Many commensal bacteria antagonize each other or their host by producing syringe-like secretion systems called contractile injection systems (CIS). Members of the Bacteroidales family have been shown to produce only one type of CIS—a contact-dependent type 6 secretion system that mediates bacterium-bacterium interactions. Here, we show that a second distinct cluster of genes from Bacteroidales bacteria from the human microbiome may encode yet-uncharacterized injection systems that we term Bacteroidales injection systems (BIS). We found that BIS genes are present in the gut microbiomes of 99% of individuals from the United States and Europe and that BIS genes are more prevalent in the gut microbiomes of healthy individuals than in those individuals suffering from inflammatory bowel disease. Gene clusters similar to that of the BIS mediate interactions between bacteria and diverse eukaryotes, like amoeba, insects, and tubeworms. Our findings highlight the ubiquity of the BIS gene cluster in the human gut and emphasize the relevance of the gut microbiome to the human host. These results warrant investigations into the structure and function of the BIS and how they might mediate interactions between Bacteroidales bacteria and the human host or microbiome.

中文翻译：

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在大多数健康成人微生物组中发现了独特的收缩注射系统基因簇。

许多共生细菌通过产生称为收缩注射系统（CIS）的注射器样分泌系统来对抗彼此或它们的宿主。拟杆菌目家族的成员已被证明只产生一种类型的 CIS——一种介导细菌与细菌相互作用的接触依赖性 6 型分泌系统。在这里，我们表明，来自人类微生物组的拟杆菌门细菌的第二个不同基因簇可能编码尚未表征的注射系统，我们将其称为拟杆菌注射系统（BIS）。我们发现，BIS 基因存在于 99% 的美国和欧洲个体的肠道微生物组中，并且 BIS 基因在健康个体的肠道微生物组中比在患有炎症性肠病的个体中更普遍。与 BIS 相似的基因簇介导细菌与多种真核生物（如阿米巴原虫、昆虫和管虫）之间的相互作用。我们的研究结果强调了 BIS 基因簇在人类肠道中的普遍存在，并强调了肠道微生物组与人类宿主的相关性。这些结果值得对 BIS 的结构和功能以及它们如何介导拟杆菌和人类宿主或微生物组之间的相互作用进行研究。