Ghequire Maarten G K, Dillen Yörg, Lambrichts Ivo, Proost Paul, Wattiez Ruddy, De Mot René
Centre of Microbial and Plant Genetics (CMPG), University of Leuven, Heverlee, Belgium
Group of Morphology, Biomedical Research Institute (BIOMED), Hasselt University, Diepenbeek, Leuven, Belgium.
Genome Biol Evol. 2015 Sep 26;7(10):2810-28. doi: 10.1093/gbe/evv184.
Bacterial genomes accommodate a variety of mobile genetic elements, including bacteriophage-related clusters that encode phage tail-like protein complexes playing a role in interactions with eukaryotic or prokaryotic cells. Such tailocins are unable to replicate inside target cells due to the lack of a phage head with associated DNA. A subset of tailocins mediate antagonistic activities with bacteriocin-like specificity. Functional characterization of bactericidal tailocins of two Pseudomonas putida rhizosphere isolates revealed not only extensive similarity with the tail assembly module of the Pseudomonas aeruginosa R-type pyocins but also differences in genomic integration site, regulatory genes, and lytic release modules. Conversely, these three features are quite similar between strains of the P. putida and Pseudomonas fluorescens clades, although phylogenetic analysis of tail genes suggests them to have evolved separately. Unlike P. aeruginosa R pyocin elements, the tailocin gene clusters of other pseudomonads frequently carry cargo genes, including bacteriocins. Compared with P. aeruginosa, the tailocin tail fiber sequences that act as specificity determinants have diverged much more extensively among the other pseudomonad species, mostly isolates from soil and plant environments. Activity of the P. putida antibacterial particles requires a functional lipopolysaccharide layer on target cells, but contrary to R pyocins from P. aeruginosa, strain susceptibilities surpass species boundaries.
细菌基因组容纳了多种可移动遗传元件，包括与噬菌体相关的基因簇，这些基因簇编码在与真核细胞或原核细胞相互作用中起作用的噬菌体尾样蛋白复合物。由于缺乏带有相关DNA的噬菌体头部，此类尾丝菌素无法在靶细胞内复制。一部分尾丝菌素介导具有类细菌素特异性的拮抗活性。对两种恶臭假单胞菌根际分离株的杀菌尾丝菌素进行功能表征，结果不仅显示其与铜绿假单胞菌R型绿脓菌素的尾部组装模块有广泛相似性，而且在基因组整合位点、调控基因和裂解释放模块方面存在差异。相反，恶臭假单胞菌和荧光假单胞菌分支的菌株之间，这三个特征相当相似，尽管对尾部基因的系统发育分析表明它们是独立进化的。与铜绿假单胞菌R型绿脓菌素元件不同，其他假单胞菌的尾丝菌素基因簇经常携带包括细菌素在内的货物基因。与铜绿假单胞菌相比，作为特异性决定因素的尾丝菌素尾纤维序列在其他假单胞菌物种（大多是从土壤和植物环境中分离出来的）中差异更大。恶臭假单胞菌抗菌颗粒的活性需要靶细胞上有功能正常的脂多糖层，但与铜绿假单胞菌的R型绿脓菌素不同，菌株敏感性跨越了物种界限。
