Week 1/2: Growth in Environment and Lab

Question 1

what is a Winogradsky column?

Answer 1

• 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

Question 2

which do proteins not contain: C, H,O, N, P ,S

Answer 2

not phosphorous

Question 3

what element is not in DNA C, H, O, N, P, S

Answer 3

have phosphodiester bonds (have P) but no sulfer

Question 4

fact: membrane lipids contain C, H, O, P

Question 5

what is haemolysin

Answer 5

produced by pathogens allows them to “steal” Fe from Heme

• pathogens like strep will secrete hemolysin to break RBC to sequester iron

Question 6

why is Rose Bendal Agar selective

Answer 6

Rose bendar and streptomycin in the media select against bacteria and in favour of yeasts/molds

Question 7

what is defined media? give an ex

Answer 7

know exact nature of the nutrients in it - know the exact amounts

BG11 is a defined medium

Question 8

what is the purpose of enrichment

Answer 8

* different then enriched media

• do to alter the microbial diversity, use in lab to isolate underrepresented microbed from complex communities

Question 9

why would you use defined media for a heterotroph like e coli when its easy to culture?

Answer 9

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)

Question 10

Why do photosynthetic and lithotrophic microbes always use defined medium

Answer 10

• they dont require energy from carbon
• would be hard to find lithotrophs on complex media bc overgrown by other heterotrophs

Question 11

what makes N-Free mannitol agar a defined enrichmed media?

Answer 11

• 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

Question 12

What makes BG11 a selective defined medium? what gorwth deos it favour? what makes BG11₀ more selective?

Answer 12

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)

Question 14

define eutrophic

Answer 14

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)

Question 15

what are the major macronutrients that supply major macroelements

Answer 15

C, H, O, N, P, S in g/L amounts

Question 16

what are the minor macronurtients supply minor macroelements

Answer 16

K, Fe in mg/L amounts

Question 17

what are oligotrophs

Answer 17

reuqire very low (major macronutrients) mg/L or even ug/L

ex: marine bacterium pelagibacter ubiqe

Question 18

micronutrients or trace elements are present in what amounts

Answer 18

ug/L

Question 19

what are growth factors

Answer 19

• essential nutrients that may be required
• small organic molecules like aa, purines, pyrimidines, vitamines, required due to evolutionary mutations in biosynthetic pathways

Question 20

what is an example of enriched medium

Answer 20

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

Question 21

what are haemolytic species?

Answer 21

capable of breaking RBC

Question 22

what is enriched media?

Answer 22

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

Question 23

why are organisms that reuqire growth factors almost always heterotrophs?

Answer 23

• they are symbionts/pathogens, especially obligates

Question 24

why use metagenomic DNA?

Answer 24

• 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)

Question 25

what is maconkey agar?

Answer 25

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)

Question 26

purpose of nitrogen free mannitol agar

Answer 26

• selective for organisms like aerobic azotobacter
• must be albe to fix nitrogen gas and use mannitol as sole carbon source

Question 27

what type of media supports growth of fastidious organisms

Answer 27

enriched media

*different than an enrichment culture which fosters growth of an underrepresented microbe