Abstract
Background. The bacterium Moraxella osloensis is a mutualistic symbiont of the slug-parasitic nematode Phasmarhabditis hermaphrodita. In nature, P. hermaphrodita vectors M. osloensis into the shell cavity of the slug host Deroceras reticulatum in which the bacteria multiply and kill the slug. As M. osloensis is the main killing agent, genes expressed by M. osloensis in the slug are likely to play important roles in virulence. Studies on pathogenic interactions between bacteria and lower order hosts are few, but such studies have the potential to shed light on the evolution of bacterial virulence. Therefore, we investigated such an interaction by determining gene expression of M. osloensis in its slug host D. reticulatum by selectively capturing transcribed sequences. Results. Thirteen M. osloensis genes were identified to be up-regulated post infection in D. reticulatum. Compared to the in vitro expressed genes in the stationary phase, we found that genes of ubiquinone synthetase (ubiS) and acyl-coA synthetase (acs) were up-regulated in both D. reticulatum and stationary phase in vitro cultures, but the remaining 11 genes were exclusively expressed in D. reticulatum and are hence infection specific. Mutational analysis on genes of protein-disulfide isomerase (dsbC) and ubiS showed that the virulence of both mutants to slugs was markedly reduced and could be complemented. Further, compared to the growth rate of wild-type M. osloensis, the dsbC and ubiS mutants showed normal and reduced growth rate in vitro, respectively. Conclusion. We conclude that 11 out of the 13 up-regulated M. osloensis genes are infection specific. Distribution of these identified genes in various bacterial pathogens indicates that the virulence genes are conserved among different pathogen-host interactions. Mutagenesis, growth rate and virulence bioassays further confirmed that ubiS and dsbC genes play important roles in M. osloensis survival and virulence, respectively in D. reticulatum.
| Original language | English (US) |
|---|---|
| Article number | 19 |
| Journal | BMC microbiology |
| Volume | 8 |
| DOIs | |
| State | Published - 2008 |
Bibliographical note
Funding Information:We appreciate the helpful reviews of the manuscript by Dr. Michael Sad-owsky (Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN), Dr. David Denlinger (Department of Entomology, The Ohio State University, Columbus, OH), and Dr. Man-Wah Tan (Genetics and Microbiology and Immunology Departments, Stanford University, Palo Alto, CA). We thank Ms. Judy A. Smith for help with slug collection and Ms. Megan Strother for technical assistance. This research was supported by an interdisciplinary grant from the Ohio Agricultural Research and Development Center, Wooster, Ohio.