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Tirloni E, Bernardi C, Celandroni F, Mazzantini D, Massimino M, Stella S, Ghelardi E. Prevalence, Virulence Potential, and Growth in Cheese of Bacillus cereus Strains Isolated from Fresh and Short-Ripened Cheeses Sold on the Italian Market. Microorganisms 2023; 11:microorganisms11020521. [PMID: 36838486 PMCID: PMC9964947 DOI: 10.3390/microorganisms11020521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 02/03/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
This study investigated B. cereus presence in 122 samples belonging to 34 typologies of fresh or short-ripened cheeses made from cow, sheep, goat, or buffalo pasteurized milk, and sold on the Italian market. B. cereus was isolated at a prevalence of 9.8%, with a marked variability among cheese categories, and at low counts (always below 2.26 Log CFU/g). Twelve isolates were identified by MALDI-TOF analysis and typified by RAPD PCR as belonging to different B. cereus strains. All the strains were tested for the production of hemolysin BL, phosphatidylcholine-specific phospholipase C, proteases, and biofilm formation, and for the presence of chromosomal toxin-encoding genes (sph, plcA, cytK, entFM, bcet, nheA, nheB, nheC). Overall, 92% of strains harbored bcet, 75% the three genes nheA, nheB, and nheC, as well as plcA and sph, 67% entFM, and 33% cytK. All strains showed biofilm-forming ability. A chemical-physical characterization of the cheeses was also performed to show their suitability as substrates for B. cereus growth, showing high heterogeneity in terms of pH, aw, salt content, and concentration of organic acids. Finally, the ability to support spore germination and vegetative cell growth of a selected cheese was investigated in spores-inoculated samples maintained at 10 °C and 15 °C, showing the inhibitory effect of low storage temperatures.
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Affiliation(s)
- Erica Tirloni
- Department of Veterinary Medicine and Animal Sciences, University of Milan, Via dell’Università 6, 26900 Lodi, Italy
| | - Cristian Bernardi
- Department of Veterinary Medicine and Animal Sciences, University of Milan, Via dell’Università 6, 26900 Lodi, Italy
| | - Francesco Celandroni
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via San Zeno 37, 56127 Pisa, Italy
| | - Diletta Mazzantini
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via San Zeno 37, 56127 Pisa, Italy
| | - Mariacristina Massimino
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via San Zeno 37, 56127 Pisa, Italy
| | - Simone Stella
- Department of Veterinary Medicine and Animal Sciences, University of Milan, Via dell’Università 6, 26900 Lodi, Italy
| | - Emilia Ghelardi
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via San Zeno 37, 56127 Pisa, Italy
- Research Center Nutraceuticals and Food for Health-Nutrafood, University of Pisa, 56128 Pisa, Italy
- Correspondence: ; Tel.: +39-050-2213679
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Tirloni E, Bernardi C, Ghelardi E, Celandroni F, Andrighetto C, Rota N, Stella S. Biopreservation as a potential hurdle for Bacillus cereus growth in fresh cheese. J Dairy Sci 2019; 103:150-160. [PMID: 31668441 DOI: 10.3168/jds.2019-16739] [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: 04/03/2019] [Accepted: 09/03/2019] [Indexed: 11/19/2022]
Abstract
This study aimed to evaluate the possible inhibitory effect of natural lactic acid bacteria on the growth of 2 Bacillus cereus strains. First, we evaluated the behavior of spores of B. cereus GPe2 and D43 when inoculated before cheesemaking using pasteurized or raw milk; no statistical differences were observed between cheese produced with the 2 types of milk. Then, lactic acid bacteria (LAB) were isolated from cheese at the last sampling time, identified, and tested in vitro for their antagonistic activity and organic acid production by using an HPLC method, showing antimicrobial potential. The LAB that produced larger inhibition halos (>9 mm) against B. cereus strains (LAB 3, 6, 9, 10: Lactococcus lactis ssp. lactis; LAB 7: Lactococcus lactis ssp. cremoris) were selected to produce a LAB mixture for subsequent tests. Spores of B. cereus GPe2 and D43 were inoculated in pasteurized milk before cheesemaking with or without addition of the LAB mixture at a high dosage. Bacillus cereus grew more slowly when LAB were added to the dairy matrix (with differences from 2.36 to 2.66 log cfu/g in B. cereus GPe2 and D43 growth).
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Affiliation(s)
- Erica Tirloni
- Department of Health, Animal Science and Food Safety, Università degli Studi di Milano, Via Celoria 10, IT-20133, Milan, Italy.
| | - Cristian Bernardi
- Department of Health, Animal Science and Food Safety, Università degli Studi di Milano, Via Celoria 10, IT-20133, Milan, Italy
| | - Emilia Ghelardi
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via San Zeno 37, IT-56127, Pisa, Italy; Research Center Nutraceuticals and Food for Health-Nutrafood, University of Pisa, IT-56127, Pisa, Italy
| | - Francesco Celandroni
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via San Zeno 37, IT-56127, Pisa, Italy
| | - Christian Andrighetto
- Agenzia Veneta per l'Innovazione nel Settore Primario, Via San Gaetano 74, Thiene (VI), Italy
| | - Nicola Rota
- Freelance Agronomist, Pontirolo Nuovo, IT-24040, Italy
| | - Simone Stella
- Department of Health, Animal Science and Food Safety, Università degli Studi di Milano, Via Celoria 10, IT-20133, Milan, Italy
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Soni A, Oey I, Silcock P, Bremer PJ. Impact of temperature, nutrients, pH and cold storage on the germination, growth and resistance of Bacillus cereus spores in egg white. Food Res Int 2018; 106:394-403. [DOI: 10.1016/j.foodres.2018.01.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 12/10/2017] [Accepted: 01/06/2018] [Indexed: 12/11/2022]
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Tirloni E, Ghelardi E, Celandroni F, Bernardi C, Stella S. Effect of dairy product environment on the growth of Bacillus cereus. J Dairy Sci 2017; 100:7026-7034. [DOI: 10.3168/jds.2017-12978] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 05/27/2017] [Indexed: 11/19/2022]
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Tirloni E, Ghelardi E, Celandroni F, Bernardi C, Casati R, Rosshaug PS, Stella S. Bacillus cereus in fresh ricotta: Comparison of growth and Haemolysin BL production after artificial contamination during production or post processing. Food Control 2017. [DOI: 10.1016/j.foodcont.2017.04.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Phillips DA, Joseph CM, Hirsch PR. Occurrence of flavonoids and nucleosides in agricultural soils. Appl Environ Microbiol 2010; 63:4573-7. [PMID: 16535739 PMCID: PMC1389295 DOI: 10.1128/aem.63.11.4573-4577.1997] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AN ECOLOGICALLY RELEVANT SOIL EXTRACTION PROCEDURE SEPARATED TWO TYPES OF MOLECULES IMPORTANT FOR BACTERIA: flavonoids and small hydrophilic organic compounds. Two flavonoids, identified previously as inducers of nodulation genes in Rhizobium meliloti, were detected in rhizosphere soil from alfalfa (Medicago sativa L.). In addition, biologically significant quantities (micromoles per kilogram) of ribonucleosides and deoxyribonucleosides were found in all soils tested. Long-term wheat (Triticum aestivum L.) plots that had received manure contained elevated amounts of nucleosides, and in a separate experiment, the presence of legumes in a wheat-cropping sequence increased soil nucleosides. Intact bacterial cells accounted for less than 1% of the free nucleosides detected. These results suggest new testable hypotheses for molecular ecologists and differ from those obtained with older, harsher techniques.
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Dodatko T, Akoachere M, Jimenez N, Alvarez Z, Abel-Santos E. Dissecting interactions between nucleosides and germination receptors in Bacillus cereus 569 spores. MICROBIOLOGY-SGM 2009; 156:1244-1255. [PMID: 20035009 DOI: 10.1099/mic.0.030270-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Bacillus cereus 569 spores germinate either with inosine as a sole germinant or with a combination of nucleosides and L-alanine. Whereas the inosine-only germination pathway requires the presence of two different germination receptors (GerI and GerQ) to be activated, the nucleoside/alanine germination pathway only needs one of the two receptors. To differentiate how nucleoside recognition varies between the inosine-only germination pathway and the nucleoside/alanine germination pathway, we tested 61 purine analogues as agonists and antagonists of the two pathways in wild-type, DeltagerI and DeltagerQ spores. The structure-activity relationships of germination agonists and antagonists suggest that the inosine-only germination pathway is restricted to recognize a single germinant (inosine), but can be inhibited in predictable patterns by structurally distinct purine nucleosides. B. cereus spores encoding GerI as the only nucleoside receptor (DeltagerQ mutant) showed a germination inhibition profile similar to wild-type spores treated with inosine only. Thus, GerI seems to have a well-organized binding site that recognizes inosine and inhibitors through specific substrate-protein interactions. Structure-activity analysis also showed that the nucleoside/alanine germination pathway is more promiscuous toward purine nucleoside agonists, and is only inhibited by hydrophobic analogues. B. cereus spores encoding GerQ as the only nucleoside receptor (DeltagerI mutant) behaved like wild-type spores treated with inosine and L-alanine. Thus, the GerQ receptor seems to recognize substrates in a more flexible binding site through non-specific interactions. We propose that the GerI receptor is responsible for germinant detection in the inosine-only germination pathway. On the other hand, supplementing inosine with l-alanine allows bypassing of the GerI receptor to activate the more flexible GerQ receptor.
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Affiliation(s)
- Tetyana Dodatko
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Monique Akoachere
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA
| | - Nadia Jimenez
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA
| | - Zadkiel Alvarez
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA
| | - Ernesto Abel-Santos
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA
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Dodatko T, Akoachere M, Muehlbauer SM, Helfrich F, Howerton A, Ross C, Wysocki V, Brojatsch J, Abel-Santos E. Bacillus cereus spores release alanine that synergizes with inosine to promote germination. PLoS One 2009; 4:e6398. [PMID: 19636427 PMCID: PMC2712684 DOI: 10.1371/journal.pone.0006398] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 05/30/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The first step of the bacterial lifecycle is the germination of bacterial spores into their vegetative form, which requires the presence of specific nutrients. In contrast to closely related Bacillus anthracis spores, Bacillus cereus spores germinate in the presence of a single germinant, inosine, yet with a significant lag period. METHODS AND FINDINGS We found that the initial lag period of inosine-treated germination of B. cereus spores disappeared in the presence of supernatants derived from already germinated spores. The lag period also dissipated when inosine was supplemented with the co-germinator alanine. In fact, HPLC-based analysis revealed the presence of amino acids in the supernatant of germinated B. cereus spores. The released amino acids included alanine in concentrations sufficient to promote rapid germination of inosine-treated spores. The alanine racemase inhibitor D-cycloserine enhanced germination of B. cereus spores, presumably by increasing the L-alanine concentration in the supernatant. Moreover, we found that B. cereus spores lacking the germination receptors gerI and gerQ did not germinate and release amino acids in the presence of inosine. These mutant spores, however, germinated efficiently when inosine was supplemented with alanine. Finally, removal of released amino acids in a washout experiment abrogated inosine-mediated germination of B. cereus spores. CONCLUSIONS We found that the single germinant inosine is able to trigger a two-tier mechanism for inosine-mediated germination of B. cereus spores: Inosine mediates the release of alanine, an essential step to complete the germination process. Therefore, B. cereus spores appear to have developed a unique quorum-sensing feedback mechanism to monitor spore density and to coordinate germination.
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Affiliation(s)
- Tetyana Dodatko
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Monique Akoachere
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
| | - Stefan M. Muehlbauer
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Forrest Helfrich
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, United States of America
| | - Amber Howerton
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
| | - Christian Ross
- School of Life Science, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
| | - Vicki Wysocki
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, United States of America
| | - Jürgen Brojatsch
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Ernesto Abel-Santos
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
- * E-mail:
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Ghelardi E, Celandroni F, Salvetti S, Fiscarelli E, Senesi S. Bacillus thuringiensis pulmonary infection: critical role for bacterial membrane-damaging toxins and host neutrophils. Microbes Infect 2007; 9:591-8. [PMID: 17387030 DOI: 10.1016/j.micinf.2007.02.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 01/23/2007] [Accepted: 02/02/2007] [Indexed: 12/01/2022]
Abstract
The occurrence of Bacillus thuringiensis bacteremia in a neutropenic patient suffering from severe pulmonary disease addressed the question of whether the aggressive behavior of B. thuringiensis depended on the host status and/or on the membrane-damaging toxins the isolate produced. After intratracheal injection, BALB/c mice developed pneumonia followed by fatal dissemination into deep organs, with mice rendered neutropenic by cyclophosphamide injection being extremely more susceptible to infection than normal animals. In animals infected with isogenic strains of B. thuringiensis progressively more defective in membrane-damaging toxins (407 Cry->IP2>MP02), an increase in the 50% lethal dose was registered (3.9x10(5), 1.1x10(6), 1.2x10(7)CFU). Consistently, after non-lethal dose application, only 407 Cry- replicated intrapulmonary, reaching a bacterial burden 4.7-fold and 40.9-fold higher than IP2 (P=0.018) and MP02 (P=0.008) at 48h post-inoculation. Notably, the time-course of infection was similar in animals infected with viable bacilli or spores, with neutropenic mice always being more susceptible to infection. The overall results indicate that B. thuringiensis may be responsible for opportunistic infections and strongly suggest that membrane-damaging toxins contribute to intrapulmonary bacterial persistence favoring dissemination.
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Affiliation(s)
- Emilia Ghelardi
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università di Pisa, Via San Zeno 37, 56127 Pisa, Italy
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Abel-Santos E, Dodatko T. Differential nucleoside recognition during Bacillus cereus 569 (ATCC 10876) spore germination. NEW J CHEM 2007. [DOI: 10.1039/b616695d] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Alberto F, Botella L, Carlin F, Nguyen-The C, Broussolle V. The Clostridium botulinum GerAB germination protein is located in the inner membrane of spores. FEMS Microbiol Lett 2005; 253:231-5. [PMID: 16242862 DOI: 10.1016/j.femsle.2005.09.037] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Revised: 09/22/2005] [Accepted: 09/26/2005] [Indexed: 11/15/2022] Open
Abstract
Clostridium botulinum dormant spores germinate in presence of l-alanine via a specific receptor composed of GerAA, GerAB and GerAC proteins. In Bacillus subtilis spores, GerAA and GerAC proteins were located in the inner membrane of the spore. We studied the location of the GerAB protein in C. botulinum spore fractions by Western-blot analysis, using an antipeptidic antibody. The protein GerAB was in vitro translated and used to confirm the specificity of the antibodies. GerAB was not present in a coat and spore outer membrane fraction but was present in a fraction of decoated spores containing inner membrane. These results strongly suggest that the protein GerAB is located in the inner membrane of the spore.
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Affiliation(s)
- François Alberto
- INRA UMR A408 Sécurité et Qualité des Produits d'Origine Végétale, Institut National de la Recherche Agronomique, Domaine Saint-Paul, Site Agroparc, 84914 Avignon Cedex 9, France
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Celandroni F, Longo I, Tosoratti N, Giannessi F, Ghelardi E, Salvetti S, Baggiani A, Senesi S. Effect of microwave radiation on Bacillus subtilis spores. J Appl Microbiol 2005; 97:1220-7. [PMID: 15546413 DOI: 10.1111/j.1365-2672.2004.02406.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To compare the killing efficacy and the effects exerted by microwaves and conventional heating on structural and molecular components of Bacillus subtilis spores. METHODS AND RESULTS A microwave waveguide applicator was developed to generate a uniform and measurable distribution of the microwave electric-field amplitude. The applicator enabled the killing efficacy exerted by microwaves on B. subtilis spores to be evaluated in comparison with conventional heating at the same temperature value. The two treatments produced a similar kinetics of spore survival, while remarkably different effects on spore structures were seen. The cortex layer of the spores subjected to conductive heating was 10 times wider than that of the untreated spores; in contrast, the cortex of irradiated spores did not change. In addition, the heated spores were found to release appreciable amounts of dipicolinic acid (DPA) upon treatment, while extracellular DPA was completely undetectable in supernatants of the irradiated spores. These observations suggest that microwave radiation may promote the formation of stable complexes between DPA and other spore components (i.e. calcium ions); thus, making any release of DPA from irradiated spores undetectable. Indeed, while a decrease in measurable DPA concentrations was not produced by microwave radiation on pure DPA solutions, a significant lowering in DPA concentration was detected when this molecule was exposed to microwaves in the presence of either calcium ions or spore suspensions. CONCLUSIONS Microwaves are as effective as conductive heating in killing B. subtilis spores, but the microwave E-field induces changes in the structural and/or molecular components of spores that differ from those attributable only to heat. SIGNIFICANCE AND IMPACT OF THE STUDY This study provides information on the effect of microwaves on B. subtilis spore components.
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Affiliation(s)
- F Celandroni
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Universita degli Studi di Pisa, Pisa, Italy
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Senesi S, Celandroni F, Salvetti S, Beecher DJ, Wong ACL, Ghelardi E. Swarming motility in Bacillus cereus and characterization of a fliY mutant impaired in swarm cell differentiation. MICROBIOLOGY (READING, ENGLAND) 2002; 148:1785-1794. [PMID: 12055298 DOI: 10.1099/00221287-148-6-1785] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This report describes a new behavioural response of Bacillus cereus that consists of a surface-induced differentiation of elongated and hyperflagellated swarm cells exhibiting the ability to move collectively across the surface of the medium. The discovery of swarming motility in B. cereus paralleled the isolation of a spontaneous non-swarming mutant that was found to carry a deletion of fliY, the homologue of which, in Bacillus subtilis, encodes an essential component of the flagellar motor-switch complex. However, in contrast to B. subtilis, the fliY mutant of B. cereus was flagellated and motile, thus suggesting a different role for FliY in this organism. The B. cereus mutant was completely deficient in chemotaxis and in the secretion of the L2 component of the tripartite pore-forming necrotizing toxin, haemolysin BL, which was produced exclusively by the wild-type strain during swarm-cell differentiation. All the defects in the fliY mutant of B. cereus could be complemented by a plasmid harbouring the B. cereus fliY gene. These results demonstrate that the activity of fliY is required for swarming and chemotaxis in B. cereus, and suggest that swarm-cell differentiation is coupled with virulence in this organism.
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Affiliation(s)
- Sonia Senesi
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università degli Studi di Pisa, Via S. Zeno 35, Pisa 56127, Italy1
| | - Francesco Celandroni
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università degli Studi di Pisa, Via S. Zeno 35, Pisa 56127, Italy1
| | - Sara Salvetti
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università degli Studi di Pisa, Via S. Zeno 35, Pisa 56127, Italy1
| | - Douglas J Beecher
- Food Research Institute, Department of Food Microbiology and Toxicology, University of Wisconsin-Madison, 1925 Willow Drive, Madison, WI 53706, USA2
| | - Amy C L Wong
- Food Research Institute, Department of Food Microbiology and Toxicology, University of Wisconsin-Madison, 1925 Willow Drive, Madison, WI 53706, USA2
| | - Emilia Ghelardi
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università degli Studi di Pisa, Via S. Zeno 35, Pisa 56127, Italy1
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Schuch R, Garibian A, Saxild HH, Piggot PJ, Nygaard P. Nucleosides as a carbon source in Bacillus subtilis: characterization of the drm-pupG operon. MICROBIOLOGY (READING, ENGLAND) 1999; 145 ( Pt 10):2957-66. [PMID: 10537218 DOI: 10.1099/00221287-145-10-2957] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In Bacillus subtilis, nucleosides are readily taken up from the growth medium and metabolized. The key enzymes in nucleoside catabolism are nucleoside phosphorylases, phosphopentomutase, and deoxyriboaldolase. The characterization of two closely linked loci, drm and pupG, which encode phosphopentomutase (Drm) and guanosine (inosine) phosphorylase (PupG), respectively, is reported here. When expressed in Escherichia coli mutant backgrounds, drm and pupG confer phosphopentomutase and purine-nucleoside phosphorylase activity. Northern blot and enzyme analyses showed that drm and pupG form a dicistronic operon. Both enzymes are induced when nucleosides are present in the growth medium. Using mutants deficient in nucleoside catabolism, it was demonstrated that the low-molecular-mass effectors of this induction most likely were deoxyribose 5-phosphate and ribose 5-phosphate. Both Drm and PupG activity levels were higher when succinate rather than glucose served as the carbon source, indicating that the expression of the operon is subject to catabolite repression. Primer extension analysis identified two transcription initiation signals upstream of drm; both were utilized in induced and non-induced cells. The nucleoside-catabolizing system in B. subtilis serves to utilize the base for nucleotide synthesis while the pentose moiety serves as the carbon source. When added alone, inosine barely supports growth of B. subtilis. This slow nucleoside catabolism contrasts with that of E. coli, which grows rapidly on a nucleoside as a carbon source. When inosine was added with succinate or deoxyribose, however, a significant increase in growth was observed in B. subtilis. The findings of this study therefore indicate that the B. subtilis system for nucleoside catabolism differs greatly from the well-studied system in E. coli.
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Affiliation(s)
- R Schuch
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences Bethesda, MD 20814, USA
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FERMANIAN CHRISTOPHE, FREMY JEANMARC, LAHELLEC CECILE. BACILLUS CEREUS PATHOGENICITY: A REVIEW. ACTA ACUST UNITED AC 1993. [DOI: 10.1111/j.1745-4581.1993.tb00282.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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