Gregersen Lea H, Habicht Kirsten S, Peduzzi Sandro, Tonolla Mauro, Canfield Donald E, Miller Mette, Cox Raymond P, Frigaard Niels-Ulrik
Department of Biology, University of Copenhagen, Copenhagen N, Denmark.
FEMS Microbiol Ecol. 2009 Oct;70(1):30-41. doi: 10.1111/j.1574-6941.2009.00737.x. Epub 2009 Jul 1.
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 x 10(6) 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.
多年来，瑞士卡达尼奥湖（Lake Cadagno）的化学分层湖中的化学跃层一直由紫色硫细菌主导。然而，近年来在一次主要的群落转变之后，绿色硫细菌（GSB）开始占据主导地位。我们通过使用荧光原位杂交（FISH）细胞计数和群体多位点序列分型[小亚基（SSU）rRNA基因座以及参与绿色硫细菌光合作用的两个基因座：fmoA和csmCA的克隆文库序列分析]进行微生物多样性调查，对这个群落进行了研究。所有细菌种群都根据水柱化学性质明显分层。绿色硫细菌种群在化学跃层达到峰值（约8×10⁶个绿色硫细菌细胞 mL⁻¹），并在水柱缺氧区的所有细胞中占约50%。这些绿色硫细菌细胞中至少99.5%的SSU rRNA、fmoA和csmCA序列与先前分离并进行基因组测序的绿色硫细菌布氏绿菌（Chlorobium clathratiforme）菌株BU - 1（DSM 5477）的序列基本相同。在绿色硫细菌大量繁殖之前，这种核糖型在卡达尼奥湖中未被检测到。这些观察结果表明，在卡达尼奥湖稳定下来的布氏绿菌种群是克隆性的。我们推测这种克隆性大量繁殖可能是由环境干扰、突变适应或入侵引起的。
