Xanthomonas bundabergensis sp. nov., Xanthomonas medicagonis sp. nov. and Xanthomonas tesorieronis sp. nov.: three members of group 1 Xanthomonas.

Abstract

Between 1976 and 2010, four bacterial isolates were collected in New South Wales and Queensland, Australia, and stored as part of routine biosecurity surveillance. Recently, these historic isolates were analysed as part of a larger project to enhance the taxonomic accuracy of our culture collection and improve Australia's biosecurity preparedness. Three isolates were collected from Fragaria × ananassa, initially identified as Xanthomonas sp., and one from Medicago sativa, identified as Xanthomonas axonopodis subsp. alfalfae. In this study, we employed modern phenotypic and genomic techniques to further characterize these isolates. Matrix-assisted laser desorption ionization-time of flight MS biotyping and Biolog GEN III MicroPlates confirmed that they are members of the Xanthomonas genus but did not allow for species-level classification. Genome-relatedness indices and phylogenetic analysis confirmed that they were Xanthomonas and revealed that they represent three novel species. The maximum average nucleotide identity and digital DNA-DNA hybridization values observed when comparing the four isolates to all Xanthomonas type strains and each other were 93.9% and 50.7%, respectively. Pathogenesis assays confirmed that two of the isolates are not pathogenic to Fragaria, the plant from which they were isolated. Based on these findings, we propose the names Xanthomonas bundabergensis sp. nov. (DAR 80977^T=ICMP 24943), Xanthomonas medicagonis sp. nov. (DAR 35659^T=ICMP 24942) and Xanthomonas tesorieronis sp. nov. (DAR 34887^T=ICMP 24940).