Environmental Microbiology

Michael Leonardo

Research opportunities with Dr. Leonardo are available to students with a variety of academic backgrounds. Currently, biofilm formation is the primary focus in his lab. In nature, biofilms are mixed communities of bacteria and is a common survival strategy of many bacteria.  One key aspect of community development and biofilm formation is cell-cell communication amongst the bacterial community members. Dr. Leonardo’s lab is exploring the interactions of two genera of bacteria that interact because of their overlapping niches: the marine pathogen Vibrio parahaemolyticus and diverse Shewanella species. In V. parahaemolyticus and certain marine species of Shewanella, biofilm formation is controlled by a homologous cell-cell signal transduction pathway (ScrABC). Investigations show a similar signaling ligand (S-signal) is produced by both of these Vibrio and Shewanella signaling systems. Further experiments have shown that cloned scrABC genes of one species can complement null mutations in their homologues from the other. Bio-assays have demonstrated potential cross-talk between both bacteria as well. To determine the impact of this intercellular cross-talk, we will approach this on two fronts, genetically and in vivo. We will be developing a plasmid-borne SCARless system for CRISPR-generated mutations in the S-signal production and response in Shewanella. Gene expression will be monitored by qPCR and other methods. In addition, we will grow biofilms using different combinations of Vibrio and Shewanella strains then use confocal laser-scanning fluorescent microscopy and Surface-enhanced Raman Spectroscopy (SERS) to study the architecture of biofilms. Classic microbiological protocols will be employed to study the interactions between the two genera within the biofilms.

Dr. Leonardo is a member of the Coe College Biology Department mleonard@coe.edu