Ligninolytic Capabilities of Indigenous Bacteria Isolated from Reynoutria Japonica Rhizosphere: A Potential Mechanism Enhancing Plant Invasiveness

Abstract

Japanese knotweed (Reynoutria japonica), an invasive alien plant species (IAPS) from East Asia, has spread to Europe and North America, threatening native ecosystems. Its invasiveness is linked to aggressive growth, resilience, and allelopathic phenolic compounds released by the plant or produced by its rhizosphere microbiome from lignin. Five lignin-degrading Paraburkholderia spp. strains isolated from the R. japonica rhizosphere and degraded (1) alkali lignin, (2) lignin from R. japonica biomass, and (3) lignin from R. japonica black liquor. Lignin degradation was most effective in plant biomass, producing hydroxycinnamic, nonanoic, and octanoic acids intermediates, potentially contributing to R. japonica invasiveness. Genome analysis of Paraburkholderia spp. L4 strain revealed beta-ketoadipate and phenylpropanoid metabolic pathways but lacked common lignin-degrading enzymes (laccase, lignin-, and manganese peroxidase), confirming Paraburkholderia’s role in IAPS promotion.

Keywords: Invasive alien plant species, lignin, allelopathy, Paraburkholderia spp., Japanese knotweed