Three Distinct Two-Component Systems Are Involved in Resistance to the Class I Bacteriocins, Nukacin ISK-1 and Nisin A, in Staphylococcus aureus

Staphylococcus aureus uses two-component systems (TCSs) to adapt to stressful environmental conditions. To colonize a host, S. aureus must resist bacteriocins produced by commensal bacteria. In a comprehensive analysis using individual TCS inactivation mutants, the inactivation of two TCSs, graRS and braRS, significantly increased the susceptibility to the class I bacteriocins, nukacin ISK-1 and nisin A, and inactivation of vraSR slightly increased the susceptibility to nukacin ISK-1. In addition, two ABC transporters (BraAB and VraDE) regulated by BraRS and one transporter (VraFG) regulated by GraRS were associated with resistance to nukacin ISK-1 and nisin A. We investigated the role of these three TCSs of S. aureus in co-culture with S. warneri, which produces nukacin ISK-1, and Lactococcus lactis, which produces nisin A. When co-cultured with S. warneri or L. lactis, the braRS mutant showed a significant decrease in its population compared with the wild-type, whereas the graRS and vraSR mutants showed slight decreases. Expression of vraDE was elevated significantly in S. aureus co-cultured with nisin A/nukacin ISK-1-producing strains. These results suggest that three distinct TCSs are involved in the resistance to nisin A and nukacin ISK-1. Additionally, braRS and its related transporters played a central role in S. aureus survival in co-culture with the strains producing nisin A and nukacin ISK-1.金黄色葡萄球菌（Staphylococcus aureus）借助双组分系统（two-component systems, TCSs）适应胁迫环境。为实现宿主定殖，S. aureus必须抵御共生菌产生的细菌素。本研究通过构建单个双组分系统失活突变体开展全面分析，结果显示graRS与braRS这两个双组分系统的失活，会显著提升菌株对I类细菌素nukacin ISK-1与nisin A的敏感性；而vraSR的失活仅小幅增加菌株对nukacin ISK-1的敏感性。此外，由BraRS调控的两种ATP结合盒（ATP-binding cassette, ABC）转运蛋白（BraAB与VraDE），以及由GraRS调控的一种转运蛋白（VraFG），均与S. aureus对nukacin ISK-1和nisin A的抗性相关。我们进一步探究了S. aureus的这三种双组分系统，在与产nukacin ISK-1的沃氏葡萄球菌（Staphylococcus warneri）、产nisin A的乳酸乳球菌（Lactococcus lactis）共培养过程中的作用。当与沃氏葡萄球菌或乳酸乳球菌共培养时，braRS突变体的种群数量相较于野生型菌株出现显著下降，而graRS与vraSR突变体的种群数量仅出现小幅降低。在与产nisin A或nukacin ISK-1的菌株共培养时，S. aureus中vraDE的表达水平显著上调。上述结果表明，三种不同的双组分系统均参与了S. aureus对nisin A与nukacin ISK-1的抗性过程。此外，braRS及其调控的转运蛋白在S. aureus与产nisin A、nukacin ISK-1的菌株共培养时的存活过程中发挥核心作用。