Bray Andrew S, Broberg Christopher A, Hudson Andrew W, Wu Weisheng, Nagpal Ravinder K, Islam Maidul, Valencia-Bacca Juan D, Shahid Fawaz, Hernandez Giovanna E, Nutter Noah A, Walker Kimberly A, Bennett Emma F, Young Taylor M, Barnes Andrew J, Ornelles David A, Miller Virginia L, Zafar M Ammar
Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston Salem, NC, USA.
Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, NC, USA.
Nat Commun. 2025 Jan 22;16(1):940. doi: 10.1038/s41467-025-56309-8.
Microbial species must compete for space and nutrients to persist in the gastrointestinal (GI) tract, and our understanding of the complex pathobiont-microbiota interactions is far from complete. Klebsiella pneumoniae, a problematic, often drug-resistant nosocomial pathogen, can colonize the GI tract asymptomatically, serving as an infection reservoir. To provide insight on how K. pneumoniae interacts with the resident gut microbiome, we conduct a transposon mutagenesis screen using a murine model of GI colonization with an intact microbiota. Among the genes identified were those encoding a type VI secretion system (T6SS), which mediates contact-dependent killing of gram-negative bacteria. From several approaches, we demonstrate that the T6SS is critical for K. pneumoniae gut colonization. Metagenomics and in vitro killing assays reveal that K. pneumoniae reduces Betaproteobacteria species in a T6SS-dependent manner, thus identifying specific species targeted by K. pneumoniae. We further show that T6SS gene expression is controlled by several transcriptional regulators and that expression only occurs in vitro under conditions that mimic the gut environment. By enabling K. pneumoniae to thrive in the gut, the T6SS indirectly contributes to the pathogenic potential of this organism. These observations advance our molecular understanding of how K. pneumoniae successfully colonizes the GI tract.
微生物物种必须竞争空间和营养物质才能在胃肠道（GI）中持续存在，而我们对复杂的致病共生菌与微生物群相互作用的理解还远远不够完善。肺炎克雷伯菌是一种有问题的、通常具有耐药性的医院病原体，它可以无症状地定殖在胃肠道，成为感染源。为了深入了解肺炎克雷伯菌如何与肠道常驻微生物群相互作用，我们使用具有完整微生物群的胃肠道定殖小鼠模型进行了转座子诱变筛选。在鉴定出的基因中，有编码VI型分泌系统（T6SS）的基因，该系统介导革兰氏阴性菌的接触依赖性杀伤。通过多种方法，我们证明T6SS对肺炎克雷伯菌在肠道的定殖至关重要。宏基因组学和体外杀伤试验表明，肺炎克雷伯菌以T6SS依赖的方式减少β-变形菌属物种，从而确定了肺炎克雷伯菌靶向的特定物种。我们进一步表明，T6SS基因表达受几种转录调节因子控制，并且仅在模拟肠道环境的条件下在体外发生表达。通过使肺炎克雷伯菌在肠道中茁壮成长，T6SS间接促进了这种生物体的致病潜力。这些观察结果推进了我们对肺炎克雷伯菌如何成功定殖胃肠道的分子理解。
