Mechanisms by which cells attach to a surface and form a biofilm are diverse and differ greatly among organisms. The Gram-negative gammaproteobacterium Pseudomonas fluorescens attaches to a surface through the localization of the large type 1-secreted RTX adhesin LapA to the outer surface of the cell. LapA localization to the cell surface is controlled by the activities of a periplasmic protease, LapG, and an inner membrane-spanning cyclic di-GMP-responsive effector protein, LapD. A previous study identified a second, LapA-like protein encoded in the P. fluorescens Pf0-1 genome: Pfl01_1463. Here, we identified specific growth conditions under which Pfl01_1463, here called MapA (medium adhesion protein A) is a functional adhesin contributing to biofilm formation. This adhesin, like LapA, appears to be secreted through a Lap-related type 1 secretion machinery, and its localization is controlled by LapD and LapG. However, differing roles of LapA and MapA in biofilm formation are achieved, at least in part, through the differences in the sequences of the two adhesins and different distributions of the expression of the lapA and mapA genes within a biofilm. LapA-like proteins are broadly distributed throughout the Proteobacteria, and furthermore, LapA and MapA are well conserved among other Pseudomonas species. Together, our data indicate that the mechanisms by which a cell forms a biofilm and the components of a biofilm matrix can differ depending on growth conditions and the matrix protein(s) expressed.

中文翻译：

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假单胞菌中保守的第二大RTX粘附蛋白MapA有助于荧光假单胞菌形成生物膜。

细胞附着于表面并形成生物膜的机制是多种多样的，并且在生物体之间差异很大。革兰氏阴性γ-变形杆菌荧光假单胞菌通过将大型1型RTX粘附素LapA定位在细胞外表面而附着在表面上。LapA定位到细胞表面是由周质蛋白酶LapG和内部跨膜环状di-GMP响应效应蛋白LapD的活性控制的。先前的研究确定了在荧光假单胞菌Pf0-1基因组中编码的第二个LapA样蛋白：Pfl01_1463。在这里，我们确定了具体的生长条件下，其Pfl01_1463，这里所说的地图（米edium一个dhesion p roteinA）是有助于生物膜形成的功能性粘附素。与LapA一样，这种粘附素似乎是通过Lap相关的1型分泌机制分泌的，其定位受LapD和LapG的控制。但是，LapA和MapA在生物膜形成中的不同作用至少部分是通过两种粘附素序列的差异以及生物膜内lapA和mapA基因表达的不同分布来实现的。LapA样蛋白广泛分布在整个变形杆菌中，此外，LapA和MapA在其他假单胞菌中保存良好种类。总之，我们的数据表明，细胞形成生物膜和生物膜基质成分的机制可能因生长条件和表达的基质蛋白而异。