Isolation of the Novel Strain Bacillus amyloliquefaciens F9 and Identification of Lipopeptide Extract Components Responsible for Activity against Xanthomonas citri subsp. citri.

Xin Wang,Liqiong Liang,Xiaoxin Ye,Lianhui Zhang,Yu Shi,Junxia Wang,Xiaoyun Chen,Xiaobei Yang,Hang Shao,Linghui Xu

doi:10.3390/plants11030457

Xin Wang, Liqiong Liang + Show 8 more

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https://doi.org/10.3390/plants11030457

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Abstract

Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a quarantine disease that seriously affects citrus production worldwide. The use of microorganisms and their products for biological control has been proven to be effective in controlling Xanthomonas disease. In this study, a novel Xcc antagonistic strain was isolated and identified as Bacillus amyloliquefaciens F9 by morphological and molecular analysis. The lipopeptide extract of B. amyloliquefaciens F9 (F9LE) effectively inhibited the growth of Xcc in an agar diffusion assay and restrained the occurrence of canker lesions in a pathogenicity test under greenhouse conditions. Consistent with these findings, F9LE treatment significantly inhibited the production of extracellular enzymes in Xcc cells and induced cell wall damage, with leakage of bacterial contents revealed by scanning electron microscopy and transmission electron microscopy analyses. In addition, F9LE also showed strong antagonistic activity against a wide spectrum of plant pathogenic bacteria and fungi. Furthermore, using electrospray ionization mass spectrometry analysis, the main antimicrobial compounds of strain F9 were identified as three kinds of lipopeptides, including homologues of surfactin, fengycin, and iturin. Taken together, our results show that B. amyloliquefaciens F9 and its lipopeptide components have the potential to be used as biocontrol agents against Xcc, and other plant pathogenic bacteria and fungi.

Highlights

Integrative Microbiology Research Centre, College of Plant Protection, South China Agricultural University, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou 510642, China
Luria–Bertani agar (LB) agar plates containing the pathogen Xanthomonas citri subsp. citri (Xcc) jx-6 as an indicator, the dual culture method was used to isolate and screen the microorganisms that inhibit the growth of Xcc
Citrus canker caused by the Gram-negative bacterium Xcc infects almost all citrus species [3,4] and poses a serious threat to all citrus-producing areas [2]

Summary

Introduction

Integrative Microbiology Research Centre, College of Plant Protection, South China Agricultural University, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou 510642, China. The lipopeptide extract of B. amyloliquefaciens F9 (F9LE) effectively inhibited the growth of Xcc in an agar diffusion assay and restrained the occurrence of canker lesions in a pathogenicity test under greenhouse conditions. 1. Introduction with regard to jurisdictional claims in Citrus canker is a serious bacterial citrus disease that causes significant economic losses in citrus-producing areas worldwide [1]. Introduction with regard to jurisdictional claims in Citrus canker is a serious bacterial citrus disease that causes significant economic losses in citrus-producing areas worldwide [1] This disease is caused by the Gram-negative bacterium Xanthomonas citri subsp. Iturin-like lipopeptides are essential components in the biocontrol library of B. subtilis against the cucurbit pathogenic bacterium X. campestris pv

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