Bacillus pumilus WP8 exhibits biocontrol efficacy against tomato bacterial wilt via attenuation of the virulence of the pathogenic bacterium
Bacillus pumilus WP8 exhibits biocontrol efficacy against tomato bacterial wilt via attenuation of the virulence of the pathogenic bacterium
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DOI：
10.1080/09064710.2017.1416663
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发表时间：
2018-07
期刊：
影响因子：
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通讯作者：
Min Shen;Dan Xia;Zhifeng Yin;Qing-xin Zhao;Yijun Kang
中科院分区：
文献类型：
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作者：
Min Shen;Dan Xia;Zhifeng Yin;Qing-xin Zhao;Yijun Kang
摘要短小芽孢杆菌WP8是一种促进植物生长的根瘤菌（PGPR），对番茄青枯病病原菌Ralstonia solanacearum Rs1115具有良好的生物防治效果。然而，生物防治不是由于病原菌的拮抗作用。因此，我们假设WP8的生物防治效果是通过降低Rs1115的毒力来实现的。本研究通过盆栽试验比较植株不同部位的Rs1115，研究WP8对植株地上部分Rs1115的抑制能力。通过显微检查和结晶紫染色检测WP8的初级和次级代谢物含量及其对Rs1115抽动和蜂群运动的抑制作用。采用定量PCR方法确定WP8代谢产物对Rs1115典型毒力基因表达的影响。接种后根际Rs1115丰度随接种时间增加而增加。而接种WP8后第3天和第6天芽体无病原体。接种后第9天，WP8 + Rs1115处理组茎部中Rs1115的丰度比Rs1115处理组高1.5 lg单位，而叶片中Rs1115的丰度较少。这表明WP8阻止了Rs1115向植株地上部分扩散。此外，WP8的一些耐热次生代谢产物（如脂肽）抑制了Rs1115的抽搐和群体运动。此外，代谢产物降低了Rs1115中典型毒力基因的表达。因此，WP8可能通过分泌pumilacidin来减弱Rs1115的毒力。
ABSTRACT Bacillus pumilus WP8 is a plant growth-promoting rhizobacterium (PGPR) with good biocontrol efficacy against tomato bacterial wilt caused by Ralstonia solanacearum Rs1115. Biocontrol, however, is not due to antagonism of the pathogenic bacterium. Thus, we hypothesised that the biocontrol efficacy of WP8 was achieved by attenuation of Rs1115 virulence. Here, pot experiments for comparison of Rs1115 in different plant parts were conducted to investigate the ability of WP8 to prevent entry of Rs1115 into the regions of the plant above ground. Primary and secondary metabolite contents of WP8 and their inhibitory effects on twitching and swarming motilities of Rs1115 were determined by microscopic examination and crystal violet staining. The effects of WP8 metabolites on the expression of typical virulence genes in Rs1115 were established by quantitative PCR. Rs1115 abundance in the rhizosphere increased with time after inoculation. However, the shoots treated with WP8 were pathogen-free on days 3 and 6 after inoculation. In the WP8 + Rs1115 treatment group, the abundance of Rs1115 in shoots was 1.5 lg units higher on day 9 post-inoculation than that in the Rs1115 treatment group, while less Rs1115 was observed in the leaves. This indicated that WP8 prevented Rs1115 from spreading to the regions of the plant above ground. Furthermore, some heat-resistant secondary metabolites of WP8 (e.g. lipopeptides) inhibited the twitching and swarming motility of Rs1115. Moreover, the metabolites decreased the expression of typical virulence genes in Rs1115. Therefore, WP8 was shown to attenuate Rs1115 virulence, possibly through pumilacidin secretion.