Non-sulfate-reducing, syntrophic bacteria affiliated with Desulfotomaculum cluster I are widely distributed in methanogenic environments

Hiroyuki Imachi, Yuji Sekiguchi, Yoichi Kamagata, Alexander Loy, Yan Ling Qiu, Philip Hugenholtz, Nobutada Kimura, Michael Wagner, Akiyoshi Ohashi, Hideki Harada

Research output: Contribution to journalArticlepeer-review

137 Citations (Scopus)


The classical perception of members of the gram-positive Desulfotomaculum cluster I as sulfate-reducing bacteria was recently challenged by the isolation of new representatives lacking the ability for anaerobic sulfate respiration. For example, the two described syntrophic propionate-oxidizing species of the genus Pelotomaculum form the novel Desulfotomaculum subcluster Ih. In the present study, we applied a polyphasic approach by using cultivation-independent and culturing techniques in order to further characterize the occurrence, abundance, and physiological properties of subcluster Ih bacteria in low-sulfate, methanogenic environments. 16S rRNA (gene)-based cloning, quantitative fluorescence in situ hybridization, and real-time PCR analyses showed that the subcluster Ih population composed a considerable part of the Desulfotomaculum cluster I community in almost all samples examined. Additionally, five propionate-degrading syntrophic enrichments of subcluster Ih bacteria were successfully established, from one of which the new strain MGP was isolated in coculture with a hydrogenotrophic methanogen. None of the cultures analyzed, including previously described Pelotomaculum species and strain MGP, consumed sulfite, sulfate, or organosulfonates. In accordance with these phenotypic observations, a PCR-based screening for dsrAB (key genes of the sulfate respiration pathway encoding the alpha and beta subunits of the dissimilatory sulfite reductase) of all enrichments/(co)cultures was negative with one exception. Surprisingly, strain MGP contained dsrAB, which were transcribed in the presence and absence of sulfate. Based on these and previous findings, we hypothesize that members of Desulfotomaculum subcluster Ih have recently adopted a syntrophic lifestyle to thrive in low-sulfate, methanogenic environments and thus have lost their ancestral ability for dissimilatory sulfate/sulfite reduction.

Original languageEnglish
Pages (from-to)2080-2091
Number of pages12
JournalApplied and environmental microbiology
Issue number3
Publication statusPublished - 2006 Mar
Externally publishedYes

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology


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