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.

Research Support, Non-U.S. Gov't

Heat Shock Causes Oxidative Stress and Induces a Variety of Cell Rescue Proteins in Saccharomyces cerevisiae KNU5377: Il-Sup Kim , Hye-Youn Moon , Hae-Sun Yun , Ingnyol Jin; J. Microbiol. 2006;44(5):492-501.; DOI: https://doi.org/2449 [pii]

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Abstract: In this study, we attempted to characterize the physiological response to oxidative stress by heat shock in Saccharomyces cerevisiae KNU5377 (KNU5377) that ferments at a temperature of 40°C. The KNU5377 strain evidenced a very similar growth rate at 40°C as was recorded under normal conditions. Unlike the laboratory strains of S. cerevisiae, the cell viability of KNU5377 was affected slightly under 2 hours of heat stress conditions at 43°C. KNU5377 evidenced a time-dependent increase in hydroperoxide levels, carbonyl contents, and malondialdehyde (MDA), which increased in the expression of a variety of cell rescue proteins containing Hsp104p, Ssap, Hsp30p, Sod1p, catalase, glutathione reductase, G6PDH, thioredoxin, thioredoxin peroxidase (Tsa1p), Adhp, Aldp, trehalose and glycogen at high temperature. Pma1/2p, Hsp90p and H+-ATPase expression levels were reduced as the result of exposure to heat shock. With regard to cellular fatty acid composition, levels of unsaturated fatty acids (USFAs) were increased significantly at high temperatures (43°C), and this was particularly true of oleic acid (C18:1). The results of this study indicated that oxidative stress as the result of heat shock may induce a more profound stimulation of trehalose, antioxidant enzymes, and heat shock proteins, as well as an increase in the USFAs ratios. This might contribute to cellular protective functions for the maintenance of cellular homeostasis, and may also contribute to membrane fluidity.

Protective Effects of Antoxidant Enzymes of Candida albicans against Oxidative Killing by Macrophages: Kim, Hye Jin , Na, Byoung Kuk , Kim, Moon Bo , Choi, Duk Young , Song, Chul Yong; J. Microbiol. 1999;37(2):117-122.

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Abstract: Protective roles of antioxidant enzymes, copper-zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD), and catalase of Candida albicans against exogenous reactive oxygens and oxidative killing by macrophages were investigated. The initial growth of C. albicans was inhibited by reactive, oxygen-producing chemicals such as hydrogen peroxide, pyrogallol, and paraquat, but it was restored as the production of antioxidant enzymes were increased. The growth inhibition of C. albicans by reactive, oxygen-producing chemicals was reduced by treating the purified candidal SOD and catalase. Also, in the presence of SOD and catalase, the oxidative killing of C. albicans by macrophages was significantly inhibited. These results suggest that antioxidant enzymes, CuZnSOD, MnSOD, and catalase of C. albicans may play important roles in the protection of C. albicans not only from exogenous oxidative stress but also from oxidative killing by macrophages.

Alterations in the Activities of Antioxidant Enzymes of Human Dermal Microvascular Endothelial Cells Infected with Orientia tsutsugamushi: Young-Sang Koh; J. Microbiol. 2001;39(2):142-145.

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Abstract: Changes in the activities of several antioxidant enzymes in transformed human dermal microvascular endothelial cells (HMEC-1) by infection with the obligate intracellular bacterium Orientia tsutsugamushi, the causative agent of scrub typhus, were investigated. The activities of glucose-6-phosphate dehydrogenase, catalase, and glutathione peroxidase were significantly decreased in HMEC-1 cells infected with O. tsutsugamushi. However, the level of superoxide dismutase increased slightly. Furthermore, increased levels of intracellular peroxide was observed in HMEC-1 during infection. These results support the hypothesis that cells infected by this intracellular bacterium experience oxidant-mediated injury that may eventually contribute to cell death.

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