Department of Biology, Emory University, Atlanta, Georgia, USA.
Division of Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia, USA.
Appl Environ Microbiol. 2021 May 26;87(12):e0021221. doi: 10.1128/AEM.00212-21.
A pervasive pest of stored leguminous products, the bean beetle Callosobruchus maculatus (Coleoptera: Chrysomelidae) associates with a simple bacterial community during adulthood. Despite its economic importance, little is known about the compositional stability, heritability, localization, and metabolic potential of the bacterial symbionts of C. maculatus. In this study, we applied community profiling using 16S rRNA gene sequencing to reveal a highly conserved bacterial assembly shared between larvae and adults. Dominated by and , this community is localized extracellularly along the epithelial lining of the bean beetle's digestive tract. Our analysis revealed that only one species, Staphylococcus gallinarum (phylum ), is shared across all developmental stages. Isolation and whole-genome sequencing of S. gallinarum from the beetle gut yielded a circular chromosome (2.8 Mb) and one plasmid (45 kb). The strain encodes complete biosynthetic pathways for the production of B vitamins and amino acids, including tyrosine, which is increasingly recognized as an important symbiont-supplemented precursor for cuticle biosynthesis in beetles. A carbohydrate-active enzyme search revealed that the genome codes for a number of digestive enzymes, reflecting the nutritional ecology of . The ontogenic conservation of the gut microbiota in the bean beetle, featuring a "core" community composed of , may be indicative of an adaptive role for the host. In clarifying symbiont localization and metabolic potential, we further our understanding and study of a costly pest of stored products. From supplementing essential nutrients to detoxifying plant secondary metabolites and insecticides, bacterial symbionts are a key source of adaptations for herbivorous insect pests. Despite the pervasiveness and geographical range of the bean beetle , the role of microbial symbioses in its natural history remains understudied. Here, we demonstrate that the bean beetle harbors a simple gut bacterial community that is stable throughout development. This community localizes along the insect's digestive tract and is largely dominated by Staphylococcus gallinarum. In elucidating symbiont metabolic potential, we highlight its possible adaptive significance for a widespread agricultural pest.
豆象是储存豆类产品的一种普遍害虫，成年豆象与简单的细菌群落相关联。尽管豆象具有重要的经济意义，但人们对其细菌共生体的组成稳定性、遗传性、定位和代谢潜力知之甚少。在这项研究中，我们应用 16S rRNA 基因测序的群落分析揭示了幼虫和成虫之间共享的高度保守的细菌组合。该群落主要由 和 组成，定位于豆象消化道的上皮衬里的细胞外。我们的分析表明，只有一个物种，即金黄色葡萄球菌（门），存在于所有发育阶段。从甲虫肠道中分离和全基因组测序金黄色葡萄球菌得到一个圆形染色体（2.8 Mb）和一个质粒（45 kb）。该菌株编码完整的生物合成途径，用于生产 B 族维生素和氨基酸，包括酪氨酸，酪氨酸越来越被认为是甲虫外骨骼生物合成中重要的共生体补充前体。碳水化合物活性酶搜索表明，该基因组编码了许多消化酶，反映了 的营养生态。豆象肠道微生物群的个体发生保守性，以由 组成的“核心”群落为特征，可能表明宿主具有适应性作用。在阐明共生体的定位和代谢潜力的同时，我们进一步了解和研究了一种储存产品的昂贵害虫。从补充必需营养物质到解毒植物次生代谢物和杀虫剂，细菌共生体是植食性昆虫害虫适应的关键来源。尽管豆象普遍存在且分布广泛，但微生物共生在其自然历史中的作用仍未得到充分研究。在这里，我们证明豆象体内存在一种简单的肠道细菌群落，这种群落在整个发育过程中是稳定的。该群落定位于昆虫的消化道，主要由金黄色葡萄球菌组成。在阐明共生体的代谢潜力时，我们强调了其对广泛存在的农业害虫的可能适应性意义。
