Karen Visick, PhD

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.

Christensen, D.G., A.E. Marsden, K. Hodge-Hanson, T. Essock-Burns, and K. L. Visick. 2020. LapG mediates biofilm dispersal in Vibrio fischeri by controlling maintenance of the VCBS-containing adhesin LapV. Mol Microbiol.  https://doi: 10.1111/mmi.14573.

Christensen, D. G. and K. L. Visick. 2020. Vibrio fischeri: Laboratory cultivation, storage, and common phenotypic assays. Curr Protoc Microbiol. 57(1):e103. doi: 10.1002/cpmc.103.

Christensen, D. G., J. Tepavčević,, and K. L. Visick. 2020. Genetic manipulation of Vibrio fischeri. Curr Protoc Microbiol. 59(1):e115. doi: 10.1002/cpmc.115.

Fuqua C, A. Filloux A, J.M. Ghigo, and K.L. Visick. 2019. Biofilms 2018: A diversity of microbes and mechanisms. J. Bacteriol. doi: 10.1128/JB.00118-1

Thompson, C. M., A. H. Tischler, D. Tarnowski, M.J. Mandel, and K. L. Visick. 2019. Nitric oxide inhibits biofilm formation by Vibrio fischeri via the nitric oxide-sensor HnoX. Mol Micro. 111(1):187-203.

Koehler, S., R. Gaedeke, C. Thompson, C Bongrand, K. L. Visick, E. Ruby, and M. McFall-Ngai. 2018. The model squid-vibrio symbiosis provides a window into the impact of strain- and species-level differences during the initial stages of symbiont engagement. Environ Microbiol. doi: 10.1111/1462-2920.

Tischler, A. H., L. Lie, C. M. Thompson, and K. L. Visick. 2018.  Discovery of calcium as a biofilm-promoting signal for Vibrio fischeri reveals new phenotypes and underlying regulatory complexity. J. Bacteriol. 200 (15): e00016-18.

Visick, K. L., K. M. Hodge-Hanson, A. H. Tischler, A. K. Bennett, and V. Mastrodomenico. 2018. Tools for rapid genetic engineering of Vibrio fischeri. Appl Environ Microbiol. 84:e00850-18.

Thompson CM, Marsden AE, Tischler AH, Koo J, Visick, K. L. 2018. Vibrio fischeri biofilm formation prevented by a trio of regulators. Appl Environ Microbiol. 84(19):e01257-18.

Visick, K. L., M. A. Schembri, F. Yildiz, and J. M. Ghigo. 2016. Biofilms 2015: Multidisciplinary approaches shed light into microbial life on surfaces. J. Bacteriol. 198(19): 2553-2563.

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.

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.

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.

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.

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.

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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