Identifying phenotypic and genetic traits for assessing pathogenic potential and biocontrol capacity in Burkholderia sensu lato strains.

In the 1990s, several Burkholderia strains were registered as biocontrol agents but later withdrawn after opportunistic infections were reported. Phylogenetic revisions now separate the group into Burkholderia sensu stricto (s.s.), including environmental and clinical strains with elevated pathogenic potential, and several newly established genera, largely presumed harmless. We analysed 76 Burkholderia sensu lato (s.l.; taxa formerly classified as Burkholderia) for pathogenic potential in a Galleria mellonella model, in vitro biocontrol activity, and phenotypic traits linked to virulence or environmental fitness. Proteolytic activity and siderophore production manifested in strains with higher pathogenic potential, whereas oxalate utilization and other environmental traits correlated with lower pathogenic potential. Whereas most pathogenic strains belonged to B. s.s., some Paraburkholderia isolates also exhibited elevated pathogenic potential. Transfer of the ornibactin biosynthetic cluster from a clinical Burkholderia strain to environmental Paraburkholderia sacchari increased pathogenic potential without affecting biocontrol capacity or persistence, illustrating the fine line between safe and hazardous strains. Collectively, our results identify novel phenotypic traits and genetic markers that enable improved, strain-level evaluation of pathogenic potential and biocontrol capacity, supporting the rational selection or engineering of Burkholderia s.l. strains for safe agricultural applications.