1
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Liu G, Catacutan DB, Rathod K, Swanson K, Jin W, Mohammed JC, Chiappino-Pepe A, Syed SA, Fragis M, Rachwalski K, Magolan J, Surette MG, Coombes BK, Jaakkola T, Barzilay R, Collins JJ, Stokes JM. Deep learning-guided discovery of an antibiotic targeting Acinetobacter baumannii. Nat Chem Biol 2023; 19:1342-1350. [PMID: 37231267 DOI: 10.1038/s41589-023-01349-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 04/25/2023] [Indexed: 05/27/2023]
Abstract
Acinetobacter baumannii is a nosocomial Gram-negative pathogen that often displays multidrug resistance. Discovering new antibiotics against A. baumannii has proven challenging through conventional screening approaches. Fortunately, machine learning methods allow for the rapid exploration of chemical space, increasing the probability of discovering new antibacterial molecules. Here we screened ~7,500 molecules for those that inhibited the growth of A. baumannii in vitro. We trained a neural network with this growth inhibition dataset and performed in silico predictions for structurally new molecules with activity against A. baumannii. Through this approach, we discovered abaucin, an antibacterial compound with narrow-spectrum activity against A. baumannii. Further investigations revealed that abaucin perturbs lipoprotein trafficking through a mechanism involving LolE. Moreover, abaucin could control an A. baumannii infection in a mouse wound model. This work highlights the utility of machine learning in antibiotic discovery and describes a promising lead with targeted activity against a challenging Gram-negative pathogen.
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Affiliation(s)
- Gary Liu
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Denise B Catacutan
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Khushi Rathod
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Kyle Swanson
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Wengong Jin
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jody C Mohammed
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Anush Chiappino-Pepe
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Saad A Syed
- Department of Medicine, Department of Biochemistry and Biomedical Sciences, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Meghan Fragis
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
| | - Kenneth Rachwalski
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Jakob Magolan
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
| | - Michael G Surette
- Department of Medicine, Department of Biochemistry and Biomedical Sciences, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Brian K Coombes
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Tommi Jaakkola
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Regina Barzilay
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
- Abdul Latif Jameel Clinic for Machine Learning in Health, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - James J Collins
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA.
- Abdul Latif Jameel Clinic for Machine Learning in Health, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Department of Biological Engineering, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Broad Institute of MIT and Harvard, Cambridge, MA, USA.
| | - Jonathan M Stokes
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada.
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2
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Patel Y, Soni V, Rhee KY, Helmann JD. Mutations in rpoB That Confer Rifampicin Resistance Can Alter Levels of Peptidoglycan Precursors and Affect β-Lactam Susceptibility. mBio 2023; 14:e0316822. [PMID: 36779708 PMCID: PMC10128067 DOI: 10.1128/mbio.03168-22] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 01/23/2023] [Indexed: 02/14/2023] Open
Abstract
Bacteria can adapt to stressful conditions through mutations affecting the RNA polymerase core subunits that lead to beneficial changes in transcription. In response to selection with rifampicin (RIF), mutations arise in the RIF resistance-determining region (RRDR) of rpoB that reduce antibiotic binding. These changes can also alter transcription and thereby have pleiotropic effects on bacterial fitness. Here, we studied the evolution of resistance in Bacillus subtilis to the synergistic combination of RIF and the β-lactam cefuroxime (CEF). Two independent evolution experiments led to the recovery of a single rpoB allele (S487L) that was able to confer resistance to RIF and CEF through a single mutation. Two other common RRDR mutations made the cells 32 times more sensitive to CEF (H482Y) or led to only modest CEF resistance (Q469R). The diverse effects of these three mutations on CEF resistance are correlated with differences in the expression of peptidoglycan (PG) synthesis genes and in the levels of two metabolites crucial in regulating PG synthesis, glucosamine-6-phosphate (GlcN-6-P) and UDP-N-acetylglucosamine (UDP-GlcNAc). We conclude that RRDR mutations can have widely varying effects on pathways important for cell wall biosynthesis, and this may restrict the spectrum of mutations that arise during combination therapy. IMPORTANCE Rifampicin (RIF) is one of the most valued drugs in the treatment of tuberculosis. TB treatment relies on a combination therapy and for multidrug-resistant strains may include β-lactams. Mutations in rpoB present a common route for emergence of resistance to RIF. In this study, using B. subtilis as a model, we evaluate the emergence of resistance for the synergistic combination of RIF and the β-lactam cefuroxime (CEF). One clinically relevant rpoB mutation conferred resistance to both RIF and CEF, whereas one other increased CEF sensitivity. We were able to link these CEF sensitivity phenotypes to accumulation of UDP-N-acetylglucosamine (UDP-GlcNAc), which feedback regulates GlmS activity and thereby peptidoglycan synthesis. Further, we found that higher CEF concentrations precluded the emergence of high RIF resistance. Collectively, these results suggest that multidrug treatment regimens may limit the available pathways for the evolution of antibiotic resistance.
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Affiliation(s)
- Yesha Patel
- Department of Microbiology, Cornell University, Ithaca, New York, USA
| | - Vijay Soni
- Department of Medicine, Division of Infectious Diseases, Weill Cornell Medicine, New York, New York, USA
| | - Kyu Y. Rhee
- Department of Medicine, Division of Infectious Diseases, Weill Cornell Medicine, New York, New York, USA
| | - John D. Helmann
- Department of Microbiology, Cornell University, Ithaca, New York, USA
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3
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Riu M, Kim MS, Choi SK, Oh SK, Ryu CM. Elicitation of Innate Immunity by a Bacterial Volatile 2-Nonanone at Levels below Detection Limit in Tomato Rhizosphere. Mol Cells 2022; 45:502-511. [PMID: 35791736 PMCID: PMC9260139 DOI: 10.14348/molcells.2022.2009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 02/24/2022] [Accepted: 02/24/2022] [Indexed: 11/27/2022] Open
Abstract
Bacterial volatile compounds (BVCs) exert beneficial effects on plant protection both directly and indirectly. Although BVCs have been detected in vitro, their detection in situ remains challenging. The purpose of this study was to investigate the possibility of BVCs detection under in situ condition and estimate the potentials of in situ BVC to plants at below detection limit. We developed a method for detecting BVCs released by the soil bacteria Bacillus velezensis strain GB03 and Streptomyces griseus strain S4-7 in situ using solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS). Additionally, we evaluated the BVC detection limit in the rhizosphere and induction of systemic immune response in tomato plants grown in the greenhouse. Two signature BVCs, 2-nonanone and caryolan-1-ol, of GB03 and S4-7 respectively were successfully detected using the soil-vial system. However, these BVCs could not be detected in the rhizosphere pretreated with strains GB03 and S4-7. The detection limit of 2-nonanone in the tomato rhizosphere was 1 µM. Unexpectedly, drench application of 2-nonanone at 10 nM concentration, which is below its detection limit, protected tomato seedlings against Pseudomonas syringae pv. tomato. Our finding highlights that BVCs, including 2-nonanone, released by a soil bacterium are functional even when present at a concentration below the detection limit of SPME-GC-MS.
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Affiliation(s)
- Myoungjoo Riu
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Korea
- Department of Applied Biology, College of Agriculture & Life Sciences, Chungnam National University, Daejeon 34134, Korea
| | - Man Su Kim
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Korea
- Department of Biosystems and Bioengineering Program, KRIBB School of Biotechnology, University of Science and Technology (UST), Daejeon 34113, Korea
| | - Soo-Keun Choi
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Korea
- Department of Biosystems and Bioengineering Program, KRIBB School of Biotechnology, University of Science and Technology (UST), Daejeon 34113, Korea
| | - Sang-Keun Oh
- Department of Applied Biology, College of Agriculture & Life Sciences, Chungnam National University, Daejeon 34134, Korea
| | - Choong-Min Ryu
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Korea
- Department of Biosystems and Bioengineering Program, KRIBB School of Biotechnology, University of Science and Technology (UST), Daejeon 34113, Korea
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4
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Cordero M, García-Fernández J, Acosta IC, Yepes A, Avendano-Ortiz J, Lisowski C, Oesterreicht B, Ohlsen K, Lopez-Collazo E, Förstner KU, Eulalio A, Lopez D. The induction of natural competence adapts staphylococcal metabolism to infection. Nat Commun 2022; 13:1525. [PMID: 35314690 PMCID: PMC8938553 DOI: 10.1038/s41467-022-29206-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 03/03/2022] [Indexed: 11/26/2022] Open
Abstract
A central question concerning natural competence is why orthologs of competence genes are conserved in non-competent bacterial species, suggesting they have a role other than in transformation. Here we show that competence induction in the human pathogen Staphylococcus aureus occurs in response to ROS and host defenses that compromise bacterial respiration during infection. Bacteria cope with reduced respiration by obtaining energy through fermentation instead. Since fermentation is energetically less efficient than respiration, the energy supply must be assured by increasing the glycolytic flux. The induction of natural competence increases the rate of glycolysis in bacteria that are unable to respire via upregulation of DNA- and glucose-uptake systems. A competent-defective mutant showed no such increase in glycolysis, which negatively affects its survival in both mouse and Galleria infection models. Natural competence foster genetic variability and provides S. aureus with additional nutritional and metabolic possibilities, allowing it to proliferate during infection. Orthologs of natural competence genes are conserved in non-competent bacterial species, suggesting they have a role other than in transformation. Here, the authors show that competence induction in Staphylococcus aureus occurs in response to reactive oxygen species and host defenses that compromise bacterial respiration during infection, leading to increased DNA and glucose uptake and glycolytic flux.
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5
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Environmental dependence of competitive fitness in rifampin-resistant
rpoB
mutants of
Bacillus subtilis. Appl Environ Microbiol 2022; 88:e0242221. [DOI: 10.1128/aem.02422-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
RNA polymerase (RNAP) is a highly conserved macromolecular machine that contributes to the flow of genetic information from genotype to phenotype. In
Bacillus subtilis
, mutations in the
rpoB
gene encoding the β-subunit of RNAP have been shown to alter a number of global phenotypes including growth, utilization of unusual nutrient sources, sporulation, germination, and production of secondary metabolites. In addition, the spectrum of mutations in
rpoB
leading to rifampin resistance (Rif
R
) can change dramatically depending upon the environment to which
B. subtilis
cells or spores are exposed. Rif
R
rpoB
mutations have historically been associated with slower growth and reduced fitness; however, these assessments of fitness were conducted on limited collections of mutants in rich laboratory media that poorly reflect natural environments typically inhabited by
B. subtilis
. Using a novel, deep-sequencing approach in addition to traditional measurements of growth rate, lag time, and pairwise competitions, we demonstrated the competitive advantage of specific
rpoB
alleles differs depending on the growth environment in which they are determined.
IMPORTANCE
Microbial resistance to antibiotics is a growing threat to public health across the world. Historically, resistance to antibiotics has been associated with reduced fitness. A growing body of evidence indicates that resistance to rifampin, a frontline antibiotic used to treat mycobacterial and biofilm-associated infections, may increase fitness given an appropriate environment even in the absence of the selective antibiotic. Here we experimentally confirm this phenomenon by directly comparing the fitness of multiple rifampin-resistant mutants of
Bacillus subtilis
in rich LB medium and an asparagine minimal medium. Our research demonstrates that the fitness cost of rifampin resistance can vary greatly depending upon the environment. This has important implications for understanding how microbes develop antimicrobial resistance in the absence of antibiotic selection.
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Lactic Acid Bacteria Antagonism of Acid-tolerant and Antibiotic-resistant Non-staphylococcal Pathogenic Species Isolated from a Fermented Cereal Beverage using Baird-Parker Agar. NUTRITION AND FOOD SCIENCES RESEARCH 2022. [DOI: 10.52547/nfsr.9.1.31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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7
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Fujiwara D, Kawaguchi Y, Kinoshita I, Yatabe J, Narumi I, Hashimoto H, Yokobori SI, Yamagishi A. Mutation Analysis of the rpoB Gene in the Radiation-Resistant Bacterium Deinococcus radiodurans R1 Exposed to Space during the Tanpopo Experiment at the International Space Station. ASTROBIOLOGY 2021; 21:1494-1504. [PMID: 34694920 DOI: 10.1089/ast.2020.2424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
To investigate microbial viability and DNA damage, dried cell pellets of the radiation-resistant bacterium Deinococcus radiodurans were exposed to various space environmental conditions at the Exposure Facility of the International Space Station (ISS) as part of the Tanpopo mission. Mutation analysis was done by sequencing the rpoB gene encoding RNA polymerase β-subunit of the rifampicin-resistant mutants. Samples included bacteria exposed to the space environment with and without exposure to UV radiation as well as control samples held in the ISS cabin and at ground. The mutation sites of the rpoB gene obtained from the space-exposed and ISS/ground control samples were similar to the rpoB mutation sites previously reported in D. radiodurans. Most mutations were found at or near the rifampicin binding site in the RNA polymerase β-subunit. Mutation sites found in UV-exposed samples were mostly shared with non-exposed and ISS/ground control samples. These results suggest that most mutations found in our experiments were induced during procedures that were applied across all treatments: preparation, transfer from our laboratory to the ISS, return from the ISS, and storage before analysis. Some mutations may be enhanced by specific factors in the space experiments, but the mutations were also found in the spontaneous and control samples. Our experiment suggests that the dried cells of the microorganism D. radiodurans can travel without space-specific deterioration that may induce excess mutations relative to travel at Earth's surface. However, upon arrival at a recipient location, they must still be able to survive and repair the general damage induced during travel.
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Affiliation(s)
- Daisuke Fujiwara
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Yuko Kawaguchi
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Iori Kinoshita
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Jun Yatabe
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Issay Narumi
- Faculty of Life Sciences, Toyo University, Itakura, Gunma, Japan
| | - Hirofumi Hashimoto
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa, Japan
| | - Shin-Ichi Yokobori
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Akihiko Yamagishi
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa, Japan
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8
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Leehan JD, Nicholson WL. The Spectrum of Spontaneous Rifampin Resistance Mutations in the Bacillus subtilis rpoB Gene Depends on the Growth Environment. Appl Environ Microbiol 2021; 87:e0123721. [PMID: 34495706 PMCID: PMC8552901 DOI: 10.1128/aem.01237-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 09/01/2021] [Indexed: 11/20/2022] Open
Abstract
Results from previous investigations into spontaneous rifampin resistance (Rifr) mutations in the Bacillus subtilis rpoB gene suggested that the spectrum of mutations depends on the growth environment. However, these studies were limited by low sample numbers, allowing for the potential distortion of the data by the presence of "jackpot" mutations that may have arisen early in the growth of a population. Here, we addressed this issue by performing fluctuation analyses to assess both the rate and spectrum of Rifr mutations in two distinct media: LB, a complete laboratory medium, and SMMAsn, a minimal medium utilizing l-asparagine as the sole carbon source. We cultivated 60 separate populations under each growth condition and determined the mutation rate to Rifr to be slightly but significantly higher in LB cultures. We then sequenced the relevant regions of rpoB to map the spectrum of Rifr mutations under each growth condition. We found a distinct spectrum of mutations in each medium; LB cultures were dominated by the H482Y mutation (27/53 or 51%), whereas SMMAsn cultures were dominated by the S487L mutation (24/51 or 47%). Furthermore, we found through competition experiments that the relative fitness of the S487L mutant was significantly higher in SMMAsn than in LB medium. We therefore conclude that both the spectrum of Rifr mutations in the B. subtilis rpoB gene and the fitness of resulting mutants are influenced by the growth environment. IMPORTANCE The rpoB gene encodes the beta subunit of RNA polymerase, and mutations in rpoB are key determinants of resistance to the clinically important antibiotic rifampin. We show here that the spectrum of mutations in Bacillus subtilis rpoB depends on the medium in which the cells are cultivated. The results show that the growth environment not only plays a role in natural selection and fitness but also influences the probability of mutation at particular bases within the target gene.
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Affiliation(s)
- Joss D. Leehan
- Department of Microbiology and Cell Science, University of Florida, Merritt Island, Florida, USA
| | - Wayne L. Nicholson
- Department of Microbiology and Cell Science, University of Florida, Merritt Island, Florida, USA
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9
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Estimation of the Genome-Wide Mutation Rate and Spectrum in the Archaeal Species Haloferax volcanii. Genetics 2020; 215:1107-1116. [PMID: 32513815 DOI: 10.1534/genetics.120.303299] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 05/26/2020] [Indexed: 12/26/2022] Open
Abstract
Organisms adapted to life in extreme habitats (extremophiles) can further our understanding of the mechanisms of genetic stability, particularly replication and repair. Despite the harsh environmental conditions they endure, these extremophiles represent a great deal of the Earth's biodiversity. Here, for the first time in a member of the archaeal domain, we report a genome-wide assay of spontaneous mutations in the halophilic species Haloferax volcanii using a direct and unbiased method: mutation accumulation experiments combined with deep whole-genome sequencing. H. volcanii is a key model organism not only for the study of halophilicity, but also for archaeal biology in general. Our methods measure the genome-wide rate, spectrum, and spatial distribution of spontaneous mutations. The estimated base substitution rate of 3.15 × 10-10 per site per generation, or 0.0012 per genome per generation, is similar to the value found in mesophilic prokaryotes (optimal growth at ∼20-45°). This study contributes to a comprehensive phylogenetic view of how evolutionary forces and molecular mechanisms shape the rate and molecular spectrum of mutations across the tree of life.
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10
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Serrano E, Carrasco B. Measurement of the Length of the Integrated Donor DNA during Bacillus subtilis Natural Chromosomal Transformation. Bio Protoc 2019; 9:e3338. [PMID: 33654843 DOI: 10.21769/bioprotoc.3338] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/19/2019] [Accepted: 07/22/2019] [Indexed: 11/02/2022] Open
Abstract
For natural transformation to occur, bacterial cells must first develop a programmed physiological state called competence. Competence in Bacillus subtilis, which occurs only in a fraction of cells, is a transient stress response that allows cells to take up DNA from the environment. During natural chromosomal transformation, the internalized linear single-stranded (ss) DNA recombines with the identical (homologous) or partially identical (homeologous) sequence of the resident duplex. The length of the integrated DNA, which can be measured, depends on the percentage of sequence divergence between the donor (internalized) and the recipient (chromosomal) DNAs. The following protocol describes how to induce the development of competence in B. subtilis cells, how to transform them with donor DNAs representing different percentages of sequence divergence compared with the recipient chromosomal DNA, how to calculate the chromosomal transformation efficiency for each of them, and how to amplify the chromosomal DNA from the transformants in order to measure the length in base pairs (bp) of the integrated donor DNA.
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Affiliation(s)
- Ester Serrano
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 28049 Madrid, Spain
| | - Begoña Carrasco
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 28049 Madrid, Spain
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11
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Valenzuela‐García LI, Ayala‐García VM, Regalado‐García AG, Setlow P, Pedraza‐Reyes M. Transcriptional coupling (Mfd) and DNA damage scanning (DisA) coordinate excision repair events for efficient Bacillus subtilis spore outgrowth. Microbiologyopen 2018; 7:e00593. [PMID: 29536659 PMCID: PMC6182552 DOI: 10.1002/mbo3.593] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 01/06/2018] [Indexed: 01/16/2023] Open
Abstract
The absence of base excision repair (BER) proteins involved in processing ROS-promoted genetic insults activates a DNA damage scanning (DisA)-dependent checkpoint event in outgrowing Bacillus subtilis spores. Here, we report that genetic disabling of transcription-coupled repair (TCR) or nucleotide excision repair (NER) pathways severely affected outgrowth of ΔdisA spores, and much more so than the effects of these mutations on log phase growth. This defect delayed the first division of spore's nucleoid suggesting that unrepaired lesions affected transcription and/or replication during outgrowth. Accordingly, return to life of spores deficient in DisA/Mfd or DisA/UvrA was severely affected by a ROS-inducer or a replication blocking agent, hydrogen peroxide and 4-nitroquinoline-oxide, respectively. Mutation frequencies to rifampin resistance (Rifr ) revealed that DisA allowed faithful NER-dependent DNA repair but activated error-prone repair in TCR-deficient outgrowing spores. Sequencing analysis of rpoB from spontaneous Rifr colonies revealed that mutations resulting from base deamination predominated in outgrowing wild-type spores. Interestingly, a wide range of base substitutions promoted by oxidized DNA bases were detected in ΔdisA and Δmfd outgrown spores. Overall, our results suggest that Mfd and DisA coordinate excision repair events in spore outgrowth to eliminate DNA lesions that interfere with replication and transcription during this developmental period.
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Affiliation(s)
| | | | | | - Peter Setlow
- Department of Molecular Biology and BiophysicsUConn HealthFarmingtonCTUSA
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12
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Fajardo-Cavazos P, Leehan JD, Nicholson WL. Alterations in the Spectrum of Spontaneous Rifampicin-Resistance Mutations in the Bacillus subtilis rpoB Gene after Cultivation in the Human Spaceflight Environment. Front Microbiol 2018; 9:192. [PMID: 29491852 PMCID: PMC5817088 DOI: 10.3389/fmicb.2018.00192] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 01/29/2018] [Indexed: 01/20/2023] Open
Abstract
The effect of Bacillus subtilis exposure to the human spaceflight environment on growth, mutagenic frequency, and spectrum of mutations to rifampicin resistance (RifR) was investigated. B. subtilis cells were cultivated in Biological Research in Canister-Petri Dish Fixation Units (BRIC-PDFUs) on two separate missions to the International Space Station (ISS), dubbed BRIC-18 and BRIC-21, with matching asynchronous ground controls. No statistically significant difference in either growth or in the frequency of mutation to RifR was found in either experiment. However, nucleotide sequencing of the RifR regions of the rpoB gene from RifR mutants revealed dramatic differences in the spectrum of mutations between flight (FL) and ground control (GC) samples, including two newly discovered rpoB alleles in the FL samples (Q137R and L489S). The results strengthen the idea that exposure to the human spaceflight environment causes unique stresses on bacteria, leading to alterations in their mutagenic potential.
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Affiliation(s)
| | | | - Wayne L. Nicholson
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, United States
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13
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Suzuki H, Taketani T, Kobayashi J, Ohshiro T. Antibiotic resistance mutations induced in growing cells of Bacillus-related thermophiles. J Antibiot (Tokyo) 2018; 71:382-389. [PMID: 29348523 DOI: 10.1038/s41429-017-0003-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 10/12/2017] [Accepted: 10/23/2017] [Indexed: 12/20/2022]
Abstract
Stress-induced mutagenesis can assist pathogens in generating drug-resistant cells during antibiotic therapy; however, if and how antibiotics induce mutagenesis in microbes remains poorly understood. A non-pathogenic thermophile, Geobacillus kaustophilus HTA426, efficiently produces derivative cells resistant to rifampicin and streptomycin via rpoB and rpsL mutations, respectively. Here, we examined this phenomenon to suggest a novel mutagenic mode induced by antibiotics. Fluctuation analysis indicated that mutations occurred via spontaneous mutations during culture. However, mutations were much more frequent in growing cells than stationary cells, and mutation sites were varied through cell growth. These observations suggested that growing cells induced mutagenesis in response to antibiotics. An in-frame deletion of mfd, which governs transcription-coupled repair to correct DNA lesions on the transcribed strand, caused mutations that were comparable between growing and stationary cells; therefore, the mutagenic mechanism was attributable to DNA repair defects where growing cells depressed mfd function. Mutations occurred more frequently at optimal growth temperatures for G. kaustophilus than at a higher growth temperature, suggesting that the mutagenesis relies on active cellular activities rather than high temperature-associated DNA damage. In addition, the mutagenesis may involve a mutagenic factor targeting these sites, in addition to mfd depression, because rpoB and rpsL mutations were dominant at thymine and guanine sites on the transcribed strand. A similar mutagenic profile was observed for other Geobacillus and thermophilic Bacillus species. This suggests that Bacillus-related thermophiles commonly induce mutagenesis in response to rifampicin and streptomycin to produce resistant cells.
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Affiliation(s)
- Hirokazu Suzuki
- Functional Genomics of Extremophiles, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-Ku, Fukuoka, 812-8581, Japan. .,Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8550, Japan.
| | - Tatsunari Taketani
- Department of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8550, Japan
| | - Jyumpei Kobayashi
- Functional Genomics of Extremophiles, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-Ku, Fukuoka, 812-8581, Japan.,Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8550, Japan
| | - Takashi Ohshiro
- Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8550, Japan
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Paschalis V, Le Chatelier E, Green M, Nouri H, Képès F, Soultanas P, Janniere L. Interactions of the Bacillus subtilis DnaE polymerase with replisomal proteins modulate its activity and fidelity. Open Biol 2017; 7:170146. [PMID: 28878042 PMCID: PMC5627055 DOI: 10.1098/rsob.170146] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/01/2017] [Indexed: 01/09/2023] Open
Abstract
During Bacillus subtilis replication two replicative polymerases function at the replisome to collectively carry out genome replication. In a reconstituted in vitro replication assay, PolC is the main polymerase while the lagging strand DnaE polymerase briefly extends RNA primers synthesized by the primase DnaG prior to handing-off DNA synthesis to PolC. Here, we show in vivo that (i) the polymerase activity of DnaE is essential for both the initiation and elongation stages of DNA replication, (ii) its error rate varies inversely with PolC concentration, and (iii) its misincorporations are corrected by the mismatch repair system post-replication. We also found that the error rates in cells encoding mutator forms of both PolC and DnaE are significantly higher (up to 15-fold) than in PolC mutants. In vitro, we showed that (i) the polymerase activity of DnaE is considerably stimulated by DnaN, SSB and PolC, (ii) its error-prone activity is strongly inhibited by DnaN, and (iii) its errors are proofread by the 3' > 5' exonuclease activity of PolC in a stable template-DnaE-PolC complex. Collectively our data show that protein-protein interactions within the replisome modulate the activity and fidelity of DnaE, and confirm the prominent role of DnaE during B. subtilis replication.
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Affiliation(s)
- Vasileios Paschalis
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Emmanuelle Le Chatelier
- Institut National de la Recherche Agronomique, Génétique Microbienne, 78350 Jouy-en-Josas, France
| | - Matthew Green
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Hamid Nouri
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
| | - François Képès
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
| | - Panos Soultanas
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Laurent Janniere
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
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15
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Fajardo-Cavazos P, Nicholson WL. Cultivation of Staphylococcus epidermidis in the Human Spaceflight Environment Leads to Alterations in the Frequency and Spectrum of Spontaneous Rifampicin-Resistance Mutations in the rpoB Gene. Front Microbiol 2016; 7:999. [PMID: 27446039 PMCID: PMC4923109 DOI: 10.3389/fmicb.2016.00999] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 06/13/2016] [Indexed: 12/15/2022] Open
Abstract
Bacteria of the genus Staphylococcus are persistent inhabitants of human spaceflight habitats and represent potential opportunistic pathogens. The effect of the human spaceflight environment on the growth and the frequency of mutations to antibiotic resistance in the model organism Staphylococcus epidermidis strain ATCC12228 was investigated. Six cultures of the test organism were cultivated in biological research in canisters-Petri dish fixation units for 122 h on orbit in the International Space Station (ISS) as part of the SpaceX-3 resupply mission. Asynchronous ground controls (GCs) consisted of identical sets of cultures cultivated for 122 h in the ISS Environmental Simulator at Kennedy Space Center. S. epidermidis exhibited significantly lower viable counts but significantly higher frequencies of mutation to rifampicin (Rif) resistance in space vs. GC cultures. The spectrum of mutations in the rpoB gene leading to Rif(R) was altered in S. epidermidis isolates cultivated in the ISS compared to GCs. The results suggest that the human spaceflight environment induces unique physiologic stresses on growing bacterial cells leading to changes in mutagenic potential.
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Affiliation(s)
| | - Wayne L Nicholson
- Department of Microbiology and Cell Science, University of Florida, Merritt Island FL, USA
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16
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Carrasco B, Serrano E, Sánchez H, Wyman C, Alonso JC. Chromosomal transformation in Bacillus subtilis is a non-polar recombination reaction. Nucleic Acids Res 2016; 44:2754-68. [PMID: 26786319 PMCID: PMC4824099 DOI: 10.1093/nar/gkv1546] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 12/29/2015] [Indexed: 11/13/2022] Open
Abstract
Natural chromosomal transformation is one of the primary driving forces of bacterial evolution. This reaction involves the recombination of the internalized linear single-stranded (ss) DNA with the homologous resident duplex via RecA-mediated integration in concert with SsbA and DprA or RecO. We show that sequence divergence prevents Bacillus subtilis chromosomal transformation in a log-linear fashion, but it exerts a minor effect when the divergence is localized at a discrete end. In the nucleotide bound form, RecA shows no apparent preference to initiate recombination at the 3′- or 5′-complementary end of the linear duplex with circular ssDNA, but nucleotide hydrolysis is required when heterology is present at both ends. RecA·dATP initiates pairing of the linear 5′ and 3′ complementary ends, but only initiation at the 5′-end remains stably paired in the absence of SsbA. Our results suggest that during gene transfer RecA·ATP, in concert with SsbA and DprA or RecO, shows a moderate preference for the 3′-end of the duplex. We show that RecA-mediated recombination initiated at the 3′- or 5′-complementary end might have significant implication on the ecological diversification of bacterial species with natural transformation.
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Affiliation(s)
- Begoña Carrasco
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 28049 Madrid, Spain
| | - Ester Serrano
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 28049 Madrid, Spain
| | - Humberto Sánchez
- Department of Genetics, Cancer Genomics Netherlands, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Claire Wyman
- Department of Genetics, Cancer Genomics Netherlands, Erasmus University Medical Center, Rotterdam, The Netherlands Department of Radiation Oncology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Juan C Alonso
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 28049 Madrid, Spain
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17
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Nicholson WL, Park R. Anaerobic growth of Bacillus subtilis alters the spectrum of spontaneous mutations in the rpoB gene leading to rifampicin resistance. FEMS Microbiol Lett 2015; 362:fnv213. [PMID: 26538577 DOI: 10.1093/femsle/fnv213] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2015] [Indexed: 11/14/2022] Open
Abstract
Spontaneous rifampicin-resistant (RFM(R)) mutants were isolated from Bacillus subtilis 168 cultivated in the presence or absence of oxygen. By DNA sequencing, the mutations were located within Cluster I of the rpoB gene encoding the β subunit of RNA polymerase. The spectrum of RFM(R) rpoB mutations isolated from B. subtilis cells grown anaerobically differed from aerobically grown cells, not only with respect to the location of mutations within Cluster I but also in the class of mutation observed (transition versus transversion). In the absence of RFM, RFM(R) mutants exhibited poorer growth under anaerobic conditions than did the wild-type strain, indicating their lower fitness in the absence of antibiotic selection.
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Affiliation(s)
- Wayne L Nicholson
- Department of Microbiology and Cell Science, Space Life Sciences Laboratory, University of Florida, 505 Odyssey Way, Room 201-B, Exploration Park at Kennedy Space Center, Merritt Island, FL 32953, USA
| | - Roy Park
- Department of Microbiology and Cell Science, Space Life Sciences Laboratory, University of Florida, 505 Odyssey Way, Room 201-B, Exploration Park at Kennedy Space Center, Merritt Island, FL 32953, USA
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18
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Thermoadaptation-directed enzyme evolution in an error-prone thermophile derived from Geobacillus kaustophilus HTA426. Appl Environ Microbiol 2014; 81:149-58. [PMID: 25326311 DOI: 10.1128/aem.02577-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thermostability is an important property of enzymes utilized for practical applications because it allows long-term storage and use as catalysts. In this study, we constructed an error-prone strain of the thermophile Geobacillus kaustophilus HTA426 and investigated thermoadaptation-directed enzyme evolution using the strain. A mutation frequency assay using the antibiotics rifampin and streptomycin revealed that G. kaustophilus had substantially higher mutability than Escherichia coli and Bacillus subtilis. The predominant mutations in G. kaustophilus were A · T→G · C and C · G→T · A transitions, implying that the high mutability of G. kaustophilus was attributable in part to high-temperature-associated DNA damage during growth. Among the genes that may be involved in DNA repair in G. kaustophilus, deletions of the mutSL, mutY, ung, and mfd genes markedly enhanced mutability. These genes were subsequently deleted to construct an error-prone thermophile that showed much higher (700- to 9,000-fold) mutability than the parent strain. The error-prone strain was auxotrophic for uracil owing to the fact that the strain was deficient in the intrinsic pyrF gene. Although the strain harboring Bacillus subtilis pyrF was also essentially auxotrophic, cells became prototrophic after 2 days of culture under uracil starvation, generating B. subtilis PyrF variants with an enhanced half-denaturation temperature of >10°C. These data suggest that this error-prone strain is a promising host for thermoadaptation-directed evolution to generate thermostable variants from thermolabile enzymes.
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Koch A, Mizrahi V, Warner DF. The impact of drug resistance on Mycobacterium tuberculosis physiology: what can we learn from rifampicin? Emerg Microbes Infect 2014; 3:e17. [PMID: 26038512 PMCID: PMC3975073 DOI: 10.1038/emi.2014.17] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 12/12/2013] [Accepted: 12/30/2013] [Indexed: 01/08/2023]
Abstract
The emergence of drug-resistant pathogens poses a major threat to public health. Although influenced by multiple factors, high-level resistance is often associated with mutations in target-encoding or related genes. The fitness cost of these mutations is, in turn, a key determinant of the spread of drug-resistant strains. Rifampicin (RIF) is a frontline anti-tuberculosis agent that targets the rpoB-encoded β subunit of the DNA-dependent RNA polymerase (RNAP). In Mycobacterium tuberculosis (Mtb), RIF resistance (RIF(R)) maps to mutations in rpoB that are likely to impact RNAP function and, therefore, the ability of the organism to cause disease. However, while numerous studies have assessed the impact of RIF(R) on key Mtb fitness indicators in vitro, the consequences of rpoB mutations for pathogenesis remain poorly understood. Here, we examine evidence from diverse bacterial systems indicating very specific effects of rpoB polymorphisms on cellular physiology, and consider these observations in the context of Mtb. In addition, we discuss the implications of these findings for the propagation of clinically relevant RIF(R) mutations. While our focus is on RIF, we also highlight results which suggest that drug-independent effects might apply to a broad range of resistance-associated mutations, especially in an obligate pathogen increasingly linked with multidrug resistance.
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Affiliation(s)
- Anastasia Koch
- Medical Research Council/National Health Laboratory Service/University of Cape Town Molecular Mycobacteriology Research Unit, Department of Science and Technology/National Research Foundation Centre of Excellence for Biomedical Tuberculosis Research, Institute of Infectious Disease and Molecular Medicine and Department of Clinical Laboratory Sciences, University of Cape Town , Cape Town 7701, South Africa
| | - Valerie Mizrahi
- Medical Research Council/National Health Laboratory Service/University of Cape Town Molecular Mycobacteriology Research Unit, Department of Science and Technology/National Research Foundation Centre of Excellence for Biomedical Tuberculosis Research, Institute of Infectious Disease and Molecular Medicine and Department of Clinical Laboratory Sciences, University of Cape Town , Cape Town 7701, South Africa
| | - Digby F Warner
- Medical Research Council/National Health Laboratory Service/University of Cape Town Molecular Mycobacteriology Research Unit, Department of Science and Technology/National Research Foundation Centre of Excellence for Biomedical Tuberculosis Research, Institute of Infectious Disease and Molecular Medicine and Department of Clinical Laboratory Sciences, University of Cape Town , Cape Town 7701, South Africa
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20
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Abstract
DNA helicases have important roles in genome maintenance. The RecD helicase has been well studied as a component of the heterotrimeric RecBCD helicase-nuclease enzyme important for double-strand break repair in Escherichia coli. Interestingly, many bacteria lack RecBC and instead contain a RecD2 helicase, which is not known to function as part of a larger complex. Depending on the organism studied, RecD2 has been shown to provide resistance to a broad range of DNA-damaging agents while also contributing to mismatch repair (MMR). Here we investigated the importance of Bacillus subtilis RecD2 helicase to genome integrity. We show that deletion of recD2 confers a modest increase in the spontaneous mutation rate and that the mutational signature in ΔrecD2 cells is not consistent with an MMR defect, indicating a new function for RecD2 in B. subtilis. To further characterize the role of RecD2, we tested the deletion strain for sensitivity to DNA-damaging agents. We found that loss of RecD2 in B. subtilis sensitized cells to several DNA-damaging agents that can block or impair replication fork movement. Measurement of replication fork progression in vivo showed that forks collapse more frequently in ΔrecD2 cells, supporting the hypothesis that RecD2 is important for normal replication fork progression. Biochemical characterization of B. subtilis RecD2 showed that it is a 5'-3' helicase and that it directly binds single-stranded DNA binding protein. Together, our results highlight novel roles for RecD2 in DNA replication which help to maintain replication fork integrity during normal growth and when forks encounter DNA damage.
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21
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Du X, Hua X, Qu T, Jiang Y, Zhou Z, Yu Y. Molecular characterization of Rifr mutations in Enterococcus faecalis and Enterococcus faecium. J Chemother 2013; 26:217-21. [PMID: 24070269 DOI: 10.1179/1973947813y.0000000137] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mutation rate is an important factor affecting the appearance and spread of acquired antibiotic resistance. The frequencies and types of enterococci mutations were determined in this study. The MICs of rifampicin in enterococci and their rifampicin-resistant mutants were determined by the Clinical and Laboratory Standards Institute (CLSI) agar dilution method. The Enterococcus faecalis isolates A15 and 18165 showed no significant differences in mutation frequencies or mutation rates. In Enterococcus faecium, the mutation frequency and mutation rate were both 6·4-fold lower than in E. faecalis. The spectrum of mutations characterized in E. faecium B42 differed significantly from that of E. faecalis. The types and rate of mutations indicated that E. faecalis had a higher potential to develop linezolid resistance. Rifampicin resistance was associated with mutations in the rpoB gene. Rifampicin MICs for the E. faecalis mutant were 2048 mg/l, but rifampicin MICs for E. faecium mutants ranged from 64 to 1024 mg/l.
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22
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de Oliveira RR, Nicholson WL. The LysR-type transcriptional regulator (LTTR) AlsR indirectly regulates expression of the Bacillus subtilis bdhA gene encoding 2,3-butanediol dehydrogenase. Appl Microbiol Biotechnol 2013; 97:7307-16. [PMID: 23576037 DOI: 10.1007/s00253-013-4871-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 03/19/2013] [Indexed: 11/26/2022]
Abstract
Bacillus subtilis ferments pyruvate to 2,3-butanediol via α-acetolactate synthase, α-acetolactate decarboxylase, and butanediol dehydrogenase (BDH), encoded by the alsSD operon and the unlinked monocistronic bdhA gene, respectively. Upstream and divergent from alsSD is the alsR gene that encodes AlsR, a member of the LysR-type transcriptional regulator family. AlsR directly stimulates alsSD transcription by binding to characteristic sites preceding the alsS promoter, but its effect on bdhA expression was unknown. The effect of AlsR on bdhA expression was assessed in a wild-type strain and a congenic strain carrying an alsR::spc knockout mutation by measuring: (a) expression of a transcriptional bdhA-lacZ fusion; (b) bdhA mRNA steady-state levels by quantitative reverse transcriptase PCR; and (c) expression of BDH enzymatic activity. Activation of bdhA expression occurred in early stationary phase, and expression was lowered, but not abolished, in the alsR::spc mutant. Mapping the transcriptional start site of bdhA by primer extension revealed a 268-nucleotide 5'-untranslated region preceding the bdhA initiation methionine codon. Transcription initiation was not reduced in the alsR::spc mutant, and by electrophoretic mobility shift assay, purified AlsR protein did not bind to the bdhA promoter region, suggesting that bdhA expression is indirectly under AlsR transcriptional control.
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Affiliation(s)
- Rafael R de Oliveira
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, USA
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23
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Moeller R, Reitz G, Nicholson The Protect Team WL, Horneck G. Mutagenesis in bacterial spores exposed to space and simulated martian conditions: data from the EXPOSE-E spaceflight experiment PROTECT. ASTROBIOLOGY 2012; 12:457-468. [PMID: 22680692 DOI: 10.1089/ast.2011.0739] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
As part of the PROTECT experiment of the EXPOSE-E mission on board the International Space Station (ISS), the mutagenic efficiency of space was studied in spores of Bacillus subtilis 168. After 1.5 years' exposure to selected parameters of outer space or simulated martian conditions, the rates of induced mutations to rifampicin resistance (Rif(R)) and sporulation deficiency (Spo(-)) were quantified. In all flight samples, both mutations, Rif(R) and Spo(-), were induced and their rates increased by several orders of magnitude. Extraterrestrial solar UV radiation (>110 nm) as well as simulated martian UV radiation (>200 nm) led to the most pronounced increase (up to nearly 4 orders of magnitude); however, mutations were also induced in flight samples shielded from insolation, which were exposed to the same conditions except solar irradiation. Nucleotide sequencing located the Rif(R) mutations in the rpoB gene encoding the β-subunit of RNA polymerase. Mutations isolated from flight and parallel mission ground reference (MGR) samples were exclusively localized to Cluster I. The 21 Rif(R) mutations isolated from the flight experiment showed all a C to T transition and were all localized to one hotspot: H482Y. In mutants isolated from the MGR, the spectrum was wider with predicted amino acid changes at residues Q469K/L/R, H482D/P/R/Y, and S487L. The data show the unique mutagenic power of space and martian surface conditions as a consequence of DNA injuries induced by solar UV radiation and space vacuum or the low pressure of Mars.
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Affiliation(s)
- Ralf Moeller
- Radiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center (DLR) , Cologne, Germany.
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24
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Hua X, Xu X, Li M, Wang C, Tian B, Hua Y. Three nth homologs are all required for efficient repair of spontaneous DNA damage in Deinococcus radiodurans. Extremophiles 2012; 16:477-84. [PMID: 22527041 DOI: 10.1007/s00792-012-0447-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 04/02/2012] [Indexed: 11/27/2022]
Abstract
Deinococcus radiodurans is a bacterium that can survive extreme DNA damage. To understand the role of endonuclease III (Nth) in oxidative repair and mutagenesis, we constructed nth single, double and triple mutants. The nth mutants showed no significant difference with wild type in both IR resistance and H(2)O(2) resistance. We characterized these strains with regard to mutation rates and mutation spectrum using the rpoB/Rif(r) system. The Rif(r) frequency of mutant MK1 (△dr0289) was twofold higher than that of wild type. The triple mutant of nth (ME3)generated a mutation frequency 34.4-fold, and a mutation rate 13.8-fold higher than the wild type. All strains demonstrated specific mutational hotspots. Each single mutant had higher spontaneous mutation frequency than wild type at base substitution (G:C → A:T). The mutational response was further increased in the double and triple mutants. The higher mutation rate and mutational response in ME3 suggested that the three nth homologs had non-overlapped and overlapped substrate spectrum in endogenous oxidative DNA repair.
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Affiliation(s)
- Xiaoting Hua
- Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, 310029, China.
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25
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Moeller R, Vlašić I, Reitz G, Nicholson WL. Role of altered rpoB alleles in Bacillus subtilis sporulation and spore resistance to heat, hydrogen peroxide, formaldehyde, and glutaraldehyde. Arch Microbiol 2012; 194:759-67. [PMID: 22484477 DOI: 10.1007/s00203-012-0811-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 03/21/2012] [Accepted: 03/23/2012] [Indexed: 11/29/2022]
Abstract
Mutations in the RNA polymerase β-subunit gene rpoB causing resistance to rifampicin (Rif(R)) in Bacillus subtilis were previously shown to lead to alterations in the expression of a number of global phenotypes known to be under transcriptional control. To better understand the influence of rpoB mutations on sporulation and spore resistance to heat and chemicals, cells and spores of the wild-type and twelve distinct congenic Rif(R) mutant strains of B. subtilis were tested. Different levels of glucose catabolite repression during sporulation and spore resistance to heat and chemicals were observed in the Rif(R) mutants, indicating the important role played by the RNA polymerase β-subunit, not only in the catalytic aspect of transcription, but also in the initiation of sporulation and in the spore resistance properties of B. subtilis.
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Affiliation(s)
- Ralf Moeller
- Institute of Aerospace Medicine, German Aerospace Center, Linder Hoehe, 51147 Cologne, Germany.
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26
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Mutations in the β subunit of RNA polymerase alter intrinsic cephalosporin resistance in Enterococci. Antimicrob Agents Chemother 2012; 56:2022-7. [PMID: 22290974 DOI: 10.1128/aac.06077-11] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
As major causes of hospital-acquired infections, antibiotic-resistant enterococci are a serious public health concern. Enterococci are intrinsically resistant to many cephalosporin antibiotics, a trait that enables proliferation in patients undergoing cephalosporin therapy. Although a few genetic determinants of cephalosporin resistance in enterococci have been described, overall, many questions remain about the underlying genetic and biochemical basis for cephalosporin resistance. Here we describe an unexpected effect of specific mutations in the β subunit of RNA polymerase (RNAP) on intrinsic cephalosporin resistance in enterococci. We found that RNAP mutants, selected initially on the basis of their ability to provide resistance to rifampin, resulted in allele-specific alterations of the intrinsic resistance of enterococci toward expanded- and broad-spectrum cephalosporins. These mutations did not affect resistance toward a diverse collection of other antibiotics that target a range of alternative cellular processes. We propose that the RNAP mutations identified here lead to alterations in transcription of as-yet-unknown genes that are critical for cellular adaption to cephalosporin stress.
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27
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Hydrogen peroxide-dependent DNA release and transfer of antibiotic resistance genes in Streptococcus gordonii. J Bacteriol 2011; 193:6912-22. [PMID: 21984796 DOI: 10.1128/jb.05791-11] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Certain oral streptococci produce H(2)O(2) under aerobic growth conditions to inhibit competing species like Streptococcus mutans. Additionally, H(2)O(2) production causes the release of extracellular DNA (eDNA). eDNA can participate in several important functions: biofilm formation and cell-cell aggregation are supported by eDNA, while eDNA can serve as a nutrient and as an antimicrobial agent by chelating essential cations. eDNA contains DNA fragments of a size that has the potential to transfer genomic information. By using Streptococcus gordonii as a model organism for streptococcal H(2)O(2) production, H(2)O(2)-dependent eDNA release was further investigated. Under defined growth conditions, the eDNA release process was shown to be entirely dependent on H(2)O(2). Chromosomal DNA damage seems to be the intrinsic signal for the release, although only actively growing cells were proficient eDNA donors. Interestingly, the process of eDNA production was found to be coupled with the induction of the S. gordonii natural competence system. Consequently, the production of H(2)O(2) triggered the transfer of antibiotic resistance genes. These results suggest that H(2)O(2) is potentially much more than a simple toxic metabolic by-product; rather, its production could serve as an important environmental signal that facilitates species evolution by transfer of genetic information and an increase in the mutation rate.
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Activation of dormant secondary metabolism neotrehalosadiamine synthesis by an RNA polymerase mutation in Bacillus subtilis. Biosci Biotechnol Biochem 2011; 75:618-23. [PMID: 21512256 DOI: 10.1271/bbb.100854] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Microorganisms possess the ability to produce a variety of commercially important secondary metabolites such as antibiotics. Although it becomes harder and harder to discover useful new compounds, microorganisms still have the potential to produce unknown compounds. One of the reasons for the difficulty in finding new compounds is that the expression level of many secondary metabolite genes is insufficient in wild-type strains. Therefore, a new method of activating gene expression might be a powerful tool for the screening of novel compounds and for strain improvement to overproduce useful compounds. We found that the rifampicin-resistant RNA polymerase mutations stimulate the expression of antibiotic synthetic gene clusters in several microorganisms. In the case of the Gram-positive model organism Bacillus subtilis, one of the rifampicin-resistance mutations resulted in the activation of a dormant secondary metabolism, neotrehalosadiamine synthesis. To clarify this activation mechanism, we first identified the neotrehalosadiamine biosynthetic operon and investigated its transcriptional regulation. Here we summarize our findings on the transcriptional regulation of the neotrehalosadiamine biosynthetic operon and discuss a crucial effect of the rifampicin-resistance mutation on the expression of dormant genes.
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Mismatch repair modulation of MutY activity drives Bacillus subtilis stationary-phase mutagenesis. J Bacteriol 2010; 193:236-45. [PMID: 20971907 DOI: 10.1128/jb.00940-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Stress-promoted mutations that occur in nondividing cells (adaptive mutations) have been implicated strongly in causing genetic variability as well as in species survival and evolutionary processes. Oxidative stress-induced DNA damage has been associated with generation of adaptive His(+) and Met(+) but not Leu(+) revertants in strain Bacillus subtilis YB955 (hisC952 metB5 leuC427). Here we report that an interplay between MutY and MutSL (mismatch repair system [MMR]) plays a pivotal role in the production of adaptive Leu(+) revertants. Essentially, the genetic disruption of MutY dramatically reduced the reversion frequency to the leu allele in this model system. Moreover, the increased rate of adaptive Leu(+) revertants produced by a MutSL knockout strain was significantly diminished following mutY disruption. Interestingly, although the expression of mutY took place during growth and stationary phase and was not under the control of RecA, PerR, or σ(B), a null mutation in the mutSL operon increased the expression of mutY several times. Thus, in starved cells, saturation of the MMR system may induce the expression of mutY, disturbing the balance between MutY and MMR proteins and aiding in the production of types of mutations detected by reversion to leucine prototrophy. In conclusion, our results support the idea that MMR regulation of the mutagenic/antimutagenic properties of MutY promotes stationary-phase mutagenesis in B. subtilis cells.
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Moeller R, Reitz G, Berger T, Okayasu R, Nicholson WL, Horneck G. Astrobiological aspects of the mutagenesis of cosmic radiation on bacterial spores. ASTROBIOLOGY 2010; 10:509-521. [PMID: 20624059 DOI: 10.1089/ast.2009.0429] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Based on their unique resistance to various space parameters, Bacillus endospores are one of the model systems used for astrobiological studies. In this study, spores of B. subtilis were used to study the effects of galactic cosmic radiation (GCR) on spore survival and induced mutagenesis. In interplanetary space, outside Earth's protective magnetic field, spore-containing rocks would be exposed to bombardment by high-energy charged particle radiation from galactic sources and from the Sun, which consists of photons (X-rays, gamma rays), protons, electrons, and heavy, high-energy charged (HZE) particles. B. subtilis spores were irradiated with X-rays and accelerated heavy ions (helium, carbon, silicon and iron) in the linear energy transfer (LET) range of 2-200 keV/mum. Spore survival and the rate of the induced mutations to rifampicin resistance (Rif(R)) depended on the LET of the applied species of ions and radiation, whereas the exposure to high-energy charged particles, for example, iron ions, led to a low level of spore survival and increased frequency of mutation to Rif(R) compared to low-energy charged particles and X-rays. Twenty-one Rif(R) mutant spores were isolated from X-ray and heavy ion-irradiated samples. Nucleotide sequencing located the Rif(R) mutations in the rpoB gene encoding the beta-subunit of RNA polymerase. Most mutations were primarily found in Cluster I and were predicted to result in amino acid changes at residues Q469L, A478V, and H482P/Y. Four previously undescribed alleles in B. subtilis rpoB were isolated: L467P, R484P, and A488P in Cluster I and H507R in the spacer between Clusters I and II. The spectrum of Rif(R) mutations arising from spores exposed to components of GCR is distinctly different from those of spores exposed to simulated space vacuum and martian conditions.
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Affiliation(s)
- Ralf Moeller
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Radiation Biology Department, Cologne, Germany.
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Mutations in the Bacillus subtilis beta clamp that separate its roles in DNA replication from mismatch repair. J Bacteriol 2010; 192:3452-63. [PMID: 20453097 DOI: 10.1128/jb.01435-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The beta clamp is an essential replication sliding clamp required for processive DNA synthesis. The beta clamp is also critical for several additional aspects of DNA metabolism, including DNA mismatch repair (MMR). The dnaN5 allele of Bacillus subtilis encodes a mutant form of beta clamp containing the G73R substitution. Cells with the dnaN5 allele are temperature sensitive for growth due to a defect in DNA replication at 49 degrees C, and they show an increase in mutation frequency caused by a partial defect in MMR at permissive temperatures. We selected for intragenic suppressors of dnaN5 that rescued viability at 49 degrees C to determine if the DNA replication defect could be separated from the MMR defect. We isolated three intragenic suppressors of dnaN5 that restored growth at the nonpermissive temperature while maintaining an increase in mutation frequency. All three dnaN alleles encoded the G73R substitution along with one of three novel missense mutations. The missense mutations isolated were S22P, S181G, and E346K. Of these, S181G and E346K are located near the hydrophobic cleft of the beta clamp, a common site occupied by proteins that bind the beta clamp. Using several methods, we show that the increase in mutation frequency resulting from each dnaN allele is linked to a defect in MMR. Moreover, we found that S181G and E346K allowed growth at elevated temperatures and did not have an appreciable effect on mutation frequency when separated from G73R. Thus, we found that specific residue changes in the B. subtilis beta clamp separate the role of the beta clamp in DNA replication from its role in MMR.
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Fajardo-Cavazos P, Schuerger AC, Nicholson WL. Exposure of DNA and Bacillus subtilis spores to simulated martian environments: use of quantitative PCR (qPCR) to measure inactivation rates of DNA to function as a template molecule. ASTROBIOLOGY 2010; 10:403-411. [PMID: 20528195 DOI: 10.1089/ast.2009.0408] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Several NASA and ESA missions are planned for the next decade to investigate the possibility of present or past life on Mars. Evidence of extraterrestrial life will likely rely on the detection of biomolecules, which highlights the importance of preventing forward contamination not only with viable microorganisms but also with biomolecules that could compromise the validity of life-detection experiments. The designation of DNA as a high-priority biosignature makes it necessary to evaluate its persistence in extraterrestrial environments and the effects of those conditions on its biological activity. We exposed DNA deposited on spacecraft-qualified aluminum coupons to a simulated martian environment for periods ranging from 1 minute to 1 hour and measured its ability to function as a template for replication in a quantitative polymerase chain reaction (qPCR) assay. We found that inactivation of naked DNA or DNA extracted from exposed spores of Bacillus subtilis followed a multiphasic UV-dose response and that a fraction of DNA molecules retained functionality after 60 minutes of exposure to simulated full-spectrum solar radiation in martian atmospheric conditions. The results indicate that forward-contaminant DNA could persist for considerable periods of time at the martian surface.
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Affiliation(s)
- Patricia Fajardo-Cavazos
- Department of Microbiology and Cell Science, University of Florida , Kennedy Space Center, Florida 32899, USA.
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Perkins AE, Schuerger AC, Nicholson WL. Isolation of rpoB mutations causing rifampicin resistance in Bacillus subtilis spores exposed to simulated Martian surface conditions. ASTROBIOLOGY 2008; 8:1159-1167. [PMID: 19191541 DOI: 10.1089/ast.2007.0224] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT Bacterial spores are considered prime candidates for Earth-to-Mars transport by natural processes and human spaceflight activities. Previous studies have shown that exposure of Bacillus subtilis spores to ultrahigh vacuum (UHV) characteristic of space both increased the spontaneous mutation rate and altered the spectrum of mutation in various marker genes; but, to date, mutagenesis studies have not been performed on spores exposed to milder low pressures encountered in the martian environment. Mutations to rifampicin-resistance (Rif(R)) were isolated in B. subtilis spores exposed to simulated martian atmosphere (99.9% CO(2), 710 Pa) for 21 days in a Mars Simulation Chamber (MSC) and compared to parallel Earth controls. Exposure in the MSC reduced spore viability by approximately 67% compared to Earth controls, but this decrease was not statistically significant (P = 0.3321). The frequency of mutation to Rif(R) was also not significantly increased in the MSC compared to Earth-exposed spores (P = 0.479). Forty-two and 51 Rif(R) mutant spores were isolated from the MSC- and Earth-exposed controls, respectively. Nucleotide sequencing located the Rif(R) mutations in the rpoB gene encoding the beta subunit of RNA polymerase at residue V135F of the N-cluster and at residues Q469K/L, H482D/P/R/Y, and S487L in Cluster I. No mutations were found in rpoB Clusters II or III. Two new alleles, Q469L and H482D, previously unreported in B. subtilis rpoB, were isolated from spores exposed in the MSC; otherwise, only slight differences were observed in the spectra of spontaneous Rif(R) mutations from spores exposed to Earth vs. the MSC. However, both spectra are distinctly different from Rif(R) mutations previously reported arising from B. subtilis spores exposed to simulated space vacuum.
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Affiliation(s)
- Amy E Perkins
- Department of Microbiology & Cell Science, University of Florida, Space Life Sciences Laboratory, Kennedy Space Center, FL 32899, USA
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Transcriptome divergence and the loss of plasticity in Bacillus subtilis after 6,000 generations of evolution under relaxed selection for sporulation. J Bacteriol 2008; 191:428-33. [PMID: 18952793 DOI: 10.1128/jb.01234-08] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We used microarrays to identify the causes of sporulation deficiencies in Bacillus subtilis after 6,000 generations of evolution. We found that sporulation loss did not result from large-scale deletions; therefore, it must have resulted from smaller indels and/or substitutions. Transcription patterns of one strain versus its ancestor showed that sporulation was not initiated and suggested that sporulation loss may be part of an overall decline in plasticity.
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Involvement of recQ in the ultraviolet damage repair pathway in Deinococcus radiodurans. Mutat Res 2008; 641:48-53. [PMID: 18343459 DOI: 10.1016/j.mrfmmm.2008.02.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Revised: 10/27/2007] [Accepted: 02/05/2008] [Indexed: 11/23/2022]
Abstract
Deinococcus radiodurans is a bacterium which can survive extremely DNA damage. To investigate the relationship between recQ and the ultraviolet radiation (UV) damage repair pathway, we created a four mutant strain by constructing recQ knockout mutants in uvrA1, uvrA2, and uvsE backgrounds. Using the rpoB/Rif(r) system, we measured the mutation frequencies and rates in wild type, recQ (MQ), uvsE uvrA1 uvrA2 (TNK006), and uvsE uvrA1 uvrA2 recQ (TQ). We then isolated Rif(r) mutants of these strains and sequenced the rpoB gene. The mutation frequency of TQ was 6.4, 10.1, and 2.43 times that of wild type, MQ, and TNK006, respectively, and resulted in rates of 4.7, 6.71, and 2.15 folds higher than that of wild type, MQ, and TNK006, respectively. All the strains demonstrated specific mutational hotspots. Furthermore, the TQ strain showed a transversion bias that was different from the other three strains. The results indicate that recQ is involved in the ultraviolet damage repair pathway via the interaction between recQ and uvrA1, uvrA2, and uvsE in D. radiodurans.
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Perkins AE, Nicholson WL. Uncovering new metabolic capabilities of Bacillus subtilis using phenotype profiling of rifampin-resistant rpoB mutants. J Bacteriol 2007; 190:807-14. [PMID: 17644585 PMCID: PMC2223569 DOI: 10.1128/jb.00901-07] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
RNA polymerase is a central macromolecular machine controlling the flow of information from genotype to phenotype, and insights into global transcriptional regulation can be gained by studying mutational perturbations in the enzyme. Mutations in the RNA polymerase beta subunit gene rpoB causing resistance to rifampin (Rif(r)) in Bacillus subtilis were previously shown to lead to alterations in the expression of a number of global phenotypes known to be under transcriptional control, such as growth, competence for transformation, sporulation, and germination (H. Maughan, B. Galeano, and W. L. Nicholson, J. Bacteriol. 186:2481-2486, 2004). To better understand the global effects of rpoB mutations on metabolism, wild-type and 11 distinct congenic Rif(r) mutant strains of B. subtilis were tested for utilization of 95 substrates by use of Biolog GP2 MicroPlates. A number of alterations of substrate utilization patterns were observed in the Rif(r) mutants, including the utilization of novel substrates previously unknown in B. subtilis, such as gentiobiose, beta-methyl-D-glucoside, and D-psicose. The results indicate that combining global metabolic profiling with mutations in RNA polymerase provides a system-wide approach for uncovering previously unknown metabolic capabilities and further understanding global transcriptional control circuitry in B. subtilis.
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Affiliation(s)
- Amy E Perkins
- Department of Microbiology and Cell Science, University of Florida, Kennedy Space Center, Florida 32899, USA
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Maughan H, Callicotte V, Hancock A, Birky CW, Nicholson WL, Masel J. THE POPULATION GENETICS OF PHENOTYPIC DETERIORATION IN EXPERIMENTAL POPULATIONS OF BACILLUS SUBTILIS. Evolution 2006. [DOI: 10.1111/j.0014-3820.2006.tb01148.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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38
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Maughan H, Callicotte V, Hancock A, Birky CW, Nicholson WL, Masel J. THE POPULATION GENETICS OF PHENOTYPIC DETERIORATION IN EXPERIMENTAL POPULATIONS OF BACILLUS SUBTILIS. Evolution 2006. [DOI: 10.1554/05-370.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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39
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Maughan H, Galeano B, Nicholson WL. Novel rpoB mutations conferring rifampin resistance on Bacillus subtilis: global effects on growth, competence, sporulation, and germination. J Bacteriol 2004; 186:2481-6. [PMID: 15060052 PMCID: PMC412138 DOI: 10.1128/jb.186.8.2481-2486.2004] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, spontaneous rifampin resistance mutations were isolated in cluster I of the rpoB gene, resulting in amino acid replacements (Q469R, H482R, H482Y, or S487L) in the Bacillus subtilis RNA polymerase beta subunit (W. L. Nicholson and H. Maughan, J. Bacteriol. 184:4936-4940, 2002). In this study, each amino acid change in the beta subunit was observed to result in its own unique spectrum of effects on growth and various developmental events, including sporulation, germination, and competence for transformation. The results thus establish the important role played by the RNA polymerase beta subunit, not only in the catalytic aspect of transcription, but also in the regulation of major developmental events in B. subtilis.
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Affiliation(s)
- Heather Maughan
- Departments of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA
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40
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Sasaki M, Kurusu Y. Analysis of spontaneous base substitutions generated in mutator strains ofBacillus subtilis. FEMS Microbiol Lett 2004. [DOI: 10.1111/j.1574-6968.2004.tb09510.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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Inaoka T, Takahashi K, Yada H, Yoshida M, Ochi K. RNA polymerase mutation activates the production of a dormant antibiotic 3,3'-neotrehalosadiamine via an autoinduction mechanism in Bacillus subtilis. J Biol Chem 2003; 279:3885-92. [PMID: 14612444 DOI: 10.1074/jbc.m309925200] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacillus and Streptomyces species possess the ability to produce a variety of commercially important metabolites and extracellular enzymes. We previously demonstrated that antibiotic production in Streptomyces coeli-color A3(2) and Streptomyces lividans can be enhanced by RNA polymerase (RNAP) mutations selected for the rifampicin-resistant (Rif(r)) phenotype. Here, we have shown that the introduction of a certain Rif(r) rpoB mutation into a B. subtilis strain resulted in cells that overproduce an aminosugar antibiotic 3,3'-neotrehalosadiamine (NTD), the production of which is dormant in the wild-type strain. Mutational and recombinant gene expression analyses have revealed a polycistronic gene ntdABC (formally yhjLKJ) and a monocistronic gene ntdR (formally yhjM) as the NTD biosynthesis operon and a positive regulator for ntdABC, respectively. Analysis of transcriptional fusions to a lacZ reporter revealed that NTD acts as an autoinducer for its own biosynthesis genes via NtdR protein. Our results also showed that the Rif(r) rpoB mutation causes an increase in the activity of sigma(A)-dependent promoters including ntdABC promoter. Therefore, we propose that unlike the wild-type RNAP, the mutant RNAP efficiently recognized the sigma(A)-dependent promoters, resulting in the dramatic activation of the NTD biosynthesis pathway by an autoinduction mechanism.
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Affiliation(s)
- Takashi Inaoka
- Microbial Function Laboratory and Molecular Elucidation Laboratory, National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan
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Ko KS, Kim JM, Kim JW, Jung BY, Kim W, Kim IJ, Kook YH. Identification of Bacillus anthracis by rpoB sequence analysis and multiplex PCR. J Clin Microbiol 2003; 41:2908-14. [PMID: 12843020 PMCID: PMC165277 DOI: 10.1128/jcm.41.7.2908-2914.2003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Comparative sequence analysis was performed upon Bacillus anthracis and its closest relatives, B. cereus and B. thuringiensis. Portions of rpoB DNA from 10 strains of B. anthracis, 16 of B. cereus, 10 of B. thuringiensis, 1 of B. mycoides, and 1 of B. megaterium were amplified and sequenced. The determined rpoB sequences (318 bp) of the 10 B. anthracis strains, including five Korean isolates, were identical to those of Ames, Florida, Kruger B, and Western NA strains. Strains of the "B. cereus group" were separated into two subgroups, in which the B. anthracis strains formed a separate clade in the phylogenetic tree. However, B. cereus and B. thuringiensis could not be differentiated. Sequence analysis confirmed the five Korean isolates as B. anthracis. Based on the rpoB sequences determined in the present study, multiplex PCR generating either B. anthracis-specific amplicons (359 and 208 bp) or cap DNA (291 bp) in a virulence plasmid could be used for the rapid differential detection and identification of virulent B. anthracis.
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Affiliation(s)
- Kwan Soo Ko
- Department of Microbiology and Cancer Research Institute, Institute of Endemic Diseases, SNUMRC, Seoul National University College of Medicine, Seoul National University Hospital, Seoul 110-799, Korea
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Benardini JN, Sawyer J, Venkateswaran K, Nicholson WL. Spore UV and acceleration resistance of endolithic Bacillus pumilus and Bacillus subtilis isolates obtained from Sonoran desert basalt: implications for lithopanspermia. ASTROBIOLOGY 2003; 3:709-717. [PMID: 14987476 DOI: 10.1089/153110703322736033] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bacterial spores have been used as model systems for studying the theory of interplanetary transport of life by natural processes such as asteroidal or cometary impacts (i.e., lithopanspermia). Because current spallation theory predicts that near-surface rocks are ideal candidates for planetary ejection and surface basalts are widely distributed throughout the rocky planets, we isolated spore-forming bacteria from the interior of near-subsurface basalt rocks collected in the Sonoran desert near Tucson, Arizona. Spores were found to inhabit basalt at very low concentrations (</=28 colony-forming units/g) in these samples. Six isolates identified as being most closely related to Bacillus pumilus and one Bacillus subtilis isolate were recovered from near-subsurface basalt samples. Populations of purified spores prepared from the isolated strains were subjected to 254-nm UV and ballistics tests in order to assess their resistance to UV radiation and to extreme acceleration shock, two proposed lethal factors for spores during interplanetary transfer. Specific natural isolates of B. pumilus were found to be substantially more resistant to UV and extreme acceleration than were reference laboratory strains of B. subtilis, the benchmark organism, suggesting that spores of environmental B. pumilus isolates may be more likely to survive the rigors of interplanetary transfer.
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Affiliation(s)
- James N Benardini
- Department of Veterinary Science and Microbiology, University of Arizona, Tucson, Arizona, USA
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