# Genetic characteristics of novel extreme alkaline-inducible promoter located in five prime upstream region of peptidyl-prolyl cis/trans isomerase from Vibrio anguillarum

## TL;DR

This paper identifies a promoter in a bacteria that activates under extreme alkaline conditions, which could be useful for biotech applications.

## Contribution

The study identifies a novel promoter region in Vibrio anguillarum that is inducible under extreme alkaline stress.

## Key findings

- The promoter region of VaFklB is upregulated under extreme alkaline conditions (pH 10).
- β-galactosidase activity increased significantly at pH 9 and pH 10 compared to normal conditions.
- The promoter system has potential for biotechnological applications like pH-responsive gene expression.

## Abstract

This study presents the identification and characterization of the promoter region of Vibrio anguillarum NB10, which enhances the expression of FK506-binding protein (FKBP)-type peptidyl-prolyl cis/trans isomerase (PPIase; FklB), capable of binding to the immunosuppressant FK506 under extremely alkaline conditions. Our proteomic analysis of V. anguillarum NB10 revealed that FklB (VaFklB) expression is significantly upregulated under extreme alkaline stress (pH 10). When the putative core promoter regions were coupled with a β-galactosidase reporter gene and introduced into Escherichia coli, we observed β-galactosidase activities of 61.47 ± 2.91 and 95.83 ± 6.76 Miller units (MU) at pH 9 and 10, respectively, after 4 h of stress exposure. These values represent 1.97- and 2.88-fold increases compared to normal conditions (25 °C, pH 7: 31.27 ± 1.15 MU). This alkaline-inducible promoter system has potential for biotechnological applications, including the development of pH-responsive gene expression systems, biomanufacturing processes requiring alkaline environments, and targeted activation of silent biosynthetic gene clusters for novel bioactive compound discovery. Our findings provide a valuable molecular tool for synthetic biology and metabolic engineering, enabling precise genetic control under specific environmental conditions that may revolutionize industrial biotechnology.

The online version contains supplementary material available at 10.1038/s41598-025-98559-y.