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 lep A 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.