The LysR-type transcriptional regulator (LTTR) AlsR indirectly regulates expression of the Bacillus subtilis bdhA gene encoding 2,3-butanediol dehydrogenase

Abstract

Bacillus subtilis ferments pyruvate to 2,3-butanediol via α-acetolactate synthase, α-acetolactate decarboxylase, and butanediol dehydrogenase (BDH), encoded by the alsSD operon and the unlinked monocistronic bdhA gene, respectively. Upstream and divergent from alsSD is the alsR gene that encodes AlsR, a member of the LysR-type transcriptional regulator family. AlsR directly stimulates alsSD transcription by binding to characteristic sites preceding the alsS promoter, but its effect on bdhA expression was unknown. The effect of AlsR on bdhA expression was assessed in a wild-type strain and a congenic strain carrying an alsR::spc knockout mutation by measuring: (a) expression of a transcriptional bdhA-lacZ fusion; (b) bdhA mRNA steady-state levels by quantitative reverse transcriptase PCR; and (c) expression of BDH enzymatic activity. Activation of bdhA expression occurred in early stationary phase, and expression was lowered, but not abolished, in the alsR::spc mutant. Mapping the transcriptional start site of bdhA by primer extension revealed a 268-nucleotide 5'-untranslated region preceding the bdhA initiation methionine codon. Transcription initiation was not reduced in the alsR::spc mutant, and by electrophoretic mobility shift assay, purified AlsR protein did not bind to the bdhA promoter region, suggesting that bdhA expression is indirectly under AlsR transcriptional control.

Comparison of Bacillus subtilis transcriptome profiles from two separate missions to the International Space Station

“…In addition, changes in cell physiology associated with the switch to oxygen limitation activate a transcriptional regulator called AlsR, which activates expression of alsSD directly 47,52 and bdhA indirectly. 53 Meanwhile, the regulatory protein Rex senses changes in the NAD + /NADH ratio brought on by oxygen limitation and responds by activating a number of genes including the cydABCD and ldh-lctP operons. 51 We were prompted by these observations to search for regulators of anaerobic gene expression in the datasets, and found significant upregulation of the arfM gene in BRIC-21 (Supplemental Table S1), the resD and resE genes in BRIC-23 (Supplemental Table S2), and the narK-fnr operon in both BRIC-21 and BRIC-23 GC samples (Table 2).…”

Metabolic engineering of Bacillus subtilis for chiral pure meso-2,3-butanediol production

“…As the direct precursor of 2,3-BD, acetoin (AC) formation from pyruvate was catalyzed in a two-step reaction by acetolactate synthase and acetolactate decarboxylase in B. subtilis , coded by alsS and alsD , respectively [ 26 ]. It was indicated that although the LysR-type transcriptional regulator AlsR protein (coded by alsR ) positively regulated the alsSD operon [ 27 , 28 ] in B. subtilis , it indirectly regulated the expression of bdhA (encoding 2,3-BD dehydrogenase/AC reductase) [ 29 ]. The biodegradation of AC was catabolized by the AC dehydrogenase enzyme system, and its core subunit encoded by acoA affects the dehydrogenase complex activity significantly [ 30 ].…”

Mechanism of microbial production of acetoin and 2,3-butanediol optical isomers and substrate specificity of butanediol dehydrogenase

“…AlsR, a protein homologous to the LysR family of bacterial transcriptional activators, is induced by acetate, low pH, and anaerobic environments. AlsR positively regulates the transcription of the alsSD operon in B. subtilis by interacting with a cis-acting region between the alsR and alsS genes,whose deletion results in the inactivation of alsSD operon expression [ 21 ]. In addition, the global regulator of carbon metabolism A (Catabolite control protein A, CcpA) has been shown to participate in the regulation of the alsSD operon [ 22 , 23 ].…”