180
production supporting wild fisheries. Some pilot experiments have already been
undertaken.
Marine diazotrophy may also play a role in biotechnology including marine
aquaculture. Novel thermophilic diazotrophs have been isolated from deep hot vent
environments and could be exploited to engineer more efficient biological systems
for producing nitrogenous fertilizers to replace the energy intensive Haber-Bosch
process. Marine aquaculture (or mariculture) is rapidly expanding globally as the
demands for protein from the sea continues to increase as many wild fisheries
simultaneously decline. Marine macroalgae which are already raised in farms
worldwide provide important chemical feedstocks such as carrageenan for the food
industry or for the conversion of its biomass to biofuels. Mariculture systems require
large nutrient subsidies, and it seems logical to consider marine diazotrophs as a
potential source of N in their future development. Indeed, macroalgae are already
known to harbor diverse microbial associations including diazotrophs. Multi-trophic
mariculture systems are actively under development. Finally, recent results from
studies in the wake of the massive Deep Water Horizon oil discharge in 2000 have
found globally distributed hydrocarbon degrading diazotrophs in coast sediments
exposed to petroleum hydrocarbons. A gamma proteobacterium has been isolated
and genetically characterized and such organisms may be exploited to facilitate
cleanup in the aftermath of future accidental oil discharges.
10.10 Over-Arching Questions, Controversies and Future
Directions
Microbiological
• What is the relative importance of the different groups of diazotroph groups both
within particular ecosystems and at the global scale?
• Is heterotrophic N 2 fixation significant relative to other inputs and that from cyanobacterial diazotrophs in the surface ocean?
• Are there as yet undiscovered or unstudied diazotrophs such as diatom, lucinid
clam and deep coral symbionts and do they make significant contributions to
their associations or at larger scales?
• Are there other deep sea environments, such as the hot vents that host significant
diazotrophic populations?
Physiological
• How do Trichodesmium and UCYN-A avoid O 2 inhibition?
• How does UCYN-A protect its nitrogenase allowing it to fix in the light?
10 Summary and Conclusions
production supporting wild fisheries. Some pilot experiments have already been
undertaken.
Marine diazotrophy may also play a role in biotechnology including marine
aquaculture. Novel thermophilic diazotrophs have been isolated from deep hot vent
environments and could be exploited to engineer more efficient biological systems
for producing nitrogenous fertilizers to replace the energy intensive Haber-Bosch
process. Marine aquaculture (or mariculture) is rapidly expanding globally as the
demands for protein from the sea continues to increase as many wild fisheries
simultaneously decline. Marine macroalgae which are already raised in farms
worldwide provide important chemical feedstocks such as carrageenan for the food
industry or for the conversion of its biomass to biofuels. Mariculture systems require
large nutrient subsidies, and it seems logical to consider marine diazotrophs as a
potential source of N in their future development. Indeed, macroalgae are already
known to harbor diverse microbial associations including diazotrophs. Multi-trophic
mariculture systems are actively under development. Finally, recent results from
studies in the wake of the massive Deep Water Horizon oil discharge in 2000 have
found globally distributed hydrocarbon degrading diazotrophs in coast sediments
exposed to petroleum hydrocarbons. A gamma proteobacterium has been isolated
and genetically characterized and such organisms may be exploited to facilitate
cleanup in the aftermath of future accidental oil discharges.
10.10 Over-Arching Questions, Controversies and Future
Directions
Microbiological
• What is the relative importance of the different groups of diazotroph groups both
within particular ecosystems and at the global scale?
• Is heterotrophic N 2 fixation significant relative to other inputs and that from cyanobacterial diazotrophs in the surface ocean?
• Are there as yet undiscovered or unstudied diazotrophs such as diatom, lucinid
clam and deep coral symbionts and do they make significant contributions to
their associations or at larger scales?
• Are there other deep sea environments, such as the hot vents that host significant
diazotrophic populations?
Physiological
• How do Trichodesmium and UCYN-A avoid O 2 inhibition?
• How does UCYN-A protect its nitrogenase allowing it to fix in the light?
10 Summary and Conclusions