期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2019
卷号：116
期号：45
页码：22673-22682
DOI：10.1073/pnas.1912397116
出版社：The National Academy of Sciences of the United States of America
摘要：Despite the omnipresence of specific host–symbiont associations with acquisition of the microbial symbiont from the environment, little is known about how the specificity of the interaction evolved and is maintained. The bean bug Riptortus pedestris acquires a specific bacterial symbiont of the genus Burkholderia from environmental soil and harbors it in midgut crypts. The genus Burkholderia consists of over 100 species, showing ecologically diverse lifestyles, and including serious human pathogens, plant pathogens, and nodule-forming plant mutualists, as well as insect mutualists. Through infection tests of 34 Burkholderia species and 18 taxonomically diverse bacterial species, we demonstrate here that nonsymbiotic Burkholderia and even its outgroup Pandoraea could stably colonize the gut symbiotic organ and provide beneficial effects to the bean bug when inoculated on aposymbiotic hosts. However, coinoculation revealed that the native symbiont always outcompeted the nonnative bacteria inside the gut symbiotic organ, explaining the predominance of the native Burkholderia symbiont in natural bean bug populations. Hence, the abilities for colonization and cooperation, usually thought of as specific traits of mutualists, are not unique to the native Burkholderia symbiont but, to the contrary, competitiveness inside the gut is a derived trait of the native symbiont lineage only and was thus critical in the evolution of the insect gut symbiont..
