W6 Environmental Microbiology Flashcards
why are microbial systems so amenable to ecology
large populations size
short generation time
genetic manipulation
readily sampled
experimentally tractable
different modes of genetic inheritance
what are hopanoids
lipids found in cell membranes
play a role in membrane fluidity, stress and protein localisation
more stable than dna, ran and proteins > used as biomarkers in fossils
do not contain sequence information > harder to identify
what are sulfidogens
microbes that produce H2S
eg: desulfovibrio
what are the two enzyme complexes needed for nitrogen fixation
dinitrogenase and dinitrogenase reductase
properties of heterocysts for nitrogen fixation
thickened cell walls to reduce cell permeability
no chlorophyll > no photosynthesis
reduced nitrogen is transported from heterocyst to vegetative cells
sugars supplied in excess so they leak out of the cell > attracts heterotrophic bacteria that consumes both oxygen and sugars reducing O
process of heterocyst spacing
activator of heterocyst formation, HetR is expressed under nitrogen starvation > RGSGR pentapeptide promotes HetR decay > inhibit heterocyst formation > RGSGR pentapeptide diffuses away from source cells to neighbouring cells > establish inhibitor concentration gradient along filament > promote inverse gradient of activator
what is mycorrihizae
the symbiotic system formed between plant roots and fungi
symbiosis formed primarily for nutrient exchange
two types: VAM arbuscular mycorrhizae (inside plant root) and ectomycorrhizae (outside plant root)
benefits of mycorrhizal
improved transplant survival and growth
more effective rooting
improved soil structure
increased fertiliser utilisation
decreased drought stress
tolerance of environmental extremes
reduces off-site pollution of surface and groundwater
disease reduction
possible mechanisms of reduction of infection by root pathogens by mycorrhizae
production of antibiotics by fungi symbionts
mechanical barrier created by fungi mantle
chemical exudation of mycorrhizae
protective microbial rhizosphere populations
what type of cell do cyanobacteria use fro nitrogen fixation
heterocysts
