The Distribution of Some Genera of Filamentous Bacteria in Littoral and Profundal Lake Sediments

Freshwater Biological Association. Windermere Laboratory, The Ferry House, Ambleside, Cumbria LA22 0LP ABSTRACT The distribution of several genera of filamentous bacteria was determined in profundal and littoral sediments of three lakes of differing trophic status. The bacteria were tentatively identified on the basis of cytochemical tests and microscopic observations of organisms in wet mount preparations and on agar-coated and uncoated slides incubated in the sediment cores. The population density and the diversity of the filamentous bacteria increased with increasing nutrient content of the lakes. The general observations of higher numbers in the profundal than in the littoral zone and a decrease in population density with sediment depth were confirmed for most genera. Some of the genera may be microaerophiles. An affinity for surfaces was observed. Pseudanabaena usually occurred only in littoral samples and Beggiatoa only in the two richer lakes. Vitreoscilla was found mainly in the two richer lakes and Leptothrix was present in large numbers in all three lakes. Present address: Universidade Federal de São Carlos. Departamento de Ciências Biologicas, 13560 São Carlos SP, Brazil.