University of Connecticut |
Education: Ph.D. University of Southern California, Postdoctoral study, University of Berne, Switzerland Research Interests: While all animals are colonized by bacteria, we know very little about molecular interactions between these bacteria and their host animal unless the bacteria cause disease. The main goal of our research is to enhance the general understanding of how bacteria and animals interact. As a model for digestive-tract associations, we investigate the digestive-tract symbiosis of the medicinal leech, Hirudo medicinalis . In the largest compartment of the leech digestive tract, only two species of bacteria are found, Aeromonas veronii and a novel Rikenella species. Historically, the study of digestive-tract symbioses has been hindered by the presence of complex microbial communities but the unusual simplicity of the leech symbiosis provides an opportunity to investigate the interaction on a molecular level. While A. veronii functions as a cooperative symbiont inside the leech, this species is also a human pathogen when injected into vertebrate tissue during leech feeding, causing wound infections and, when ingested, diarrhea. The switching between symbiotic and pathogenic lifestyles suggests the ability of A. veronii to regulate its physiology according to its host and provides an opportunity to learn about the evolution of bacteria-animal associations. We use molecular tools to tease apart the interaction and epifluorescent microscopy for visualization of the symbionts. Additional research interests include the use of 16S rRNA gene sequences for the identification of bacteria, the molecular investigation of other symbiotic or pathogenic bacteria, and the discovery of novel antimicrobial compounds. Selected Publications:
Kikuchi, Y. L. Bomar and J. Graf. 2009. Stratified bacterial community in the bladder of the medicinal leech, Hirudo verbana. Environ. Microbiol. in press. Rio, R.V.M., M. Maltz, B. McCormick, A. Reiss and J. Graf. 2009. Symbiont Succession during the Embryonic Development of the European Medicinal Leech, Hirudo verbana. Appl. Environ. Microbiol. in press. Laufer, A., M. Siddall and J. Graf. 2008. Characterization of the Digestive-Tract Microbiota of Hirudo orientalis, a European Medicinal Leech. Appl. Environ. Microbiol. 74:6151-6154. Silver, A.C., Y. Kikuchi, A. A. Fadl, J. Sha, A. Chopra and J. Graf. 2007. Interaction between innate immune cells and a bacterial type-three secretion system in mutualistic and pathogenic associations. Proc. Natl. Acad. Sci.USA. 104:9481-9486. Rio, R.V.M., M. Anderegg and J. Graf. 2007. Characterization of a catalase gene from Aeromonas veronii, the digestive-tract symbiont of the medicinal leech. Microbiology. 153:1897-1906. Kikuchi, Y. and J. Graf. 2007. Spatial and temporal population dynamics of a naturally occurring two-species microbial community inside the Medicinal Leech. Appl. Environ. Microbiol. 73:1984-1991. (cover article) Worthen, P. L., C. J. Gode and J. Graf. 2006. Culture-independent characterization of the digestive-tract microbiota of the medicinal leech, a tripartide symbiosis. Appl. Environ. Microbiol. 72:4775-4781. Graf, J. 2005. Molecular requirements for the colonization of Hirudo medicinalis by Aeromonas veronii . In: Overmann, J. (ed) Molecular mechanisms of symbiosis. Series: Progress in Molecular and Subcellular Biology. Springer-Verlag, Berlin. Braschler, T., S. Merino, J. Tomas, and J. Graf . 2003. Complement resistance is essential for the colonization of the digestive tract of Hirudo medicinalis by Aeromonas strains. Appl. Envrionment. Microbiol. 69:4268-4271. Graf, J. 2002. The effect of the symbionts on the physiology of Hirudo medicinalis , the medicinal leech. Inv. Reproductive Develop Biol. 41:269-275. Iten, A., S. Graf, M. Egger, M. Tauber and J. Graf. 2001. Helicobacter sp. flexispira bacteremia in an immunocompetent young adult. J. Clin. Microbiol. 39:1716-1720. |
