Ecotypes of planktonic Actinobacteria with identical 16S rRNA genes adapted to thermal niches in temperate, subtropical, and tropical freshwater habitats
Ecotypes of planktonic Actinobacteria with identical 16S rRNA genes adapted to thermal niches in temperate, subtropical, and tropical freshwater habitats
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DOI：
10.1128/aem.71.2.766-773.2005
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发表时间：
2005-02-01
影响因子：
4.4
通讯作者：
Pöckl, M
中科院分区：
文献类型：
--
作者：
Hahn, MW;Pöckl, M
从温带（奥地利和澳大利亚）、亚热带（中华人民共和国）和热带（乌干达）气候带的6个淡水生境中分离到7株具有相同165 rRNA基因的Luna2群（放线菌）。分离株的核糖体操纵子2,310个核苷酸片段在0到5个位置上存在序列差异，包括165 rRNA基因上游的部分基因间间隔区、完整的165 rRNA基因、完整的16S-23S内部转录间隔区（ITS1）和235 rRNA基因的一小部分。发现的少数序列差异大部分位于内部转录的间隔序列。来自亚洲和欧洲生境的两个分离株，以及来自中华人民共和国不同生境的两个分离株，在整个片段序列上具有相同的序列。尽管所研究的核糖体操纵子部分的序列差异很小，但菌株在温度响应曲线上表现出显著差异（只有一个例外），以及温度最佳值（25.0至35.6℃）的显著差异。所观察到的温度适应差异通常与菌株所在栖息地的热条件有关。来自温带生境的菌株具有最低温度最优，来自亚热带生境的菌株具有中等温度最优，来自热带生境的菌株具有最高温度最优。根据观察到的温度响应，我们得出结论，所调查的菌株对其家乡栖息地的热条件适应良好。因此，这些密切相关的菌株代表了适应不同热生态位的不同生态型。
Seven strains with identical 165 rRNA genes affiliated with the Luna2 cluster (Actinobacteria) were isolated from six freshwater habitats located in temperate (Austria and Australia), subtropical (People's Republic of China), and tropical (Uganda) climatic zones. The isolates had sequence differences at zero to five positions in a 2,310-nucleotide fragment of the ribosomal operon, including part of the intergenic spacer upstream of the 165 rRNA gene, the complete 165 rRNA gene, the complete 16S-23S internal transcribed spacer (ITS1), and a short part of the 235 rRNA gene. Most of the few sequence differences found were located in the internal transcribed spacer sequences. Two isolates obtained from habitats in Asia and Europe, as well as two isolates obtained from different habitats in the People's Republic of China, had identical sequences for the entire fragment sequenced. In spite of minimal sequence differences in the part of the ribosomal operon investigated, the strains exhibited significant differences in their temperature response curves (with one exception), as well as pronounced differences in their temperature optima (25.0 to 35.6degreesC). The observed differences in temperature adaptation were generally in accordance with the thermal conditions in the habitats where the strains were isolated. Strains obtained from temperate zone habitats had the lowest temperature optima, strains from subtropical habitats had intermediate temperature optima, and a strain from a tropical habitat had the highest temperature optimum. Based on the observed temperature responses, we concluded that the strains investigated are well adapted to the thermal conditions in their home habitats. Consequently, these closely related strains represent different ecotypes adapted to different thermal niches.