The well-known Crp/Fnr family regulator Fnr has long been recognized as an oxygen sensor to regulate multiple biological processes, including the switch between aerobic/anaerobic metabolism, nitrogen fixation, bioluminescence, infection, and virulence. In most cases, Fnr was found to be active under anaerobic conditions. However, its role in aerobic antibiotic metabolism has not yet been revealed. In this research, we report that in the model organism, Serratia sp. ATCC 39006, Fnr (Ser39006_013370) negatively regulates prodigiosin production by binding to the spacer between the −10 and −35 region in the promoter of prodigiosin biosynthetic gene cluster under aerobic conditions. Fnr was also shown to modulate the anti-bacterial activity and motility by regulating pathway-specific regulatory genes, indicating that Fnr acts as a global regulator in Serratia sp. ATCC 39006. For the first time, we describe that Fnr regulates antibiotic synthesis in the presence of oxygen, which expands the known physiological functions of Fnr and benefits the further investigation of this important transcriptional regulator.

众所周知的 Crp/Fnr 家族调节因子 Fnr 长期以来一直被认为是调节多种生物过程的氧传感器，包括需氧/厌氧代谢、固氮、生物发光、感染和毒力之间的转换。在大多数情况下，发现 Fnr 在厌氧条件下是活跃的。然而，其在有氧抗生素代谢中的作用尚未揭示。在这项研究中，我们报告说，在模式生物中，沙雷氏菌sp. ATCC 39006, Fnr (Ser39006_013370) 在有氧条件下通过与灵菌红素生物合成基因簇启动子中 -10 和 -35 区之间的间隔区结合，负调节灵菌红素的产生。Fnr 还显示出通过调节通路特异性调节基因来调节抗菌活性和运动性，表明 Fnr 在沙雷氏菌sp. ATCC 39006。我们首次描述了 Fnr 在有氧的情况下调节抗生素合成，这扩展了 Fnr 的已知生理功能，并有利于进一步研究这一重要的转录调节因子。