Microbial Growth Flashcards
what are the essential MACRONUTRIENTS?
carbon, nitrogen, phosphorous, hydrogen, oxygen, sulfur, magnesium ion, iron ion, potassium ion, calcium ion
from: carbohydrates, lipids, nucleic acids, proteins, enzyme cofactors (ions), regulatory molecules (ions)
what are the MICRONUTRIENTS?
cobalt, copper, manganese, molybdenum, nickel, zinc ions
mainly from enzyme cofactors
what are the chemical reactions of METABOLISM?
CATABOLISM = breakdown of molecules, EXERGONIC, ENERGY OUT
ANABOLISM = build molecules, ENDERGONIC, ENERGY IN
catabolism provides energy for anabolism
what percentage of carbon and nitrogen transfer to each level of the pyramid?
10%
what are AUTOTROPHS?
get carbon from inorganic sources and use sunlight to make energy
describe HETEROTROPHS
get carbon and electrons from organic sources
what are CHEMOTROPHS?
get energy from chemical compounds and inorganic compounds
describe the NITROGEN CYCLE
need N for amino acids and nucleic acids
nitrogen fixers have enzyme NITROGENASE, converts N2 to NH4+
ex. Rhizobium bacterial species
describe the microbial GROWTH CYCLE
most divide by BINARY FISSION –> cell increases in size/cell volume and splits into two equal daughter cells
Population DOUBLES after each division
yeast and some bacteria divide by ASYMMETRICAL BUDDING
what is GENERATION TIME
time it takes for a population to DOUBLE
in an OPTIMAL ENVIRONMENT, bacteria divides at a constant rate
Nt = N0 x 2^n
some organisms generate and secrete compounds that are TOXIC to themselves, slowing growth
what are the fastest and slowest bacterial generation times?
clostridium perfringens: ~10 mins
Mycobacterium leprae: ~14 days (due to cell wall)
how do we MEASURE GROWTH of microbes?
PURE CULTURE (<1% of microbes are culturable)
can understand microbes better than we can in complex environments
use OPTIMAL nutrient and environmental conditions
why is it important to understand NUTRIENT REQUIREMENTS?
CHARACTERIZATION of microbes
OPTIMIZED USAGE of beneficial microbes (ex. mass producing pharmaceuticals)
INCREASED UNDERSTANDING of PATHOGENIC microbes
why can we not CULTURE MORE microbes?
do not know how to grow in lab
depend on OTHER SPECIES in NICHE
evolved to live INSIDE OTHER CELLS
OBLIGATELY SYMBIOTIC - cannot grow without partners
what are the main forms of CULTURE MEDIA?
LIQUID/BROTH: cells held in SUSPENSION –> study in pure culture, obtain LARGE NUMBER of cells & extracellular products
SOLID MEDIA/AGAR: cells grow as COLONY FORMING UNITS –> SEPARATE bacteria, ISOLATE pure culture, study DIVERSITY and TRAITS of a sample
what is COMPLEX/RICH media
nutrient rich, composition poorly defined, do not know exact concentrations
what is MINIMAL DEFINED media
contain only ESSENTIAL nutrients, concentrations known
what is ENRICHED media
specific factors that the microbe cannot produce are ADDED (ex. blood proteins, nucleotides, vitamins///0
what is SELECTIVE media?
FAVOUR the growth of ONE organism over another (pH, specific nutrients)
what is DIFFERENTIAL media?
exploits BIOCHEMICAL/PHYSIOLOGICAL differences between TWO SPECIES that grow equally well in a medium
ex. miconchi agar changes colour for gram +/-
how are pure cultures ISOLATED?
DILUTION STREAKING and SPREAD PLATING
used to establish PURE CULTURES or estimate NUMBER of bacteria
assume ONE CELL = ONE COLONY
describe DILUTION STREAKING
work ASEPTICALLY
STERILIZED LOOP picks up small amount of sample
DRAG loop across surface of agar plate
FLAME loop
TOUCH END to LAST streak, repeat streaking
millions of cell divisions produce visible colonies
describe SPREAD PLATES
set up 10 fold serial dilution
plate 0.1mL (100 microlitres)
analyze plates with ~30-300 CFUs
how is bacteria COUNTED
must be SUSPENDED in liquid
1. direct microscopic counts via HAEMOCYTOMETRY
2. PLATE counts
3. OPTICAL DENSITY using spectrophotometer
what is OPTICAL DENSITY?
higher cell concentration = higher TURBIDITY (cloudiness of liquid)
measured as LIGHT SCATTERED by suspension
higher reading = denser cell culture
amount of diffraction is a function of density (NOT a cell count)
what is the microbial GROWTH CYCLE?
measure of cell DENSITY/COUNTS over TIME
what is the LAG PHASE?
bacteria ADAPTS to new growth conditions
bacteria MATURES and cannot divide
SYNTHESIS of RNA and ENZYMES
what is the EXPONENTIAL/LOGARITHMIC phase?
EARLY: cells grow at MAX rate
LATE: SLOWING of growth due to density, competition, waste accumulation
what is the STATIONARY PHASE?
population PLATEAUS due to GROWTH LIMITING FACTORS
cells are still ALIVE and METABOLICALLY ACTIVE
what is the DEATH phase?
cells DIE due to NUTRIENT DEPLETION and the production of TOXIC BYPRODUCTS
what is CHEMOSTAT?
ensures CONTINUOUS logarithmic growth by ADDING and REMOVING equal amounts of CULTURE medium
growth conditions are HIGHLY CONTROLLED
allows study of NATURAL CONDITIONS
