Going from the bench to the (more complex) field: Study of cultivated macroalgae-degrading bacteria and salt marsh microbial communities


Thursday, September 13, 2012
Redfield Auditorium - 12:00 Noon
Dr. Francois Thomas
Postdoctoral Investigator
Biology Department
Woods Hole Oceanographich Institution

The essential role of microorganisms in biogeochemical cycles can be studied by a variety of laboratory and field-based approaches, either working on pure cultures or natural communities.

During this talk, I will first present results of my doctoral work, focusing on the degradation of algal polysaccharides by the marine bacterium Zobellia galactanivorans. Genomic and transcriptomic analyses revealed that this flavobacterium contains two inducible operons putatively involved in alginate degradation. Several candidate enzymes from these gene clusters were overexpressed in E. coli and their activity characterized, revealing a complete pathway for alginate uptake and assimilation. Comparisons with publicly available bacterial genomes unveiled that such alginolytic operons originated from an ancestral marine flavobacterium and were independently transferred to marine Proteobacteria and some human gut Bacteroides

In the second part of this talk, I will introduce my post-doctoral project at WHOI. I have moved towards the study of natural communities, focusing on sulfur oxidation in salt marshes. The aim is to identify S-oxidizing bacteria living in sediments colonized by the dominant cordgrass Spartina alterniflora and to determine which pathways are involved. We will analyze how environmental parameters (eg. oxygenation, nitrate loadings, etc.) affect the activity of the microbes and eventually the sulfur, nitrogen and carbon cycles.