Coordinated Cyclic-Di-GMP Repression of Salmonella Motility through YcgR and Cellulose
Coordinated Cyclic-Di-GMP Repression of Salmonella Motility through YcgR and Cellulose
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DOI：
10.1128/jb.01789-12
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发表时间：
2013-02-01
影响因子：
3.2
通讯作者：
Solano, Cristina
中科院分区：
文献类型：
--
作者：
Zorraquino, Violeta;Garcia, Begona;Solano, Cristina
环二gmp （c-di-GMP）是控制多种细胞过程的二级信使，包括生物膜和浮游细菌生活方式之间的转换。这种核苷酸与细胞效应物结合以发挥其调节功能。在沙门氏菌中，两种蛋白BcsA和YcgR是唯一已知的c-di-GMP受体，它们都含有与c-di-GMP结合的PilZ结构域。BcsA通过c-二gmp结合，合成纤维素，这是生物膜基质的主要外多糖。YcgR通过与鞭毛运动蛋白的相互作用，致力于c-di- gmp依赖性运动抑制。然而，先前的证据表明，在缺乏YcgR的情况下，仍有一种额外的元素介导高c-di-GMP水平下的运动障碍。在这里，我们发现纤维素本身是进一步促进抑制细菌运动的因素，一旦高c-二gmp含量驱动了一种固定的生活方式的激活。bcsABZC操纵子的不同基因失活、BcsA PilZ结构域RxxxR基序的保守残基突变或BcsA产生的纤维素降解，可以挽救通过过表达二胍酸环化酶达到高c-二gmp水平的Delta ycgR菌株的运动缺陷。高c-二gmp水平引起细胞周围的纤维素积累，阻碍鞭毛旋转，可能是通过位阻的方式，但不影响鞭毛基因的表达、输出或组装。我们的研究结果强调了纤维素在沙门氏菌生活方式转换中的相关性，作为一种建筑元素，它既是生物膜发育所必需的，也是与YcgR合作完全抑制运动所必需的。
Cyclic di-GMP (c-di-GMP) is a secondary messenger that controls a variety of cellular processes, including the switch between a biofilm and a planktonic bacterial lifestyle. This nucleotide binds to cellular effectors in order to exert its regulatory functions. In Salmonella, two proteins, BcsA and YcgR, both of them containing a c-di-GMP binding PilZ domain, are the only known c-di-GMP receptors. BcsA, upon c-di-GMP binding, synthesizes cellulose, the main exopolysaccharide of the biofilm matrix. YcgR is dedicated to c-di-GMP-dependent inhibition of motility through its interaction with flagellar motor proteins. However, previous evidences indicate that in the absence of YcgR, there is still an additional element that mediates motility impairment under high c-di-GMP levels. Here we have uncovered that cellulose per se is the factor that further promotes inhibition of bacterial motility once high c-di-GMP contents drive the activation of a sessile lifestyle. Inactivation of different genes of the bcsABZC operon, mutation of the conserved residues in the RxxxR motif of the BcsA PilZ domain, or degradation of the cellulose produced by BcsA rescued the motility defect of Delta ycgR strains in which high c-di-GMP levels were reached through the overexpression of diguanylate cyclases. High c-di-GMP levels provoked cellulose accumulation around cells that impeded flagellar rotation, probably by means of steric hindrance, without affecting flagellum gene expression, exportation, or assembly. Our results highlight the relevance of cellulose in Salmonella lifestyle switching as an architectural element that is both essential for biofilm development and required, in collaboration with YcgR, for complete motility inhibition.