Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA.
FEMS Microbiol Lett. 2010 Sep 1;310(1):62-8. doi: 10.1111/j.1574-6968.2010.02046.x. Epub 2010 Jun 23.
The pili of Geobacter sulfurreducens are of interest because of the apparent importance of the type IV pili in extracellular electron transfer. A strain of G. sulfurreducens, designated strain MA, produced many more pili than the previously studied DL-1 strain even though genome resequencing indicated that the MA and DL-1 genome sequences were identical. Filaments that looked similar to type IV pili in transmission electron micrographs were abundant even after the gene encoding PilA, the structural pilin protein, was deleted. The results of proteinase K treatment indicated that the filaments were proteinaceous. The simultaneous deletion of several genes encoding homologues of type II pseudopilins was required before the filaments were significantly depleted. The pilA-deficient MA strain attached to glass as well as the wild-type MA did, but strains in which three or four pseudopilin genes were deleted in addition to pilA had impaired attachment capabilities. These results demonstrate that there are several proteins that can yield pilin-like filaments in G. sulfurreducens and that some means other than microscopic observation is required before the composition of filaments can be unambiguously specified.
硫还原地杆菌的菌毛引起了人们的兴趣，因为 IV 型菌毛在细胞外电子转移中显然很重要。与先前研究的 DL-1 菌株相比，一株被命名为 MA 的硫还原地杆菌产生了更多的菌毛，尽管基因组重测序表明 MA 和 DL-1 的基因组序列完全相同。即使删除了编码结构菌毛蛋白 PilA 的基因，在透射电子显微镜下也能观察到大量类似于 IV 型菌毛的丝状结构。蛋白激酶处理的结果表明这些丝状结构是蛋白质。只有在同时删除几个编码 II 型假菌毛同源物的基因后，丝状结构才会明显减少。与野生型 MA 相比，缺失 pilA 的 MA 菌株仍能附着在玻璃上，但除了 pilA 之外还删除了三个或四个假菌毛基因的菌株附着能力受损。这些结果表明，在硫还原地杆菌中有几种蛋白质可以产生菌毛样的丝状结构，在能够明确指定丝状结构的组成之前，需要采用除显微镜观察以外的其他手段。
