Deng Jundan, Xu Weikang, Lv Guochang, Yuan Hang, Zhang Qing-He, Wickham Jacob D, Xu Letian, Zhang Longwa
Anhui Provincial Key Laboratory of Microbial Control, Anhui Agricultural University, Hefei, 230036, China.
State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, China.
Environ Microbiome. 2022 Sep 9;17(1):47. doi: 10.1186/s40793-022-00443-z.
The entomopathogenic Beauveria bassiana is a popular fungus used to control the Japanese pine sawyer, Monochamus alternatus Hope, the key vector of pine wood nematode (Bursaphelenchus xylophilus) that is the causal agent of pine wilt disease, resulting in devastating losses of pines in China and Portugal. However, recent studies have demonstrated that some insect-associated bacteria might decrease fungal toxicity and further undermine its biological control efficacy against M. alternatus. Thus, it is of great significance to uncover whether and how associated bacteria of M. alternatus become involved in the infection process of B. bassiana.
Here, we show that axenic M. alternatus larvae died significantly faster than non-axenic larvae infected by four increasing concentrations of B. bassiana spores (Log-rank test, P < 0.001). The infection of B. bassiana significantly changed the richness and structure of the beetle-associated bacterial community both on the cuticle and in the guts of M. alternatus; meanwhile, the abundance of Pseudomonas and Serratia bacteria were significantly enriched as shown by qPCR. Furthermore, these two bacteria genera showed a strong inhibitory activity against B. bassiana (One-way ANOVA, P < 0.001) by reducing the fungal conidial germination and growth rather than regulating host immunity.
This study highlights the role of insect-associated bacteria in the interaction between pest insects and entomopathogenic fungi, which should be taken into consideration when developing microbial-based pest control strategies.
昆虫病原球孢白僵菌是一种常用真菌，用于防治日本松墨天牛，即松材线虫（松材线虫病的致病因子）的关键传播媒介，松材线虫病在中国和葡萄牙导致松树遭受毁灭性损失。然而，最近的研究表明，一些与昆虫相关的细菌可能会降低真菌毒性，并进一步削弱其对松墨天牛的生物防治效果。因此，揭示松墨天牛的相关细菌是否以及如何参与球孢白僵菌的感染过程具有重要意义。
在这里，我们表明，无菌条件下的松墨天牛幼虫比受四种浓度递增的球孢白僵菌孢子感染的非无菌幼虫死亡速度明显更快（对数秩检验，P < 0.001）。球孢白僵菌的感染显著改变了松墨天牛体表和肠道中与甲虫相关的细菌群落的丰富度和结构；同时，通过定量PCR显示，假单胞菌属和沙雷氏菌属的丰度显著增加。此外，这两个细菌属通过降低真菌分生孢子的萌发和生长而不是调节宿主免疫力，对球孢白僵菌表现出强烈的抑制活性（单因素方差分析，P < 0.001）。
本研究强调了与昆虫相关的细菌在害虫与昆虫病原真菌相互作用中的作用，在制定基于微生物的害虫防治策略时应予以考虑。
