Aerobic Anoxygenic Photosynthesis Is Commonly Present within the Genus Limnohabitans

The genusLimnohabitans (Comamonadaceae ,Betaproteobacteria ) is a common and a highly active component of freshwater bacterioplanktonic communities. To date, the genus has been considered to contain only heterotrophic species. In this study, we detected the photosynthesis genespufLM andbchY in 28 of 46 strains from threeLimnohabitans lineages. ThepufM sequences obtained are very closely related to environmentalpufM sequences detected in various freshwater habitats, indicating the ubiquity and potential importance of photoheterotrophicLimnohabitans in nature. Additionally, we sequenced and analyzed the genomes of 5 potentially photoheterotrophicLimnohabitans strains, to gain further insights into their phototrophic capacity. The structure of the photosynthesis gene cluster turned out to be highly conserved within the genusLimnohabitans and also among all potentially photosyntheticBetaproteobacteria strains. The expression of photosynthetic complexes was detected in a culture ofLimnohabitans planktonicus II-D5T using spectroscopic and pigment analyses. This was further verified by a novel combination of infrared microscopy and fluorescentin situ hybridization.IMPORTANCE The data presented document that the capacity to perform anoxygenic photosynthesis is common among the members of the genusLimnohabitans , indicating that they may have a novel role in freshwater habitats.