Professor of Microbiology
Office Location: Health Sciences, J179A
Campus Box: 357735
My research involves the study of bacterial communities. This research focuses on two aspects that are closely related. Quorum sensing is a term used to describe the regulation of gene expression according to population densities, many Gram-negative bacteria use specific signaling molecules, called acyl-homoserine lactones (acy-HSLs), to sense the presence of other bacteria of the same species in the bacterial cell membrane. At high cell densities the acyl-HSL reaches a critical concentration at which expression of quorum sensing-controlled genes is induced. Therefore, quorum sensing constitutes a rudimentary communication system between bacteria that allows them to coordinate behavior at the community level.
We are also interested in the surface-attached bacterial communities called biofilms. These bacteria are held together by an extracellular matrix. Most bacteria in the environment exist as biofilms and biofilm bacteria have been shown to possess unique characteristics that are not seen in conventional test tube-grown bacteria. It has also been estimated recently that up to 67% of bacterial infections involve biofilm bacteria. Therefore there is a growing appreciation for the need to study biofilm bacteria.
We use the opportunistic pathogen, Pseudomonas aeruginosa, as a model organism for our research. P. aeruginosa is responsible for a variety of nosocomial infections. It is also the primary infectious agent in lung infections of people suffering from Cystic Fibrosis. Recently, we determined that quorum sensing is important for normal biofilm development. This finding has important implications for understanding and controlling both clinical and environmental biofilms. We are trying to understand the mechanism of quorum sensing in biofilms at the molecular level. We also are interested in the extracellular matrix of P. aeruginosa biofilms - what is it made of? and how does it contribute to antimicrobial resistance? Our research utilizes cutting-edge technology such as scanning confocal laser microscopy and techiques from the fields of molecular biology, biochemistry, and bacterial pathogenesis.
Shrout, J.S., Chopp, D.L., Just, C.L., Hentzer, M., Givskov, M., and M.R. Parsek. 2006. The impact of quorum sensing and swarming motility on Pseudomonas aeruginosa biofilm formation is nutritionally conditional. Mol. Microbiol., In Press.
An, D., Danhorn, T., Fuqua, C., and M.R. Parsek. 2006. Quorum sensing and motility mediate interactions between Pseudomonas aeruginosa and Agrobacterium tumefaciens in biofilm co-cultures., PNAS., 2006 Mar 7; 103:3828-33.
Landry, R.L., Hupp, J.S., Singh, P.K., and M.R. Parsek. 2006. Mucin-P. aeruginosa interactions biofilm formation and antibiotic tolerance, Mol. Microbiol., 59:142-151.
Kirisits MJ, Prost L, Starkey M, M.R. Parsek. 2005. Characterization of Colony Morphology Variants Isolated from Pseudomonas aeruginosa Biofilms. Appl. Env. Microbiol., 71:4809-4821.
Parsek M.R. and E.P. Greenberg. 2005. Sociomicrobiology: the connections between quorum sensing and biofilms. Trends Microbiol. 13:27-33.
Parsek, M.R. and C. Fuqua. 2004. Biofilms 2003: Emerging themes and challenges in the study of surface-associated microbial life. J. Bacteriol., 186:4427-40.
Danhorn, T., Hentzer, M., Parsek, M.R. and C. Fuqua. 2004. Phosphorous limitation enhances biofilm formation of the plant pathogen Agrobacterium tumefaciens through the PhoR-PhoB regulatory system. J. Bacteriol., 186:4492-501.