Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Aarhus, Denmark.
PLoS One. 2013 Oct 7;8(10):e76630. doi: 10.1371/journal.pone.0076630. eCollection 2013.
Functional bacterial amyloids (FuBA) are important components in many environmental biofilms where they provide structural integrity to the biofilm, mediate bacterial aggregation and may function as virulence factor by binding specifically to host cell molecules. A novel FuBA system, the Fap system, was previously characterized in the genus Pseudomonas, however, very little is known about the phylogenetic diversity of bacteria with the genetic capacity to apply this system. Studies of genomes and public metagenomes from a diverse range of habitats showed that the Fap system is restricted to only three classes in the phylum Proteobacteria, the Beta-, Gamma- and Deltaproteobacteria. The structural organization of the fap genes into a single fapABCDEF operon is well conserved with minor variations such as a frequent deletion of fapA. A high degree of variation was seen within the primary structure of the major Fap fibril monomers, FapC, whereas the minor monomers, FapB, showed less sequence variation. Comparison of phylogenetic trees based on Fap proteins and the 16S rRNA gene of the corresponding bacteria showed remarkably similar overall topology. This indicates, that horizontal gene transfer is an infrequent event in the evolution of the Fap system.
功能性细菌淀粉样蛋白（FuBA）是许多环境生物膜中的重要组成部分，它们为生物膜提供结构完整性，介导细菌聚集，并通过特异性结合宿主细胞分子而可能作为毒力因子发挥作用。先前在假单胞菌属中对一种新型 FuBA 系统（Fap 系统）进行了特征描述，但是，对于具有应用该系统遗传能力的细菌的系统发育多样性知之甚少。对来自各种生境的基因组和公共宏基因组的研究表明，Fap 系统仅局限于变形菌门的三个类，即β、γ和δ变形菌。fap 基因的结构组织成单个 fapABCDEF 操纵子，具有较小的变化，例如 fapA 频繁缺失。主要 Fap 纤维单体 FapC 的一级结构中存在高度的变异，而次要单体 FapB 的序列变异较少。基于 Fap 蛋白和相应细菌的 16S rRNA 基因构建的系统发育树的比较显示出非常相似的整体拓扑结构。这表明，在 Fap 系统的进化过程中，水平基因转移是一个罕见的事件。
