Stephen Melville

• Ph.D., Microbiology, University of California at Davis, 1987
• Postdoctoral Fellow, University of California at Los Angeles, 1988 - 1992
• Postdoctoral Fellow and Lecturer, Tufts University School of Medicine, 1993 - 1995

Current Research

1. The interactions of the host immune system with the anaerobic bacterial pathogen Clostridium perfringens.  Specifically, the molecular mechanisms that allow the bacteria to avoid being killed by phagocytic cells of the immune system, macrophages and neutrophils
2. The molecular regulation of toxin synthesis by C. perfringens, especially the enterotoxin that is responsible from food poisoning outbreaks
3. The mechanism of pili-dependent gliding motility in C. perfringen

Type IV pili in C. perfringens-  We discovered  that C. perfringens, a gram-positive bacterium has type IV pili (TFP) and uses these to move across agar plates with a kind of gliding motility.  We are researching the underlying mechanisms for explaining how TFP function in virulence and the molecular mechanisms used to assemble the pili themselves.

Videos showing motility:

• Movie 1
• Movie 2
• Movie 3

Survival of C. perfringens in host tissues-  C. perfringens causes the lethal infection called gas gangrene.  This disease is 100% fatal if not treated.  We are using molecular techniques to identify virulence factors used by the bacterium to allow it to completely overwhelm the immune system and prevent itself from being killed.  We have discovered that macrophages play an unexpected role in limiting gas gangrene progression and also that phagocytosed C. perfringens can escape the phagosome and survive inside macrophages.  We are examining the role of toxins made by the bacteria to see how they contribute to this process.

Factors leading to heat resistance in spores made by C. perfringens-  C. perfringens is estimated to be the third common cause of bacterial food poisoning in the U. S.  It causes food poisoning by releasing a toxin (called CPE) in the intestines of patients who ingest food contaminated by the bacterium.  The bacteria only synthesize and release CPE when they are sporulating.  We are examining factors that allow the spores made by C. perfringens to resist being killed by normal cooking procedures.  We are also examining the connection between sporulation and CPE synthesis at the molecular level to try and understand how these complex process are co-regulated.

Melville, S. B. and Craig, L.  Type IV pili in Gram-positive bacteria.  2013. Microbiol Mol Biol Rev. In Press.

Kumar, S. S., Hendrick, W., Correll, J. B., Patterson A. D., Melville, S. B., and Ferry, J. G. 2013. Biochemistry and physiology of the β class carbonic anhydrase (Cpb) from Clostridium perfringens Strain 13.  J. Bacteriol. In Press.

Liu, H., Bouillaut, L., Sonenshein, A. L. and Melville, S. B. 2013. Use of a mariner-based transposon mutagenesis system to isolate Clostridium perfringens mutants deficient in gliding motility J. Bacteriol. 195: 629-636.

Rodgers K., Arvidson, C. G., and Melville, S. B.. 2011.  Expression of a Clostridium perfringens type IV pilin by Neisseria gonorrhoeae mediates adherence to muscle cells.  Infect Immun. 79:3096-3105. 

Hartman, A. H., Liu, H. and S. B. Melville. 2011. Construction and characterization of a lactose-inducible promoter system for controlled gene expression in Clostridium perfringens. Appl Environ Microbiol. 77:471-478.  

Orsburn B., Melville, S. B., and Popham D. L.  2010.  EtfA catalyzes the formation of dipicolinic acid in Clostridium perfringens. Mol Microbiol. 75:178-86.

Harry KH, Zhou R, Kroos L, and Melville S.B. 2009. Sporulation and enterotoxin (CPE) synthesis are controlled by the sporulation-specific sigma factors SigE and SigK in Clostridium perfringens. J Bacteriol. 191:2728-2742.

Orsburn, B., Sucre, K., Popham D. L., and Melville S. B. 2009. The SpmA/B and DacF proteins of Clostridium perfringens play important roles in spore heat resistance. FEMS Micro Lett. 291:188-94.

Varga, J. J., Therit, B. H., and Melville, S. B. 2008. Type IV pili and the CcpA protein are needed for maximal biofilm formation by the gram-positive anaerobic pathogen Clostridium perfringens. Infect Immun 76:4944-4951.

Orsburn B., Melville, S. B., and. Popham D. L.  2008. Factors contributing to heat resistance of Clostridium perfringens endospores. Appl Environ Microbiol. 74:3328-3335.

O’Brien, D. K., Therit, B. H., Woodman, M. E, and. Melville S. B.  2007. The role of neutrophils and monocytic cells in controlling the initiation of Clostridium perfringens gas gangrene infections.  FEMS Immunol Med Microbiol. 50:86-93.

Varga, J. J., Nguyen, V., O'Brien, D. K., Rodgers, K., Walker, R. A. and Melville, S. B.  2006. Type IV pili-dependent gliding motility in the Gram-positive pathogen Clostridium perfringens and other Clostridia.  Mol Microbiol. 62 (3): 680-694.

Myers, G. S., D. A. Rasko, J. K. Cheung, J. Ravel, R. Seshadri, R. T. Deboy, Q. Ren, J. Varga, M. M. Awad, L. M. Brinkac, S. C. Daugherty, D. H. Haft, R. J. Dodson, R. Madupu, W. C. Nelson, M. J. Rosovitz, S. A. Sullivan, H. Khouri, G. I. Dimitrov, K. L. Watkins, S. Mulligan, J. Benton, D. Radune, D. J. Fisher, H. S. Atkins, T. Hiscox, B. H. Jost, S. J. Billington, J. G. Songer, B. A. McClane, R. W. Titball, J. I. Rood, S. B. Melville, and I. T. Paulsen.  2006.  Skewed genomic variability in strains of the toxigenic bacterial pathogen, Clostridium perfringens. Genome Res 16:1031-40. 

Mastropaolo M. D., N. P. Evans, M. K. Byrnes, A. M. Stevens, J. L. Robertson, and S. B. Melville. 2005. Synergy in polymicrobial infections in a mouse model for type 2 diabetes. Infect Immun. 73:6055-6063.

O’Brien, D. K. and S. B. Melville. 2004. Effects of Clostridium perfringens alpha-toxin (PLC) and perfringolysin O (PFO) on cytotoxicity to macrophages, on escape from the phagosomes of macrophages, and on persistence of C. perfringens in host tissues. Infect Immun. 72:5204-5215.

Varga J, Stirewalt, V. L. and S. B. Melville. 2004. The CcpA protein is necessary for efficient sporulation and enterotoxin gene (cpe) regulation in Clostridium perfringens. J Bacteriol. 186:5221-5229.

O’Brien, D. K. and S. B. Melville. 2003. Multiple effects on Clostridium perfringens binding, uptake and trafficking to lysosomes by inhibitors to macrophage phagocytosis receptors. Microbiology, 149: 1377-1386.

O’Brien, D. K. and S. B. Melville. 2000. The anaerobic pathogen Clostridium perfringens can escape the phagosome of macrophages under aerobic conditions.  Cell Microbiol. 2: 505-519.

Walters, D. M., Stirewalt, V. L., and S. B. Melville. 1999. Cloning, sequence and transcriptional regulation of the operon encoding a putative N-acetylmannosamine-6-P epimerase (nanE) and sialic acid lyase (nanA) in Clostridium perfringens. J Bacteriol. 181:4526-4532.

Zhao, Y. and S. B. Melville. 1998. Identification and characterization of sporulation-dependent promoters upstream of the enterotoxin gene (cpe) of Clostridium perfringens.  J Bacteriol. 180:136-142.

Cotter, P., S. B. Melville, J. Albrecht, and R. P. Gunsalus. 1997. Aerobic regulation of the cytochrome d (cydAB) operon expression in Escherichia coli: roles of FNR and ArcA in repression and activation. Mol Microbiol. 25:605-615.

Melville, S. B. and R. P. Gunsalus. 1996. Isolation of an oxygen responsive FNR protein of Escherichia coli: interaction at activator and repressor sites of FNR controlled genes. Proc Natl Acad Sci. 93:1226-1231.

Melville, S. B., R. Labbe, and A. L. Sonenshein. 1994.  Expression from the Clostridium perfringens cpe promoter in C. perfringens and Bacillus subtilis.  Infect Immun. 62:5550-5558.

Melville, S. B. and R. P. Gunsalus. 1990. Mutations in fnr that alter anaerobic regulation of electron transport-associated genes in Escherichia coli. J Biol Chem. 265:18733-18736.

Melville, S. B., T. A. Michel, and J. M. Macy. 1988.  Pathway and sites for energy conservation in the metabolism of glucose by Selenomonas ruminantium. J Bacteriol. 170:5298-5304.

Melville, S. B., T. A. Michel, and J. M. Macy. 1988.  Regulation of carbon flow in Selenomonas ruminantium grown in glucose-limited continuous culture.  J Bacteriol. 170:5305-5311

Melville, S. B., T. A. Michel, and J. M. Macy. 1987.  Involvement of D-lactate and lactic acid racemase in the metabolism of glucose by Selenomonas ruminantium.  FEMS Microbiol Lett. 40:289-293.