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Garcia PS, Gribaldo S, Barras F. When iron and sulfur met on an anoxic planet and eventually made clusters essential for life. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119730. [PMID: 38631441 DOI: 10.1016/j.bbamcr.2024.119730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 03/11/2024] [Accepted: 04/04/2024] [Indexed: 04/19/2024]
Abstract
[FeS] clusters are co-factors that are essential for life and are synthesized by dedicated multiprotein cellular machineries. In this review, we present the current scenario for the emergence and the diversification of the [FeS] cluster biosynthesis machineries. In addition to well-known NIF, ISC and SUF machineries, two alternative minimal systems, SMS, and MIS, were recently identified. Taxonomic distribution and phylogeny analyses indicate that SMS and MIS were present in the Last Universal Common Ancestor (LUCA), well before the increase of oxygen on Earth. ISC, SUF and NIF systems emerged later in the history of life. The possible reasons for the emergence and diversification of these machineries are discussed.
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Affiliation(s)
- Pierre Simon Garcia
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Department of Microbiology, Unit Stress Adaptation and Metabolism in Enterobacteria, Paris, France; Institut Pasteur, Université Paris Cité, Department of Microbiology, Unit Evolutionary Biology of the Microbial Cell, Paris, France
| | - Simonetta Gribaldo
- Institut Pasteur, Université Paris Cité, Department of Microbiology, Unit Evolutionary Biology of the Microbial Cell, Paris, France
| | - Frédéric Barras
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Department of Microbiology, Unit Stress Adaptation and Metabolism in Enterobacteria, Paris, France.
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2
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Abanoz-Seçgin B, Otur Ç, Okay S, Kurt-Kızıldoğan A. The regulatory role of Fur-encoding SCLAV_3199 in iron homeostasis in Streptomyces clavuligerus. Gene 2023:147594. [PMID: 37364696 DOI: 10.1016/j.gene.2023.147594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 06/09/2023] [Accepted: 06/23/2023] [Indexed: 06/28/2023]
Abstract
Iron homeostasis is strictly regulated by complex cascades connected with secondary metabolism in bacteria. Ferric uptake regulators ('Fur's), siderophores, efflux systems, and two-component signal transduction systems are the leading players in response stimuli. However, these regulatory mechanisms remain to be elucidated in Streptomyces clavuligerus. Our study focused on unraveling a possible role of SCLAV_3199 which encodes a Fur family transcriptional regulator, particularly in iron regulation and at the global level in this species. We deleted the SCLAV_3199 gene in S. clavuligerus and compared gene expression differences with the wild-type strain based on iron availability by RNA-seq. We found a potential regulatory effect of SCLAV_3199 on many transcriptional regulators and transporters. Besides, the genes encoding iron sulfur binding proteins were overexpressed in the mutant in the presence of iron. Notably, catechol (SCLAV_5397), and hydroxamate-type (SCLAV_1952, SCLAV_4680) siderophore-related genes were upregulated in the mutant strain in iron scarcity. Concomitantly, S. clavuligerus Δ3199 produced 1.65 and 1.9 times more catechol and hydroxamate-type siderophores, respectively, than that of the wild type strain under iron depletion. Iron containing chemically defined medium did not favor antibiotic production in S. clavuligerus Δ3199 while fermentation in starch-asparagine medium led to improved cephamycin C (2.23-fold) and clavulanic acid (2.56-fold) production in the mutant compared to the control. However, better tunicamycin yield (2.64-fold) was obtained in trypticase soy broth-grown cultures of S. clavuligerus Δ3199. Our findings demonstrate that the SCLAV_3199 gene plays a significant role in regulating both iron homeostasis and secondary metabolite biosynthesis in S. clavuligerus.
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Affiliation(s)
- Büşra Abanoz-Seçgin
- Department of Agricultural Biotechnology, Ondokuz Mayıs University, Samsun 55139, Türkiye
| | - Çiğdem Otur
- Department of Agricultural Biotechnology, Ondokuz Mayıs University, Samsun 55139, Türkiye
| | - Sezer Okay
- Department of Vaccine Technology, Vaccine Institute, Hacettepe University, Ankara, 06230, Türkiye
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Pang Y, Wang J, Gao X, Jiang M, Zhu L, Liang F, Liang M, Wu X, Xu X, Ren X, Xie T, Wang W, Sun Q, Xiong X, Lyu J, Li J, Tan G. Roles of conserved active site residues in the IscS cysteine desulfurase reaction. Front Microbiol 2023; 14:1084205. [PMID: 36876095 PMCID: PMC9978102 DOI: 10.3389/fmicb.2023.1084205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Accepted: 01/31/2023] [Indexed: 02/18/2023] Open
Abstract
Escherichia coli cysteine desulfurase (CD), IscS, modifies basal metabolism by transferring sulphur (S) from L-cysteine to numerous cellular pathways, whereas NFS1, a human CD, is active only in the formation of the [Acp]2:[ISD11]2:[NFS1]2 complex. Despite the accumulation of red-coloured IscS in E. coli cells as a result of the deficiency of accessible iron, as revealed in our previous studies, the mechanism of the potential enzymatic reaction remains unclear. In this study, the N-terminus of IscS was fused with the C-terminus of NFS1, which was reported to be almost fully active as IscS and exhibits a pyridoxal 5'-phosphate (PLP) absorption peak at 395 nm. Moreover, SUMO-EH-IscS exhibited significant growth recovery and NADH-dehydrogenase I activity in the iscS mutant cells. Furthermore, through in vitro and in vivo experiments combined with high-performance liquid chromatography and ultra-performance liquid chromatography-tandem mass spectrometry, it was shown that the new absorption peaks of the IscS H104Q, IscS Q183E, IscS K206A, and IscS K206A&C328S variants at 340 and 350 nm may correspond to the enzyme reaction intermediates, Cys-ketimine and Cys-aldimine, respectively. However, after mutation of the conserved active-site residues, additional absorption peaks at 420 and 430 nm were associated with PLP migration in the active-site pocket. Additionally, the corresponding absorption peaks of Cys-quinonoid, Ala-ketimine, and Ala-aldimine intermediates in IscS were 510, 325, and 345 nm, respectively, as determined by site-directed mutagenesis and substrate/product-binding analyses during the CD reaction process. Notably, red IscS formed in vitro by incubating IscS variants (Q183E and K206A) with excess L-alanine and sulphide under aerobic conditions produced an absorption peak similar to the wild-type IscS, at 510 nm. Interestingly, site-directed mutation of IscS with hydrogen bonds to PLP at Asp180 and Gln183 resulted in a loss of enzymatic activity followed by an absorption peak consistent with NFS1 (420 nm). Furthermore, mutations at Asp180 or Lys206 inhibited the reaction of IscS in vitro with L-cysteine (substrate) and L-alanine (product). These results suggest that the conserved active site residues (His104, Asp180, and Gln183) and their hydrogen bond with PLP in the N-terminus of IscS play a key role in determining whether the L-cysteine substrate can enter the active-site pocket and regulate the enzymatic reaction process. Therefore, our findings provide a framework for evaluating the roles of conserved active-site residues, motifs, and domains in CDs.
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Affiliation(s)
- Yilin Pang
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China.,Hunan Animal Pharmaceutical Company, Hunan Agricultural Group Company, Hunan Agricultural Development & Investment Group Company, Wangcheng Economic and Technological Development Zone, Changsha, Hunan, China
| | - Jing Wang
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xueping Gao
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Mengyao Jiang
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Lifei Zhu
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Feng Liang
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China.,Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Mengxiang Liang
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xiaolin Wu
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xianxian Xu
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xiaojun Ren
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China.,People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Ting Xie
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Wu Wang
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Qianqian Sun
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xiaojun Xiong
- Hunan Animal Pharmaceutical Company, Hunan Agricultural Group Company, Hunan Agricultural Development & Investment Group Company, Wangcheng Economic and Technological Development Zone, Changsha, Hunan, China
| | - Jianxin Lyu
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China.,People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Jianghui Li
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Guoqiang Tan
- Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
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Zaidi SEZ, Zaheer R, Barbieri R, Cook SR, Hannon SJ, Booker CW, Church D, Van Domselaar G, Zovoilis A, McAllister TA. Genomic Characterization of Enterococcus hirae From Beef Cattle Feedlots and Associated Environmental Continuum. Front Microbiol 2022; 13:859990. [PMID: 35832805 PMCID: PMC9271880 DOI: 10.3389/fmicb.2022.859990] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 04/08/2022] [Indexed: 11/13/2022] Open
Abstract
Enterococci are commensal bacteria of the gastrointestinal tract of humans, animals, and insects. They are also found in soil, water, and plant ecosystems. The presence of enterococci in human, animal, and environmental settings makes these bacteria ideal candidates to study antimicrobial resistance in the One-Health continuum. This study focused on Enterococcus hirae isolates (n = 4,601) predominantly isolated from beef production systems including bovine feces (n = 4,117, 89.5%), catch-basin water (n = 306, 66.5%), stockpiled bovine manure (n = 24, 0.5%), and natural water sources near feedlots (n = 145, 32%), and a few isolates from urban wastewater (n = 9, 0.2%) denoted as human-associated environmental samples. Antimicrobial susceptibility profiling of a subset (n = 1,319) of E. hirae isolates originating from beef production systems (n = 1,308) showed high resistance to tetracycline (65%) and erythromycin (57%) with 50.4% isolates harboring multi-drug resistance, whereas urban wastewater isolates (n = 9) were resistant to nitrofurantoin (44.5%) and tigecycline (44.5%) followed by linezolid (33.3%). Genes for tetracycline (tetL, M, S/M, and O/32/O) and macrolide resistance erm(B) were frequently found in beef production isolates. Antimicrobial resistance profiles of E. hirae isolates recovered from different environmental settings appeared to reflect the kind of antimicrobial usage in beef and human sectors. Comparative genomic analysis of E. hirae isolates showed an open pan-genome that consisted of 1,427 core genes, 358 soft core genes, 1701 shell genes, and 7,969 cloud genes. Across species comparative genomic analysis conducted on E. hirae, Enterococcus faecalis and Enterococcus faecium genomes revealed that E. hirae had unique genes associated with vitamin production, cellulose, and pectin degradation, traits which may support its adaptation to the bovine digestive tract. E. faecium and E. faecalis more frequently harbored virulence genes associated with biofilm formation, iron transport, and cell adhesion, suggesting niche specificity within these species.
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Affiliation(s)
- Sani-e-Zehra Zaidi
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada
- University of Lethbridge, Lethbridge, AB, Canada
| | - Rahat Zaheer
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada
| | - Ruth Barbieri
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada
| | - Shaun R. Cook
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada
| | | | | | - Deirdre Church
- Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Calgary Laboratory Services, Calgary, AB, Canada
| | - Gary Van Domselaar
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada
| | | | - Tim A. McAllister
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada
- *Correspondence: Tim A. McAllister,
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Abstract
Iron limitation is a universal strategy of host immunity during bacterial infection. However, the mechanisms by which pathogens antagonize host nutritional immunity have not been fully elucidated. Here, we identified a requirement for the UMPylator YdiU for this process in Salmonella. The expression of YdiU was dramatically induced by the metal starvation signal. The intracellular iron content was much lower in the ΔydiU strain than in wild-type Salmonella, and the ΔydiU strain exhibited severe growth defect under metal deficiency environments. Genome-wide expression analyses revealed significantly decreased expression of iron uptake genes in ΔydiU strain compared with the wild-type strain. Interestingly, YdiU did not affect the expression level of the major iron uptake regulator Fur but directly UMPylated Fur on its H118 residue in vivo and in vitro. UMPylation destroyed the Fur dimer, promoted Fur aggregation, and eliminated the DNA-binding activity of Fur, thus abolishing the ability of Fur to inhibit iron uptake. Restricting Fur to the deUMPylated state dramatically eliminates Salmonella iron uptake in iron deficiency environments. In parallel, YdiU facilitates Salmonella survival within host cells by regulating the iron uptake pathway.
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6
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Fontenot CR, Tasnim H, Valdes KA, Popescu CV, Ding H. Ferric uptake regulator (Fur) reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis in Escherichia coli. J Biol Chem 2020; 295:15454-15463. [PMID: 32928958 DOI: 10.1074/jbc.ra120.014814] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 09/04/2020] [Indexed: 12/19/2022] Open
Abstract
The ferric uptake regulator (Fur) is a global transcription factor that regulates intracellular iron homeostasis in bacteria. The current hypothesis states that when the intracellular "free" iron concentration is elevated, Fur binds ferrous iron, and the iron-bound Fur represses the genes encoding for iron uptake systems and stimulates the genes encoding for iron storage proteins. However, the "iron-bound" Fur has never been isolated from any bacteria. Here we report that the Escherichia coli Fur has a bright red color when expressed in E. coli mutant cells containing an elevated intracellular free iron content because of deletion of the iron-sulfur cluster assembly proteins IscA and SufA. The acid-labile iron and sulfide content analyses in conjunction with the EPR and Mössbauer spectroscopy measurements and the site-directed mutagenesis studies show that the red Fur protein binds a [2Fe-2S] cluster via conserved cysteine residues. The occupancy of the [2Fe-2S] cluster in Fur protein is ∼31% in the E. coli iscA/sufA mutant cells and is decreased to ∼4% in WT E. coli cells. Depletion of the intracellular free iron content using the membrane-permeable iron chelator 2,2´-dipyridyl effectively removes the [2Fe-2S] cluster from Fur in E. coli cells, suggesting that Fur senses the intracellular free iron content via reversible binding of a [2Fe-2S] cluster. The binding of the [2Fe-2S] cluster in Fur appears to be highly conserved, because the Fur homolog from Hemophilus influenzae expressed in E. coli cells also reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis.
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Affiliation(s)
- Chelsey R Fontenot
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Homyra Tasnim
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Kathryn A Valdes
- Department of Chemistry, University of St. Thomas, St. Paul, Minnesota, USA
| | - Codrina V Popescu
- Department of Chemistry, University of St. Thomas, St. Paul, Minnesota, USA
| | - Huangen Ding
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA.
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Li J, Han Q, Zhang T, Du J, Sun Q, Pang Y. Expression of soluble native protein in Escherichia coli using a cold-shock SUMO tag-fused expression vector. ACTA ACUST UNITED AC 2018; 19:e00261. [PMID: 30009138 PMCID: PMC6042314 DOI: 10.1016/j.btre.2018.e00261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 05/27/2018] [Accepted: 05/28/2018] [Indexed: 02/01/2023]
Abstract
Construction of a simple and efficient cloning vector namely, pWMU-19T based on seamless cloning method. The novel pCold-SUMOa vector is suitable for expression of soluble native heterologous proteins. The pCold-SUMOa expression vector can dramatically enhance the stability and activity of target proteins.
At present, approximately 30% of eukaryotic proteins can be expressed in a soluble form in Escherichia coli. In this study, a pCold-SUMOa plasmid was constructed in order to express heterologous proteins fused with SUMO by a cold-shock expression vector. The human cysteine desulfurase NFS1 and a chimeric cysteine desulfurase namely, EH-IscS were successfully expressed in E. coli. The proteins were particularly difficult to be produced functionally, due to their readily sequestered nature. The recombinant cysteine desulfurases that were generated by pCold-SUMOa exhibited higher activity, solubility and stability compared with the well-known plasmid pCold I. In contrast to the pCold TF plasmid, the SUMO tag conferred no biological activity with regard to the conformation of the cysteine desulfurases. Furthermore, the SUMO protease 1 can efficiently recognize the tertiary structure of SUMO and cleave it. The data indicate that the pCold-SUMOa vector is a promising tool for native eukaryotic protein production.
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Affiliation(s)
- Jianghui Li
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, Institute of Enzyme Engineering and Medical Diagnosis, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Qinxia Han
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, Institute of Enzyme Engineering and Medical Diagnosis, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Tao Zhang
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, Institute of Enzyme Engineering and Medical Diagnosis, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Jing Du
- People's Hospital of Hangzhou Medical College, Hangzhou 310014, China
| | - Qianqian Sun
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, Institute of Enzyme Engineering and Medical Diagnosis, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou 325035, China
| | - Yilin Pang
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, Institute of Enzyme Engineering and Medical Diagnosis, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou 325035, China
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Ghosh S, Dureja C, Khatri I, Subramanian S, Raychaudhuri S, Ghosh S. Identification of novel small RNAs in Burkholderia cenocepacia KC-01 expressed under iron limitation and oxidative stress conditions. MICROBIOLOGY-SGM 2017; 163:1924-1936. [PMID: 29099689 DOI: 10.1099/mic.0.000566] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Small RNA (sRNA)-mediated regulation of gene expression is a major tool to understand bacterial responses to environmental changes. In particular, pathogenic bacteria employ sRNAs to adapt to the host environment and establish infection. Members of the Burkholderia cepacia complex, normally present in soil microbiota, cause nosocomial lung infection especially in hospitalized cystic fibrosis patients. We sequenced the draft genome of Burkholderia cenocepacia KC-01, isolated from the coastal saline soil, and identified several potential sRNAs in silico. Expression of seven small RNAs (Bc_KC_sr1-7) was subsequently confirmed. Two sRNAs (Bc_KC_sr1 and Bc_KC_sr2) were upregulated in response to iron depletion by 2,2'-bipyridyl and another two (Bc_KC_sr3 and Bc_KC_sr4) responded to the presence of 60 µM H2O2 in the culture media. Bc_Kc_sr5, 6 and 7 remained unchanged under these conditions. Expression of Bc_KC_sr2, 3 and 4 also altered with a change in temperature and incubation time. A search in the Rfam and BSRD databases identified Bc_Kc_sr4 as candidate738 in B. pseudomallei D286 and assigned Bc_Kc_sr5 and 6 as tmRNA and 6S RNA, respectively. The novel sRNAs were conserved in Burkholderiaceae but did not have any homologue in other genera. Bc_KC_sr1 and 4 were transcribed independently while the rest were part of the 3' UTR of their upstream genes. TargetRNA2 predicted that these sRNAs could target a host of cellular messages with very high stringency. Intriguingly, regions surrounding the translation initiation site for several enzymes involved in Fe-S cluster and siderophore biosynthesis, ROS homeostasis, porins, transcription and translation regulators, were among the suggested putative binding sites for these sRNAs.
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Affiliation(s)
- Suparna Ghosh
- Department of Microbiology, University of Calcutta, Kolkata 700 019, India
| | - Chetna Dureja
- CSIR-Institute of Microbial Technology, Chandigarh 160 036, India
| | - Indu Khatri
- CSIR-Institute of Microbial Technology, Chandigarh 160 036, India
| | | | | | - Sagarmoy Ghosh
- Department of Microbiology, University of Calcutta, Kolkata 700 019, India
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Anaerobic Copper Toxicity and Iron-Sulfur Cluster Biogenesis in Escherichia coli. Appl Environ Microbiol 2017; 83:AEM.00867-17. [PMID: 28576762 DOI: 10.1128/aem.00867-17] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 05/31/2017] [Indexed: 12/31/2022] Open
Abstract
While copper is an essential trace element in biology, pollution of groundwater from copper has become a threat to all living organisms. Cellular mechanisms underlying copper toxicity, however, are still not fully understood. Previous studies have shown that iron-sulfur proteins are among the primary targets of copper toxicity in Escherichia coli under aerobic conditions. Here, we report that, under anaerobic conditions, iron-sulfur proteins in E. coli cells are even more susceptible to copper in medium. Whereas addition of 0.2 mM copper(II) chloride to LB (Luria-Bertani) medium has very little or no effect on iron-sulfur proteins in wild-type E. coli cells under aerobic conditions, the same copper treatment largely inactivates iron-sulfur proteins by blocking iron-sulfur cluster biogenesis in the cells under anaerobic conditions. Importantly, proteins that do not have iron-sulfur clusters (e.g., fumarase C and cysteine desulfurase) in E. coli cells are not significantly affected by copper treatment under aerobic or anaerobic conditions, indicating that copper may specifically target iron-sulfur proteins in cells. Additional studies revealed that E. coli cells accumulate more intracellular copper under anaerobic conditions than under aerobic conditions and that the elevated copper content binds to the iron-sulfur cluster assembly proteins IscU and IscA, which effectively inhibits iron-sulfur cluster biogenesis. The results suggest that the copper-mediated inhibition of iron-sulfur proteins does not require oxygen and that iron-sulfur cluster biogenesis is the primary target of anaerobic copper toxicity in cells.IMPORTANCE Copper contamination in groundwater has become a threat to all living organisms. However, cellular mechanisms underlying copper toxicity have not been fully understood up to now. The work described here reveals that iron-sulfur proteins in Escherichia coli cells are much more susceptible to copper in medium under anaerobic conditions than they are under aerobic conditions. Under anaerobic conditions, E. coli cells accumulate excess intracellular copper, which specifically targets iron-sulfur proteins by blocking iron-sulfur cluster biogenesis. Since iron-sulfur proteins are involved in diverse and vital physiological processes, inhibition of iron-sulfur cluster biogenesis by copper disrupts multiple cellular functions and ultimately inhibits cell growth. The results from this study illustrate a new interplay between intracellular copper toxicity and iron-sulfur cluster biogenesis in bacterial cells under anaerobic conditions.
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