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Appl Environ Microbiol. 2012 Sep;78(17):6121-7. doi: 10.1128/AEM.01221-12. Epub 2012 Jun 22.

The physiological opportunism of Desulfitobacterium hafniense strain TCE1 towards organohalide respiration with tetrachloroethene.

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1
Ecole Polytechnique Fédérale de Lausanne, School of Architecture, Civil and Environmental Engineering, Laboratory for Environmental Biotechnology, Station 6, Lausanne, Switzerland.

Abstract

Desulfitobacterium hafniense strain TCE1 is capable of metabolically reducing tetra- and trichloroethenes by organohalide respiration. A previous study revealed that the pce gene cluster responsible for this process is located on an active composite transposon, Tn-Dha1. In the present work, we investigated the effects on the stability of the transposon during successive subcultivations of strain TCE1 in a medium depleted of tetrachloroethene. At the physiological level, an increased fitness of the population was observed after 9 successive transfers and was correlated with a decrease in the level of production of the PceA enzyme. The latter observation was a result of the gradual loss of the pce genes in the population of strain TCE1 and not of a regulation mechanism, as was postulated previously for a similar phenomenon described for Sulfurospirillum multivorans. A detailed molecular analysis of genetic rearrangements occurring around Tn-Dha1 showed two independent but concomitant events, namely, the transposition of the first insertion sequence, ISDha1-a, and homologous recombination across identical copies of ISDha1 flanking the transposon. A new model is proposed for the genetic heterogeneity around Tn-Dha1 in D. hafniense strain TCE1, along with some considerations for the cleavage mechanism mediated by the transposase TnpA1 encoded by ISDha1.

PMID:
22729540
PMCID:
PMC3416639
DOI:
10.1128/AEM.01221-12
[Indexed for MEDLINE]
Free PMC Article
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