Phylogenetic diversity and temporal variation in the Spirochaeta populations from two Mediterranean microbial mats Authors Mercedes Berlanga Department of Microbiology and Parasitology, University of Barcelona Jorn A. Aas Department of Molecular Genetics, Forsyth Institute Tahani Boumenna Department of Molecular Genetics, Forsyth Institute Floyd E. Dewhirst Department of Molecular Genetics, Forsyth Institute Bruce J. Paster Department of Molecular Genetics, Forsyth Institute Ricardo Guerrero Department of Microbiology University of Barcelona Keywords: Spirochaeta, bacterial phylogenetic diversity, temporal variation, microbial mats, symbiosis Abstract Spirochetes represent one of the bacterial groups often observed in hydrogen- sulfide-rich layers from coastal microbial mats. However, relatively few spirochetes from these microbial mats have been described and characterized. We have used 16S rDNA phylogenetic analysis to investigate the spirochetal diversity of microbial mats from two different geographic locations in the western Mediterranean (Ebro Delta, Spain, and Camargue, France). Samples from each delta was monitored in the spring and winter over 1 to 2 year’s duration. In the sequence analysis of 332 clones derived from samples of both deltas, 42 novel phylotypes of not-yet-cultivated spirochetes belonging to the genus Spirochaeta were detected. None of the phylotypes were identified as known culturable species of Spirochaeta or previously identified phylotyepes cloned from other hypersaline microbial mat such as Guerrero Negro. Eight of the phylotypes were common to Ebro and Camargue mats, two of them, IF058 and LL066 are present both in spring and winter. Some phylotypes appeared to show seasonal variation, i.e. they were found only in the spring, but not in the winter. On the other hand, Ebro and Camargue phylotypes compared with phylotypes from Guerrero Negro grouped according to the vertical gradient of oxygen and sulfide in the mat. Some phylotypes, such as LH073, IE028, LH042 or LG013 are harbored in low H2S or H2S-O2 interface zone. In contrast, major phylotypes were detected presumably in deeper layers and they are likely to be strict anaerobes and high tolerance to H2S. The presence of spirochetes in different located microbial mats suggests that constitutes a very diverse and stable population involved in a well-integrated “symbiosis” (i.e., permanent physiological cooperation) with other guild-populations in the mats to maintain a coordinated functional and stable community. Author Biographies Mercedes Berlanga, Department of Microbiology and Parasitology, University of Barcelona Department of Microbiology and Parasitology, University of Barcelona Jorn A. Aas, Department of Molecular Genetics, Forsyth Institute Department of Molecular Genetics, Forsyth Institute Tahani Boumenna, Department of Molecular Genetics, Forsyth Institute Department of Molecular Genetics, Forsyth Institute Floyd E. Dewhirst, Department of Molecular Genetics, Forsyth Institute Department of Molecular Genetics, Forsyth Institute Bruce J. Paster, Department of Molecular Genetics, Forsyth Institute Department of Molecular Genetics, Forsyth Institute Ricardo Guerrero, Department of Microbiology University of Barcelona Department of Microbiology University of Barcelona Downloads PDF Published 2010-09-21 Issue Vol. 11 No. 4 (2008) Section Research Articles License Submission of a manuscript to International Microbiology implies: that the work described has not been published before, including publication in the World Wide Web (except in the form of an Abstract or as part of a published lecture, review, or thesis); that it is not under consideration for publication elsewhere; that all the coauthors have agreed to its publication. 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