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Moraxella osloensis gene expression in the slug host Deroceras reticulatum.

An R, Sreevatsan S, Grewal PS - BMC Microbiol. (2008)

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Entomology Department, The Ohio State University, Wooster, OH 44691, USA. grewal.4@osu.edu.

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.

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Growth curve for M. osloensis in culture derived from measurements of OD 600 over time. Wild: wild-type M. osloensis; M-DsbC: mutant of dsbC gene; C-DsbC: complemented dsbC mutant; M-UbiS: mutant of ubiS gene; C-UbiS: complemented ubiS mutant. All data are shown as the mean of three repeated experiments with standard errors.
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Figure 3: Growth curve for M. osloensis in culture derived from measurements of OD 600 over time. Wild: wild-type M. osloensis; M-DsbC: mutant of dsbC gene; C-DsbC: complemented dsbC mutant; M-UbiS: mutant of ubiS gene; C-UbiS: complemented ubiS mutant. All data are shown as the mean of three repeated experiments with standard errors.

Mentions: As reduced virulence of mutants may result from growth defect, the growth rates of dsbC and ubiS mutants in the BHI medium were examined. Compared to the wild-type M. osloensis, the dsbC mutant did not show any growth defect in vitro (Fig. 3). However, the ubiS mutant showed significant reduction in growth rate in vitro. The ubiS mutant grew slower than the wild type and its viability (shown as OD600) was about 12% lower relative to the wild-type strain after 12 h (Fig. 3), and the growth defect became evident at the time of the late log phase entering into the stationary phase. In addition, the growth defect phenotype was fully complemented by the trans-complementation with the gene itself.


Moraxella osloensis gene expression in the slug host Deroceras reticulatum.

An R, Sreevatsan S, Grewal PS - BMC Microbiol. (2008)

Growth curve for M. osloensis in culture derived from measurements of OD 600 over time. Wild: wild-type M. osloensis; M-DsbC: mutant of dsbC gene; C-DsbC: complemented dsbC mutant; M-UbiS: mutant of ubiS gene; C-UbiS: complemented ubiS mutant. All data are shown as the mean of three repeated experiments with standard errors.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2266756&req=5

Figure 3: Growth curve for M. osloensis in culture derived from measurements of OD 600 over time. Wild: wild-type M. osloensis; M-DsbC: mutant of dsbC gene; C-DsbC: complemented dsbC mutant; M-UbiS: mutant of ubiS gene; C-UbiS: complemented ubiS mutant. All data are shown as the mean of three repeated experiments with standard errors.
Mentions: As reduced virulence of mutants may result from growth defect, the growth rates of dsbC and ubiS mutants in the BHI medium were examined. Compared to the wild-type M. osloensis, the dsbC mutant did not show any growth defect in vitro (Fig. 3). However, the ubiS mutant showed significant reduction in growth rate in vitro. The ubiS mutant grew slower than the wild type and its viability (shown as OD600) was about 12% lower relative to the wild-type strain after 12 h (Fig. 3), and the growth defect became evident at the time of the late log phase entering into the stationary phase. In addition, the growth defect phenotype was fully complemented by the trans-complementation with the gene itself.

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Entomology Department, The Ohio State University, Wooster, OH 44691, USA. grewal.4@osu.edu.

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.

Show MeSH
Related in: MedlinePlus