Christian D. Mohr, PhD

Assistant Professor, Department of Microbiology and Immunology

Christian D. Mohr

Contact Info

mohrx005@umn.edu

Office Phone 612-625-7104

Lab Phone 612-625-6957

PhD, University of Texas Health Science Center, 1993

Research

Research Summary/Interests

Research in my laboratory is focused on the virulence factors and pathogenic mechanisms of the gram-negative bacterium Burkholderia cepacia. B. cepacia has recently emerged as an important opportunistic pathogen of the lower respiratory tract, affecting immunocompromised individuals and particularly cystic fibrosis (CF) patients.

Projects in My Laboratory:

Type III Secretion

Pathogenesis in a growing number of gram-negative bacteria is dependent on the secretion of virulence proteins via a conserved secretory system, termed type III. We have identified and characterized a genetic locus encoding multiple type III secretion genes in B. cepacia. Using allelic exchange mutagenesis, we generated defined null mutations in central components of the type III secretion system, and demonstrated that a type III mutant is severely attenuated in virulence in a murine model of infection. We are currently pursuing proteomic and genomic-based approaches to identify the secreted substrates of the B. cepacia type III translocon, as well as further characterize the role of type III secretion in modulating the host response to B. cepacia infection.

Cable Pilus Biogenesis

Cable pili are unique peritrichous adherence organelles expressed by certain strains ofB. cepacia. Cable pili have been shown to mediate binding to both cellular and acellular receptors, and likely promote B. cepacia colonization of the respiratory tract of compromised hosts. We have undertaken a genetic analysis of cable pili and have identified and characterized a locus (cbl) encoding structural, accessory, and regulatory components of the cable pilus biosynthetic pathway. We have also initiated studies to define the regulatory control of cable pilus gene expression, and have evidence that control is manifested at both the transcriptional and posttranscriptional levels. We have recently identified within the cbl locus three additional genes, designated cblS, cblT andcblR, predicted to encode new members of the superfamily of environmentally responsive two-component signal transduction systems. We are currently utilizing a combined genetic and biochemical approach to characterize the function of these genes and to define the signal transduction events controlling cable pilus gene expression

Electron micrographs of macrophages infected with Burkholderia cepacia

Electron micrographs of wild-type Burkholderia cepacia expressing cable pili (A-D) and a cblA mutant strain (E,F) blocked in cable pilus expression

Publications

  • Tomich, M. and C. D. Mohr. (2004). Genetic characterization of a multicomponent signal transduction system controlling the expression of cable pili in Burkholderia cenocepacia. J. Bacteriol. 186:3826-3836.
  • Tomich, M. and C. D. Mohr. (2004). Transcriptional and posttranscriptional control of cable pilus gene expression in Burkholderia cenocepacia. J. Bacteriol. 186:1009-1020
  • Tomich, M. and C. D. Mohr. (2003). Adherence and autoaggregation phenotypes of a Burkholderia cenocepacia cable pilus mutant. FEMS Microbiol. Lett. 228:287-297.
  • Tomich, M., A. Griffith, C. A. Herfst, J. L. Burns, and C. D. Mohr. (2003). Attenuated virulence of a Burkholderia cepacia type III secretion mutant in a murine model of infection. Infect. Immun. 71: 1405-1415.
  • Tomich, M., C. A. Herfst, J. W. Golden, and C. D. Mohr. (2002). Role of flagella in Burkholderia cepacia host cell invasion. Infect. Immun. 70:1799-1806.
  • Mohr, C. D., M. Tomich, and C. A. Herfst. (2001). Cellular aspects ofBurkholderia cepacia infection. Microbes Infect. 3:425-35.
  • D. Martin and C. D. Mohr. (2000). Invasion and intracellular survival ofBurkholderia cepacia. Infect. Immun. 68: 24-29.