Kirkwood Andrea E, Buchheim Julie A, Buchheim Mark A, Henley William J
Botany Department, Oklahoma State University, Stillwater, OK 74078, USA.
Microb Ecol. 2008 Apr;55(3):453-65. doi: 10.1007/s00248-007-9291-5. Epub 2007 Jul 26.
The Great Salt Plains (GSP) in north-central Oklahoma, USA is an expansive salt flat (approximately 65 km(2)) that is part of the federally protected Salt Plains National Wildlife Refuge. The GSP serves as an ideal environment to study the microbial diversity of a terrestrial, hypersaline system that experiences wide fluctuations in freshwater influx and diel temperature. Our study assessed cyanobacterial diversity at the GSP by focusing on the taxonomic and physiological diversity of GSP isolates, and the 16S rRNA phylogenetic diversity of isolates and environmental clones from three sites (north, central, and south). Taxonomic diversity of isolates was limited to a few genera (mostly Phormidium and Geitlerinema), but physiological diversity based on halotolerance ranges was strikingly more diverse, even between strains of the same phylotype. The phylogenetic tree revealed diversity that spanned a number of cyanobacterial lineages, although diversity at each site was dominated by only a few phylotypes. Unlike other hypersaline systems, a number of environmental clones from the GSP were members of the heterocystous lineage. Although a number of cyanobacterial isolates were close matches with prevalent environmental clones, it is not certain if these clones reflect the same halotolerance ranges of their matching isolates. This caveat is based on the notable disparities we found between strains of the same phylotype and their inherent halotolerance. Our findings support the hypothesis that variable or poikilotrophic environments promote diversification, and in particular, select for variation in ecotype more than phylotype.
美国俄克拉何马州中北部的大盐原（GSP）是一片广阔的盐滩（约65平方千米），是联邦保护的盐原国家野生动物保护区的一部分。大盐原为研究淡水流入量和昼夜温度波动较大的陆地高盐系统中的微生物多样性提供了理想环境。我们的研究通过关注大盐原分离株的分类学和生理多样性，以及来自三个地点（北部、中部和南部）的分离株和环境克隆的16S rRNA系统发育多样性，评估了大盐原的蓝藻多样性。分离株的分类多样性仅限于少数几个属（主要是席藻属和鞘丝藻属），但基于耐盐范围的生理多样性则明显更为多样，即使是同一系统型的菌株之间也是如此。系统发育树显示出跨越多个蓝藻谱系的多样性，尽管每个地点的多样性仅由少数几个系统型主导。与其他高盐系统不同，大盐原的许多环境克隆属于异形胞谱系。尽管一些蓝藻分离株与常见的环境克隆密切匹配，但不确定这些克隆是否反映了与其匹配的分离株相同的耐盐范围。这一警告基于我们在同一系统型菌株与其固有耐盐性之间发现的显著差异。我们的研究结果支持了可变或变养环境促进多样化这一假设，特别是选择生态型而非系统型的变异。
