Description and functional testing of four species of the novel phototrophic genus Chioneia gen. nov., isolated from different East Antarctic environments.

Seven Gram-negative, aerobic, non-sporulating, motile strains were isolated from terrestrial (R-67880T, R-67883, R-36501 and R-36677T) and aquatic (R-39604, R-39161T and R-39594T) East Antarctic environments (i.e. soil and aquatic microbial mats), between 2007 and 2014. Analysis of near-complete 16S rRNA gene sequences revealed that the strains potentially form a novel genus in the family Sphingomonadaceae (Alphaproteobacteria). DNA-DNA reassociation and average nucleotide identity values indicated distinction from close neighbors in the family Sphingomonadaceae and showed that the seven isolates form four different species. The main central pathways present in the strains are the glycolysis, tricarboxylic acid cycle and pentose phosphate pathway. The strains can use only a limited number of carbon sources and mainly depend on ammonia and sulfate as a nitrogen and sulfur source, respectively. The novel strains showed the potential of aerobic anoxygenic phototrophy, based on the presence of bacteriochlorophyll a pigments, which was corroborated by the presence of genes for all building blocks for a type 2 photosynthetic reaction center in the annotated genomes. Based on the results of phenotypic, genomic, phylogenetic and chemotaxonomic analyses, the strains could be assigned four new species in the novel genus Chioneia gen. nov. in the family Sphingomonadaceae, for which the names C. frigida sp. nov. (R-67880T, R-67883 and R-36501), C. hiemis sp. nov. (R-36677T), C. brumae sp. nov. (R-39161T and R-39604) and C. algoris sp. nov. (R-39594T) are proposed.