Département de Microbiologie, Unité de Génétique des Biofilms, Institut Pasteur, Paris, France.
ISME J. 2014 Jun;8(6):1275-88. doi: 10.1038/ismej.2013.238. Epub 2014 Jan 23.
Formation of bacterial biofilm communities leads to profound physiological modifications and increased physical and metabolic exchanges between bacteria. It was previously shown that bioactive molecules produced within the biofilm environment contribute to bacterial interactions. Here we describe new pore-forming colicin R, specifically produced in biofilms formed by the natural isolate Escherichia coli ROAR029 but that cannot be detected under planktonic culture conditions. We demonstrate that an increased SOS stress response within mature biofilms induces SOS-dependent colicin R expression. We provide evidence that colicin R displays increased activity against E. coli strains that have a reduced lipopolysaccharide length, such as the pathogenic enteroaggregative E. coli LF82 clinical isolate, therefore pointing to lipopolysaccharide size as an important determinant for resistance to colicins. We show that colicin R toxicity toward E. coli LF82 is increased under biofilm conditions compared with planktonic susceptibility and that release of colicin R confers a strong competitive advantage in mixed biofilms by rapidly outcompeting sensitive neighboring bacteria. This work identifies the first biofilm-associated colicin that preferentially targets biofilm bacteria. Furthermore, it indicates that the study of antagonistic molecules produced in biofilm and multispecies contexts could reveal unsuspected, ecologically relevant bacterial interactions influencing population dynamics in natural environments.
细菌生物膜群落的形成导致了深刻的生理改变，并增加了细菌之间的物理和代谢交换。先前的研究表明，生物膜环境中产生的生物活性分子有助于细菌之间的相互作用。在这里，我们描述了一种新的孔形成大肠菌素 R，它是由天然分离株大肠杆菌 ROAR029 在生物膜中特异性产生的，但在浮游培养条件下无法检测到。我们证明，成熟生物膜内增加的 SOS 应激反应诱导了 SOS 依赖性大肠菌素 R 的表达。我们提供的证据表明，大肠菌素 R 对脂多糖长度减少的大肠杆菌菌株（如致病性肠聚集性大肠杆菌 LF82 临床分离株）显示出增加的活性，因此脂多糖大小是抵抗大肠菌素的一个重要决定因素。我们表明，与浮游敏感性相比，大肠菌素 R 对大肠杆菌 LF82 的毒性在生物膜条件下增加，并且大肠菌素 R 的释放通过快速淘汰敏感的邻近细菌，在混合生物膜中赋予了强大的竞争优势。这项工作确定了第一个优先靶向生物膜细菌的生物膜相关大肠菌素。此外，它表明，在生物膜和多物种环境中研究拮抗分子可以揭示意想不到的、具有生态相关性的细菌相互作用，这些相互作用影响自然环境中的种群动态。
