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Korshunov S, Imlay JA. Antioxidants are ineffective at quenching reactive oxygen species inside bacteria and should not be used to diagnose oxidative stress. Mol Microbiol 2024; 122:113-128. [PMID: 38889382 DOI: 10.1111/mmi.15286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 05/31/2024] [Accepted: 06/03/2024] [Indexed: 06/20/2024]
Abstract
A wide variety of stresses have been proposed to exert killing effects upon bacteria by stimulating the intracellular formation of reactive oxygen species (ROS). A key part of the supporting evidence has often been the ability of antioxidant compounds to protect the cells. In this study, some of the most-used antioxidants-thiourea, glutathione, N-acetylcysteine, and ascorbate-have been examined. Their ability to quench superoxide and hydrogen peroxide was verified in vitro, but the rate constants were orders of magnitude too slow for them to have an impact upon superoxide and peroxide concentrations in vivo, where these species are already scavenged by highly active enzymes. Indeed, the antioxidants were unable to protect the growth and ROS-sensitive enzymes of E. coli strains experiencing authentic oxidative stress. Similar logic posits that antioxidants cannot substantially quench hydroxyl radicals inside cells, which contain abundant biomolecules that react with them at diffusion-limited rates. Indeed, antioxidants were able to protect cells from DNA damage only if they were applied at concentrations that slow metabolism and growth. This protective effect was apparent even under anoxic conditions, when ROS could not possibly be involved, and it was replicated when growth was similarly slowed by other means. Experimenters should discard the use of antioxidants as a way of detecting intracellular oxidative stress and should revisit conclusions that have been based upon such experiments. The notable exception is that these compounds can effectively degrade hydrogen peroxide from environmental sources before it enters cells.
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Affiliation(s)
- Sergey Korshunov
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - James A Imlay
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
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Liu T, Zheng X, Li X, Yang H, Zhi H, Tang G, Yang X, Liu Z, Wu H, Tian J. Acute impact of salinity and C/N ratio on the formation and properties of soluble microbial products from activated sludge. CHEMOSPHERE 2023; 330:138612. [PMID: 37028716 DOI: 10.1016/j.chemosphere.2023.138612] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 01/12/2023] [Accepted: 04/03/2023] [Indexed: 05/14/2023]
Abstract
The present study investigated the shock of NaCl and C/N ratio on properties of soluble microbial products (SMPs), focusing on their sized fractions. The results indicated that the NaCl stress increased the content of biopolymers, humic substances, building blocks, and LMW substances in SMPs, while the addition of 40 g NaCl L-1 significantly changed their relative abundance in SMPs. The acute impact of both N-rich and N-deficient conditions accelerated the secretion of SMPs, but the characteristics of LMW substances differed. Meanwhile, the bio-utilization of SMPs has been enhanced with the increase of NaCl dosage but decreased with the increase of the C/N ratio. The mass balance of sized fractions in SMPs + EPS could be set up when NaCl dosage <10 g/L and C/N ratio >5, which indicates the hydrolysis of sized fractions in EPS mainly compensated for their increase/reduction in SMPs. Besides, the results of the toxic assessment indicated that the oxidative damage caused by the NaCl shock was an important factor affecting the property of SMPs, and the abnormal expression of DNA transcription cannot be neglected for bacteria metabolisms with the change of C/N ratio.
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Affiliation(s)
- Tong Liu
- State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China
| | - Xing Zheng
- State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China; National Supervision & Inspection Center of Environmental Protection Equipment Quality, Jiangsu, Yixing, 214205, China.
| | - Xiaolin Li
- State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China
| | - Heyun Yang
- State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China
| | - Hegang Zhi
- College of Agricultural and Environmental Sciences, University of California, Davis, 95616, United States
| | - Gang Tang
- Earth and Atmospheric Sciences, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Xinyu Yang
- State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China
| | - Zhiqi Liu
- State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China
| | - Hua Wu
- State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China
| | - Jiayu Tian
- School of Civil and Transportation Engineering, Hebei University of Technology, Tianjin, 300401, China
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Akhova AV, Tkachenko AG. Cadaverine Biosynthesis in Escherichia сoli Adaptation to Hydrogen Peroxide. APPL BIOCHEM MICRO+ 2022. [DOI: 10.1134/s0003683822050039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Physiology and antioxidant activity of Pediococcus pentosaceus R1 and Lactobacillus fermentum R6 in response to lactic acid stress. Lebensm Wiss Technol 2021. [DOI: 10.1016/j.lwt.2021.111878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Cardoza E, Singh H. Involvement of CspC in response to diverse environmental stressors in Escherichia coli. J Appl Microbiol 2021; 132:785-801. [PMID: 34260797 DOI: 10.1111/jam.15219] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 07/07/2021] [Accepted: 07/12/2021] [Indexed: 12/23/2022]
Abstract
The ability of Escherichia coli surviving a cold shock lies mainly with the induction of a few Csps termed as 'Major cold shock proteins'. Regardless of high sequence similarity among the nine homologous members, CspC appears to be functionally diverse in conferring the cell adaptability to various stresses based on fundamental properties of the protein including nucleic acid binding, nucleic acid melting and regulatory activity. Spanning three different stress regulons of acid, oxidative and heat, CspC regulates gene expression and transcript stability of stress proteins and bestows upon the cell tolerance to lethal-inducing agents ultimately helping it adapt to severe environmental assaults. While its exact role in cellular physiology is still to be detailed, understanding the transcriptional and translational control will likely provide insights into the mechanistic role of CspC under stress conditions. To this end, we review the knowledge on stress protein regulation by CspC and highlight its activity in response to stressors thereby elucidating its role as a major Csp player in response to one too many environmental triggers. The knowledge presented here could see various downstream applications in engineering microbes for industrial, agricultural and research applications in order to achieve high product efficiency and to aid bacteria cope with environmentally harsh conditions.
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Affiliation(s)
- Evieann Cardoza
- Department of Biological Sciences, Sunandan Divatia School of Science, NMIMS Deemed to be University, Mumbai, India
| | - Harinder Singh
- Department of Biological Sciences, Sunandan Divatia School of Science, NMIMS Deemed to be University, Mumbai, India
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Zhang H, Xu J, Chen Q, Wang H, Kong B. Physiological, Morphological and Antioxidant Responses of Pediococcus pentosaceus R1 and Lactobacillus fermentum R6 Isolated from Harbin Dry Sausages to Oxidative Stress. Foods 2021; 10:foods10061203. [PMID: 34073637 PMCID: PMC8229211 DOI: 10.3390/foods10061203] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/24/2021] [Accepted: 05/24/2021] [Indexed: 02/01/2023] Open
Abstract
As functional starter cultures and potential probiotics, the ability of lactic acid bacteria to resist oxidative stress is essential to maintain viability and functional properties. This study investigates the effects of H2O2 at different concentrations (0, 1, 2, and 3 mM) on the physiological, morphological, and antioxidant properties of Pediococcus pentosaceus R1 and Lactobacillus fermentum R6 isolated from Harbin dry sausages. The increase in H2O2 concentration induced a significant increase in reactive oxygen species and a decrease in intracellular ATP levels (p < 0.05). Based on scanning electron microscopy, transmission electron microscopy, and electric conductivity analysis, H2O2 stress caused cell deformation, the destruction of cell membrane integrity, partial loss of the cytoplasm, and an increase in the cell conductivity of both strains. H2O2 stress with 1 mM or 2 mM concentrations could effectively improve the scavenging rates of free radicals, the activities of superoxide dismutase and glutathione peroxide, and the total antioxidant capacity of both strains (p < 0.05). In conclusion, an appropriate oxidative stress contributed to the activation of the antioxidant defense system of both strains, conferred strains a better effect in inhibiting the oxidation of fermented foods, and improved the health of the host.
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Affiliation(s)
| | | | | | | | - Baohua Kong
- Correspondence: ; Tel.: +86-4515-519-1794; Fax: +86-4515-519-0577
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