How important is prokaryotic photoheterotrophy in ecosystems of the Atlantic Ocean from 40oS to 40oN?
Lead Research Organisation:
University of Warwick
Department Name: Biological Sciences
Abstract
The aim of the proposal is to find out how important photoheterotrophy is in the open ocean - the Earth's largest ecosystem, of profound importance to global biogeochemistry and climate. Photoheterotrophic prokaryotes use light for energy but cannot use carbon dioxide as their sole carbon source and consequently use organic molecules from the environment to satisfy their carbon requirements. Despite considerable advances in the understanding of several photoheterotrophic mechanisms the role of solar radiation in the metabolism of bacterioplankton in the ocean is difficult to assess, although it is already apparent that CO2 fixation by prokaryotic cells may be only a part of the picture. The project proposes to experimentally test and to examine by mathematical modelling a hypothesis that SAR11 alphaproteobacteria and Prochlorococcus cyanobacteria numerically dominate the open ocean because of their photoheterotrophy. Using a combination of laboratory and oceanic cruise experiments the following objectives will be addressed: (i) to determine uptake rates of phosphate and amino acids as a function of light intensity and spectrum by the main planktonic prokaryotic groups, SAR11 and Prochlorococcus, and to relate these rates to cyanobacterial rates of CO2 fixation; (ii) to quantify mesoscale spatial and depth-related variations of group-specific rates of light-enhanced uptake of phosphate and amino acids within the euphotic zone, linking these variations in photoheterotrophy with population sizes and composition of the dominant groups in the North Atlantic subtropical gyre; (iii) to compare photoheterotrophic rates in the North Atlantic gyre with the ones in the Southern gyre and the Equatorial region, using light-enhanced amino acid uptake in order to ascertain the significance of photoheterotrophic use of light at the ocean scale. In order to meet the above objectives we will focus on experimental work in the open Atlantic Ocean combining isotopic tracer nutrient bioassays with flow cytometric sorting of bacterioplankton cells followed by ultra-sensitive radioassaying of cells, cell identification by fluorescence in situ hybridization and nano-scale secondary-ion mass spectrometry in conjunction with molecular identification of prokaryotic cells by halogen in situ hybridisation. Our overarching aim is to establish the input of solar energy into the microbial world of the open ocean beyond that used for CO2 fixation.
Organisations
People |
ORCID iD |
David Scanlan (Principal Investigator) |
Publications
Evans C
(2015)
Photoheterotrophy of bacterioplankton is ubiquitous in the surface oligotrophic ocean
in Progress in Oceanography
Gómez-Pereira PR
(2013)
Comparable light stimulation of organic nutrient uptake by SAR11 and Prochlorococcus in the North Atlantic subtropical gyre.
in The ISME journal
Hartmann M
(2013)
In situ interactions between photosynthetic picoeukaryotes and bacterioplankton in the Atlantic Ocean: evidence for mixotrophy.
in Environmental microbiology reports
Hartmann M
(2014)
Efficient CO2 fixation by surface Prochlorococcus in the Atlantic Ocean.
in The ISME journal
Hartmann M
(2012)
Mixotrophic basis of Atlantic oligotrophic ecosystems
in Proceedings of the National Academy of Sciences
Zubkov MV
(2015)
Dominant oceanic bacteria secure phosphate using a large extracellular buffer.
in Nature communications
Description | We have shown that bacterioplankton that dominate the phosphate depleted regions of the ocean exploit a large extracellular buffer to meet their phosphate requirements. Such a phosphate buffer could be a common feature for the majority of microbial cells. Buffering of vital nutrients explains how bacteria without internal reserves can still secure their growth. |
Exploitation Route | The mechanism underlying this novel extracellular phosphate buffer is unknown and such a mechanism is likely generic among bacteria. The existence of such a buffer has important implications for the elemental stoichiometry of bacterial cells and how such stoichiometry is introduced into marine ecosystem models. If such a buffer is present in microbial pathogens then deciphering the mechanism may open up a novel target for antimicrobials. |
Sectors | Environment,Pharmaceuticals and Medical Biotechnology |
URL | http://nora.nerc.ac.uk/511066/ |
Description | Publications in Internationally recognised journals. Science talks to researchers and the general public |
First Year Of Impact | 2016 |
Sector | Environment |
Impact Types | Societal |