Project 9: Characterization of the role of bacteria on photo-trophic bio-film formation

This project is based at the University of Konstanz in Germany. Research has shown previously that bacteria or substances secreted by bacteria can have a strong impact on diatom growth, attachment and carbohydrate secretion. Therefore, this project is aimed at characterising the organismic syntrophic interactions as well as bio-chemically signalling processes in photo-autotrophic bio-films and more specifically the role of bacteria for induction of diatom growth, movement, carbohydrate secretion and bio-film formation.

Researchers at Konstanz have been able to isolate a larger number of benthic fresh water diatom strains (about 50) and the respective satellite bacteria and identified a limited number of diatom and bacterial model partners that show clear phenotypes of interaction. They have also established in the lab a protocol for disruption of bacterial genes of the satellite bacteria by transposon tagging resulting in mutated bacteria as well as bioassays for easy screening of diatom growth and carbohydrate secretion. This will enable screening for bacterial mutants that are unable to induce the described effects in the diatoms and will allow us to identify the bacterial genes involved. This approach is highly complementary to  project 7, although our project is not trying to identify signalling molecules directly, but rather bacterial genes and pathways involved in the production of signalling molecules. After identification of individual tagged genes we will complement the respective bacterial mutants with the wild type alleles in order to verify our results.

project-9

Biofilm formation will be monitored automatically in biofilm growth chambers further developed in collaboration with LimCo. Ultimately, our objective will be to identify bacterial pathways that increase the productivity and growth rate of diatoms as well as those that affect the attachment and biofilm formation of the diatoms. These mutants will be studied by metabolomics in order to identify changes of metabolic substances. After characterisation of these substances we will use the respective artificially synthesized substances to modify the performance of the diatoms in axenic cultures without the necessity to add bacteria. A strong collaboration- enabled by the bioinformatic platform (WP5)-is underway with ESR 7 on diatom/bacteria quorum sensing, with ESR 2 on interactions between diatoms and lytic bacteria and with ESR 12 on algal/Marinobacter interactions.

Lachlan Dow has been appointed to this project at Konstanz and his research will aim to:

  • Identify of bacterial genes and pathways involved in diatom biofilm induction;
  • Complement and verify the role of genes knocked out by transposon tagging; and
  • Test identified compounds for effects on biofilm formation by diatoms and development of antifouling products.