The silkworm, Bombyx mori, is utilized as a research model in many aspects of biological studies, including genetics, development and immunology. Previous biochemical and genomic studies have elucidated the silkworm immunity in response to infections elicited by bacteria, fungi, microsporidia, and viruses. The intestine serves as the front line in the battle between insects and ingested harmful microorganisms. In this study, we performed RNA sequencing (RNA-seq) of the larval silkworm midgut after oral infection with the Gram-positive bacterium Bacillus bombysepticus and the Gram-negative bacterium Yersinia pseudotuberculosis. This enables us to get a comprehensive understanding of the midgut responses to bacterial infection. We found that B. bombysepticus induced much stronger immune responses than Y. pseudotuberculosis did. Bacterial infection resulted in more energy consumption including carbohydrates and fatty acids. The midgut immune system was characterized by the generation of reactive oxygen species and antimicrobial peptides. The former played a critical role in eliminating invading bacteria during early stage, while the latter executed during late stage. Our results provide an integrated insight into the midgut systematic responses to bacterial infection.

中文翻译：

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响应细菌感染，家蚕中肠依次产生活性氧和抗菌肽。

家蚕 Bombyx mori 被用作生物学研究的许多方面的研究模型，包括遗传学、发育和免疫学。以前的生化和基因组研究阐明了蚕对细菌、真菌、微孢子虫和病毒引起的感染的免疫反应。肠道是昆虫和摄入的有害微生物之间战斗的前线。在这项研究中，我们对被革兰氏阳性菌炸弹脓毒杆菌和革兰氏阴性菌假结核杆菌感染的幼虫中肠进行 RNA 测序 (RNA-seq)。这使我们能够全面了解中肠对细菌感染的反应。我们发现 B.bombysepticus 诱导的免疫反应比 Y.pseudotuberculosis 强得多。细菌感染导致更多的能量消耗，包括碳水化合物和脂肪酸。中肠免疫系统的特征是产生活性氧和抗菌肽。前者在早期对入侵细菌的清除起到关键作用，而后者则在后期发挥作用。我们的结果提供了对细菌感染的中肠系统反应的综合见解。