Proteomics analysis of the response of the marine bacterium Marinobacter adhaerens HP15 to the diatom Thalassiosira weissflogii

摘要

Bacteria are often associated with diatoms through attachment or by being in close proximity. Certain bacteria-diatom interactions are assumed to be mutualistic. Substrates determining these interactions have been identified, yet in-depth studies on bacteria-diatom interactions remain scarce. In the present study, we applied a proteomics approach to obtain a deeper perspective of the response of a bacterium to a diatom. A bilateral model system was used, comprising the marine γγ-proteobacterium Marinobacter adhaerens HP15 and the diatom Thalassiosira weissflogii. In co-cultivation experiments, the interacting partners were physically separated by dialysis tubing allowing diffusion of compounds. The proteome of M. adhaerens HP15 derived from cell lysates was sampled and compared with protein samples from diatom-free bacterial cultures. Proteome alterations were visualized by 2-dimensional gel electrophoresis, and differentially expressed proteins were analyzed by mass spectrometry. We hypothesizedthat observable protein alterations will give information on substrates that determine a potential mutualistic interaction. Our results suggested a differentiated nutrient supply for M. adhaerens HP15 during co-cultivation. The bacterium seemed to benefit from the release of amino acids by the diatom, as indicated by an up-regulation of several transporter elements responsible for amino acid uptake. To substantiate these results, a screening for suitable nutrient substrates of M. adhaerens was conducted revealing that amino acids appeared to be the preferred carbon source of the bacterium, while various tested sugars were not utilized.