Microbiology & Immunology Faculty
David J. Kolodrubetz, Ph.D.
Periodontitis is an inflammatory disease of tissues in the subgingival crevice that can lead to soft tissue damage and bone loss. Aggregatibacter actinomycetemcomitans (Aa) and Campylobacter rectus are gram negative bacteria involved in the etiology of periodontal diseases. A number of virulence factors have been identified in these organisms including a leukotoxin from Aa and a proteinaceous layer, called the S-layer, on the outer membrane of C. rectus. The major goals in our lab are to determine the roles of these proteins, and other virulence factors, in pathogenesis and to unravel the mechanisms by which their synthesis is regulated by signals unique to the oral microenvironment. These fundamental questions are being addressed using genetic, molecular, genomic and biochemical approaches
Our work in Aa has focused on the regulation of leukotoxin transcription. We have shown that the regulation of Aa leukotoxin RNA synthesis by aerobic versus anaerobic growth uses a previously undefined mechanism. A systematic and comprehensive genetic approach was employed to identify three transcription factors (IHF, CRP, and Mlc) that are involved in the novel pathway of transcriptional regulation. Biochemical and genetic analyses are being done to determine the mechanisms by which these proteins coordinate with one another to accurately regulate leukotoxin synthesis in response to environmental cues.
Since IHF, CRP and Mlc are likely to be global regulatory proteins, and some of the non-leukotoxin genes they regulate are likely to have critical roles in Aa, we have used gene-expression microarrays to identify their regulons (the Aa genes that are differentially synthesized in wild type versus ihf, crp and mlc mutants). The CRP, IHF and Mlc regulons differ from those seen in other bacteria and dozens of regulated genes encode proteins of unknown functions. These are potential new virulence factors and their roles in the unique physiology and pathogenesis of Aa are being investigated by making and analyzing appropriate mutants.
The lab's studies with C. rectus have emphasized the function and secretion of the 150 kd S-layer protein. S-layer-negative mutants were used to show that the presence of the S-layer alters the cytokine profile produced by host cells in response to C. rectus. We have also shown that the S-layer protein is transported to the cell surface by a type I secretion system. Interestingly, another gene, called crsC, is involved in the release of some S-layer protein from the cell surface. We are pursuing this observation because the S-layer protein released from the C. rectus cell surface appears to have a new function, possibly as a cytotoxin.
- Feuerbacher LA, Burgum A, Kolodrubetz D. 2011. The cyclic-AMP receptor protein (CRP) regulon in Aggregatibacter actinomycetemcomitans includes leukotoxin. Microb Pathog; 51: 133-141.
- Kolodrubetz D, Phillips L, Burgum A. 2010. Repression of aerobic leukotoxin transcription by integration host factor (IHF) in A. actinomycetemcomitans. Res. in Microbiology; 161: 541-548.
- Chu L, Lai Y, Xu X, Eddy S, Yang S, Song L, Kolodrubetz D. 2008. A 52-kDa leucyl aminopeptidase from Treponema denticola is a cysteinylglycinase that mediates the second step of glutathione metabolism. J. Biol. Chem; 283:19351-19358.
- Lawley GR, Schindler WG, Walker III WA, Kolodrubetz D. 2004. Evaluation of ultrasonically placed MTA and fracture resistance with intracanal composite resin in a model of apexification. Journal of Endodontics;30:167-172.
- Kolodrubetz D, Phillips L, Jacobs C, Burgum A, Kraig E. 2003. Anaerobic regulation of A. actinomycetemcomitans leukotoxin transcription is ArcA/FnrA-independent and requires a novel promoter element. Res in Microbiology; 154:645-653.
Lab Rooms: 5.023V
- Linda Phillips, Research Associate