Week 2: Autotrophy and diazotophy (growth in env and lab) Flashcards
whats an autotroph
uses CO2 as carbon source
- assimilatory reduction into organisc and assimilation of organics into biomass
what is diazotrophy
N2 is used as the nitrogen souce
- organism use assimilatory reduction to reduce N2 into organics (DNA, proteins) and assimilation into biomass
*diazotrophy is only characteristic of certain species of bacteria and archea
*treat apparently spread through horizontal gene transfer and operon found in many distantly relaed and not related species
what are Rhizobia
bacteria symbionts of legume roots and can fix nitrogen only in that state
how can you identify ability to fix nitrogen?
locating the operon in genome and that its surrounded by genetic sequences that differ from species to species
describe incorperation/assimilation of nitrogen into cellular structures
- ammoniium NH4+ and nitrate NO3- are common, preferred macronutrient sources for N
- nitrogen fixation from N2 is energetically expensive (diazotrophs dont fix N2 unless they need to bc energy intense process) ie have preferred source of nitrogen but can fix when needed
what inhibits nitrogenase activity?
O2
*nitrogenase is enzyme that conv N2 to NH3
if nitrogenase is inactivated by oxygen why are not all N-fixers anaerobic?
- aerobic diazotrophs create pseudo anaerobic microenvironments aka anaerobiosis
Anabaena (filamentous cyanobacteria) is an oxyenic photosynthetic bacterium, when needs to fix nitrogen forms a heterocyst
- Anoxygenic photosynthesis allows nitrogenase to remain active, shares fixed nitrogen with neighbouring cells while those cells supply additional nutrients to heterocyts
*Also uses temporal regulation to fix nitrogen during the night when no sunlight
- also can use root nodules: plant provides leghaemoglobin oxygen binding protein to amke a nitrogen safe zone and development of “nutrient market”
