Project description:Aquatic microbial communities contain a vast amount of genetic diversity and we have much to learn about how this manifests to functional diversity. Existing long-term time series data includes 16S tags, metagenomes, single amplified genomes (SAGs), and genomes from metagenomes (GFMs). Information about functional diversity and metabolic capabilities is often unavailable. The study sites include three lakes that are the subject of intense study through the North Temperate Lakes Long Term Ecological Research site: Sparkling Lake (oligotrophic), Lake Mendota (eutrophic), and Trout Bog Lake (dystrophic).
The work (proposal:https://doi.org/10.46936/10.25585/60000947) conducted by the U.S. Department of Energy Joint Genome Institute (https://ror.org/04xm1d337), a DOE Office of Science User Facility, is supported by the Office of Science of the U.S. Department of Energy operated under Contract No. DE-AC02-05CH11231.
Project description:Bacterium Sphingomonas glacialis AAP5 isolated from the alpine lake Gossenköllesee contains genes for anoxygenic phototrophy as well as proton-pumping xanthorhodopsin. Here we show that AAP5 expresses xanthorhodopsin when illuminated at temperatures below 16°C. In contrast bacteriochlorophyll-containing reaction centers are expressed between 4 and 22°C in the dark. Thus, cells grown at lower temperature under natural light-dark cycle produced both photosystems. The purified xanthorhodopsin contains carotenoid nostoxanthin serving as an auxiliary antenna and performs the standard photocycle. The xanthorhodopsin-containing cells reduced upon illumination their respiration, increased their ATP synthesis and produced more biomass. This documents that the harvested light energy was utilized in the metabolism, which can represent a competitive advance under carbon-limiting conditions. The presence of Sphingomonas bacteria with dual phototrophy was verified in the metagenomes collected from lake Gossenköllesee. This unique trait may represent a metabolic advantage in alpine lakes where photoheterotrophic organisms facelimited organic substrates, low temperature, and extreme changes in irradiance.
