Dominance of a clonal green sulfur bacterial population in a stratified lake |
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Authors: | Lea H. Gregersen,Kirsten S. Habicht,Sandro Peduzzi,Mauro Tonolla,Donald E. Canfield,Mette Miller,Raymond P. Cox,& Niels-Ulrik Frigaard |
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Affiliation: | Department of Biology, University of Copenhagen, Copenhagen N, Denmark;;Nordic Center for Earth Evolution and Institute of Biology, University of Southern Denmark, Odense M, Denmark;;Cantonal Institute of Microbiology, Bellinzona, Switzerland;;Alpine Biology Center Foundation Piora, Quinto, Switzerland;;Laboratory of Microbial Ecology, Microbiology Unit, Plant Biology Department, University of Geneva, Geneva, Switzerland;and;Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark |
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Abstract: | For many years, the chemocline of the meromictic Lake Cadagno, Switzerland, was dominated by purple sulfur bacteria. However, following a major community shift in recent years, green sulfur bacteria (GSB) have come to dominate. We investigated this community by performing microbial diversity surveys using FISH cell counting and population multilocus sequence typing [clone library sequence analysis of the small subunit (SSU) rRNA locus and two loci involved in photosynthesis in GSB: fmoA and csmCA ]. All bacterial populations clearly stratified according to water column chemistry. The GSB population peaked in the chemocline ( c . 8 × 106 GSB cells mL−1) and constituted about 50% of all cells in the anoxic zones of the water column. At least 99.5% of these GSB cells had SSU rRNA, fmoA , and csmCA sequences essentially identical to that of the previously isolated and genome-sequenced GSB Chlorobium clathratiforme strain BU-1 (DSM 5477). This ribotype was not detected in Lake Cadagno before the bloom of GSB. These observations suggest that the C. clathratiforme population that has stabilized in Lake Cadagno is clonal. We speculate that such a clonal bloom could be caused by environmental disturbance, mutational adaptation, or invasion. |
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Keywords: | Chlorobium clonal population bloom green sulfur bacteria Lake Cadagno |
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