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Monselise EBI, Vyazmensky M, Scherf T, Batushansky A, Fishov I. D-Glutamate production by stressed Escherichia coli gives a clue for the hypothetical induction mechanism of the ALS disease. Sci Rep 2024; 14:18247. [PMID: 39107374 PMCID: PMC11303787 DOI: 10.1038/s41598-024-68645-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 07/25/2024] [Indexed: 08/10/2024] Open
Abstract
In the search for the origin of Amyotrophic Lateral Sclerosis disease (ALS), we hypothesized earlier (Monselise, 2019) that D-amino acids produced by stressed microbiome may serve as inducers of the disease development. Many examples of D-amino acid accumulation under various stress conditions were demonstrated in prokaryotic and eukaryotic cells. In this work, wild-type Escherichia coli, members of the digestive system, were subjected to carbon and nitrogen starvation stress. Using NMR and LC-MS techniques, we found for the first time that D-glutamate accumulated in the stressed bacteria but not in control cells. These results together with the existing knowledge, allow us to suggest a new insight into the pathway of ALS development: D-glutamate, produced by the stressed microbiome, induces neurobiochemical miscommunication setting on C1q of the complement system. Proving this insight may have great importance in preventive medicine of such MND modern-age diseases as ALS, Alzheimer, and Parkinson.
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Affiliation(s)
- Edna Ben-Izhak Monselise
- Department of Life Science, Bergman Campus, Ben-Gurion University of the Negev, 8441901, Beer-Sheva, Israel.
| | - Maria Vyazmensky
- Department of Life Science, Bergman Campus, Ben-Gurion University of the Negev, 8441901, Beer-Sheva, Israel
| | - Tali Scherf
- Department of Chemical Research Support, The Weizmann Institute of Science, 7610001, Rehovot, Israel
| | - Albert Batushansky
- Ilse Katz Institute for Nanoscale Science & Technology, Marcus Campus, Ben-Gurion University of the Negev, 8410501, Beer-Sheva, Israel
| | - Itzhak Fishov
- Department of Life Science, Bergman Campus, Ben-Gurion University of the Negev, 8441901, Beer-Sheva, Israel.
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2
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Benn JS, Nunez CM, Blue-McLendon A, Chaki SP, Ficht TA, Rice-Ficht AC, Cook WE. LETHAL TOXIN NEUTRALIZING ANTIBODY RESPONSE INDUCED FOLLOWING ORAL VACCINATION WITH A MICROENCAPSULATED BACILLUS ANTHRACIS STERNE STRAIN 34F2 VACCINE PROOF-OF-CONCEPT STUDY IN WHITE-TAILED DEER ( ODOCOILEUS VIRGINIANUS). J Zoo Wildl Med 2024; 55:212-218. [PMID: 38453505 DOI: 10.1638/2023-0065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2023] [Indexed: 03/09/2024] Open
Abstract
Improved methods are needed to prevent wildlife deaths from anthrax. Caused by Bacillus anthracis, naturally occurring outbreaks of anthrax are frequent but unpredictable. The commercially available veterinary vaccine is labeled for subcutaneous injection and is impractical for large-scale wildlife vaccination programs; therefore, oral vaccination is the most realistic method to control and prevent these outbreaks. We reported the induction of an anthrax-specific lethal toxin (LeTx) neutralizing antibody response in mice following oral vaccination with alginate microcapsules containing B. anthracis Sterne strain 34F2 spores, coated with poly-L-lysine (PLL) and vitelline protein B (VpB). We continued evaluating our novel vaccine formulation through this proof-of-concept study in white-tailed deer (WTD; Odocoileus virginianus; n = 9). We orally vaccinated WTD via needle-free syringe with three formulations of the encapsulated vaccine: 1) PLL-VpB-coated microcapsules with 107-8 spores/ml (n = 5), 2) PLL-VpB-coated microcapsules with 109-10 spores/ml (n = 2), and 3) PLL-coated microcapsules with 109-10 spores/ml (n = 2). Although the limited sample sizes require continued experimentation, we observed an anthrax-specific antibody response in WTD serum following oral vaccination with PLL-coated microcapsules containing 109 spores/ ml. Furthermore, this antibody response neutralized anthrax LeTx in vitro, suggesting that continued development of this vaccine may allow for realistic wildlife anthrax vaccination programs.
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Affiliation(s)
- Jamie S Benn
- Cook Wildlife Lab, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA,
| | - Chase M Nunez
- Cook Wildlife Lab, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA,
| | - Alice Blue-McLendon
- The Winnie Carter Wildlife Center, Department of Veterinary Pharmacology and Physiology, Texas A&M University, College Station, TX 77843, USA
| | - Sankar P Chaki
- The Global Health Research Complex, Division of Research, Texas A&M University, College Station, TX 77843, USA
| | - Thomas A Ficht
- Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77843, USA
| | - Allison C Rice-Ficht
- Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77843, USA
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843, USA
| | - Walter E Cook
- Cook Wildlife Lab, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA
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3
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Caldwell M, Hughes M, Wei F, Ngo C, Pascua R, Pugazhendhi AS, Coathup MJ. Promising applications of D-amino acids in periprosthetic joint infection. Bone Res 2023; 11:14. [PMID: 36894568 PMCID: PMC9998894 DOI: 10.1038/s41413-023-00254-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/02/2023] [Accepted: 02/10/2023] [Indexed: 03/11/2023] Open
Abstract
Due to the rise in our aging population, a disproportionate demand for total joint arthroplasty (TJA) in the elderly is forecast. Periprosthetic joint infection (PJI) represents one of the most challenging complications that can occur following TJA, and as the number of primary and revision TJAs continues to rise, an increasing PJI burden is projected. Despite advances in operating room sterility, antiseptic protocols, and surgical techniques, approaches to prevent and treat PJI remain difficult, primarily due to the formation of microbial biofilms. This difficulty motivates researchers to continue searching for an effective antimicrobial strategy. The dextrorotatory-isoforms of amino acids (D-AAs) are essential components of peptidoglycan within the bacterial cell wall, providing strength and structural integrity in a diverse range of species. Among many tasks, D-AAs regulate cell morphology, spore germination, and bacterial survival, evasion, subversion, and adhesion in the host immune system. When administered exogenously, accumulating data have demonstrated that D-AAs play a pivotal role against bacterial adhesion to abiotic surfaces and subsequent biofilm formation; furthermore, D-AAs have substantial efficacy in promoting biofilm disassembly. This presents D-AAs as promising and novel targets for future therapeutic approaches. Despite their emerging antibacterial efficacy, their role in disrupting PJI biofilm formation, the disassembly of established TJA biofilm, and the host bone tissue response remains largely unexplored. This review aims to examine the role of D-AAs in the context of TJAs. Data to date suggest that D-AA bioengineering may serve as a promising future strategy in the prevention and treatment of PJI.
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Affiliation(s)
- Matthew Caldwell
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Megan Hughes
- School of Biosciences, Cardiff University, CF10 3AT, Wales, UK
| | - Fei Wei
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Christopher Ngo
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Raven Pascua
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Abinaya Sindu Pugazhendhi
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Melanie J Coathup
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA.
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4
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Brogna C, Costanzo V, Brogna B, Bisaccia DR, Brogna G, Giuliano M, Montano L, Viduto V, Cristoni S, Fabrowski M, Piscopo M. Analysis of Bacteriophage Behavior of a Human RNA Virus, SARS-CoV-2, through the Integrated Approach of Immunofluorescence Microscopy, Proteomics and D-Amino Acid Quantification. Int J Mol Sci 2023; 24:3929. [PMID: 36835341 PMCID: PMC9965620 DOI: 10.3390/ijms24043929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/08/2023] [Accepted: 02/11/2023] [Indexed: 02/18/2023] Open
Abstract
SARS-CoV-2, one of the human RNA viruses, is widely studied around the world. Significant efforts have been made to understand its molecular mechanisms of action and how it interacts with epithelial cells and the human microbiome since it has also been observed in gut microbiome bacteria. Many studies emphasize the importance of surface immunity and also that the mucosal system is critical in the interaction of the pathogen with the cells of the oral, nasal, pharyngeal, and intestinal epithelium. Recent studies have shown how bacteria in the human gut microbiome produce toxins capable of altering the classical mechanisms of interaction of viruses with surface cells. This paper presents a simple approach to highlight the initial behavior of a novel pathogen, SARS-CoV-2, on the human microbiome. The immunofluorescence microscopy technique can be combined with spectral counting performed at mass spectrometry of viral peptides in bacterial cultures, along with identification of the presence of D-amino acids within viral peptides in bacterial cultures and in patients' blood. This approach makes it possible to establish the possible expression or increase of viral RNA viruses in general and SARS-CoV-2, as discussed in this study, and to determine whether or not the microbiome is involved in the pathogenetic mechanisms of the viruses. This novel combined approach can provide information more rapidly, avoiding the biases of virological diagnosis and identifying whether a virus can interact with, bind to, and infect bacteria and epithelial cells. Understanding whether some viruses have bacteriophagic behavior allows vaccine therapies to be focused either toward certain toxins produced by bacteria in the microbiome or toward finding inert or symbiotic viral mutations with the human microbiome. This new knowledge opens a scenario on a possible future vaccine: the probiotics vaccine, engineered with the right resistance to viruses that attach to both the epithelium human surface and gut microbiome bacteria.
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Affiliation(s)
- Carlo Brogna
- Department of Research, Craniomed Group Facility Srl., 20091 Bresso, Italy
| | - Vincenzo Costanzo
- Biogem, Institute of Molecular Biology and Genetics, 83031 Ariano Irpino, Italy
| | - Barbara Brogna
- Department of Radiology, Moscati Hospital, Contrada Amoretta, 83100 Avellino, Italy
| | | | - Giancarlo Brogna
- Department of Research, Craniomed Group Facility Srl., 20091 Bresso, Italy
| | - Marino Giuliano
- Marsanconsulting Srl. Public Health Company, Via dei Fiorentini, 80133 Napoli, Italy
| | - Luigi Montano
- Andrology Unit and Service of LifeStyle Medicine in Uro-Andrology, Local Health Authority (ASL), 84124 Salerno, Italy
| | - Valentina Viduto
- Long COVID-19 Foundation, Brookfield Court, Garforth, Leeds LS25 1NB, UK
| | | | - Mark Fabrowski
- Department of Emergency Medicine, Royal Sussex County Hospital, University Hospitals Sussex, Eastern Road, Brighton BN2 5BE, UK
| | - Marina Piscopo
- Department of Biology, University of Naples Federico II, 80126 Napoli, Italy
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Sundaresan A, Le Ngoc M, Wew MU, Ramkumar V, Raninga P, Sum R, Cheong I. A design of experiments screen reveals that Clostridium novyi-NT spore germinant sensing is stereoflexible for valine and its analogs. Commun Biol 2023; 6:118. [PMID: 36709236 PMCID: PMC9884283 DOI: 10.1038/s42003-023-04496-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 01/17/2023] [Indexed: 01/30/2023] Open
Abstract
Although Clostridium novyi-NT is an anti-cancer bacterial therapeutic which germinates within hypoxic tumors to kill cancer cells, the actual germination triggers for C. novyi-NT are still unknown. In this study, we screen candidate germinants using combinatorial experimental designs and discover by serendipity that D-valine is a potent germinant, inducing 50% spore germination at 4.2 mM concentration. Further investigation revealed that five D-valine analogs are also germinants and four of these analogs are enantiomeric pairs. This stereoflexible effect of L- and D-amino acids shows that spore germination is a complex process where enantiomeric interactions can be confounders. This study also identifies L-cysteine as a germinant, and hypoxanthine and inosine as co-germinants. Several other amino acids promote (L-valine, L-histidine, L-threonine and L-alanine) or inhibit (L-arginine, L-glycine, L-lysine, L-tryptophan) germination in an interaction-dependent manner. D-alanine inhibits all germination, even in complex growth media. This work lays the foundation for improving the germination efficacy of C. novyi-NT spores in tumors.
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Affiliation(s)
- Ajitha Sundaresan
- grid.226688.00000 0004 0620 9198Temasek Life Sciences Laboratory, Singapore, Singapore ,grid.4280.e0000 0001 2180 6431Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Mai Le Ngoc
- grid.4280.e0000 0001 2180 6431NUS High School of Mathematics and Sciences, Singapore, Singapore
| | - Marvell Ung Wew
- grid.4280.e0000 0001 2180 6431NUS High School of Mathematics and Sciences, Singapore, Singapore
| | - Varsha Ramkumar
- grid.4280.e0000 0001 2180 6431NUS High School of Mathematics and Sciences, Singapore, Singapore
| | - Prahlad Raninga
- grid.226688.00000 0004 0620 9198Temasek Life Sciences Laboratory, Singapore, Singapore
| | - Rongji Sum
- grid.226688.00000 0004 0620 9198Temasek Life Sciences Laboratory, Singapore, Singapore ,grid.4280.e0000 0001 2180 6431Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Ian Cheong
- grid.226688.00000 0004 0620 9198Temasek Life Sciences Laboratory, Singapore, Singapore ,grid.4280.e0000 0001 2180 6431Department of Biological Sciences, National University of Singapore, Singapore, Singapore
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6
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Spore-Associated Proteins Involved in c-di-GMP Synthesis and Degradation of Bacillus anthracis. J Bacteriol 2021; 203:e0013521. [PMID: 34096779 DOI: 10.1128/jb.00135-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Bis-(3'-5')-cyclic-dimeric GMP (c-di-GMP) is an important bacterial regulatory signaling molecule affecting biofilm formation, toxin production, motility, and virulence. The genome of Bacillus anthracis, the causative agent of anthrax, is predicted to encode ten putative GGDEF/EAL/HD-GYP-domain containing proteins. Heterologous expression in Bacillus subtilis hosts indicated that there are five active GGDEF domain-containing proteins and four active EAL or HD-GYP domain-containing proteins. Using an mCherry gene fusion-Western blotting approach, the expression of the c-di-GMP-associated proteins was observed throughout the in vitro life cycle. Of the six c-di-GMP-associated proteins found to be present in sporulating cells, four (CdgA, CdgB, CdgD, and CdgG) contain active GGDEF domains. The six proteins expressed in sporulating cells are retained in spores in a CotE-independent manner and thus are not likely to be localized to the exosporium layer of the spores. Individual deletion mutations involving the nine GGDEF/EAL protein-encoding genes and one HD-GYP protein-encoding gene did not affect sporulation efficiency, the attachment of the exosporium glycoprotein BclA, or biofilm production. Notably, expression of anthrax toxin was not affected by deletion of any of the cdg determinants. Three determinants encoding proteins with active GGDEF domains were found to affect germination kinetics. This study reveals a spore association of cyclic-di-GMP regulatory proteins and a likely role for these proteins in the biology of the B. anthracis spore. IMPORTANCE The genus Bacillus is composed of Gram-positive, rod shaped, soil-dwelling bacteria. As a mechanism for survival in the harsh conditions in soil, the organisms undergo sporulation, and the resulting spores permit the organisms to survive harsh environmental conditions. Although most species are saprophytes, Bacillus cereus and Bacillus anthracis are human pathogens and Bacillus thuringiensis is an insect pathogen. The bacterial c-di-GMP regulatory system is an important control system affecting motility, biofilm formation, and toxin production. The role of c-di-GMP has been studied in the spore-forming bacilli Bacillus subtilis, Bacillus amyloliquefaciens, B. cereus, and B. thuringiensis. However, this regulatory system has not heretofore been examined in the high-consequence zoonotic pathogen of this genus, B. anthracis.
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Omadacycline compared to vancomycin when combined with germinants to disrupt the life cycle of Clostridioides difficile. Antimicrob Agents Chemother 2021; 65:AAC.01431-20. [PMID: 33649111 PMCID: PMC8092874 DOI: 10.1128/aac.01431-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Clostridioides difficile (C. difficile) infections (CDI) are commonly treated with antibiotics that do not impact the dormant spore form of the pathogen. CDI-directed antibiotics, such as vancomycin and metronidazole, can destroy the vegetative form of C. difficile and protective microbiota. After treatment, spores can germinate into vegetative cells causing clinical disease relapse and further spore shedding. This in vitro study compares the combination of germinants with vancomycin or omadacycline to antibiotics alone in eradicating C. difficile spores and vegetative cells. Among the four strains in this study, omadacycline minimum inhibitory concentrations (0.031-0.125 mg/L) were lower than vancomycin (1-4 mg/L). Omadacycline nor vancomycin in media alone reduced spore counts. In three of the four strains, including the epidemic ribotype 027, spore eradication with germinants was 94.8-97.4% with vancomycin and 99.4-99.8% with omadacycline (p<0.005). In ribotype 012, either antibiotic combined with germinants resulted in 100% spore eradication at 24 hours. The addition of germinants with either antibiotic did not result in significant toxin A or B production, which were below the limit of detection (<1.25 ng/mL) by 48 hours. Limiting the number of spores present in patient GI tracts at the end of therapy may be effective at preventing recurrent CDI and limiting spore shedding in the healthcare environment. These results with germinants warrant safety and efficacy evaluations in animal models.
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Miyamoto T, Homma H, Miyamoto T. D-Amino acid metabolism in bacteria. J Biochem 2021; 170:5-13. [PMID: 33788945 DOI: 10.1093/jb/mvab043] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 03/19/2021] [Indexed: 02/02/2023] Open
Affiliation(s)
- Tetsuya Miyamoto
- Graduate School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Hiroshi Homma
- Graduate School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Tetsuya Miyamoto
- Graduate School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
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9
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Norris MH, Kirpich A, Bluhm AP, Zincke D, Hadfield T, Ponciano JM, Blackburn JK. Convergent evolution of diverse Bacillus anthracis outbreak strains toward altered surface oligosaccharides that modulate anthrax pathogenesis. PLoS Biol 2020; 18:e3001052. [PMID: 33370274 PMCID: PMC7793302 DOI: 10.1371/journal.pbio.3001052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 01/08/2021] [Accepted: 12/14/2020] [Indexed: 11/19/2022] Open
Abstract
Bacillus anthracis, a spore-forming gram-positive bacterium, causes anthrax. The external surface of the exosporium is coated with glycosylated proteins. The sugar additions are capped with the unique monosaccharide anthrose. The West African Group (WAG) B. anthracis have mutations rendering them anthrose deficient. Through genome sequencing, we identified 2 different large chromosomal deletions within the anthrose biosynthetic operon of B. anthracis strains from Chile and Poland. In silico analysis identified an anthrose-deficient strain in the anthrax outbreak among European heroin users. Anthrose-deficient strains are no longer restricted to West Africa so the role of anthrose in physiology and pathogenesis was investigated in B. anthracis Sterne. Loss of anthrose delayed spore germination and enhanced sporulation. Spores without anthrose were phagocytized at higher rates than spores with anthrose, indicating that anthrose may serve an antiphagocytic function on the spore surface. The anthrose mutant had half the LD50 and decreased time to death (TTD) of wild type and complement B. anthracis Sterne in the A/J mouse model. Following infection, anthrose mutant bacteria were more abundant in the spleen, indicating enhanced dissemination of Sterne anthrose mutant. At low sample sizes in the A/J mouse model, the mortality of ΔantC-infected mice challenged by intranasal or subcutaneous routes was 20% greater than wild type. Competitive index (CI) studies indicated that spores without anthrose disseminated to organs more extensively than a complemented mutant. Death process modeling using mouse mortality dynamics suggested that larger sample sizes would lead to significantly higher deaths in anthrose-negative infected animals. The model was tested by infecting Galleria mellonella with spores and confirmed the anthrose mutant was significantly more lethal. Vaccination studies in the A/J mouse model showed that the human vaccine protected against high-dose challenges of the nonencapsulated Sterne-based anthrose mutant. This work begins to identify the physiologic and pathogenic consequences of convergent anthrose mutations in B. anthracis.
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Affiliation(s)
- Michael H. Norris
- Spatial Epidemiology & Ecology Research Laboratory, Department of Geography, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Alexander Kirpich
- Department of Population Health Services, Georgia State University, Atlanta, Georgia, United States of America
| | - Andrew P. Bluhm
- Spatial Epidemiology & Ecology Research Laboratory, Department of Geography, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Diansy Zincke
- Spatial Epidemiology & Ecology Research Laboratory, Department of Geography, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Ted Hadfield
- Spatial Epidemiology & Ecology Research Laboratory, Department of Geography, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Jose Miguel Ponciano
- Department of Biology, University of Florida, Gainesville, Florida, United States of America
| | - Jason K. Blackburn
- Spatial Epidemiology & Ecology Research Laboratory, Department of Geography, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
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10
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Sidiq KR, Chow MW, Zhao Z, Daniel RA. Alanine metabolism in Bacillus subtilis. Mol Microbiol 2020; 115:739-757. [PMID: 33155333 DOI: 10.1111/mmi.14640] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 11/02/2020] [Accepted: 11/03/2020] [Indexed: 12/30/2022]
Abstract
Both isomeric forms of alanine play a crucial role in bacterial growth and viability; the L-isomer of this amino acid is one of the building blocks for protein synthesis, and the D-isomer is incorporated into the bacterial cell wall. Despite a long history of genetic manipulation of Bacillus subtilis using auxotrophic markers, the genes involved in alanine metabolism have not been characterized fully. In this work, we genetically characterized the major enzymes involved in B. subtilis alanine biosynthesis and identified an alanine permease, AlaP (YtnA), which we show has a major role in the assimilation of D-alanine from the environment. Our results provide explanations for the puzzling fact that growth of B. subtilis does not result in the significant accumulation of extracellular D-alanine. Interestingly, we find that in B. subtilis, unlike E. coli where multiple enzymes have a biochemical activity that can generate alanine, the primary synthetic enzyme for alanine is encoded by alaT, although a second gene, dat, can support slow growth of an L-alanine auxotroph. However, our results also show that Dat mediates the synthesis of D-alanine and its activity is influenced by the abundance of L-alanine. This work provides valuable insights into alanine metabolism that suggests that the relative abundance of D- and L-alanine might be linked with cytosolic pool of D and L-glutamate, thereby coupling protein and cell envelope synthesis with the metabolic status of the cell. The results also suggest that, although some of the purified enzymes involved in alanine biosynthesis have been shown to catalyze reversible reactions in vitro, most of them function unidirectionally in vivo.
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Affiliation(s)
- Karzan R Sidiq
- Centre for Bacterial Cell Biology, Biosciences Institute, Medical Faculty, Newcastle University, Newcastle Upon Tyne, UK
| | - Man W Chow
- Centre for Bacterial Cell Biology, Biosciences Institute, Medical Faculty, Newcastle University, Newcastle Upon Tyne, UK
| | - Zhao Zhao
- Centre for Bacterial Cell Biology, Biosciences Institute, Medical Faculty, Newcastle University, Newcastle Upon Tyne, UK
| | - Richard A Daniel
- Centre for Bacterial Cell Biology, Biosciences Institute, Medical Faculty, Newcastle University, Newcastle Upon Tyne, UK
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11
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Lee CJ, Qiu TA, Sweedler JV. d-Alanine: Distribution, origin, physiological relevance, and implications in disease. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2020; 1868:140482. [DOI: 10.1016/j.bbapap.2020.140482] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/19/2020] [Accepted: 06/29/2020] [Indexed: 01/01/2023]
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12
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Cote CK, Weidner JM, Klimko C, Piper AE, Miller JA, Hunter M, Shoe JL, Hoover JC, Sauerbry BR, Buhr T, Bozue JA, Harbourt DE, Glass PJ. Biological Validation of a Chemical Effluent Decontamination System. APPLIED BIOSAFETY 2020. [DOI: 10.1177/1535676020937967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Introduction: Failure of an existing effluent decontamination system (EDS) prompted the consideration of commercial off-the-shelf solutions for decontamination of containment laboratory waste. A bleach-based chemical EDS was purchased to serve as an interim solution. Methods: Studies were conducted in the laboratory to validate inactivation of Bacillus spores with bleach in complex matrices containing organic simulants including fetal bovine serum, humic acid, and animal room sanitation effluent. Results: These studies demonstrated effective decontamination of >106 spores at a free chlorine concentration of ≥5700 parts per million with a 2-hour contact time. Translation of these results to biological validation of the bleach-based chemical EDS required some modifications to the system and its operation. Discussion: The chemical EDS was validated for the treatment of biosafety levels 3 and 4 waste effluent using laboratory-prepared spore packets along with commercial biological indicators; however, several issues and lessons learned identified during the process of onboarding are also discussed, including bleach product source, method of validation, dechlorination, and treated waste disposal.
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Affiliation(s)
- Christopher K. Cote
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Jessica M. Weidner
- Medical Translational Sciences Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Christopher Klimko
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Ashley E. Piper
- Virology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Jeremy A. Miller
- Biosafety Office, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Melissa Hunter
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Jennifer L. Shoe
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Jennifer C. Hoover
- Virology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Brian R. Sauerbry
- Logistics Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Tony Buhr
- Naval Surface Warfare Center, Dahlgren Division, Dahlgren, VA, USA
| | - Joel A. Bozue
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - David E. Harbourt
- Biosafety Office, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
| | - Pamela J. Glass
- Virology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD, USA
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13
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Buhr T, Minter Z, Kennihan N, Young A, Borgers‐Klonkowski E, Osborn E, Bohmke M, Hamilton S, Kimani M, Miller C, Mackie R, Innocenti J, Bensman M, Lilly S. Combining spore germination and heat inactivation to decontaminate materials contaminated with
Bacillus anthracis
spores. J Appl Microbiol 2019; 128:124-137. [DOI: 10.1111/jam.14474] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 09/24/2019] [Accepted: 09/27/2019] [Indexed: 11/26/2022]
Affiliation(s)
- T.L. Buhr
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - Z.A. Minter
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - N.L. Kennihan
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - A.A. Young
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - E.L. Borgers‐Klonkowski
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - E.B. Osborn
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - M.D. Bohmke
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - S.M. Hamilton
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - M.B. Kimani
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - C.T. Miller
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - R.S. Mackie
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - J.M. Innocenti
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - M.D. Bensman
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
| | - S.D. Lilly
- Naval Surface Warfare Center‐Dahlgren Division CBR Concepts and Experimentation Branch (B21) Dahlgren VA USA
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14
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Ehling-Schulz M, Lereclus D, Koehler TM. The Bacillus cereus Group: Bacillus Species with Pathogenic Potential. Microbiol Spectr 2019; 7:10.1128/microbiolspec.gpp3-0032-2018. [PMID: 31111815 PMCID: PMC6530592 DOI: 10.1128/microbiolspec.gpp3-0032-2018] [Citation(s) in RCA: 235] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Indexed: 12/17/2022] Open
Abstract
The Bacillus cereus group includes several Bacillus species with closely related phylogeny. The most well-studied members of the group, B. anthracis, B. cereus, and B. thuringiensis, are known for their pathogenic potential. Here, we present the historical rationale for speciation and discuss shared and unique features of these bacteria. Aspects of cell morphology and physiology, and genome sequence similarity and gene synteny support close evolutionary relationships for these three species. For many strains, distinct differences in virulence factor synthesis provide facile means for species assignment. B. anthracis is the causative agent of anthrax. Some B. cereus strains are commonly recognized as food poisoning agents, but strains can also cause localized wound and eye infections as well as systemic disease. Certain B. thuringiensis strains are entomopathogens and have been commercialized for use as biopesticides, while some strains have been reported to cause infection in immunocompromised individuals. In this article we compare and contrast B. anthracis, B. cereus, and B. thuringiensis, including ecology, cell structure and development, virulence attributes, gene regulation and genetic exchange systems, and experimental models of disease.
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Affiliation(s)
- Monika Ehling-Schulz
- Institute of Microbiology, Department of Pathology, University of Veterinary Medicine, 1210 Vienna, Austria
| | - Didier Lereclus
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
| | - Theresa M Koehler
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center - Houston, Houston, TX 77030
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15
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Kohler LJ, Quirk AV, Welkos SL, Cote CK. Incorporating germination-induction into decontamination strategies for bacterial spores. J Appl Microbiol 2017; 124:2-14. [PMID: 28980459 DOI: 10.1111/jam.13600] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/28/2017] [Accepted: 09/29/2017] [Indexed: 01/05/2023]
Abstract
Bacterial spores resist environmental extremes and protect key spore macromolecules until more supportive conditions arise. Spores germinate upon sensing specific molecules, such as nutrients. Germination is regulated by specialized mechanisms or structural features of the spore that limit contact with germinants and enzymes that regulate germination. Importantly, germination renders spores more susceptible to inactivating processes such as heat, desiccation, and ultraviolet radiation, to which they are normally refractory. Thus, germination can be intentionally induced through a process called germination-induction and subsequent treatment of these germinated spores with common disinfectants or gentle heat will inactivate them. However, while the principle of germination-induction has been shown effective in the laboratory, this strategy has not yet been fully implemented in real-word scenarios. Here, we briefly review the mechanisms of bacterial spore germination and discuss the evolution of germination-induction as a decontamination strategy. Finally, we examine progress towards implementing germination-induction in three contexts: biodefense, hospital settings and food manufacture. SIGNIFICANCE AND IMPACT This article reviews implementation of germination-induction as part of a decontamination strategy for the cleanup of bacterial spores. To our knowledge this is the first time that germination-induction studies have been reviewed in this context. This article will provide a resource which summarizes the mechanisms of germination in Clostridia and Bacillus species, challenges and successes in germination-induction, and potential areas where this strategy may be implemented.
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Affiliation(s)
- L J Kohler
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
| | - A V Quirk
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
| | - S L Welkos
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
| | - C K Cote
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
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16
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Abstract
To survive adverse conditions, some bacterial species are capable of developing into a cell type, the "spore," which exhibits minimal metabolic activity and remains viable in the presence of multiple environmental challenges. For some pathogenic bacteria, this developmental state serves as a means of survival during transmission from one host to another. Spores are the highly infectious form of these bacteria. Upon entrance into a host, specific signals facilitate germination into metabolically active replicating organisms, resulting in disease pathogenesis. In this article, we will review spore structure and function in well-studied pathogens of two genera, Bacillus and Clostridium, focusing on Bacillus anthracis and Clostridium difficile, and explore current data regarding the lifestyles of these bacteria outside the host and transmission from one host to another.
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17
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Shrestha R, Lockless SW, Sorg JA. A Clostridium difficile alanine racemase affects spore germination and accommodates serine as a substrate. J Biol Chem 2017; 292:10735-10742. [PMID: 28487371 DOI: 10.1074/jbc.m117.791749] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 05/07/2017] [Indexed: 12/18/2022] Open
Abstract
Clostridium difficile has become one of the most common bacterial pathogens in hospital-acquired infections in the United States. Although C. difficile is strictly anaerobic, it survives in aerobic environments and transmits between hosts via spores. C. difficile spore germination is triggered in response to certain bile acids and glycine. Although glycine is the most effective co-germinant, other amino acids can substitute with varying efficiencies. Of these, l-alanine is an effective co-germinant and is also a germinant for most bacterial spores. Many endospore-forming bacteria embed alanine racemases into their spore coats, and these enzymes are thought to convert the l-alanine germinant into d-alanine, a spore germination inhibitor. Although the C. difficile Alr2 racemase is the sixth most highly expressed gene during C. difficile spore formation, a previous study reported that Alr2 has little to no role in germination of C. difficile spores in rich medium. Here, we hypothesized that Alr2 could affect C. difficile l-alanine-induced spore germination in a defined medium. We found that alr2 mutant spores more readily germinate in response to l-alanine as a co-germinant. Surprisingly, d-alanine also functioned as a co-germinant. Moreover, we found that Alr2 could interconvert l- and d-serine and that Alr2 bound to l- and d-serine with ∼2-fold weaker affinity to that of l- and d-alanine. Finally, we demonstrate that l- and d-serine are also co-germinants for C. difficile spores. These results suggest that C. difficile spores can respond to a diverse set of amino acid co-germinants and reveal that Alr2 can accommodate serine as a substrate.
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Affiliation(s)
- Ritu Shrestha
- From the Department of Biology, Texas A&M University, College Station, Texas 77843
| | - Steve W Lockless
- From the Department of Biology, Texas A&M University, College Station, Texas 77843
| | - Joseph A Sorg
- From the Department of Biology, Texas A&M University, College Station, Texas 77843
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18
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Mott T, Shoe J, Hunter M, Woodson A, Fritts K, Klimko C, Quirk A, Welkos S, Cote C. Comparison of sampling methods to recover germinatedBacillus anthracisandBacillus thuringiensisendospores from surface coupons. J Appl Microbiol 2017; 122:1219-1232. [DOI: 10.1111/jam.13418] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/03/2017] [Accepted: 02/04/2017] [Indexed: 11/26/2022]
Affiliation(s)
- T.M. Mott
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - J.L. Shoe
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - M. Hunter
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - A.M. Woodson
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - K.A. Fritts
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - C.P. Klimko
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - A.V. Quirk
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - S.L. Welkos
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
| | - C.K. Cote
- Bacteriology Division; United States Army Medical Research Institute of Infectious Disease (USAMRIID); Frederick MD USA
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19
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Warda AK, Xiao Y, Boekhorst J, Wells-Bennik MHJ, Nierop Groot MN, Abee T. Analysis of Germination Capacity and Germinant Receptor (Sub)clusters of Genome-Sequenced Bacillus cereus Environmental Isolates and Model Strains. Appl Environ Microbiol 2017; 83:e02490-16. [PMID: 27881417 PMCID: PMC5288832 DOI: 10.1128/aem.02490-16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Accepted: 11/17/2016] [Indexed: 12/28/2022] Open
Abstract
Spore germination of 17 Bacillus cereus food isolates and reference strains was evaluated using flow cytometry analysis in combination with fluorescent staining at a single-spore level. This approach allowed for rapid collection of germination data under more than 20 conditions, including heat activation of spores, germination in complex media (brain heart infusion [BHI] and tryptone soy broth [TSB]), and exposure to saturating concentrations of single amino acids and the combination of alanine and inosine. Whole-genome sequence comparison revealed a total of 11 clusters of operons encoding germinant receptors (GRs): GerK, GerI, and GerL were present in all strains, whereas GerR, GerS, GerG, GerQ, GerX, GerF, GerW, and GerZ (sub)clusters showed a more diverse presence/absence in different strains. The spores of tested strains displayed high diversity with regard to their sensitivity and responsiveness to selected germinants and heat activation. The two laboratory strains, B. cereus ATCC 14579 and ATCC 10987, and 11 food isolates showed a good germination response under a range of conditions, whereas four other strains (B. cereus B4085, B4086, B4116, and B4153) belonging to phylogenetic group IIIA showed a very weak germination response even in BHI and TSB media. Germination responses could not be linked to specific (combinations of) GRs, but it was noted that the four group IIIA strains contained pseudogenes or variants of subunit C in their gerL cluster. Additionally, two of those strains (B4086 and B4153) carried pseudogenes in the gerK and gerRI (sub)clusters that possibly affected the functionality of these GRs. IMPORTANCE Germination of bacterial spores is a critical step before vegetative growth can resume. Food products may contain nutrient germinants that trigger germination and outgrowth of Bacillus species spores, possibly leading to food spoilage or foodborne illness. Prediction of spore germination behavior is, however, very challenging, especially for spores of natural isolates that tend to show more diverse germination responses than laboratory strains. The approach used has provided information on the genetic diversity in GRs and corresponding subclusters encoded by B. cereus strains, as well as their germination behavior and possible associations with GRs, and it provides a basis for further extension of knowledge on the role of GRs in B. cereus (group member) ecology and transmission to the host.
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Affiliation(s)
- Alicja K Warda
- TI Food and Nutrition, Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University & Research, Wageningen, The Netherlands
- Wageningen Food and Biobased Research, Wageningen, The Netherlands
| | - Yinghua Xiao
- TI Food and Nutrition, Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Jos Boekhorst
- TI Food and Nutrition, Wageningen, The Netherlands
- NIZO Food Research B.V., Ede, The Netherlands
| | - Marjon H J Wells-Bennik
- TI Food and Nutrition, Wageningen, The Netherlands
- NIZO Food Research B.V., Ede, The Netherlands
| | - Masja N Nierop Groot
- TI Food and Nutrition, Wageningen, The Netherlands
- Wageningen Food and Biobased Research, Wageningen, The Netherlands
| | - Tjakko Abee
- TI Food and Nutrition, Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University & Research, Wageningen, The Netherlands
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20
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Abstract
In some Bacillus species, including Bacillus subtilis, the coat is the outermost layer of the spore. In others, such as the Bacillus cereus family, there is an additional layer that envelops the coat, called the exosporium. In the case of Bacillus anthracis, a series of fine hair-like projections, also referred to as a "hairy" nap, extends from the exosporium basal layer. The exact role of the exosporium in B. anthracis, or for any of the Bacillus species possessing this structure, remains unclear. However, it has been assumed that the exosporium would play some role in infection for B. anthracis, because it is the outermost structure of the spore and would make initial contact with host and immune cells during infection. Therefore, the exosporium has been a topic of great interest, and over the past decade much progress has been made to understand its composition, biosynthesis, and potential roles. Several key aspects of this spore structure, however, are still debated and remain undetermined. Although insights have been gained on the interaction of exosporium with the host during infection, the exact role and significance of this complex structure remain to be determined. Furthermore, because the exosporium is a highly antigenic structure, future strategies for the next-generation anthrax vaccine should pursue its inclusion as a component to provide protection against the spore itself during the initial stages of anthrax.
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21
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The Exosporium Layer of Bacterial Spores: a Connection to the Environment and the Infected Host. Microbiol Mol Biol Rev 2016; 79:437-57. [PMID: 26512126 DOI: 10.1128/mmbr.00050-15] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Much of what we know regarding bacterial spore structure and function has been learned from studies of the genetically well-characterized bacterium Bacillus subtilis. Molecular aspects of spore structure, assembly, and function are well defined. However, certain bacteria produce spores with an outer spore layer, the exosporium, which is not present on B. subtilis spores. Our understanding of the composition and biological functions of the exosporium layer is much more limited than that of other aspects of the spore. Because the bacterial spore surface is important for the spore's interactions with the environment, as well as being the site of interaction of the spore with the host's innate immune system in the case of spore-forming bacterial pathogens, the exosporium is worthy of continued investigation. Recent exosporium studies have focused largely on members of the Bacillus cereus family, principally Bacillus anthracis and Bacillus cereus. Our understanding of the composition of the exosporium, the pathway of its assembly, and its role in spore biology is now coming into sharper focus. This review expands on a 2007 review of spore surface layers which provided an excellent conceptual framework of exosporium structure and function (A. O. Henriques and C. P. Moran, Jr., Annu Rev Microbiol 61:555-588, 2007, http://dx.doi.org/10.1146/annurev.micro.61.080706.093224). That review began a process of considering outer spore layers as an integrated, multilayered structure rather than simply regarding the outer spore components as independent parts.
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22
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Animal Models for the Pathogenesis, Treatment, and Prevention of Infection by Bacillus anthracis. Microbiol Spectr 2016; 3:TBS-0001-2012. [PMID: 26104551 DOI: 10.1128/microbiolspec.tbs-0001-2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
This article reviews the characteristics of the major animal models utilized for studies on Bacillus anthracis and highlights their contributions to understanding the pathogenesis and host responses to anthrax and its treatment and prevention. Advantages and drawbacks associated with each model, to include the major models (murine, guinea pig, rabbit, nonhuman primate, and rat), and other less frequently utilized models, are discussed. Although the three principal forms of anthrax are addressed, the main focus of this review is on models for inhalational anthrax. The selection of an animal model for study is often not straightforward and is dependent on the specific aims of the research or test. No single animal species provides complete equivalence to humans; however, each species, when used appropriately, can contribute to a more complete understanding of anthrax and its etiologic agent.
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23
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Milutinović B, Höfling C, Futo M, Scharsack JP, Kurtz J. Infection of Tribolium castaneum with Bacillus thuringiensis: quantification of bacterial replication within cadavers, transmission via cannibalism, and inhibition of spore germination. Appl Environ Microbiol 2015; 81:8135-44. [PMID: 26386058 PMCID: PMC4651099 DOI: 10.1128/aem.02051-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Accepted: 09/14/2015] [Indexed: 12/18/2022] Open
Abstract
Reproduction within a host and transmission to the next host are crucial for the virulence and fitness of pathogens. Nevertheless, basic knowledge about such parameters is often missing from the literature, even for well-studied bacteria, such as Bacillus thuringiensis, an endospore-forming insect pathogen, which infects its hosts via the oral route. To characterize bacterial replication success, we made use of an experimental oral infection system for the red flour beetle Tribolium castaneum and developed a flow cytometric assay for the quantification of both spore ingestion by the individual beetle larvae and the resulting spore load after bacterial replication and resporulation within cadavers. On average, spore numbers increased 460-fold, showing that Bacillus thuringiensis grows and replicates successfully in insect cadavers. By inoculating cadaver-derived spores and spores from bacterial stock cultures into nutrient medium, we next investigated outgrowth characteristics of vegetative cells and found that cadaver-derived bacteria showed reduced growth compared to bacteria from the stock cultures. Interestingly, this reduced growth was a consequence of inhibited spore germination, probably originating from the host and resulting in reduced host mortality in subsequent infections by cadaver-derived spores. Nevertheless, we further showed that Bacillus thuringiensis transmission was possible via larval cannibalism when no other food was offered. These results contribute to our understanding of the ecology of Bacillus thuringiensis as an insect pathogen.
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Affiliation(s)
- Barbara Milutinović
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Christina Höfling
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Momir Futo
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Jörn P Scharsack
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Joachim Kurtz
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
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24
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Bacillus anthracis Overcomes an Amino Acid Auxotrophy by Cleaving Host Serum Proteins. J Bacteriol 2015; 197:2400-11. [PMID: 25962917 DOI: 10.1128/jb.00073-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 04/21/2015] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED Bacteria sustain an infection by acquiring nutrients from the host to support replication. The host sequesters these nutrients as a growth-restricting strategy, a concept termed "nutritional immunity." Historically, the study of nutritional immunity has centered on iron uptake because many bacteria target hemoglobin, an abundant circulating protein, as an iron source. Left unresolved are the mechanisms that bacteria use to attain other nutrients from host sources, including amino acids. We employed a novel medium designed to mimic the chemical composition of human serum, and we show here that Bacillus anthracis, the causative agent of anthrax disease, proteolyzes human hemoglobin to liberate essential amino acids which enhance its growth. This property can be traced to the actions of InhA1, a secreted metalloprotease, and extends to at least three other serum proteins, including serum albumin. The results suggest that we must also consider proteolysis of key host proteins to be a way for bacterial pathogens to attain essential nutrients, and we provide an experimental framework to determine the host and bacterial factors involved in this process. IMPORTANCE The mechanisms by which bacterial pathogens acquire nutrients during infection are poorly understood. Here we used a novel defined medium that approximates the chemical composition of human blood serum, blood serum mimic (BSM), to better model the nutritional environment that pathogens encounter during bacteremia. Removing essential amino acids from BSM revealed that two of the most abundant proteins in blood-hemoglobin and serum albumin-can satiate the amino acid requirement for Bacillus anthracis, the causative agent of anthrax. We further demonstrate that hemoglobin is proteolyzed by the secreted protease InhA1. These studies highlight that common blood proteins can be a nutrient source for bacteria. They also challenge the historical view that hemoglobin is solely an iron source for bacterial pathogens.
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25
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Monselise EBI, Levkovitz A, Kost D. Ultraviolet radiation induces stress in etiolated Landoltia punctata, as evidenced by the presence of alanine, a universal stress signal: a ¹⁵N NMR study. PLANT BIOLOGY (STUTTGART, GERMANY) 2015; 17 Suppl 1:101-107. [PMID: 24889211 DOI: 10.1111/plb.12198] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Accepted: 03/24/2014] [Indexed: 06/03/2023]
Abstract
Analysis with (15) N NMR revealed that alanine, a universal cellular stress signal, accumulates in etiolated duckweed plants exposed to 15-min pulsed UV light, but not in the absence of UV irradiation. The addition of 10 mm vitamin C, a radical scavenger, reduced alanine levels to zero, indicating the involvement of free radicals. Free D-alanine was detected in (15) N NMR analysis of the chiral amino acid content, using D-tartaric acid as solvent. The accumulation of D-alanine under stress conditions presents a new perspective on the biochemical processes taking place in prokaryote and eukaryote cells.
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Affiliation(s)
- E B-I Monselise
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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26
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Omotade TO, Bernhards RC, Klimko CP, Matthews ME, Hill AJ, Hunter MS, Webster WM, Bozue JA, Welkos SL, Cote CK. The impact of inducing germination of Bacillus anthracis and Bacillus thuringiensis spores on potential secondary decontamination strategies. J Appl Microbiol 2014; 117:1614-33. [PMID: 25196092 DOI: 10.1111/jam.12644] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/03/2014] [Accepted: 09/03/2014] [Indexed: 12/22/2022]
Abstract
AIMS Decontamination and remediation of a site contaminated by the accidental or intentional release of fully virulent Bacillus anthracis spores are difficult, costly and potentially damaging to the environment. Development of novel decontamination strategies that have minimal environmental impacts remains a high priority. Although ungerminated spores are amongst the most resilient organisms known, once exposed to germinants, the germinating spores, in some cases, become susceptible to antimicrobial environments. We evaluated the concept that once germinated, B. anthracis spores would be less hazardous and significantly easier to remediate than ungerminated dormant spores. METHODS AND RESULTS Through in vitro germination and sensitivity assays, we demonstrated that upon germination, B. anthracis Ames spores and Bacillus thuringiensis Al Hakam spores (serving as a surrogate for B. anthracis) become susceptible to environmental stressors. The majority of these germinated B. anthracis and B. thuringiensis spores were nonviable after exposure to a defined minimal germination-inducing solution for prolonged periods of time. Additionally, we examined the impact of potential secondary disinfectant strategies including bleach, hydrogen peroxide, formaldehyde and artificial UV-A, UV-B and UV-C radiation, employed after a 60-min germination-induction step. Each secondary disinfectant employs a unique mechanism of killing; as a result, germination-induction strategies are better suited for some secondary disinfectants than others. CONCLUSIONS These results provide evidence that the deployment of an optimal combination strategy of germination-induction/secondary disinfection may be a promising aspect of wide-area decontamination following a B. anthracis contamination event. SIGNIFICANCE AND IMPACT OF THE STUDY By inducing spores to germinate, our data confirm that the resulting cells exhibit sensitivities that can be leveraged when paired with certain decontamination measures. This increased susceptibility could be exploited to devise more efficient and safe decontamination measures and may obviate the need for more stringent methods that are currently in place.
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Affiliation(s)
- T O Omotade
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
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Abstract
Spores of Bacillus species can remain in their dormant and resistant states for years, but exposure to agents such as specific nutrients can cause spores' return to life within minutes in the process of germination. This process requires a number of spore-specific proteins, most of which are in or associated with the inner spore membrane (IM). These proteins include the (i) germinant receptors (GRs) that respond to nutrient germinants, (ii) GerD protein, which is essential for GR-dependent germination, (iii) SpoVA proteins that form a channel in spores' IM through which the spore core's huge depot of dipicolinic acid is released during germination, and (iv) cortex-lytic enzymes (CLEs) that degrade the large peptidoglycan cortex layer, allowing the spore core to take up much water and swell, thus completing spore germination. While much has been learned about nutrient germination, major questions remain unanswered, including the following. (i) How do nutrient germinants penetrate through spores' outer layers to access GRs in the IM? (ii) What happens during the highly variable and often long lag period between the exposure of spores to nutrient germinants and the commitment of spores to germinate? (iii) What do GRs and GerD do, and how do these proteins interact? (iv) What is the structure of the SpoVA channel in spores' IM, and how is this channel gated? (v) What is the precise state of the spore IM, which has a number of novel properties even though its lipid composition is very similar to that of growing cells? (vi) How is CLE activity regulated such that these enzymes act only when germination has been initiated? (vii) And finally, how does the germination of spores of clostridia compare with that of spores of bacilli?
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Azúa I, Goiriena I, Baña Z, Iriberri J, Unanue M. Release and consumption of D-amino acids during growth of marine prokaryotes. MICROBIAL ECOLOGY 2014; 67:1-12. [PMID: 24057323 DOI: 10.1007/s00248-013-0294-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 09/09/2013] [Indexed: 06/02/2023]
Abstract
Analysis of the composition of the marine-dissolved organic matter has highlighted the importance of D-amino acids, whose origin is attributed mainly to the remains of bacterial peptidoglycan released as a result of grazing or viral lysis. However, very few studies have focused on the active release of D-amino acids by bacteria. With this purpose, we measured the concentration of dissolved amino acids in both enantiomeric forms with two levels of complexity: axenic cultures of Vibrio furnissii and Vibrio alginolyticus and microcosms created from marine microbial assemblages (Biscay Bay, Cantabrian Sea) with and without heterotrophic nanoflagellates (HNFs). Axenic cultures showed that only D-Ala was significantly released and accumulated in the medium up to a concentration of 120 nM, probably as a consequence of the rearrangement of peptidoglycan. The marine microbial assemblages showed that only two D-amino acids significantly accumulated in the environment, D-Ala and D-aspartic acid (Asp), in both the absence and presence of HNFs. The D/L ratio increased during the incubation and reached maximum values of 3.0 to 4.3 for Ala and 0.4 to 10.6 for Asp and correlated with prokaryotic and HNF abundance as well as the rate of prokaryotic thymidine and leucine incorporation. Prokaryotes preferentially consumed L-amino acids, but the relative uptake rates of D-Ala significantly increased in the growth phase. These results demonstrate that bacteria can release and consume D-amino acids at high rates during growth, even in the absence of viruses and grazers, highlighting the importance of bacteria as producers of dissolved organic matter (DOM) in the sea.
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Affiliation(s)
- Iñigo Azúa
- Departamento de Inmunología, Microbiología y Parasitología, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV/EHU), Apdo. 644, 48080, Bilbao, Spain,
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Omotade TO, Heffron JD, Klimko CP, Marchand CL, Miller LL, Halasahoris SA, Bozue JA, Welkos SL, Cote CK. D-cycloserine or similar physiochemical compounds may be uniquely suited for use in Bacillus anthracis spore decontamination strategies. J Appl Microbiol 2013; 115:1343-56. [PMID: 23927578 DOI: 10.1111/jam.12322] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 07/18/2013] [Accepted: 07/30/2013] [Indexed: 02/06/2023]
Abstract
AIMS As observed in the aftermath of the anthrax attacks of 2001, decontamination and remediation of a site contaminated by the accidental or intentional release of Bacillus anthracis spores is difficult, costly and potentially damaging to the environment. The identification of novel strategies that neutralize the threat of spores while minimizing environmental damage remains a high priority. We investigated the efficacy of d-cycloserine (DCS), an antibiotic and inhibitor of the spore-associated enzyme (alanine racemase) responsible for converting l-alanine to d-alanine, as a spore germination enhancer and antimicrobial agent. METHODS AND RESULTS We characterized the impact of DCS exposure on both germinating spores and vegetative cells of fully virulent B. anthracis by evaluating spore germination kinetics, determining the minimum inhibitory concentrations (MICs) required to affect growth of the bacteria and performing macrophage viability assays. DCS enhanced germination induced by l-alanine and also efficiently killed the newly germinated spores. Furthermore, DCS proved nontoxic to macrophages at concentrations that provided protection from the killing effects of spores. Similar tests were conducted with Bacillus thuringiensis (subspecies kurstaki and Al Hakam) to determine its potential as a possible surrogate for B. anthracis field trials. Bacillus thuringiensis spores responded in a similar manner to B. anthracis spores when exposed to DCS. CONCLUSIONS These results further support that DCS augments the germination response of spores in the presence of l-alanine but also reveal that DCS is bactericidal towards germinating spores. SIGNIFICANCE AND IMPACT OF THE STUDY DCS (or similar compounds) may be uniquely suited for use as part of decontamination strategies by augmenting the induction of spore germination and then rendering the germinated spores nonviable.
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Affiliation(s)
- T O Omotade
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
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Gutting BW, Nichols TL, Channel SR, Gearhart JM, Andrews GA, Berger AE, Mackie RS, Watson BJ, Taft SC, Overheim KA, Sherwood RL. Inhalational anthrax (Ames aerosol) in naïve and vaccinated New Zealand rabbits: characterizing the spread of bacteria from lung deposition to bacteremia. Front Cell Infect Microbiol 2012; 2:87. [PMID: 22919678 PMCID: PMC3417635 DOI: 10.3389/fcimb.2012.00087] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 06/06/2012] [Indexed: 12/21/2022] Open
Abstract
There is a need to better understand inhalational anthrax in relevant animal models. This understanding could aid risk assessment, help define therapeutic windows, and provide a better understanding of disease. The aim here was to characterize and quantify bacterial deposition and dissemination in rabbits following exposure to single high aerosol dose (> 100 LD50) of Bacillus anthracis (Ames) spores immediately following exposure through 36 h. The primary goal of collecting the data was to support investigators in developing computational models of inhalational anthrax disease. Rabbits were vaccinated prior to exposure with the human vaccine (Anthrax Vaccine Adsorbed, AVA) or were sham-vaccinated, and were then exposed in pairs (one sham and one AVA) so disease kinetics could be characterized in equally-dosed hosts where one group is fully protected and is able to clear the infection (AVA-vaccinated), while the other is susceptible to disease, in which case the bacteria are able to escape containment and replicate uncontrolled (sham-vaccinated rabbits). Between 4–5% of the presented aerosol dose was retained in the lung of sham- and AVA-vaccinated rabbits as measured by dilution plate analysis of homogenized lung tissue or bronchoalveolar lavage (BAL) fluid. After 6 and 36 h, >80% and >96%, respectively, of the deposited spores were no longer detected in BAL, with no detectable difference between sham- or AVA-vaccinated rabbits. Thereafter, differences between the two groups became noticeable. In sham-vaccinated rabbits the bacteria were detected in the tracheobronchial lymph nodes (TBLN) 12 h post-exposure and in the circulation at 24 h, a time point which was also associated with dramatic increases in vegetative CFU in the lung tissue of some animals. In all sham-vaccinated rabbits, bacteria increased in both TBLN and blood through 36 h at which point in time some rabbits succumbed to disease. In contrast, AVA-vaccinated rabbits showed small numbers of CFU in TBLN between 24 and 36 h post-exposure with small numbers of bacteria in the circulation only at 24 h post-exposure. These results characterize and quantify disease progression in naïve rabbits following aerosol administration of Ames spores which may be useful in a number of different research applications, including developing quantitative models of infection for use in human inhalational anthrax risk assessment.
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Impact of spores on the comparative efficacies of five antibiotics for treatment of Bacillus anthracis in an in vitro hollow fiber pharmacodynamic model. Antimicrob Agents Chemother 2011; 56:1229-39. [PMID: 22155821 DOI: 10.1128/aac.01109-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus anthracis, the bacterium that causes anthrax, is an agent of bioterrorism. The most effective antimicrobial therapy for B. anthracis infections is unknown. An in vitro pharmacodynamic model of B. anthracis was used to compare the efficacies of simulated clinically prescribed regimens of moxifloxacin, linezolid, and meropenem with the "gold standards," doxycycline and ciprofloxacin. Treatment outcomes for isogenic spore-forming and non-spore-forming strains of B. anthracis were compared. Against spore-forming B. anthracis, ciprofloxacin, moxifloxacin, linezolid, and meropenem reduced the B. anthracis population by 4 log(10) CFU/ml over 10 days. Doxycycline reduced the population of this B. anthracis strain by 5 log(10) CFU/ml (analysis of variance [ANOVA] P = 0.01 versus other drugs). Against an isogenic non-spore-forming strain, meropenem killed the vegetative B. anthracis the fastest, followed by moxifloxacin and ciprofloxacin and then doxycycline. Linezolid offered the lowest bacterial kill rate. Heat shock studies using the spore-producing B. anthracis strain showed that with moxifloxacin, ciprofloxacin, and meropenem therapies the total population was mostly spores, while the population was primarily vegetative bacteria with linezolid and doxycycline therapies. Spores have a profound impact on the rate and extent of killing of B. anthracis. Against spore-forming B. anthracis, the five antibiotics killed the total (spore and vegetative) bacterial population at similar rates (within 1 log(10) CFU/ml of each other). However, bactericidal antibiotics killed vegetative B. anthracis faster than bacteriostatic drugs. Since only vegetative-phase B. anthracis produces the toxins that may kill the infected host, the rate and mechanism of killing of an antibiotic may determine its overall in vivo efficacy. Further studies are needed to examine this important observation.
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Cote CK, Welkos SL, Bozue J. Key aspects of the molecular and cellular basis of inhalational anthrax. Microbes Infect 2011; 13:1146-55. [DOI: 10.1016/j.micinf.2011.07.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 07/05/2011] [Accepted: 07/07/2011] [Indexed: 01/25/2023]
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Yang WW, Ponce A. Validation of a Clostridium endospore viability assay and analysis of Greenland ices and Atacama Desert soils. Appl Environ Microbiol 2011; 77:2352-8. [PMID: 21296951 PMCID: PMC3067429 DOI: 10.1128/aem.01966-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 01/01/2011] [Indexed: 11/20/2022] Open
Abstract
A microscopy-based endospore viability assay (micro-EVA) capable of enumerating germinable Clostridium endospores (GCEs) in less than 30 min has been validated and employed to determine GCE concentrations in Greenland ices and Atacama Desert soils. Inoculation onto agarose doped with Tb(3+) and d-alanine triggers Clostridium spore germination and the concomitant release of ∼10(8) molecules of dipicolinic acid (DPA) per endospore, which, under pulsed UV excitation, enables enumeration of resultant green Tb(3+)-DPA luminescent spots as GCEs with time-gated luminescence microscopy. The intensity time courses of the luminescent spots were characteristic of stage I Clostridium spore germination dynamics. Micro-EVA was validated against traditional CFU cultivation from 0 to 1,000 total endospores/ml (i.e., phase-bright bodies/ml), yielding 56.4% ± 1.5% GCEs and 43.0% ± 1.0% CFU. We also show that d-alanine serves as a Clostridium-specific germinant (three species tested) that inhibits Bacillus germination of spores (five species tested) in that endospore concentration regime. Finally, GCE concentrations in Greenland ice cores and Atacama Desert soils were determined with micro-EVA, yielding 1 to 2 GCEs/ml of Greenland ice (versus <1 CFU/ml after 6 months of incubation) and 66 to 157 GCEs/g of Atacama Desert soil (versus 40 CFU/g soil).
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Affiliation(s)
- Wan-Wan Yang
- California Institute of Technology, Jet Propulsion Laboratory, Pasadena, California
| | - Adrian Ponce
- California Institute of Technology, Jet Propulsion Laboratory, Pasadena, California
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Bacillus anthracis spore interactions with mammalian cells: relationship between germination state and the outcome of in vitro. BMC Microbiol 2011; 11:46. [PMID: 21356113 PMCID: PMC3060849 DOI: 10.1186/1471-2180-11-46] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 02/28/2011] [Indexed: 11/10/2022] Open
Abstract
Background During inhalational anthrax, internalization of Bacillus anthracis spores by host cells within the lung is believed to be a key step for initiating the transition from the localized to disseminated stages of infection. Despite compelling in vivo evidence that spores remain dormant within the bronchioalveolar spaces of the lungs, and germinate only after uptake into host cells, most in vitro studies of infection have been conducted under conditions that promote rapid germination of spores within the culture medium. Results Using an in vitro model of infection, we evaluated the influence of the germination state of B. anthracis spores, as controlled by defined culture conditions, on the outcome of infection. Spores prepared from B. anthracis Sterne 7702 germinated in a variety of common cell culture media supplemented with fetal bovine serum (FBS) while, in the absence of FBS, germination was strictly dependent on medium composition. RAW264.7 macrophage-like cells internalized spores to the same extent in either germinating or non-germinating media. However, significantly more viable, intracellular B. anthracis were recovered from cells infected under non-germinating conditions compared to germinating conditions. At the same time, RAW264.7 cells demonstrated a significant loss in viability when infected under non-germinating conditions. Conclusions These results suggest that the outcome of host cell infection is sensitive to the germination state of spores at the time of uptake. Moreover, this study demonstrates the efficacy of studying B. anthracis spore infection of host cells within a defined, non-germinating, in vitro environment.
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Autoregulatory characteristics of a Bacillus anthracis serine/threonine kinase. J Bacteriol 2011; 193:1833-42. [PMID: 21296958 DOI: 10.1128/jb.01401-10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BA-Stk1 is a serine/threonine kinase (STK) expressed by Bacillus anthracis. In previous studies, we found that BA-Stk1 activity is modulated through dephosphorylation by a partner phosphatase, BA-Stp1. In this study, we identified critical phosphorylation regions of BA-Stk1 and determined the contributions of these phosphodomains to autophosphorylation and substrate phosphorylation. The data indicate that BA-Stk1 undergoes trans-autophosphorylation within a regulatory domain, referred to as the activation loop, which carries eight putative regulatory serine and threonine residues. We identified activation loop mutants that impacted kinase activity in three different manners: regulation of autophosphorylation (T162), regulation of substrate phosphorylation (T159 and S169), and regulation of overall kinase activity (T163). Tandem mass spectrometry (MS/MS) analysis of the phosphorylation profile of each mutant revealed a second site of phosphorylation on the kinase that was influenced by the phosphorylation status of the activation loop. This second region of the kinase contained a single phosphorylation residue, S214. Previous work has shown S214 to be necessary for downstream substrate phosphorylation, and we have shown that this residue is subject to dephosphorylation by BA-Stp1. These findings indicate a connection between the phosphorylation status of the activation loop and phosphorylation of S214, and this suggests a previously undescribed model for how a bacterial STK shifts from a state of autophosphorylation to targeting downstream substrates.
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Cava F, Lam H, de Pedro MA, Waldor MK. Emerging knowledge of regulatory roles of D-amino acids in bacteria. Cell Mol Life Sci 2010; 68:817-31. [PMID: 21161322 PMCID: PMC3037491 DOI: 10.1007/s00018-010-0571-8] [Citation(s) in RCA: 234] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 09/24/2010] [Accepted: 10/14/2010] [Indexed: 12/24/2022]
Abstract
The d-enantiomers of amino acids have been thought to have relatively minor functions in biological processes. While l-amino acids clearly predominate in nature, d-amino acids are sometimes found in proteins that are not synthesized by ribosomes, and d-Ala and d-Glu are routinely found in the peptidoglycan cell wall of bacteria. Here, we review recent findings showing that d-amino acids have previously unappreciated regulatory roles in the bacterial kingdom. Many diverse bacterial phyla synthesize and release d-amino acids, including d-Met and d-Leu, which were not previously known to be made. These noncanonical d-amino acids regulate cell wall remodeling in stationary phase and cause biofilm dispersal in aging bacterial communities. Elucidating the mechanisms by which d-amino acids govern cell wall remodeling and biofilm disassembly will undoubtedly reveal new paradigms for understanding how extracytoplasmic processes are regulated as well as lead to development of novel therapeutics.
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Affiliation(s)
- Felipe Cava
- Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, and Howard Hughes Medical Institute, Boston, MA 02115, USA.
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Testing nucleoside analogues as inhibitors of Bacillus anthracis spore germination in vitro and in macrophage cell culture. Antimicrob Agents Chemother 2010; 54:5329-36. [PMID: 20921305 DOI: 10.1128/aac.01029-10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Bacillus anthracis, the etiological agent of anthrax, has a dormant stage in its life cycle known as the endospore. When conditions become favorable, spores germinate and transform into vegetative bacteria. In inhalational anthrax, the most fatal manifestation of the disease, spores enter the organism through the respiratory tract and germinate in phagosomes of alveolar macrophages. Germinated cells can then produce toxins and establish infection. Thus, germination is a crucial step for the initiation of pathogenesis. B. anthracis spore germination is activated by a wide variety of amino acids and purine nucleosides. Inosine and l-alanine are the two most potent nutrient germinants in vitro. Recent studies have shown that germination can be hindered by isomers or structural analogues of germinants. 6-Thioguanosine (6-TG), a guanosine analogue, is able to inhibit germination and prevent B. anthracis toxin-mediated necrosis in murine macrophages. In this study, we screened 46 different nucleoside analogues as activators or inhibitors of B. anthracis spore germination in vitro. These compounds were also tested for their ability to protect the macrophage cell line J774a.1 from B. anthracis cytotoxicity. Structure-activity relationship analysis of activators and inhibitors clarified the binding mechanisms of nucleosides to B. anthracis spores. In contrast, no structure-activity relationships were apparent for compounds that protected macrophages from B. anthracis-mediated killing. However, multiple inhibitors additively protected macrophages from B. anthracis.
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Mallozzi M, Viswanathan VK, Vedantam G. Spore-forming Bacilli and Clostridia in human disease. Future Microbiol 2010; 5:1109-23. [DOI: 10.2217/fmb.10.60] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Many Gram-positive spore-forming bacteria in the Firmicute phylum are important members of the human commensal microbiota, which, in rare cases, cause opportunistic infections. Other spore-formers, however, have evolved to become dedicated pathogens that can cause a striking variety of diseases. Despite variations in disease presentation, the etiologic agent is often the spore, with bacterially produced toxins playing a central role in the pathophysiology of infection. This review will focus on the specific diseases caused by spores of the Clostridia and Bacilli.
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Affiliation(s)
- Michael Mallozzi
- Department of Veterinary Science and Microbiology, University of Arizona, 1117, East Lowell St., Building 90, Room 303, Tucson, AZ 85721, USA
| | - VK Viswanathan
- Department of Veterinary Science and Microbiology, University of Arizona, 1117, East Lowell St., Building 90, Room 303, Tucson, AZ 85721, USA
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Cutting SM, Hong HA, Baccigalupi L, Ricca E. Oral vaccine delivery by recombinant spore probiotics. Int Rev Immunol 2010; 28:487-505. [PMID: 19954360 DOI: 10.3109/08830180903215605] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Over the past few decades, advancements in molecular and cell biology have allowed scientists to identify a large number of new antigens from a variety of viral and bacterial pathogens. However, successful development of these antigens into effective vaccines strongly relies on delivery systems able to avoid the rapid loss of biological activity that often impairs antigen efficacy. Various delivery systems have been proposed as alternative vaccine vehicles, from live microorganisms to nanoparticles, and all of them have shown advantages but also drawbacks. The bacterial spore is a quiescent cell form that, as a vaccine vehicle, may conjugate some advantages of live microorganisms with those of synthetic nanoparticles and that has recently been proposed as a potentially powerful tool to deliver antigens to mucosal surfaces. Here we review the use of bacterial spores as a delivery system for mucosal immunizations. We will first analyze the nature of the interaction between wild type spores and the gut-associated lymphoid tissue and then address the immune responses that are induced by oral immunizations with recombinant spores displaying heterologous antigens.
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Affiliation(s)
- Simon M Cutting
- School of Biological Sciences, Royal Holloway University of London, Egham, UK
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Shetron-Rama LM, Herring-Palmer AC, Huffnagle GB, Hanna P. Transport of Bacillus anthracis from the lungs to the draining lymph nodes is a rapid process facilitated by CD11c+ cells. Microb Pathog 2010; 49:38-46. [PMID: 20188814 DOI: 10.1016/j.micpath.2010.02.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 08/14/2009] [Accepted: 02/18/2010] [Indexed: 11/27/2022]
Abstract
Inhalational anthrax is established after inhaled Bacillus anthracis spores are transported to the lung associated lymph nodes. Dendritic cells (CD11c+ cells) located in the lungs are phagocytes that maintain many capabilities consistent with transport. This study investigates the role of dendritic cells as conduits of spores from the lung to the draining lymph nodes. The intratracheally spore-challenged mouse model of inhalational anthrax was utilized to investigate in vivo activities of CD11c+ cells. FITC labeled spores were delivered to the lungs of mice. Subsequently lung associated lymph nodes were isolated after infection and CD11c+ cells were found in association with the labeled spores. Further investigation of CD11c+ cells in early anthrax events was facilitated by use of the CD11c-diphtheria toxin (DT) receptor-green fluorescent protein transgenic mice in which CD11c+ cells can be transiently depleted by treatment with DT. We found that the presence of CD11c+ cells was necessary for efficient traffic of the spore to lung associated lymph nodes at early times after infection. Cultured dendritic cells were used to determine that these cells are capable of B. anthracis spore phagocytosis, and support germination and outgrowth. This data demonstrates that CD11c+ cells are likely carriers of B. anthracis spores from the point of inhalation in the lung to the lung associated lymph nodes. The cultured dendritic cell allows for spore germination and outgrowth supporting the concept that the CD11c+ cell responsible for this function can be a dendritic cell.
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Affiliation(s)
- Lynne M Shetron-Rama
- Department of Microbiology & Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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Driks A. The Bacillus anthracis spore. Mol Aspects Med 2009; 30:368-73. [DOI: 10.1016/j.mam.2009.08.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 08/09/2009] [Indexed: 01/27/2023]
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Regulatory interactions of a virulence-associated serine/threonine phosphatase-kinase pair in Bacillus anthracis. J Bacteriol 2009; 192:400-9. [PMID: 19915022 DOI: 10.1128/jb.01221-09] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In the current study, we examined the regulatory interactions of a serine/threonine phosphatase (BA-Stp1), serine/threonine kinase (BA-Stk1) pair in Bacillus anthracis. B. anthracis STPK101, a null mutant lacking BA-Stp1 and BA-Stk1, was impaired in its ability to survive within macrophages, and this correlated with an observed reduction in virulence in a mouse model of pulmonary anthrax. Biochemical analyses confirmed that BA-Stp1 is a PP2C phosphatase and dephosphorylates phosphoserine and phosphothreonine residues. Treatment of BA-Stk1 with BA-Stp1 altered BA-Stk1 kinase activity, indicating that the enzymatic function of BA-Stk1 can be influenced by BA-Stp1 dephosphorylation. Using a combination of mass spectrometry and mutagenesis approaches, three phosphorylated residues, T165, S173, and S214, in BA-Stk1 were identified as putative regulatory targets of BA-Stp1. Further analysis found that T165 and S173 were necessary for optimal substrate phosphorylation, while S214 was necessary for complete ATP hydrolysis, autophosphorylation, and substrate phosphorylation. These findings provide insight into a previously undescribed Stp/Stk pair in B. anthracis.
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Roles of the Bacillus anthracis spore protein ExsK in exosporium maturation and germination. J Bacteriol 2009; 191:7587-96. [PMID: 19837802 DOI: 10.1128/jb.01110-09] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Bacillus anthracis spore is the causative agent of the disease anthrax. The outermost structure of the B. anthracis spore, the exosporium, is a shell composed of approximately 20 proteins. The function of the exosporium remains poorly understood and is an area of active investigation. In this study, we analyzed the previously identified but uncharacterized exosporium protein ExsK. We found that, in contrast to other exosporium proteins, ExsK is present in at least two distinct locations, i.e., the spore surface as well as a more interior location underneath the exosporium. In spores that lack the exosporium basal layer protein ExsFA/BxpB, ExsK fails to encircle the spore and instead is present at only one spore pole, indicating that ExsK assembly to the spore is partially dependent on ExsFA/BxpB. In spores lacking the exosporium surface protein BclA, ExsK fails to mature into high-molecular-mass species observed in wild-type spores. These data suggest that the assembly and maturation of ExsK within the exosporium are dependent on ExsFA/BxpB and BclA. We also found that ExsK is not required for virulence in murine and guinea pig models but that it does inhibit germination. Based on these data, we propose a revised model of exosporium maturation and assembly and suggest a novel role for the exosporium in germination.
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Affiliation(s)
- Steven R. Blanke
- Department of Microbiology and the Institute for Genomic Biology, University of Illinois, Urbana, IL 61810, USA
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Couñago RM, Davlieva M, Strych U, Hill RE, Krause KL. Biochemical and structural characterization of alanine racemase from Bacillus anthracis (Ames). BMC STRUCTURAL BIOLOGY 2009; 9:53. [PMID: 19695097 PMCID: PMC2743695 DOI: 10.1186/1472-6807-9-53] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Accepted: 08/20/2009] [Indexed: 12/04/2022]
Abstract
BACKGROUND Bacillus anthracis is the causative agent of anthrax and a potential bioterrorism threat. Here we report the biochemical and structural characterization of B. anthracis (Ames) alanine racemase (AlrBax), an essential enzyme in prokaryotes and a target for antimicrobial drug development. We also compare the native AlrBax structure to a recently reported structure of the same enzyme obtained through reductive lysine methylation. RESULTS B. anthracis has two open reading frames encoding for putative alanine racemases. We show that only one, dal1, is able to complement a D-alanine auxotrophic strain of E. coli. Purified Dal1, which we term AlrBax, is shown to be a dimer in solution by dynamic light scattering and has a Vmax for racemization (L- to D-alanine) of 101 U/mg. The crystal structure of unmodified AlrBax is reported here to 1.95 A resolution. Despite the overall similarity of the fold to other alanine racemases, AlrBax makes use of a chloride ion to position key active site residues for catalysis, a feature not yet observed for this enzyme in other species. Crystal contacts are more extensive in the methylated structure compared to the unmethylated structure. CONCLUSION The chloride ion in AlrBax is functioning effectively as a carbamylated lysine making it an integral and unique part of this structure. Despite differences in space group and crystal form, the two AlrBax structures are very similar, supporting the case that reductive methylation is a valid rescue strategy for proteins recalcitrant to crystallization, and does not, in this case, result in artifacts in the tertiary structure.
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Affiliation(s)
- Rafael M Couñago
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Milya Davlieva
- Department of Biochemistry Rice University, Houston, TX, USA
| | - Ulrich Strych
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA
| | - Ryan E Hill
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Kurt L Krause
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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Cote CK, Bozue J, Twenhafel N, Welkos SL. Effects of altering the germination potential of Bacillus anthracis spores by exogenous means in a mouse model. J Med Microbiol 2009; 58:816-825. [DOI: 10.1099/jmm.0.008656-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Inhalational anthrax is the most severe form of anthrax. It has been shown in small-animal and non-human primate models that relatively large pools of ungerminated Bacillus anthracis spores can remain within the alveolar spaces for days to weeks post-inhalation or until transported to areas more favourable for germination and bacillary outgrowth. In this study, spores of the Ames strain that were exposed to germination-inducing media prior to intranasal delivery were significantly less infectious than spores delivered in either water or germination-inhibitory medium. The effect of manipulating the germination potential of these spores within the lungs of infected mice by exogenous germination-altering media was examined. The data suggested that neither inducing germination nor inhibiting germination of spores within the lungs protected mice from the ensuing infection. Germination-altering strategies could, instead, significantly increase the severity of disease in a mouse model of inhalational anthrax when implemented in vivo. It was shown that germination-altering strategies, in this study, were not beneficial to the infected host and are impractical as in vivo countermeasures.
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Affiliation(s)
- C. K. Cote
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD, USA
| | - J. Bozue
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD, USA
| | - N. Twenhafel
- Pathology Division, US Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD, USA
| | - S. L. Welkos
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD, USA
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Ceragioli M, Cangiano G, Esin S, Ghelardi E, Ricca E, Senesi S. Phagocytosis, germination and killing of Bacillus subtilis spores presenting heterologous antigens in human macrophages. Microbiology (Reading) 2009; 155:338-346. [DOI: 10.1099/mic.0.022939-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Bacillus subtilis is a Gram-positive spore-bearing bacterium long used as a probiotic product and more recently regarded as an attractive vehicle for delivering heterologous antigens to be used for mucosal vaccination. This report describes the in vitro interaction between human macrophages and B. subtilis spores displaying the tetanus toxin fragment C or the B subunit of the heat-labile toxin of Escherichia coli on their surface in comparison to spores of the parental strain. Recombinant and parental B. subtilis spores were similarly internalized by human macrophages, at a frequency lower than 2.5 %. Inside macrophages, nearly all spores germinated and were killed within 6 h. Using germination-defective spores and inhibiting spore germination inside macrophages, evidence was produced that only germinated spores were killed by human macrophages and that intracellular spore germination was mediated by an alanine-dependent pathway. The germinated spores were killed by macrophages before any round of cell duplication, as estimated by fluorescence microscopy analysis of macrophages infected with spores carrying the gfp gene fused to abrB, a B. subtilis gene shown here to be expressed at the transition between outgrowth and vegetative growth. Monitoring of macrophage infection never revealed cytotoxic effects being exerted by B. subtilis spores. These in vitro data support the hypothesis that B. subtilis spores may potentially be used as a suitable and safe vehicle for administering heterologous antigens to humans.
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Affiliation(s)
- Mara Ceragioli
- Dipartimento di Biologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy
| | - Giuseppina Cangiano
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, via Cinthia, 80126 Napoli, Italy
| | - Semih Esin
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy
| | - Emilia Ghelardi
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy
| | - Ezio Ricca
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, via Cinthia, 80126 Napoli, Italy
| | - Sonia Senesi
- Dipartimento di Biologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy
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The spore-specific alanine racemase of Bacillus anthracis and its role in suppressing germination during spore development. J Bacteriol 2008; 191:1303-10. [PMID: 19074397 DOI: 10.1128/jb.01098-08] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Spores of Bacillus anthracis are enclosed by an exosporium composed of a basal layer and an external hair-like nap. The nap is apparently formed by a single glycoprotein, while the basal layer contains many different structural proteins and several enzymes. One of the enzymes is Alr, an alanine racemase capable of converting the spore germinant l-alanine to the germination inhibitor d-alanine. Unlike other characterized exosporium proteins, Alr is nonuniformly distributed in the exosporium and might have a second spore location. In this study, we demonstrated that expression of the alr gene, which encodes Alr, is restricted to sporulating cells and that the bulk of alr transcription and Alr synthesis occurs during the late stages of sporulation. We also mapped two alr promoters that are differentially active during sporulation and might be involved in the atypical localization of Alr. Finally, we constructed a Deltaalr mutant of B. anthracis that lacks Alr and examined the properties of the spores produced by this strain. Mature Deltaalr spores germinate more efficiently in the presence of l-alanine, presumably because of their inability to convert exogenous l-alanine to d-alanine, but they respond normally to other germinants. Surprisingly, the production of mature spores by the Deltaalr mutant is defective because approximately one-half of the nascent spores germinate and lose their resistance properties before they are released from the mother cell. This phenotype suggests that an important function of Alr is to produce D-alanine during the late stages of sporulation to suppress premature germination of the developing spore.
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Four superoxide dismutases contribute to Bacillus anthracis virulence and provide spores with redundant protection from oxidative stress. Infect Immun 2008; 77:274-85. [PMID: 18955476 DOI: 10.1128/iai.00515-08] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Bacillus anthracis genome encodes four superoxide dismutases (SODs), enzymes capable of detoxifying oxygen radicals. That two of these SODs, SOD15 and SODA1, are present in the outermost layers of the B. anthracis spore is indicated by previous proteomic analyses of the exosporium. Given the requirement that spores must survive interactions with reactive oxygen species generated by cells such as macrophages during infection, we hypothesized that SOD15 and SODA1 protect the spore from oxidative stress and contribute to the pathogenicity of B. anthracis. To test these theories, we constructed a double-knockout (Delta sod15 Delta sodA1) mutant of B. anthracis Sterne strain 34F2 and assessed its lethality in an A/J mouse intranasal infection model. The 50% lethal dose of the Delta sod15 Delta sodA1 strain was similar to that of the wild type (34F2), but surprisingly, measurable whole-spore SOD activity was greater than that in 34F2. A quadruple-knockout strain (Delta sod15 Delta sodA1 Delta sodC Delta sodA2) was then generated, and as anticipated, spore-associated SOD activity was diminished. Moreover, the quadruple-knockout strain, compared to the wild type, was attenuated more than 40-fold upon intranasal challenge of mice. Spore resistance to exogenously generated oxidative stress and to macrophage-mediated killing correlated with virulence in A/J mice. Allelic exchange that restored sod15 and sodA1 to their wild-type state restored wild-type characteristics. We conclude that SOD molecules within the spore afford B. anthracis protection against oxidative stress and enhance the pathogenicity of B. anthracis in the lung. We also surmise that the presence of four SOD alleles within the genome provides functional redundancy for this key enzyme.
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