Institute for Limnology, Austrian Academy of Sciences, Mondseestrasse 9, A-5310 Mondsee, Austria.
Environ Microbiol. 2010 Mar;12(3):658-69. doi: 10.1111/j.1462-2920.2009.02106.x. Epub 2009 Dec 22.
We present a survey on the distribution and habitat range of Polynucleobacter necessarius ssp. asymbioticus (PnecC), a numerically and functionally important taxon in the plankton of freshwater systems. We systematically sampled stagnant freshwater habitats in a heterogeneous 2000 km(2) area, together with ecologically different habitats outside this area. In total, 137 lakes, ponds and puddles were investigated, which represent an enormous diversity of habitats differing, e.g. in depth (< 10 cm-171 m) and pH (3.9-8.5). PnecC bacteria were detected by cultivation-independent methods in all investigated habitats, and their presence was confirmed by cultivation of strains from selected habitats representing the whole studied ecological range. The determined relative abundance of the subspecies ranged from values close to the detection limit of FISH (0.2%) to 67% (average 14.5%), and the highest observed absolute abundance was 5.3 x 10(6) cells ml(-1). Statistical analyses revealed that the abundance of PnecC bacteria was partially controlled by factors linked to concentrations of humic substances, which support the hypothesis that these bacteria utilize photodegradation products of humic substances. Based on the revealed statistical relationships, an average relative abundance of this subspecies of 20% in global freshwater habitats was extrapolated. Our study provides important implications for the current debate on ubiquity and biogeography in microorganisms.
我们对 Polynucleobacter necessarius ssp. asymbioticus（PnecC）的分布和栖息地范围进行了调查，PnecC 是淡水系统浮游生物中数量和功能上重要的分类群。我们系统地采集了 2000 平方公里不均匀区域内的静止淡水栖息地，以及该区域外的生态差异栖息地。总共调查了 137 个湖泊、池塘和水坑，它们代表了各种不同的栖息地，例如深度（<10cm-171m）和 pH 值（3.9-8.5）。通过非培养方法在所有调查的栖息地中均检测到 PnecC 细菌，并且通过培养来自代表整个研究生态范围的选定栖息地的菌株来证实其存在。确定的亚种相对丰度从接近 FISH（0.2%）的检测下限到 67%（平均值为 14.5%）不等，观察到的最高绝对丰度为 5.3 x 10(6)细胞 ml(-1)。统计分析表明，PnecC 细菌的丰度部分受到与腐殖质浓度相关的因素的控制，这支持了这些细菌利用腐殖质光降解产物的假说。根据揭示的统计关系，推断出全球淡水栖息地中该亚种的平均相对丰度为 20%。我们的研究对当前关于微生物普遍性和生物地理学的争论具有重要意义。
