Prosthecate aerobic anoxygenic phototrophs Photocaulis sulfatitolerans gen. nov. sp. nov. and Photocaulis rubescens sp. nov. isolated from alpine meromictic lakes in British Columbia, Canada.

Seven Gram-negative flagellated and subsequent prosthecate bacteria were isolated from meromictic Mahoney Lake and Blue Lake in British Columbia, Canada. Each became pink-red after 1-2 weeks of incubation, containing bacteriochlorophyll a incorporated into light harvesting and reaction center pigment-protein complexes. They did not grow anaerobically under illuminated conditions, supporting their identification as obligate aerobic anoxygenic phototrophs (AAP). All isolates preferred high salinity and BL14 T tolerated up to 6.5% NaCl or 16.0% Na 2 SO 4 . In addition to phenotypic differences, analysis of 16S rRNA gene sequences found both strains BL14 T and ML37 T were related to Alkalicaulis satelles, G-192 T by 98.41 and 98.84%, respectively, and distantly associated to members of the non-phototrophic genus Glycocaulis profundi, ZYF765 T (95.59 and 95.36%, respectively) within the newly recognized Maricaulales order of α-Proteobacteria. BL14 T and ML37 T contained photosynthetic operons of 46,143 and 46,315 bp, where genes of BL14 T were uniquely split into two distal operons. Furthermore, A. satelles was not originally published as an AAP, but was also found in this work to contain a similar 45,131 bp fragment. The distinct morphological features, physiological traits and genomic analysis including average nucleotide identity and digital DNA:DNA hybridization of circularized genomes supported the proposal of new genus and species Photocaulis sulfatitolerans gen. nov. sp. nov., type strain BL14 T and Photocaulis rubescens sp. nov. type strain ML37 T .