The ldhA Gene Encoding Fermentative l-Lactate Dehydrogenase in Corynebacterium Glutamicum Is Positively Regulated by the Global Regulator GlxR

Abstract

Bacterial metabolism shifts from aerobic respiration to fermentation at the transition from exponential to stationary growth phases in response to limited oxygen availability. Corynebacterium glutamicum, a Gram-positive, facultative aerobic bacterium used for industrial amino acid production, excretes L-lactate, acetate, and succinate as fermentation products. The ldhA gene encoding L-lactate dehydrogenase is solely responsible for L-lactate production. Its expression is repressed at the exponential phase and prominently induced at the transition phase. ldhA is transcriptionally repressed by the sugar-phosphate-responsive regulator SugR and L-lactate-responsive regulator LldR. Although ldhA expression is derepressed even at the exponential phase in the sugR and lldR double deletion mutant, a further increase in its expression is still observed at the stationary phase, implicating the action of additional transcription regulators. In this study, involvement of the cAMP receptor protein-type global regulator GlxR in the regulation of ldhA expression was investigated. The GlxR-binding site found in the ldhA promoter was modified to inhibit or enhance binding of GlxR. The ldhA promoter activity and expression of ldhA were altered in proportion to the binding affinity of GlxR. Similarly, L-lactate production was also affected by the binding site modification. Thus, GlxR was demonstrated to act as a transcriptional activator of ldhA.

Staphylococcus epidermidis biofilms undergo metabolic and matrix remodeling under nitrosative stress

“…Another explanation for the observed increase in lactate production in 1457-forming biofilms exposed to NO could be that lactate derives from d -lactate dehydrogenase rather than l -lactate dehydrogenase, whose activities lead to the formation of d -lactate and l -lactate isomers, respectively, that cannot be distinguished in the 1 H-NMR spectra, as they resonate in similar spectral regions under the NMR-acquiring conditions. However, to our knowledge, in contrast with L- ldh , transcriptional regulatory mechanisms of D- ldh genes have never been reported for Gram-positive bacteria ( Feldman-Salit et al., 2013 ; Toyoda and Inui, 2021 ; Ma et al., 2022 ).…”

“…As S. epidermidis biofilms exposed to NO showed higher lactate accumulation, we investigated whether this increase could be related to the induced expression of ldh gene encoding the l -lactate dehydrogenase enzyme ( Figure 1 ). l -Ldh has been linked to drug resistance and is considered a possible target of regulatory control in many bacterial species, including in coagulase-negative staphylococci ( Richardson et al., 2008 ; Toyoda and Inui, 2021 ; Ma et al., 2022 ; Yuan et al., 2022 ). For this purpose, biofilms of strains 1457 and RP62A, treated with NO or left untreated and grown for 24 h, were used to extract total RNA and evaluate ldh expression by RT-qPCR.…”

Use of the mCherry fluorescent protein to optimize the expression of class I lanthipeptides in Escherichia coli

“…Naturally, the STldh promoter transcriptionally controls the ldhA (L-lactate dehydrogenase) gene responsible for the production of l -lactate as a fermentation by-product when metabolism transitions from exponential to stationary growth phase [ 41 ]. However, it was shown that the ldhA gene in C. glutamicum is positively regulated by the cAMP receptor protein-type global regulator GlxR [ 51 ]. Similarly, the widely available lac and lacUV5 inducible promoters used in E. coli DE3 lysogens are controlled positively by the presence of high levels of cAMP and cAMP receptor protein (CAP) when glucose levels decrease in the expression media, also known as catabolite repression [ 30 , 52 ].…”