Taxonomic Re-Evaluation and Genomic Comparison of Novel Extracellular Electron Uptake-Capable Rhodovulum visakhapatnamense and Rhodovulum sulfidophilum isolates

Rhodovulum spp. are anoxygenic photosynthetic purple bacteria with versatile metabolisms, including the ability to obtain electrons from minerals in their environment to drive photosynthesis, a relatively novel process called phototrophic extracellular electron uptake (pEEU). Recently, our group isolated 15 strains of R. sulfidophilum to observe this metabolism in marine phototrophs. Our group previously observed carbon dioxide fixation coupled to phototrophic iron oxidation (photoferrotrophy) and pEEU in AB26 and identified a novel di-heme c¬-type cytochrome EeuP important for pEEU but not photoferrotrophy. Taxonomic re-evaluation based on 16S and pufM phylogenetic analyses led us to re-classify two isolates, AB26 and AB19, as Rhodovulum visakhapatnamense. The AB26 genome consists of 4,380,746 base-pairs, including two plasmids, and encodes 4,296 predicted protein-coding genes. AB26 contains 22 histidine kinases, 20 response regulators, and dedicates ~16% of its genome to transport. Transcriptomic data under aerobic, photoheterotrophy, photoautotrophy, and pEEU reveals how gene expression varies between metabolisms. Lastly, we use transcriptomic data for a comparative genomic analysis of potential pEEU-relevant genes between all 15 isolates. With these data we identify potential pEEU capable phototrophs within these isolates, and likely molecular mechanisms of pEEU.