Chapter 6 - Cultivating Microorganisms Flashcards
All cells need access to large amounts of carbon, nitrogen, phosphorus, sulfur, and oxygen (_____________) to build macromolecules.
macronutrients
Various ______________ are also required by microbes for protein structure/activity and includes several metal ions.
micronutrients
__________ capture light energy to produce ATP
Phototroph
___________ capture energy from oxidation of reduced organic or inorganic compounds.
Chemotrophs
____________ acquire their electrons from organic molecules (e.g. glucose)
Organotrophs
___________ acquire their electrons from inorganic sources (e.g. H2 gas and elemental sulfur) - “rock-eaters”
Lithotrophs
__________ assimilate carbon from inorganic sources.
Autotrophs
____________ assimilate carbon in preexisting organic form.
Heterotrophs
Organism that requires certain organic precursors from the environment in order to synthesize all necessary cellular constituents (because they cannot synthesize it themselves).
auxotrophs
Organism that can synthesize all necessary cellular constituents from a single organic carbon source and inorganic precursors.
prototrophes
“capture energy” =
phototrophs & chemotrophs
“acquires electrons” =
organotrophs & lithotrophs
“assimilates carbon” =
heterotrophs & autotrophs
The one key nutrient, available in the lowest amount, that dictates how much growth can occur over time.
limiting factor
_______ grow in the presence of oxygen.
Aerobes
________ _______ REQUIRE oxygen (e.g. humans).
Obligate aerobes
_______________ grow best when there is less oxygen than normal (~2-10%).
Microaerophiles
_________ growth occurs without oxygen.
Anaerobic
____________ anaerobes aren’t harmed by oxygen, but don’t use it either.
Aerotolerant
________ _________ cannot grow when oxygen is present.
Obligate anaerobes
____________ anaerobes CAN use oxygen but can also grow in the absence of oxygen.
Facultative
___________ = pH <5.5
Acidophiles
____________ = pH 5.5-8.5
Neutrophiles
_____________ = pH >8.5
Alkalophiles
_______ ________ and ______ availability can have an effect on microbial growth.
Osmotic pressure, water
Microbial growth is affected by __________. Different microbes have different optimal __________ for growth.
temperature (x2)
The substance on which you grow bacteria.
media
Microbes can be grown in the lab on both solid (____ ______) and liquid media (______).
agar plates, broths
Mound of clonal cells that grow large enough to be seen without a microscope.
colony
Media for microbial growth with an unknown chemical composition is _______.
complex
Media for microbial growth with a precisely defined chemical composition is _______/__________.
defined, synthetic
When cultivating E Coli, LB is a _______ media and M9 is a _________ media.
complex, defined
_________ media allows for isolation of microbes with specific properties (e.g. salt tolerance of mannitol salt agar plates)
Selective
____________ media allows certain microbes to be recognized based on visual reactions in the medium (e.g., lactose fermentation of E. coli on MacConkey agar).
Differential
________ media can be used to increase a particular population of microbes with a specific property from a mixture of cell types.
Enriched
________ media is like selective in that it selects FOR a type of microbe but doesn’t select AGAINST another.
Enriched
__________ agar is both selective and differential. It selects for gram-________ bacteria. It differentiates between _______-__________ and non-fermenting bacteria.
MacConkey, negative, lactose-fermenting.
Many types of bacteria can cause lysis of red blood cells, resulting in a distinctive clear zone around the colonies when cultured on _____ agar.
blood
Separating a mixture of cells into a pure population creates a ____ _______.
pure culture
3 Methods for separating cells on a plate:
- streak plate method
- spread plate method
- pour plate method
Cultivation-independent method for unculturable bacteria = DNA can be amplified and sequenced by ___.
PCR (polymerase chain reactions)
A culture is sterilized and streaked across sectors multiple times to isolate cells and separate colonies.
Streak plate
In ___________, DNA is isolated from an environmental sample and sequenced.
metagenomics
Microbes that are too accustomed to growing with their friends and neighbors to be isolated.
Consortia
Mycobacterium leprae = the bacterium that causes _______, can only be cultured on armadillos because it is a microbial ________.
leprosy, consortia
Methods to measure and count bacteria:
- direct counting
- 3.
A known volume is loaded onto the grid and cells are counted under a light microscope.
pros: cheap, fast, easy
cons: no way to differentiate between living and dead cells
direct counts (Petroff- Hauser counting chamber)
Culture is diluted, dilutions are plated, and colonies are counted. Colony-forming units per milliliter is calculated.
Serial dilutions and CFUs
If cells are already very diluted, a ______ apparatus can concentrate the cells.
filter
Cloudiness of a liquid that can indicate density of suspended particles or cells.
turbitidy
Microbial populations can also be monitored by measuring the turbidity of a liquid culture using a _________________.
spectrophotometer
The spectrophotometer gives a rough measure of cell _______ in the tube.
density
Measuring microbial population growth over time =
the microbial growth curve
Initial period of growth during which cells grow slowly as they adjust to new surroundings.
lag phase
Common features displayed during a growth curve:
- lag phase
- exponential pahse
- stationary phase
- death pahse
Period of growth during which cells divide producing more cells at a maximum rate.
log (exponential) phase
Period where either replication has halted due to lack of nutrients and excessive wastes, or the rate of replication is now equal to the death rate.
stationary phase
Period where nutrients and depleted and waste levels are high, cells are dying at a steady exponential rate.
death phase
Open growth system to which nutrients are continually added and waste products are continually removed (to mimic a stable environment). example = the human gut
continuous culture
A _________ flows in fresh medium and takes out some old medium to keep the culture in continuous operation.
chemostat
__________ = a physical removal of microbes.
filtration
____ can be used to kill microbes.
heat
An __________ adds pressure, keeping fluids from evaporating during the high temperatures, but:
autoclave
hyperthermophiles thrive in high temperatures, microbial structures (endospores) resist high temperatures, some materials can’t be heated
______________ (low-temp heating) to reduce microbe numbers.
pasteurization
________ can damage cells by forming ice crystals, stops biochemical reactions, and is good for long-term preservatives.
Freezing
________________ _________ can be used to control microbes. (UV radiation, ionizing radiation and gamma rays).
Electrochemical radiation
Chemicals used on nonliving surfaces to kill potentially infectious microbes.
disinfectants
Chemicals that can be used on living tissue to kill potentially infectious microbes (usually topically)
antiseptics
Chemical methods of controlling microbes:
- Alcohols
- Phenolic compounds
- Oxidizing agents
- Others
Time required to kill 90% of the target organism under specific conditions.
Decimal reduction time (D value)
