Characterisation of Waterborne Psychrophilic Massilia Isolates with Violacein Production and Description of Massilia antarctica sp. nov.

A group of seven bacterial strains producing blue-purple pigmented colonies on R2A agar was isolated from freshwater samples collected in a deglaciated part of James Ross Island and Eagle Island, Antarctica, from 2017-2019. The isolates were psychrophilic, oligotrophic, resistant to chloramphenicol, and exhibited strong hydrolytic activities. To clarify the taxonomic position of these isolates, a polyphasic taxonomic approach was applied based on sequencing of the 16S rRNA, gyr B and lep A genes, whole-genome sequencing, rep-PCR, MALDI-TOF MS, chemotaxonomy analyses and biotyping. Phylogenetic analysis of the 16S rRNA gene sequences revealed that the entire group are representatives of the genus Massilia . The closest relatives of the reference strain P8398 T were Massilia atriviolacea , Massilia violaceinigra , Massilia rubra , Massilia mucilaginosa , Massilia aquatica , Massilia frigida , Massilia glaciei and Massilia eurypsychrophila with a pairwise similarity of 98.6-100% in the 16S rRNA. The subsequent gyr B and lep A sequencing results showed the novelty of the analysed group, and the average nucleotide identity and digital DNA-DNA hybridisation values clearly proved that P8398 T represents a distinct Massilia species. After all these results, we nominate a new species with the proposed name Massilia antarctica sp. nov. The type strain is P8398 T (= CCM 8941 T = LMG 32108 T ).