TOPIC 2 + 3: Microbial Growth, Enumeration, and Nutrition Flashcards
how can bacteria be grown in the lab?
liquid culture (batch culture, continuous culture)
semi-solid media (agar, carbohydrate allows it to solidify) –> colony is a clone of a bacteria
what is the formula for binary fission?
X(2^n)
what are the stages of a bacterial growth curve?
Lag phase –> metabolically active, adapting
Log phase –> dividing exponentially
Stationary phase –> plateau, stop dividing, # new = # dying
Death phase –> decline, neative exponential curve
why might cells stop growing?
run out of nutrients
produce toxic byproducts from metabolism
what is a continuous cluture?
all cells in a population achieve a steady state
allows a detailed study of bacterial physiology
chemostat ensures a log growth
adding and removing an equal amount of culture media
GASTROINTESTINAL TRACT
how can plate counts be performed?
spread plate –> sample spread on surface of semi solid media, colonies appear on surface
pour plate –> add sample to molten agar, pour into petri dish and allow to solidify, colonies can be embedded into the media or on surface (note: bacteria must be able to survive 50C. can count anaerobic bacteria)
how can a sample be concentrated?
0.22m filter
describe optical density
LIGHT - SAMPLE - DETECTOR
will detect less light with more bacteria (cloudier)
directly proportional
measured by SPECTROPHOTOMETER
what is a direct method of counting bacteria?
HEMOCYTOMETER
cells/mL > 107 for stat reliability
what is a HEMOCYTOMETER?
microorganisms can be counted directly by placing dilutions on a special microscope slide with grids that hold a known volume of liquid
count the bacteria in the grid
what are biofilms?
surface attached communities
one or multiple species
- attachment monolayer
- micro-colonies
- secret EPS
- mature biofilm
- disillusion and dispersal
what are the macronutrients?
C, O, H –> lipids, carbs, proteins, nucleic acids
N –> proteins and nucleic acids
P –> nucleic acids, phospholipids
S –> some amino acids
SCHNOP
where can microbes get carbon from?
organic sources (heterotrophs)
CO2 (autotrophs)
where can microbes obtain N from?
ammonium or organic nitrogen coumpounds (ex. proteins)
some bacteria produce NITROGENASE, which converts N2 to ammonium (DIAZOTROPHS) –> symbiotic relationship with plant roots
what macro metal ions do microbes need?
potassium, calcium, magnesium, sodium, iron
required for enzymes, electron carriers, membrane stability
what micro metal ions do microbes need?
iron, coalt, manganses, molybdenum, zinc, copper, nickel, chromium, selenium, tungsten
required for some enzymes to function
describe EXXON VALDEZ
spilt 11 million gallons of crude oil in Alaska
hot water spray, high pressure water, skimmers worked to a limited extent
BIOREMEDIATION: use of living organisms to clean up waste
BIOAUGMENTATION: added fertilizers containing nitrogen and phosphorus to enhance growth of organisms
what could impact a microbes ability to be cultured in the lab?
METABOLIC CAPABILITIES
ability to TRANSPORT NUTRIENTS into the cell
what is DEFINED MEDIA?
know precise chemical composition
can calculate concentration of each element
what is COMPLEX media?
exact composition is UNKNOWN
ex. peptone, tryptone, yeast extract, beef extract, soytone
what is ENRICHED media?
used to grow FASTIDIOUS heterotrophs (complex/unknown nutritional requirements)
eg. contains blood, serum
what is the difference between blood and chocolate agar?
RBCs in chocolate agar have already been lysed
what are oligotrophs?
bacteria that prefer low levels of nutrients
what is selective media?
encourages the growth of some organisms, suppresses the growth of others
