Importance of biofilms in environmental mercury methylation and persistence of enteric bacteria ...

Title: Importance of biofilms in environmental mercury methylation and
persistence of enteric bacteria in beach sandSpeaker:
Dr. Jennifer Jay,
UCLAAbstract:Microbial research has undergone a significant shift over the last decade, as we now recognize that the majority of bacteria in the environment live in attached communities, or biofilms. This talk concerns the role of biofilms in two research areas relevant to public health: I. The cycling of mercury (Hg) in the environment. In aquatic systems, inorganic Hg is microbially transformed to methylmercury, a very toxic form of Hg(II) that is readily biomagnified through food webs. While it is known that microbial uptake of Hg by planktonic cultures is influenced by the extracellular speciation of Hg in aquatic systems, Hg uptake in biofilm cultures is understudied. Working first with Escherichia coli O55 as a model gram-negative biofilm-forming organism, and then with two coastal wetland isolates of Desulfovibrio desulfuricans, we found that the presence of a biofilm does not alter the relative availability of the dominant Hg species in both sulfidic and oxic conditions. Interestingly, we observed much higher Hg methylation rates in biofilm cultures compared to planktonic cultures. Results on the geochemical controls on Hg methylation at our coastal wetland field site and in wetland mesocosms will also be presented. II. The persistence of enteric bacteria in sediments. Biofilms also play an important role in the survival of enteric bacteria in beach environments. We observed very high levels of fecal indicator bacteria (FIB) in sediments at enclosed beaches, and both field and laboratory microcosm results support the hypothesis that the quiescent environment rather than sediment characteristics can explain the elevated sediment FIB levels observed at enclosed beaches.

Location: Kaprielian Hall (KAP) - rielian Hall, Room 203

Audiences: Everyone Is Invited

Contact: Evangeline Reyes