This study investigates the effects of mutations in loci other than the kdpDE genes on kdp operon regulation in *Escherichia coli*. The researchers identified two new mutations, dke-1 and dke-2, which significantly reduce kdp expression. Dke-1 is located in the trxB gene, encoding thioredoxin 1, while dke-2 is in the hns gene, encoding the nucleoid protein H-NS. Both mutations affect kdp expression independently and are rescued by exogenous dithiothreitol, suggesting that they alter cytoplasmic thiol oxidation status. The study also found that the double mutant of trxB and hns has an even more severe reduction in kdp expression, indicating an additive effect of these mutations. Epistasis experiments show that the trxB and hns mutations act upstream of KdpD in the signal transduction pathway, suggesting that they influence kdp expression through mechanisms other than altering the strength of the environmental signal. The findings highlight the importance of cytoplasmic thiol oxidation status and the nucleoid protein H-NS in regulating kdp operon expression.This study investigates the effects of mutations in loci other than the kdpDE genes on kdp operon regulation in *Escherichia coli*. The researchers identified two new mutations, dke-1 and dke-2, which significantly reduce kdp expression. Dke-1 is located in the trxB gene, encoding thioredoxin 1, while dke-2 is in the hns gene, encoding the nucleoid protein H-NS. Both mutations affect kdp expression independently and are rescued by exogenous dithiothreitol, suggesting that they alter cytoplasmic thiol oxidation status. The study also found that the double mutant of trxB and hns has an even more severe reduction in kdp expression, indicating an additive effect of these mutations. Epistasis experiments show that the trxB and hns mutations act upstream of KdpD in the signal transduction pathway, suggesting that they influence kdp expression through mechanisms other than altering the strength of the environmental signal. The findings highlight the importance of cytoplasmic thiol oxidation status and the nucleoid protein H-NS in regulating kdp operon expression.