Uniformed Services University of the Health Sciences
Department of Microbiology and Immunology
4301 Jones Bridge Road
Bethesda, Maryland 20814-4799
Phone: (301) 295-3424
Fax: (301) 295-1545
Molecular Genetics and Regulation of Virulence Gene Expression in Shigella;
Molecular Genetics of Chlamydia Pathogenicity.
Ph.D., University of Alabama, Birmingham
The major research interest of this laboratory is the molecular genetics of bacterial pathogenesis. Specifically, we study two intracellular pathogens: Shigella flexneri, a facultative intracellular pathogen and Chlamydia trachomatis, an obligate intracellular pathogen. Shigella are the causative agents of bacillary dysentery, a disease of major importance in many parts of the developing world. Organisms of the genus Chlamydia cause a variety of diseases including pneumonia, blinding eye infections, and sexually transmitted diseases. Our current studies on Shigella flexneri focus on three areas: anti-apoptosis and intracellular survival; intracellular metabolism; and cell signaling via secretion of the Osp effector proteins. We recently characterized the ability of Shigella to block induction of apoptosis in epithelial cells that the bacteria invade and we are defining the bacterial genes involved in anti-apoptosis and identifying the elements of the host apoptosis/survival pathway where these bacterial proteins interact. The second area of post invasion pathogenesis is focused on metabolic virulence genes, i.e. genes that are specifically required for pathogen growth within the cytoplasm of mammalian cells. We are interested in determining how Shigella grows intracellularly, what nutrients present in the host cytosol are the preferred substrates and what pathways the bacterium uses to metabolize these nutrients. The third area of post invasion pathogenesis is to understand how Shigella modulates the host inflammatory response to bacterial invasion. We recently identified a secreted effector protein, OspF, as a mediator of this response and are studying several other secreted effectors of Shigella that contribute to the bacterium's ability to both induce and dampen the inflammatory response. Another area of research is the study of how Shigella evolved from a non-pathogenic ancestor it shared with Escherichia coli to become a pathogen. These studies led us to propose the concept of pathoadaptation through loss of gene function as the newly evolved pathogen adapted to its new niche. Thus, Shigella has lost genes that are incompatible with virulence via deletion ("black holes"), insertion or point mutations. When these genes are re-introduced into Shigella, virulence becomes attenuated. The identification and study of these "anti-virulence" genes provides new avenues for understanding pathogenesis and opens up possibilities for the development of new treatments for dysentery as well as safer vaccine strains.
A major barrier to understanding how Chlamydia can cause such a broad range of diseases is the absence of genetic tools for studying the organism. An important focus of our efforts over the past 10 years has been to develop these tools so that the power of molecular genetics can be applied to understanding Chlamydia pathogenesis. Although we have not yet isolated stable transformants of Chlamydia, we have made significant progress in solving this difficult problem and we continue to be committed to developing these genetic tools. In addition, we are using a variety of molecular approaches to increase our understanding of Chlamydia biology. One project is to define the steps in peptidoglycan synthesis in Chlamydia and determine the role that peptidoglycan plays in the developmental cycle of the organism. Another project is focused on elucidating the pathways of synthesis or acquisition of essential metabolic intermediates and /or cofactors for which Chlamydia does not appear to have the genes for synthesis. For example, genome annotation of Chlamydia includes homologs for all seven genes of the shikimate pathway and predicts that Chlamydia synthesize shikimate and chorismate. Surprisingly, the annotation lacks genes for enzymes that would funnel chorismate into other pathways for synthesis of folate, phenylalanine, tyrosine, tryptophan, and ubiquinone. We are currently attempting to demonstrate that Chlamydia makes chorismate and then will determine how the bacterium moves this compound into the pathways for which it is a precursor. Similarly, Chlamydia has enzymes that require S-adenosyl methionine (SAM) as a methyl donor but it lacks the metK gene which encodes the enzyme for synthesis of SAM. We have proposed that Chlamydia obtain SAM from the host cytosol via a specific SAM transporter and we have identified a gene from a C. trachomatis library that appears to have SAM transport activity when expressed in E. coli. Finally, we are examining the synthesis/acquisition of lipoic acid by Chlamydia. Lipoic acid is a covalently bound disulfide-containing cofactor required for function of key metabolic pathways in most organisms. These projects may reveal novel pathways that are essential for Chlamydia growth and can therefore provide new targets for drug development. Our long-term goals are to use the genetic tools that we are developing to create defined mutants of Chlamydia to study intracellular metabolism and to understand regulation of the Chlamydia developmental cycle.
Bliven K.A., A.T.Maurelli. (2012) Antivirulence Genes: Insights into Pathogen Evolution through Gene Loss. Infect Immun. 80(12):4061-70.
Bliven K.A., Fisher D.J., A.T. Maurelli. (2012) Characterization of the activity and expression of arginine decarboxylase in human and animal Chlamydia pathogens. FEMS Microbiol Lett. [Epub ahead of print]
Fisher D.J., Fernández R.E., Adams N.E., A.T. Maurelli. (2012) Uptake of Biotin by Chlamydia Spp. through the Use of a Bacterial Transporter (BioY) and a Host-Cell Transporter (SMVT). PLoS One. 7(9):e46052
Rank R.G., Bowlin A.K., Tormanen K.I., Wang Y., A.T. Maurelli. (2012) Effect of inflammatory response on in vivo competition between two chlamydial variants in the guinea pig model of inclusion conjunctivitis. Infect Immun. 80(2):612-9.
Binet R., Fernandez R.E., Fisher D.J., A.T. Maurelli (2011) Identification and characterization of the Chlamydia trachomatis L2 S-adenosylmethionine transporter. MBio. 2(3):e00051-11.
Ramaswamy A.V., A.T. Maurelli. (2010) Chlamydia trachomatis serovar L2 can utilize exogenous lipoic acid through the action of the lipoic acid ligase LplA1. J Bacteriol. 192(23):6172-81.
Faherty C.S., D.S. Merrell, C. Semino-Mora, A. Dubois, A.V. Ramaswamy, A.T. Maurelli. (2010) Microarray analysis of Shigella flexneri-infected epithelial cells identifies host factors important for apoptosis inhibition. BMC Genomics. 11:272.
Binet R., A.K. Bowlin, A.T. Maurelli, R.G. Rank. (2010) Impact of azithromycin resistance mutations on the virulence and fitness of Chlamydia caviae in guinea pigs. Antimicrob Agents Chemother. 54(3):1094-101.
Binet R. and A.T. Maurelli. 2009. The chlamydial functional homolog of KsgA confers kasugamycin sensitivity to Chlamydia trachomatis and impacts bacterial fitness. BMC Microbiol. 9:279.
Faherty C.S. and A.T. Maurelli. (2009) Spa15 of Shigella flexneri is secreted through the type III secretion system and prevents staurosporine-induced apoptosis. Infect. Immun. 77(12):5281-90.
Binet R. and A.T. Maurelli. 2009. Transformation and isolation of allelic exchange mutants of Chlamydia psittaci using recombinant DNA introduced by electroporation. Proc Natl Acad Sci U S A. 106(1):292-7.
Zurawski D.V., K.L. Mumy, C.S. Faherty, B.A. McCormick, A.T. Maurelli. (2009) Shigella flexneri type III secretion system effectors OspB and OspF target the nucleus to downregulate the host inflammatory response via interactions with retinoblastoma protein. Mol Microbiol. 71(2):350-68.
Faherty C.S. and A.T. Maurelli. (2008) Staying alive: bacterial inhibition of apoptosis during infection. Trends in Microbiology.16(4):173-80. Review.
Zurawski D.V., K.L. Mumy, L. Badea, J.A. Prentice, E.L. Hartland, B.A. McCormick BA, A.T. Maurelli. (2008) NleE/OspZ family of effector proteins is required for PMN transepithelial migration, a characteristic shared by enteropathogenic Escherichia coli and Shigella flexneri infections. Infect Immun. 76(1):369-79.
Binet R. and A.T. Maurelli. (2007) Frequency of Development and Associated Physiological Cost of Azithromycin Resistance in Chlamydia psittaci 6BC and C. trachomatis L2. Antimicrob. Agents Chemother. 51 (12):4267-75.
Prunier A.L., R. Schuch, R.E. Fernández, A.T. Maurelli. 2007. Genetic Structure of the nadA and nadB Anti-virulence Loci in Shigella spp. J Bacteriol. 189(17): 6482-6.
Maurelli A.T. and AL Prunier AL. (2007) Mutations, Black Holes, and Antivirulence Genes. Microbe. August 2007.
Prunier AL, R. Schuch, R.E. Fernández, K.L. Mumy, H. Kohler, B.A. McCormick, A.T. Maurelli. (2007) nadA and nadB of Shigella flexneri 5a are antivirulence loci responsible for the synthesis of quinolinate, a small molecule inhibitor of Shigella pathogenicity. Microbiology. 153(Pt 7):2363-72.
Clark C.S. and A.T. Maurelli. (2007) Shigella flexneri Inhibits Staurosporine-Induced Apoptosis in Epithelial Cells. Infect Immun. 75(5):2531-9.
Maurelli A.T.. (2007) Black holes, antivirulence genes, and gene inactivation in the evolution of bacterial pathogens. FEMS Microbiol Lett. 267(1):1-8. Review.
McCoy A.J., N.E. Adams, A.O. Hudson, C. Gilvarg, T. Leustek, A.T. Maurelli. (2006) L,L-diaminopimelate aminotransferase, a trans-kingdom enzyme shared by Chlamydia and plants for synthesis of diaminopimelate/lysine. Proc Natl Acad Sci U S A. 103(47):17909-14.
Zurawski D.V., C. Mitsuhata, K.L. Mumy, B.A. McCormick, A.T. Maurelli. (2006) OspF and OspC1 are Shigella flexneri type III secretion system effectors that are required for postinvasion aspects of virulence. InfectImmun. 74(10):5964-76.
McCoy A.J. and A.T. Maurelli. (2006) Building the invisible wall: updating the chlamydial peptidoglycan anomaly. Trends Microbiol. 14(2):70-7.
Binet R. and A.T. Maurelli. (2005) Fitness cost due to mutations in the 16S rRNA associated with spectinomycin resistance in Chlamydia psittaci 6BC. Antimicrob. Agents Chemother. 49(11):4455-64.
Binet R. and A.T. Maurelli. (2005) Frequency of spontaneous mutations that confer antibiotic resistance in Chlamydia spp.. Antimicrob. Agents Chemother. 49 (7): 2865-2873.
McCoy A.J., and A.T. Maurelli. (2005) Characterization of Chlamydia MurC-Ddl, a fusion protein exhibiting D-alanyl-D-alanine ligase activity involved in peptidoglycan synthesis and D-cycloserine sensitivity. Mol. Micro. 57 (1): 41-52.
Honma Y., R.E. Fernández, A.T. Maurelli. (2004) A DNA adenine methylase mutant of Shigella flexneri shows no significant attenuation of virulence. Microbiology. 150(Pt 4):1073-8.
Verma A., and A.T. Maurelli. (2003) Identification of two eukaryote-like serine/threonine kinases encoded by Chlamydia trachomatis serovar L2 and characterization of interacting partners of Pkn1. Infect Immun. 71(10):5772-84.
McCoy A.J., R.C. Sandlin, A.T. Maurelli. 2003. In vitro and in vivo functional activity of Chlamydia MurA, a UDP-N-acetylglucosamine enolpyruvyl transferase involved in peptidoglycan synthesis and fosfomycin resistance. J. Bacteriol. 185(4):1218-28.
Kohler H, S.P. Rodrigues, A.T. Maurelli, B.A. McCormick. (2002) Inhibition of Salmonella typhimurium enteropathogenicity by piperidine, a metabolite of the polyamine cadaverine. J. Infect Dis. 186(8):1122-30.
Kane CD, R. Schuch, W.A. Day, A.T. Maurelli. (2002) MxiE regulates intracellular expression of factors secreted by the Shigella flexneri 2a type III secretion system. J. Bacteriol. 184(16):4409-19.
Schuch, R and A.T. Maurelli. (2001) MxiM and MxiJ, base elements of the Mxi-Spa type III secretion system of Shigella, interact with and stabilize the MxiD secretin in the cell envelope. J. Bacteriol. 183(24):6991-8.
Day W.A. Jr, R.E. Fernández, A.T. Maurelli. (2001) Pathoadaptive Mutations That Enhance Virulence: Genetic Organization of the cadA Regions of Shigella spp. Infect. Immun. 69:7471-80
Fernandez, I.M., M. Silva, R. Schuch, W.A. Walker, A.M. Siber, A.T. Maurelli, B.A. McCormick. (2001) Cadaverine prevents the escape of Shigella flexneri from the phagolysosome: a connection between bacterial dissemination and neutrophil transepithelial signaling. J. Infect. Dis. 184:743-53.
Schuch, R., and A.T. Maurelli. (2001) Spa33, a cell surface-associated subunit of the Mxi-Spa type III secretory pathway of Shigella flexneri, regulates Ipa protein traffic. Infect. Immun. 69:2180-9.
Day W.A. Jr. and A.T. Maurelli. (2001) Shigella flexneri LuxS quorum-sensing system modulates virB expression but is not essential for virulence. Infect. Immun. 69:15-23.
Schuch R., R.C. Sandlin, and A. T. Maurelli. (1999) A system for identifying post-invasion functions of invasion genes: requirements for the Mxi-Spa type III secretion pathway of Shigella flexneri in intercellular dissemination. Mol. Microbiol. 34:675-689.
McCormick B.A., M. I. Fernandez, A.M. Siber, and A. T. Maurelli. (1999) Inhibition of Shigella flexneri-induced transepithelial migration of polymorphonuclear leukocytes by cadaverine. Cell. Microbiol. 1:143-155.
Schuch R., and A. T. Maurelli. (1999) The Mxi-Spa type III secretory pathway of Shigella flexneri requires an outer membrane lipoprotein, MxiM, for invasin translocation. Infect. Immun. 67:1982-1991.
Sandlin R.C., and A. T. Maurelli. (1999) Establishment of unipolar localization of IcsA in Shigella flexneri 2a is not dependent on virulence plasmid determinants. Infect. Immun. 67:350- 356.
Maurelli A.T., P.R. Routh, R.C. Dilman, M. D. Ficken, D. M. Weinstock, G. W. Almond, and P. E. Orndorff. (1998) Shigella infection as observed in the experimentally inoculated domestic pig, Sus scrofa domestica. Microbial Pathogen. 25:189-196.
McCormick B.A., A.M. Siber, and A.T. Maurelli. (1998) Requirement of the Shigella flexneri virulence plasmid in the ability to induce trafficking of neutrophils across polarized monolayers of the intestinal epithelium. Infec. Immunity. 66:4237-4243.
Maurelli A.T., R.E. Fernández, C.A. Bloch, C.K. Rode, and A. Fasano. (1998) "Black holes" and bacterial pathogenicity: A large genomic deletion that enhances the virulence of Shigella spp. and enteroinvasive Escherichia coli. Proc. Natl. Acad. Sci. USA. 95:3943-3948.