Center for Molecular Medicine and Infectious Diseases, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, 24061, USA.
Virginia Tech Carilion School of Medicine, Roanoke, VA, 24016, USA.
Sci Rep. 2019 Aug 22;9(1):12252. doi: 10.1038/s41598-019-48697-x.
Biofilms are matrix-associated communities that enable bacteria to colonise environments unsuitable for free-living bacteria. The facultative intracellular pathogen Francisella tularensis can persist in water, amoebae, and arthropods, as well as within mammalian macrophages. F. tularensis Types A and B form poor biofilms, but F. tularensis mutants lacking lipopolysaccharide O-antigen, O-antigen capsule, and capsule-like complex formed up to 15-fold more biofilm than fully glycosylated cells. The Type B live vaccine strain was also 50% less capable of initiating surface attachment than mutants deficient in O-antigen and capsule-like complex. However, the growth medium of all strains tested also influenced the formation of biofilm, which contained a novel exopolysaccharide consisting of an amylose-like glucan. In addition, the surface polysaccharide composition of the bacterium affected the protein:DNA:polysaccharide composition of the biofilm matrix. In contrast, F. novicida attached to surfaces more efficiently and made a more robust biofilm than Type A or B strains, but loss of O-antigen or capsule-like complex did not significantly affect F. novicida biofilm formation. These results indicated that suppression of surface polysaccharides may promote biofilm formation by F. tularensis Types A and B. Whether biofilm formation enhances survival of F. tularensis in aquatic or other environmental niches has yet to be determined.
生物膜是一种基质相关的群落，使细菌能够在不适合自由生活细菌的环境中定殖。兼性细胞内病原体土拉弗朗西斯菌可以在水中、变形虫和节肢动物中以及哺乳动物巨噬细胞内持续存在。F. tularensis 型 A 和 B 形成的生物膜较差，但缺乏脂多糖 O-抗原、O-抗原荚膜和类似荚膜的复合物的 F. tularensis 突变体形成的生物膜比完全糖基化细胞多 15 倍。B 型活疫苗株在表面附着方面的能力也比缺乏 O-抗原和类似荚膜复合物的突变体低 50%。然而，所有测试菌株的生长培养基也会影响生物膜的形成，其中含有一种由类似直链淀粉的葡聚糖组成的新型胞外多糖。此外，细菌的表面多糖组成会影响生物膜基质的蛋白质、DNA 和多糖的组成。相比之下，F. novicida 比型 A 或 B 菌株更有效地附着在表面上，并形成更坚固的生物膜，但缺失 O-抗原或类似荚膜的复合物不会显著影响 F. novicida 生物膜的形成。这些结果表明，表面多糖的抑制可能会促进 F. tularensis 型 A 和 B 的生物膜形成。生物膜形成是否会增强土拉弗朗西斯菌在水生或其他环境小生境中的生存能力还有待确定。
