Hullar Meredith A J, Kaplan Louis A, Stahl David A
Civil and Environmental Engineering, University of Washington, Seattle, WA 98112, USA.
Appl Environ Microbiol. 2006 Jan;72(1):713-22. doi: 10.1128/AEM.72.1.713-722.2006.
Recurring seasonal patterns of microbial distribution and abundance in three third-order temperate streams within the southeast Pennsylvania Piedmont were observed over 4 years. Populations associated with streambed sediments and rocks (epilithon) were identified using terminal restriction length polymorphism (tRFLP) and sequencing of 16S rRNA genes selectively amplified with primers for the bacterial domain. Analyses of the relative magnitudes of tRFLP peak areas by using nonmetric multidimensional scaling resolved clear seasonal trends in epilithic and sediment populations. Oscillations between two dominant groups of epilithic genotypes, explaining 86% of the seasonal variation in the data set, were correlated with temperature and dissolved organic carbon. Sequences affiliated with epilithic phototrophs (cyanobacteria and diatom chloroplasts), a Rhodoferax sp., and a Bacillus species clustered in the summer, whereas sequences most closely related to "Betaproteobacteria" (putative Burkholderia sp.), and a putative cyanobacterium clustered in the fall/spring. The sediment genotypes also clustered into two groups, and these explained 85% of seasonal variation but correlated only with temperature. A summer tRFLP pattern was characterized by prevalence of "Betaproteobacteria," "Gammaproteobacteria," and a Bacillus sp., whereas the winter/spring pattern was characterized by phylotypes most closely related to "Firmicutes," "Gammaproteobacteria," and "Nitrospirae." A close association between these headwater streams and their watersheds was suggested by the recovery of sequences related to microbial populations provisionally attributed to not only freshwaters but also terrestrial habitats.
在4年的时间里，对宾夕法尼亚州东南部皮埃蒙特地区的三条三级温带溪流中微生物分布和丰度的季节性循环模式进行了观测。使用末端限制性片段长度多态性（tRFLP）以及用细菌域引物选择性扩增的16S rRNA基因测序，对与河床沉积物和岩石（附石生物）相关的种群进行了鉴定。通过非度量多维标度分析tRFLP峰面积的相对大小，解析了附石生物和沉积物种群中明显的季节性趋势。附石生物基因型的两个优势组之间的振荡解释了数据集中86%的季节性变化，这与温度和溶解有机碳相关。与附石光合生物（蓝细菌和硅藻叶绿体）、一种红环菌属细菌和一种芽孢杆菌属相关的序列在夏季聚集，而与“β-变形菌纲”（假定的伯克霍尔德菌属）和一种假定的蓝细菌最密切相关的序列在秋季/春季聚集。沉积物基因型也聚为两组，这解释了85%的季节性变化，但仅与温度相关。夏季tRFLP模式的特征是“β-变形菌纲”、“γ-变形菌纲”和一种芽孢杆菌属占优势，而冬季/春季模式的特征是与“厚壁菌门”、“γ-变形菌纲”和“硝化螺旋菌门”最密切相关的系统发育型。这些源头溪流与其流域之间存在密切关联，这一点从与微生物种群相关的序列回收情况可以看出，这些微生物种群不仅暂时归因于淡水，还归因于陆地栖息地。
