Peloploca fibrata is an aggregate-forming bacterium that was first described in 1956 by Skuja in Swedish Lapland. In the aggregates, which can consist of more than 1000 individual cells, the bacteria are arranged in filaments. These filaments in turn are arranged in bundles of varying thickness and length to form the aggregate (s. figs. 1 a-b, 2 and 3).

I find Peloploca fibrata regularly, but never frequently in the Simmelried. I have not yet been able to find this bacterium in my other sampling sites. Peloploca fibrata is almost always associated with rhodobacteria. Since the aggregates of Peloploca fibrata are very long (up to 1 mm), they are immediately noticeable in the samples even at low magnifications. In the aggregates of my population, the individual cells in the filaments were not or only indistinctly recognizable, as Skuja has already described. I only found a few aggregates in which the boundaries of individual cells could be clearly seen (s. figs. 4 and 5). They were almost always aggregates with only a few filaments. The individual cells may be easier to recognize in the growth phase of the aggregates. In such aggregates it can be seen that the cylindrical bacteria in the filaments have very different lengths, which is also described by Skuja. Important characteristics of Peloploca fibrata are that there are no constrictions between the individual cells and that the cells do not contain gas vacuoles. This distinguishes Peloploca fibrata from Peloploca taeniata.