Table_1_Dominance Between Plasmids Determines the Extent of Biofilm Formation.XLSX

Bacterial biofilms have an impact in medical and industrial environments because they often confer protection to bacteria against harmful agents, and constitute a source from which microorganisms can disperse. Conjugative plasmids can enhance bacterial ability to form biofilms because conjugative pili act as adhesion factors. However, plasmids may interact with each other, either facilitating or inhibiting plasmid transfer. Accordingly, we asked whether effects on plasmid transfer also impacts biofilm formation. We measured biofilm formation of Escherichia coli cells harboring two plasmid types, or when the two plasmids were present in the same population but carried in different cells. Using eleven natural isolated conjugative plasmids, we confirmed that some indeed promote biofilm formation and, importantly, that this ability is correlated with conjugative efficiency. Further we studied the effect of plasmid pairs on biofilm formation. We observed increased biofilm formation in approximately half of the combinations when both plasmids inhabited the same cell or when the plasmids were carried in different cells. Moreover, in approximately half of the combinations, independent of the co-inhabitation conditions, one of the plasmids alone determined the extent of biofilm formation – thus having a dominant effect over the other plasmid. The molecular mechanisms responsible for these interactions were not evaluated here and future research is required to elucidate them.

细菌生物膜（bacterial biofilms）可对医疗与工业环境造成影响，因其通常可使细菌抵御有害因子的侵袭，并成为微生物扩散的源头。接合性质粒（conjugative plasmids）可提升细菌形成生物膜的能力，这是由于接合菌毛（conjugative pili）可作为黏附因子发挥作用。然而，质粒之间可发生相互作用，或促进或抑制质粒的接合转移。据此，我们探究了质粒接合转移的相关效应是否同样会对生物膜形成产生影响。我们以携带两类质粒的大肠杆菌（Escherichia coli），或是两类质粒共存于同一菌群但分别位于不同宿主细胞内的样本为对象，测定其生物膜形成能力。我们使用11株天然分离的接合性质粒，证实部分质粒确实可促进生物膜形成，且重要的是，该能力与接合效率相关。进一步地，我们探究了质粒组合对生物膜形成的影响。我们观察到，当两类质粒共存于同一宿主细胞，或是分别存在于不同宿主细胞时，约半数的质粒组合可使生物膜形成能力得到提升。此外，在约半数的质粒组合中，无论两类质粒是否共存于同一宿主细胞，其中某一株质粒均可单独决定生物膜的形成程度，即对另一株质粒表现出显性效应。本研究未探究此类相互作用的分子机制，后续仍需开展相关研究以阐明其具体机理。