Elasri M, Delorme S, Lemanceau P, Stewart G, Laue B, Glickmann E, Oger P M, Dessaux Y
Institut des Sciences Végétales, CNRS UPR040, 91198 Gif-sur-Yvette Cedex, France.
Appl Environ Microbiol. 2001 Mar;67(3):1198-209. doi: 10.1128/AEM.67.3.1198-1209.2001.
A total of 137 soilborne and plant-associated bacterial strains belonging to different Pseudomonas species were tested for their ability to synthesize N-acyl-homoserine lactones (NAHL). Fifty-four strains synthesized NAHL. Interestingly, NAHL production appears to be more common among plant-associated than among soilborne Pseudomonas spp. Indeed, 40% of the analyzed Pseudomonas syringae strains produced NAHL which were identified most often as the short-chain NAHL, N-hexanoyl-L-homoserine lactone, N-(3-oxo-hexanoyl)-homoserine lactone, and N-(3-oxo-octanoyl)-L-homoserine lactone (no absolute correlation between genomospecies of P. syringae and their ability to produce NAHL could be found). Six strains of fluorescent pseudomonads, belonging to the species P. chlororaphis, P. fluorescens, and P. putida, isolated from the plant rhizosphere produced different types of NAHL. In contrast, none of the strains isolated from soil samples were shown to produce NAHL. The gene encoding the NAHL synthase in P. syringae pv. maculicola was isolated by complementation of an NAHL-deficient Chromobacterium mutant. Sequence analysis revealed the existence of a luxI homologue that we named psmI. This gene is sufficient to confer NAHL synthesis upon its bacterial host and has strong homology to psyI and ahlI, two genes involved in NAHL production in P. syringae pv. tabaci and P. syringae pv. syringae, respectively. We identified another open reading frame that we termed psmR, transcribed convergently in relation to psmI and partly overlapping psmI; this gene encodes a putative LuxR regulatory protein. This gene organization, with luxI and luxR homologues facing each other and overlapping, has been found so far only in the enteric bacteria Erwinia and Pantoea and in the related species P. syringae pv. tabaci.
对总共137株属于不同假单胞菌属的土壤源和植物相关细菌菌株进行了合成N-酰基高丝氨酸内酯（NAHL）能力的测试。54株菌株能够合成NAHL。有趣的是，与土壤源假单胞菌相比，NAHL的产生在植物相关假单胞菌中似乎更为常见。实际上，40%的分析丁香假单胞菌菌株产生NAHL，这些NAHL最常被鉴定为短链NAHL、N-己酰基-L-高丝氨酸内酯、N-（3-氧代己酰基）-高丝氨酸内酯和N-（3-氧代辛酰基）-L-高丝氨酸内酯（未发现丁香假单胞菌基因组种与其产生NAHL能力之间存在绝对相关性）。从植物根际分离出的6株荧光假单胞菌，分别属于绿针假单胞菌、荧光假单胞菌和恶臭假单胞菌，产生了不同类型的NAHL。相比之下，从土壤样品中分离出的菌株均未显示出产生NAHL的能力。通过对NAHL缺陷型嗜色菌突变体进行互补，分离出了丁香假单胞菌番茄致病变种中编码NAHL合酶的基因。序列分析揭示了一个luxI同源物的存在，我们将其命名为psmI。该基因足以使其细菌宿主产生NAHL，并且与丁香假单胞菌烟草致病变种和丁香假单胞菌丁香致病变种中参与NAHL产生的两个基因psyI和ahlI具有高度同源性。我们鉴定出另一个开放阅读框，我们将其命名为psmR，它与psmI反向转录且部分重叠；该基因编码一种假定的LuxR调节蛋白。到目前为止，这种luxI和luxR同源物相对且重叠的基因组织仅在肠道细菌欧文氏菌属和泛菌属以及相关物种丁香假单胞菌烟草致病变种中发现。
