AgfC and AgfE facilitate extracellular thin aggregative fimbriae synthesis in Salmonella Enteritidis
AgfC and AgfE facilitate extracellular thin aggregative fimbriae synthesis in Salmonella Enteritidis
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DOI：
10.1099/mic.0.2006/000935-0
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发表时间：
2007-04-01
期刊：
影响因子：
2.8
通讯作者：
Kay, W. W.
中科院分区：
文献类型：
--
作者：
Gibson, D. L.;White, A. P.;Kay, W. W.
沙门氏菌薄聚集菌毛（Tclause; curli）是重要的致病和生物膜的形成，但是，很少有人知道他们的结构和形态发生。在沙门氏菌agfBAC Tactylon操纵子中，agfC的转录和作用一直是难以捉摸的，在这项研究中，agfBAC转录本检测使用敏感的逆转录酶技术。使用针对纯化的六组氨酸标记的AgfC产生的多克隆抗体未检测到天然AgfC;然而，反式表达揭示AgfC作为成熟形式定位于周质。一个同基因Δ agfC突变体显示出丰富的20 nm的纤维，除了天然的TfC（5-7 nm），并增加了细胞表面的疏水性。纯化的20 nm纤维在非常严格的条件下解聚，以释放被证明是AgfA亚基的物质。这表明，20 nm的纤维代表了不同形式的TdR。使用同基因Δ agf突变体的抗体捕获测定进一步研究了AgfC在Tclase组装中的作用。在野生型（wt）、Δ agfB和Δ agfF菌株中捕获了可溶性抗体可及形式的AgfA，以支持Tclase组装的细胞外成核-沉淀途径，但在Δ agfC或Δ agfE突变体中未捕获。这表明AgfC和AgfE对于AgfA细胞外组装是重要的，从而促进了TdR的合成。
Salmonella thin aggregative fimbriae (Tafi; curli) are important in pathogenesis and biofilm formation; however, less is known of their structure and morphogenesis. In the Salmonella agfBAC Tafi operon, the transcription and role of agfC have been elusive, In this study, agfBAC transcripts were detected using a sensitive reverse transcriptase technique. Native AgfC was not detected using polyclonal antibodies generated against purified hexahistidine-tagged AgfC; however, in trans expression revealed that AgfC was localized to the periplasm as a mature form. An isogenic Delta agfC mutant displayed an abundance of 20 nm fibres, in addition to native Tafi (5-7 nm), and had an increase in cell surface hydrophobicity. Purified 20 nm fibres were depolymerized under exceptionally stringent conditions to release what proved to be AgfA subunits. This revealed that the 20 nm fibres represented a different form of Tafi. The role of AgfC in Tafi assembly was investigated further using an antibody-capture assay of isogenic Delta agf mutants. A soluble anti body-accessible form of AgfA was captured in wild-type (wt), Delta agfB and Delta agfF strains, in support of the extracellular nucleation-precipitation pathway of Tafi assembly, but not in Delta agfC or Delta agfE mutants. This indicates that AgfC and AgfE are important for AgfA extracellular assembly, facilitating the synthesis of Tafi.