Microbial Perspective Flashcards
‘Classic’ application of isotopes in ecology
Stable carbon isotopes used in determining the source of primary production responsible for the energy flow in an ecosystem.
what does differences in Carbon 13 between animals indicate?
indicate that they have different food sources or that their food webs are based on different primary producers
Isotope ratios of Biomarkers in Ocean’s uses
Can be used to study organic
matter sources utilised by microorganisms in complex ecosystems and for identifying specific groups of bacteria like methanotrophs
Meta/community approach
stable isotope probing (DNA, RNA, Protein)
Single cell approach
NanoSIMS; FISH-MAR; RAMAN-FISH
what is FISH-MAR?
a technique to combine radio-labeled substrates with conventional FISH to detect phylogenetic groups and metabolic activities simultaneously
Stable isotope probing method
DNA extracted from a M. extorquens grown with 12C- or 13C-methanol as the sole carbon source.
DNA extraction from soil that had utilized 12C- or 13C-methanol, showing the position of the 13C- DNA fraction
Transparent Exopolymer Particles (TEPs)
TEP are polysaccharide gels that are abundant in seawater
Primary source of TEPs
Phytoplankton are the primary source of TEP, with diatoms shown to be major producers
What is Particulate Organic Carbon (POC)?
all combustible, non-carbonate carbon that can be collected on a filter
Carbon suspended in the water (non carbonate)
What % of POC (particulate organic carbon) are TEPs (Transparent Exopolymer Particles)?
TEP can vary between 10-40% of Particulate Organic Carbon (POC)
How big are Transparent Exopolymer Particles and what can they be stained with?
Larger than 0.2 μm and stainable with the dye alcian blue
TEP Formation
STEP 1 - DOC polymers assemble first, forming nanogels that are stabilized by entanglements and Ca bonds
STEP 2 - Entangled networks undergo axial diffusion, allowing polymers to interpenetrate neighbouring nanogels, forming microgels
DOC polymers to Nanogels
assembly
Nanogels to DOC Polymers
dispersion
nanogels to microgels
annealing
microgels to Nanogels
fragmentation
DOC Polymers size
5-50nm
Nanogels size
100-200nm
microgels size
3–6 μm
TEPs major roles in marine ecosystem functioning and Earth system processes
Aggregate formation
Atmospheric aerosol formation
Biofilm development
Nitrogen fixation and transfer in diatom–cyanobacterial symbioses
Nitrogen-fixing cyanobacteria transfer N to diatom
Samples fixed and analysed with NanoSIMS
Bioturbation
the disturbance of sedimentary deposits by living organisms
Bioturbation increase hydrocarbon degradation in sediments by:
Aeration (O2)
Nutrient exchange
Sediment reworking (increasing
availability of substrates to bacteria)
Hydrocarbon degradation in Sediment
Significant hydrocarbon degradation in bioturbated sediments compared to controls
abundance of active bacteria and active eukaryotes in burrows compared to sediments
Higher abundance of active bacteria and active eukaryotes in burrows
Eukaryote community structure
Domination of fungi in all samples
stimulation of bacterivorous protists (e.g. Cercozoa)
stimulation of microfauna (e.g. rotifers)
