Discovery and Functional Characterization of Salinity-Responsive Promoters in Pseudomonas putida KT2440

Abstract Microbial bioprocesses are associated with environmental advantages, but their freshwater demand remains a challenge. Seawater is abundant and a sustainable alternative; however, high salinity often limits microbial growth and survival. This study aimed to identify biological parts involved in microbial salt stress responses for applications in microbial engineering. Regulatory regions adjacent to genes related to salinity and other industrially relevant conditions in Pseudomonas putida KT2440 were cloned into a reporter plasmid for functional evaluation. We identified and characterized the promoters of PP_1833 and PP_4707 as salt-inducible in KT2440, showing fluorescence levels 1.9- and 2.8-fold greater than a standard strong constitutive promoter (Pj100) under 3.5% NaCl (w/v), respectively, while no activity was detected in Escherichia coli DH10B. These results provide a basis for developing salt-responsive regulatory circuits in P. putida KT2440. Competing Interest Statement The authors have declared no competing interest.