The Negativicutes are a clade of the Firmicutes that have retained the ancestral diderm character and possess an outer membrane. One of the best studied Negativicutes, Veillonella parvula, is an anaerobic commensal and opportunistic pathogen inhabiting complex human microbial communities, including the gut and the dental plaque microbiota. Whereas the adhesion and biofilm capacities of V. parvula are expected to be crucial for its maintenance and development in these environments, studies of V. parvula adhesion have been hindered by the lack of efficient genetic tools to perform functional analyses in this bacterium. Here, we took advantage of a recently described naturally transformable V. parvula isolate, SKV38, and adapted tools developed for the closely related Clostridia spp. to perform random transposon and targeted mutagenesis to identify V. parvula genes involved in biofilm formation. We show that type V secreted autotransporters, typically found in diderm bacteria, are the main determinants of V. parvula autoaggregation and biofilm formation and compete with each other for binding either to cells or to surfaces, with strong consequences for V. parvula biofilm formation capacity. The identified trimeric autotransporters have an original structure compared to classical autotransporters identified in Proteobacteria, with an additional C-terminal domain. We also show that inactivation of the gene coding for a poorly characterized metal-dependent phosphohydrolase HD domain protein conserved in the Firmicutes and their closely related diderm phyla inhibits autotransporter-mediated biofilm formation. This study paves the way for further molecular characterization of V. parvula interactions with other bacteria and the host within complex microbiota environments.

中文翻译：

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自动转运蛋白可驱动小生虫Firmicute Veillonella parvula中的生物膜形成和自动聚集。

的Negativicutes是的进化枝厚壁菌门已经保留了祖diderm字符和具有的外膜。一个最好的学习的Negativicutes，小韦荣菌，是一种厌氧共生和条件致病菌居住在复杂的人类微生物群落，包括肠和牙菌斑菌群。预计小肠粘虫的粘附力和生物膜能力对其在这些环境中的维持和发育至关重要，而小肠粘菌的研究缺乏有效的遗传工具来执行此细菌的功能分析已阻碍了粘附。在这里，我们利用了最近描述自然变形的五球菌菌株，SKV38，并适用于密切相关的开发工具，梭状芽孢杆菌属。进行随机转座子和定向诱变，以鉴定参与生物膜形成的小枝弧菌基因。我们表明，通常在双生殖细菌中发现的V型分泌的自转运蛋白是V. parvula自动聚集和生物膜形成的主要决定因素，并且彼此竞争结合到细胞或表面，对V. parvula具有很强的影响生物膜形成能力。与在Proteobacteria中鉴定的经典自转运蛋白相比，已鉴定的三聚体自转运蛋白具有原始结构，并带有一个额外的C末端结构域。我们还表明，编码在Firmicutes和它们密切相关的Diderm phyl中保存的特征不佳的金属依赖性磷酸水解酶HD域蛋白的基因失活抑制了自转运蛋白介导的生物膜的形成。这项研究为进一步在复杂的微生物群环境中表征小枝弧菌与其他细菌和宿主的相互作用铺平了道路。