Enrichment of protective microbiota in the rhizosphere facilitates disease suppression. However, how the disruption of protective rhizobacteria affects disease suppression is largely unknown. Here, we analyzed the rhizosphere microbial community of a healthy and diseased tomato plant grown <30-cm apart in a greenhouse at three different locations in South Korea. The abundance of Gram-positive Actinobacteria and Firmicutes phyla was lower in diseased rhizosphere soil (DRS) than in healthy rhizosphere soil (HRS) without changes in the causative Ralstonia solanacearum population. Artificial disruption of Gram-positive bacteria in HRS using 500-μg/mL vancomycin increased bacterial wilt occurrence in tomato. To identify HRS-specific and plant-protective Gram-positive bacteria species, Brevibacterium frigoritolerans HRS1, Bacillus niacini HRS2, Solibacillus silvestris HRS3, and Bacillus luciferensis HRS4 were selected from among 326 heat-stable culturable bacteria isolates. These four strains did not directly antagonize R. solanacearum but activated plant immunity. A synthetic community comprising these four strains displayed greater immune activation against R. solanacearum and extended plant protection by 4 more days in comparison with each individual strain. Overall, our results demonstrate for the first time that dysbiosis of the protective Gram-positive bacterial community in DRS promotes the incidence of disease.

根际保护性微生物群的富集有利于疾病的抑制。然而，保护性根际细菌的破坏如何影响疾病抑制尚不清楚。在这里，我们分析了在韩国三个不同地点的温室中生长的健康和患病番茄植株的根际微生物群落，这些番茄植株的间距 < 30 厘米。患病根际土壤（DRS）中革兰氏阳性放线菌和厚壁菌门的丰度低于健康根际土壤（HRS），而致病青枯菌种群没有变化。使用 500 μg/mL 万古霉素人工破坏 HRS 中的革兰氏阳性菌会增加番茄青枯病的发生。为了鉴定 HRS 特异性和植物保护性革兰氏阳性菌种类，从 326 个热稳定可培养细菌分离株中选择了冷短杆菌HRS1、烟酸芽孢杆菌HRS2、银芽孢杆菌HRS3 和荧光芽孢杆菌HRS4。这4株菌株并不直接拮抗青枯菌，而是激活植物免疫。与每个单独菌株相比，由这四种菌株组成的合成群落表现出更强的针对青枯菌的免疫激活作用，并将植物保护期延长了 4 天。总体而言，我们的结果首次证明 DRS 中保护性革兰氏阳性菌群落的失调会促进疾病的发生。