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Redox Cycling Dioxonaphthoimidazoliums Disrupt Iron Homeostasis in Mycobacterium bovis Bacillus Calmette-Guérin. Microbiol Spectr 2022; 10:e0197022. [PMID: 36377959 PMCID: PMC9769636 DOI: 10.1128/spectrum.01970-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The dioxonaphthoimidazolium scaffold is a novel, highly bactericidal redox cycling antituberculosis chemotype that is reliant on the respiratory enzyme Type II NADH dehydrogenase (NDH2) for the generation of reactive oxygen species (ROS). Here, we employed Mycobacterium bovis Bacillus Calmette-Guérin (M. bovis BCG) reporter strains to show that ROS generated by the redox cycler SA23 simulated an iron deficient state in the bacteria, which led to a compensatory increase in the expression of the iron acquisition mbtB gene while collaterally reducing the expression of the iron storage bfrB gene. Exacerbating the iron deficiency via the inclusion of an iron chelator or aggravating oxidative stress by deploying a catalase (KatG) loss-of-function mutant strain enhanced the activity of SA23, whereas a combined approach of treating the katG mutant strain with an iron chelator led to even greater gains in activity. Our results support the notion that the activity of SA23 pivots on a vicious cycle of events that involve the derailment of iron homeostasis toward greater acquisition of the metal, overwhelmed oxidative stress defenses due to enhanced Fenton reactivity, and, ultimately, self-inflicted death. Hence, we posit that redox cyclers that concurrently perturb the iron equilibrium and cellular respiration are well-positioned to be potent next-generation anti-tubercular drugs. IMPORTANCE Cellular respiration in mycobacteria is a potentially rich target space for the discovery of novel drug entities. Here, we show that a redox cycling bactericidal small molecule that selectively activates a respiratory complex in mycobacteria has the surprising effect of disrupting iron homeostasis. Our results support the notion that the disruption of cellular respiration is a potent driver of reactive oxygen species (ROS) generation by the redox cycling molecule. Mycobacteria respond by acquiring iron to restore the levels depleted by the prevailing oxidizing conditions, which inadvertently trigger the compensatory acquisition of the metal. This leads to overwhelmed oxidative stress defenses and yet more iron depletion. For organisms that are unable to break out of this pernicious cycle of events, cell death is the inevitable outcome. Hence, aberrant ROS production by a redox cycling bactericidal agent inflicts a plethora of damaging effects on mycobacteria, including the derailment of iron homeostasis.
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2
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Nair RR, Sharan D, Srinivasan V, Mukkayyan N, Jakkala K, Ajitkumar P. The H2O2 inherently released by the mycobacterial minor subpopulation enhances the survival of the major kin subpopulation against rifampicin. CURRENT RESEARCH IN MICROBIAL SCIENCES 2022; 3:100148. [PMID: 35909613 PMCID: PMC9325904 DOI: 10.1016/j.crmicr.2022.100148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 06/04/2022] [Accepted: 06/15/2022] [Indexed: 11/30/2022] Open
Abstract
Stress survival of mycobacterial minor (SCs) and major (NCs) subpopulations. The SCs enhance survival of the NCs against rifampicin. H2O2 released by the SCs increased KatG levels in the NCs. Increased KatG levels neutralised the H2O2 formed during rifampicin exposure. The enhanced survival was not observed in the furA-katG/katG knockout mutants.
Exposure to antibiotics most often generates oxidative stress in bacteria. Oxidative stress survival mechanisms would facilitate the evolution of antibiotic resistance. As part of an effort to understand oxidative stress survival mechanisms in mycobacteria, here we show that the minor subpopulation (SCs; short-sized cells constituting 10% of the population) of Mycobacterium smegmatis significantly increased the survival of its major kin subpopulation (NCs; normal/long-sized cells constituting 90% of the population) in the mid-log-phase (MLP) cultures against the oxidative stress induced by rifampicin and exogenously added H2O2 (positive control). We had earlier shown that the SCs in the MLP cultures inherently and naturally release significantly high levels of H2O2 into the medium. Addition of the SCs’ culture supernatant, unlike the supernatant of the dimethylthiourea (H2O2 scavenger) exposed SCs, enhanced the survival of NCs. It indicated that NCs’ survival required the H2O2 present in the SCs’ supernatant. This H2O2 transcriptionally induced high levels of catalase-peroxidase (KatG) in the NCs. The naturally high KatG levels in the NCs significantly neutralised the endogenous H2O2 formed upon exposure to rifampicin or H2O2, thereby enhancing the survival of NCs against oxidative stress. The absence of such enhanced survival in the furA-katG and katG knockout (KO) mutants of NCs in the presence of wild-type SCs, confirmed the requirement of the H2O2 present in the SCs’ supernatant and NCs’ KatG for enhanced oxidative stress survival. The presence of SCs:NCs at 1:9 in the pulmonary tuberculosis patients’ sputum alludes to the clinical significance of the finding.
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Affiliation(s)
- Rashmi Ravindran Nair
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, Karnataka, India
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Deepti Sharan
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, Karnataka, India
- Department of Microbiology, University of Chicago, Chicago, IL 60637, USA
| | - Vijay Srinivasan
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, Karnataka, India
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Nagaraja Mukkayyan
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, Karnataka, India
- Department of Microbial Pathogenesis, University of Maryland, Baltimore 21201, Maryland, USA
| | - Kishor Jakkala
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, Karnataka, India
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Parthasarathi Ajitkumar
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, Karnataka, India
- Corresponding author.
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Shimizu T, Onuki M, Suzuki S, Hirai S, Yokoyama E, Matsumoto A, Hamabata T. Enhanced production of Shiga toxin 1 in enterohaemorrhagic Escherichia coli by oxygen. MICROBIOLOGY (READING, ENGLAND) 2021; 167. [PMID: 34951398 DOI: 10.1099/mic.0.001122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Enterohaemorrhagic Escherichia coli (EHEC) produces Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2). Although stx1 and stx2 were found within the late operons of the Stx-encoding phages (Stx-phages), stx1 could mainly be transcribed from the stx1 promoter (P Stx1), which represents the functional operator-binding site (Fur box) for the transcriptional regulator Fur (ferric uptake regulator), upstream of stx1. In this study, we found that the production of Stx1 by EHEC was affected by oxygen concentration. Increased Stx1 production in the presence of oxygen is dependent on Fur, which is an Fe2+-responsive transcription factor. The intracellular Fe2+ pool was lower under microaerobic conditions than under anaerobic conditions, suggesting that lower Fe2+ availability drove the formation of less Fe2+-Fur, less DNA binding to the P Stx1 region, and an increase in Stx1 production.
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Affiliation(s)
- Takeshi Shimizu
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8670, Japan
| | - Manami Onuki
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8670, Japan
| | - Shin Suzuki
- Departments of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8670, Japan
| | - Shinichiro Hirai
- Department of Infectious Disease Risk Management Center, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi-murayama, Tokyo 208-0011, Japan
| | - Eiji Yokoyama
- Division of Bacteriology, Chiba Prefectural Institute of Public Health, 666-2 Nitona, Chuo-ku, Chiba, 260-8715, Japan
| | - Akio Matsumoto
- Department of Aging Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-Nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Takashi Hamabata
- Department of Infectious Disease, Research Institute, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo, 162-8655, Japan
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4
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Fridianto KT, Li M, Hards K, Negatu DA, Cook GM, Dick T, Lam Y, Go ML. Functionalized Dioxonaphthoimidazoliums: A Redox Cycling Chemotype with Potent Bactericidal Activities against Mycobacterium tuberculosis. J Med Chem 2021; 64:15991-16007. [PMID: 34706190 DOI: 10.1021/acs.jmedchem.1c01383] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Disruption of redox homeostasis in mycobacteria causes irreversible stress induction and cell death. Here, we report the dioxonaphthoimidazolium scaffold as a novel redox cycling antituberculosis chemotype with potent bactericidal activity against growing and nutrient-starved phenotypically drug-resistant nongrowing bacteria. Maximal potency was dependent on the activation of the redox cycling quinone by the positively charged scaffold and accessibility to the mycobacterial cell membrane as directed by the lipophilicity and conformational characteristics of the N-substituted side chains. Evidence from microbiological, biochemical, and genetic investigations implicates a redox-driven mode of action that is reliant on the reduction of the quinone by type II NADH dehydrogenase (NDH2) for the generation of bactericidal levels of the reactive oxygen species (ROS). The bactericidal profile of a potent water-soluble analogue 32 revealed good activity against nutrient-starved organisms in the Loebel model of dormancy, low spontaneous resistance mutation frequency, and synergy with isoniazid in the checkerboard assay.
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Affiliation(s)
| | | | - Kiel Hards
- Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand
| | - Dereje A Negatu
- Center for Discovery and Innovation, Hackensack Meridian Health & Department of Medical Sciences, Hackensack Meridian School of Medicine, Nutley, New Jersey 07110, United States
| | - Gregory M Cook
- Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand
| | - Thomas Dick
- Center for Discovery and Innovation, Hackensack Meridian Health & Department of Medical Sciences, Hackensack Meridian School of Medicine, Nutley, New Jersey 07110, United States.,Department of Microbiology and Immunology, Georgetown University, Washington, District of Columbia 20057, United States
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5
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Dow A, Sule P, O’Donnell TJ, Burger A, Mattila JT, Antonio B, Vergara K, Marcantonio E, Adams LG, James N, Williams PG, Cirillo JD, Prisic S. Zinc limitation triggers anticipatory adaptations in Mycobacterium tuberculosis. PLoS Pathog 2021; 17:e1009570. [PMID: 33989345 PMCID: PMC8121289 DOI: 10.1371/journal.ppat.1009570] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 04/19/2021] [Indexed: 01/06/2023] Open
Abstract
Mycobacterium tuberculosis (Mtb) has complex and dynamic interactions with the human host, and subpopulations of Mtb that emerge during infection can influence disease outcomes. This study implicates zinc ion (Zn2+) availability as a likely driver of bacterial phenotypic heterogeneity in vivo. Zn2+ sequestration is part of "nutritional immunity", where the immune system limits micronutrients to control pathogen growth, but this defense mechanism seems to be ineffective in controlling Mtb infection. Nonetheless, Zn2+-limitation is an environmental cue sensed by Mtb, as calprotectin triggers the zinc uptake regulator (Zur) regulon response in vitro and co-localizes with Zn2+-limited Mtb in vivo. Prolonged Zn2+ limitation leads to numerous physiological changes in vitro, including differential expression of certain antigens, alterations in lipid metabolism and distinct cell surface morphology. Furthermore, Mtb enduring limited Zn2+ employ defensive measures to fight oxidative stress, by increasing expression of proteins involved in DNA repair and antioxidant activity, including well described virulence factors KatG and AhpC, along with altered utilization of redox cofactors. Here, we propose a model in which prolonged Zn2+ limitation defines a population of Mtb with anticipatory adaptations against impending immune attack, based on the evidence that Zn2+-limited Mtb are more resistant to oxidative stress and exhibit increased survival and induce more severe pulmonary granulomas in mice. Considering that extracellular Mtb may transit through the Zn2+-limited caseum before infecting naïve immune cells or upon host-to-host transmission, the resulting phenotypic heterogeneity driven by varied Zn2+ availability likely plays a key role during early interactions with host cells.
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Affiliation(s)
- Allexa Dow
- School of Life Sciences, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
| | - Preeti Sule
- Microbial Pathogenesis and Immunology, Texas A&M University Health, Bryan, Texas, United States of America
| | - Timothy J. O’Donnell
- Department of Chemistry, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
| | - Andrew Burger
- School of Ocean and Earth Science and Technology, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
| | - Joshua T. Mattila
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Brandi Antonio
- School of Life Sciences, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
| | - Kevin Vergara
- School of Life Sciences, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
| | - Endrei Marcantonio
- School of Life Sciences, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
| | - L. Garry Adams
- Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas, United States of America
| | - Nicholas James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, Honolulu, Hawaii, United States of America
| | - Philip G. Williams
- Department of Chemistry, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
| | - Jeffrey D. Cirillo
- Microbial Pathogenesis and Immunology, Texas A&M University Health, Bryan, Texas, United States of America
| | - Sladjana Prisic
- School of Life Sciences, University of Hawaiʻi at Mānoa, Honolulu, Hawaii, United States of America
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Ethanol in Combination with Oxidative Stress Significantly Impacts Mycobacterial Physiology. J Bacteriol 2020; 202:JB.00222-20. [PMID: 32928928 DOI: 10.1128/jb.00222-20] [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: 04/24/2020] [Accepted: 09/02/2020] [Indexed: 11/20/2022] Open
Abstract
Here, we investigate the mycobacterial response to the combined stress of an organic oxidant (cumene hydroperoxide [CHP]) and a solvent (ethanol). To understand the interaction between the two stressors, we treated Mycobacterium smegmatis cells to a range of ethanol concentrations (2.5% to 10% [vol/vol]) in combination with a subinhibitory concentration of 1 mM CHP. It was observed that the presence of CHP increases the efficacy of ethanol in inducing rapid cell death. The data further suggest that ethanol reacts with the alkoxy radicals to produce ethanol-derived peroxides. These radicals induce significant membrane damage and lead to cell lysis. The ethanol-derived radicals were primarily recognized by the cells as organic radicals, as was evident by the differential upregulation of the ohr-ohrR genes that function in cells treated with the combination of ethanol and CHP. The role of organic peroxide reductase, Ohr, was further confirmed by the significantly higher sensitivity of the deletion mutant to CHP and the combined stress treatment of CHP and ethanol. Moreover, we also observed the sigma factor σB to be important for the cells treated with ethanol alone as well as the aforementioned combination. A ΔsigB mutant strain had significantly higher susceptibility to the stress conditions. This finding was correlated with the σB-dependent transcriptional regulation of ohr and ohrR In summary, our data indicate that the combination of low levels of ethanol and organic peroxides induce ethanol-derived organic radicals that lead to significant oxidative stress on the cells in a concentration-dependent manner.IMPORTANCE Bacterial response to a combination of stresses can be unexpected and very different compared with that of an individual stress treatment. This study explores the physiological and transcriptional response of mycobacteria in response to the combinatorial treatment of an oxidant with the commonly used solvent ethanol. The presence of a subinhibitory concentration of organic peroxide increases the effectiveness of ethanol by inducing reactive peroxides that destroy the membrane integrity of cells in a significantly short time span. Our work elucidates a mechanism of targeting the complex mycobacterial membrane, which is its primary source of intrinsic resistance. Furthermore, it also demonstrates the importance of exploring the effect of various stress conditions on inducing bacterial clearance.
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7
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Gao CH, Wei WP, Tao HL, Cai LK, Jia WZ, Hu L, Yang M. Cross-talk between the three furA orthologs in Mycobacterium smegmatis and the contribution to isoniazid resistance. J Biochem 2019; 166:237-243. [PMID: 30993320 DOI: 10.1093/jb/mvz030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 04/10/2019] [Indexed: 01/18/2023] Open
Abstract
The ferric uptake regulator A (FurA) plays an essential role in responding to oxidative stress in mycobacteria. The genome of Mycobacterium smegmatis harbours three FurA orthologs; however, the potential cross-talk and contribution to drug resistance of different furA operon remain underdetermined. In this study, we characterized the cross-regulation and effect in drug resistance of these orthologs from M. smegmatis. Cross-binding of FurA protein to furA promoter was observed. The binding of FurA1 to furA3p and FurA2 to furA1p or furA3p is even more pronounced than their self-binding. The three FurA proteins are all functional at repressing the expression of the peroxidase enzyme katG1/katG2 in vivo. When overexpressing any of the furA orthologs in M. smegmatis, the bacteria become more resistant to isoniazid (INH). This pattern is consistent with that in Mycobacterium bovis. However, the knockdown of furA does not affect the INH sensitivity. This is the first report of cross-talk and contribution to drug resistance of all three furA orthologs in M. smegmatis.
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Affiliation(s)
- Chun-Hui Gao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, No. 1, Shizishan Street, Hongshan District, Wuhan, China
| | - Wen-Ping Wei
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, No. 1, Shizishan Street, Hongshan District, Wuhan, China
| | - Hui-Ling Tao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, No. 1, Shizishan Street, Hongshan District, Wuhan, China
| | - Li-Kai Cai
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, No. 1, Shizishan Street, Hongshan District, Wuhan, China
| | - Wan-Zhong Jia
- The State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, No. 1, Xujiaping, Chengguan District, Chinese Academy of Agricultural Sciences, Lanzhou, China
| | - Lihua Hu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, No. 1, Shizishan Street, Hongshan District, Wuhan, China
| | - Min Yang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, No. 1, Shizishan Street, Hongshan District, Wuhan, China
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8
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Chatterjee R, Shreenivas MM, Sunil R, Chakravortty D. Enteropathogens: Tuning Their Gene Expression for Hassle-Free Survival. Front Microbiol 2019; 9:3303. [PMID: 30687282 PMCID: PMC6338047 DOI: 10.3389/fmicb.2018.03303] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/19/2018] [Indexed: 12/27/2022] Open
Abstract
Enteropathogenic bacteria have been the cause of the majority of foodborne illnesses. Much of the research has been focused on elucidating the mechanisms by which these pathogens evade the host immune system. One of the ways in which they achieve the successful establishment of a niche in the gut microenvironment and survive is by a chain of elegantly regulated gene expression patterns. Studies have shown that this process is very elaborate and is also regulated by several factors. Pathogens like, enteropathogenic Escherichia coli (EPEC), Salmonella Typhimurium, Shigellaflexneri, Yersinia sp. have been seen to employ various regulated gene expression strategies. These include toxin-antitoxin systems, quorum sensing systems, expression controlled by nucleoid-associated proteins (NAPs), several regulons and operons specific to these pathogens. In the following review, we have tried to discuss the common gene regulatory systems of enteropathogenic bacteria as well as pathogen-specific regulatory mechanisms.
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Affiliation(s)
- Ritika Chatterjee
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India.,Division of Biological Sciences, Indian Institute of Science, Bengaluru, India
| | - Meghanashree M Shreenivas
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India.,Division of Biological Sciences, Indian Institute of Science, Bengaluru, India.,Undergraduate Studies, Indian Institute of Science, Bengaluru, India
| | - Rohith Sunil
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India.,Division of Biological Sciences, Indian Institute of Science, Bengaluru, India.,Undergraduate Studies, Indian Institute of Science, Bengaluru, India
| | - Dipshikha Chakravortty
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India.,Division of Biological Sciences, Indian Institute of Science, Bengaluru, India.,Centre for Biosystems Science and Engineering, Indian Institute of Science, Bengaluru, India
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9
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Essential Nucleoid Associated Protein mIHF (Rv1388) Controls Virulence and Housekeeping Genes in Mycobacterium tuberculosis. Sci Rep 2018; 8:14214. [PMID: 30242166 PMCID: PMC6155035 DOI: 10.1038/s41598-018-32340-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 07/20/2018] [Indexed: 12/14/2022] Open
Abstract
Tight control of gene expression is crucial for Mycobacterium tuberculosis to adapt to the changing environments encountered when infecting or exiting human cells. While three nucleoid associated proteins (NAPs) EspR, HupB and Lsr2 have been investigated, the role of a fourth, the mycobacterial integration host factor (mIHF), remains elusive. Here, we report a multidisciplinary functional analysis that exploits a conditional mIHF mutant. Gene silencing was bactericidal and resulted in elongated cells devoid of septa, with only one nucleoid. ChIP-sequencing identified 153 broad peaks distributed around the chromosome, which were often situated upstream of transcriptional start sites where EspR also bound. RNA-sequencing showed expression of 209 genes to be heavily affected upon mIHF depletion, including those for many tRNAs, DNA synthesis and virulence pathways. Consistent with NAP function, mIHF acts as a global regulator by directly and indirectly controlling genes required for pathogenesis and for housekeeping functions.
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10
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Lee HN, Ji CJ, Lee HH, Park J, Seo YS, Lee JW, Oh JI. Roles of three FurA paralogs in the regulation of genes pertaining to peroxide defense in Mycobacterium smegmatis mc 2 155. Mol Microbiol 2018; 108:661-682. [PMID: 29569300 DOI: 10.1111/mmi.13956] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/18/2018] [Indexed: 11/28/2022]
Abstract
Mycobacterium smegmatis mc2 155 has three genes (MSMEG_6383, furA1; MSMEG_3460, furA2; MSMEG_6253, furA3) encoding FurA (ferric-uptake regulator A) paralogs. Three FurA paralogs in M. smegmatis are functionally redundant and negatively regulate expression of a subset of genes involved in peroxide detoxification such as ahpC, katG1 and katG2, as well as their own genes. The FurA paralogs sense H2 O2 via metal-catalyzed His oxidation (MCHO) in the same way as PerR. The propensity of FurA2 and FurA3 for MCHO is greater than that of FurA1. The three furA genes are transcribed into leaderless mRNAs lacking the Shine-Dalgarno (SD) sequence. FurA1 and FurA3 have the quaternary structure of homodimers like most Fur homologs, whereas FurA2 occurs as a monomer. The monomeric structure of FurA2 is determined by the C-terminal region of its dimerization domain. FurA2 monomers appear to cooperatively bind to the FurA-binding site with an inverted repeat configuration and have a broader binding specificity for the target DNA than dimeric FurA1 and FurA3. Comparative transcriptomic analysis revealed that the FurA paralogs do not regulate genes related to iron homeostasis in M. smegmatis, and that expression of SigF-regulated genes is significantly decreased in a furA triple mutant relative to the wild-type strain of M. smegmatis.
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Affiliation(s)
- Ha-Na Lee
- Department of Microbiology, Pusan National University, Busan, 46241, Korea
| | - Chang-Jun Ji
- Department of Life Science and Research Institute for Natural Sciences, Hanyang University, Seoul, 04763, Korea
| | - Hyun-Hee Lee
- Department of Microbiology, Pusan National University, Busan, 46241, Korea
| | - Jungwook Park
- Department of Microbiology, Pusan National University, Busan, 46241, Korea
| | - Young-Su Seo
- Department of Microbiology, Pusan National University, Busan, 46241, Korea
| | - Jin-Won Lee
- Department of Life Science and Research Institute for Natural Sciences, Hanyang University, Seoul, 04763, Korea
| | - Jeong-Il Oh
- Department of Microbiology, Pusan National University, Busan, 46241, Korea
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11
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Oliveira TL, Rizzi C, Dellagostin OA. Recombinant BCG vaccines: molecular features and their influence in the expression of foreign genes. Appl Microbiol Biotechnol 2017; 101:6865-6877. [PMID: 28779291 DOI: 10.1007/s00253-017-8439-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 07/13/2017] [Accepted: 07/15/2017] [Indexed: 01/17/2023]
Abstract
Recombinant Mycobacterium bovis BCG vaccines (rBCG) were first developed in the 1990s as a means of expressing antigens from multiple pathogens. This review examines the key structural factors of recombinant M. bovis that influence the expression of the heterologous antigens and the generation of genetic and functional stability in rBCG, which are crucial for inducing strong and lasting immune responses. The fundamental aim of this paper is to provide an overview of factors that affect the expression of recombinant proteins in BCG and the generation of the immune response against the target antigens, including mycobacterial promoters, location of foreign antigens, and stability of the vectors. The reporter systems that have been employed for evaluation of these molecular features in BCG are also reviewed here.
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Affiliation(s)
- Thaís Larré Oliveira
- Programa de Pós-Graduação em Biotecnologia, Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, RS, Brazil
| | - Caroline Rizzi
- Programa de Pós-Graduação em Biotecnologia, Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, RS, Brazil
| | - Odir Antônio Dellagostin
- Programa de Pós-Graduação em Biotecnologia, Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, RS, Brazil. .,Unidade de Biotecnologia, Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Campus Universitário, Caixa Postal 354, Pelotas, RS, CEP 96010-900, Brazil.
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12
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Namouchi A, Gómez-Muñoz M, Frye SA, Moen LV, Rognes T, Tønjum T, Balasingham SV. The Mycobacterium tuberculosis transcriptional landscape under genotoxic stress. BMC Genomics 2016; 17:791. [PMID: 27724857 PMCID: PMC5057432 DOI: 10.1186/s12864-016-3132-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 09/27/2016] [Indexed: 11/10/2022] Open
Abstract
Background As an intracellular human pathogen, Mycobacterium tuberculosis (Mtb) is facing multiple stressful stimuli inside the macrophage and the granuloma. Understanding Mtb responses to stress is essential to identify new virulence factors and pathways that play a role in the survival of the tubercle bacillus. The main goal of this study was to map the regulatory networks of differentially expressed (DE) transcripts in Mtb upon various forms of genotoxic stress. We exposed Mtb cells to oxidative (H2O2 or paraquat), nitrosative (DETA/NO), or alkylation (MNNG) stress or mitomycin C, inducing double-strand breaks in the DNA. Total RNA was isolated from treated and untreated cells and subjected to high-throughput deep sequencing. The data generated was analysed to identify DE genes encoding mRNAs, non-coding RNAs (ncRNAs), and the genes potentially targeted by ncRNAs. Results The most significant transcriptomic alteration with more than 700 DE genes was seen under nitrosative stress. In addition to genes that belong to the replication, recombination and repair (3R) group, mainly found under mitomycin C stress, we identified DE genes important for bacterial virulence and survival, such as genes of the type VII secretion system (T7SS) and the proline-glutamic acid/proline-proline-glutamic acid (PE/PPE) family. By predicting the structures of hypothetical proteins (HPs) encoded by DE genes, we found that some of these HPs might be involved in mycobacterial genome maintenance. We also applied a state-of-the-art method to predict potential target genes of the identified ncRNAs and found that some of these could regulate several genes that might be directly involved in the response to genotoxic stress. Conclusions Our study reflects the complexity of the response of Mtb in handling genotoxic stress. In addition to genes involved in genome maintenance, other potential key players, such as the members of the T7SS and PE/PPE gene family, were identified. This plethora of responses is detected not only at the level of DE genes encoding mRNAs but also at the level of ncRNAs and their potential targets. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3132-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Amine Namouchi
- Department of Microbiology, Oslo University Hospital, Postboks 4950, NO-0424, Oslo, Norway
| | | | - Stephan A Frye
- Department of Microbiology, Oslo University Hospital, Postboks 4950, NO-0424, Oslo, Norway
| | - Line Victoria Moen
- Department of Informatics, University of Oslo, Oslo, Norway.,Current address: Department of Nutrition, University of Oslo, Oslo, Norway
| | - Torbjørn Rognes
- Department of Microbiology, Oslo University Hospital, Postboks 4950, NO-0424, Oslo, Norway.,Department of Informatics, University of Oslo, Oslo, Norway
| | - Tone Tønjum
- Department of Microbiology, Oslo University Hospital, Postboks 4950, NO-0424, Oslo, Norway.,Department of Microbiology, University of Oslo, Oslo, Norway
| | - Seetha V Balasingham
- Department of Microbiology, Oslo University Hospital, Postboks 4950, NO-0424, Oslo, Norway.
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13
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Hu Y, Wang Z, Feng L, Chen Z, Mao C, Zhu Y, Chen S. σ(E) -dependent activation of RbpA controls transcription of the furA-katG operon in response to oxidative stress in mycobacteria. Mol Microbiol 2016; 102:107-20. [PMID: 27353316 DOI: 10.1111/mmi.13449] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/22/2016] [Indexed: 01/08/2023]
Abstract
Mycobacterium tuberculosis adopts various strategies to cope with oxidative stress during infection. Transcriptional regulators, including σ factors, make important contributions to this stress response, but how these proteins cooperate with each other is largely unknown. In this study, the role of RbpA and its cooperation with σ factors in response to oxidative stress are investigated. Knock down expression of rbpA in Mycobacterium smegmatis attenuated bacterial survival in the presence of H2 O2 . Additionally, transcription of the rbpA gene was induced by H2 O2 in a σ(E) -dependent manner. After induction, RbpA interacts with the principal sigma factor, σ(A) , to control the transcription of furA-katG operon, which encodes an H2 O2 scavenging enzyme. Moreover, this regulation is responsible for the role of σ(E) in oxidative response because bacterial survival was attenuated and transcription of the furA-katG operon was down-regulated with H2 O2 treatment in sigE deletion mutant (ΔsigE), and over-expression of RbpA in ΔsigE strain restored all of these phenotypes. Taken together, our study first illustrated a mechanism for σ(E) in response to oxidative stress through regulation of rbpA transcription. This study was also the first to demonstrate that RbpA is required for the full response to oxidative stress by cooperating with the principal σ(A) .
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Affiliation(s)
- Yangbo Hu
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Zhongwei Wang
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.,University of Chinese Academy of Sciences, Beijing, 10086, China
| | - Lipeng Feng
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.,University of Chinese Academy of Sciences, Beijing, 10086, China
| | - Zhenkang Chen
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.,University of Chinese Academy of Sciences, Beijing, 10086, China
| | - Chunyou Mao
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.,University of Chinese Academy of Sciences, Beijing, 10086, China
| | - Yan Zhu
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.,University of Chinese Academy of Sciences, Beijing, 10086, China
| | - Shiyun Chen
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
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14
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Patel SJ, Lewis BE, Long JE, Nambi S, Sassetti CM, Stemmler TL, Argüello JM. Fine-tuning of Substrate Affinity Leads to Alternative Roles of Mycobacterium tuberculosis Fe2+-ATPases. J Biol Chem 2016; 291:11529-39. [PMID: 27022029 DOI: 10.1074/jbc.m116.718239] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Indexed: 11/06/2022] Open
Abstract
Little is known about iron efflux transporters within bacterial systems. Recently, the participation of Bacillus subtilis PfeT, a P1B4-ATPase, in cytoplasmic Fe(2+) efflux has been proposed. We report here the distinct roles of mycobacterial P1B4-ATPases in the homeostasis of Co(2+) and Fe(2+) Mutation of Mycobacterium smegmatis ctpJ affects the homeostasis of both ions. Alternatively, an M. tuberculosis ctpJ mutant is more sensitive to Co(2+) than Fe(2+), whereas mutation of the homologous M. tuberculosis ctpD leads to Fe(2+) sensitivity but no alterations in Co(2+) homeostasis. In vitro, the three enzymes are activated by both Fe(2+) and Co(2+) and bind 1 eq of either ion at their transport site. However, equilibrium binding affinities and activity kinetics show that M. tuberculosis CtpD has higher affinity for Fe(2+) and twice the Fe(2+)-stimulated activity than the CtpJs. These parameters are paralleled by a lower activation and affinity for Co(2+) Analysis of Fe(2+) and Co(2+) binding to CtpD by x-ray absorption spectroscopy shows that both ions are five- to six-coordinate, constrained within oxygen/nitrogen environments with similar geometries. Mutagenesis studies suggest the involvement of invariant Ser, His, and Glu residues in metal coordination. Interestingly, replacement of the conserved Cys at the metal binding pocket leads to a large reduction in Fe(2+) but not Co(2+) binding affinity. We propose that CtpJ ATPases participate in the control of steady state Fe(2+) levels. CtpD, required for M. tuberculosis virulence, is a high affinity Fe(2+) transporter involved in the rapid response to iron dyshomeostasis generated upon redox stress.
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Affiliation(s)
- Sarju J Patel
- From the Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
| | - Brianne E Lewis
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201
| | - Jarukit E Long
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts 01655, and
| | - Subhalaxmi Nambi
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts 01655, and
| | - Christopher M Sassetti
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts 01655, and Howard Hughes Medical Institute, Chevy Chase, Maryland 20815
| | - Timothy L Stemmler
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201
| | - José M Argüello
- From the Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts 01609,
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15
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Sikri K, Kumari P, Tyagi JS, Nandi M, Taneja NK, Batra SD. The pleiotropic transcriptional response of Mycobacterium tuberculosis to vitamin C is robust and overlaps with the bacterial response to multiple intracellular stresses. Microbiology (Reading) 2015; 161:739-53. [DOI: 10.1099/mic.0.000049] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 01/28/2015] [Indexed: 11/18/2022] Open
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16
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Lee HN, Lee NO, Han SJ, Ko IJ, Oh JI. Regulation of the ahpC gene encoding alkyl hydroperoxide reductase in Mycobacterium smegmatis. PLoS One 2014; 9:e111680. [PMID: 25365321 PMCID: PMC4218801 DOI: 10.1371/journal.pone.0111680] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 09/29/2014] [Indexed: 12/04/2022] Open
Abstract
The ahpC (MSMEG_4891) gene encodes alkyl hydroperoxide reductase C in Mycobacterium smegmatis mc2155 and its expression is induced under oxidative stress conditions. Two well-defined inverted repeat sequences (IR1 and IR2) were identified in the upstream region of ahpC. Using a crp (cAMP receptor protein: MSMEG_6189) mutant and in vitro DNA-binding assay, it was demonstrated that the IR1 sequence serves as a Crp-binding site and that Crp functions as an activator in the regulation of ahpC expression. The expression level of ahpC was shown to be proportional to intracellular cAMP levels. Intracellular levels of cAMP were increased in M. smegmatis, when it was treated with oxidative stress inducers. The IR2 sequence is very similar to the known consensus sequence of FurA-binding sites and involved in the negative regulation of ahpC expression. Taken together, these results suggest that the induction of ahpC expression under oxidative stress conditions probably results from a combinatory effect of both inactivation of FurA by oxidative stress and activation of Crp in response to increased levels of cAMP.
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Affiliation(s)
- Ha-Na Lee
- Department of Microbiology, Pusan National University, Busan, Korea
| | - Na-On Lee
- Department of Microbiology, Pusan National University, Busan, Korea
| | - Seung J. Han
- Department of Microbiology and Institute for Immunology and Immunological Diseases, Yonsei University, Seoul, Korea
| | - In-Jeong Ko
- Korea Science Academy of KAIST, Busan, Korea
| | - Jeong-Il Oh
- Department of Microbiology, Pusan National University, Busan, Korea
- * E-mail:
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17
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Rodriguez GM, Neyrolles O. Metallobiology of Tuberculosis. Microbiol Spectr 2014; 2:10.1128/microbiolspec.MGM2-0012-2013. [PMID: 26103977 PMCID: PMC5180607 DOI: 10.1128/microbiolspec.mgm2-0012-2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Indexed: 11/20/2022] Open
Abstract
Transition metals are essential constituents of all living organisms, playing crucial structural and catalytic parts in many enzymes and transcription factors. However, transition metals can also be toxic when present in excess. Their uptake and efflux rates must therefore be carefully controlled by biological systems. In this chapter, we summarize the current knowledge about uptake and efflux systems in Mycobacterium tuberculosis for mainly three of these metals, namely iron, zinc, and copper. We also propose questions for future research in the field of metallobiology of host-pathogen interactions in tuberculosis.
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Affiliation(s)
- G. Marcela Rodriguez
- Public Health Research Institute Center & Department of Medicine, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103
| | - Olivier Neyrolles
- Centre National de la Recherche Scientifique & Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France
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18
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Newton-Foot M, Gey van Pittius NC. The complex architecture of mycobacterial promoters. Tuberculosis (Edinb) 2012; 93:60-74. [PMID: 23017770 DOI: 10.1016/j.tube.2012.08.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 07/31/2012] [Accepted: 08/06/2012] [Indexed: 01/02/2023]
Abstract
The genus Mycobacterium includes a variety of species with differing phenotypic properties, including growth rate, pathogenicity and environment- and host-specificity. Although many mycobacterial species have been extensively studied and their genomes sequenced, the reasons for phenotypic variation between closely related species remain unclear. Variation in gene expression may contribute to these characteristics and enable the bacteria to respond to changing environmental conditions. Gene expression is controlled primarily at the level of transcription, where the main element of regulation is the promoter. Transcriptional regulation and associated promoter sequences have been studied extensively in E. coli. This review describes the complex structure and characteristics of mycobacterial promoters, in comparison to the classical E. coli prokaryotic promoter structure. Some components of mycobacterial promoters are similar to those of E. coli. These include the predominant guanine residue at the transcriptional start point, conserved -10 hexamer, similar interhexameric distances, the use of ATG as a start codon, the guanine- and adenine-rich ribosome binding site and the presence of extended -10 (TGn) motifs in strong promoters. However, these components are much more variable in sequence in mycobacterial promoters and no conserved -35 hexamer sequence (clearly defined in E. coli) can be identified. This may be a result of the high G+C content of mycobacterial genomes, as well as the large number of sigma factors present in mycobacteria, which may recognise different promoter sequences. Mycobacteria possess a complex transcriptional regulatory network. Numerous regulatory motifs have been identified in mycobacterial promoters, predominantly in the interhexameric region. These are bound by specific transcriptional regulators in response to environmental changes. The combination of specific promoter sequences, transcriptional regulators and a variety of sigma factors enables rapid and specific responses to diverse conditions and different stages of infection. This review aims to provide an overview of the complex architecture of mycobacterial transcriptional regulation.
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Affiliation(s)
- Mae Newton-Foot
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Stellenbosch University, PO Box 19063, Francie van Zijl Drive, Tygerberg 7505, South Africa.
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19
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Midha M, Prasad NK, Vindal V. MycoRRdb: a database of computationally identified regulatory regions within intergenic sequences in mycobacterial genomes. PLoS One 2012; 7:e36094. [PMID: 22563442 PMCID: PMC3338573 DOI: 10.1371/journal.pone.0036094] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 03/29/2012] [Indexed: 11/18/2022] Open
Abstract
The identification of regulatory regions for a gene is an important step towards deciphering the gene regulation. Regulatory regions tend to be conserved under evolution that facilitates the application of comparative genomics to identify such regions. The present study is an attempt to make use of this attribute to identify regulatory regions in the Mycobacterium species followed by the development of a database, MycoRRdb. It consist the regulatory regions identified within the intergenic distances of 25 mycobacterial species. MycoRRdb allows to retrieve the identified intergenic regulatory elements in the mycobacterial genomes. In addition to the predicted motifs, it also allows user to retrieve the Reciprocal Best BLAST Hits across the mycobacterial genomes. It is a useful resource to understand the transcriptional regulatory mechanism of mycobacterial species. This database is first of its kind which specifically addresses cis-regulatory regions and also comprehensive to the mycobacterial species. Database URL: http://mycorrdb.uohbif.in.
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Affiliation(s)
- Mohit Midha
- Department of Biotechnology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Nirmal K. Prasad
- Department of Biotechnology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Vaibhav Vindal
- Department of Biotechnology, School of Life Sciences, University of Hyderabad, Hyderabad, India
- * E-mail:
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20
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McGuire AM, Weiner B, Park ST, Wapinski I, Raman S, Dolganov G, Peterson M, Riley R, Zucker J, Abeel T, White J, Sisk P, Stolte C, Koehrsen M, Yamamoto RT, Iacobelli-Martinez M, Kidd MJ, Maer AM, Schoolnik GK, Regev A, Galagan J. Comparative analysis of Mycobacterium and related Actinomycetes yields insight into the evolution of Mycobacterium tuberculosis pathogenesis. BMC Genomics 2012; 13:120. [PMID: 22452820 PMCID: PMC3388012 DOI: 10.1186/1471-2164-13-120] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 03/28/2012] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND The sequence of the pathogen Mycobacterium tuberculosis (Mtb) strain H37Rv has been available for over a decade, but the biology of the pathogen remains poorly understood. Genome sequences from other Mtb strains and closely related bacteria present an opportunity to apply the power of comparative genomics to understand the evolution of Mtb pathogenesis. We conducted a comparative analysis using 31 genomes from the Tuberculosis Database (TBDB.org), including 8 strains of Mtb and M. bovis, 11 additional Mycobacteria, 4 Corynebacteria, 2 Streptomyces, Rhodococcus jostii RHA1, Nocardia farcinia, Acidothermus cellulolyticus, Rhodobacter sphaeroides, Propionibacterium acnes, and Bifidobacterium longum. RESULTS Our results highlight the functional importance of lipid metabolism and its regulation, and reveal variation between the evolutionary profiles of genes implicated in saturated and unsaturated fatty acid metabolism. It also suggests that DNA repair and molybdopterin cofactors are important in pathogenic Mycobacteria. By analyzing sequence conservation and gene expression data, we identify nearly 400 conserved noncoding regions. These include 37 predicted promoter regulatory motifs, of which 14 correspond to previously validated motifs, as well as 50 potential noncoding RNAs, of which we experimentally confirm the expression of four. CONCLUSIONS Our analysis of protein evolution highlights gene families that are associated with the adaptation of environmental Mycobacteria to obligate pathogenesis. These families include fatty acid metabolism, DNA repair, and molybdopterin biosynthesis. Our analysis reinforces recent findings suggesting that small noncoding RNAs are more common in Mycobacteria than previously expected. Our data provide a foundation for understanding the genome and biology of Mtb in a comparative context, and are available online and through TBDB.org.
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21
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Li Y, He ZG. The mycobacterial LysR-type regulator OxyS responds to oxidative stress and negatively regulates expression of the catalase-peroxidase gene. PLoS One 2012; 7:e30186. [PMID: 22272299 PMCID: PMC3260234 DOI: 10.1371/journal.pone.0030186] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 12/15/2011] [Indexed: 11/18/2022] Open
Abstract
Protection against oxidative stress is one of the primary defense mechanisms contributing to the survival of Mycobacterium tuberculosis in the host. In this study, we provide evidence that OxyS, a LysR-type transcriptional regulator functions as an oxidative stress response regulator in mycobacteria. Overexpression of OxyS lowers expression of the catalase-peroxidase (KatG) gene in M. smegmatis. OxyS binds directly with the katG promoter region and a conserved, GC-rich T-N(11)-A motif for OxyS binding was successfully characterized in the core binding site. Interestingly, the DNA-binding activity of OxyS was inhibited by H(2)O(2), but not by dithiothreitol. Cys25, which is situated at the DNA-binding domain of OxyS, was found to have a regulatory role for the DNA-binding ability of OxyS in response to oxidative stress. In contrast, the other three cysteine residues in OxyS do not appear to have this function. Furthermore, the mycobacterial strain over-expressing OxyS had a higher sensitivity to H(2)O(2). Thus, OxyS responds to oxidative stress through a unique cysteine residue situated in its DNA-binding domain and negatively regulates expression of the katG gene. These findings uncover a specific regulatory mechanism for mycobacterial adaptation to oxidative stress.
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Affiliation(s)
- Yuqing Li
- National Key Laboratory of Agricultural Microbiology, Center for Proteomics Research, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Zheng-Guo He
- National Key Laboratory of Agricultural Microbiology, Center for Proteomics Research, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- * E-mail:
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22
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Taverniti V, Forti F, Ghisotti D, Putzer H. Mycobacterium smegmatis RNase J is a 5'-3' exo-/endoribonuclease and both RNase J and RNase E are involved in ribosomal RNA maturation. Mol Microbiol 2011; 82:1260-76. [PMID: 22014150 DOI: 10.1111/j.1365-2958.2011.07888.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The presence of very different sets of enzymes, and in particular the presence of RNase E and RNase J, has been used to explain significant differences in RNA metabolism between the two model organisms Escherichia coli and Bacillus subtilis. However, these studies might have somewhat polarized our view of RNA metabolism. Here, we identified a RNase J in Mycobacterium smegmatis that has both 5'-3' exo- and endonucleolytic activity. This enzyme coexists with RNase E in this organism, a configuration that enabled us to study how these two key nucleases collaborate. We demonstrate that RNase E is responsible for the processing of the furA-katG transcript in M. smegmatis and that both RNase E and RNase J are involved in the 5' end processing of all ribosomal RNAs. In contrast to B. subtilis, the activity of RNase J, although required in vivo for 23S rRNA maturation, is not essential in M. smegmatis. We show that the pathways for ribosomal RNA maturation in M. smegmatis are quite different from those observed in E. coli and in B. subtilis. Studying organisms containing different combinations of key ribonucleases can thus significantly broaden our view of the possible strategies that exist to direct RNA metabolism.
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Affiliation(s)
- Valerio Taverniti
- Department of Biomolecular Sciences and Biotechnology, University of Milano, Via Celoria 26, 20133 Milano, Italy
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MdoR is a novel positive transcriptional regulator for the oxidation of methanol in Mycobacterium sp. strain JC1. J Bacteriol 2011; 193:6288-94. [PMID: 21908665 DOI: 10.1128/jb.05649-11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium sp. strain JC1 is able to grow on methanol as a sole source of carbon and energy using methanol:N,N'-dimethyl-4-nitrosoaniline oxidoreductase (MDO) as a key enzyme for methanol oxidation. The second open reading frame (mdoR) upstream of, and running divergently from, the mdo gene was identified as a gene for a TetR family transcriptional regulator. The N-terminal region of MdoR contained a helix-turn-helix DNA-binding motif. An electrophoretic mobility shift assay (EMSA) indicated that MdoR could bind to a mdo promoter region containing an inverted repeat. The mdoR deletion mutant did not grow on methanol, but growth on methanol was restored by a plasmid containing an intact mdoR gene. In DNase I footprinting and EMSA experiments, MdoR bound to two inverted repeats in the putative mdoR promoter region. Reverse transcription-PCR indicated that the mdoR gene was transcribed only in cells growing on methanol, whereas β-galactosidase assays showed that the mdoR promoter was activated in the presence of methanol. These results indicate that MdoR serves as a transcriptional activator for the expression of mdo and its own gene. Also, MdoR is the first discovered member of the TetR family of transcriptional regulators to be involved in the regulation of the methanol oxidation, as well as to function as a positive autoregulator.
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Forti F, Mauri V, Dehò G, Ghisotti D. Isolation of conditional expression mutants in Mycobacterium tuberculosis by transposon mutagenesis. Tuberculosis (Edinb) 2011; 91:569-78. [PMID: 21840262 DOI: 10.1016/j.tube.2011.07.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 06/28/2011] [Accepted: 07/17/2011] [Indexed: 12/22/2022]
Abstract
In Mycobacterium tuberculosis identification of essential genes has been hampered by the scarcity of suitable genetic tools for genome wide screenings. We constructed two Himar1 transposon derivatives in which the Streptomyces pristinamycin I-inducible ptr promoter was inserted at one transposon end in outward orientation. These transposons, Tn-pip/pptr (which harbours the promoter and its repressor pip gene) and Tn-pptr (which depends on a host expressing the pip gene), were inserted in the thermosensitive mycobacteriophage phAE87. After transduction into M. tuberculosis H37Rv, hygromycin resistant clones were selected in the presence of pristinamycin, screened for inducer dependent growth, and the transposon insertion point mapped by sequencing. Out of 3530 Hyg(R) mutants tested, we obtained 14 (0.4%) single insertion conditional mutants. In three (leuA, mazE6, rne) pptr was located upstream of genes whose function had been assessed by experimental evidence, whereas in seven the transposon targeted genes (ftsK, glf, infB, metC, pyrD, secY, and tuf) whose function had been assigned by similarity with homologous genes and four ORFs of unknown function (Rv0883c, Rv1478, Rv2050 and Rv2204c). These results validate our mutagenesis system and provide previously unavailable conditional expression mutants in genes of known, putative and unknown functions for genetic and physiological studies.
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Affiliation(s)
- Francesca Forti
- Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
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25
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Banerjee S, Farhana A, Ehtesham NZ, Hasnain SE. Iron acquisition, assimilation and regulation in mycobacteria. INFECTION GENETICS AND EVOLUTION 2011; 11:825-38. [PMID: 21414421 DOI: 10.1016/j.meegid.2011.02.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 02/25/2011] [Accepted: 02/28/2011] [Indexed: 11/28/2022]
Abstract
Iron is as crucial to the pathogen as it is to the host. The tuberculosis causing bacillus, Mycobacterium tuberculosis (M.tb), is an exceptionally efficient pathogen that has evolved proficient mechanisms to sequester iron from the host despite its thick mycolate-rich outer covering and a highly impermeable membrane of phagolysosome within which it persists inside an infected host macrophage. Further, both overindulgence and moderation of iron inside a host are a threat to mycobacterial persistence. While for removing iron from the host reservoirs, mycobacteria synthesize molecules that have several times higher affinity for iron than their host counterparts, they also synthesize molecules for efficient storage of excess iron. This is supported by tightly regulated iron dependent global gene expressions. In this review we discuss the various molecules and pathways evolved by mycobacteria for an efficient iron metabolism. We also discuss the less investigated players, like iron responsive proteins and iron responsive elements in mycobacteria, and highlight the lacunae in our current understanding of iron acquisition and utilization in mycobacteria with an ultimate aim to make iron metabolism as a possible anti-mycobacterial target.
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Affiliation(s)
- Sharmistha Banerjee
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
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Ando H, Kitao T, Miyoshi-Akiyama T, Kato S, Mori T, Kirikae T. Downregulation of katG expression is associated with isoniazid resistance in Mycobacterium tuberculosis. Mol Microbiol 2011; 79:1615-28. [DOI: 10.1111/j.1365-2958.2011.07547.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Repression of antibiotic production and sporulation in Streptomyces coelicolor by overexpression of a TetR family transcriptional regulator. Appl Environ Microbiol 2010; 76:7741-53. [PMID: 20935121 DOI: 10.1128/aem.00819-10] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The overexpression of a regulatory gene of the TetR family (SCO3201) originating either from Streptomyces lividans or from Streptomyces coelicolor was shown to strongly repress antibiotic production (calcium-dependent antibiotic [CDA], undecylprodigiosin [RED], and actinorhodin [ACT]) of S. coelicolor and of the ppk mutant strain of S. lividans. Curiously, the overexpression of this gene also had a strong inhibitory effect on the sporulation process of S. coelicolor but not on that of S. lividans. SCO3201 was shown to negatively regulate its own transcription, and its DNA binding motif was found to overlap its -35 promoter sequence. The interruption of this gene in S. lividans or S. coelicolor did not lead to any obvious phenotypes, indicating that when overexpressed SCO3201 likely controls the expression of target genes of other TetR regulators involved in the regulation of the metabolic and morphological differentiation process in S. coelicolor. The direct and functional interaction of SCO3201 with the promoter region of scbA, a gene under the positive control of the TetR-like regulator, ScbR, was indeed demonstrated by in vitro as well as in vivo approaches.
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Sklar JG, Makinoshima H, Schneider JS, Glickman MS. M. tuberculosis intramembrane protease Rip1 controls transcription through three anti-sigma factor substrates. Mol Microbiol 2010; 77:605-17. [PMID: 20545848 DOI: 10.1111/j.1365-2958.2010.07232.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Regulated intramembrane proteolysis (RIP) is a mechanism of transmembrane signal transduction that functions through intramembrane proteolysis of substrates. We previously reported that the RIP metalloprotease Rv2869c (Rip1) is a determinant of Mycobacterium tuberculosis (Mtb) cell envelope composition and virulence, but the substrates of Rip1 were undefined. Here we show that Rip1 cleaves three transmembrane anti-sigma factors: anti-SigK, anti-SigL and anti-SigM, negative regulators of Sigma K, L and M. We show that transcriptional activation of katG in response to phenanthroline requires activation of SigK and SigL by Rip1 cleavage of anti-SigK and anti-SigL. We also demonstrate a Rip1-dependent pathway that activates the genes for the mycolic acid biosynthetic enzyme KasA and the resuscitation promoting factor RpfC, but represses the bacterioferritin encoding gene bfrB. Regulation of these three genes by Rip1 is not reproduced by deletion of Sigma K, L or M, either indicating a requirement for multiple Rip1 substrates or additional arms of the Rip1 pathway. These results identify a branched proteolytic signal transduction system in which a single intramembrane protease cleaves three anti-sigma factor substrates to control multiple downstream pathways involved in lipid biosynthesis and defence against oxidative stress.
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Affiliation(s)
- Joseph G Sklar
- Immunology Program, Sloan-Kettering Institute, New York, NY 10021, USA
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Mycobacterium tuberculosis transcriptional adaptation, growth arrest and dormancy phenotype development is triggered by vitamin C. PLoS One 2010; 5:e10860. [PMID: 20523728 PMCID: PMC2877710 DOI: 10.1371/journal.pone.0010860] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 04/30/2010] [Indexed: 12/03/2022] Open
Abstract
Background Tubercle bacilli are thought to persist in a dormant state during latent tuberculosis (TB) infection. Although little is known about the host factors that induce and maintain Mycobacterium tuberculosis (M. tb) within latent lesions, O2 depletion, nutrient limitation and acidification are some of the stresses implicated in bacterial dormancy development/growth arrest. Adaptation to hypoxia and exposure to NO/CO is implemented through the DevRS/DosT two-component system which induces the dormancy regulon. Methodology/Principal Findings Here we show that vitamin C (ascorbic acid/AA) can serve as an additional signal to induce the DevR regulon. Physiological levels of AA scavenge O2 and rapidly induce the DevR regulon at an estimated O2 saturation of <30%. The kinetics and magnitude of the response suggests an initial involvement of DosT and a sustained DevS-mediated response during bacterial adaptation to increasing hypoxia. In addition to inducing DevR regulon mechanisms, vitamin C induces the expression of selected genes previously shown to be responsive to low pH and oxidative stress, triggers bacterial growth arrest and promotes dormancy phenotype development in M. tb grown in axenic culture and intracellularly in THP-1 cells. Conclusions/Significance Vitamin C mimics multiple intracellular stresses and has wide-ranging regulatory effects on gene expression and physiology of M. tb which leads to growth arrest and a ‘dormant’ drug-tolerant phenotype, but in a manner independent of the DevRS/DosT sytem. The ‘AA-dormancy infection model’ offers a potential alternative to other models of non-replicating persistence of M. tb and may be useful for investigating host-‘dormant’ M. tb interactions. Our findings offer a new perspective on the role of nutritional factors in TB and suggest a possible role for vitamin C in TB.
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Boldrin F, Casonato S, Dainese E, Sala C, Dhar N, Palù G, Riccardi G, Cole ST, Manganelli R. Development of a repressible mycobacterial promoter system based on two transcriptional repressors. Nucleic Acids Res 2010; 38:e134. [PMID: 20406773 PMCID: PMC2896539 DOI: 10.1093/nar/gkq235] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Tightly regulated gene expression systems represent invaluable tools for studying gene function and for the validation of drug targets in bacteria. While several regulated bacterial promoters have been characterized, few of them have been successfully used in mycobacteria. In this article we describe the development of a novel repressible promoter system effective in both fast- and slow-growing mycobacteria based on two chromosomally encoded repressors, dependent on tetracycline (TetR) and pristinamycin (Pip), respectively. This uniqueness results in high versatility and stringency. Using this method we were able to obtain an ftsZ conditional mutant in Mycobacterium smegmatis and a fadD32 conditional mutant in Mycobacterium tuberculosis, confirming their essentiality for bacterial growth in vitro. This repressible promoter system could also be exploited to regulate gene expression during M. tuberculosis intracellular growth.
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Affiliation(s)
- Francesca Boldrin
- Department of Histology, Microbiology and Medical Biotechnologies, University of Padova, Via Gabelli, 63 35100 Padova, Italy
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Identification of katG mutations associated with high-level isoniazid resistance in Mycobacterium tuberculosis. Antimicrob Agents Chemother 2010; 54:1793-9. [PMID: 20211896 DOI: 10.1128/aac.01691-09] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Isoniazid (INH) is an effective first-line antituberculosis drug. KatG, a catalase-peroxidase, converts INH to an active form in Mycobacterium tuberculosis, and katG mutations are major causes of INH resistance. In the present study, we sequenced katG of 108 INH-resistant M. tuberculosis clinical isolates. Consequently, 9 novel KatG mutants with a single-amino-acid substitution were found. All of these mutants had significantly lower INH oxidase activities than the wild type, and each mutant showed various levels of activity. Isolates having mutations with relatively low activities showed high-level INH resistance. On the basis of our results and known mutations associated with INH resistance, we developed a new hybridization-based line probe assay for rapid detection of INH-resistant M. tuberculosis isolates.
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Jang HJ, Nde C, Toghrol F, Bentley WE. Microarray analysis of Mycobacterium bovis BCG revealed induction of iron acquisition related genes in response to hydrogen peroxide. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:9465-9472. [PMID: 19924887 DOI: 10.1021/es902255q] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Mycobacterium bovis BCG strain Pasteur 1173P2 responds with adaptive and protective strategies against oxidative stress. Despite advances in our understanding of the responses to oxidative stress in many specific cases, the connectivity between targeted protective genes and the rest of cell metabolism remains obscure. This study was therefore carried out to investigate the genome-wide response of M. bovis BCG to hydrogen peroxide after 10 and 60 min of treatment. ATP measurements were carried out in order to monitor the changes in M. bovis BCG growth over a 1 h period. The furA gene in Mycobacterium bovis, a pleiotropic regulator that couples iron metabolism to the oxidative stress response was involved in the response to hydrogen peroxide stress. There were also increased levels of catalase/ peroxidase (KatG) and the biosynthesis operon of mycobactin. This study revealed significant upregulation of the oxidative response group of M. bovis, amino acid transport and metabolism, defense mechanisms, DNA replication, recombination and repair, and downregulation of cell cycle control, mitosis, and meiosis, lipid transport and metabolism, and cell wall/membrane biogenesis. This study shows that the treatment of M. bovis BCG with hydrogen peroxide induces iron acquisition related genes and oxidative stress response genes within one hour of treatment.
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Affiliation(s)
- Hyeung-Jin Jang
- Department of Biochemistry, College of Oriental Medicine, Kyung Hee University, Seoul 130-701, Republic of Korea
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Lee HI, Yoon JH, Nam JS, Kim YM, Ro YT. Cloning, expression and characterization of the catalase-peroxidase (KatG) gene from a fast-growing Mycobacterium sp. strain JC1 DSM 3803. J Biochem 2009; 147:511-22. [PMID: 19933836 DOI: 10.1093/jb/mvp197] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The gene encoding a catalase-peroxidase (KatG) was cloned from chromosomal DNA of a fast-growing Mycobacterium sp. strain JC1 DSM 3803. The nucleotide sequence of a 5.7 kb EcoRI fragment containing the katG and its flanking regions was determined. The fragment (5,706 bps) contained two complete open reading frames (ORFs) encoding putative ferric uptake regulator A (FurA) and KatG proteins. The cloned gene, katG, had an ORF of 2241 nt, encoding a protein with calculated molecular mass of 81,748 Da. The furA was located in the upstream of the katG with the same transcriptional direction and there was a 38 bp gap space between them. The deduced KatG and FurA protein sequences showed significant homologies to KatG2 and Fur2 of Mycobacterium smegmatis and clustered with other mycobacterial KatG and Fur-like proteins in phylogenetic trees, respectively. The recombinant KatG overproduced in Escherichia coli was nearly indistinguishable from the native JC1 catalase-peroxidase in enzymatic properties and also possessed the resistance to organic solvents, indicating that the cloned katG truly encodes the Mycobacterium sp. JC1 catalase-peroxidase. Difference spectroscopy revealed Mn(II) binding near the haem of the KatG. Transcript analysis of the furA-katG using RT-PCR suggests that the katG is independently transcribed from the furA.
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Affiliation(s)
- Hyun-Il Lee
- Department of Biochemistry, Graduate School of Medicine, Konkuk University, Seoul 134-701, Korea
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Ortiz de Orué Lucana D, Groves MR. The three-component signalling system HbpS-SenS-SenR as an example of a redox sensing pathway in bacteria. Amino Acids 2009; 37:479-86. [PMID: 19259771 DOI: 10.1007/s00726-009-0260-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 01/30/2009] [Indexed: 01/06/2023]
Abstract
The two-component system SenS-SenR and the extracellular HbpS protein of the cellulose degrader Streptomyces reticuli have been shown to act in concert as a novel system which detects redox stress. In vivo and in vitro experiments have led to the hypothesis that HbpS binds and degrades heme, communicating the extracellular presence of heme and oxidative stress to the membrane-embedded sensor histidine kinase SenS via a bound iron. The response regulator SenR would then up-regulate downstream signalling cascades, leading to the appropriate gene expression levels for bacterial survival in an oxidative environment. Sequence analysis has shown that homologs of HbpS and SenS-SenR exist in a number of ecologically and medically relevant bacterial species, suggesting the existence of a previously undescribed bacterial oxidative stress-response pathway common to both Gram-negative and Gram-positive bacteria. The presented report reviews the current knowledge of the function of this novel protein family consisting of an accessory protein and its cognate two-component system, which could be more properly described as a three-component system.
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Forti F, Crosta A, Ghisotti D. Pristinamycin-inducible gene regulation in mycobacteria. J Biotechnol 2009; 140:270-7. [PMID: 19428723 DOI: 10.1016/j.jbiotec.2009.02.001] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 01/26/2009] [Accepted: 02/03/2009] [Indexed: 10/21/2022]
Abstract
In this work the Pip-inducible system, already used in eukaryotes, was tested in mycobacteria. This system is based on the Streptomyces coelicolor Pip repressor, the Streptomyces pristinaespiralis ptr promoter and the inducer pristinamycin I. By cloning in an integrative plasmid the ptr promoter upstream of the lacZ reporter gene and the pip gene under the control of a constitutive mycobacterial promoter, we demonstrated that the ptr promoter activity increased up to 50-fold in Mycobacterium smegmatis and up to 400-fold in Mycobacterium tuberculosis, in dependence on pristinamycin I concentration, and that the promoter was fully repressed in the absence of the inducer. Three mycobacterial genes were cloned under pptr-Pip control, both in sense and antisense direction; both proteins and antisense RNAs could be over-expressed, the antisenses causing a partial reduction of the amount of the targeted proteins. This system was used to obtain two M. tuberculosis conditional mutants in the fadD32 and pknB genes: the mutant strains grew only in the presence of the inducer pristinamycin I. Thus it showed to be an effective inducible system in mycobacteria.
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Affiliation(s)
- Francesca Forti
- Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26 - 20133 Milano, Italy.
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Saha B, Mukherjee S, Dutta D, Das AK. Expression, purification, crystallization and preliminary X-ray diffraction analysis of the transcriptional repressor SirR from Mycobacterium tuberculosis H37Rv. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:154-8. [PMID: 19194009 PMCID: PMC2635875 DOI: 10.1107/s1744309108043534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Accepted: 12/22/2008] [Indexed: 11/10/2022]
Abstract
SirR, a metal-dependent transcriptional repressor from Mycobacterium tuberculosis (Rv2788), was cloned in pQE30 expression vector with an N-terminal His(6) tag for heterologous overexpression in Escherichia coli M15 (pREP4) cells and purified to homogeneity using chromatographic procedures. The purified protein was crystallized using the sitting-drop vapour-diffusion technique. The crystals belonged to the tetragonal space group P4(1)2(1)2/P4(3)2(1)2, with unit-cell parameters a = 105.21, b = 105.21, c = 144.85 A. The X-ray diffraction data were processed to a maximum resolution of 2.5 A. The Matthews coefficient suggests the presence of two (V(M) = 4.01 A(3) Da(-1)) to four (V(M) = 2.0 A(3) Da(-1)) molecules in the asymmetric unit. Calculation of the self-rotation function shows a crystallographic fourfold symmetry axis along the z axis (chi = 90 degrees) and also a twofold symmetry axis around the z axis (chi = 180 degrees).
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Affiliation(s)
- Baisakhee Saha
- Department of Biotechnology, Indian Institute of Technology, Kharagpur 721 302, India
| | - Somnath Mukherjee
- Department of Biotechnology, Indian Institute of Technology, Kharagpur 721 302, India
| | - Debajyoti Dutta
- Department of Biotechnology, Indian Institute of Technology, Kharagpur 721 302, India
| | - Amit Kumar Das
- Department of Biotechnology, Indian Institute of Technology, Kharagpur 721 302, India
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Fan XY, Ma H, Guo J, Li ZM, Cheng ZH, Guo SQ, Zhao GP. A novel differential expression system for gene modulation in Mycobacteria. Plasmid 2008; 61:39-46. [PMID: 18835406 DOI: 10.1016/j.plasmid.2008.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 08/05/2008] [Accepted: 09/10/2008] [Indexed: 11/25/2022]
Abstract
Tuberculosis (TB) remains a major global health problem, and successful genetic manipulation of mycobacteria is crucial for developing new approaches to study the mechanism of pathogenesis of Mycobacterium tuberculosis (M.tb) and to combat TB. In this study, a series of M.tb furA gene operator/promoter (pfurA) mutants were generated aiming at optimization of the promoter activities in mycobacterial strains. Measured by the lacZ gene-fusion reporter system, change of the initial codon GTG to the preferred ATG resulted in a double increase of beta-galactosidase activity, while a 6-bp substitution in the conserved FurA binding AT-rich region upstream of furA gene led to 4-6 folds increase of the activity. It is significant that combination of both mutations showed about 10 folds of beta-galactosidase activity higher than that of the prototype pfurA. Furthermore, all of the furA promoters were expressed continuously in vivo during intracellular growth of Mycobacterium bovis BCG, and were induced early upon infection in macrophages. Employing the series of pfurA-based differential expression vectors, M.tb chimeric antigen Ag856A2 known for its excellent immunogenicity, was shown to be expressed at different levels in the recombinant Mycobacterium smegmatis and BCG strains. These results indicated that this differential expression system is feasible to express any target antigen of interest in a modular fashion for the study of gene regulation in mycobacterial strains, and also for the development of different recombinant BCG vaccine candidates against TB or other infectious diseases, which would be beneficial for elicitation of optimal immune response.
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Affiliation(s)
- Xiao-Yong Fan
- Department of Microbiology, School of Life Sciences, Fudan University, Shanghai, China.
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Riccardi G, Milano A, Pasca MR, Nies DH. Genomic analysis of zinc homeostasis inMycobacterium tuberculosis. FEMS Microbiol Lett 2008; 287:1-7. [DOI: 10.1111/j.1574-6968.2008.01320.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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The Metal-Dependent Regulators FurA and FurB from Mycobacterium Tuberculosis. Int J Mol Sci 2008; 9:1548-1560. [PMID: 19169435 PMCID: PMC2630230 DOI: 10.3390/ijms9081548] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 07/29/2008] [Accepted: 07/30/2008] [Indexed: 11/17/2022] Open
Abstract
The ferric uptake regulators (Fur) form a large family of bacterial metal-activated DNA-binding proteins that control a diverse set of genes at the transcriptional level. Mycobacterium tuberculosis, the causative agent of tuberculosis, expresses two members of the Fur family, designated FurA and FurB. Although both belong to the same family, they share only approximately 25% sequence identity and as a consequence, they differ significantly in some of their key biological functions. FurA appears to be a specialized iron-dependent regulator that controls the katG gene, which encodes for a catalase-peroxidase involved in the response of M. tuberculosis to oxidative stress. KatG is also the key mycobacterial enzyme responsible for the activation of the first-line tuberculosis drug Isoniazid. FurB in contrast requires Zn(2+) rather than Fe(2+), to bind to its target sequence in regulated genes, which include those involved in Zn(2+)-homeostasis. Recent biochemical, crystallographic and spectroscopic data have now shed light on the activation and metal discrimination mechanisms in this protein family.
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Santos CL, Vieira J, Tavares F, Benson DR, Tisa LS, Berry AM, Moradas-Ferreira P, Normand P. On the nature of fur evolution: a phylogenetic approach in Actinobacteria. BMC Evol Biol 2008; 8:185. [PMID: 18578876 PMCID: PMC2464607 DOI: 10.1186/1471-2148-8-185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2007] [Accepted: 06/25/2008] [Indexed: 01/01/2023] Open
Abstract
Background An understanding of the evolution of global transcription regulators is essential for comprehending the complex networks of cellular metabolism that have developed among related organisms. The fur gene encodes one of those regulators – the ferric uptake regulator Fur – widely distributed among bacteria and known to regulate different genes committed to varied metabolic pathways. On the other hand, members of the Actinobacteria comprise an ecologically diverse group of bacteria able to inhabit various natural environments, and for which relatively little is currently understood concerning transcriptional regulation. Results BLAST analyses revealed the presence of more than one fur homologue in most members of the Actinobacteria whose genomes have been fully sequenced. We propose a model to explain the evolutionary history of fur within this well-known bacterial phylum: the postulated scenario includes one duplication event from a primitive regulator, which probably had a broad range of co-factors and DNA-binding sites. This duplication predated the appearance of the last common ancestor of the Actinobacteria, while six other duplications occurred later within specific groups of organisms, particularly in two genera: Frankia and Streptomyces. The resulting paralogues maintained main biochemical properties, but became specialised for regulating specific functions, coordinating different metal ions and binding to unique DNA sequences. The presence of syntenic regions surrounding the different fur orthologues supports the proposed model, as do the evolutionary distances and topology of phylogenetic trees built using both Neighbor-Joining and Maximum-Likelihood methods. Conclusion The proposed fur evolutionary model, which includes one general duplication and two in-genus duplications followed by divergence and specialization, explains the presence and diversity of fur genes within the Actinobacteria. Although a few rare horizontal gene transfer events have been reported, the model is consistent with the view of gene duplication as a main force of microbial genomes evolution. The parallel study of Fur phylogeny across diverse organisms offers a solid base to guide functional studies and allows the comparison between response mechanisms in relation with the surrounding environment. The survey of regulators among related genomes provides a relevant tool for understanding the evolution of one of the first lines of cellular adaptability, control of DNA transcription.
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Affiliation(s)
- Catarina L Santos
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
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Núñez MC, Menéndez MC, Rebollo MJ, García MJ. Transcriptional analysis of Mycobacterium fortuitum cultures upon hydrogen peroxide treatment using the novel standard rrnA-P1. BMC Microbiol 2008; 8:100. [PMID: 18565220 PMCID: PMC2443159 DOI: 10.1186/1471-2180-8-100] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 06/19/2008] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND The ability of an intracellular pathogen to establish infection depends on the capacity of the organism to survive and replicate inside the host. Mycobacterium fortuitum is a bacteria that contains genes involved in the detoxification of the oxygen reactive species such as those produced by the host during the infection. In this work, we investigate the effects of hydrogen peroxide on the transcription and expression of these genes by developing a real time quantitative PCR technique (qRT-PCR) using the ribosomal promoter region (rrnA-P1) as reference product for quantification of the mRNA levels. RESULTS M. fortuitum cultures were treated with different hydrogen peroxide concentrations (0.02 to 20 mM) during several periods of time (30 to 120 minutes). The activity of the enzymes KatGII and SodA, and the transcription of corresponding genes were evaluated. The transcriptional regulator furAII gene was also studied. The ribosomal promoter region rrnA-P1 was validated as referential product under the stress conditions checked by qRT-PCR. Minor changes were observed under the conditions tested except when bacteria were incubated in the presence of 20 mM hydrogen peroxide. Under those conditions, the levels of transcription of the three genes under study increased at 30 minutes of treatment. The viability of the bacteria was not influenced under the conditions tested. CONCLUSION In this work, we have quantified transcriptional responses to stress suggesting that, the opportunistic pathogen M. fortuitum is more resistant and differs in behaviour in the presence of hydrogen peroxide, when compared to the major pathogen Mycobacterium tuberculosis and the saprophyte Mycobacterium smegmatis. Besides, we demonstrate the mycobacterial non-coding region rrnA-P1 to be a suitable reference product in the analysis of qRT-PCR transcriptional data of M. fortuitum.
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Affiliation(s)
- María Carmen Núñez
- Departamento de Medicina Preventiva, Facultad de Medicina, Universidad Autónoma, c/Arzobispo Morcillo, 4, 28029-Madrid, Spain
- Departamento de Biotecnologia del INIA, Carretera de La Coruña, Km 7.5, 28040-Madrid, Spain
| | - María Carmen Menéndez
- Departamento de Medicina Preventiva, Facultad de Medicina, Universidad Autónoma, c/Arzobispo Morcillo, 4, 28029-Madrid, Spain
| | - María José Rebollo
- Departamento de Medicina Preventiva, Facultad de Medicina, Universidad Autónoma, c/Arzobispo Morcillo, 4, 28029-Madrid, Spain
- GlaxoSmithKline R&D, Diseases of the Developing World, Molecular Drug Discovery, C/Severo Ochoa, n° 2, 28760-Tres Cantos, Madrid, Spain
| | - María J García
- Departamento de Medicina Preventiva, Facultad de Medicina, Universidad Autónoma, c/Arzobispo Morcillo, 4, 28029-Madrid, Spain
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Sala C, Forti F, Magnoni F, Ghisotti D. The katG mRNA of Mycobacterium tuberculosis and Mycobacterium smegmatis is processed at its 5' end and is stabilized by both a polypurine sequence and translation initiation. BMC Mol Biol 2008; 9:33. [PMID: 18394163 PMCID: PMC2358910 DOI: 10.1186/1471-2199-9-33] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Accepted: 04/04/2008] [Indexed: 11/30/2022] Open
Abstract
Background In Mycobacterium tuberculosis and in Mycobacterium smegmatis the furA-katG loci, encoding the FurA regulatory protein and the KatG catalase-peroxidase, are highly conserved. In M. tuberculosis furA-katG constitute a single operon, whereas in M. smegmatis a single mRNA covering both genes could not be found. In both species, specific 5' ends have been identified: the first one, located upstream of the furA gene, corresponds to transcription initiation from the furA promoter; the second one is the katG mRNA 5' end, located in the terminal part of furA. Results In this work we demonstrate by in vitro transcription and by RNA polymerase Chromatin immunoprecipitation that no promoter is present in the M. smegmatis region covering the latter 5' end, suggesting that it is produced by specific processing of longer transcripts. Several DNA fragments of M. tuberculosis and M. smegmatis were inserted in a plasmid between the sigA promoter and the lacZ reporter gene, and expression of the reporter gene was measured. A polypurine sequence, located four bp upstream of the katG translation start codon, increased beta-galactosidase activity and stabilized the lacZ transcript. Mutagenesis of this sequence led to destabilization of the mRNA. Analysis of constructs, in which the polypurine sequence of M. smegmatis was followed by an increasing number of katG codons, demonstrated that mRNA stability requires translation of at least 20 amino acids. In order to define the requirements for the 5' processing of the katG transcript, we created several mutations in this region and analyzed the 5' ends of the transcripts: the distance from the polypurine sequence does not seem to influence the processing, neither the sequence around the cutting point. Only mutations which create a double stranded region around the processing site prevented RNA processing. Conclusion This is the first reported case in mycobacteria, in which both a polypurine sequence and translation initiation are shown to contribute to mRNA stability. The furA-katG mRNA is transcribed from the furA promoter and immediately processed; this processing is prevented by a double stranded RNA at the cutting site, suggesting that the endoribonuclease responsible for the cleavage cuts single stranded RNA.
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Affiliation(s)
- Claudia Sala
- Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, 20133, Milano, Italy.
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Study of the role of Mce3R on the transcription of mce genes of Mycobacterium tuberculosis. BMC Microbiol 2008; 8:38. [PMID: 18304349 PMCID: PMC2277422 DOI: 10.1186/1471-2180-8-38] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 02/27/2008] [Indexed: 11/10/2022] Open
Abstract
Background mce3 is one of the four virulence-related mce operons of Mycobacterium tuberculosis. In a previous work we showed that the overexpression of Mce3R in Mycobacterium smegmatis and M. tuberculosis abolishes the expression of lacZ fused to the mce3 promoter, indicating that Mce3R represses mce3 transcription. Results We obtained a knockout mutant strain of M. tuberculosis H37Rv by inserting a hygromycin cassette into the mce3R gene. The mutation results in a significant increase in the expression of mce3 genes either in vitro or in a murine cell macrophages line as it was determined using promoter-lacZ fusions in M. tuberculosis. The abundance of mce1, mce2 and mce4 mRNAs was not affected by this mutation as it was demonstrated by quantitative RT-PCR. The mce3R promoter activity in the presence of Mce3R was significantly reduced compared with that in the absence of the regulator, during the in vitro culture of M. tuberculosis. Conclusion Mce3R repress the transcription of mce3 operon and self regulates its own expression but does not affect the transcription of mce1, mce2 and mce4 operons of M. tuberculosis.
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The global responses of Mycobacterium tuberculosis to physiological levels of copper. J Bacteriol 2008; 190:2939-46. [PMID: 18263720 DOI: 10.1128/jb.01847-07] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Copper (Cu) is a required micronutrient, but it is highly toxic at high concentrations. Therefore, the levels of Cu must be tightly regulated in all living cells. The phagosome of Mycobacterium tuberculosis has been shown to have variable levels of Cu. Previously, we showed that M. tuberculosis contains a copper-sensitive operon, cso, that is induced during early infection in mice. In this study, we showed that ctpV, a gene in the cso operon, is a copper-responsive gene and most likely encodes an efflux pump for Cu. Furthermore, the transcription of key genes in the cso operon is induced by Cu ions and not by other ions, such as Ni and Zn ions. To elucidate copper-responsive genes other than those in the cso operon, we utilized DNA microarrays to profile mycobacterial responses to physiological levels of Cu. A transcriptome analysis identified a novel set of 30 copper-responsive genes in M. tuberculosis, one-half of which were induced only when toxic levels of Cu were added. Interestingly, several transcriptional regulators, including the furA gene, were induced during toxic Cu exposure, indicating that there was a generalized response to oxidative stressors rather than a Cu-specific response. In general, the Cu-induced transcriptome generated should help elucidate the role of the Cu response in maintaining M. tuberculosis survival during infection and could provide novel targets for controlling this virulent pathogen.
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Ojha A, Hatfull GF. The role of iron in Mycobacterium smegmatis biofilm formation: the exochelin siderophore is essential in limiting iron conditions for biofilm formation but not for planktonic growth. Mol Microbiol 2007; 66:468-83. [PMID: 17854402 PMCID: PMC2170428 DOI: 10.1111/j.1365-2958.2007.05935.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Many species of mycobacteria form structured biofilm communities at liquid–air interfaces and on solid surfaces. Full development of Mycobacterium smegmatis biofilms requires addition of supplemental iron above 1 μM ferrous sulphate, although addition of iron is not needed for planktonic growth. Microarray analysis of the M. smegmatis transcriptome shows that iron-responsive genes – especially those involved in siderophore synthesis and iron uptake – are strongly induced during biofilm formation reflecting a response to iron deprivation, even when 2 μM iron is present. The acquisition of iron under these conditions is specifically dependent on the exochelin synthesis and uptake pathways, and the strong defect of an iron–exochelin uptake mutant suggests a regulatory role of iron in the transition to biofilm growth. In contrast, although the expression of mycobactin and iron ABC transport operons is highly upregulated during biofilm formation, mutants in these systems form normal biofilms in low-iron (2 μM) conditions. A close correlation between iron availability and matrix-associated fatty acids implies a possible metabolic role in the late stages of biofilm maturation, in addition to the early regulatory role. M. smegmatis surface motility is similarly dependent on iron availability, requiring both supplemental iron and the exochelin pathway to acquire it.
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Boulette ML, Payne SM. Anaerobic regulation of Shigella flexneri virulence: ArcA regulates Fur and iron acquisition genes. J Bacteriol 2007; 189:6957-67. [PMID: 17660284 PMCID: PMC2045222 DOI: 10.1128/jb.00621-07] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Invasion and plaque formation in epithelial monolayers are routinely used to assess the virulence of Shigella flexneri, a causative agent of dysentery. A modified plaque assay was developed to identify factors contributing to the virulence of S. flexneri under the anaerobic conditions present in the colon. This assay demonstrated the importance of the ferrous iron transport system Feo, as well as the global transcription factors Fur, ArcA, and Fnr, for Shigella plaque formation in anoxic environments. Transcriptional analyses of S. flexneri iron transport genes indicated that anaerobic conditions activated feoABC while repressing genes encoding two other iron transport systems, the ABC transporter Sit and the Iuc/Iut aerobactin siderophore synthesis and transport system. The anaerobic transcription factors ArcA and Fnr activated expression of feoABC, while ArcA repressed iucABCD iutA. Transcription of fur, encoding the iron-responsive transcriptional repressor of bacterial iron acquisition, was also repressed anaerobically in an ArcA-dependent manner.
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Večerek B, Moll I, Bläsi U. Control of Fur synthesis by the non-coding RNA RyhB and iron-responsive decoding. EMBO J 2007; 26:965-75. [PMID: 17268550 PMCID: PMC1852835 DOI: 10.1038/sj.emboj.7601553] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 12/18/2006] [Indexed: 11/08/2022] Open
Abstract
The Fe2+-dependent Fur protein serves as a negative regulator of iron uptake in bacteria. As only metallo-Fur acts as an autogeneous repressor, Fe2+scarcity would direct fur expression when continued supply is not obviously required. We show that in Escherichia coli post-transcriptional regulatory mechanisms ensure that Fur synthesis remains steady in iron limitation. Our studies revealed that fur translation is coupled to that of an upstream open reading frame (uof), translation of which is downregulated by the non-coding RNA (ncRNA) RyhB. As RyhB transcription is negatively controlled by metallo-Fur, iron depletion creates a negative feedback loop. RyhB-mediated regulation of uof-fur provides the first example for indirect translational regulation by a trans-encoded ncRNA. In addition, we present evidence for an iron-responsive decoding mechanism of the uof-fur entity. It could serve as a backup mechanism of the RyhB circuitry, and represents the first link between iron availability and synthesis of an iron-containing protein.
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Affiliation(s)
- Branislav Večerek
- Department of Microbiology and Immunobiology, Max F Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Isabella Moll
- Department of Microbiology and Immunobiology, Max F Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Udo Bläsi
- Department of Microbiology and Immunobiology, Max F Perutz Laboratories, University of Vienna, Vienna, Austria
- Department of Microbiology and Immunobiology, Max F Perutz Laboratories, University of Vienna, Dr. Bohrgasse 9/4, Vienna 1030, Austria. Tel.: +43 1 4277 54609; Fax: +43 1 4277 9546; E-mail:
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Lee HJ, Bang SH, Lee KH, Park SJ. Positive regulation of fur gene expression via direct interaction of fur in a pathogenic bacterium, Vibrio vulnificus. J Bacteriol 2007; 189:2629-36. [PMID: 17237166 PMCID: PMC1855807 DOI: 10.1128/jb.01791-06] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In pathogenic bacteria, the ability to acquire iron, which is mainly regulated by the ferric uptake regulator (Fur), is essential to maintain growth as well as its virulence. In Vibrio vulnificus, a human pathogen causing gastroenteritis and septicemia, fur gene expression is positively regulated by Fur when the iron concentration is limited (H.-J. Lee et al., J. Bacteriol. 185:5891-5896, 2003). Footprinting analysis revealed that an upstream region of the fur gene was protected by the Fur protein from DNase I under iron-depleted conditions. The protected region, from -142 to -106 relative to the transcription start site of the fur gene, contains distinct AT-rich repeats. Mutagenesis of this repeated sequence resulted in abolishment of binding by Fur. To confirm the role of this cis-acting element in Fur-mediated control of its own gene in vivo, fur expression was monitored in V. vulnificus strains using a transcriptional fusion containing the mutagenized Fur-binding site (fur(mt)::luxAB). Expression of fur(mt)::luxAB showed that it was not regulated by Fur and was not influenced by iron concentration. Therefore, this study demonstrates that V. vulnificus Fur acts as a positive regulator under iron-limited conditions by direct interaction with the fur upstream region.
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Affiliation(s)
- Hyun-Jung Lee
- Department of Parasitology, Yonsei University School of Medicine, 134 Shinchon-dong, Seodaemun-gu, Seoul 152-750, Republic of Korea
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Rodrigue S, Provvedi R, Jacques PE, Gaudreau L, Manganelli R. The sigma factors of Mycobacterium tuberculosis. FEMS Microbiol Rev 2006; 30:926-41. [PMID: 17064287 DOI: 10.1111/j.1574-6976.2006.00040.x] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Mycobacterium tuberculosis is a remarkable pathogen capable of adapting and surviving in various harsh conditions. Correct gene expression regulation is essential for the success of this process. The reversible association of different sigma factors is a common mechanism for reprogramming bacterial RNA polymerase and modulating the transcription of numerous genes. Thirteen putative sigma factors are encoded in the M. tuberculosis genome, several being important for virulence. Here, we analyse the latest information available on mycobacterial sigma factors and discuss their roles in the physiology and virulence of M. tuberculosis.
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Affiliation(s)
- Sébastien Rodrigue
- Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada
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Bagchi G, Chauhan S, Sharma D, Tyagi JS. Transcription and autoregulation of the Rv3134c-devR-devS operon of Mycobacterium tuberculosis. MICROBIOLOGY-SGM 2006; 151:4045-4053. [PMID: 16339949 DOI: 10.1099/mic.0.28333-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
DevR is a transcriptional regulator that mediates the genetic response of Mycobacterium tuberculosis to oxygen limitation and nitric oxide exposure. devR is co-transcribed along with devS, which encodes its cognate sensor kinase, and an upstream gene, Rv3134c. The transcriptional activity of this operon was characterized by primer extension, transcriptional fusion and electrophoretic mobility shift assays (EMSAs) under aerobic conditions. Transcription start points (Tsps) were detected upstream of both Rv3134c and devR, and the major transcript was derived from upstream of Rv3134c. Sequences with similarity to sigma factor consensus elements and to DevR-binding motifs were detected in the vicinity of the Tsps by in silico analysis. EMSAs with promoter regions and DevR protein showed that DevR binds to its own promoters in a sequence-specific manner with differing affinities. Consistent with the primer extension and EMSA data, Rv3134c promoters, and not devR promoters, were determined to be the principal promoters of this operon using reporter assays performed in Mycobacterium smegmatis and Escherichia coli. Furthermore, DevR modulated the activity of both devR and Rv3134c promoters. From these findings it is inferred that the Rv3134c-devR-devS operon is transcribed from multiple promoters and is autoregulated.
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Affiliation(s)
- Gargi Bagchi
- Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
| | - Santosh Chauhan
- Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
| | - Deepak Sharma
- Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
| | - Jaya Sivaswami Tyagi
- Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
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