Isolation, identification, and antimicrobial activities of myxobacteria in primitive forest of Tianshan Grand Canyon

Abstract:

[Background] Myxobacteria are a group of higher prokaryotes with social behavior. They are versatile predators that prey on phytopathogenic fungi and bacteria, serving as excellent candidates for biocontrol agents. [Objective] To explore the diversity and antimicrobial activities of culturable myxobacteria in the primitive forest of Tianshan Grand Canyon in Urumqi, and lay a foundation for the discovery of myxobacteria strains for biocontrol. [Methods] Culturable myxobacteria were isolated from the soil and rotting wood samples collected from the primitive forest of Tianshan Grand Canyon by the rabbit dung pellets-inducing method and prey-inducing method. The isolates were identified based morphological characteristics, physiological and biochemical properties, and the 16S rRNA gene sequences. The antimicrobial activities of the isolates were determined with 6 phytopathogenic fungal species (Verticillium dahliae, Fusarium oxysporum f. sp. vasinfectum, Fusarium verticillioides, Rhizoctonia solani, Fusarium culmorum, and Alternaria tenuissima) and 1 phytopathogenic bacterial species (Erwinia amylovora) by plate confrontation method and lawn predation method. [Results] Seventy potential strains were isolated from the collected samples, and 36 pure cultures of myxobacteria were obtained after purification. The 36 strains belonged to 4 genera: Myxococcus (30 strains), Cystobacter (3 strains), Corallococcus (2 strains), and Archangium (1 strain). The 36 strains of myxobacteria presented activities against at least two species of phytopathogenic fungi, exhibiting broad-spectrum antifungal activities. One strain NSE37-1 with both broad-spectrum efficient antifungal activity was screened out. Fifteen strains had predatory activity against E. amylovora, and one strain NSE25 with strong predatory activity was screened out. [Conclusion] The culturable myxobacteria are abundant in Tianshan Grand Canyon, among which Myxococcus is the dominant genus. The isolated and purified myxobacteria strains all exhibited broad-spectrum activities against phytopathogens, demonstrating the value for research in the future.