Microbial Perspective

Question 1

‘Classic’ application of isotopes in ecology

Answer 1

Stable carbon isotopes used in determining the source of primary production responsible for the energy flow in an ecosystem.

Question 2

what does differences in Carbon 13 between animals indicate?

Answer 2

indicate that they have different food sources or that their food webs are based on different primary producers

Question 3

Isotope ratios of Biomarkers in Ocean’s uses

Answer 3

Can be used to study organic
matter sources utilised by microorganisms in complex ecosystems and for identifying specific groups of bacteria like methanotrophs

Question 4

Meta/community approach

Answer 4

stable isotope probing (DNA, RNA, Protein)

Question 5

Single cell approach

Answer 5

NanoSIMS; FISH-MAR; RAMAN-FISH

Question 6

what is FISH-MAR?

Answer 6

a technique to combine radio-labeled substrates with conventional FISH to detect phylogenetic groups and metabolic activities simultaneously

Question 7

Stable isotope probing method

Answer 7

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

Question 8

Transparent Exopolymer Particles (TEPs)

Answer 8

TEP are polysaccharide gels that are abundant in seawater

Question 9

Primary source of TEPs

Answer 9

Phytoplankton are the primary source of TEP, with diatoms shown to be major producers

Question 10

What is Particulate Organic Carbon (POC)?

Answer 10

all combustible, non-carbonate carbon that can be collected on a filter

Carbon suspended in the water (non carbonate)

Question 11

What % of POC (particulate organic carbon) are TEPs (Transparent Exopolymer Particles)?

Answer 11

TEP can vary between 10-40% of Particulate Organic Carbon (POC)

Question 12

How big are Transparent Exopolymer Particles and what can they be stained with?

Answer 12

Larger than 0.2 μm and stainable with the dye alcian blue

Question 13

TEP Formation

Answer 13

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

Question 14

DOC polymers to Nanogels

Answer 14

assembly

Question 15

Nanogels to DOC Polymers

Answer 15

dispersion

Question 16

nanogels to microgels

Answer 16

annealing

Question 17

microgels to Nanogels

Answer 17

fragmentation

Question 18

DOC Polymers size

Answer 18

5-50nm

Question 19

Nanogels size

Answer 19

100-200nm

Question 20

microgels size

Answer 20

3–6 μm

Question 21

TEPs major roles in marine ecosystem functioning and Earth system processes

Answer 21

Aggregate formation
Atmospheric aerosol formation
Biofilm development

Question 22

Nitrogen fixation and transfer in diatom–cyanobacterial symbioses

Answer 22

Nitrogen-fixing cyanobacteria transfer N to diatom

Samples fixed and analysed with NanoSIMS

Question 23

Bioturbation

Answer 23

the disturbance of sedimentary deposits by living organisms

Question 24

Bioturbation increase hydrocarbon degradation in sediments by:

Answer 24

Aeration (O2)
Nutrient exchange
Sediment reworking (increasing
availability of substrates to bacteria)

Question 25

Hydrocarbon degradation in Sediment

Answer 25

Significant hydrocarbon degradation in bioturbated sediments compared to controls

Question 26

abundance of active bacteria and active eukaryotes in burrows compared to sediments

Answer 26

Higher abundance of active bacteria and active eukaryotes in burrows

Question 27

Eukaryote community structure

Answer 27

Domination of fungi in all samples
stimulation of bacterivorous protists (e.g. Cercozoa)
stimulation of microfauna (e.g. rotifers)