Two new psychrotolerant Massilia species inhibit plant pathogens Clavibacter and Curtobacterium

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 B2^T, Massilia rubra CCM 8692^T, Massilia frigida CCM 8695^T, Massilia antarctica CCM 8941^T, and Massilia aquatica CCM 8693^T. 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 P3689^T (= CCM 9206^T = LMG 33568^T) and P5043^T (= CCM 9029^T = LMG 32502^T), 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.