Antimicrobial activity of endophytic bacterium strain B-11 isolated from Curcuma wenyujin

Abstract:

[Background] Endophytes are widely distributed in nature, and have great potential for further exploration and application. [Objective] To isolate and identify endophytic bacteria of Curcuma wenyujin and evaluate their antimicrobial activity. [Methods] Endophytic bacteria from rhizomeof C. wenyujin were separated using routine tissue-separation method and identified by 16S rRNA gene sequences analysis. Their antimicrobial activity against Colletotrichum gloeosporioides was tested by confront-culture method. Strain B-11. C. gloeosporioides was identified through morphological, physiological, biochemical characteristics and 16S rRNA gene sequences analysis. Its influence on the hyphae of 6 pathogenic fungi, belonging to different families, was detected. Its antimicrobial components were determined by 4 specific culture mediums and MALDI-TOF-MS. The control efficacy against C. gloeosporioides on Dendrobium officinale was analyzed by inoculation of leaves in vitro. [Results] Twenty-five strains of endophytic bacteria, belonging to 12 families, were isolated and Bacillus spp. were the dominant species account for 28%. Eight strains showed antagonistic effect against C. gloeosporioides. Bacillus velezensis strain B-11 inhibited the growth of 6 different pathogenic fungi, with the hyphae inflated, deformed and branches increased. It can produce diverse antifungal substances including protease, β-gluconase and siderophore and lipopeptide. Inoculation experiment in vitro found that the cell-free culture of it had a control efficacy of 64% against C. gloeosporioides on D. officinale. [Conclusion] Endophytic bacterium strain B-11 in the rhizome of Curcuma wenyujin is an efficient biocontrol agent with potential for antibiotics development.