Journal of Microbiology

Journal Articles

Regulatory role of cysteines in (2R, 3R)-butanediol dehydrogenase BdhA of Bacillus velezensis strain GH1-13: Yunhee Choi , Yong-Hak Kim; J. Microbiol. 2022;60(4):411-418. Published online March 14, 2022; DOI: https://doi.org/10.1007/s12275-022-2018-y

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Abstract: Bacillus velezensis strain GH1-13 contains a (2R,3R)-butanediol dehydrogenase (R-BDH) BdhA which converts acetoin to R-BD reversibly, however, little is known about its regulatory cysteine and biological significance. We performed sitedirected mutation of three cysteines in BdhA. The C37S mutant had no enzyme activity and the C34S and C177S mutants differed from each other and wild type (WT). After zinc affinity chromatography, 1 mM ZnCl2 treatment resulted in a 3-fold enhancement of the WT activity, but reduced activity of the C34S mutant by more than 2 folds compared to the untreated ones. However, ZnCl2 treatment did not affect the activity of the C177S mutant. Most of the double and triple mutant proteins (C34S/C37S, C34S/C177S, C37S/C177S, and C34S/C37S/C177S) were aggregated in zinc resins, likely due to the decreased protein stability. All of the purified WT and single mutant proteins increased multiple intermolecular disulfide bonds in the presence of H2O2 as the buffer pH decreased from 7.5 to 5.5, whereas an intramolecular disulfide bond of cysteine 177 and another cysteine in the CGIC motif region was likely formed at pH higher than pKa of 7.5. When pH varied, WT and its C34S or C177S mutants reduced acetoin to R-BD at the optimum pH 5.5 and oxidized R-BD to acetoin at the optimum pH 10. This study demonstrated that cysteine residues in BdhA play a regulatory role for the production of acetoin and R-BD depending on pH as well as metal binding and oxidative stress.

Oxygen-mediated growth enhancement of an obligate anaerobic archaeon Thermococcus onnurineus NA1: Seong Hyuk Lee , Hwan Youn , Sung Gyun Kang , Hyun Sook Lee; J. Microbiol. 2019;57(2):138-142. Published online January 31, 2019; DOI: https://doi.org/10.1007/s12275-019-8592-y

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Abstract: Thermococcus onnurineus NA1, an obligate anaerobic hyperthermophilic archaeon, showed variable oxygen (O2) sensitivity depending on the types of substrate employed as an energy source. Unexpectedly, the culture with yeast extract as a sole energy source showed enhanced growth by 2-fold in the presence of O2. Genome-wide transcriptome analysis revealed the upregulation of several antioxidant-related genes encoding thioredoxin peroxidase (TON_0862), rubrerythrin (TON_0864), rubrerythrin-related protein (TON_0873), NAD(P)H rubredoxin oxidoreductase (TON_0865), or thioredoxin reductase (TON_1603), which can couple the detoxification of reactive oxygen species with the regeneration of NAD(P)+ from NAD(P)H. We present a plausible mechanism by which O2 serves to maintain the intracellular redox balance. This study demonstrates an unusual strategy of an obligate anaerobe underlying O2-mediated growth enhancement despite not having heme-based or cytochrome-type proteins.

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