Centre for Host-Microbiome Interactions, Faculty of Dental, Oral & Craniofacial Sciences, King's College London, London, UK.
School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK.
NPJ Biofilms Microbiomes. 2022 Feb 25;8(1):9. doi: 10.1038/s41522-022-00272-5.
Escherichia coli is a Gram-negative bacterium that colonises the human intestine and virulent strains can cause severe diarrhoeal and extraintestinal diseases. The protein SslE is secreted by a range of pathogenic and commensal E. coli strains. It can degrade mucins in the intestine, promotes biofilm maturation and it is a major determinant of infection in virulent strains, although how it carries out these functions is not well understood. Here, we examine SslE from the commensal E. coli Waksman and BL21 (DE3) strains and the enterotoxigenic H10407 and enteropathogenic E2348/69 strains. We reveal that SslE has a unique and dynamic structure in solution and in response to acidification within mature biofilms it can form a unique aggregate with amyloid-like properties. Furthermore, we show that both SslE monomers and aggregates bind DNA in vitro and co-localise with extracellular DNA (eDNA) in mature biofilms, and SslE aggregates may also associate with cellulose under certain conditions. Our results suggest that interactions between SslE and eDNA are important for biofilm maturation in many E. coli strains and SslE may also be a factor that drives biofilm formation in other SslE-secreting bacteria.
大肠杆菌是一种革兰氏阴性细菌，定植于人体肠道，其毒力株可引起严重的腹泻和肠道外疾病。蛋白SslE 由多种致病性和共生大肠杆菌菌株分泌。它可以降解肠道中的粘蛋白，促进生物膜成熟，是毒力株感染的主要决定因素，尽管其如何发挥这些功能尚不清楚。在这里，我们研究了来自共生大肠杆菌 Waksman 和 BL21（DE3）菌株以及肠产毒性 H10407 和肠致病性 E2348/69 菌株的 SslE。我们揭示了 SslE 在溶液中具有独特而动态的结构，并且在成熟生物膜中的酸化反应中，它可以形成具有类似淀粉样特性的独特聚集体。此外，我们表明 SslE 单体和聚集体都可以在体外结合 DNA，并在成熟生物膜中与细胞外 DNA（eDNA）共定位，并且在某些条件下 SslE 聚集体也可能与纤维素结合。我们的结果表明，SslE 与 eDNA 之间的相互作用对于许多大肠杆菌菌株的生物膜成熟很重要，并且 SslE 也可能是其他分泌 SslE 的细菌中生物膜形成的一个因素。
