Department of Microbiology, Southern Illinois University, Carbondale, IL 62901, USA.
Department of Microbiology and Plant Sciences, University of Oklahoma, Norman, OK 73019, USA.
Can J Microbiol. 2021 Apr;67(4):332-341. doi: 10.1139/cjm-2020-0462. Epub 2020 Nov 2.
Hot Lake is a small heliothermal and hypersaline lake in far north-central Washington State (USA) and is limnologically unusual because MgSO rather than NaCl is the dominant salt. In late summer, the Hot Lake metalimnion becomes distinctly green from blooms of planktonic phototrophs. In a study undertaken over 60 years ago, these blooms were predicted to include green sulfur bacteria, but no cultures were obtained. We sampled Hot Lake and established enrichment cultures for phototrophic sulfur bacteria in MgSO-rich sulfidic media. Most enrichments turned green or red within 2 weeks, and from green-colored enrichments, pure cultures of a lobed green sulfur bacterium (phylum ) were isolated. Phylogenetic analyses showed the organism to be a species of the prosthecate green sulfur bacterium . Cultures of this Hot Lake phototroph were halophilic and tolerated high levels of sulfide and MgSO. In addition, unlike all recognized species of , the Hot Lake isolates grew at temperatures up to 45 °C, indicating an adaptation to the warm summer temperatures of the lake. Photoautotrophy by Hot Lake green sulfur bacteria may contribute dissolved organic matter to anoxic zones of the lake, and their diazotrophic capacity may provide a key source of bioavailable nitrogen, as well.
热湖是美国华盛顿州中北部一个小型的热液和高盐湖泊，其湖水中的主要盐分是硫酸镁而非氯化钠，这使得它在湖沼学上具有独特性。每年夏末，热湖的弱光层会因为浮游藻类的大量繁殖而呈现出明显的绿色。在 60 多年前的一项研究中，这些藻类的爆发被预测会包括绿硫细菌，但当时并未获得任何培养物。我们对热湖进行了采样，并在富含硫酸镁的硫化物培养基中对光合硫细菌进行了富集培养。大多数培养物在 2 周内变成绿色或红色，而从绿色的富集物中，我们成功分离出了一种具有叶状结构的绿硫细菌（门）的纯培养物。系统发育分析表明，该生物体是一种具有突起的绿硫细菌。这种热湖光合生物的培养物是嗜盐的，可以耐受高浓度的硫化物和硫酸镁。此外，与所有已知的绿硫细菌物种不同，热湖分离株可以在高达 45°C 的温度下生长，这表明它们已经适应了湖泊夏季温暖的温度。热湖绿硫细菌的光合作用可能会为湖泊缺氧区提供溶解有机物质，而其固氮能力也可能为生物可利用氮提供一个关键来源。
