Institute for Limnology, Austrian Academy of Sciences, Mondsee, Austria.
FEMS Microbiol Ecol. 2012 Aug;81(2):467-79. doi: 10.1111/j.1574-6941.2012.01372.x. Epub 2012 Apr 23.
The distribution and abundance of Betaproteobacteria and three of its genera - Limnohabitans (R-BT065 lineage), Polynucleobacter (including subclusters Polynucleobacter necessarius and Polynucleobacter acidiphobus/Polynucleobacter difficilis), and Methylophilus - across the epilimnia of 72 limnologically diverse freshwater habitats were investigated using fluorescence in situ hybridization. Moreover, seasonal development of Betaproteobacteria subgroups along the longitudinal axis of a reservoir was followed. Betaproteobacteria comprised on average 29.1%, Polynucleobacter 11.6%, P. necessarius 10.1%, P. acidiphobus/difficilis 0.5%, Limnohabitans 8.9%, and Methylophilus 0.9% of total bacterioplankton cells in the investigated habitats. Polynucleobacter necessarius and Limnohabitans coexisted in the majority of habitats but showed contrasting abundance patterns along the pH gradient of habitats (pH, 3.8-8.5). The observed distribution patterns could theoretically be explained by different preferences for substrate sources, that is, substances of humic origin in acidic waters and algal-derived substances in alkaline waters. However, substrate utilization patterns observed in laboratory experiments indicate no coherent group-specific differences in substrate preferences. Interestingly, similar distribution patterns were revealed for Limnohabitans and P. acidiphobus/difficilis, suggesting similar ecological adaptations of these distantly related taxa. Our findings further emphasize that at least two taxa of freshwater Betaproteobacteria represent ecologically diversified groups. Investigations at higher phylogenetic resolution are required for obtaining further insights into their ecology.
采用荧光原位杂交技术，研究了贝塔变形菌及其三个属——Limnohabitans（R-BT065 谱系）、 Polynucleobacter（包括 Polynucleobacter necessarius 和 Polynucleobacter acidiphobus/Polynucleobacter difficilis 亚群）和 Methylophilus——在 72 个具有不同湖沼学特性的淡水生境中的分布和丰度。此外，还沿着一个水库的纵轴跟踪了贝塔变形菌亚群的季节性发展。贝塔变形菌平均占调查生境中总细菌浮游生物细胞的 29.1%， Polynucleobacter 占 11.6%，P. necessarius 占 10.1%，P. acidiphobus/difficilis 占 0.5%，Limnohabitans 占 8.9%，Methylophilus 占 0.9%。 Polynucleobacter necessarius 和 Limnohabitans 共存于大多数生境中，但在生境 pH 梯度（pH 为 3.8-8.5）上表现出相反的丰度模式。观察到的分布模式可以从对基质来源的不同偏好理论上解释，即酸性水中的腐殖质来源物质和碱性水中的藻类衍生物质。然而，实验室实验中观察到的基质利用模式表明，在基质偏好方面没有一致的特定群体差异。有趣的是，Limnohabitans 和 P. acidiphobus/difficilis 表现出相似的分布模式，表明这些亲缘关系较远的类群具有相似的生态适应。我们的研究结果进一步强调，至少有两个淡水贝塔变形菌类群代表了具有多样化生态的群体。需要进行更高系统发育分辨率的调查，以进一步了解它们的生态学。
