4. Microbial Nutrition, Measuring Microbial Growth Flashcards
(31 cards)
2 reasons why knowing growth requirements for microbes is important
- To control microbial growth
2. To be able to culture microbe
2 ways microbes can get iron?
Secrete siderophores
Secrete hemolysins (lyse RBCs)
What are siderophores? How does it work?
Low MW molecules that are able to complex with ferric iron and supply it to the cell
Ferric iron in middle of 3 siderophores => bind to siderophore receptor
Once iron has entered a G- bacterium, how can it get into the cytoplasm?
When iron reaches periplasmic space, moves through PM with aid of a TRANSPORTER
Reduced to ferrous form (Fe2+) afterwards
What are growth factors? 3 examples?
Pre-formed organic nutrients
Amino acids, vitamins, nucleic acids
3 types of nutrition microbes need to acquire?
Energy, electrons, carbon
What are the 5 major nutritional types of microorganisms?
Photo-litho-autotrophy
Photo-organo-heterotrophy
Chemo-litho-autotrophy
Chemo-litho-heterotrophy
Chemo-organo-heterotrophy
2 types of energy source trophs
phototroph, chemotroph
2 types of electron source trophs
organotroph, lithotroph
2 types of carbon source trophs
heterotroph, autotroph
Do lithotrophs oxidize or reduce electron donors?
Oxidize them
What is auxotrophy?
Inability to synthesize particular organic compound required for growth
3 major processes of nutrient uptake?
Simple diffusion
Active transport
Facilitated diffusion
2 general types of growth media and their differences?
Complex and synthetic
Complex = undefined
Synthetic = defined
Composition of the 2 types of growth media?
Complex - protein hydrolysate (beef/soy protein), water soluble extract of yeast/beef, separate carbon source(glucose)
Synthetic - only specific amounts of known nutrients
Differences between differential and selective media? Examples?
Differential allows one to distinguish among groups of microbes (blood agar)
Selective favors the growth of a particular type of microbe (eosin methylene blue)
Word for the progeny that arise from a single cell?
Clonal
Species vs strain?
Species - arbitrarily define group of orgs that with high degree of shared characteristics
Strain - isolate; arises from single cell
What is a type strain?
Often one of the first isolates of a species and therefore the best chaacterized.. but not necessarily the most common
4 phases of a bacterial growth curve?
Lag, exponential (log), stationary, death
What is the variable you can determine from a growth curve?
‘g’ (growth) = time it takes for the pop. to double, but ONLY for the exponential phase
What occurs during the stationary phase of a growth curve?
No net change in live biomass (growth/death still occurring)
Growth decrease due to limited nutrients/toxic build-up
We can ONLY calculate ‘g’ during the ____________ phase
exponential (log)
Microbe growth curve is a ______-____ plot
semi-log
