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      Roles of the Two-MnSOD System of Stenotrophomonas maltophilia in the Alleviation of Superoxide Stress

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          Abstract

          Manganese-dependent superoxide dismutase (MnSOD, SodA) and iron-dependent SOD (FeSOD, SodB) are critical cytosolic enzymes for alleviating superoxide stress. Distinct from the singular sodA gene in most bacteria, Stenotrophomonas maltophilia harbors two sodA genes, sodA1 and sodA2. The roles of SodA1, SodA2, and SodB of S. maltophilia in alleviating superoxide stress were investigated. The expression of sod genes was determined by promoter– xylE transcriptional fusion assay and qRT–PCR. SodA2 and sodB expressions were proportional to the bacterial logarithmic growth, but unaffected by menadione (MD), iron, or manganese challenges. SodA1 was intrinsically unexpressed and inducibly expressed by MD. Complementary expression of sodA1 was observed when sodA2 was inactivated. The individual or combined sod deletion mutants were constructed using the gene replacement strategy. The functions of SODs were assessed by evaluating cell viabilities of different sod mutants in MD, low iron-stressed, and/or low manganese-stressed conditions. Inactivation of SodA1 or SodA2 alone did not affect bacterial viability; however, simultaneously inactivating sodA1 and sodA2 significantly compromised bacterial viability in both aerobic growth and stressed conditions. SodA1 can either rescue or support SodA2 when SodA2 is defective or insufficiently potent. The presence of two MnSODs gives S. maltophilia an advantage against superoxide stress.

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          Most cited references23

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          Superoxide radical and superoxide dismutases.

          O2- oxidizes the [4Fe-4S] clusters of dehydratases, such as aconitase, causing-inactivation and release of Fe(II), which may then reduce H2O2 to OH- +OH.. SODs inhibit such HO. production by scavengingO2-, but Cu, ZnSODs, by virtue of a nonspecific peroxidase activity, may peroxidize spin trapping agents and thus give the appearance of catalyzing OH. production from H2O2. There is a glycosylated, tetrameric Cu, ZnSOD in the extracellular space that binds to acidic glycosamino-glycans. It minimizes the reaction of O2- with NO. E. coli, and other gram negative microorganisms, contain a periplasmic Cu, ZnSOD that may serve to protect against extracellular O2-. Mn(III) complexes of multidentate macrocyclic nitrogenous ligands catalyze the dismutation of O2- and are being explored as potential pharmaceutical agents. SOD-null mutants have been prepared to reveal the biological effects of O2-. SodA, sodB E. coli exhibit dioxygen-dependent auxotrophies and enhanced mutagenesis, reflecting O2(-)-sensitive biosynthetic pathways and DNA damage. Yeast, lacking either Cu, ZnSOD or MnSOD, are oxygen intolerant, and the double mutant was hypermutable and defective in sporulation and exhibited requirements for methionine and lysine. A Cu, ZnSOD-null Drosophila exhibited a shortened lifespan.
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            Nutritional immunity beyond iron: a role for manganese and zinc.

            Vertebrates sequester iron from invading pathogens, and conversely, pathogens express a variety of factors to steal iron from the host. Recent work has demonstrated that in addition to iron, vertebrates sequester zinc and manganese both intracellularly and extracellularly to protect against infection. Intracellularly, vertebrates utilize the ZIP/ZnT families of transporters to manipulate zinc levels, as well as Nramp1 to manipulate manganese levels. Extracellularly, the S100 protein calprotectin sequesters manganese and potentially zinc to inhibit microbial growth. To circumvent these defenses, bacteria possess high affinity transporters to import specific nutrient metals. Limiting the availability of zinc and manganese as a mechanism to defend against infection expands the spectrum of nutritional immunity and further establishes metal sequestration as a key defense against microbial invaders. Copyright 2009 Elsevier Ltd. All rights reserved.
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              Superoxide dismutases: ancient enzymes and new insights.

              Superoxide dismutases (SODs) catalyze the de toxification of superoxide. SODs therefore acquired great importance as O(2) became prevalent following the evolution of oxygenic photosynthesis. Thus the three forms of SOD provide intriguing insights into the evolution of the organisms and organelles that carry them today. Although ancient organisms employed Fe-dependent SODs, oxidation of the environment made Fe less bio-available, and more dangerous. Indeed, modern lineages make greater use of homologous Mn-dependent SODs. Our studies on the Fe-substituted MnSOD of Escherichia coli, as well as redox tuning in the FeSOD of E. coli shed light on how evolution accommodated differences between Fe and Mn that would affect SOD performance, in SOD proteins whose activity is specific to one or other metal ion. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
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                Author and article information

                Journal
                Int J Mol Sci
                Int J Mol Sci
                ijms
                International Journal of Molecular Sciences
                MDPI
                1422-0067
                10 April 2019
                April 2019
                : 20
                : 7
                : 1770
                Affiliations
                [1 ]Department of Clinical Pathology, Cheng Hsin General Hospital, Taipei 11220; Taiwan; jcm5851@ 123456gmail.com (H.-W.J.); ch1835@ 123456chgh.org.tw (H.-F.L.)
                [2 ]Department of Restaurant, Hotel and Institutional Management, 24205, Fu-Jen Catholic University, New Taipei City 24205, Taiwan
                [3 ]Department of Biotechnology and Laboratory Science in Medicine, 11221, National Yang-Ming University, Taipei 11221, Taiwan; r19817037@ 123456yahoo.com.tw (Y.-W.H.); sarapanpan0208@ 123456gmail.com (S.-Y.P.); e8201212002@ 123456gmail.com (I.-L.L.); toe3273917@ 123456outlook.com (H.-H.H.)
                Author notes
                [* ]Correspondence: tcyang@ 123456ym.edu.tw ; Tel.: +886-2-2826-7289
                [†]

                These authors contributed equally to this work.

                Article
                ijms-20-01770
                10.3390/ijms20071770
                6479884
                30974814
                37f4758e-eaff-4085-8437-dc4547487d40
                © 2019 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 27 February 2019
                : 09 April 2019
                Categories
                Article

                Molecular biology
                superoxide dismutase,mnsod,fesod,soda,stenotrophomonas maltophilia,oxidative stress,soxr
                Molecular biology
                superoxide dismutase, mnsod, fesod, soda, stenotrophomonas maltophilia, oxidative stress, soxr

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