Molecular Microbiology
 Ece Karatan
Assistant Professor
Ph.D.
University of Illinois at Urbana-Champaign
For more information, please see My Webpage.
Bacteria are incredibly versatile in the number of strategies that they utilize to deal with the changing conditions in their environments. I am mainly interested in studying how bacteria use these strategies to sense and respond to their environments. What signals do they respond to? Which signal transduction networks are responsible for sensing and processing the various types of signals? What are the physiological, behavioral and gene expression changes that occur as a result of these signals? We are asking these questions in the context of biofilm development by the aquatic bacterium Vibrio cholerae . Biofilms are surface-attached microbial communities encased in a self-made polysaccharide matrix. Biofilm formation has been implicated to play role in the survival of V. cholerae in its natural habitats. Thus, studying how this behavior is regulated should yield insights into the physiology and ecology of this organism.
In my lab, we are trying to elucidate the signaling mechanisms that regulate biofilm formation in V. cholerae . We are particularly interested in effect of polyamines such as norspermidine on biofilm development. My previous work has shown that exogenous norspermidine increases biofilm formation and expression of the vps genes, which are responsible for exopolysaccharide production, and that this response is dependent on the presence of a putative periplasmic sensor protein, NspS. We have evidence that a signaling system composed of NspS and MbaA, a putative integral membrane protein encoded by a gene adjacent to nspS , work together to regulate biofilm formation. MbaA, a member of the ever growing GGDEF/EAL protein family, is likely to be a phosphodiesterase which hydrolyzes the novel secondary messenger cyclic-di-guanosine monophosphate (c-di-GMP). We are interested in understanding how this system works. We are asking the following questions: How does norspermidine exerts its effect at the molecular level, does it regulate the proposed enzymatic activity of MbaA, do NspS and MbaA interact and if so, is this interaction mediated and/or affected by norspermidine, does norspermidine affect c-di-GMP levels in the cell, what is the source norspermidine, can it be an intercellular signaling molecule? To answer these questions we are utilizing a variety of molecular, genetic and biochemical techniques including biofilm assays, immunoprecipitation, enzyme assays, site-directed mutagenesis, reporter gene fusions, fluorescence microscopy and microarrays.
Fluorescent micrographs of wild-type and mutant Vibrio cholerae biofilms
Selected Publications:
Karatan E ., Duncan, T., Watnick PI. NspS, a predicted polyamine sensor, mediates activation of Vibrio cholerae biofilm formation by norspermidine (In press in Journal of Bacteriology )
Kierek-Pearson K. and Karatan E . Biofilm Development in Bacteria. 2005. Advances in Applied Microbiology , Laskin, AI., Bennett, JW., and Gadd, MG. (Ed) Elsevier Inc. Vol. 57 pp. 79-112
Kapfhammer D ., Karatan E . , Pflughoeft K.J ., Watnick P.I . 2005. Role for glycine betaine transport in Vibrio cholerae osmoadaptation and biofilm formation within microbial communities. Appl. Environ. Microbiol. Jul;71(7):3840-7.
Karatan E ., Merguerian M., Han Z., Scholle MD., Koide S., Kay BK. 2004. Molecular Recognition Properties of FN3 Monobodies that Bind the Src SH3 Domain. Chem. Biol. Jun;11(6):835-44
Karatan E., Han Z., and Kay BK. Molecular Display Technologies. 2004. Chapter contribution for Encyclopedia of Molecular Cell Biology and Molecular Medicine Meyers, RA. (Ed.) WILEY-VCH (In press)
Karatan E ., Saulmon M.M., Bunn MW., Ordal G.W. 2001. Phosphorylation of CheV is Involved in Adaptation to Excitatory Signals in Bacillus subtilis Chemotaxis J. Biol. Chem . Nov. 23; 276 (47): 43618-43626
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