Three bacterial strains producing blue-violet pigmented colonies on R2A agar were isolated from a wet rock wall and lakes in the deglaciated northern part of James Ross Island, Antarctica. The isolated strains inhibited phytopathogenic Gram-positive bacteria Clavibacter spp., Curtobacterium flacumfaciens, and Paenarthrobacter ilicis. Phylogenetic analysis based on the 16S rRNA gene indicated that the isolates belonged to the genus Massilia and the closest relatives were Massilia violaceinigra B2T, Massilia rubra CCM 8692T, Massilia frigida CCM 8695T, Massilia antarctica CCM 8941T, and Massilia aquatica CCM 8693T. A polyphasic taxonomic study based on lepA genes sequencing, automated ribotyping, MALDI-TOF MS, chemotaxonomy analyses, extensive biotyping, average nucleotide identity, and digital DNA-DNA hybridization calculations based on whole-genome sequences proved that the isolates represent a novel Massilia species for which the names Massilia pseudoviolaceinigra sp. nov. and Massilia scottii sp. nov. are suggested, with the type strains P3689T (= CCM 9206T = LMG 33568T) and P5043T (= CCM 9029T = LMG 32502T), respectively. These two bioactive metabolite-producing species may play an important role in shaping the composition of fresh-water Antarctic microbiomes due to the inhibition of various Gram-positive bacteria.

• Keywords
• Clavibacter, Curtobacterium, Massilia, Antarctica, Plant-pathogenic, Taxonomic description,
• MeSH
• Actinobacteria MeSH
• Biological Control Agents * isolation & purification   metabolism   MeSH
• Clavibacter * pathogenicity   MeSH
• DNA, Bacterial genetics   isolation & purification   MeSH
• Extremophiles * classification   genetics   isolation & purification   metabolism   MeSH
• Phylogeny MeSH
• Plant Diseases * microbiology   prevention & control   MeSH
• Oxalobacteraceae * classification   genetics   isolation & purification   metabolism   MeSH
• RNA, Ribosomal, 16S genetics   MeSH
• Whole Genome Sequencing MeSH
• Fresh Water microbiology   MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Antarctic Regions MeSH
• Names of Substances
• Biological Control Agents * MeSH
• DNA, Bacterial MeSH
• RNA, Ribosomal, 16S MeSH

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, gyrB and lepA 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 P8398T 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 gyrB and lepA sequencing results showed the novelty of the analysed group, and the average nucleotide identity and digital DNA-DNA hybridisation values clearly proved that P8398T 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 P8398T (= CCM 8941T = LMG 32108T).

• Keywords
• Antarctica, Massilia, description, psychrophilic, violacein, whole-genome sequencing,
• Publication type
• Journal Article MeSH