Dorosky Robert J, Yu Jun Myoung, Pierson Leland S, Pierson Elizabeth A
Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, USA.
Department of Horticultural Sciences, Texas A&M University, College Station, Texas, USA.
Appl Environ Microbiol. 2017 Jul 17;83(15). doi: 10.1128/AEM.00706-17. Print 2017 Aug 1.
R-type tailocins are high-molecular-weight bacteriocins that resemble bacteriophage tails and are encoded within the genomes of many species. In this study, analysis of the 30-84 R-tailocin gene cluster revealed that it contains the structural components to produce two R-tailocins of different ancestral origins. Two distinct R-tailocin populations differing in length were observed in UV-induced lysates of 30-84 via transmission electron microscopy. Mutants defective in the production of one or both R-tailocins demonstrated that the killing spectrum of each tailocin is limited to species. The spectra of pseudomonads killed by the two R-tailocins differed, although a few species were either killed by or insusceptible to both tailocins. Tailocin release was disrupted by deletion of the holin gene within the tailocin gene cluster, demonstrating that the lysis cassette is required for the release of both R-tailocins. The loss of functional tailocin production reduced the ability of 30-84 to compete with an R-tailocin-sensitive strain within biofilms and rhizosphere communities. Our study demonstrates that species can produce more than one functional R-tailocin particle sharing the same lysis cassette but differing in their killing spectra. This study provides evidence for the role of R-tailocins as determinants of bacterial competition among plant-associated in biofilms and the rhizosphere. Recent studies have identified R-tailocin gene clusters potentially encoding more than one R-tailocin within the genomes of plant-associated but have not demonstrated that more than one particle is produced or the ecological significance of the production of multiple R-tailocins. This study demonstrates for the first time that strains can produce two distinct R-tailocins with different killing spectra, both of which contribute to bacterial competition between rhizosphere-associated bacteria. These results provide new insight into the previously uncharacterized role of R-tailocin production by plant-associated species in bacterial population dynamics within surface-attached biofilms and on roots.
R型尾噬菌体素是一种高分子量的细菌素，类似于噬菌体尾部，由许多物种的基因组编码。在本研究中，对30-84 R型尾噬菌体素基因簇的分析表明，它包含产生两种不同祖先起源的R型尾噬菌体素的结构成分。通过透射电子显微镜在30-84的紫外线诱导裂解物中观察到了两种长度不同的独特R型尾噬菌体素群体。在一种或两种R型尾噬菌体素产生方面存在缺陷的突变体表明，每种尾噬菌体素的杀伤谱仅限于特定物种。两种R型尾噬菌体素杀死的假单胞菌谱不同，尽管有少数物种对两种尾噬菌体素均敏感或均不敏感。尾噬菌体素基因簇中孔蛋白基因的缺失破坏了尾噬菌体素的释放，表明裂解盒对于两种R型尾噬菌体素的释放都是必需的。功能性尾噬菌体素产生的丧失降低了30-84在生物膜和根际群落中与R型尾噬菌体素敏感菌株竞争的能力。我们的研究表明，特定物种可以产生不止一种功能性R型尾噬菌体素颗粒，它们共享相同的裂解盒，但杀伤谱不同。本研究为R型尾噬菌体素作为生物膜和根际中植物相关细菌间竞争的决定因素的作用提供了证据。最近的研究已经在植物相关细菌的基因组中鉴定出可能编码不止一种R型尾噬菌体素的基因簇，但尚未证明能产生不止一种颗粒或多种R型尾噬菌体素产生的生态意义。本研究首次证明，特定菌株可以产生两种具有不同杀伤谱的独特R型尾噬菌体素，这两种尾噬菌体素都有助于根际相关细菌之间的竞争。这些结果为植物相关细菌产生R型尾噬菌体素在附着于表面的生物膜和根上的细菌种群动态中以前未被表征的作用提供了新的见解。
