Lerat Emmanuelle, Moran Nancy A
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA.
Mol Biol Evol. 2004 May;21(5):903-13. doi: 10.1093/molbev/msh097. Epub 2004 Mar 10.
Communication among bacterial cells through quorum-sensing (QS) systems is used to regulate ecologically and medically important traits, including virulence to hosts. QS is widespread in bacteria; it has been demonstrated experimentally in diverse phylogenetic groups, and homologs to the implicated genes have been discovered in a large proportion of sequenced bacterial genomes. The widespread distribution of the underlying gene families (LuxI/R and LuxS) raises the questions of how often QS genes have been transferred among bacterial lineages and the extent to which genes in the same QS system exchange partners or coevolve. Phylogenetic analyses of the relevant gene families show that the genes annotated as LuxI/R inducer and receptor elements comprise two families with virtually no homology between them and with one family restricted to the gamma-Proteobacteria and the other more widely distributed. Within bacterial phyla, trees for the LuxS and the two LuxI/R families show broad agreement with the ribosomal RNA tree, suggesting that these systems have been continually present during the evolution of groups such as the Proteobacteria and the Firmicutes. However, lateral transfer can be inferred for some genes (e.g., from Firmicutes to some distantly related lineages for LuxS). In general, the inducer/receptor elements in the LuxI/R systems have evolved together with little exchange of partners, although loss or replacement of partners has occurred in several lineages of gamma-Proteobacteria, the group for which sampling is most intensive in current databases. For instance, in Pseudomonas aeruginosa, a transferred QS system has been incorporated into the pathway of a native one. Gene phylogenies for the main LuxI/R family in Pseudomonas species imply a complex history of lateral transfer, ancestral duplication, and gene loss within the genus.
细菌细胞通过群体感应（QS）系统进行的通讯用于调节生态和医学上重要的性状，包括对宿主的毒力。QS在细菌中广泛存在；已在不同的系统发育群体中通过实验证明了这一点，并且在很大比例的已测序细菌基因组中发现了与相关基因同源的基因。潜在基因家族（LuxI/R和LuxS）的广泛分布引发了以下问题：QS基因在细菌谱系之间转移的频率有多高，以及同一QS系统中的基因交换伙伴或共同进化的程度如何。对相关基因家族的系统发育分析表明，被注释为LuxI/R诱导物和受体元件的基因包括两个几乎没有同源性的家族，其中一个家族仅限于γ-变形菌门，另一个分布更广泛。在细菌门内，LuxS和两个LuxI/R家族的树与核糖体RNA树显示出广泛的一致性，这表明这些系统在变形菌门和厚壁菌门等群体的进化过程中一直存在。然而，可以推断某些基因发生了横向转移（例如，对于LuxS，从厚壁菌门转移到一些远缘谱系）。一般来说，LuxI/R系统中的诱导物/受体元件一起进化，伙伴交换很少，尽管在γ-变形菌门的几个谱系中发生了伙伴的丢失或替换，在当前数据库中该群体的样本最为密集。例如，在铜绿假单胞菌中，一个转移的QS系统已被纳入一个原生系统的途径中。假单胞菌属中主要LuxI/R家族的基因系统发育暗示了该属内横向转移、祖先重复和基因丢失的复杂历史。
