Karen Visick, PhD


Ph.D., University of Washington
Microbial Geneticist

Major Research Interests: Vibrio fischeri-squid mutualism: a model for investigating biofilm formation in an animal host

Bacteria can form multi-cellular communities, or biofilms, in which individual cells are protected from environmental insults such as antibiotics by virtue of being (1) encased in a protective matrix comprised of polysaccharides and other macromolecules and (2) physiologically distinct from free-living, planktonic cells. Furthermore, biofilm formation enhances the ability of bacteria to colonize surfaces, including host tissues and abiotic surfaces such as medical implants. As a result of these characteristics, bacteria in biofilms are believed to be responsible for the majority of hospital-acquired infections. Due to their medical relevance, how biofilms form and how bacteria naturally disperse from such biofilms is being intensively studied. Although numerous animal models of biofilm formation have been developed, few robustly demonstrate that mechanisms of biofilm formation uncovered in culture reflect what actually occurs in nature.

One such robust model, however, can be found in the Vibrio fischeri - squid (Euprymna scolopes) symbiosis. To colonize, V. fischeri first forms a biofilm-like aggregate on the surface of the symbiotic organ, then disperses from the aggregate to enter and ultimately colonize sites deep within the organ. Our work has shown that genes required for biofilm formation in laboratory culture are similarly required for symbiotic aggregation and colonization. Furthermore, genetic conditions that enhance biofilm formation in laboratory culture also strikingly enhance symbiotic biofilm formation and colonization. This strong correlation affords us an exceptional opportunity to develop and test hypotheses about the mechanisms of biofilm formation and dispersal in bacterial colonization of a eukaryotic host.

We have previously determined that biofilm formation and colonization depends on syp, an 18-gene locus involved in the production and export of a polysaccharide, and on regulators that control syp transcription. Our work continues to probe control over syp-dependent biofilm formation. Recently, we determined that V. fischeri exerts considerable post-transcriptional control over the activities of specific Syp proteins, and this is an area of on-going work. We are also investigating the roles of genes, other than syp, that contribute to biofilm formation. These areas of our work provide insights into the varied mechanisms by which bacteria control biofilms both positively and negatively in the context of an animal host.

Ray, V. A., Driks, A., and K. L. Visick. 2015. Identification of a novel matrix protein that promotes biofilm maturation in Vibrio fischeri. J. Bacteriol. 197:518-28. PMCID: PMC4285995

Norsworthy, A. N. and K. L. Visick. 2015. Signaling between two interacting sensor kinases promotes biofilms and colonization by a bacterial symbiont. Mol Microbiol. 96: 233-248. doi: 10.1111/mmi.12932. PMCID: PMC4465548

Thompson, C. M., and K. L. Visick. 2015. Assessing the function of STAS domain protein SypA in Vibrio fischeri using a comparative analysis. Front. Microbiol. 6:760. doi: 10.3389/fmicb.2015.00760 PMCID: PMC4517449

Morris, A. R., and K. L. Visick. 2013. The response regulator SypE controls biofilm formation and colonization through phosphorylation of the syp-encoded regulator SypA in Vibrio fischeri. Mol Microbiol 87:509-525.

Stabb, E. V., and K. L. Visick. 2013. Vibrio fischeri:  a bioluminescent light-organ symbiont of the bobtail squid Euprymna scolopes, p. 497-532. In E. Rosenberg (ed in chief), E. F. DeLong, E. Stackebrandt, S. Lory, and F. Thompson (ed.), The Prokaryotes, 4th ed. Springer-Verlag Berlin Heidelberg.

Ray, V. A., J. L. Eddy, E. A. Hussa, M. Misale, and K. L. Visick. 2013. The syp enhancer sequence plays a key role in transcriptional activation by the σ54-dependent response regulator SypG and in biofilm formation and host colonization by Vibrio fischeri. J. Bacteriol. 195: 5402-12. PMCID: PMC3837961

Shibata, S., E. S. Yip, K. P. Quirke, J. M. Ondrey, and K. L. Visick. 2012. Roles of the structural symbiosis polysaccharide (syp) genes in host colonization, biofilm formation and polysaccharide biosynthesis in Vibrio fischeri. J Bacteriol 194:6736-6747.

Shibata, S., and K. L. Visick. 2012. The sensor kinase RscS induces the production of antigenically-distinct outer membrane vesicles that depend on the symbiosis polysaccharide locus in Vibriofischeri. J Bacteriol. 194:185-194.

Ray, V. A. & K. L. Visick. 2012.  LuxU connects quorum sensing to biofilm formation in Vibriofischeri. Mol Microbiol 86: 954-970.

Ray, V. A., A. R. Morris and K. L. Visick. 2012. A semi-quantitative approach to assess biofilm formation using wrinkled colony development. J Vis Exp. 64:e4035.* 
*Open access publication funded by a grant from Zeiss.

Ray, V. A. & K. L. Visick, (2012) Two-component regulators in the Vibrio fischeri-Euprymna scolopes symbiosis. In: Two-component systems in bacteria. R. Gross & D. Beier (eds). Norfolk, UK: Caister Academic Press, pp. 371-404.

Morris, A. R., C. L. Darnell, and K. L. Visick. 2011. Inactivation of a novel response regulator is necessary for biofilm formation and host colonization by Vibrio fischeri. Mol Microbiol 82:114–130.
            *Cover photo and by-line on front cover

Morris, A. R. and K. L. Visick. 2010. Control of biofilm formation and colonization in Vibrio      fischeri: a role for partner switching? Environ Microbiol 12:2051–2059.

Mandel, M. J., M. S. Wollenberg, E. V. Stabb, K. L. Visick, and E. G. Ruby. 2009. A single regulatory gene is sufficient to alter bacterial host range. Nature 458:215-218.

Visick, K. L. 2009. An intricate network of regulators controls biofilm formation and colonization by Vibrio fischeri. Mol. Microbiol. 74:782-789.

Yildiz, F. H., and K. L. Visick. 2009. Vibrio biofilms: so much the same yet so different. Trends Microbiol. 17:109-118.

Hussa, E. A., C. Darnell, and K. L. Visick. 2008. RscS functions upstream of SypG to control thesyp locus and biofilm formation in Vibrio fischeri. J. Bacteriol. 190:4576-83.

Geszvain, K., and K. L. Visick. 2008. The hybrid sensor kinase RscS integrates positive and negative signals to modulate biofilm formation in Vibrio fischeri. J. Bacteriol. 190:4437-46.

Yip, E. S., K. Geszvain, C. R. DeLoney-Marino, and K. L. Visick. 2006. The symbiosis regulator RscS controls the syp gene locus, biofilm formation and symbiotic aggregation by Vibrio fischeri. Mol. Microbiol.62:1586-1600.


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