Meridianimarinicoccus lucivorans sp. nov. and Roseovarius manitobensis sp. nov., New Halophilic Aerobic Anoxygenic Phototrophs from the Saline Springs of Lake Winnipegosis Region in Canada

Two light-pink coloured, gram-negative bacterial strains MS613T and MS785T were isolated from the waters of saline springs located near Lake Winnipegosis, Manitoba, Canada. The presence of bacteriochlorophyll a incorporated into reaction centres and light-harvesting I complexes, along with no anaerobic or photoautotrophic growth, supports classification as aerobic anoxygenic phototrophs. Similarity based on 16S rRNA identified Meridianimarinicoccus zhengii (98.65%), M. roseus (97.70%), and M. aquatilis (94.98%) as the closest relatives to MS613T. For MS785T, they are chemolithoautotroph Roseovarius autotrophicus (97.94%), heterotroph R. nitratireducens (96.58%), and aerobic anoxygenic phototroph R. tolerans (95.92%). Its proximity to these physiologically distinct species is captured by the presence of anoxygenic photosynthesis alongside encoding all Calvin cycle genes, despite not growing autotrophically. The designation of both as new species is supported by differences in their photosynthetic capability, salt tolerance, colony colour, and cell shape compared to closest relatives. Additionally, each strain had low average amino acid identity (<95%), average nucleotide identity (<95%), and digital DNA-DNA hybridization (<70%) in comparison to other members of Roseobacteraceae. Thus, we propose that strains MS613T (=NCIMB 15650T =DSM 122955T) and MS785T (=NCIMB 15651T =DSM 122954T) be classified as new species with the names Meridianimarinicoccus lucivorans sp. nov. and Roseovarius manitobensis sp. nov.