Changes in diversity and gene expression of marine bacterial communities under experimental hydrocarbon pollution

LANFRANCONI, M.P.; CAPO, V.; BOSCH, R.; NOGALES, B.

Palma de Mallorca (ESPAÑA)

Workshop; Workshop on Metabolomics and Environmental Biotechnology; 2008

Metagenomics has greatly advanced our understanding of the ecology and diversity of microbiol communities in the ocean. However, many questions concerning regulation and dynamics of genes in the environment remain unanswered. Furthermore, the information regarding the physiological responses of marine microbial communities under stress conditions in the environment is scarce. To evaluate the impact of diesel pollution on bacterial communities we proposed to study changes in diversity and the expression of relevant genes by carrying out laboratory microcosms experiments, which were prepared with 45 L of unpolluted surface water from Western Mediterranean Sea. With this approach we expected to reduce the influence of uncontrollable environmental variables that we encountered in our previous studies in situ. In diesel-treated microcosms we observed an increase in the number of prokaryotic cells, a higher bacterial activity, and changes in the bacterial community structure. We also detected a negative effect of diesel on picocyanobacteria (Synechococcus) microscopic counts. A decrease in the expression of genes involved in oxygenic photosynthesis (rbcLIA and psbA) was also observed, as evidenced by lower amplification signal in mRNA RT-PCR analysis when compared to control microcosms. However, regarding aerobic anoxygenic photosynthesis, no changes in bchL/bchX expression were observed between diesel-treated and control microcosms. Comparison of clone sequences from cDNA libraries with reference sequences in databases was performed to analyze diversity of gene transcripts. Our results will help to understand which physiological pathways are turned on (or off) under a stress condition like hydrocarbon pollution and which microorganisms are involved in different key processes.