Description of Current Research :
Either harmful or beneficial bacterium-host interactions can trigger similar host-responses that respectively result in eradication or tolerance of the bacterium. How bacteria can appropriately communicate to a host its benign naturre and how hosts can discriminate between harmful and beneficial bacteria is poorly understood. Using as a model system they symbiosis of the bioluminescent bacterium, Vibrio fischeri, with its animal host, the squid Euprymna scolopes, my research seeks to elucidate how bacteria initiate and maintain long-term associations and how hosts recognize and respond to their desired symbiotic partner.
Symbiotic colonization is a dynamic process that requires adaptation by both partners. The host is an active participant during initiation of the symbiotic association, collecting bacteria from the surrounding seawater in mucus it secretes from paired epithelial appendages attached to the light organ and concentrating them near the entrance to the organ that eventually cultures the bacterial symbiont. Although various bacterial species associate with the mucus, only the correct symbiont, V. fischeri, is able to successfully enter into symbiosis by overcoming host-imposed checkpoints. Studies indicate that during the specific cooperative association between V. fisheri and its squid host, the baacterial two-component regulator GacA, coordinately regulates the expression of bacterial traits that alllow it to initiate a benign infection of the squid's light-emitting organ. GacA mutants of V. fischeri are less effective at initiating infection and are also impaired at forming tight aggregates during infection. When its light organ is colonized by V. fischeri, the squid host adapts to this association and, in response to bacterial signals, undergoes a program of changes that leads to the normal develoment of the light organ. One of the most striking changes is apoptosis in and regression of the appendages over a four-day period. GacA mutants that successfully colonize squid light organs do not trigger normal apoptosis during regression of these appendages, implying that delivery of bacterial signals to the squid host is GacA-controlled. Furthermore, GacA mutants fail to trigger cessation of mucus shedding, a colonization response that normally limits further bacterial interaction.
My current research focus will use the GacA mutant as a basis for identifying and characterization colonization traits. These studies will provide insight into bacteria-derived signals that allow hosts to respond appropriately to beneficial organisms, thus allowing association, without compromising the ability of immune responses to protect the host from pathogenic infection. We are currently utilizing a recently generated DNA microarray of the entire genome of V. fischeri, and will also combine this genomic approach with random mutagenesis screens to discover previously uncharacterized genes and traits that contribute to animal tissue colonization.
Ph.D., Molecular and Cellular Biology, Oregon State University
B.A., General Biology, University of California - San Diego
BMS 503: General Microbiology
BMS 790: Undergrad Teaching Experience
GEN 704: Genetics Prokaryotic Microbes
GEN 790: Undergrad Teaching Experience
GEN 999: Doctoral Research
INCO 590: Rsrch Exp/MCBS
MCBS 905: Contemp Top Molec/Cell/Biomed
MCBS 997: Seminar
Xu, F., Gonzalez-Escalona, N., Drees, K. P., Sebra, R. P., Cooper, V. S., Jones, S. H., & Whistler, C. A. (2017). Parallel Evolution of Two Clades of an Atlantic-Endemic Pathogenic Lineage of Vibrio parahaemolyticus by Independent Acquisition of Related Pathogenicity Islands. Applied and Environmental Microbiology, 83(18). doi:10.1128/aem.01168-17
Xu, F., Gonzalez-Escalona, N., Haendiges, J., Myers, R. A., Ferguson, J., Stiles, T., . . . Whistler, C. A. (2017). Sequence Type 631 Vibrio parahaemolyticus, an Emerging Foodborne Pathogen in North America. Journal of Clinical Microbiology, 55(2), 645-648. doi:10.1128/jcm.02162-16
Foxall, R. L., Ballok, A. E., Avitabile, A., & Whistler, C. A. (2015). Spontaneous phenotypic suppression of GacA-defective Vibrio fischeri is achieved via mutation of csrA and ihfA. BMC Microbiology, 15(1). doi:10.1186/s12866-015-0509-2
Whistler, C. A., Hall, J. A., Xu, F., Ilyas, S., Siwakoti, P., Cooper, V. S., & Jones, S. H. (2015). Use of Whole-Genome Phylogeny and Comparisons for Development of a Multiplex PCR Assay To Identify Sequence Type 36 Vibrio parahaemolyticus. Journal of Clinical Microbiology, 53(6), 1864-1872. doi:10.1128/jcm.00034-15
Fidopiastis, P. M., Rader, B. A., Gerling, D. G., Gutierrez, N. A., Watkins, K. H., Frey, M. W., . . . Whistler, C. A. (2013). Characterization of a Vibrio fischeri Aminopeptidase and Evidence for Its Influence on an Early Stage of Squid Colonization. Journal of Bacteriology, 195(14), 3298. doi:10.1128/jb.00578-13
Mahoney, J. C., Gerding, M. J., Jones, S. H., & Whistler, C. A. (2010). Comparison of the Pathogenic Potentials of Environmental and Clinical Vibrio parahaemolyticus Strains Indicates a Role for Temperature Regulation in Virulence. Applied and Environmental Microbiology, 76(22), 7459-7465. doi:10.1128/aem.01450-10
Whistler, C. A., & Ruby, E. G. (2003). GacA Regulates Symbiotic Colonization Traits of Vibrio fischeri and Facilitates a Beneficial Association with an Animal Host. Journal of Bacteriology, 185(24), 7202-7212. doi:10.1128/jb.185.24.7202-7212.2003
Whistler, C. A., Stockwell, V. O., & Loper, J. E. (2000). Lon Protease Influences Antibiotic Production and UV Tolerance of Pseudomonas fluorescens Pf-5. Applied and Environmental Microbiology, 66(7), 2718-2725. doi:10.1128/aem.66.7.2718-2725.2000
Whistler, C. A., Corbell, N. A., Sarniguet, A., Ream, W., & Loper, J. E. (1998). The two-component regulators GacS and GacA influence accumulation of the stationary-phase sigma factor sigma(S) and the stress response in Pseudomonas fluorescens Pf-5. JOURNAL OF BACTERIOLOGY, 180(24), 6635-6641. Retrieved from http://gateway.webofknowledge.com/
Heath-Heckman, E. A. C., Peyer, S. M., Whistler, C. A., Apicella, M. A., Goldman, W. E., & McFall-Ngai, M. J. (n.d.). Bacterial Bioluminescence Regulates Expression of a Host Cryptochrome Gene in the Squid-Vibrio Symbiosis. mBio, 4(2). doi:10.1128/mbio.00167-13