Brian Hammer, Assistant Professor
Ph.D., Microbiology and Immunology, University of Michigan Medical School, 2001
Office: Cherry Emerson 223
Microbiology, quorum sensing, regulatory small RNAs, signal transduction, host-pathogen interactions, microbial biofilms
The bacterium Vibrio cholera causes ~3 million annual cases of the fatal diarrheal disease cholera worldwide, with the largest outbreak in recent times occurring after the 2010 Haiti earthquake. There is intense interest in understanding the origin of cholera epidemics because people that consume contaminated water are a transient source of the pathogen; however, this microbe is also a ubiquitous marine inhabitant that forms biofilms on chitinous surfaces like zooplankton. The pathogenesis and ecology of V. cholera are the primary focus of research in the Hammer lab. V. cholera is a model organism for studying quorum sensing (QS), which allows bacteria to control gene expression in response to self-produced signal molecules (autoinducers, AIs) that accumulate with increased cell density. We are defining how AI accumulation controls expression of genes for biofilm formation and production of a DNA uptake apparatus that promotes horizontal gene transfer (HGT). This work is being conducted in historical references strains, as well as in isolates obtained from Haiti and other clinical and environmental settings. We are discovering components of a nucleoside scavenging system we identified that is integrated into a regulatory network with QS for HGT. We are dissecting the mechanisms by which four QS-controlled regulatory small RNAs directly base-pair with multiple mRNAs for factors important in both marine and host associations. Finally, we are exploiting our understanding of AI-based regulation to engineer synthetic E. coli QS circuits for understanding principles of chemical signaling. In the Hammer lab we use genetic, genomic, biochemical, and computational methods to engage in cross disciplinary research with colleagues from within Georgia Tech and the larger scientific community.
Zhao X, Koestler BJ, Waters CW & Hammer BK. 2013. Post-transcriptional activation of a diguanylate cyclase by quorum sensing small RNAs promotes biofilm formation in Vibrio cholerae. Mol Microbiol. (in press).
Sun YU, Bernardy EE, Hammer BK, Miyashiro TI. 2013. Competence and Natural Transformation in Vibrios. Mol Microbiol. (in press)
Krishnaswamy B , Henegar CM, Bardill JP, Russakow D, Holst GL, Hammer BK, Forest CR & Sivakumar R. 2013. When Bacteria Talk: Time Elapse Communication for Super-Slow Networks, Proceedings of the Institute of Electrical and Electronics Engineers (IEEE) International Conference on Communications (ICC) 2013 - Wireless Networking Symposium (ICC'13 WN), Budapest, Hungary.
Katz LS, Petkau A, Beaulaurier J, Tyler S, Antonova ES, Turnsek M, Guo Y, Wang S, Paxinos E, Orata F, Gladney L, Stroika S, Folster J, Rowe L, Freeman M, Knox N, Frace M, Boncy J, Hammer BK, Boucher Y, Bashir A, Hanage WP, Van Domselaar G, Tarr CL. 2013. Evolutionary dynamics of Vibrio cholerae following a single source introduction to Haiti. mBio. 4(4):1-10.
Bardill JP & Hammer BK. 2012. Non-coding sRNAs regulate virulence in the bacterial pathogen Vibrio cholerae RNA Biology. 9(4): 392-401.
Antonova E, Bernardy E & Hammer BK. 2012. Natural competence in Vibrio cholerae is controlled by a nucleoside scavenging response that requires CytR-dependent anti-activation. Mol. Microbiol. 86: 1215-1231.
Akyildiz IF, Fekri F, Sivakumar R, Forest CR & Hammer BK. 2012. MONACO: Fundamentals of Molecular Nano-Communication Networks. IEEE Wireless Commun. 19(5): 12-18.
Antonova E & Hammer BK. 2011. Quorum-sensing autoinducer molecules produced by members of a multispecies biofilm promote horizontal gene transfer to Vibrio cholerae. FEMS Micro Lett. 322: 68-76.
Bardill JP, Zhao X & BK Hammer. 2011. The Vibrio cholerae quorum sensing response is mediated by Hfq-dependent sRNA/mRNA base pairing interactions. Mol Microbiol. 80:1381-1394.
Hammer BK & SL Svenningsen. 2011. Small RNA target genes and regulatory connections in the Vibrio cholerae quorum sensing system. Methods Mol Biol. 692: 189-206.