chapter 6: microbial growth Flashcards
-phile
lover
-phobe
hater / fearer
psychro-
cold
thermo-
heat
meso-
middle
hyper-
more than / greater
hypo-
less than
auto-
self
hetero-
other
halo-
salt
glyco-
sweet
micro-
little
macro-
big / much
aero-
air
geo-
earth
litho-
rock
-troph
feeder
which bacteria grow well at 0°C?
psychrotrophs
which bacteria grow well at refrigerator temperature?
mesophiles
which bacteria includes the most spoilage and disease organisms & what is its optimal growth range?
psychrotrophs (0-30°C)
which bacteria can grow at 100°C?
hyperthermophiles (>80°C)
which bacteria are at work in a temperature of 60°C?
thermophiles (50-60°C)
acidophile
grow in acidic environments; a form of extremophile
halophile
grow in high salt concentrations
obligate halophile
can only survive in a high salt concentration environment; (environment with high osmotic pressure)
facilitative halophile
can survive with or without a high salt concentration environment
plasmolysis
the loss of water due to a hypertonic situation
carbon source
the use of a carbon containing molecule (carbohydrate, amino acid, CO2…) to synthesize organic molecules
fixation
process in which a substance is removed from the gaseous or solution phase and is localized
SPONCH (major components of compounds found in microorganisms)
sulfur, phosphorus, oxygen, nitrogen, carbon, hydrogen
culture medium
nutrients prepared for microbial growth
sterile
no living microbes
inoculum
introduction of microbes into a medium
culture
microbes growing in or on a culture medium
what is agar used for?
a solidifying agent for culture media in petri plates, slants, and deeps
chemically defined media
media where the exact chemical composition is known
complex media
chemical composition varies batch to batch; blood, herbal extract, yeast
trace elements
elements required in small amounts; Ex) iron, copper, zinc
obligate aerobe
oxygen is required for growth
facultative anaerobes
can grow with (aerobic respiration) or without (fermentation) the presence of oxygen; greater growth in presence of oxygen
obligate anaerobe
unable to use oxygen / harmed by it
aerotolerant anaerobe
tolerate but cannot use oxygen for growth
microaerophile
requires oxygen concentration lower than air
reactive oxygen species (ROS)
singlet oxygen: ¹O₂- superoxide radical: O₂ peroxide anion: O₂²⁻ hydroxyl radical: OH (harmful to cells in large quantities; lethal to cells in small doses if cells lack proper enzymes)
biofilm
a microbial community; form slime or hydrogels that adhere to surfaces
what do bacteria cells use to communicate?
quorum sensing
selective media
suppresses unwanted microbes (using inhibitors) and encourages desired microbes
Ex) salting foods
differential media
allow distinguishing of colonies of different microbes on the same plate
enrichment culture
encourages growth of a desired microbe by increasing very small number of desired organism to detectable levels (usually a liquid)
purpose of the streak plate method
used to isolate pure cultures; acquire a single colony of many identical cells
what is microbial budding?
instead of using binary fission, a microbe grows smaller offspring on their bodies
which process divides a non-enclosed nucleoid in two?
binary fission
what is bacterial growth?
the multiplication of bacteria / increase in number of cells (more so than increase in cell size)
what does the log representation of a microbial growth graph emphasize?
growth rate
phases of bacterial growth (4)
lag phase, log phase, stationary phase, death phase
what occurs during the lag phase of bacterial growth?
bacteria prepares for growth / are adjusting to situation
what occurs during the log phase of bacterial growth?
logarithmic / exponential increase in population
what occurs during the stationary phase of bacterial growth?
period of equilibrium; microbial deaths balance production of new cells
what occurs during the death phase of bacterial growth?
population decreases at a logarithmic rate; caused by the exhaustion of nutrients for bacteria or pollution of media
serial dilution
stepwise dilution of a solution to find the number of bacteria in original inoculum; reduces concentration of cells to avoid overcrowding which could prevent growth on medium
plate count
count colonies on plates that have 30-300 colonies (CFU - colony forming units)
filtration
solution is passed through a filter that collects bacteria; used for low levels of bacteria to grow out on a petri dish
direct microscope count
calculates average number of bacteria per viewing field; number of bacteria / ml = (# of cells counted) / (volume of area counted)
what are the direct measurements for microbial growth?
plate count, filtration, direct microscope count,
what are the indirect measurements (estimations) for microbial growth?
turbidity, metabolic activity, dry weight
turbidity (and instrument used)
measurement of cloudiness with a spectrophotometer
which organisms use the indirect measurement of dry weight?
filamentous organisms (most fungi and a few bacteria)
