Representative Freshwater Bacterioplankton Isolated from Crater Lake, Oregon

Abstract

High-throughput culturing (HTC) methods that rely on dilution to extinction in very-low-nutrient media were used to obtain bacterial isolates from Crater Lake, Oregon. 16S rRNA sequence determination and phylogenetic reconstruction were used to determine the potential ecological significance of isolated bacteria, both in Crater Lake and globally. Fifty-five Crater Lake isolates yielded 16 different 16S rRNA gene sequences. Thirty of 55 (55%) Crater Lake isolates had 16S rRNA gene sequences with 97% or greater similarity to sequences recovered previously from Crater Lake 16S rRNA gene clone libraries. Furthermore, 36 of 55 (65%) Crater Lake isolates were found to be members of widely distributed freshwater groups. These results confirm that HTC is a significant improvement over traditional isolation techniques that tend to enrich for microorganisms that do not predominate in their environment and rarely correlate with 16S rRNA gene clone library sequences. Although all isolates were obtained under dark, heterotrophic growth conditions, 2 of the 16 different groups showed evidence of photosynthetic capability as assessed by the presence of puf operon sequences, suggesting that photoheterotrophy may be a significant process in this oligotrophic, freshwater habitat.

Fate of Heterotrophic Microbes in Pelagic Habitats: Focus on Populations

“…This appears to create a favorable conceptual environment for a population-based perspective in aquatic microbial ecology. Already, the analysis of genomic information has strengthened the interest in the cultivation of abundant heterotrophic microbes from the water column (39,63,110,204,238). Such activities will probably draw increased attention to the unique physiological features of different genotypes and thus to the potential ecological differences between cooccurring microbial populations in mixed assemblages.…”

Distribution of aerobic anoxygenic phototrophic bacteria in glacial lakes of northern Europe

“…The first freshwater AAP species were isolated from alkaline mat surfaces by Yurkov & Gorlenko (1990, 1992. Later, the presence of AAP species in limnic habitats was documented by the isolation of several AAP bacteria strains from various freshwater lakes (Page et al 2004, Gich & Overmann 2006. The existence of freshwater AAP species was also proven using culture-independent techniques.…”

The phrA gene of Rhodobacter sphaeroides encodes a photolyase and is regulated by singlet oxygen and peroxide in a σ E-dependent manner

“…R. sphaeroides uses light for anoxygenic photosynthesis but can also perform aerobic or anaerobic respiration. As a free-living aquatic bacterium, R. sphaeroides is exposed to sunlight in its natural habitat (Page et al, 2004). However, solar radiation of high intensity is harmful due to the formation of DNA photoproducts.…”