Zavan Lauren, Hor Lilian, Johnston Ella L, Paxman Jason, Heras Begoña, Kaparakis-Liaskos Maria
Department of Microbiology, Anatomy, Physiology, and Pharmacology, La Trobe University, Melbourne, Victoria, Australia.
Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria, Australia.
Microbiol Spectr. 2025 Mar 4;13(3):e0189024. doi: 10.1128/spectrum.01890-24. Epub 2025 Jan 22.
Bacterial membrane vesicles (MVs) are produced by all bacteria and contribute to numerous bacterial functions due to their ability to package and transfer bacterial cargo. In doing so, MVs have been shown to facilitate horizontal gene transfer, mediate antimicrobial activity, and promote biofilm formation. Uropathogenic is a pathogenic Gram-negative organism that persists in the urinary tract of its host due to its ability to form persistent, antibiotic-resistant biofilms. The formation of these biofilms is dependent upon proteins such as Antigen 43 (Ag43), which belongs to the widespread Autotransporter group of bacterial surface proteins. In the autotransporter Ag43 has been shown to contribute to bacterial cell aggregation and biofilm formation via self-association of Ag43 between neighboring Ag43-expressing bacteria. As MVs package bacterial proteins, we investigated whether MVs produced by contained Ag43, and the ability of Ag43-expressing MVs to facilitate cell aggregation and biofilm formation. We showed that Ag43 expressing produced MVs that contained Ag43 on their surface and had an enhanced ability to bind to bacteria. Furthermore, we demonstrated that the addition of Ag43-containing MVs to Ag43-expressing significantly enhanced biofilm formation. These findings reveal the contribution of MVs harboring autotransporters in promoting bacterial aggregation and enhancing biofilm formation, highlighting the impact of MVs and their specific composition to bacterial adaptation and pathogenesis.IMPORTANCEAutotransporter proteins are the largest family of outer membrane and secreted proteins in Gram-negative bacteria which contribute to pathogenesis by promoting aggregation, biofilm formation, persistence, and cytotoxicity. Although the roles of bacterial autotransporters are well known, the ability of bacterial membrane vesicles (MVs) naturally released from the surface of bacteria to contain autotransporters and their role in promoting virulence remains less investigated. Our findings reveal that MVs produced by contain the autotransporter protein Ag43. Furthermore, we show that Ag43-containing MVs function to enhance bacterial cell interactions and biofilm formation. By demonstrating the ability of MVs to carry functional autotransporter adhesins, this work highlights the importance of MVs in disseminating autotransporters beyond the bacterial cell membrane to ultimately promote cellular interactions and enhance biofilm development. Overall, these findings have significant implications in furthering our understanding of the numerous ways in which MVs can facilitate bacterial persistence and pathogenesis.
细菌膜泡（MVs）由所有细菌产生，由于其具有包装和转运细菌物质的能力，因而对多种细菌功能有贡献。在此过程中，已证明MVs能促进水平基因转移、介导抗菌活性并促进生物膜形成。尿路致病性大肠杆菌是一种致病性革兰氏阴性菌，因其能够形成持续存在的、对抗生素耐药的生物膜而在宿主尿路中持续存在。这些生物膜的形成依赖于诸如抗原43（Ag43）等蛋白质，Ag43属于广泛存在的细菌表面蛋白自转运体家族。在大肠杆菌中，自转运体Ag43已被证明通过相邻表达Ag43的细菌之间的Ag43自缔合作用，促进细菌细胞聚集和生物膜形成。由于MVs能包装细菌蛋白，我们研究了大肠杆菌产生的MVs是否含有Ag43，以及表达Ag43的MVs促进细胞聚集和生物膜形成的能力。我们发现表达Ag43的大肠杆菌产生的MVs在其表面含有Ag43，并且与大肠杆菌的结合能力增强。此外，我们证明向表达Ag43的大肠杆菌中添加含Ag43的MVs可显著增强生物膜形成。这些发现揭示了携带自转运体的MVs在促进细菌聚集和增强生物膜形成中的作用，突出了MVs及其特定组成对细菌适应性和致病性的影响。重要性自转运体蛋白是革兰氏阴性菌中外膜和分泌蛋白的最大家族，通过促进聚集、生物膜形成、持续性和细胞毒性作用对致病性有贡献。尽管细菌自转运体的作用已为人所知，但从细菌表面自然释放的细菌膜泡（MVs）含有自转运体的能力及其在促进毒力方面发挥的作用仍较少被研究。我们的发现揭示了大肠杆菌产生的MVs含有自转运体蛋白Ag43。此外，我们表明含Ag43的MVs起到增强细菌细胞相互作用和生物膜形成的作用。通过证明MVs携带功能性自转运体黏附素的能力，这项研究突出了MVs在将自转运体传播到细菌细胞膜之外以最终促进细胞相互作用和增强生物膜发育方面的重要性。总体而言，这些发现对于进一步理解MVs促进细菌持续性和致病性的多种方式具有重要意义。
