The haloalkalitolerant bacterium Egicoccus halophilus EGI 80432^T exhibits high adaptability to saline–alkaline environment. The salinity adaptation mechanism of E. halophilus EGI 80432^T was fully understood based on transcriptome analyses and physiological responses; however, the alkaline response mechanism has not yet been investigated. Here, we investigated the alkaline response mechanism of E. halophilus EGI 80432^T by a transcriptomic comparison. In this study, the genes involved in the glycolysis, TCA cycle, starch, and trehalose metabolism for energy production and storage, were up-regulated under highly alkaline condition. Furthermore, genes responsible for the production of acidic and neutral metabolites, i.e., acetate, pyruvate, formate, glutamate, threonine, and ectoine, showed increased expression under highly alkaline condition, compared with the control pH condition. In contrast, the opposite results were observed in proton capture or retention gene expression profiles, i.e., cation/proton antiporters and ATP synthases. The above results revealed that E. halophilus EGI 80432^T likely tended to adopt an “acidic metabolites production” strategy in response to a highly alkaline condition. These findings would pave the way for further studies in the saline–alkaline adaptation mechanisms of E. halophilus EGI 80432^T, and hopefully provide a new insight into the foundational theory and application in ecological restoration with saline–alkaline strains.

耐盐碱细菌Egicoccus halophilus EGI 80432 ^T对盐碱环境具有高度适应性。基于转录组分析和生理反应，E. halophilus EGI 80432 ^T的盐度适应机制得到了充分理解；然而，尚未研究碱性反应机制。在这里，我们研究了E. halophilus EGI 80432 ^T的碱性反应机制通过转录组比较。在这项研究中，参与糖酵解、TCA 循环、淀粉和海藻糖代谢以产生和储存能量的基因在高碱性条件下上调。此外，与对照 pH 条件相比，在高碱性条件下，负责产生酸性和中性代谢物（即乙酸盐、丙酮酸盐、甲酸盐、谷氨酸盐、苏氨酸和四氢嘧啶）的基因表达增加。相反，在质子捕获或保留基因表达谱中观察到相反的结果，即阳离子/质子反向转运蛋白和 ATP 合酶。以上结果表明，嗜盐大肠杆菌EGI 80432 ^T可能倾向于采用“酸性代谢物生产”策略来应对强碱性条件。这些发现将为进一步研究E. halophilus EGI 80432 ^T的盐碱适应机制铺平道路，并有望为盐碱菌株生态修复的基础理论和应用提供新的见解。