Bacterioplankton compositions of lakes and oceans: a first comparison based on fluorescence in situ hybridization

Abstract

Fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes was used to investigate the phylogenetic composition of bacterioplankton communities in several freshwater and marine samples. An average of about 50% of the cells were detected by probes for the domains Bacteria and Archaea, and of these, about half could be identified at the subdomain level with a set of group-specific probes. Beta subclass proteobacteria constituted a dominant fraction in freshwater systems, accounting for 16% (range, 3 to 32%) of the cells, although they were essentially absent in the marine samples examined. Members of the Cytophaga-Flavobacterium cluster were the most abundant group detected in the marine systems, accounting for 18% (range, 2 to 72%) of the 4',6-diamidino-2-phenylindole (DAPI) counts, and they were also important in freshwater systems (7%, range 0 to 18%). Furthermore, members of the alpha and gamma subclasses of Proteobacteria as well as members of the Planctomycetales were detected in both freshwater and marine water in abundances <7%.

FIG. 1

(A) Depth profile from the Baltic Sea. The bars show the total abundances of members of the beta subclass of the proteobacteria as revealed with probe BET42a. The line indicates the salinity. (B and C) Depth profiles from Lake Grosser Ostersee (B) and Lake Lago di Cadagno (C). The bars show the total abundances of the Cytophaga-Flavobacterium group as revealed with probe CF319a.