摘要

s型脓菌素是由铜绿假单胞菌分离株产生的细菌素，用于拮抗或杀死同一物种的其他菌株。它们具有模块化组织，包括识别靶细菌表面成分的受体结合结构域、通过周质转运的结构域以及具有DNase、tRNase或成孔活性的杀伤或毒性结构域。脓毒症S2、S3、S4和S5识别外膜中的TonB依赖性铁载体受体。我们在这里描述了一种新的核酸酶细菌素，化脓性链球菌S6，编码在铜绿假单胞菌囊性纤维化( CF )临床分离株CF _ PA39的基因组中。与脓毒症S1和S2相似，S6毒素-免疫基因串联被募集到编码外毒素a的基因组区域，脓毒症S6受体结合和易位结构域与脓毒症S1相同，而杀伤结构域与大肠杆菌大肠杆菌E3的16S核糖核酸酶结构域相似。随着大肠杆菌素E3等效催化基序的突变，脓菌素S6形式的细胞毒性活性被消除。CF _ PA39 S6免疫基因的表达水平高于编码杀伤蛋白的基因，后者只有在铁限制条件下培养细菌时才能检测到。在S1 -绿脓杆菌ATCC 25254和绿脓杆菌S2产生菌绿脓杆菌pao 1中，绿脓杆菌S6杀伤结构域的残体和完整的S6 -型免疫基因位于它们各自的绿脓杆菌操作子的下游。菌株pao 1对脓菌素S6不敏感，其S6型免疫基因对脓菌素S6活性具有保护作用。纯化的绿脓菌素S6抑制110株铜绿假单胞菌CF临床分离株的五分之一，当靶细胞在铁限制下生长时，显示出更清晰的抑制区。在这个小组中，发现大约一半的CF临床分离株含有S6基因。化脓性链球菌S6基因座也存在于一些非CF临床分离株的基因组中。

S‐type pyocins are bacteriocins produced by Pseudomonas aeruginosa isolates to antagonize or kill other strains of the same species. They have a modular organization comprising a receptor‐binding domain recognizing a surface constituent of the target bacterium, a domain for translocation through the periplasm, and a killing or toxic domain with DNase, tRNase, or pore‐forming activity. Pyocins S2, S3, S4, and S5 recognize TonB‐dependent ferri‐siderophore receptors in the outer membrane. We here describe a new nuclease bacteriocin, pyocin S6, encoded in the genome of a P. aeruginosa cystic fibrosis (CF) clinical isolate, CF_PA39. Similarly to pyocins S1 and S2, the S6 toxin–immunity gene tandem was recruited to the genomic region encoding exotoxin A. The pyocin S6 receptor‐binding and translocation domains are identical to those of pyocin S1, whereas the killing domain is similar to the 16S ribonuclease domain ofEscherichia coli colicin E3. The cytotoxic activity was abolished in pyocin S6 forms with a mutation in the colicin E3‐equivalent catalytic motif. The CF_PA39 S6 immunity gene displays a higher expression level than the gene encoding the killing protein, the latter being only detected when bacteria are grown under iron‐limiting conditions. In the S1‐pyocinogenic strain P. aeruginosa ATCC 25324 and pyocin S2 producer P. aeruginosaPAO1, a remnant of the pyocin S6 killing domain and an intact S6‐type immunity gene are located downstream of their respective pyocin operons. Strain PAO1 is insensitive for pyocin S6, and its S6‐type immunity gene provides protection against pyocin S6 activity. Purified pyocin S6 inhibits one‐fifth of 110 P. aeruginosa CF clinical isolates tested, showing clearer inhibition zones when the target cells are grown under iron limitation. In this panel, about half of the CF clinical isolates were found to host the S6 genes. The pyocin S6 locus is also present in the genome of some non‐CF clinical isolates.

https://onlinelibrary.wiley.com/doi/full/10.1002/mbo3.339