Abstract

The halophilic lactic acid bacterium Tetragenococcus halophilus has been widely used in high-salinity fermentation processes of food. Previous studies have indicated that the catabolism of arginine may contribute to the osmotic stress adaptation of T. halophilus. Unusually, in the chromosome of T. halophilus, preceding the arginine deiminase (ADI) operon, locate two co-transcribed genes, both encoding an ArgR regulator; similar structure was rarely found and the roles of the regulators have not been demonstrated. In the current study, regulatory roles of these two nonidentical ArgR regulators on the arginine metabolism of T. halophilus were investigated. The results show that these two regulators play different roles in arginine metabolism, ArgR1 acts as a negative regulator of the ADI pathway by binding to the promoter sequences and repressing the transcription of genes, and the addition of arginine or hyper-osmotic stress conditions can abolish the ArgR1 repression, whereas ArgR2 negatively regulates the genes involved in arginine biosynthesis. Our study found that despite the commonly known roles of the ArgR regulators as the activator of arginine catabolism and the repressor of arginine biosynthesis, which are found in most studied bacteria possessed one ArgR regulator, the two nonidentical ArgR regulators of T. halophilus both act as repressors, and the repression by which is regulated when sensing changes of environments. By revealing the regulation of arginine metabolism, the current study provides molecular insights and potential tools for future applications of halophiles in biotechnology.

Key points

• The expression of the ADI pathway of T. halophilus is regulated by carbon sources and osmotic stress.

• The arginine metabolism process of T. halophilus is fine-tuned by the two ArgR regulators.

• The ADI pathway may contribute to the osmotic stress adaptation by generating more energy and accumulating citrulline which acts as compatible solute.

中文翻译：

---

嗜盐四核球菌的两个不同的ArgR调节剂的表征及其对精氨酸代谢的调节作用。

摘要

嗜盐乳酸菌嗜盐球菌已被广泛用于食品的高盐度发酵过程中。以前的研究表明精氨酸的分解代谢可能有助于T. halophilus的渗透胁迫适应。不同寻常的是，在精氨酸脱亚氨酶（ADI）操纵子之前的嗜盐丁酸杆菌的染色体中，存在两个共同转录的基因，两个基因都编码一个ArgR调控子。很少发现类似的结构，并且尚未证明监管机构的作用。在当前的研究中，这两个不同的ArgR调节剂对嗜盐丁酸杆菌精氨酸代谢的调节作用被调查了。结果表明，这两种调节剂在精氨酸代谢中发挥不同的作用，ArgR1通过与启动子序列结合并抑制基因的转录而成为ADI途径的负调节剂，而添加精氨酸或高渗胁迫条件可以废除ArgR1抑制，而ArgR2负调控精氨酸生物合成中涉及的基因。我们的研究发现，尽管在大多数研究细菌中发现ArgR调节剂作为精氨酸分解代谢的激活剂和精氨酸生物合成的阻遏剂的众所周知的作用，但它们具有一种ArgR调节剂，而嗜盐丁酸球的两种不同ArgR调节剂。两者都起着抑制器的作用，并且在感测环境变化时通过这种抑制来调节。通过揭示精氨酸代谢的调控，本研究为嗜盐菌在生物技术中的未来应用提供了分子见解和潜在工具。

关键点

•嗜盐杆菌的ADI途径的表达受碳源和渗透压的调节。

•通过两个ArgR调节剂微调嗜盐丁酸杆菌的精氨酸代谢过程。

•ADI途径可能通过产生更多的能量并积累瓜氨酸作为亲和溶质，从而促进渗透压的适应。