Paraburkholderia dioscoreae sp. nov., a novel plant associated growth promotor.

A novel bacterium, designated strain Msb3T, was recently isolated from leaves of the yam family plant Dioscorea bulbifera (Dioscoreaceae). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that this strain belonged to the genus Paraburkholderia with Paraburkholderia xenovorans as nearest validly named neighbour taxon (99.3 % sequence similarity towards the P. xenovorans type strain). Earlier genome sequence analysis revealed a genome of 8.35 Mb in size with a G+C content of 62.5 mol%, which was distributed over two chromosomes and three plasmids. Here, we confirm that strain Msb3T represents a novel Paraburkholderia species. In silico DNA-DNA hybridization and average nucleotide identity (OrthoANIu) analyses towards P. xenovorans LB400T yielded 58.4 % dDDH and 94.5 % orthoANIu. Phenotypic and metabolic characterization revealed growth at 15 °C on tryptic soy agar, growth in the presence of 1 % NaCl and the lack of assimilation of phenylacetic acid as distinctive features. Together, these data demonstrate that strain Msb3T represents a novel species of the genus Paraburkholderia, for which we propose the name Paraburkholderia dioscoreae sp. nov. The type strain is Msb3T (=LMG 31881T, DSM 111632T, CECT 30342T).

The Potato Yam Phyllosphere Ectosymbiont Paraburkholderia sp. Msb3 Is a Potent Growth Promotor in Tomato.

The genus Paraburkholderia includes a variety of species with promising features for sustainable biotechnological solutions in agriculture through increasing crop productivity. Here, we present a novel Paraburkholderia isolate, a permanent and predominant member of the Dioscoreae bulbifera (yam family, Dioscoreaceae) phyllosphere, making up to 25% of the microbial community on leaf acumens. The 8.5 Mbp genome of isolate Msb3 encodes an unprecedented combination of features mediating a beneficial plant-associated lifestyle, including biological nitrogen fixation (BNF), plant hormone regulation, detoxification of various xenobiotics, degradation of aromatic compounds and multiple protein secretion systems including both T3SS and T6SS. The isolate exhibits significant growth promotion when applied to agriculturally important plants such as tomato, by increasing the total dry biomass by up to 40%. The open question about the "beneficial" nature of this strain led us to investigate ecological and generic boundaries in Burkholderia sensu lato. In a refined phylogeny including 279 Burkholderia sensu lato isolates strain Msb3 clusters within Clade I Paraburkholderia, which also includes few opportunistic strains that can potentially act as pathogens, as revealed by our ecological meta-data analysis. In fact, we demonstrate that all genera originating from the "plant beneficial and environmental" (PBE) Burkholderia species cluster include opportunists. This indicates that further functional examinations are needed before safe application of these strains in sustainable agricultural settings can be assured.