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首页> 外文期刊>Applied Microbiology >A Novel Bacteriophage Exclusion (BREX) System Encoded by the pglX Gene in Lactobacillus casei Zhang
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A Novel Bacteriophage Exclusion (BREX) System Encoded by the pglX Gene in Lactobacillus casei Zhang

机译：干酪乳杆菌中pglX基因编码的新型噬菌体排除系统

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The bacteriophage exclusion (BREX) system is a novel prokaryotic defense system against bacteriophages. To our knowledge, no study has systematically characterized the function of the BREX system in lactic acid bacteria. Lactobacillus casei Zhang is a probiotic bacterium originating from koumiss. By using single-molecule real-time sequencing, we previously identified N6-methyladenine (m6A) signatures in the genome of L. casei Zhang and a putative methyltransferase (MTase), namely, pglX. This work further analyzed the genomic locus near the pglX gene and identified it as a component of the BREX system. To decipher the biological role of pglX, an L. casei Zhang pglX mutant (ΔpglX) was constructed. Interestingly, m6A methylation of the 5′-ACRCAG-3′ motif was eliminated in the ΔpglX mutant. The wild-type and mutant strains exhibited no significant difference in morphology or growth performance in de Man-Rogosa-Sharpe (MRS) medium. A significantly higher plasmid acquisition capacity was observed for the ΔpglX mutant than for the wild type if the transformed plasmids contained pglX recognition sites (i.e., 5′-ACRCAG-3′). In contrast, no significant difference was observed in plasmid transformation efficiency between the two strains when plasmids lacking pglX recognition sites were tested. Moreover, the ΔpglX mutant had a lower capacity to retain the plasmids than the wild type, suggesting a decrease in genetic stability. Since the Rebase database predicted that the L. casei PglX protein was bifunctional, as both an MTase and a restriction endonuclease, the PglX protein was heterologously expressed and purified but failed to show restriction endonuclease activity. Taken together, the results show that the L. casei Zhang pglX gene is a functional adenine MTase that belongs to the BREX system.IMPORTANCELactobacillus casei Zhang is a probiotic that confers beneficial effects on the host, and it is thus increasingly used in the dairy industry. The possession of an effective bacterial immune system that can defend against invasion of phages and exogenous DNA is a desirable feature for industrial bacterial strains. The bacteriophage exclusion (BREX) system is a recently described phage resistance system in prokaryotes. This work confirmed the function of the BREX system in L. casei and that the methyltransferase (pglX) is an indispensable part of the system. Overall, our study characterizes a BREX system component gene in lactic acid bacteria.
机译：噬菌体排斥（BREX）系统是针对噬菌体的新型原核防御系统。据我们所知，没有研究能系统地表征BREX系统在乳酸菌中的功能。 Casei Lactobacillus casei Zhang是起源于koumiss的益生菌。通过使用单分子实时测序，我们以前确定了干酪乳杆菌张氏基因组中的N6-甲基腺嘌呤（m6A）签名和一个假定的甲基转移酶（MTase），即pglX。这项工作进一步分析了pglX基因附近的基因组基因座，并将其鉴定为BREX系统的组成部分。为了破译pglX的生物学作用，构建了干酪乳杆菌Zhang pglX突变体（ΔpglX）。有趣的是，在ΔpglX突变体中消除了5'-ACRCAG-3'基序的m6A甲基化。在de Man-Rogosa-Sharpe（MRS）培养基中，野生型和突变菌株在形态或生长性能上均未显示出显着差异。如果转化的质粒包含pglX识别位点（即5'-ACRCAG-3'），则对于ΔpglX突变体观察到的质粒捕获能力比野生型高得多。相反，当测试缺少pglX识别位点的质粒时，在两个菌株之间的质粒转化效率上没有观察到显着差异。而且，ΔpglX突变体具有比野生型更低的保留质粒的能力，表明遗传稳定性降低。由于Rebase数据库预测干酪乳杆菌PglX蛋白具有MTase和限制性核酸内切酶双重功能，因此PglX蛋白被异源表达和纯化，但未显示限制性核酸内切酶活性。综上所述，结果表明，干酪乳杆菌pglX基因是属于BREX系统的功能性腺嘌呤MTase。重要干酪乳杆菌是一种对宿主具有有益作用的益生菌，因此在乳品工业中得到了越来越多的应用。拥有可以抵抗噬菌体和外源DNA入侵的有效细菌免疫系统，是工业细菌菌株的理想功能。噬菌体排斥（BREX）系统是原核生物中最近描述的噬菌体抗性系统。这项工作证实了干酪乳杆菌BREX系统的功能，并且甲基转移酶（pglX）是该系统不可或缺的部分。总体而言，我们的研究表征了乳酸菌中的BREX系统组成基因。

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