The biological pump concept describes the fate of carbon in the ocean starting from CO2fixation to carbon recycling and sequestration to the ocean bed. Up to 10% of the sequestered CO2 is transported to the deep waters in form of marine snow. Marine snow consists of aggregates composed of plankton cells, detritus, and faecal material all aggregated together and stabilized by a matrix of exopolymeric substances (EPS) released by phytoplankton and bacterial cells.
Phytoplankton-bacteria interactions significantly impact the production of EPS and therefore predictably impact aggregate dynamics, marine snow formation, and ultimately affecting the carbon sink in the ocean. In this context, a better understanding of the molecular cell-to-cell interactions is required.
The model system
In order to further our understanding of the molecular interactions between phytoplanktonic and bacterial cells, an in vitro model system consisting of the diatom Thalassiosira weissflogii and the marine gamma-proteobacterium Marinobacter sp. HP15w has been established in our laboratory.
This bilateral system has attributes that make it promising for genetic manipulation: Both, T.weissflogii and Marinobacter sp. HP15w, are easy to cultivate in the laboratory, considerable genetic background is already available on the diatom, and considerable progress is made towards the genetic and biochemical characterization of the bacteria in our laboratory.
The planned study is directed towards a better understanding of the phytoplankton-bacteria interactions by using the model system.
The project focuses on the:
1. Optimization and technical improvement of the bacterial model system’s genetic accessibility;
2. Investigation of the role of bacterial motility determinants in the initial bacterial attachment to diatom surfaces; and
3. Analysis of the effects of changing environmental conditions on diatom-bacteria interaction with emphasis on temperature changes and ocean acidification.