Weiss P, Schweitzer B, Amann R, Simon M
Limnological Institute, University of Konstanz, Constance, Germany.
Appl Environ Microbiol. 1996 Jun;62(6):1998-2005. doi: 10.1128/aem.62.6.1998-2005.1996.
Microbial assemblages on large organic aggregates (lake snow) of Lake Constance, Germany, were analyzed with rRNA-directed fluorescent oligonucleotide probes specific for the domain Bacteria and the alpha-, beta-, and gamma-subclasses of the class Proteobacteria. Lake snow aggregates were either collected in situ by SCUBA diving or in a sediment trap at 50 m or formed of natural lake water incubated in rolling cylinders under simulated in situ conditions. For the latter aggregates, the time course of the microbial colonization was also examined. The natural aggregates and those made in rolling cylinders were composed of the particulate organic material present in the lake and thus reflected the composition of the ambient plankton community. All types of lake snow aggregates examined were heavily colonized by microbial cells and harbored between 0.5 x 10(6) and > 2 x 10(6) cells aggregate -1. Between 55 and 100% of the microbial cells stained with 4', 6-diamidino-2-phenylindole (DAPI) could be visualized with the domain Bacteria-specific probe. In most samples, beta-subclass proteobacteria dominated the microbial community, constituting 27 to 42% of total cells as counted by DAPI staining, irrespective of the composition of the aggregates. During the time course experiments with the laboratory-made aggregates, the fraction of beta-subclass proteobacteria usually increased over time. Except for a few samples, alpha- and gamma-subclass proteobacteria were far less abundant than beta-subclass proteobacteria, constituting 11 to 25 and 9 to 33% of total cells, respectively. Therefore, we assume that a specific aggregate-adapted microbial community was established on the aggregates. Because the compositions of the microbial assemblages on natural and laboratory-made aggregates were similar, we conclude that aggregates made in rolling cylinders are good model system with which to examine the formation and microbial colonization of macroscopic organic aggregates.
利用针对细菌域以及变形菌纲α-、β-和γ-亚类的rRNA导向荧光寡核苷酸探针，对德国康斯坦茨湖大型有机聚集体（湖雪）上的微生物群落进行了分析。湖雪聚集体要么通过水肺潜水原位采集，要么在50米深处的沉积物捕集器中收集，要么由在模拟原位条件下于滚动圆筒中培养的天然湖水形成。对于后一种聚集体，还研究了微生物定殖的时间进程。天然聚集体和在滚动圆筒中形成的聚集体由湖中存在的颗粒有机物质组成，因此反映了周围浮游生物群落的组成。所检查的所有类型的湖雪聚集体都被微生物细胞大量定殖，每个聚集体中含有0.5×10⁶至＞2×10⁶个细胞。用4′,6-二脒基-2-苯基吲哚（DAPI）染色的微生物细胞中，有55%至100%可用细菌域特异性探针可视化。在大多数样本中，β-亚类变形菌在微生物群落中占主导地位，通过DAPI染色计数，占总细胞数的27%至42%，与聚集体的组成无关。在对实验室制备的聚集体进行的时间进程实验中，β-亚类变形菌的比例通常随时间增加。除了少数样本外，α-和γ-亚类变形菌的丰度远低于β-亚类变形菌，分别占总细胞数的11%至25%和9%至33%。因此，我们假设在聚集体上建立了一个特定的适应聚集体的微生物群落。由于天然聚集体和实验室制备聚集体上微生物群落的组成相似，我们得出结论，在滚动圆筒中形成的聚集体是研究宏观有机聚集体形成和微生物定殖的良好模型系统。
