Dominance of green sulfur bacteria in the chemocline of the meromictic Lake Suigetsu, Japan, as revealed by dissimilator
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Dominance of green sulfur bacteria in the chemocline of the meromictic Lake Suigetsu, Japan, as revealed by dissimilatory sulfite reductase gene analysis Yumi Mori • Takafumi Kataoka • Takahiko Okamura • Ryuji Kondo
Received: 29 August 2012 / Revised: 18 December 2012 / Accepted: 16 February 2013 / Published online: 3 March 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract This study investigated the spatiotemporal abundance and diversity of the a-subunit of the dissimilatory sulfite reductase gene (dsrA) in the meromictic Lake Suigetsu for assessing the sulfur-oxidizing bacterial community. The density of dsrA in the chemocline reached up to 3.1 9 106 copies ml-1 in summer by means of quantitative real-time PCR and it was generally higher than deeper layers. Most of the dsrA clones sequenced were related to green sulfur bacteria such as Chlorobium phaeovibrioides, C. limicola, and C. luteolum. Below the chemocline of the lake, we also detected other dsrA clones related to the purple sulfur bacterium Halochromatium salexigens and some branching lineages of diverse sequences that were related to chemotrophic sulfur bacterial species such as Magnetospirillum gryphiswaldense, Candidatus Ruthia magnifica, and Candidatus Thiobios zoothamnicoli. The abundance and community compositions of sulfur-oxidizing bacteria changed depending on the
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Electronic supplementary material The online version of this article (doi:10.1007/s00203-013-0879-5) contains supplementary material, which is available to authorized users. Y. Mori T. Kataoka T. Okamura R. Kondo (&) Department of Marine Bioscience, Fukui Prefectural University, Obama, Fukui 917-0003, Japan e-mail: [email protected] Y. Mori e-mail: [email protected] Present Address: T. Kataoka Center for Marine Environmental Studies (CMES), Ehime University, Matsuyama, Ehime 790-8577, Japan
water depth and season. This study indicated that the green sulfur bacteria dominated among sulfur-oxidizing bacterial population in the chemocline of Lake Suigetsu and that certain abiotic environmental variables were important factors that determined sulfur bacterial abundance and community structure. Keywords Dissimilatory sulfite reductase gene Meromictic lake Phototrophic sulfur bacteria qPCR
Introduction Anoxic environments are widespread in nature including stratified lakes, coastal lagoons, estuaries, marine sediments, and microbial mats. In these environments, phototrophic sulfur bacteria supply organic carbon to chemoorganotrophic organisms; hence, they have a significant role in the anaerobic carbon cycle as well as the sulfur cycle. Phototrophic sulfur bacteria are characterized by their oxidation of reduced sulfur compounds, which serve as electron donors during carbon fixation and anoxygenic photosynthetic growth in aquatic environments when the anoxic layers containing reduced sulfur compounds are exposed to light (Brune 1995; Sireva˚g 1995). Phototrophic sulfur bacteria often form dense blooms in the oxic–anoxic
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