Phylogenetic affiliations and physiological traits of freshwater bacteria

Joan Petersen, Fordham University


The purpose of this research was to examine the structure and function of freshwater microbial communities. A total of 124 bacterial isolates were purified in culture from Calder and Rye Lakes (NY) and found to be both physiologically and phylogenetically diverse. In addition, 16S rDNA sequence analysis showed that many of the bacterial isolates obtained in this study represented previously undescribed species. Novel 16S rDNA sequences were also obtained from whole communities (uncultured cells) in a gene clone survey of Calder Lake. This research demonstrated that both traditional isolation methods and gene clones surveys reveal novel bacterial types. The major bacterial groups detected by both methods included Cytophagales, actinomycetes, and proteobacteria. This study also examined the effects of experimental additions of organic carbon substrates on Calder Lake microbial communities. Both leaf and macrophyte detritus additions resulted in significant effects on the physiological properties of microbial communities. Each of the treatments showed a unique pattern of differences (as compared to controls), indicating a substrate-specific response to the organic carbon additions. The differences in community physiological properties were not reflected in shifts in total bacterial densities. Shifts in the physiological properties of total microbial communities were linked to shifts in microbial community structure, as revealed by DNA hybridization assays. Oligonucleotide probes specific to five bacterial subclasses revealed significant differences in microbial community structure between control treatments and those amended with macrophyte and terrestrial leaves. These results indicate that the physiological responses to organic carbon additions are likely due to shifts in species composition. Hybridization assays were also used to compare the community composition of free-living microbial cells to those associated with the aquatic macrophyte Vallisneria americana. Domain-level probes indicated that eubacteria were the predominant cell type among free-living communities, whereas eukaryotes (algae) comprised the majority of microorganisms attached to macrophyte leaves. Archaeal cells (previously thought to inhabit only extreme environments) were detected in both communities, but were more abundant among free-living microbial communities.

Subject Area

Ecology|Microbiology|Freshwater ecology

Recommended Citation

Petersen, Joan, "Phylogenetic affiliations and physiological traits of freshwater bacteria" (1999). ETD Collection for Fordham University. AAI9926911.