Week 1/2: Growth in Environment and Lab Flashcards
what is a Winogradsky column?
- only allows for light and atmospheric gas exchange
- self sustaining so need organisms that are primary producers and other organisms that will feed on those products
- also need microbes to fix nitrogen gas (bc nitrgoen required for all life)
**regardless of organisms abilities, energy sources and tolerances, they all have similar molecular composition and elemental needs/composition
* may just have a perfereed source of where they get said nutrients
which do proteins not contain: C, H,O, N, P ,S
not phosphorous
what element is not in DNA C, H, O, N, P, S
have phosphodiester bonds (have P) but no sulfer
fact: membrane lipids contain C, H, O, P
what is haemolysin
produced by pathogens allows them to “steal” Fe from Heme
- pathogens like strep will secrete hemolysin to break RBC to sequester iron
why is Rose Bendal Agar selective
Rose bendar and streptomycin in the media select against bacteria and in favour of yeasts/molds
what is defined media? give an ex
know exact nature of the nutrients in it - know the exact amounts
BG11 is a defined medium
what is the purpose of enrichment
* different then enriched media
- do to alter the microbial diversity, use in lab to isolate underrepresented microbed from complex communities
why would you use defined media for a heterotroph like e coli when its easy to culture?
so you can do physiological studies
- can determine perferred carbon source, identify range of carbon energy sources a species can use, genetics (look at ability to use a particular energy source and the genes that underly that ability)
Why do photosynthetic and lithotrophic microbes always use defined medium
- they dont require energy from carbon
- would be hard to find lithotrophs on complex media bc overgrown by other heterotrophs
what makes N-Free mannitol agar a defined enrichmed media?
- know everything thats in it
- mannitol cannot be used readily by a lot of heterotrophs, so it favours growth of the oligotroph
- no nitrogen source added so favours microbes that fix nitrogen gas
What makes BG11 a selective defined medium? what gorwth deos it favour? what makes BG110 more selective?
favours growth of photosynthetic cyano bacteria (and algae)
- has oligotrophic concentrations of nutrients and no orgnaic energy/C source (organisms must get energy from light and carbon from CO2)
- BG110 is more selective bc no source of nitrogen, so organisms must be able to fix N2 (diazotrophs)
define eutrophic
rich in nutrients and so supporting a dense plant population, the decomposition of which kills animal life by depriving it of oxygen
- think lakes with too muh plant growth
*these environments contain copiotrophic organisms (organisms found in a nutrient rich environemtn)
what are the major macronutrients that supply major macroelements
C, H, O, N, P, S in g/L amounts
what are the minor macronurtients supply minor macroelements
K, Fe in mg/L amounts
what are oligotrophs
reuqire very low (major macronutrients) mg/L or even ug/L
ex: marine bacterium pelagibacter ubiqe
micronutrients or trace elements are present in what amounts
ug/L
what are growth factors
- essential nutrients that may be required
- small organic molecules like aa, purines, pyrimidines, vitamines, required due to evolutionary mutations in biosynthetic pathways
what is an example of enriched medium
chocolate agar, contains partially haemolyzed blood
*nutrient enrichment is adding a source of growth factors
*blood agar is a differential medium (haemolytic species) and an enriched medium
what are haemolytic species?
capable of breaking RBC
what is enriched media?
supplemented complex media used for “picky eaters” fastidious heterotrophs (requrie complex mixture, or unidetified growth factors)
*different than an enrichment culture - used to increase/select for underrepresented species in a complex sample (mixed culture)
ex: chocolate agar
why are organisms that reuqire growth factors almost always heterotrophs?
- they are symbionts/pathogens, especially obligates
why use metagenomic DNA?
- rRNA profiling from metagenoic DNA provides taxonomic (classification) info on samples
- shot gun sequencing provides metabolic info and even geneome sequencing
*can characterize a microbial community (partial solution to great plate count anaomaly)
what is maconkey agar?
selective and differential media
- isolates gram negative and differentiates based on lactose fermentation
- crystal violet and bile salts prevents growth of gram positive (selective component)
- lactose is differential (those that metabolize change colour)
purpose of nitrogen free mannitol agar
- selective for organisms like aerobic azotobacter
- must be albe to fix nitrogen gas and use mannitol as sole carbon source
what type of media supports growth of fastidious organisms
enriched media
*different than an enrichment culture which fosters growth of an underrepresented microbe
