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Martínez LE, Gómez G, Ramírez N, Franco B, Robleto EA, Pedraza-Reyes M. 8-OxoG-Dependent Regulation of Global Protein Responses Leads to Mutagenesis and Stress Survival in Bacillus subtilis. Antioxidants (Basel) 2024; 13:332. [PMID: 38539865 PMCID: PMC10968225 DOI: 10.3390/antiox13030332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 02/27/2024] [Accepted: 03/05/2024] [Indexed: 04/04/2024] Open
Abstract
The guanine oxidized (GO) system of Bacillus subtilis, composed of the YtkD (MutT), MutM and MutY proteins, counteracts the cytotoxic and genotoxic effects of the oxidized nucleobase 8-OxoG. Here, we report that in growing B. subtilis cells, the genetic inactivation of GO system potentiated mutagenesis (HPM), and subsequent hyperresistance, contributes to the damaging effects of hydrogen peroxide (H2O2) (HPHR). The mechanism(s) that connect the accumulation of the mutagenic lesion 8-OxoG with the ability of B. subtilis to evolve and survive the noxious effects of oxidative stress were dissected. Genetic and biochemical evidence indicated that the synthesis of KatA was exacerbated, in a PerR-independent manner, and the transcriptional coupling repair factor, Mfd, contributed to HPHR and HPM of the ΔGO strain. Moreover, these phenotypes are associated with wider pleiotropic effects, as revealed by a global proteome analysis. The inactivation of the GO system results in the upregulated production of KatA, and it reprograms the synthesis of the proteins involved in distinct types of cellular stress; this has a direct impact on (i) cysteine catabolism, (ii) the synthesis of iron-sulfur clusters, (iii) the reorganization of cell wall architecture, (iv) the activation of AhpC/AhpF-independent organic peroxide resistance, and (v) increased resistance to transcription-acting antibiotics. Therefore, to contend with the cytotoxic and genotoxic effects derived from the accumulation of 8-OxoG, B. subtilis activates the synthesis of proteins belonging to transcriptional regulons that respond to a wide, diverse range of cell stressors.
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Affiliation(s)
- Lissett E. Martínez
- Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato 36050, Mexico; (L.E.M.); (G.G.); (N.R.); (B.F.)
| | - Gerardo Gómez
- Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato 36050, Mexico; (L.E.M.); (G.G.); (N.R.); (B.F.)
| | - Norma Ramírez
- Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato 36050, Mexico; (L.E.M.); (G.G.); (N.R.); (B.F.)
| | - Bernardo Franco
- Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato 36050, Mexico; (L.E.M.); (G.G.); (N.R.); (B.F.)
| | - Eduardo A. Robleto
- School of Life Sciences, University of Nevada, Las Vegas, NV 89557, USA;
| | - Mario Pedraza-Reyes
- Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato 36050, Mexico; (L.E.M.); (G.G.); (N.R.); (B.F.)
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Smita N, Sasikala C, Ramana C. New insights into peroxide toxicology: sporulenes help Bacillus subtilis endospores from hydrogen peroxide. J Appl Microbiol 2023; 134:lxad238. [PMID: 37863832 DOI: 10.1093/jambio/lxad238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 09/11/2023] [Accepted: 10/19/2023] [Indexed: 10/22/2023]
Abstract
AIM The purpose of the present study was to understand the possible events involved in the toxicity of hydrogen peroxide (H2O2) to wild and sporulene-deficient spores of Bacillus subtilis, as H2O2 was previously shown to have deleterious effects. METHODS AND RESULTS The investigation utilized two strains of B. subtilis, namely the wild-type PY79 (WT) and the sporulene-deficient TB10 (ΔsqhC mutant). Following treatment with 0.05% H2O2 (v/v), spore viability was assessed using a plate count assay, which revealed a significant decrease in cultivability of 80% for the ΔsqhC mutant spores. Possible reasons for the loss of spore viability were investigated with microscopic analysis, dipicholinic acid (DPA) quantification and propidium iodide (PI) staining. Microscopic examinations revealed the presence of withered and deflated morphologies in spores of ΔsqhC mutants treated with H2O2, indicating a compromised membrane permeability. This was further substantiated by the absence of DPA and a high frequency (50%-75%) of PI infiltration. The results of fatty acid methyl ester analysis and protein profiling indicated that the potentiation of H2O2-induced cellular responses was manifested in the form of altered spore composition in ΔsqhC B. subtilis. The slowed growth rates of the ΔsqhC mutant and the heightened sporulene biosynthesis pathways in the WT strain, both upon exposure to H2O2, suggested a protective function for sporulenes in vegetative cells. CONCLUSIONS Sporulenes serve as a protective layer for the inner membrane of spores, thus assuming a significant role in mitigating the adverse effects of H2O2 in WT B. subtilis. The toxic effects of H2O2 were even more pronounced in the spores of the ΔsqhC mutant, which lacks this protective barrier of sporulenes.
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Affiliation(s)
- N Smita
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, P.O. Central University, Hyderabad 500046, India
| | - Ch Sasikala
- Bacterial Discovery Laboratory, Centre for Environment, Institute of Science and Technology, J.N.T. University Hyderabad, Hyderabad 500085, India
| | - ChV Ramana
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, P.O. Central University, Hyderabad 500046, India
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3
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Moir A, Christie G. A coating of lipoproteins provides a stabilizing environment on the inner membrane of Bacillus subtilis spores. J Bacteriol 2023; 205:e0016723. [PMID: 37730539 PMCID: PMC10601610 DOI: 10.1128/jb.00167-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023] Open
Abstract
A new study by M. J. Flores, K. Duricy, S. Choudhary, M. Laue, and D. L. Popham (J Bacteriol 205:e00142-23, 2023, https://doi.org/10.1128/jb.00142-23) demonstrates a role for the YlaJ/YhcN family of lipoproteins in the immobilization of the spore's inner membrane. In the absence of these lipoproteins, membrane fluidity increases and membrane-associated proteins like the GerA receptor complexes are more exposed to inimical conditions. The role of these proteins in stabilizing the Bacillus spore inner membrane is now being explored.
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Affiliation(s)
- Anne Moir
- School of Biosciences, University of Sheffield, Firth Court, Sheffield, United Kingdom
| | - Graham Christie
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, United Kingdom
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Flores MJ, Duricy K, Choudhary S, Laue M, Popham DL. A Family of Spore Lipoproteins Stabilizes the Germination Apparatus by Altering Inner Spore Membrane Fluidity in Bacillus subtilis Spores. J Bacteriol 2023; 205:e0014223. [PMID: 37338384 PMCID: PMC10601750 DOI: 10.1128/jb.00142-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 05/26/2023] [Indexed: 06/21/2023] Open
Abstract
Dormant bacterial spores undergo the process of germination to return to a vegetative state. In most species, germination involves the sensing of nutrient germinants, the release of various cations and a calcium-dipicolinic acid (DPA) complex, spore cortex degradation, and full rehydration of the spore core. These steps are mediated by membrane-associated proteins, and all these proteins have exposure on the outer surface of the membrane, a hydrated environment where they are potentially subject to damage during dormancy. A family of lipoproteins, including YlaJ, which is expressed from the sleB operon in some species, are present in all sequenced Bacillus and Clostridium genomes that contain sleB. B. subtilis possesses four proteins in this family, and prior studies have demonstrated two of these are required for efficient spore germination and these proteins contain a multimerization domain. Genetic studies of strains lacking all combinations of these four genes now reveal all four play roles in ensuring efficient germination, and affect multiple steps in this process. Electron microscopy does not reveal significant changes in spore morphology in strains lacking lipoproteins. Generalized polarization measurements of a membrane dye probe indicate the lipoproteins decrease spore membrane fluidity. These data suggest a model in which the lipoproteins form a macromolecular structure on the outer surface of the inner spore membrane, where they act to stabilize the membrane and potentially interact with other germination proteins, and thus stabilize the function of multiple components of the germination machinery. IMPORTANCE Bacterial spores exhibit extreme longevity and resistance to many killing agents, and are thus problematic agents of several diseases and of food spoilage. However, to cause disease or spoilage, germination of the spore and return to the vegetative state is necessary. The proteins responsible for initiation and progression of germination are thus potential targets for spore-killing processes. A family of membrane-bound lipoproteins that are conserved across most spore-forming species was studied in the model organism Bacillus subtilis. The results indicate that these proteins reduce the membrane fluidity and increase the stability of other membrane associated proteins that are required for germination. Further understanding of such protein interactions on the spore membrane surface will enhance our understanding of the germination process and its potential as a decontamination method target.
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Affiliation(s)
- Matthew J. Flores
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | - Kate Duricy
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | - Shreya Choudhary
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | - Michael Laue
- Advanced Light and Electron Microscopy (ZBS 4), Robert Koch Institute, Berlin, Germany
| | - David L. Popham
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
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Chen T, Brul S, Hugenholtz J. Exploring the potential of Bacillus subtilis as cell factory for food ingredients and special chemicals. Microb Cell Fact 2023; 22:200. [PMID: 37777723 PMCID: PMC10542680 DOI: 10.1186/s12934-023-02208-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 09/19/2023] [Indexed: 10/02/2023] Open
Abstract
BACKGROUND Bacillus subtilis has been established as model microorganism for fundamental research in the laboratory on protein production/secretion and sporulation and as model bacterium for controlling spoilage in the food industry. It has also been used for production of (commercial) enzymes and several secondary metabolites such as vitamins. However, this doesn't fully reflect the potential of B. subtilis as a cell-factory. Here, various strains of B. subtilis, including food-grade, spore-deficient strains and industrially used strains, were compared for their growth and metabolic potential. Industry-relevant parameters were analyzed for all strains under various aeration regimes, under anaerobic conditions, in various nutritious and nutrient-limited cultivation media, with and without organic nitrogen sources, and with and without sugar. RESULTS Practical experiments were conducted to compare industrial relevant properties like growth rates, intracellular components and extracellular metabolite profile of different B. subtilis strains. Based on growth flexibility in different media, we found that some strains like NCIB3610 and DSM1092 are adapted to inorganic or organic nitrogen source utilization, which is highly relevant when considering a biorefinery approach using various cheap and abundant waste/sidestreams. Secondly, spore-deficient strains such as 3NA, 168 S and PY79S, showed advantages in microbial protein and acetolactate pathway expression, which is associated with applications in food industry for protein supplement and diacetyl production. Lastly, WB800 and PY79S exhibited potential for fermentative production of dipicolinic acid, 2,3-butanediol and lactic acid that could serve as precursors for biopolymers. CONCLUSION This study demonstrates the broad potential for more extensive industrial use of Bacillus subtilis in the (bio-based) chemical industry for use of sidestreams, in the personal care industry, in the food industry for food additive production, and in the bio-sustainable industry for biofuel and bio-degradable plastic precursors production. In addition, selecting different B. subtilis strains for specific purposes makes full use of the diversity of this species and increases the potential of B. subtilis in its contribution to the bio-based economy.
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Affiliation(s)
- Taichi Chen
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, 1098 XH, The Netherlands
| | - Stanley Brul
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, 1098 XH, The Netherlands.
| | - Jeroen Hugenholtz
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, 1098 XH, The Netherlands.
- NoPalm Ingredients BV, Nieuwe Kanaal 7a, Wageningen, 6709 PA, The Netherlands.
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6
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Inactivation mechanism of slightly acidic electrolyzed water on Bacillus cereus spores. Food Microbiol 2022; 103:103951. [DOI: 10.1016/j.fm.2021.103951] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 09/11/2021] [Accepted: 11/19/2021] [Indexed: 01/18/2023]
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Herschend J, Ernst M, Koren K, Melnik AV, da Silva RR, Røder HL, Damholt ZBV, Hägglund P, Svensson B, Sørensen SJ, Kühl M, Dorrestein PC, Burmølle M. Metabolic Profiling of Interspecies Interactions During Sessile Bacterial Cultivation Reveals Growth and Sporulation Induction in Paenibacillus amylolyticus in Response to Xanthomonas retroflexus. Front Cell Infect Microbiol 2022; 12:805473. [PMID: 35425721 PMCID: PMC9001975 DOI: 10.3389/fcimb.2022.805473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 02/28/2022] [Indexed: 11/13/2022] Open
Abstract
The toolbox available for microbiologists to study interspecies interactions is rapidly growing, and with continuously more advanced instruments, we are able to expand our knowledge on establishment and function of microbial communities. However, unravelling molecular interspecies interactions in complex biological systems remains a challenge, and interactions are therefore often studied in simplified communities. Here we perform an in-depth characterization of an observed interspecies interaction between two co-isolated bacteria, Xanthomonas retroflexus and Paenibacillus amylolyticus. Using microsensor measurements for mapping the chemical environment, we show how X. retroflexus promoted an alkalization of its local environment through degradation of amino acids and release of ammonia. When the two species were grown in proximity, the modified local environment induced a morphological change and growth of P. amylolyticus followed by sporulation. 2D spatial metabolomics enabled visualization and mapping of the degradation of oligopeptide structures by X. retroflexus and morphological changes of P. amylolyticus through e.g. the release of membrane-associated metabolites. Proteome analysis and microscopy were used to validate the shift from vegetative growth towards sporulation. In summary, we demonstrate how environmental profiling by combined application of microsensor, microscopy, metabolomics and proteomics approaches can reveal growth and sporulation promoting effects resulting from interspecies interactions.
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Affiliation(s)
- Jakob Herschend
- Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Madeleine Ernst
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, United States
- Section for Clinical Mass Spectrometry, Danish Center for Neonatal Screening, Department of Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Klaus Koren
- Aarhus University Centre for Water Technology (WATEC), Department of Biology, Aarhus University, Aarhus, Denmark
| | - Alexey V. Melnik
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Ricardo R. da Silva
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Henriette L. Røder
- Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Zacharias B. V. Damholt
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Per Hägglund
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Birte Svensson
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Søren J. Sørensen
- Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Pieter C. Dorrestein
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Mette Burmølle
- Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- *Correspondence: Mette Burmølle,
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8
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Moderate high-pressure superdormancy in Bacillus spores: properties of superdormant spores and proteins potentially influencing moderate high-pressure germination. Appl Environ Microbiol 2021; 88:e0240621. [PMID: 34910565 PMCID: PMC8863042 DOI: 10.1128/aem.02406-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Resistant bacterial spores are a major concern in industrial decontamination processes. An approach known as pressure-mediated germination-inactivation strategy aims to artificially germinate spores by isostatic pressure to mitigate their resistance to inactivation processes. The successful implementation of such a germination-inactivation strategy relies on the germination of all spores. However, germination is heterogeneous, with some “superdormant” spores germinating extremely slowly or not at all. The present study investigated potential underlying reasons for moderate high-pressure (150 MPa; 37°C) superdormancy of Bacillus subtilis spores. The water and dipicolinic acid content of superdormant spores was compared with that of the initial dormant spore population. The results suggest that water and dipicolinic acid content are not major drivers of moderate high-pressure superdormancy. A proteomic analysis was used to identify proteins that were quantified at significantly different levels in superdormant spores. Subsequent validation of the germination capacity of deletion mutants revealed that the presence of protein YhcN is required for efficient moderate high-pressure germination and that proteins MinC, cse60, and SspK may also play a role, albeit a minor one. IMPORTANCE Spore-forming bacteria are ubiquitous in nature and, as a consequence, inevitably enter the food chain or other processing environments. Their presence can lead to significant spoilage or safety-related issues. Intensive treatment is usually required to inactivate them; however, this treatment harms important product quality attributes. A pressure-mediated germination-inactivation approach can balance the need for effective spore inactivation and retention of sensitive ingredients. However, superdormant spores are the bottleneck preventing the successful and safe implementation of such a strategy. An in-depth understanding of moderate high-pressure germination and the underlying causes of superdormancy is necessary to advance the development of mild high pressure-based spore control technologies. The approach used in this work allowed the identification of proteins that have not yet been associated with reduced germination at moderate high pressure. This research paves the way for further studies on the germination and superdormancy mechanisms in spores, assisting the development of mild spore inactivation strategies.
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Liu B, Chan H, Bauda E, Contreras-Martel C, Bellard L, Villard AM, Mas C, Neumann E, Fenel D, Favier A, Serrano M, Henriques AO, Rodrigues CDA, Morlot C. Structural insights into ring-building motif domains involved in bacterial sporulation. J Struct Biol 2021; 214:107813. [PMID: 34808342 DOI: 10.1016/j.jsb.2021.107813] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 10/29/2021] [Accepted: 11/15/2021] [Indexed: 02/06/2023]
Abstract
Components of specialized secretion systems, which span the inner and outer membranes in Gram-negative bacteria, include ring-forming proteins whose oligomerization was proposed to be promoted by domains called RBM for "Ring-Building Motifs". During spore formation in Gram-positive bacteria, a transport system called the SpoIIIA-SpoIIQ complex also assembles in the double membrane that surrounds the forespore following its endocytosis by the mother cell. The presence of RBM domains in some of the SpoIIIA proteins led to the hypothesis that they would assemble into rings connecting the two membranes and form a conduit between the mother cell and forespore. Among them, SpoIIIAG forms homo-oligomeric rings in vitro but the oligomerization of other RBM-containing SpoIIIA proteins, including SpoIIIAH, remains to be demonstrated. In this work, we identified RBM domains in the YhcN/YlaJ family of proteins that are not related to the SpoIIIA-SpoIIQ complex. We solved the crystal structure of YhcN from Bacillus subtilis, which confirmed the presence of a RBM fold, flanked by additional secondary structures. As the protein did not show any oligomerization ability in vitro, we investigated the structural determinants of ring formation in SpoIIIAG, SpoIIIAH and YhcN. We showed that in vitro, the conserved core of RBM domains alone is not sufficient for oligomerization while the β-barrel forming region in SpoIIIAG forms rings on its own. This work suggests that some RBMs might indeed participate in the assembly of homomeric rings but others might have evolved toward other functions.
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Affiliation(s)
- Bowen Liu
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Helena Chan
- The ithree institute, University of Technology Sydney, 2007 Ultimo, NSW, Australia
| | - Elda Bauda
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | | | - Laure Bellard
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | | | - Caroline Mas
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | | | - Daphna Fenel
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Adrien Favier
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Monica Serrano
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal
| | | | - Cecile Morlot
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France.
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Accumulation and Release of Rare Earth Ions by Spores of Bacillus Species and the Location of These Ions in Spores. Appl Environ Microbiol 2019; 85:AEM.00956-19. [PMID: 31253678 DOI: 10.1128/aem.00956-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 06/20/2019] [Indexed: 12/28/2022] Open
Abstract
Two rare earth ions, Tb3+ and Dy3+, were incorporated into spores of Bacillus species in ≤5 min at neutral pH to 100 to 200 nmol per mg of dry spores, which is equivalent to 2 to 3% of the spore dry weight. The uptake of these ions had, at most, minimal effects on spore wet heat resistance or germination, and the ions were all released upon germination, probably by complex formation with the huge depot of dipicolinic acid (DPA) released when spores germinate. Adsorbed Tb3+/Dy3+ were also released by exogenous DPA within a few minutes and faster than in spore germination. The accumulation of Tb3+/Dy3+ was not reduced in Bacillus subtilis spores by several types of coat defects, significant modification of the spore cortex peptidoglycan structure, specific loss of components of the outer spore crust layer, or the absence of DPA in the spore core. All of these findings are consistent with Tb3+/Dy3+ being accumulated in spores' outer layers, and this was confirmed by transmission electron microscopy. However, the identity of the outer spore components binding the Tb3+/Dy3+ is not clear. These findings provide new information on the adsorption of rare earth ions by Bacillus spores and suggest this adsorption might have applications in capturing rare earth ions from the environment.IMPORTANCE Biosorption of rare earth ions by growing cells of Bacillus species has been well studied and has attracted attention for possible hydrometallurgy applications. However, the interaction of spores from Bacillus species with rare earth ions has not been well studied. We investigated here the adsorption and/or desorption of two rare earth ions, Tb3+ and Dy3+, by Bacillus spores, the location of the adsorbed ions, and the spore properties after ion accumulation. The significant adsorption of rare earth ions on the surfaces of Bacillus spores and the ions' rapid release by a chelator could allow the development of these spores as a biosorbent to recover rare earth ions from the environment.
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11
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Ghosh S, Joseph G, Korza G, He L, Yuan J, Dong W, Setlow B, Li Y, Savage P, Setlow P. Effects of the microbicide ceragenin CSA‐13 on and properties ofBacillus subtilisspores prepared on two very different media. J Appl Microbiol 2019; 127:109-120. [DOI: 10.1111/jam.14300] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 03/23/2019] [Accepted: 04/30/2019] [Indexed: 12/25/2022]
Affiliation(s)
- S. Ghosh
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
- Department of Science and Mathematics Capital Community College Hartford CT USA
| | - G. Joseph
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
| | - G. Korza
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
| | - L. He
- Department of Physics East Carolina University Greenville NC USA
- School of Electronic Engineering Dongguan University of Technology Dongguan People’s Republic of China
| | - J.‐H. Yuan
- Department of Physics East Carolina University Greenville NC USA
| | - W. Dong
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
- School of Resource and Environmental Engineering Jiangxi University of Science and Technology Ganzhou China
| | - B. Setlow
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
| | - Y.‐Q. Li
- Department of Physics East Carolina University Greenville NC USA
- School of Electronic Engineering Dongguan University of Technology Dongguan People’s Republic of China
| | - P.B. Savage
- Department of Chemistry and Biochemistry Brigham Young University Provo UT USA
| | - P. Setlow
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
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12
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Analysis of the mRNAs in Spores of Bacillus subtilis. J Bacteriol 2019; 201:JB.00007-19. [PMID: 30782632 DOI: 10.1128/jb.00007-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 02/08/2019] [Indexed: 12/12/2022] Open
Abstract
Large-scale shotgun sequencing (RNA-seq) analysis of mRNAs in dormant Bacillus subtilis spores prepared on plates or in liquid generally found the same ∼46 abundant mRNA species, with >250 mRNAs detected at much lower abundances. Knowledge of the amount of phosphate in a single B. subtilis spore allowed calculation of the amount of mRNA in an individual spore as ∼106 nucleotides (nt). Given the levels of abundant spore mRNAs compared to those of other mRNAs, it was calculated that the great majority of low-abundance mRNAs are present in only small fractions of spores in populations. Almost all of the most abundant spore mRNAs are encoded by genes expressed late in sporulation in the developing spore under the control of the forespore-specific RNA polymerase sigma factor, σG, and most of the encoded proteins are in spores. Levels of the most abundant spore mRNAs were also relatively stable for a week at 4°C after spore harvest. RNA-seq analysis of mRNAs in highly purified and less-well-purified spores made in liquid, as well as from spores that were chemically decoated to remove possible contaminating mRNA, indicated that low-abundance mRNAs in spores were not contaminants in purified spore preparations, and several sources of low-abundance mRNAs in spores are suggested. The function of at least the great majority of spore mRNAs seems most likely to be the generation of ribonucleotides for new RNA synthesis by their degradation early in spore revival.IMPORTANCE Previous work indicates that dormant Bacillus subtilis spores have many hundreds of mRNAs, some of which are suggested to play roles in spores' "return to life" or revival. The present work finds only ∼46 mRNAs at ≥1 molecule spore, with others in only fractions of spores in populations, often very small fractions. Less-abundant spore mRNAs are not contaminants in spore preparations, but how spores accumulate them is not clear. Almost all abundant spore mRNAs are synthesized in the developing spore late in its development, most encode proteins in spores, and abundant mRNAs in spores are relatively stable at 4°C. These findings will have a major impact on thinking about the roles that spore mRNAs may play in spore revival.
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Setlow P. Observations on research with spores of Bacillales and Clostridiales species. J Appl Microbiol 2019; 126:348-358. [PMID: 30106202 PMCID: PMC6329651 DOI: 10.1111/jam.14067] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 08/03/2018] [Accepted: 08/07/2018] [Indexed: 01/06/2023]
Abstract
The purpose of this article is to highlight some areas of research with spores of bacteria of Firmicute species in which the methodology too commonly used is not optimal and generates misleading results. As a consequence, conclusions drawn from data obtained are often flawed or not appropriate. Topics covered in the article include the following: (i) the importance of using well-purified bacterial spores in studies on spore resistance, composition, killing, disinfection and germination; (ii) methods for obtaining good purification of spores of various species; (iii) appropriate experimental approaches to determine mechanisms of spore resistance and spore killing by a variety of agents, as well as known mechanisms of spore resistance and killing; (iv) common errors made in drawing conclusions about spore killing by various agents, including failure to neutralize chemical agents before plating for viable spore enumeration, and equating correlations between changes in spore properties accompanying spore killing with causation. It is hoped that a consideration of these topics will improve the quality of spore research going forward.
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Affiliation(s)
- Peter Setlow
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030-3305 USA
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14
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Rao L, Feeherry FE, Ghosh S, Liao X, Lin X, Zhang P, Li Y, Doona CJ, Setlow P. Effects of lowering water activity by various humectants on germination of spores of Bacillus species with different germinants. Food Microbiol 2018; 72:112-127. [DOI: 10.1016/j.fm.2017.11.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/19/2017] [Accepted: 11/23/2017] [Indexed: 10/18/2022]
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Abstract
Bacterial endospores possess multiple integument layers, one of which is the cortex peptidoglycan wall. The cortex is essential for the maintenance of spore core dehydration and dormancy and contains structural modifications that differentiate it from vegetative cell peptidoglycan and determine its fate during spore germination. Following the engulfment stage of sporulation, the cortex is synthesized within the intermembrane space surrounding the forespore. Proteins responsible for cortex synthesis are produced in both the forespore and mother cell compartments. While some of these proteins also contribute to vegetative cell wall synthesis, others are sporulation specific. In order for the bacterial endospore to germinate and resume metabolism, the cortex peptidoglycan must first be degraded through the action of germination-specific lytic enzymes. These enzymes are present, yet inactive, in the dormant spore and recognize the muramic-δ-lactam modification present in the cortex. Germination-specific lytic enzymes across Bacillaceae and Clostridiaceae share this specificity determinant, which ensures that the spore cortex is hydrolyzed while the vegetative cell wall remains unharmed. Bacillus species tend to possess two redundant enzymes, SleB and CwlJ, capable of sufficient cortex degradation, while the clostridia have only one, SleC. Additional enzymes are often present that cannot initiate the cortex degradation process, but which can increase the rate of release of small fragments into the medium. Between the two families, the enzymes also differ in the enzymatic activities they possess and the mechanisms acting to restrict their activation until germination has been initiated.
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Stelder SK, Benito de Moya C, Hoefsloot HCJ, de Koning LJ, Brul S, de Koster CG. Stoichiometry, Absolute Abundance, and Localization of Proteins in the Bacillus cereus Spore Coat Insoluble Fraction Determined Using a QconCAT Approach. J Proteome Res 2018; 17:903-917. [PMID: 29260567 PMCID: PMC5799878 DOI: 10.1021/acs.jproteome.7b00732] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Spores of Bacillus cereus pose a threat to food
safety due to their high resistance to the heat or acid treatments
commonly used to make food microbiologically safe. Spores may survive
these treatments and later resume growth either on foodstuffs or,
after ingestion, upon entering the gut they are capable of producing
toxins, which cause either vomiting or diarrhea. The outer layers
of the spore, the spore coat and exosporium, consist primarily of
proteins that may serve as potential biomarkers for detection. The
major morphogenetic protein CotE is important for correct assembly
and attachment of the outermost layer, the exosporium, and by extension
retention of many proteins. However, characterization of the proteins
affected by deletion of CotE has been limited to electrophoretic patterns.
Here we report the effect of CotE deletion on the insoluble fraction
of the spore proteome through liquid chromatography–Fourier
transform tandem mass spectrometry (LC–FTMS/MS) analysis. A total of 560 proteins have been identified in both mutant
and wild-type spore coat isolates. A further 163 proteins were identified
exclusively in wild-type spore isolates indicating that they are dependent
on CotE for their association with the spore. Several of these are
newly confirmed as associated with the exosporium, namely BC_2569
(BclF), BC_3345, BC_2427, BC_2878, BC_0666, BC_2984, BC_3481, and
BC_2570. A total of 153 proteins were only identified in ΔCotE
spore isolates. This was observed for proteins that are known or likely
to be interacting with or are encased by CotE. Crucial spore proteins
were quantified using a QconCAT reference standard, the first time
this was used in a biochemically heterogeneous system. This allowed
us to determine the absolute abundance of 21 proteins, which spanned
across three orders of magnitude and together covered 5.66% ±
0.51 of the total spore weight. Applying the QconCAT methodology to
the ΔCotE mutant allowed us to quantify 4.13% ± 0.14 of
the spore total weight and revealed a reduction in abundance for most
known exosporium associated proteins upon CotE deletion. In contrast,
several proteins, either known or likely to be interacting with or
encased by CotE (i.e., GerQ), were more abundant. The results obtained
provide deeper insight into the layered spore structure such as which
proteins are exposed on the outside of the spore. This information
is important for developing detection methods for targeting spores
in a food safety setting. Furthermore, protein stoichiometry and determination
of the abundance of germination mediating enzymes provides useful
information for germination and outgrowth model development.
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Affiliation(s)
- Sacha K Stelder
- Molecular Biology & Microbial Food Safety, ‡Mass Spectrometry of Biomacromolecules, and §Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Celia Benito de Moya
- Molecular Biology & Microbial Food Safety, ‡Mass Spectrometry of Biomacromolecules, and §Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Huub C J Hoefsloot
- Molecular Biology & Microbial Food Safety, ‡Mass Spectrometry of Biomacromolecules, and §Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Leo J de Koning
- Molecular Biology & Microbial Food Safety, ‡Mass Spectrometry of Biomacromolecules, and §Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Stanley Brul
- Molecular Biology & Microbial Food Safety, ‡Mass Spectrometry of Biomacromolecules, and §Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Chris G de Koster
- Molecular Biology & Microbial Food Safety, ‡Mass Spectrometry of Biomacromolecules, and §Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
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17
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Korza G, Abini-Agbomson S, Setlow B, Shen A, Setlow P. Levels of L-malate and other low molecular weight metabolites in spores of Bacillus species and Clostridium difficile. PLoS One 2017; 12:e0182656. [PMID: 28850573 PMCID: PMC5574573 DOI: 10.1371/journal.pone.0182656] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 07/21/2017] [Indexed: 12/04/2022] Open
Abstract
Dormant spores of Bacillus species lack ATP and NADH and contain notable levels of only a few other common low mol wt energy reserves, including 3-phosphoglyceric acid (3PGA), and glutamic acid. Recently, Bacillus subtilis spores were reported to contain ~ 30 μmol of L-malate/g dry wt, which also could serve as an energy reserve. In present work, L-malate levels were determined in the core of dormant spores of B. subtilis, Bacillus cereus, Bacillus megaterium and Clostridium difficile, using both an enzymatic assay and 13C-NMR on extracts prepared by several different methods. These assays found that levels of L-malate in B. cereus and B. megaterium spores were ≤ 0.5 μmol/g dry wt, and ≤ 1 μmol/g dry wt in B. subtilis spores, and levels of L-lactate and pyruvate in B. megaterium and B. subtilis spores were < 0.5 μmol/g dry wt. Levels of L-malate in C. difficile spores were ≤ 1 μmol/g dry wt, while levels of 3PGA were ~ 7 μmol/g; the latter value was determined by 31P-NMR, and is in between the 3PGA levels in B. megaterium and B. subtilis spores determined previously. 13C-NMR analysis of spore extracts further showed that B. megaterium, B. subtilis and C. difficile contained significant levels of carbonate/bicarbonate in the spore core. Low mol wt carbon-containing small molecules present at > 3 μmol/g dry spores are: i) dipicolinic acid, carbonate/bicarbonate and 3PGA in B. megaterium, B. subtilis and C. difficile; ii) glutamate in B. megaterium and B. subtilis; iii) arginine in B. subtilis; and iv) at least one unidentified compound in all three species.
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Affiliation(s)
- George Korza
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States of America
| | - Stephen Abini-Agbomson
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States of America
| | - Barbara Setlow
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States of America
| | - Aimee Shen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, United States of America
| | - Peter Setlow
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, United States of America
- * E-mail:
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18
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Johnson CL, Moir A. Proteins YlaJ and YhcN contribute to the efficiency of spore germination in Bacillus subtilis. FEMS Microbiol Lett 2017; 364:3045907. [DOI: 10.1093/femsle/fnx047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 02/22/2017] [Indexed: 11/14/2022] Open
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19
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Li Q, Korza G, Setlow P. Killing the spores of
Bacillus
species by molecular iodine. J Appl Microbiol 2016; 122:54-64. [DOI: 10.1111/jam.13310] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 09/12/2016] [Accepted: 09/24/2016] [Indexed: 12/27/2022]
Affiliation(s)
- Q. Li
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
| | - G. Korza
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
| | - P. Setlow
- Department of Molecular Biology and Biophysics UConn Health Farmington CT USA
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20
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Donadio G, Lanzilli M, Sirec T, Ricca E, Isticato R. Localization of a red fluorescence protein adsorbed on wild type and mutant spores of Bacillus subtilis. Microb Cell Fact 2016; 15:153. [PMID: 27609116 PMCID: PMC5016992 DOI: 10.1186/s12934-016-0551-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/29/2016] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Bacterial spores have been proposed as vehicles to display heterologous proteins for the development of mucosal vaccines, biocatalysts, bioremediation and diagnostic tools. Two approaches have been developed to display proteins on the spore surface: a recombinant approach, based on the construction of gene fusions between DNA molecules coding for a spore surface protein (carrier) and for the heterologous protein to be displayed (passenger); and a non-recombinant approach based on spore adsorption, a spontaneous interaction between negatively charged, hydrophobic spores and purified proteins. The molecular details of spore adsorption have not been fully clarified yet. RESULTS We used the monomeric Red Fluorescent Protein (mRFP) of the coral Discosoma sp. and Bacillus subtilis spores of a wild type and an isogenic mutant strain lacking the CotH protein to clarify the adsorption process. Mutant spores, characterized by a strongly altered coat, were more efficient than wild type spores in adsorbing mRFP but the interaction was less stable and mRFP could be in part released by raising the pH of the spore suspension. A collection of isogenic strains carrying GFP fused to proteins restricted in different compartments of the B. subtilis spore was used to localize adsorbed mRFP molecules. In wild type spores mRFP infiltrated through crust and outer coat, localized in the inner coat and was not surface exposed. In mutant spores mRFP was present in all surface layers, inner, outer coat and crust and was exposed on the spore surface. CONCLUSIONS Our results indicate that different spores can be selected for different applications. Wild type spores are preferable when a very tight protein-spore interaction is needed, for example to develop reusable biocatalysts or bioremediation systems for field applications. cotH mutant spores are instead preferable when the heterologous protein has to be displayed on the spore surface or has to be released, as could be the case in mucosal delivery systems for antigens and drugs, respectively.
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Affiliation(s)
- Giuliana Donadio
- Department of Biology, Federico II University, via Cinthia-MSA, 80126 Naples, Italy
| | | | - Teja Sirec
- Department of Biology, Federico II University, via Cinthia-MSA, 80126 Naples, Italy
- School of Life Sciences, Gibbet Hill Campus, The University of Warwick, Coventry, CV4 7AL UK
| | - Ezio Ricca
- Department of Biology, Federico II University, via Cinthia-MSA, 80126 Naples, Italy
| | - Rachele Isticato
- Department of Biology, Federico II University, via Cinthia-MSA, 80126 Naples, Italy
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21
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Rao L, Liao X, Setlow P. Bacillus spore wet heat resistance and evidence for the role of an expanded osmoregulatory spore cortex. Lett Appl Microbiol 2016; 63:247-53. [PMID: 27424522 DOI: 10.1111/lam.12615] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 07/11/2016] [Accepted: 07/12/2016] [Indexed: 11/28/2022]
Abstract
UNLABELLED Previous work reported that decoated Bacillus cereus spores incubated in 4 mol l(-1) CaCl2 are killed at lower temperatures than spores in water. This wet heat sensitization was suggested to support a role for an osmoregulatory peptidoglycan cortex in spore cores' low water content, and their wet heat resistance. Current work has replicated this finding with spores of B. cereus, Bacillus megaterium and Bacillus subtilis. However, this work found that decoated spores apparently killed at 80°C in 4 mol l(-1) CaCl2 : (i) were recovered on plates containing lysozyme; (ii) lost no dipicolinic acid (DPA) and their inner membrane remained impermeable; (iii) released no DPA upon stimulation with nutrient germinants and could not complete germination; and (iv) released DPA relatively normally upon stimulation with dodecylamine. These results indicate that decoated spores treated with 80°C- 4 mol l(-1) CaCl2 are not dead, but some protein(s) essential for spore germination, most likely germinant receptors, are inactivated by this treatment. Thus, the original finding does not support a role for an osmoregulatory cortex in spore wet heat resistance. SIGNIFICANCE AND IMPACT OF THE STUDY Bacillus spores' low core water content is a major factor in their wet heat resistance. One suggested mechanism for achieving low spore core water content is osmoregulated expansion of spores' peptidoglycan cortex. Evidence for this mechanism includes a report that decoated Bacillus cereus spores incubated in 4 mol l(-1) CaCl2 exhibit drastically reduced heat resistance. The current work shows that this heat sensitization of decoated spores of three Bacillus species is most likely due to inactivation of some crucial spore germination protein(s), since while treated spores appear dead, their apparent low viability is rescued by triggering spore germination with lysozyme.
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Affiliation(s)
- L Rao
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China.,National Engineering Research Center for Fruit and Vegetable Processing, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing, China.,Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, USA
| | - X Liao
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China.,National Engineering Research Center for Fruit and Vegetable Processing, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing, China
| | - P Setlow
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT, USA.
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Zheng L, Abhyankar W, Ouwerling N, Dekker HL, van Veen H, van der Wel NN, Roseboom W, de Koning LJ, Brul S, de Koster CG. Bacillus subtilis Spore Inner Membrane Proteome. J Proteome Res 2016; 15:585-94. [PMID: 26731423 DOI: 10.1021/acs.jproteome.5b00976] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The endospore is the dormant form of Bacillus subtilis and many other Firmicutes. By sporulation, these spore formers can survive very harsh physical and chemical conditions. Yet, they need to go through germination to return to their growing form. The spore inner membrane (IM) has been shown to play an essential role in triggering the initiation of germination. In this study, we isolated the IM of bacterial spores, in parallel with the isolation of the membrane of vegetative cells. With the use of GeLC-MS/MS, over 900 proteins were identified from the B. subtilis spore IM preparations. By bioinformatics-based membrane protein predictions, ca. one-third could be predicted to be membrane-localized. A large number of unique proteins as well as proteins common to the two membrane proteomes were identified. In addition to previously known IM proteins, a number of IM proteins were newly identified, at least some of which are likely to provide new insights into IM physiology, unveiling proteins putatively involved in spore germination machinery and hence putative germination inhibition targets.
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Affiliation(s)
| | | | | | | | - Henk van Veen
- Electron Microscopy Centre Amsterdam, Department of Cell Biology and Histology, Academic Medical Center , 1105 AZ Amsterdam, The Netherlands
| | - Nicole N van der Wel
- Electron Microscopy Centre Amsterdam, Department of Cell Biology and Histology, Academic Medical Center , 1105 AZ Amsterdam, The Netherlands
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Setlow B, Korza G, Blatt KM, Fey JP, Setlow P. Mechanism of Bacillus subtilis spore inactivation by and resistance to supercritical CO2 plus peracetic acid. J Appl Microbiol 2016; 120:57-69. [PMID: 26535794 PMCID: PMC4715516 DOI: 10.1111/jam.12995] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 10/22/2015] [Accepted: 10/27/2015] [Indexed: 10/22/2022]
Abstract
AIMS Determine how supercritical CO2 (scCO2 ) plus peracetic acid (PAA) inactivates Bacillus subtilis spores, factors important in spore resistance to scCO2 -PAA, and if spores inactivated by scCO2 -PAA are truly dead. METHODS AND RESULTS Spores of wild-type B. subtilis and isogenic mutants lacking spore protective proteins were treated with scCO2 -PAA in liquid or dry at 35°C. Wild-type wet spores (aqueous suspension) were more susceptible than dry spores. Treated spores were examined for viability (and were truly dead), dipicolinic acid (DPA), mutations, permeability to nucleic acid stains, germination under different conditions, energy metabolism and outgrowth. ScCO2 -PAA-inactivated spores retained DPA, and survivors had no notable DNA damage. However, DPA was released from inactivated spores at a normally innocuous temperature (85°C), and colony formation from treated spores was salt sensitive. The inactivated spores germinated but did not outgrow, and these germinated spores had altered plasma membrane permeability and defective energy metabolism. Wet or dry coat-defective spores had increased scCO2 -PAA sensitivity, and dry spores but not wet spores lacking DNA protective proteins were more scCO2 -PAA sensitive. CONCLUSIONS These findings suggest that scCO2 -PAA inactivates spores by damaging spores' inner membrane. The spore coat provided scCO2 -PAA resistance for both wet and dry spores. DNA protective proteins provided scCO2 -PAA resistance only for dry spores. SIGNIFICANCE AND IMPACT OF THE STUDY These results provide information on mechanisms of spore inactivation of and resistance to scCO2 -PAA, an agent with increasing use in sterilization applications.
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Affiliation(s)
- Barbara Setlow
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030-3305 USA
| | - George Korza
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030-3305 USA
| | | | | | - Peter Setlow
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030-3305 USA
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Abstract
Bacterial spores, despite being metabolically dormant, possess the remarkable capacity to detect nutrients and other molecules in their environment through a biochemical sensory apparatus that can trigger spore germination, allowing the return to vegetative growth within minutes of exposure of germinants. We demonstrate here that bacterial spores of multiple species retain memory of transient exposures to germinant stimuli that can result in altered responses to subsequent exposure. The magnitude and decay of these memory effects depend on the pulse duration as well as on the separation time, incubation temperature, and pH values between the pulses. Spores of Bacillus species germinate in response to nutrients that interact with germinant receptors (GRs) in the spore’s inner membrane, with different nutrient types acting on different receptors. In our experiments, B. subtilis spores display memory when the first and second germinant pulses target different receptors, suggesting that some components of spore memory are downstream of GRs. Furthermore, nonnutrient germinants, which do not require GRs, exhibit memory either alone or in combination with nutrient germinants, and memory of nonnutrient stimulation is found to be more persistent than that induced by GR-dependent stimuli. Spores of B. cereus and Clostridium difficile also exhibit germination memory, suggesting that memory may be a general property of bacterial spores. These observations along with experiments involving strains with mutations in various germination proteins suggest a model in which memory is stored primarily in the metastable states of SpoVA proteins, which comprise a channel for release of dipicolinic acid, a major early event in spore germination. Cellular memory is defined as a sustained response to a transient environmental stimulus, and yet its generation and storage have not been described in bacterial spores. We demonstrate here that bacterial spores of multiple species retain memory of transient exposures to germinant stimuli that can result in altered responses to subsequent exposure. Memory was induced by activation of germinant receptors (GRs) or by GR-independent germinants and was accessed by both GR-dependent and GR-independent germinants. Analysis of effects on memory of exposure to GR-dependent and GR-independent germinants as well as in spores lacking various germination proteins suggests a model in which memory is stored primarily in metastable states of SpoVA proteins which comprise a channel for release of spore dipicolinic acid. Spore memory can also significantly reduce the concentration of nutrient germinants necessary to trigger germination, and this may be used to respond to low levels of nutrient germinants.
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Location and stoichiometry of the protease CspB and the cortex-lytic enzyme SleC in Clostridium perfringens spores. Food Microbiol 2015; 50:83-7. [PMID: 25998819 DOI: 10.1016/j.fm.2015.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 11/22/2022]
Abstract
The protease CspB and the cortex-lytic enzyme SleC are essential for peptoglycan cortex hydrolysis during germination of spores of the Clostridium perfringens food poisoning isolate SM101. In this study, Western blot analyses were used to demonstrate that CspB and SleC are present exclusively in the C. perfringens SM101 spore coat layer fraction and absent in the lysate from decoated spores and from the purified inner spore membrane. These results indicate why decoating treatments greatly reduce both germination and apparent viability of C. perfringens spores in the absence of an exogenous lytic enzyme. In addition, quantitative Western blot analyses showed that there are approximately 2000 and 130,000 molecules of CspB and pro-SleC, respectively, per C. perfringens SM101 spore, consistent with CspB's role in acting catalytically on pro-SleC to convert this zymogen to the active enzyme.
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Role of YpeB in cortex hydrolysis during germination of Bacillus anthracis spores. J Bacteriol 2014; 196:3399-409. [PMID: 25022853 DOI: 10.1128/jb.01899-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The infectious agent of the disease anthrax is the spore of Bacillus anthracis. Bacterial spores are extremely resistant to environmental stresses, which greatly hinders spore decontamination efforts. The spore cortex, a thick layer of modified peptidoglycan, contributes to spore dormancy and resistance by maintaining the low water content of the spore core. The cortex is degraded by germination-specific lytic enzymes (GSLEs) during spore germination, rendering the cells vulnerable to common disinfection techniques. This study investigates the relationship between SleB, a GSLE in B. anthracis, and YpeB, a protein necessary for SleB stability and function. The results indicate that ΔsleB and ΔypeB spores exhibit similar germination phenotypes and that the two proteins have a strict codependency for their incorporation into the dormant spore. In the absence of its partner protein, SleB or YpeB is proteolytically degraded soon after expression during sporulation, rather than escaping the developing spore. The three PepSY domains of YpeB were examined for their roles in the interaction with SleB. YpeB truncation mutants illustrate the necessity of a region beyond the first PepSY domain for SleB stability. Furthermore, site-directed mutagenesis of highly conserved residues within the PepSY domains resulted in germination defects corresponding to reduced levels of both SleB and YpeB in the mutant spores. These results identify residues involved in the stability of both proteins and reiterate their codependent relationship. It is hoped that the study of GSLEs and interacting proteins will lead to the use of GSLEs as targets for efficient activation of spore germination and facilitation of spore cleanup.
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Involvement of alanine racemase in germination of Bacillus cereus spores lacking an intact exosporium. Arch Microbiol 2013; 196:79-85. [PMID: 24346000 DOI: 10.1007/s00203-013-0946-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 11/29/2013] [Accepted: 12/04/2013] [Indexed: 10/25/2022]
Abstract
The L-alanine mediated germination of food isolated Bacillus cereus DSA 1 spores, which lacked an intact exosporium, increased in the presence of D-cycloserine (DCS), which is an alanine racemase (Alr) inhibitor, reflecting the activity of the Alr enzyme, capable of converting L-alanine to the germination inhibitor D-alanine. Proteomic analysis of the alkaline extracts of the spore proteins, which include exosporium and coat proteins, confirmed that Alr was present in the B. cereus DSA 1 spores and matched to that encoded by B. cereus ATCC 14579, whose spore germination was strongly affected by the block of conversion of L- to D-alanine. Unlike ATCC 14579 spores, L-alanine germination of B. cereus DSA 1 spores was not affected by the preincubation with DCS, suggesting a lack of restriction in the reactant accessibility.
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Abhyankar W, Hossain AH, Djajasaputra A, Permpoonpattana P, Ter Beek A, Dekker HL, Cutting SM, Brul S, de Koning LJ, de Koster CG. In Pursuit of Protein Targets: Proteomic Characterization of Bacterial Spore Outer Layers. J Proteome Res 2013; 12:4507-21. [DOI: 10.1021/pr4005629] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | - Patima Permpoonpattana
- School
of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
| | | | | | - Simon M. Cutting
- School
of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
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Zhou T, Dong Z, Setlow P, Li YQ. Kinetics of germination of individual spores of Geobacillus stearothermophilus as measured by raman spectroscopy and differential interference contrast microscopy. PLoS One 2013; 8:e74987. [PMID: 24058645 PMCID: PMC3772816 DOI: 10.1371/journal.pone.0074987] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 08/07/2013] [Indexed: 11/19/2022] Open
Abstract
Geobacillus stearothermophilus is a gram-positive, thermophilic bacterium, spores of which are very heat resistant. Raman spectroscopy and differential interference contrast microscopy were used to monitor the kinetics of germination of individual spores of G. stearothermophilus at different temperatures, and major conclusions from this work were as follows. 1) The CaDPA level of individual G. stearothermophilus spores was similar to that of Bacillus spores. However, the Raman spectra of protein amide bands suggested there are differences in protein structure in spores of G. stearothermophilus and Bacillus species. 2) During nutrient germination of G. stearothermophilus spores, CaDPA was released beginning after a lag time (Tlag) between addition of nutrient germinants and initiation of CaDPA release. CaDPA release was complete at Trelease, and ΔTrelease (Trelease – Tlag) was 1–2 min. 3) Activation by heat or sodium nitrite was essential for efficient nutrient germination of G. stearothermophilus spores, primarily by decreasing Tlag values. 4) Values of Tlag and Trelease were heterogeneous among individual spores, but ΔTrelease values were relatively constant. 5) Temperature had major effects on nutrient germination of G. stearothermophilus spores, as at temperatures below 65°C, average Tlag values increased significantly. 6) G. stearothermophilus spore germination with exogenous CaDPA or dodecylamine was fastest at 65°C, with longer Tlag values at lower temperatures. 7) Decoating of G. stearothermophilus spores slowed nutrient germination slightly and CaDPA germination significantly, but increased dodecylamine germination markedly. These results indicate that the dynamics and heterogeneity of the germination of individual G. stearothermophilus spores are generally similar to that of Bacillus species.
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Affiliation(s)
- Tingting Zhou
- Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Department of Physics, East Carolina University, Greenville, North Carolina, United States of America
| | - Zhiyang Dong
- Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Peter Setlow
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Yong-qing Li
- Department of Physics, East Carolina University, Greenville, North Carolina, United States of America
- * E-mail:
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The Clostridium perfringens germinant receptor protein GerKC is located in the spore inner membrane and is crucial for spore germination. J Bacteriol 2013; 195:5084-91. [PMID: 24013629 DOI: 10.1128/jb.00901-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Gram-positive, anaerobic, spore-forming bacterium Clostridium perfringens causes a variety of diseases in both humans and animals, and spore germination is thought to be the first stage of C. perfringens infection. Previous studies have indicated that the germinant receptor (GR) proteins encoded by the bicistronic gerKA-gerKC operon as well as the proteins encoded by the gerKB and gerAA genes are required for normal germination of C. perfringens spores. We now report the individual role of these GR proteins by analyzing the germination of strains carrying mutations in gerKA, gerKC, or both gerKB and gerAA. Western blot analysis was also used to determine the location and numbers of GerKC proteins in spores. Conclusions from this work include the following: (i) gerKC mutant spores germinate extremely poorly with KCl, l-asparagine, a mixture of asparagine and KCl, or NaPi; (ii) gerKC spores germinate significantly more slowly than wild-type and other GR mutant spores with a 1:1 chelate of Ca(2+) and dipicolinic acid and very slightly more slowly with dodecylamine; (iii) the germination defects in gerKC spores are largely restored by expressing the wild-type gerKA-gerKC operon in trans; (iv) GerKC is required for the spores' viability, almost certainly because of the gerKC spores' poor germination; and (v) GerKC is located in the spores' inner membrane, with ∼250 molecules/spore. Collectively, these results indicate that GerKC is the main GR protein required for nutrient and nonnutrient germination of spores of C. perfringens food-poisoning isolates.
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Numbers of individual nutrient germinant receptors and other germination proteins in spores of Bacillus subtilis. J Bacteriol 2013; 195:3575-82. [PMID: 23749970 DOI: 10.1128/jb.00377-13] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Germination of dormant Bacillus subtilis spores with specific nutrient germinants is dependent on a number of inner membrane (IM) proteins, including (i) the GerA, GerB, and GerK germinant receptors (GRs) that respond to nutrient germinants; (ii) the GerD protein, essential for optimal GR function; and (iii) SpoVA proteins, essential for the release of the spore-specific molecule dipicolinic acid (DPA) during spore germination. Levels of GR A and C subunit proteins, GerD, and SpoVAD in wild-type spores were determined by Western blot analysis of spore fractions or total disrupted spores by comparison with known amounts of purified proteins. Surprisingly, after disruption of decoated B. subtilis spores with lysozyme and fractionation, ∼90% of IM fatty acids and GR subunits remained with the spores' insoluble integument fraction, indicating that yields of purified IM are low. The total lysate from disrupted wild-type spores contained ∼2,500 total GRs/spore: GerAA and GerAC subunits each at ∼1,100 molecules/spore and GerBC and GerKA subunits each at ∼700 molecules/spore. Levels of the GerBA subunit determined previously were also predicted to be ∼700 molecules/spore. These results indicate that the A/C subunit stoichiometry in GRs is most likely 1:1, with GerA being the most abundant GR. GerD and SpoVAD levels were ∼3,500 and ∼6,500 molecules/spore, respectively. These values will be helpful in formulating mathematic models of spore germination kinetics as well as setting lower limits on the size of the GR-GerD complex in the spores' IM, termed the germinosome.
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Topology and accessibility of germination proteins in the Bacillus subtilis spore inner membrane. J Bacteriol 2013; 195:1484-91. [PMID: 23335419 DOI: 10.1128/jb.02262-12] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Access to a membrane-impermeant biotinylation reagent as well as protease sensitivity was used to determine germination proteins' topology in the inner membrane (IM) of decoated dormant spores and intact germinated Bacillus subtilis spores. The proteins examined were four nutrient germinant receptor (GR) subunits, the GerD protein, essential for normal GR-dependent spore germination, the SpoVAD protein, essential for dipicolinic acid movement across the IM, the SleB cortex-lytic enzyme, and the YpeB protein, essential for SleB assembly in spores, as well as green fluorescent protein (GFP) in the spore core. GerD and SpoVAD as well as GFP in the spore were not biotinylated in decoated dormant spores. However, GR subunits, SleB, and YpeB were biotinylated 4 to 36% in decoated dormant spores, although these levels were not increased by higher biotinylation reagent concentrations or longer reaction times. In contrast, the germination proteins were largely biotinylated in germinated spores, although GFP was not. All of the germination proteins in the germinated spore's IM, but not spore core GFP, were largely sensitive to an exogenous protease. These results, coupled with predicted or experimentally determined structural data, indicate that (i) these germination proteins are at least partially and in some cases completely on the outer surface of the spore's IM and (ii) there is significant reorganization of these germination proteins' structure or environment in the IM during spore germination.
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Huo Z, Zhang N, Raza W, Huang X, Yong X, Liu Y, Wang D, Li S, Shen Q, Zhang R. Comparison of the spores of Paenibacillus polymyxa prepared at different temperatures. Biotechnol Lett 2012; 34:925-33. [DOI: 10.1007/s10529-012-0853-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Accepted: 01/05/2012] [Indexed: 10/14/2022]
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Efficient inhibition of germination of coat-deficient bacterial spores by multivalent metal cations, including terbium (Tb³+). Appl Environ Microbiol 2011; 77:5536-9. [PMID: 21685163 DOI: 10.1128/aem.00577-11] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Release of dipicolinic acid (DPA) and its fluorescence with terbium (Tb(3+)) allow rapid measurement of the germination and viability of spores of Bacillus and Clostridium species. However, germination of coat-deficient Bacillus spores was strongly inhibited by Tb(3+) and some other multivalent cations. Tb(3+) also inhibited germination of coat-deficient Clostridium perfringens spores.
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35
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Extremely variable conservation of γ-type small, acid-soluble proteins from spores of some species in the bacterial order Bacillales. J Bacteriol 2011; 193:1884-92. [PMID: 21317325 DOI: 10.1128/jb.00018-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
γ-Type small, acid-soluble spore proteins (SASP) are the most abundant proteins in spores of at least some members of the bacterial order Bacillales, yet they remain an enigma from both functional and phylogenetic perspectives. Current work has shown that the γ-type SASP or their coding genes (sspE genes) are present in most spore-forming members of Bacillales, including at least some members of the Paenibacillus genus, although they are apparently absent from Clostridiales species. We have applied a new method of searching for sspE genes, which now appear to also be absent from a clade of Bacillales species that includes Alicyclobacillus acidocaldarius and Bacillus tusciae. In addition, no γ-type SASP were found in A. acidocaldarius spores, although several of the DNA-binding α/β-type SASP were present. These findings have elucidated the phylogenetic origin of the sspE gene, and this may help in determining the precise function of γ-type SASP.
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Localization of proteins to different layers and regions of Bacillus subtilis spore coats. J Bacteriol 2009; 192:518-24. [PMID: 19933362 DOI: 10.1128/jb.01103-09] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial spores are encased in a multilayered proteinaceous shell known as the coat. In Bacillus subtilis, over 50 proteins are involved in spore coat assembly but the locations of these proteins in the spore coat are poorly understood. Here, we describe methods to estimate the positions of protein fusions to fluorescent proteins in the spore coat by using fluorescence microscopy. Our investigation suggested that CotD, CotF, CotT, GerQ, YaaH, YeeK, YmaG, YsnD, and YxeE are present in the inner coat and that CotA, CotB, CotC, and YtxO reside in the outer coat. In addition, CotZ and CgeA appeared in the outermost layer of the spore coat and were more abundant at the mother cell proximal pole of the forespore, whereas CotA and CotC were more abundant at the mother cell distal pole of the forespore. These polar localizations were observed both in sporangia prior to the release of the forespore from the mother cell and in mature spores after release. Moreover, CotB was observed at the middle of the spore as a ring- or spiral-like structure. Formation of this structure required cotG expression. Thus, we conclude not only that the spore coat is a multilayered assembly but also that it exhibits uneven spatial distribution of particular proteins.
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Superdormant spores of Bacillus species have elevated wet-heat resistance and temperature requirements for heat activation. J Bacteriol 2009; 191:5584-91. [PMID: 19592590 DOI: 10.1128/jb.00736-09] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Purified superdormant spores of Bacillus cereus, B. megaterium, and B. subtilis isolated after optimal heat activation of dormant spores and subsequent germination with inosine, d-glucose, or l-valine, respectively, germinate very poorly with the original germinants used to remove dormant spores from spore populations, thus allowing isolation of the superdormant spores, and even with alternate germinants. However, these superdormant spores exhibited significant germination with the original or alternate germinants if the spores were heat activated at temperatures 8 to 15 degrees C higher than the optimal temperatures for the original dormant spores, although the levels of superdormant spore germination were not as great as those of dormant spores. Use of mixtures of original and alternate germinants lowered the heat activation temperature optima for both dormant and superdormant spores. The superdormant spores had higher wet-heat resistance and lower core water content than the original dormant spore populations, and the environment of dipicolinic acid in the core of superdormant spores as determined by Raman spectroscopy of individual spores differed from that in dormant spores. These results provide new information about the germination, heat activation optima, and wet-heat resistance of superdormant spores and the heterogeneity in these properties between individual members of dormant spore populations.
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Griffiths K, Setlow P. Effects of modification of membrane lipid composition onBacillus subtilissporulation and spore properties. J Appl Microbiol 2009; 106:2064-78. [DOI: 10.1111/j.1365-2672.2009.04176.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Magge A, Setlow B, Cowan AE, Setlow P. Analysis of dye binding by and membrane potential in spores of Bacillus species. J Appl Microbiol 2009; 106:814-24. [PMID: 19187156 PMCID: PMC2661013 DOI: 10.1111/j.1365-2672.2008.04048.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To determine roles of coats in staining Bacillus subtilis spores, and whether spores have membrane potential. METHODS AND RESULTS Staining by four dyes and autofluorescence of B. subtilis spores that lack some (cotE, gerE) or most (cotE gerE) coat protein was measured. Wild-type, cotE and gerE spores autofluorescenced and bound dyes, but cotE gerE spores did not autofluorescence and were stained only by two dyes. A membrane potential-sensitive dye DiOC6(3) bound to dormant Bacillus megaterium and B. subtilis spores. While this binding was abolished by the protonophore FCCP, DiOC6(3) bound to heat-killed spores, but not to dormant B. subtilis cotE gerE spores. However, DiOC6(3) bound well to all germinated spores. CONCLUSIONS The autofluorescence of dormant B. subtilis spores and the binding of some dyes are due to the coat. There is no membrane potential in dormant Bacillus spores, although membrane potential is generated when spores germinate. SIGNIFICANCE AND IMPACT OF THE STUDY The elimination of the autofluorescence of B. subtilis spores may allow assessment of the location of low abundance spore proteins using fluorescent reporter technology. The dormant spore's lack of membrane potential may allow tests of spore viability by assessing membrane potential in germinating spores.
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Affiliation(s)
- A Magge
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center Farmington, CT 06030-3305, USA
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Expression of yeeK during Bacillus subtilis sporulation and localization of YeeK to the inner spore coat using fluorescence microscopy. J Bacteriol 2008; 191:1220-9. [PMID: 19060142 DOI: 10.1128/jb.01269-08] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The yeeK gene of Bacillus subtilis is predicted to encode a protein of 145 amino acids composed of 28% glycine, 23% histidine, and 12% tyrosine residues. Previous studies were unable to detect YeeK in wild-type spores; however, the 18-kDa YeeK polypeptide has been identified in yabG mutant spores. In this study, we analyze the expression and localization of YeeK to explore the relationship between YeeK and YabG. Northern hybridization analysis of wild-type RNA indicated that transcription of the yeeK gene, which was initiated 5 h after the onset of sporulation, was dependent on a SigK-containing RNA polymerase and the GerE protein. Genetic disruption of yeeK did not impair vegetative growth, development of resistant spores, or germination. Fluorescent microscopy of in-frame fusions of YeeK with green fluorescent protein (YeeK-GFP) and red fluorescent protein (YeeK-RFP) confirmed that YeeK assembles into the spore integument. CotE, SafA, and SpoVID were required for the proper localization of YeeK-GFP. Comparative analysis of YeeK-RFP and an in-frame GFP fusion of YabG indicated that YeeK colocalized with YabG in the spore coat. This is the first use of fluorescent proteins to show localization to different layers of the spore coat. Immunoblotting with anti-GFP antiserum indicated that YeeK-GFP was primarily synthesized as a 44-kDa molecule, which was then digested into a 29-kDa fragment that corresponded to the molecular size of GFP in wild-type spores. In contrast, a minimal amount of 44-kDa YeeK-GFP was digested in yabG mutant spores. Our findings demonstrate that YeeK is guided into the spore coat by CotE, SafA, and SpoVID. We conclude that YabG is directly or indirectly involved in the digestion of YeeK.
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41
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Abstract
Spores of Bacillus subtilis have a thick outer layer of relatively insoluble protein called the coat, which protects spores against a number of treatments and may also play roles in spore germination. However, elucidation of precise roles of the coat in spore properties has been hampered by the inability to prepare spores lacking all or most coat material. In this work, we show that spores of a strain with mutations in both the cotE and gerE genes, which encode proteins involved in coat assembly and expression of genes encoding coat proteins, respectively, lack most extractable coat protein as seen by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, as well as the great majority of the coat as seen by atomic force microscopy. However, the cotE gerE spores did retain a thin layer of insoluble coat material that was most easily seen by microscopy following digestion of these spores with lysozyme. These severely coat-deficient spores germinated relatively normally with nutrients and even better with dodecylamine but not with a 1:1 chelate of Ca(2+) and dipicolinic acid. These spores were also quite resistant to wet heat, to mechanical disruption, and to treatment with detergents at an elevated temperature and pH but were exquisitely sensitive to killing by sodium hypochlorite. These results provide new insight into the role of the coat layer in spore properties.
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Rose R, Setlow B, Monroe A, Mallozzi M, Driks A, Setlow P. Comparison of the properties of Bacillus subtilis spores made in liquid or on agar plates. J Appl Microbiol 2007; 103:691-9. [PMID: 17714403 DOI: 10.1111/j.1365-2672.2007.03297.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS To compare the properties of the spores of Bacillus subtilis prepared in liquid and on plates. METHODS AND RESULTS The spores of B. subtilis were prepared at 37 degrees C using a nutrient exhaustion medium either in liquid or on agar plates. The levels of core water, dipicolinic acid (DPA) and small, acid-soluble spore proteins (SASP) were essentially identical in spores made in liquid or on plates. Spores prepared in liquid were killed approximately threefold more rapidly at 90 degrees C in water than the spores prepared on plates, and the spores prepared in liquid were more sensitive to nitrous acid and a diluted stable superoxidized water. Spores prepared in liquid also germinated more rapidly with several agents than those prepared on plates. Pellets of spores prepared on plates were darker than spores prepared in liquid, and spores prepared in liquid had more readily extracted coat protein. However, there were no major differences in the relative levels of individual coat proteins or the cross-linking of the coat protein GerQ in the two types of spores, although the inner membrane of spores prepared on plates had a higher ratio of anteiso- to iso-fatty acids. CONCLUSIONS The preparation in liquid yielded spores with some different properties than those made on agar plates. Spores made in liquid had lower resistance to heat and several chemicals, and germinated more readily with several agents. There were also differences in the composition of the inner membrane of spores prepared under these two conditions. However, there were no major differences in the levels of DPA, core water, SASP and individual coat proteins or the cross-linking of a coat protein in spores made in liquid and on plates. SIGNIFICANCE AND IMPACT OF THE STUDY This work demonstrates that the preparation method can affect the resistance and germination properties of bacterial spores, even if an identical medium and temperature are used. Evidence was also obtained consistent with the role of the inner membrane in spore resistance and germination, and that some factor in addition to core water, DPA and SASP content plays a role in spore resistance to wet heat.
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Affiliation(s)
- R Rose
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA
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Vepachedu VR, Setlow P. Role of SpoVA proteins in release of dipicolinic acid during germination of Bacillus subtilis spores triggered by dodecylamine or lysozyme. J Bacteriol 2006; 189:1565-72. [PMID: 17158659 PMCID: PMC1855772 DOI: 10.1128/jb.01613-06] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The release of dipicolinic acid (DPA) during the germination of Bacillus subtilis spores by the cationic surfactant dodecylamine exhibited a pH optimum of approximately 9 and a temperature optimum of 60 degrees C. DPA release during dodecylamine germination of B. subtilis spores with fourfold-elevated levels of the SpoVA proteins that have been suggested to be involved in the release of DPA during nutrient germination was about fourfold faster than DPA release during dodecylamine germination of wild-type spores and was inhibited by HgCl(2). Spores carrying temperature-sensitive mutants in the spoVA operon were also temperature sensitive in DPA release during dodecylamine germination as well as in lysozyme germination of decoated spores. In addition to DPA, dodecylamine triggered the release of amounts of Ca(2+) almost equivalent to those of DPA, and at least one other abundant spore small molecule, glutamic acid, was released in parallel with Ca(2+) and DPA. These data indicate that (i) dodecylamine triggers spore germination by opening a channel in the inner membrane for Ca(2+)-DPA and other small molecules, (ii) this channel is composed at least in part of proteins, and (iii) SpoVA proteins are involved in the release of Ca(2+)-DPA and other small molecules during spore germination, perhaps by being a part of a channel in the spore's inner membrane.
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Affiliation(s)
- Venkata Ramana Vepachedu
- Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA
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Paul M, Atluri S, Setlow B, Setlow P. Mechanisms of killing of spores of Bacillus subtilis by dimethyldioxirane. J Appl Microbiol 2006; 101:1161-8. [PMID: 17040240 DOI: 10.1111/j.1365-2672.2006.03000.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS To determine the mechanisms of Bacillus subtilis spore resistance to and killing by a novel sporicide, dimethyldioxirane (DMDO) that was generated in situ from acetone and potassium peroxymonosulfate at neutral pH. METHODS AND RESULTS Spores of B. subtilis were effectively killed by DMDO. Rates of killing by DMDO of spores lacking most DNA protective alpha/beta-type small, acid-soluble spore proteins (alpha- beta- spores) or the major DNA repair protein, RecA, were very similar to that of wild-type spore killing. Survivors of wild-type and alpha- beta- spores treated with DMDO also exhibited no increase in mutations. Spores lacking much coat protein due either to mutation or chemical decoating were much more sensitive to DMDO than were wild-type spores, but were more resistant than growing cells. Wild-type spores killed with this reagent retained their large pool of dipicolinic acid (DPA), and the survivors of spores treated with DMDO were sensitized to wet heat. The DMDO-killed spores germinated with nutrients, albeit more slowly than untreated spores, but germinated faster than untreated spores with dodecylamine. The killed spores were also germinated by very high pressures and by lysozyme treatment in hypertonic medium, but many of these spores lysed shortly after their germination, and none of these treatments were able to revive the DMDO-killed spores. CONCLUSIONS DMDO is an effective reagent for killing B. subtilis spores. The spore coat is a major factor in spore resistance to DMDO, which does not kill spores by DNA damage or by inactivating some component needed for spore germination. Rather, this reagent appears to kill spores by damaging the spore's inner membrane in some fashion. SIGNIFICANCE AND IMPACT OF THE STUDY This work demonstrates that DMDO is an effective decontaminant for spores of Bacillus species that can work under mild conditions, and the killed spores cannot be revived. Evidence has also been obtained on the mechanisms of spore resistance to and killing by this reagent.
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Affiliation(s)
- M Paul
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA
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Paul M, Setlow B, Setlow P. Killing of spores of Bacillus subtilis by tert-butyl hydroperoxide plus a TAML�activator. J Appl Microbiol 2006; 102:954-62. [PMID: 17381738 DOI: 10.1111/j.1365-2672.2006.03162.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To determine the effectiveness of tert-butyl hydroperoxide (tBHP) plus the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) and a tetra-amido macrocyclic ligand (TAML) activator in killing spores of Bacillus subtilis and the mechanisms of spore resistance to and killing by this reagent. METHODS AND RESULTS Killing of spores of B. subtilis by tBHP was greatly stimulated by the optimum ratio of concentrations of a TAML activator (1.7 micromol l(-1)) to tBHP (4.4%, vol/vol) plus a low level (270 mg l(-1)) of CTAB. Rates of killing of spores lacking most DNA protective alpha/beta-type small, acid-soluble spore proteins (alpha(-)beta(-) spores) or the major DNA repair protein, RecA, by tBHP plus CTAB and a TAML activator were essentially identical to that of wild-type spore killing. Survivors of wild-type and alpha(-)beta(-) spores treated with tBHP plus CTAB and a TAML activator also exhibited no increase in mutations. Spores lacking much coat protein either because of mutation or chemical decoating were much more sensitive to this reagent than were wild-type spores, but were more resistant than growing cells. Wild-type spores killed with this reagent retained their large pool of dipicolinic acid (DPA), and the survivors of spores treated with this reagent were sensitized to wet heat. The tBHP plus CTAB and TAML activator-killed spores germinated with nutrients, albeit more slowly than untreated spores, but germinated faster than untreated spores with dodecylamine. The killed spores were also germinated by application of 150 and 500 megaPascals of pressure for 15 min and by lysozyme treatment in hypertonic medium, but these spores lysed shortly after their germination. CONCLUSIONS The combination of tBHP plus CTAB and a TAML activator is effective in killing B. subtilis spores. The spore coat is a major factor in spore resistance to this reagent system, which does not kill spores by DNA damage or by inactivating some component needed for spore germination. Rather, this reagent system appears to kill spores by damaging the spore's inner membrane in some fashion. SIGNIFICANCE AND IMPACT OF THE STUDY This work demonstrates that tBHP plus CTAB and a TAML activator is an effective and mild decontaminant for spores of Bacillus species. Evidence has also been obtained on the mechanisms of spore resistance to and killing by this reagent system.
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Affiliation(s)
- M Paul
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA
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Setlow B, Atluri S, Kitchel R, Koziol-Dube K, Setlow P. Role of dipicolinic acid in resistance and stability of spores of Bacillus subtilis with or without DNA-protective alpha/beta-type small acid-soluble proteins. J Bacteriol 2006; 188:3740-7. [PMID: 16707666 PMCID: PMC1482921 DOI: 10.1128/jb.00212-06] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dipicolinic acid (DPA) comprises approximately 10% of the dry weight of spores of Bacillus species. Although DPA has long been implicated in spore resistance to wet heat and spore stability, definitive evidence on the role of this abundant molecule in spore properties has generally been lacking. Bacillus subtilis strain FB122 (sleB spoVF) produced very stable spores that lacked DPA, and sporulation of this strain with DPA yielded spores with nearly normal DPA levels. DPA-replete and DPA-less FB122 spores had similar levels of the DNA protective alpha/beta-type small acid-soluble spore proteins (SASP), but the DPA-less spores lacked SASP-gamma. The DPA-less FB122 spores exhibited similar UV resistance to the DPA-replete spores but had lower resistance to wet heat, dry heat, hydrogen peroxide, and desiccation. Neither wet heat nor hydrogen peroxide killed the DPA-less spores by DNA damage, but desiccation did. The inability to synthesize both DPA and most alpha/beta-type SASP in strain PS3664 (sspA sspB sleB spoVF) resulted in spores that lost viability during sporulation, at least in part due to DNA damage. DPA-less PS3664 spores were more sensitive to wet heat than either DPA-less FB122 spores or DPA-replete PS3664 spores, and the latter also retained viability during sporulation. These and previous results indicate that, in addition to alpha/beta-type SASP, DPA also is extremely important in spore resistance and stability and, further, that DPA has some specific role(s) in protecting spore DNA from damage. Specific roles for DPA in protecting spore DNA against damage may well have been a major driving force for the spore's accumulation of the high levels of this small molecule.
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Affiliation(s)
- Barbara Setlow
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA.
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Igarashi T, Setlow P. Transcription of the Bacillus subtilis gerK operon, which encodes a spore germinant receptor, and comparison with that of operons encoding other germinant receptors. J Bacteriol 2006; 188:4131-6. [PMID: 16707705 PMCID: PMC1482912 DOI: 10.1128/jb.00265-06] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gerA, gerB, and gerK operons, which encode germinant receptors in spores of Bacillus subtilis, were transcribed only in sporulation, and their mRNA levels peaked initially approximately 3 h before the initiation of accumulation of the spore's dipicolinic acid. After a rapid fall, levels of these mRNAs peaked again approximately 5 h later. In one wild-type strain (PS832), gerA mRNA was the most abundant, with levels of gerB and gerK mRNAs approximately 50% of that of gerA mRNA, whereas gerB mRNA was the most abundant in another wild-type strain (PY79). The synthesis of gerK mRNA in sporulation was abolished by loss of the forespore-specific RNA polymerase sigma factor, sigma(G), and induction of sigma(G) synthesis in vegetative cells led to synthesis of gerK mRNA. SpoVT, a regulator of sigma(G)-dependent gene expression, repressed gerK expression. The gerK promoter showed sequence similarities to sigma(G)-dependent promoters, and deletion of elements of this putative promoter abolished gerK expression in sporulation.
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Affiliation(s)
- Takao Igarashi
- Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA
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Shapiro MP, Setlow P. Mechanisms of Bacillus subtilis spore killing by and resistance to an acidic Fe3+-EDTA-iodide-ethanol formulation. J Appl Microbiol 2006; 100:746-53. [PMID: 16553729 DOI: 10.1111/j.1365-2672.2006.02838.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
AIMS To determine the mechanisms of Bacillus subtilis spore killing by and resistance to an acidic solution containing Fe(3+), EDTA, KI and ethanol termed the KMT reagent. METHODS AND RESULTS Wild-type B. subtilis spores were not mutagenized by the KMT reagent but the wild-type and recA spores were killed at the same rate. Spores (alpha(-)beta(-)) lacking most DNA-protective alpha/beta-type small, acid-soluble spore proteins were less resistant to the KMT reagent than wild-type spores but were also not mutagenized, and alpha(-)beta(-) and alpha(-)beta(-)recA spores exhibited nearly identical resistance. Spore resistance to the KMT reagent was greatly decreased if spores had defective coats. However, the level of unsaturated fatty acids in the inner membrane did not determine spore sensitivity to the KMT reagent. Survivors in spore populations killed by the KMT reagent were sensitized to killing by wet heat or nitrous acid and to high salt in plating medium. KMT reagent-killed spores had not released their dipicolinic acid (DPA), although these killed spores released their DPA more readily when germinated with dodecylamine than did untreated spores. However, KMT reagent-killed spores did not germinate with nutrients or Ca(2+)-DPA and were recovered only poorly by lysozyme treatment in a hypertonic medium. CONCLUSIONS The KMT reagent does not kill spores by DNA damage and a major factor in spore resistance to this reagent is the spore coat. KMT reagent treatment damages the spore's ability to germinate, perhaps by damaging the spore's inner membrane. However, this damage is not oxidation of unsaturated fatty acids. SIGNIFICANCE AND IMPACT OF THE STUDY These results provide information on the mechanism of spore resistance to and killing by the KMT reagent developed for killing Bacillus spores.
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Affiliation(s)
- M P Shapiro
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, 06032, USA
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Jones C, Padula N, Setlow P. Effect of mechanical abrasion on the viability, disruption and germination of spores of Bacillus subtilis. J Appl Microbiol 2006; 99:1484-94. [PMID: 16313421 PMCID: PMC1361271 DOI: 10.1111/j.1365-2672.2005.02744.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS To elucidate the factors influencing the sensitivity of Bacillus subtilis spores in killing and disrupting by mechanical abrasion, and the mechanism of stimulation of spore germination by abrasion. METHODS AND RESULTS Spores of B. subtilis strains were abraded by shaking with glass beads in liquid or the dry state, and spore killing, disruption and germination were determined. Dormant spores were more resistant to killing and disruption by abrasion than were growing cells or germinated spores. However, dormant spores of the wild-type strain with or without most coat proteins removed, spores of strains with mutations causing spore coat defects, spores lacking their large depot of dipicolinic acid (DPA) and spores with defects in the germination process exhibited essentially identical rates of killing and disruption by abrasion. When spores lacking all nutrient germinant receptors were enumerated by plating directly on nutrient medium, abrasion increased the plating efficiency of these spores before killing them. Spores lacking all nutrient receptors and either of the two redundant cortex-lytic enzymes behaved similarly in this regard, but the plating efficiency of spores lacking both cortex-lytic enzymes was not stimulated by abrasion. CONCLUSIONS Dormant spores are more resistant to killing and disruption by abrasion than are growing cells or germinated spores, and neither the complete coats nor DPA are important in spore resistance to such treatments. Germination is not essential for spore killing by abrasion, although abrasion can trigger spore germination by activation of either of the spore's cortex-lytic enzymes. SIGNIFICANCE AND IMPACT OF THE STUDY This work provides new insight into the mechanisms of the killing, disruption and germination of spores by abrasion and makes the surprising finding that at least much of the spore coat is not important in spore resistance to abrasion.
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Affiliation(s)
| | - N.L. Padula
- *Correspondence to: P. Setlow, Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06032 USA ()
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Cortezzo DE, Setlow P. Analysis of factors that influence the sensitivity of spores of Bacillus subtilis to DNA damaging chemicals. J Appl Microbiol 2005; 98:606-17. [PMID: 15715863 DOI: 10.1111/j.1365-2672.2004.02495.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
AIMS To elucidate factors influencing the sensitivity of Bacillus subtilis spores to DNA damaging chemicals. METHODS AND RESULTS Wild-type spores of B. subtilis made at lower temperatures were more sensitive to the DNA damaging chemicals formaldehyde and nitrous acid than were spores made at higher temperatures, but this was not the case with the DNA alkylating agents ethylmethanesulphonate and methylmethanesulphonate. Spores lacking most DNA protective alpha/beta-type small, acid-soluble proteins (termed alpha-beta- spores) made at lower temperatures were also more sensitive to killing through DNA damage by hydrogen peroxide than were alpha-beta- spores made at higher temperatures. The spore coat, whose composition varies significantly with sporulation temperature, played only a minor role in spore resistance to these DNA damaging agents. Spores made at lower temperatures exhibited higher permeability to the methylamine and germinated more rapidly with the surfactant dodecylamine than did spores made at higher temperatures. Treatment of spores with the oxidizing agent cumene hydroperoxide sensitized the surviving spores to all these DNA damaging agents. The fatty acid composition of the inner membrane of spores made at different temperatures differed significantly, but levels of unsaturated fatty acids in the inner membrane did not influence spore resistance to DNA damaging agents or the sensitization to such agents by prior treatment with cumene hydroperoxide. CONCLUSIONS The higher rates of methylamine permeation across the inner membrane of spores made at lower temperatures and the greater sensitivity of wild-type spores made at lower temperatures to formaldehyde and nitrous acid and of alpha-beta- spores made at lower temperatures to hydrogen peroxide, all agents that must pass through the spore's inner membrane to damage DNA in the spore core, suggest that the permeability of the inner membrane is a significant factor influencing spore sensitivity to these agents. The sensitization of spores to DNA damaging chemicals by pretreatment with an oxidizing agent, a treatment that increases the permeability of the spore's inner membrane, and the more rapid dodecylamine germination of spores made at lower temperatures are consistent with this suggestion. SIGNIFICANCE AND IMPACT OF THE STUDY The results in this communication provide new insight into the factors that influence the resistance of spores of Bacillus species to chemicals that kill spores by damaging spore DNA.
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Affiliation(s)
- D E Cortezzo
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06032, USA
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