Aerobic Anoxygenic Photosynthesis Is Commonly Present within the Genus Limnohabitans

Abstract

The genus <i>Limnohabitans</i> (<i>Comamonadaceae</i>, <i>Betaproteobacteria</i>) 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 genes <i>pufLM</i> and <i>bchY</i> in 28 of 46 strains from three <i>Limnohabitans</i> lineages. The <i>pufM</i> sequences obtained are very closely related to environmental <i>pufM</i> sequences detected in various freshwater habitats, indicating the ubiquity and potential importance of photoheterotrophic <i>Limnohabitans</i> in nature. Additionally, we sequenced and analyzed the genomes of 5 potentially photoheterotrophic <i>Limnohabitans</i> strains, to gain further insights into their phototrophic capacity. The structure of the photosynthesis gene cluster turned out to be highly conserved within the genus <i>Limnohabitans</i> and also among all potentially photosynthetic <i>Betaproteobacteria</i> strains. The expression of photosynthetic complexes was detected in a culture of <i>Limnohabitans planktonicus</i> II-D5^T using spectroscopic and pigment analyses. This was further verified by a novel combination of infrared microscopy and fluorescent <i>in situ</i> hybridization.<b>IMPORTANCE</b> The data presented document that the capacity to perform anoxygenic photosynthesis is common among the members of the genus <i>Limnohabitans</i>, indicating that they may have a novel role in freshwater habitats.