Microbial Nutrition and Growth Flashcards
Microbial growth
increase in a population of microbes
Growth requirements
use variety of nutrients for the energy needs to build organic molecules and cellular structures
Oxygen requirements
Oxygen is essential for obligate aerobes.
Oxygen is deadly for obligate anaerobes.
Four toxic forms of oxygen
Singlet oxygen
Superoxide radical
Peroxide anion
Hydroxyl radical
Facultative anaerobes
grow better with O2, but can live without it
Aerotolerant anaerobes
are unaffected by O2 levels
Nitrogen fixation
by certain bacteria is essential to life on Earth.
All cells recycle nitrogen for amino acids and nucleotides
Trace elements
only required in small amounts
Growth factors
Necessary organic chemicals that cannot be synthesized be certain organisms. For example, vitamins
Physical requirements - Temperature
Temperature affects three-dimensional structure of proteins. If too low, membranes become rigid and fragile. If too high, membranes become too fluid. Bacteria love our temp.
Mesophiles
microbes that are comfortable around our body temperatures
Psychrophiles
comfortable around 15-degree Celsius
Psychrotolerant
organisms can tolerate, but don’t grow best in the cold
Thermophiles
grow at temp above 45-degree celsius such as compost piles and hot springs
Hyperthermophiles
grow at temp above 80-degree celsius
pH - Physical Requirements
organisms sensitive to changes in acidity
Neutrophiles
grow best in a narrow range around neutral pH
Acidophiles
grow best in acidic habitats
Alkalinophiles
live in alkaline soils and water
Water - Physical Requirements
microbes require water to dissolve enzymes and nutrients and water is also important in reactant in many metabolic reactions. Most cells will die in the absence of water, therefore, some cells retain water. Endospores and cysts will stop metabolic activity in dry environments and still survive.
Osmotic pressure
solution is the pressure exerted on a membrane by a solution containing solutes that cannot cross freely the membrane
Hydrostatic pressure
water exerts pressure in proportion to its depth
Hypertonic solution
lower solute concetration
Hypotonic solution
greater solute concetrations
Obligate and facultative halophiles
restricts organisms to certain enviroments, like growing in high osmotic pressure/higher salt concetration
Biofilms
complex, synergistic relationships
Culture
the act of cultivating microorganisms or the microorganisms that are cultivated
Inoculum
to cultivate microorganisms is introduced into a collection of nutrients called a medium
Colony forming unit (CFU)
cultures composed of cells arising from a single progenitor; the progenitor is termed CFU
Streak plate
spreading inoculum across the surface of a petri dish
Pour plates
CFUs are separated from one another using a series of dilutions
Culture media
variety of liquid and solid media used to culture, grow, microbes
Nutrient broth
common liquid medium
Agar
common addition to make media solid; commonly used to make petri plates and slant tubes
Slant tubes
used for fungal identification; warm agar is poured into test tubes at an angle and left to cool until the agar solidifies
Defined media
used for research; exact chemical composition is known
Complex media
contains reasonably familiar material but varies slightly in chemical composition from batch to batch; exact chemical composition is unknown; nutrients commonly derived from breakdown of yeast, beef, soy, and proteins; supports growth of a wide variety of microorganisms; useful when nutritional needs of an organism are unknown
Yeast extract - Complex Media
most routine lab cultures use mediaa containing peptone from meat or fish and such media are sometimes enriched w yeast extract, which contains a number of vitamins, conenzymes, and nucleotides
Casein Hydrolysate
made from milk and contains many amino acids and used to enrich media.
Blood Nutrients
blood also contains nutrients that is needed for some pathogens, including, serum, blood (agar), and heated blood (chocolate agar)
Selective media
contain substances that favor or inhibit growth of particular microorganisms
Differential media
has an ingredient in it that will cause a color change on the media or the colony; during this process, we are looking for metabolic pathways that have a series of chemical reactions that could be associated with the waste products that could be pH or bind with something that could cause the color change in the first place
Nutrient agar
Gram positive and Gram negative will grow here
MacConkey agar
selects Gram negative and inhibits Gram positive; however, lactose can also come into play if it can ferment. Those that could ferment lactose will stand out, those that can’t won’t be easily distinguishable. Fermentation of lactose will start to make acid and have the colony then turn red.
Transport media - culture media
used by healthcare personnel to ensure clinical specimens are not contaminated and to protect people from infection; rapid transport of samples is important
Preserving cultures
refrigeration-stores for short periods of time
deep freezing-stores for years
lyophilization-stores for decades; involves removing water from a frozen culture through an intense vacuum
Binary fission
most unicellular microorganisms reproduce through this technique by having the cell grow twice its size and divide in two producing daughter cells
Generation time
time required for a bacterial cell to grow and divide depending on chemical and physical conditions; ex tuberculosis is really slow to grow
Lag phase - bacterial growth curve
cells are adjusting to their new environment
Log phase - bacterial growth curve
population increases logarithmically, which is faster then arithmetically
Stationary phase - bacterial growth curve
eventually the number of dying cells equals the number of cells being produced and the size of the population remains constant
Death phase - bacterial growth curve
if nutrients are not added and wastes not removed, a population reaches a point at which cells die at a faster rate than they are produced
Chemostat
Used to maintain a microbial population in a particular phase of growth, particularly in log phase by controlling the amount and type of fresh medium added while removing an equal amount of old culture.
