Elucidation of biofilm structure formation in the plant growth-promoting rhizobacterium Azospirillum brasilense is necessary to gain a better understanding of the growth of cells within the extracellular matrix and its role in the colonization of plants of agronomic importance. We used immunofluorescence microscopy and confocal laser scanning microscopy to study spatio-temporal biofilm formation on an abiotic surface. Observations facilitated by fluorescence microscopy revealed the presence of polar flagellin, exopolysaccharides, outer major membrane protein (OmaA) and extracellular DNA in the Azospirillum biofilm matrix. In static culture conditions, the polar flagellum disaggregated after 3 days of biofilm growth, but exopolysaccharides were increasing. These findings suggest that the first step in biofilm formation may be attachment, in which the bacterium first makes contact with a surface through its polar flagellum. After attaching to the surface, the long flagella and OmaA intertwine the cells to form a network. These bacterial aggregates initiate biofilm development. The underlying mechanisms dictating how the biofilm matrix components of A. brasilense direct the overall morphology of the biofilm are not well known. The methods developed here might be useful in further studies that analyze the differential spatial regulation of genes encoding matrix components that drive biofilm construction.

中文翻译：

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巴西固氮螺菌生物膜的时空形成和细胞外基质分析。

阐明促进植物生长的根际细菌巴西细螺旋藻的生物膜结构形成对于更好地了解细胞外基质内细胞的生长及其在具有农业重要性的植物定殖中的作用是必要的。我们使用免疫荧光显微镜和共聚焦激光扫描显微镜研究了非生物表面时空生物膜的形成。荧光显微镜观察结果表明，偶氮螺旋菌生物膜基质中存在极性鞭毛蛋白，胞外多糖，主要外膜蛋白（OmaA）和细胞外DNA。在静态培养条件下，极性鞭毛在生物膜生长3天后会分解，但胞外多糖却在增加。这些发现表明，生物膜形成的第一步可能是附着，其中细菌首先通过其极性鞭毛与表面接触。附着于表面后，长鞭毛和OmaA缠绕细胞形成网络。这些细菌聚集体启动生物膜的发育。决定巴西拟南芥生物膜基质成分如何指导生物膜整体形态的潜在机制尚不清楚。本文开发的方法可能在进一步的研究中有用，这些研究会分析编码驱动生物膜构建的基质成分的基因的差异空间调控。决定巴西拟南芥生物膜基质成分如何指导生物膜整体形态的潜在机制尚不清楚。本文开发的方法可能在进一步的研究中有用，这些研究会分析编码驱动生物膜构建的基质成分的基因的差异空间调控。决定巴西拟南芥生物膜基质成分如何指导生物膜整体形态的潜在机制尚不清楚。本文开发的方法可能在进一步的研究中有用，这些研究将分析驱动生物膜构建的基质成分的基因的差异空间调控。