共生生物的抗生素促进对鳞翅目昆虫肠道菌群的控制

Title：
Symbiont-Derived Antimicrobials Contribute to the Control of the Lepidopteran Gut Microbiota

DOI：
10.1016/j.chembiol.2016.11.015

Abstract：
Insects develop efficient antimicrobial strategies to flourish in a bacterial world. It has long been proposed that native gut microbiota is an important component of host defense; however, the responsible species have rarely been isolated to elucidate the mechanism of action. Here we show that the dominant symbiotic bacterium Enterococcus mundtii associated with the generalist herbivore Spodoptera littoralis actively secretes a stable class IIa bacteriocin (mundticin KS) against invading bacteria, but not against other gut residents, facilitating the normal development of host gut microbiota. A mundticin-defective strain lost inhibitory activity. Furthermore, purified mundticin cures infected larvae. Thus, the constitutively produced antimicrobials by native extracellular symbionts create a significant chemical barrier inside limiting invader expansion. This unique property also benefits E. mundtii itself by providing a competitive advantage, contributing to its dominance within complex microbial settings and its prevalence across Lepidoptera, and probably promotes the long-term cooperative symbiosis between both parties.

All Authors：
Yongqi Shao,Bosheng Chen,Chao Sun,Keishi Ishida,Christian Hertweck,Wilhelm Boland

First Authors：
Yongqi Shao

Correspondence：
Yongqi Shao,Wilhelm Boland

内容要点：

1、蒙氏肠球菌是灰翅夜蛾肠道的优势菌种，它分泌一种稳定的IIa类细菌素（mundticin KS）；

2、mundticin抑制细菌入侵但不会伤害肠道原住共生菌，这促进宿主肠道菌群正常发育；

3、mundticin缺陷菌株失去抑制入侵细菌的能力，提纯的mundticin则能治愈幼虫的感染；

4、这充分说明昆虫肠道里的共生细菌创造了一个重要的内部化学屏障，以限制入侵者扩张；

5、这或许也可解释蒙氏肠球菌为何能在鳞翅目昆虫肠道中占优，并促进它们与宿主的和谐共生。