Topic 5 -Microbial Growth Flashcards
List the requirements for microbial growth
Physical:
Temperature, pH, osmotic pressure
Chemical:
NCHOPS totally organic
Nitrogen, Carbon, Hydrogen, Oxygen, Phosphorous, Sulphur
Trace elements (e.g. vitamins)
Organic growth factors (e.g. Fe, Mg, Cu, Zn, Co)
A little bit about pH and microbes?
bacteria grow b/w pH 6.5-7.5 Moulds & yeast grow b/w 5 - 6 pH controlled by buffers Acidophiles Alkaliphiles
Explain the importance of osmotic pressure to growth
Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
Hypertonic enviro’s cause plasmolysis (inside of cell shrinks)
Use of Nitrogen (N) in growth?
amino acids, proteins, DNA, RNA
Use of Carbon (C) in growth?
carbohydrates, lipids, aa, DNA, RNA. Carbon for cata/anabolism.
Use of Hydrogen (H) in growth?
counter ion e.g. -OH & -COOH. Used as proton source for chemiosmotic formation of ATP
Use of Oxygen (O) in growth?
found in most organic molecules e.g. glucose.
electron acceptor
Use of Phosphorous/phosphate (P/Pi) in growth?
found as phosphate
ATP, NADP, DNA & RNA
Use of Sulfur (S) in growth?
needed for aa cysteine and methionine & co factors
What is the role of trace element Fe?
Iron.
needed for cytochromes in electron transport
What is the role of Trace element Mg?
Magnesium
Counter iron for nucleotides and ATP
What is the role of trace element Zn, Co, Cu & Mo?
Zinc, Cobalt, Copper, Molybdenum.
Enzyme cofactors
How do aerobes avoid damage from O2?
Enzymes. singlet oxygen=> boosts O2 to higher energy state then to superoxide free radicals Then to peroxide anion then to hydroxyl radical
Describe the visual growth of an obilgate aerobe?
all near top of tube where high [] of O2.
See diagram. pg 4
Describe visual growth of facultative anaerobes?
more [] near top of tube but spread throughout tube.
describe visual growth of obligate anaerobes?
all at bottom of tube where very low to no O2
describe visual growth of aerotolerant anaerobes?
spread throughout tube
describe visual growth of microaerophiles?
very sensitive, need exact right conditions. Found in strip through middle of tube or to particular needs.
Explain the purpose of organic growth factors
organic compounds obtained from the enviro.
e.g. vitamins, aa, purines, pyrimidines
many bacteria do not require these
some microorganisms absolutely require a particular GF
What is a culture medium?
nutrients prepared for microbial growth
what does sterile mean?
contains no living organisms
what is inoculum?
microbes introduced into medium
what is a culture?
microbes growing in/on a culture medium
what is a pure culture?
contains only one species or strain
what is a colony?
population of cells arising from a single cell or spore or group of attached cells
what is a colony forming unit (CFU)?
number of living cells in a sample that will grow, divide & form colonies on solid media
what is a chemically defined media for bacterial growth?
exact chemical composition known. Microbes make all nutrients themselves, uses a lot of energy, takes longer to grow
what is a complex media for bacterial growth?
e.g. beef extract and peptone (no defined chemical composition)
Nutrients provided, faster growth
How can single colonies be isolated?
streak plate method
List the different kinds of bacterial growth (repro)
binary fission
budding
fragmentation of filaments
conidiospores (asexual)
Name & describe the 4 different bacterial growth phases
- lag phase -little cell division occuring
- exponential (log) phase -growth phase
- stationary phase -bacterial death=bacterial division
- death phase -cell lysis occurs
List 4 ways of measuring cell growth
Plate count
membrane filtration
direct count under microscope
turbidity
List the 5 main groups of microbes classified according to their temp. range of growth, and what temp they grow at.
Psychrophiles -10 - 20C Psychotrophs 0-30C Mesophiles 10-50C Thermophiles 40-70C Hyperthermophiles 65-110C
