Gene Expression of Ethanol and Acetate Metabolic Pathways in the Acinetobacter baumannii EmaSR Regulon

Previous studies have confirmed the involvement of EmaSR (ethanol metabolism a sensor/regulator) in the regulation of Acinetobacter baumannii ATCC 19606 ethanol and acetate metabolism. RNA-seq analysis further revealed that DJ41_568-571, DJ41_2796, DJ41_3218, and DJ41_3568 regulatory gene clusters potentially participate in ethanol and acetate metabolism under the control of EmaSR.

This study fused the EmaSR regulon promoter segments with reporter genes and used fluorescence expression levels to determine whether EmaSR influences regulon expression in ethanol or acetate salt environments. The enzymatic function and kinetics of significantly regulated regulons were also studied.

The EmaSR regulons P and P exhibited > 2-fold increase in fluorescence expression in wild type compared to mutant strains in both ethanol and acetate environments, and P demonstrated a comparable trend. Moreover, increases in DJ41_2796 concentration enhanced the conversion of acetate and succinyl-CoA into acetyl-CoA and succinate, suggesting that DJ41_2796 possesses acetate: succinyl-CoA transferase (ASCT) activity. The k_cat/K_M values for DJ41_2796 with potassium acetate, sodium acetate, and succinyl-CoA were 0.2131, 0.4547, and 20.4623 mM^-1s^-1, respectively.

In A. baumannii, EmaSR controls genes involved in ethanol and acetate metabolism, and the EmaSR regulon DJ41_2796 was found to possess ASCT activity.