Ligninolytic capabilities of indigenous Paraburkholderia sp. isolated from Reynoutria japonica rhizosphere: a potential mechanism enhancing plant invasiveness

Invasive alien plant species (IAPS) Japanese knotweed ( Reynoutria japonica ), native to East Asia, has spread to Europe, North America and other regions posing a threat to the indigenous species and ecosystems. Its invasion can be, among the aggressive growth, resilience and lack of predators, attributed to the phenolic compounds released by the plant or produced by the rhizosphere microbiome from lignin. We, therefore, isolated five lignin degrading Paraburkholderia spp. strains from the R. japonica rhizosphere and identified lignin degradation from three sources: (1) alkali lignin, (2) lignin from R. japonica plant biomass and (3) lignin from R. japonica black liquor. Furthermore, the degradation of lignin in R. japonica plant biomass was significantly more effective compared to alkali lignin. The accumulation of compounds such as hydroxycinnamic acid, nonanoic acid, and octanoic acid after degradation suggests that bacteria can partially break down lignin into intermediates, which may contribute to R. japonica invasiveness. Genome annotation analysis of the L4 strain further confirmed the ability of Paraburkholderia spp. to produce phenolic and other compounds involved IAPS promotion. Beta-ketoadipate and phenylpropanoid metabolic pathway were found to be predominant, with the lack of common lignin degrading enzymes (laccase, lignin- and manganese peroxidase).