Department of Bacteriology, Hiroshima University Graduate School of Biomedical and Health Sciences, Hiroshima, Japan.
Department of Biological Endodontics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
Appl Environ Microbiol. 2024 Mar 20;90(3):e0208423. doi: 10.1128/aem.02084-23. Epub 2024 Feb 27.
is a cariogenic bacterium that produces a variety of bacteriocins and retains resistance to these bacteriocins. In this study, we investigated the susceptibility of 127 . strains to nukacins produced by spp., which are commensal bacteria in humans. We detected diverse susceptibilities among strains. Nineteen strains had a disrupted LctF (type I), which is responsible for nukacin susceptibility, whereas the remaining 108 strains had an intact LctF (type II) and displayed resistance to nukacins. However, the type I strains still showed resistance to nukacins to some extent. Interestingly, 18/19 (94.7%) type I strains carried a locus, which is related to the synthesis of mutacin K8, and , an ABC transporter. In contrast, among type II strains, only 6/108 strains (5.6%) had both the locus and , 19/108 strains (17.6%) carried only , and 83/108 strains (76.9%) harbored neither nor . We also found that MukF had two variants: 305 amino acids (type α) and 302 amino acids (type β). All type I strains showed a type α (MukFα), whereas most type II strains with (22/25 strains) had a type β (MukFβ). Then, we constructed a -deletion mutant complemented with MukFαEG or MukFβEG and found that only MukFαEG was involved in nukacin resistance. The nukacin resistance capability of type II-LctFEG was stronger than that of MukFαEG. In conclusion, we identified a novel nukacin resistance factor, MukFEG, and either LctFEG or MukFEG was active in most strains via genetic polymorphisms depending on genes.
is an important pathogenic bacterium not only for dental caries but also for systemic diseases. is known to produce a variety of bacteriocins and to retain resistance these bacteriocins. In this study, two ABC transporters, LctFEG and MukFEG, were implicated in nukacin resistance and each ABC transporter has two subtypes, active and inactive. Of the two ABC transporters, only one ABC transporter was always resistant, while the other ABC transporter was inactivated by genetic mutation. Interestingly, this phenomenon was defined by the presence or absence of the mutacin K8 synthesis gene region, one of the bacteriocins of . This suggests that the resistance acquisition is tightly controlled in each strain. This study provides important evidence that the insertion of bacteriocin synthesis genes is involved in the induction of genetic polymorphisms and suggests that bacteriocin synthesis genes may play an important role in bacterial evolution.
是一种致龋菌，可产生多种细菌素，并保留对这些细菌素的抗性。在这项研究中，我们调查了 127 株 对由人类共生菌 产生的 nukacins 的敏感性。我们在菌株中检测到了不同的敏感性。19 株的 LctF（I 型）中断，负责 nukacin 敏感性，而其余 108 株具有完整的 LctF（II 型）并对 nukacins 表现出抗性。然而，I 型菌株在某种程度上仍对 nukacins 表现出抗性。有趣的是，18/19（94.7%）I 型菌株携带 基因座，与 mutacin K8 和 的合成有关， 是一种 ABC 转运蛋白。相比之下，在 II 型菌株中，只有 6/108 株（5.6%）同时具有 基因座和 ，19/108 株（17.6%）仅携带 ，而 83/108 株（76.9%）既没有 也没有 。我们还发现 MukF 有两种变体：305 个氨基酸（类型 α）和 302 个氨基酸（类型 β）。所有 I 型菌株均显示出类型 α（MukFα），而大多数具有 （25 株中的 22 株）的 II 型菌株具有类型 β（MukFβ）。然后，我们构建了一个缺失突变体，用 MukFαEG 或 MukFβEG 进行了互补，并发现只有 MukFαEG 参与了 nukacin 抗性。II 型-LctFEG 的 nukacin 抗性能力强于 MukFαEG。总之，我们鉴定了一种新型 nukacin 抗性因子 MukFEG，并且取决于 基因，遗传多态性使大多数菌株中的 LctFEG 或 MukFEG 发挥作用。
不仅是导致龋齿的重要病原菌，也是导致全身疾病的重要病原菌。已知 可产生多种细菌素并保留对这些细菌素的抗性。在这项研究中，两种 ABC 转运蛋白，LctFEG 和 MukFEG，与 nukacin 抗性有关，每个 ABC 转运蛋白都有两种亚型，活性和非活性。在这两种 ABC 转运蛋白中，只有一种 ABC 转运蛋白始终具有抗性，而另一种 ABC 转运蛋白则因遗传突变而失活。有趣的是，这种现象由 mutacin K8 合成基因区域的存在或不存在定义，该区域是 的一种细菌素。这表明每个菌株的抗性获得都受到严格控制。本研究提供了重要证据，证明细菌素合成基因的插入参与了遗传多态性的诱导，并表明细菌素合成基因可能在细菌进化中发挥重要作用。
