Wisniewski-Dyé Florence, Downie J Allan
Laboratoire d'Ecologie Microbienne, UMR-CNRS 5557, Université Lyon 1, Villeurbanne, France.
Antonie Van Leeuwenhoek. 2002 Aug;81(1-4):397-407. doi: 10.1023/a:1020501104051.
Quorum-sensing signals are found in many species of legume-nodulating rhizobia. In a well-characterized strain of R. leguminosarum biovar viciae, a variety of autoinducers are synthesised, and all have been identified as N-acyl-homoserine lactones. One of these N-acyl-homoserine lactones, is N-(3-hydroxy-7-cis-tetradecenoyl)-L-homoserine lactone, previously known as small bacteriocin, which inhibits the growth of several R. leguminosarum strains. The cinRI locus is responsible for the production of small bacteriocin. CinR induces cinl in response to the AHL made by Cinl, thus forming a positive autoregulatory induction loop. A complex cascade of quorum-sensing loops was characterized, in which the cinMR locus appears to be the master control for three other AHL-dependent quorum-sensing control systems. These systems include the rail/raiR, trallyriR and rhiI/rhiR. Other rhizobial strains appear to share some of these quorum sensing loci, but not all loci are found in all strains. Small bacteriocin along with the other N-acyl-homoserine lactones produced by these three AHL-based control systems regulate (i) growth inhibition of sensitive strains, (ii) transfer of the symbiotic plasmid pRL1JI, and (iii) expression of the rhizosphere-expressed (rhi) genes that influence nodulation. Some of the genes regulated by these systems have been identified. While the functions of some, such as the trb operon regulated by triR are clear, several of the regulated genes have no homologues of known function. It is anticipated that several other genes regulated by these systems have yet to be identified. Therefore, despite the regulation of one of the most complex quorum-sensing cascade being understood, several of the functions regulated by the quorum-sensing genes remain to be elucidated.
群体感应信号在许多豆科植物根瘤菌中都有发现。在一株特征明确的豌豆根瘤菌生物变种中，会合成多种自诱导物，并且所有这些自诱导物都已被鉴定为N-酰基高丝氨酸内酯。其中一种N-酰基高丝氨酸内酯是N-(3-羟基-7-顺式十四碳烯酰基)-L-高丝氨酸内酯，以前被称为小细菌素，它能抑制几种豌豆根瘤菌菌株的生长。cinRI基因座负责小细菌素的产生。CinR会响应CinI产生的AHL诱导cinI，从而形成一个正自调节诱导环。一个复杂的群体感应环级联反应被表征出来，其中cinMR基因座似乎是其他三个AHL依赖性群体感应控制系统的主控基因座。这些系统包括rail/raiR、trallyriR和rhiI/rhiR。其他根瘤菌菌株似乎共享其中一些群体感应基因座，但并非所有菌株都含有所有基因座。小细菌素以及由这三个基于AHL的控制系统产生的其他N-酰基高丝氨酸内酯调节：(i) 敏感菌株的生长抑制，(ii) 共生质粒pRL1JI的转移，以及(iii) 影响结瘤的根际表达(rhi)基因的表达。这些系统调节的一些基因已经被鉴定出来。虽然一些基因的功能，如由triR调节的trb操纵子的功能是明确的，但一些受调节的基因没有已知功能的同源物。预计这些系统调节的其他几个基因还有待鉴定。因此，尽管已经了解了最复杂的群体感应级联反应之一的调节机制，但群体感应基因调节的一些功能仍有待阐明。
