Brian Hammer, Assistant Professor
Ph.D., Microbiology and Immunology, University of Michigan Medical School, 2001
Office: Cherry Emerson (CE) 223
Microbiology, quorum sensing, regulatory small RNAs, signal transduction, host-pathogen interactions, microbial biofilms
Research in my lab focuses on the bacterial pathogen Vibrio cholerae, a common inhabitant of marine environments and also the causative agent of the fatal diarrheal disease cholera. In particular, we study a process of cell-cell communication called quorum sensing, which is used by V. cholerae and other bacteria to communicate using chemical signaling molecules called autoinducers (AIs). Because the extracellular concentration of the AIs increases as a function of population density, quorum sensing allows bacteria to coordinate gene expression on a population-wide scale and thereby behave like multicellular organisms. In V. cholerae, AI information is funneled internally through a signal transduction circuit that impinges on the transcription of multiple small regulatory RNAs (sRNAs). Using a combination of genetics, bioinformatics, and genomics we have recently identified the molecular mechanism that explains how base-pairing of the sRNAs with target mRNA can both activate as well as repress expression of target genes. Importantly, we revealed that this sRNA signaling pathway is conserved in Vibrios isolated from both clinical and marine settings. The goal of our work is to reveal how quorum sensing enables V. cholerae to adapt to and exploit pathogenic and environmental niches that it inhabits.
Antonova E & BK Hammer. 2011. Inter-species quorum sensing signal molecules promote horizontal gene transfer to Vibrio cholerae in environmental settings. FEMS Micro Lett doi: 10.1111/j.1574-6968.2011.02328.x (in press)
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.
Hammer BK, and Bassler BL 2009 Distinct Sensory Pathways in Vibrio cholerae El Tor and Classical Biotypes Modulate Cyclic Dimeric GMP Levels To Control Biofilm Formation. J Bacteriol 191: 169-177.
Hammer BK & BL Bassler. 2008. Signal integration in the Vibrio harveyi and Vibrio cholerae quorum-sensing circuits, in Chemical Communication among Bacteria, ASM Press. 323-332.
Hammer BK & BL Bassler. 2007. Regulatory small RNAs circumvent the conventional quorum sensing pathway in pandemic Vibrio cholerae. Proc. Natl. Acad. Sci. USA. 104:11145-11149.
Hammer BK & BL Bassler. 2003. Quorum sensing controls biofilm formation in Vibrio cholerae. Mol. Microbiol. 50:101-114.
Hammer BK, ES Tateda & MS Swanson. 2002. A two-component regulator induces the transmission phenotype of stationary phase Legionella pneumophila. Mol. Microbiol. 44:107-118.
Swanson MS & BK Hammer. 2000. Legionella pneumophila pathogenesis: A fateful journey from amoebae to macrophages. Ann. Rev. Microbiol. 54:567-613.
Hammer BK & MS Swanson. 1999. Coordination of Legionella pneumophila virulence with entry into stationary phase by ppGpp. Mol. Microbiol. 33:721-731.