1. The Oceanic Biogeochemical Carbon Cycle
Bacterial adaptations to the ocean
Ecosystem functions of marine microbes:
Bacterial role in how the ocean works as a biogeochemical system
Marine microbes’ influence on global habitability

2. Are microbes important as a biogeochemical force
Are microbes important as a biogeochemical force? Microbes have been profoundly shaping the Earth’s environment “Our” Earth is a microbial planet -- and we as a biogeochemical force are changing their habitats . Will they respond by changing Earth as our habitat?
Madigan, 2008

3. The Age of Discovery 1977 Bacteria 106 mL-1 (103 x cfu)
79/80 High bacterial growth & C demand (dynamic populations)
Protozoa (103 mL-1) major predators on bacteria
Viruses abundant (107 mL-1) & major predators on bacteria
Synechococcus mL-1
Prochlorococcus mL-1
Remarkable widespread Archaea throughout the oceans ( mL-1)
Discovery of anoxygenic photosynthetic bacteria
Rise of molecular ecology
Massive marine genomics and metagenomics-- providing constrains for diversity and ecosystem function. Now, faster sequencing (454--?)
Culturing the “unculturable”
Widespread picoeukaryotes
Discovery of diverse bacteriorhodopsins
Many more: e.g. SO4-reducing methanotrophs; ammonox; Fe-protein-dominated (86%) cellular machinery of Ferroplasma acidiphilum

4. We have been discussing: Bacteria-OM interactions structure marine ecosystems at nm scale- one molecule at a time. But is bacteria-OM coupling at fine (biochemical) scale useful in ocean basin scale C fluxes?
Azam and Malfatti, 2007 Nature Reviews Microbiology 10:782
Swimming stomachs
Significance of spatial coupling
Cell surface hydrolases; x variability in cell-specific activity
High affinity + high capacity permeases
Biodiversity --> Biochemical diversity

5. Biogeochemical integrative view:
How much of the FIXED CARBON does go into:
1) Bacteria?
2) Fish?
3) Bottom sediments?
CO2
CH4
Azam and Malfatti, 2007 Nature Reviews Microbiology 10:782

6. Bacterial Carbon Demand is a Major and Variable Flux Pathway--> variability of biogeochemical state -> Variability in Bact-OM coupling strength:consequences
3H- Thymidine or Leu for µ & BCP
BCD=BCP + R
Modified from Cole et al, 1988 MEPS. 43: 1-10.
* Smith et al, 1995 (mesocosm bloom)
** Pomeroy & Deilbel, 1986 (New Foundland coast)
Turley et al, 1999 (E Med Fc =0.85)
Mesopelagial: >80% C flux-> Bacteria (Cho and Azam, 1988)
Sewage outfalls and aquaculture: Fc >1
Too high Fc may kill corals!
Coupling variability of Bacteria-OM
What causes it? Biochemistry happens!
Will return to this issue; but first: why care?

7. How much into Bacteria, Fish and Sediment?
We are living in a ppm CO2 world (

8. For a few CYCLES more (all IS connected): Carbon Nitrogen Iron Sulfur
Phosphate
Pollutants
Redfield ratio or Redfield stoichiometry is the atomic ratio of carbon, nitrogen and phosphorus found in phytoplankton and throughout the deep oceans C:N:P = 106:16:1 (Redfield A.C. 1934)

9. Carbon transformations in the environment
Figure: 19-23
Caption:
Redox cycle for carbon; note in particular the contrasts between autotrophic (CO2 organic compounds) and heterotrophic processes. Yellow arrows indicate oxidations; red arrows indicate reductions. Photosynthesis in oxic habitats is mainly oxygenic, whereas in anoxic environments it is mainly anoxygenic from the activities of purple and green bacteria. Under anoxic conditions, besides homoacetogens and methanogens, certain sulfate-reducing and nitrate-reducing bacteria are also autotrophic. Methanogens make methane, whereas methanotrophs consume methane.
Madigan 10th edition

10. In the ocean The Solubility Pump The Biological Pump
C fixed mostly by photosynthesis
Locally important C fixation by chemolithotrophs
Munn, 2004

11. The Nitrogen cycle
Figure: 19-29right
Caption:
Redox cycle for nitrogen. Oxidation reactions are represented by yellow arrows and reductions in red.
N is one of the most important growth limiting nutrients for phytoplankton and bacteria
Madigan 10th edition

12. Iron Fluxes in the environment
Low solubility of ferric iron, precipitation as oxide
Acidic environment, food vacuoles of protists
Fe is one of the most important growth limiting micro-nutrients for phytoplankton and bacteria
Cellular respiration (S-Fe protein complex)
HNLC areas, such as Southern Ocean, are Fe limited
Fe fertilization for CO2 sequestration in order to reduce CO2 in the atmosphere
Munn, 2004
Madigan 10th edition

13. Sulfur Cycle Archaea and SRB
Syntrophy: marine microbial consortium that mediates anaerobic oxidation of methane
Sulfur Cycle
Archaea and SRB
Figure: 19-25
Caption:
Anoxic methane oxidation. (a) Methane-oxidizing cell aggregates from marine sediments. The aggregates contain methanogenic bacteria (red) surrounded by sulfate-reducing bacteria (green). Each cell type is stained by a different phylogenetic FISH stain (Section 18.4). (b) Possible mechanism for syntrophic anoxic methane oxidation in the cell aggregates.
Influence on climate in the bacteria-phytoplankton interaction:
DMS (dimethyl sulfide) is a breakdown product from DMSP (dimethylsulfoniopropionate) and also from DMSO (dimethyl sulfoxide).
DMS act as cloud condensation nuclei
DMSP is an osmolyte prodcuded by phytoplankton
Madigan 10th edition and Boetius et al. 2000

14. P-cycling http://jpkc.nwu.edu.cn/
At low Pi bacteria are avid competitors with phytoplankton
At hight Pi the situation is reversed
Explained by biochemistry of flux coupling
Implication for f-ratio for P (eg: Mediterranean Sea)
Ammerman et al MEPS 18:31-39
Ammerman & Azam Science 227:
Paul et al AEM 54:
Thingstad & Rassoulzadagan Prog. Oceanogr.
Azam et el (Aggregation may enhance P-cycling rate)