A novel gliding filamentous bacterium Herpetosiphon tianshanensis sp. nov. NSE202 is a promising biocontrol agent for fire blight.

BACKGROUND

Fire blight (Erwinia amylovora), a devastating bacterial disease, has posed significant challenges to apple and pear production for more than a century. In recent years, the spread of fire blight to China via Xinjiang has heightened concerns among planters and government authorities, particularly given the region's distinct geography and climate, underscoring the urgent need for innovative biocontrol strategies.

RESULTS

This study introduced a predatory bacterium, Herpetosiphon tianshanensis sp. nov. NSE202, isolated from natural forest soil in Xinjiang, China, that could be a new type of promising biological control agent for the management of fire blight. Strain NSE202 differs from the five other reported Herpetosiphon species in terms of its physiological characteristics and genomic composition. Using morphological, 16S ribosomal RNA gene and whole-genome analysis, the NSE202 strain was assigned to H. tianshanensis sp. nov. Strain NSE202 demonstrated strong predatory capability against Erwinia amylovora (Ea) in vitro. The biocontrol capacity of NSE202 was assayed on isolated inflorescences of fragrant pear and biennial potted pear seedlings under greenhouse conditions. The protective control efficacy of NSE202 was 64.8% in the inflorescences assay. Bacterial spraying of NSE202 significantly reduced the incidence and disease index on pear seedlings with protective and therapeutic control efficacies of 71.9% and 61.5%, respectively. Strain NSE202 demonstrated stable colonization on pear blossoms and twigs under greenhouse conditions. The pathogen population was suppressed significantly in planta treated with NSE202, as shown by colony counts on plates, scanning electron microscopy, and quantitative polymerase chain reaction analysis. Further investigation demonstrated that secondary metabolites of strain NSE202, collected via macroporous resin, and extracellular proteins, precipitated using ammonium sulfate, had pronounced lytic activity against the fire blight pathogen. In addition, certain lipases, glycoside hydrolases, and peptidases secreted by strain NSE202 may contribute significantly to the predation process. These findings suggest that such components may serve as promising biocontrol factors.

CONCLUSIONS

The discovery of H. tianshanensis sp. nov. NSE202 provides a new and promising strategy for combating fire blight. The isolates' multiple capacities to colonize and exert antagonistic effects against Erwinia amylovora makes them highly promising candidates for an integrated biological solution. © 2025 Society of Chemical Industry.