary phase
plateau
number of cells dividing = number of cells dying
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
chemostats and turbidostats:
continually grow cells at a steady rate
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
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
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
mathematics of growth equation
x(2^n)
x= # of starting cells
n= # of generations
extremophiles
grow under harsh conditions that would kill most other organisms
categories of extremophiles
- salt/ solute
- temperature
- pH
- oxygen
- pressure conditions
in hypotonic solutions, microbes
reduce osmotic concentration of cytoplasm
in hypertonic solutions, microbes
increase internal solute concentration with compatible solutes to increase their internal osmotic concentration
halophiles
grow optimally in the presence of NaCl or other salts at a concentration above about 0.2 M
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
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
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
