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Wenner N, Zhu X, Rowe WPM, Händler K, Hinton JCD. Succinate utilisation by Salmonella is inhibited by multiple regulatory systems. PLoS Genet 2024; 20:e1011142. [PMID: 38457455 DOI: 10.1371/journal.pgen.1011142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 03/26/2024] [Accepted: 01/19/2024] [Indexed: 03/10/2024] Open
Abstract
Succinate is a potent immune signalling molecule that is present in the mammalian gut and within macrophages. Both of these infection niches are colonised by the pathogenic bacterium Salmonella enterica serovar Typhimurium during infection. Succinate is a C4-dicarboyxlate that can serve as a source of carbon for bacteria. When succinate is provided as the sole carbon source for in vitro cultivation, Salmonella and other enteric bacteria exhibit a slow growth rate and a long lag phase. This growth inhibition phenomenon was known to involve the sigma factor RpoS, but the genetic basis of the repression of bacterial succinate utilisation was poorly understood. Here, we use an experimental evolution approach to isolate fast-growing mutants during growth of S. Typhimurium on succinate containing minimal medium. Our approach reveals novel RpoS-independent systems that inhibit succinate utilisation. The CspC RNA binding protein restricts succinate utilisation, an inhibition that is antagonised by high levels of the small regulatory RNA (sRNA) OxyS. We discovered that the Fe-S cluster regulatory protein IscR inhibits succinate utilisation by repressing the C4-dicarboyxlate transporter DctA. Furthermore, the ribose operon repressor RbsR is required for the complete RpoS-driven repression of succinate utilisation, suggesting a novel mechanism of RpoS regulation. Our discoveries shed light on the redundant regulatory systems that tightly regulate the utilisation of succinate. We speculate that the control of central carbon metabolism by multiple regulatory systems in Salmonella governs the infection niche-specific utilisation of succinate.
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Affiliation(s)
- Nicolas Wenner
- Clinical Infection, Microbiology & Immunology, Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Xiaojun Zhu
- Clinical Infection, Microbiology & Immunology, Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Will P M Rowe
- Clinical Infection, Microbiology & Immunology, Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Kristian Händler
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin, Ireland
| | - Jay C D Hinton
- Clinical Infection, Microbiology & Immunology, Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
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Perullini M, Dulhoste S, Ribot F, Pehau-Arnaudet G, Bouvet OMM, Livage J, Nassif N. Bacteria metabolic adaptation to oxidative stress: the case of silica. J Biotechnol 2023; 374:80-89. [PMID: 37567503 DOI: 10.1016/j.jbiotec.2023.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 07/25/2023] [Accepted: 08/07/2023] [Indexed: 08/13/2023]
Abstract
Although the presence of silica in many living organisms offers advanced properties including cell protection, the different in vitro attempts to build living materials in pure silica never favoured the cells viability. Thus, little attention has been paid to host-guest interactions to modify the expected biologic response. Here we report the physiological changes undergone by Escherichia coli K-12 in silica from colloidal solution to gel confinement. We show that the physiological alterations in growing cultures are not triggered by the initial oxidative Reactive Oxygen Species (ROS) response. Silica promotes the induction of alternative metabolic pathways along with an increase of growth suggesting the existence of rpoS polymorphisms. Since the functionality of hybrid materials depends on the specific biologic responses of their guests, such cell physiological adaptation opens perspectives in the design of bioactive devices attracting for a large field of sciences.
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Affiliation(s)
- Mercedes Perullini
- CONICET - Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Laboratorio de materiales funcionales con actividad biológica, Buenos Aires, Argentina.
| | - Sophie Dulhoste
- CONICET - Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Laboratorio de materiales funcionales con actividad biológica, Buenos Aires, Argentina
| | - François Ribot
- Sorbonne Université, CNRS, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), F-75252 Paris Cedex 05, France
| | | | - Odile M M Bouvet
- IAME, UMR 1137, INSERM, Univ Paris Diderot, Sorbonne Paris Cité, F-75018 Paris, France
| | - Jacques Livage
- Sorbonne Université, CNRS, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), F-75252 Paris Cedex 05, France.
| | - Nadine Nassif
- Sorbonne Université, CNRS, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), F-75252 Paris Cedex 05, France
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Retamal P, Gaspar J, Benavides MB, Saenz L, Galarce N, Aravena T, Cornejo J, Lapierre L. Virulence and antimicrobial resistance factors in Salmonella enterica serotypes isolated from pigs and chickens in central Chile. Front Vet Sci 2022; 9:971246. [PMID: 36204291 PMCID: PMC9530323 DOI: 10.3389/fvets.2022.971246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 08/31/2022] [Indexed: 11/13/2022] Open
Abstract
Salmonella enterica is a food-borne pathogen with a wide host-range that during decades has been of public health concern in developed and developing countries. In Chile, the poultry and pig industries represent the biggest contribution of meat consumption in the population, and sanitary regulations have been imposed for Salmonella control. The aim of this work was to determine and characterize Salmonella strains isolated from pigs and chicken raised on commercials farms in Chile. For this, isolates belonging to pigs (n = 46) and poultry (n = 57) were genotyped by two multiplex PCR reactions and virulotyped by the PCR detection of virulence-associated genes. In addition, isolates were serotyped and analyzed by the Kirby Bauer assay to determine their antimicrobial resistance phenotypes. From these analyses 52 genotypes, six serotypes and several multidrug resistance phenotypes and different combinations of virulence-associated genes were detected. These results suggest that S. enterica in pigs and poultry in central Chile should be monitored due to potential consequences in public and animal health.
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Affiliation(s)
- Patricio Retamal
- Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
| | - Joaquim Gaspar
- Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
- Magister en Ciencias Animales y Veterinarias, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
| | - María Belén Benavides
- Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
- Magister en Ciencias Animales y Veterinarias, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
| | - Leonardo Saenz
- Departamento de Ciencias Biológicas, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
| | - Nicolás Galarce
- Escuela de Medicina Veterinaria, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile
| | - Trinidad Aravena
- Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
| | - Javiera Cornejo
- Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
- Javiera Cornejo
| | - Lisette Lapierre
- Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile
- *Correspondence: Lisette Lapierre
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In Vitro Gut Modeling as a Tool for Adaptive Evolutionary Engineering of Lactiplantibacillus plantarum. mSystems 2021; 6:6/2/e01085-20. [PMID: 33850040 PMCID: PMC8546992 DOI: 10.1128/msystems.01085-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Research and marketing of probiotics demand holistic strain improvement considering both the biotic and abiotic gut environment. Here, we aim to establish the continuous in vitro colonic fermentation model PolyFermS as a tool for adaptive evolutionary engineering. Immobilized fecal microbiota from adult donors were steadily cultivated up to 72 days in PolyFermS reactors, providing a long-term compositional and functional stable ecosystem akin to the donor’s gut. Inoculation of the gut microbiota with immobilized or planktonic Lactiplantibacillus plantarum NZ3400, a derivative of the probiotic model strain WCFS1, led to successful colonization. Whole-genome sequencing of 45 recovered strains revealed mutations in 16 genes involved in signaling, metabolism, transport, and cell surface. Remarkably, mutations in LP_RS14990, LP_RS15205, and intergenic region LP_RS05100<LP_RS05095 were found in recovered strains from different adaptation experiments. Combined addition of the reference strain NZ3400 and each of those mutants to the gut microbiota resulted in increased abundance of the corresponding mutant in PolyFermS microbiota after 10 days, showing the beneficial nature of these mutations. Our data show that the PolyFermS system is a suitable technology to generate adapted mutants for colonization under colonic conditions. Analysis thereof will provide knowledge about factors involved in gut microbiota colonization and persistence. IMPORTANCE Improvement of bacterial strains in regard to specific abiotic environmental factors is broadly used to enhance strain characteristics for processing and product quality. However, there is currently no multidimensional probiotic strain improvement approach for both abiotic and biotic factors of a colon microbiota. The continuous PolyFermS fermentation model allows stable and reproducible continuous cultivation of colonic microbiota and provides conditions akin to the host gut with high control and easy sampling. This study investigated the suitability of PolyFermS for adaptive evolutionary engineering of a probiotic model organism for lactobacilli, Lactiplantibacillus plantarum, to an adult human colonic microbiota. The application of PolyFermS controlled gut microbiota environment led to adaptive evolution of L. plantarum strains for enhanced gut colonization characteristics. This novel tool for strain improvement can be used to reveal relevant factors involved in gut microbiota colonization and develop adapted probiotic strains with improved functionality in the gut.
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Impact of the Resistance Responses to Stress Conditions Encountered in Food and Food Processing Environments on the Virulence and Growth Fitness of Non-Typhoidal Salmonellae. Foods 2021; 10:foods10030617. [PMID: 33799446 PMCID: PMC8001757 DOI: 10.3390/foods10030617] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 02/24/2021] [Accepted: 03/10/2021] [Indexed: 01/22/2023] Open
Abstract
The success of Salmonella as a foodborne pathogen can probably be attributed to two major features: its remarkable genetic diversity and its extraordinary ability to adapt. Salmonella cells can survive in harsh environments, successfully compete for nutrients, and cause disease once inside the host. Furthermore, they are capable of rapidly reprogramming their metabolism, evolving in a short time from a stress-resistance mode to a growth or virulent mode, or even to express stress resistance and virulence factors at the same time if needed, thanks to a complex and fine-tuned regulatory network. It is nevertheless generally acknowledged that the development of stress resistance usually has a fitness cost for bacterial cells and that induction of stress resistance responses to certain agents can trigger changes in Salmonella virulence. In this review, we summarize and discuss current knowledge concerning the effects that the development of resistance responses to stress conditions encountered in food and food processing environments (including acid, osmotic and oxidative stress, starvation, modified atmospheres, detergents and disinfectants, chilling, heat, and non-thermal technologies) exerts on different aspects of the physiology of non-typhoidal Salmonellae, with special emphasis on virulence and growth fitness.
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Planktonic and Sessile Artificial Colonic Microbiota Harbor Distinct Composition and Reestablish Differently upon Frozen and Freeze-Dried Long-Term Storage. mSystems 2020; 5:5/1/e00521-19. [PMID: 31964766 PMCID: PMC6977070 DOI: 10.1128/msystems.00521-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Fecal microbiota transplantation has been successfully applied in the treatment of recurrent Clostridium difficile infection and has been suggested as an alternative therapy for other intestinal disorders such as inflammatory bowel disease or metabolic syndrome. “Artificial” colonic microbiota delivered by PolyFermS continuous fermentation models can provide a controllable and reproducible alternative to fecal transplantation, but effective preservation strategies must be developed. In this study, we systematically investigated the response of sessile and planktonic artificial colonic microbiota to cryopreservation and lyophilization. We suggest that functional redundancy is an important factor in providing functional stability with respect to exposure to stress during processing and storage. Functional redundancy in compositionally reduced microbial systems may be considered when designing microbial products for therapy. Biofilm-associated, sessile communities represent the major bacterial lifestyle, whereas planktonic cells mainly appear during initial colonization of new surfaces. Previous research, mainly performed with pathogens, demonstrated increased environmental stress tolerance of biofilm-growing compared to planktonic bacteria. The lifestyle-specific stress response of colonic microbiota, both natural and fermentation produced, has not been addressed before. Planktonic and sessile “artificial” colonic microbiota delivered by PolyFermS continuous fermentation models can provide a controllable and reproducible alternative to fecal transplantation in treating gastrointestinal disorders. We therefore characterized planktonic and sessile microbiota produced in two PolyFermS models inoculated with immobilized fecal microbiota and comparatively tested their levels of tolerance of frozen storage (–80°C) and freeze-dried storage (4°C) for 9 months to mimic preservation strategies for therapeutic applications. Sessile microbiota harbored next to shared taxa a unique community distinguishable from planktonic microbiota. Synergistetes and Proteobacteria were highly represented in sessile microbiota, while Firmicutes were more abundant in planktonic microbiota. The community structure and metabolic activity of both microbiota, monitored during standardized reactivation batch fermentations, were better preserved after frozen storage than dried storage, indicated by higher Bray-Curtis similarity and enhanced recovery of metabolite production. For both lifestyles, reestablishment of Bacteroidaceae was impaired after frozen and dried storage along with reduced propionate formation. In contrast, butyrate production was maintained after reactivation despite compositional rearrangements within the butyrate-producing community. Unexpectedly, the rate of recovery of metabolite production was lower after preservation of sessile than planktonic microbiota. We speculate that higher functional dependencies between microbes might have led to the lower stress tolerance of sessile than planktonic microbiota. IMPORTANCE Fecal microbiota transplantation has been successfully applied in the treatment of recurrent Clostridium difficile infection and has been suggested as an alternative therapy for other intestinal disorders such as inflammatory bowel disease or metabolic syndrome. “Artificial” colonic microbiota delivered by PolyFermS continuous fermentation models can provide a controllable and reproducible alternative to fecal transplantation, but effective preservation strategies must be developed. In this study, we systematically investigated the response of sessile and planktonic artificial colonic microbiota to cryopreservation and lyophilization. We suggest that functional redundancy is an important factor in providing functional stability with respect to exposure to stress during processing and storage. Functional redundancy in compositionally reduced microbial systems may be considered when designing microbial products for therapy.
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Berlanga M, Gomez-Perez L, Guerrero R. Biofilm formation and antibiotic susceptibility in dispersed cells versus planktonic cells from clinical, industry and environmental origins. Antonie van Leeuwenhoek 2017; 110:1691-1704. [PMID: 28770446 DOI: 10.1007/s10482-017-0919-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 07/25/2017] [Indexed: 12/14/2022]
Abstract
We examined the cell-surface physicochemical properties, the biofilm formation capability and the antibiotic susceptibility in dispersed cells (from an artificial biofilm of alginate beads) and compared with their planktonic (free-swimming) counterparts. The strains used were from different origins, such as clinical (Acinetobacter baumannii AB4), cosmetic industry (Klebsiella oxytoca EU213, Pseudomonas aeruginosa EU190), and environmental (Halomonas venusta MAT28). In general, dispersed cells adhered better to surfaces (measured as the "biofilm index") and had a greater hydrophobicity [measured as the microbial affinity to solvents (MATS)] than planktonic cells. The susceptibility to two antibiotics (ciprofloxacin and tetracycline) of dispersed cells was higher compared with that of their planktonic counterparts (tested by the "bactericidal index"). Dispersed and planktonic cells exhibited differences in cell permeability, especially in efflux pump activity, which could be related to the differences observed in susceptibility to antibiotics. At 1 h of biofilm formation in microtiter plates, dispersed cells treated with therapeutic concentration of ciprofloxacin yielded a lower biofilm index than the control dispersed cells without ciprofloxacin. With respect to the planktonic cells, the biofilm index was similar with and without the ciprofloxacin treatment. In both cases there were a reduction of the number of bacteria measured as viable count of the supernatant. The lower biofilm formation in dispersed cells with ciprofloxacin treatment may be due to a significant increase of biofilm disruption with respect to the biofilm from planktonic cells. From a clinical point of view, biofilms formed on medical devices such as catheters, cells that can be related to an infection were the dispersed cells. Our results showed that early treatment with ciprofloxacin of dispersed cells could diminishe bacterial dispersion and facilitate the partial elimination of the new biofilm formed.
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Affiliation(s)
- Mercedes Berlanga
- Department of Biology, Environment and Health, Section Microbiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain.
| | - Laura Gomez-Perez
- Department of Biology, Environment and Health, Section Microbiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | - Ricardo Guerrero
- Laboratory of Molecular Microbiology and Antimicrobials, Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona, IDIBELL, Barcelona, Spain
- Barcelona Knowledge Hub, Academia Europaea, Barcelona, Spain
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Dawoud TM, Davis ML, Park SH, Kim SA, Kwon YM, Jarvis N, O’Bryan CA, Shi Z, Crandall PG, Ricke SC. The Potential Link between Thermal Resistance and Virulence in Salmonella: A Review. Front Vet Sci 2017; 4:93. [PMID: 28660201 PMCID: PMC5469892 DOI: 10.3389/fvets.2017.00093] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 06/01/2017] [Indexed: 12/19/2022] Open
Abstract
In some animals, the typical body temperature can be higher than humans, for example, 42°C in poultry and 40°C in rabbits which can be a potential thermal stress challenge for pathogens. Even in animals with lower body temperatures, when infection occurs, the immune system may increase body temperature to reduce the chance of survival for pathogens. However, some pathogens can still easily overcome higher body temperatures and/or rise in body temperatures through expression of stress response mechanisms. Salmonella is the causative agent of one of the most prevalent foodborne illnesses, salmonellosis, and can readily survive over a wide range of temperatures due to the efficient expression of the heat (thermal) stress response. Therefore, thermal resistance mechanisms can provide cross protection against other stresses including the non-specific host defenses found within the human body thus increasing pathogenic potential. Understanding the molecular mechanisms associated with thermal responses in Salmonella is crucial in designing and developing more effective or new treatments for reducing and eliminating infection caused by Salmonella that have survived heat stress. In this review, Salmonella thermal resistance is assessed followed by an overview of the thermal stress responses with a focus on gene regulation by sigma factors, heat shock proteins, along with the corresponding thermosensors and their association with virulence expression including a focus on a potential link between heat resistance and potential for infection.
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Affiliation(s)
- Turki M. Dawoud
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, United States
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
| | - Morgan L. Davis
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Si Hong Park
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Sun Ae Kim
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Young Min Kwon
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, United States
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Nathan Jarvis
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Corliss A. O’Bryan
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Zhaohao Shi
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Philip G. Crandall
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
| | - Steven C. Ricke
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, United States
- Center for Food Safety, University of Arkansas, Fayetteville, AR, United States
- Department of Food Science, University of Arkansas, Fayetteville, AR, United States
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Rajan K, Shi Z, Ricke SC. Current aspects ofSalmonellacontamination in the US poultry production chain and the potential application of risk strategies in understanding emerging hazards. Crit Rev Microbiol 2016; 43:370-392. [DOI: 10.1080/1040841x.2016.1223600] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Kalavathy Rajan
- Center for Food Safety, Department of Food Science, University of Arkansas, Fayetteville, AR, USA
| | - Zhaohao Shi
- Center for Food Safety, Department of Food Science, University of Arkansas, Fayetteville, AR, USA
| | - Steven C. Ricke
- Center for Food Safety, Department of Food Science, University of Arkansas, Fayetteville, AR, USA
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Berlanga M, Guerrero R. Living together in biofilms: the microbial cell factory and its biotechnological implications. Microb Cell Fact 2016; 15:165. [PMID: 27716327 PMCID: PMC5045575 DOI: 10.1186/s12934-016-0569-5] [Citation(s) in RCA: 150] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 09/23/2016] [Indexed: 01/18/2023] Open
Abstract
In nature, bacteria alternate between two modes of growth: a unicellular life phase, in which the cells are free-swimming (planktonic), and a multicellular life phase, in which the cells are sessile and live in a biofilm, that can be defined as surface-associated microbial heterogeneous structures comprising different populations of microorganisms surrounded by a self-produced matrix that allows their attachment to inert or organic surfaces. While a unicellular life phase allows for bacterial dispersion and the colonization of new environments, biofilms allow sessile cells to live in a coordinated, more permanent manner that favors their proliferation. In this alternating cycle, bacteria accomplish two physiological transitions via differential gene expression: (i) from planktonic cells to sessile cells within a biofilm, and (ii) from sessile to detached, newly planktonic cells. Many of the innate characteristics of biofilm bacteria are of biotechnological interest, such as the synthesis of valuable compounds (e.g., surfactants, ethanol) and the enhancement/processing of certain foods (e.g., table olives). Understanding the ecology of biofilm formation will allow the design of systems that will facilitate making products of interest and improve their yields.
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Affiliation(s)
- Mercedes Berlanga
- Section Microbiology, Department of Biology, Health and Environment, Faculty of Pharmacy and Food Sciences, University of Barcelona, Av. Joan XXIII, s/n, 08028 Barcelona, Spain
| | - Ricardo Guerrero
- Laboratory of Molecular Microbiology and Antimicrobials, Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona-IDIBELL, Barcelona, Spain
- Barcelona Knowledge Hub, Academia Europaea, Barcelona, Spain
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11
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Baka M, Noriega E, Van Langendonck K, Van Impe JF. Influence of food intrinsic complexity on Listeria monocytogenes growth in/on vacuum-packed model systems at suboptimal temperatures. Int J Food Microbiol 2016; 235:17-27. [PMID: 27393885 DOI: 10.1016/j.ijfoodmicro.2016.06.029] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 04/26/2016] [Accepted: 06/22/2016] [Indexed: 11/19/2022]
Abstract
Food intrinsic factors e.g., food (micro)structure, compositional and physicochemical aspects, which are mutually dependent, influence microbial growth. While the effect of composition and physicochemical properties on microbial growth has been thoroughly assessed and characterised, the role of food (micro)structure still remains unravelled. Most studies on food (micro)structure focus on comparing planktonic growth in liquid (microbiological) media with colonial growth in/on solid-like systems or on real food surfaces. However, foods are not only liquids or solids; they can also be emulsions or gelled emulsions and have complex compositions. In this study, Listeria monocytogenes growth was studied on the whole spectrum of (micro)structure, in terms of food (model) systems. The model systems varied not only in (micro)structure, which was the target of the study, but also in compositional and physicochemical characteristics, which was an inevitable consequence of the (micro)structural variability. The compositional and physicochemical differences were mainly due to the presence or absence of fat and gelling agents. The targeted (micro)structures were: i) liquids, ii) aqueous gels, iii) emulsions and iv) gelled emulsions. Furthermore, the microbial dynamics were studied and compared in/on all these model systems, as well as on a compositionally predefined canned meat, developed in order to have equal compositional level to the gelled emulsion model system and represent a real food system. Frankfurter sausages were the targeted real foods, selected as a case study, to which the canned meat had similar compositional characteristics. All systems were vacuum packed and incubated at 4, 8 and 12°C. The most appropriate protocol for the preparation of the model systems was developed. The pH, water activity and resistance to penetration of the model systems were characterised. Results indicated that low temperature contributes to growth variations among the model systems. Additionally, the firmer the solid system, the faster L. monocytogenes grew on it. Finally, it was found that L. monocytogenes grows faster on canned meat and real Frankfurters, as found in a previous study, followed by liquids, aqueous gels, emulsions and gelled emulsions. This observation indicates that all model systems, developed in this study, underestimated L. monocytogenes growth. Despite some limitations, model systems are overall advantageous and therefore, their validation is always recommended prior to further use.
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Affiliation(s)
- Maria Baka
- CPMF2, Flemish Cluster Predictive Microbiology in Foods, Belgium(1); BioTeC+, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Belgium.
| | - Estefanía Noriega
- CPMF2, Flemish Cluster Predictive Microbiology in Foods, Belgium(1); BioTeC+, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Belgium.
| | - Kristof Van Langendonck
- BioTeC+, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Belgium
| | - Jan F Van Impe
- CPMF2, Flemish Cluster Predictive Microbiology in Foods, Belgium(1); BioTeC+, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Belgium.
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Jeanson S, Floury J, Gagnaire V, Lortal S, Thierry A. Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment. Front Microbiol 2015; 6:1284. [PMID: 26648910 PMCID: PMC4664638 DOI: 10.3389/fmicb.2015.01284] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 10/31/2015] [Indexed: 01/26/2023] Open
Abstract
Bacteria, either indigenous or added, are immobilized in solid foods where they grow as colonies. Since the 80's, relatively few research groups have explored the implications of bacteria growing as colonies and mostly focused on pathogens in large colonies on agar/gelatine media. It is only recently that high resolution imaging techniques and biophysical characterization techniques increased the understanding of the growth of bacterial colonies, for different sizes of colonies, at the microscopic level and even down to the molecular level. This review covers the studies on bacterial colony growth in agar or gelatine media mimicking the food environment and in model cheese. The following conclusions have been brought to light. Firstly, under unfavorable conditions, mimicking food conditions, the immobilization of bacteria always constrains their growth in comparison with planktonic growth and increases the sensibility of bacteria to environmental stresses. Secondly, the spatial distribution describes both the distance between colonies and the size of the colonies as a function of the initial level of population. By studying the literature, we concluded that there systematically exists a threshold that distinguishes micro-colonies (radius < 100-200 μm) from macro-colonies (radius >200 μm). Micro-colonies growth resembles planktonic growth and no pH microgradients could be observed. Macro-colonies growth is slower than planktonic growth and pH microgradients could be observed in and around them due to diffusion limitations which occur around, but also inside the macro-colonies. Diffusion limitations of milk proteins have been demonstrated in a model cheese around and in the bacterial colonies. In conclusion, the impact of immobilization is predominant for macro-colonies in comparison with micro-colonies. However, the interaction between the colonies and the food matrix itself remains to be further investigated at the microscopic scale.
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Affiliation(s)
- Sophie Jeanson
- INRA, UMR1253, Science and Technology of Milk and EggsRennes, France
- AGROCAMPUS OUEST, UMR1253, Science and Technology of Milk and EggsRennes, France
| | - Juliane Floury
- INRA, UMR1253, Science and Technology of Milk and EggsRennes, France
- AGROCAMPUS OUEST, UMR1253, Science and Technology of Milk and EggsRennes, France
| | - Valérie Gagnaire
- INRA, UMR1253, Science and Technology of Milk and EggsRennes, France
- AGROCAMPUS OUEST, UMR1253, Science and Technology of Milk and EggsRennes, France
| | - Sylvie Lortal
- INRA, UMR1253, Science and Technology of Milk and EggsRennes, France
- AGROCAMPUS OUEST, UMR1253, Science and Technology of Milk and EggsRennes, France
| | - Anne Thierry
- INRA, UMR1253, Science and Technology of Milk and EggsRennes, France
- AGROCAMPUS OUEST, UMR1253, Science and Technology of Milk and EggsRennes, France
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Cebrián G, Arroyo C, Condón S, Mañas P. Osmotolerance provided by the alternative sigma factors σB and rpoS to Staphylococcus aureus and Escherichia coli is solute dependent and does not result in an increased growth fitness in NaCl containing media. Int J Food Microbiol 2015; 214:83-90. [PMID: 26256716 DOI: 10.1016/j.ijfoodmicro.2015.07.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Revised: 06/24/2015] [Accepted: 07/03/2015] [Indexed: 12/22/2022]
Abstract
The aim of this work was to examine the role of the alternative general stress sigma factors σ(B) and rpoS on the ability of Staphylococcus aureus and Escherichia coli, respectively, to grow in liquid and solid media of different osmolarity. For this purpose, S. aureus strain Newman and its isogenic ΔsigB mutant IK84 and E. coli strain BJ4 and its isogenic ΔrpoS mutant BJ4L1 were grown in media (TSBYE) with different concentrations of NaCl. Growth parameters (lag phase duration, growth rate and maximum number of microorganisms) and limiting growth concentrations (Maximum Non-Inhibitory Concentration - MNIC - and Minimum Inhibitory Concentration - MIC-) were determined. The mechanisms underlying the differences observed between parental and mutant strains were also explored. The absence of the sigma factors σ(B) and rpoS led to a decrease in the MNICs and MICs calculated for S. aureus and E. coli, respectively. Conversely, neither σ(B) nor rpoS provided with increased growth fitness to S. aureus and E. coli cells at NaCl concentrations up to 1.36M and 1M, respectively. The decreased osmotolerance of the σ(B) and rpoS deficient strains, as compared to their parental strains, was compensated by the addition of glycine-betaine (1mM) to the growth medium. It was also observed that the decreased tolerance to NaCl of the mutant strains was coincident with a decreased tolerance to sucrose, KCl, and LiCl but not to glycerol, MgCl2, and CaCl2. Results obtained also demonstrate that the increased osmotolerance of stationary growth phase E. coli cells, as compared to exponential growth phase ones, would be due to the activation of both rpoS-independent and rpoS-dependent mechanisms. This work will help to understand the mechanisms of bacterial resistance to osmotic stress and the role of the alternative sigma factors σ(B) and rpoS in this process.
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Affiliation(s)
- G Cebrián
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain.
| | - C Arroyo
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain
| | - S Condón
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain
| | - P Mañas
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain
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Smet C, Van Derlinden E, Mertens L, Noriega E, Van Impe JF. Effect of cell immobilization on the growth dynamics of Salmonella Typhimurium and Escherichia coli at suboptimal temperatures. Int J Food Microbiol 2015; 208:75-83. [PMID: 26057111 DOI: 10.1016/j.ijfoodmicro.2015.05.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 02/13/2015] [Accepted: 05/23/2015] [Indexed: 11/19/2022]
Abstract
Predictive microbiology has recently acknowledged the impact of the solid(like) food structure on microbial behavior. The presence of this solid(like) structure causes microorganisms to grow as colonies and no longer planktonically as in liquid. In this paper, the growth dynamics of Salmonella Typhimurium and Escherichia coli were studied as a function of temperature, considering different growth morphologies, i.e., (i) planktonic cells, (ii) immersed colonies and (iii) surface colonies. For all three growth morphologies, both microorganisms were grown in petri dishes. While E. coli was grown under optimal pH and water activity (aw), for S. Typhimurium pH and aw were adapted to 5.5 and 0.990. In order to mimic a solid(like) environment, 5% (w/v) gelatin was added. All petri dishes were incubated under static conditions at temperatures in the range [8.0°C-22.0°C]. Cell density was determined via viable plate counting. This work demonstrates that the growth morphology (planktonic vs. colony) has a negligible effect on the growth dynamics as a function of temperature. The observation of almost equal growth rates for planktonic cultures and colonies is in contrast to literature where, mostly, a difference is observed, i.e., μplanktonic cells≥μimmersed colonies≥μsurface colonies. This difference might be due to shaking of the liquid culture in these studies, which results in a nutrient and oxygen rich environment, in contrast to the diffusion-limited gel system. Experiments also indicate that lag phases for solid(like) systems are similar to those for the planktonic cultures, as can be found in literature for similar growth conditions. Considering the maximum cell density, no clear trend was deducted for either of the microorganisms. This study indicates that the growth parameters in the suboptimal temperature range do not depend on the growth morphology. For the considered experimental conditions, models previously developed for liquid environments can be used for solid(like) systems.
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Affiliation(s)
- Cindy Smet
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, Belgium(1); BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Eva Van Derlinden
- BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Laurence Mertens
- BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Estefanía Noriega
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, Belgium(1); BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
| | - Jan F Van Impe
- CPMF(2) - Flemish Cluster Predictive Microbiology in Foods, Belgium(1); BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium.
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Boons K, Noriega E, Van den Broeck R, David CC, Hofkens J, Van Impe JF. Effect of microstructure on population growth parameters of Escherichia coli in gelatin-dextran systems. Appl Environ Microbiol 2014; 80:5330-9. [PMID: 24951795 PMCID: PMC4136113 DOI: 10.1128/aem.00817-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 06/14/2014] [Indexed: 12/20/2022] Open
Abstract
Current literature acknowledges the effect of food structure on bacterial dynamics. Most studies introduce this "structure" factor using a single gelling agent, resulting in a homogeneous environment, whereas in practice most food products are heterogeneous. Therefore, this study focuses on heterogeneous protein-polysaccharide mixtures, based on gelatin and dextran. These mixtures show phase separation, leading to a range of heterogeneous microstructures by adjusting relative concentrations of both gelling agents. Based on confocal microscope observations, the growth of Escherichia coli in gelatin-dextran systems was observed to occur in the dextran phase. To find a relation between microscopic and population behavior, growth experiments were performed in binary and singular gelatin-dextran systems and culture broth at 23.5°C, with or without adding 2.9% (wt/vol) NaCl. The Baranyi and Roberts growth model was fitted to the experimental data and parameter estimates were statistically compared. For salted binary mixtures, a decrease in the population maximum cell density was observed with increasing gelatin concentration. In this series, for one type of microstructure, i.e., a gelatin matrix phase with a disperse dextran phase, the maximum cell density decreased with decreasing percentage of dextran phase. However, this relation no longer held when other types of microstructure were observed. Compared to singular systems, adding a second gelling agent in the presence of NaCl had an effect on population lag phases and maximum cell densities. For unsalted media, the growth parameters of singular and binary mixtures were comparable. Introducing this information into mathematical models leads to more reliable growth predictions and enhanced food safety.
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Affiliation(s)
- Kathleen Boons
- CPMF, Flemish Cluster Predictive Microbiology in Foods, Belgium‡ BioTeC, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium
| | - Estefanía Noriega
- CPMF, Flemish Cluster Predictive Microbiology in Foods, Belgium‡ BioTeC, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium
| | - Rob Van den Broeck
- BioTeC, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium
| | | | - Johan Hofkens
- Molecular Visualization and Photonics, KU Leuven, Leuven, Belgium
| | - Jan F Van Impe
- CPMF, Flemish Cluster Predictive Microbiology in Foods, Belgium‡ BioTeC, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Leuven, Belgium
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Abstract
The evolutionary success of bacteria depends greatly on their capacity to continually generate phenotypic diversity. Structured environments are particularly favorable for diversification because of attenuated clonal interference, which renders selective sweeps nearly impossible and enhances opportunities for adaptive radiation. We examined at the microscale level the emergence and the spatial and temporal dynamics of phenotypic diversity and their underlying causes in Escherichia coli colonies. An important dynamic heterogeneity in the growth, metabolic activity, morphology, gene expression patterns, stress response induction, and death patterns among cells within colonies was observed. Genetic analysis indicated that the phenotypic variation resulted mostly from mutations and that indole production, oxidative stress, and the RpoS-regulated general stress response played an important role in the generation of diversity. We observed the emergence and persistence of phenotypic variants within single colonies that exhibited variable fitness compared to the parental strain. Some variants showed improved capacity to produce biofilms, whereas others were able to use different nutrients or to tolerate antibiotics or oxidative stress. Taken together, our data show that bacterial colonies provide an ecological opportunity for the generation and maintenance of vast phenotypic diversity, which may increase the probability of population survival in unpredictable environments.
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Rosenkrantz JT, Aarts H, Abee T, Rolfe MD, Knudsen GM, Nielsen MB, Thomsen LE, Zwietering MH, Olsen JE, Pin C. Non-essential genes form the hubs of genome scale protein function and environmental gene expression networks in Salmonella enterica serovar Typhimurium. BMC Microbiol 2013; 13:294. [PMID: 24345035 PMCID: PMC3878590 DOI: 10.1186/1471-2180-13-294] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 12/10/2013] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Salmonella Typhimurium is an important pathogen of human and animals. It shows a broad growth range and survives in harsh conditions. The aim of this study was to analyze transcriptional responses to a number of growth and stress conditions as well as the relationship of metabolic pathways and/or cell functions at the genome-scale-level by network analysis, and further to explore whether highly connected genes (hubs) in these networks were essential for growth, stress adaptation and virulence. RESULTS De novo generated as well as published transcriptional data for 425 selected genes under a number of growth and stress conditions were used to construct a bipartite network connecting culture conditions and significantly regulated genes (transcriptional network). Also, a genome scale network was constructed for strain LT2. The latter connected genes with metabolic pathways and cellular functions. Both networks were shown to belong to the family of scale-free networks characterized by the presence of highly connected nodes or hubs which are genes whose transcription is regulated when responding to many of the assayed culture conditions or genes encoding products involved in a high number of metabolic pathways and cell functions.The five genes with most connections in the transcriptional network (wraB, ygaU, uspA, cbpA and osmC) and in the genome scale network (ychN, siiF (STM4262), yajD, ybeB and dcoC) were selected for mutations, however mutagenesis of ygaU and ybeB proved unsuccessful. No difference between mutants and the wild type strain was observed during growth at unfavorable temperatures, pH values, NaCl concentrations and in the presence of H2O2. Eight mutants were evaluated for virulence in C57/BL6 mice and none differed from the wild type strain. Notably, however, deviations of phenotypes with respect to the wild type were observed when combinations of these genes were deleted. CONCLUSION Network analysis revealed the presence of hubs in both transcriptional and functional networks of S. Typhimurium. Hubs theoretically confer higher resistance to random mutation but a greater susceptibility to directed attacks, however, we found that genes that formed hubs were dispensable for growth, stress adaptation and virulence, suggesting that evolution favors non-essential genes as main connectors in cellular networks.
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Affiliation(s)
- Jesper T Rosenkrantz
- Department of Veterinary Disease Biology, University of Copenhagen, Stigbøjlen 4, 1870 Frederiksberg, C, Denmark
| | - Henk Aarts
- Centre for Infectious disease control, National Institute for Public Health, PO box 1, 3720 BA Bilthoven, The Netherlands
| | - Tjakko Abee
- Wageningen University and Research Centre, Laboratory of Food Microbiology, P.O. Box 17, 6700 AA Wageningen, Netherlands
| | - Matthew D Rolfe
- Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK
| | - Gitte M Knudsen
- Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK
- National Food Institute, Danish Technical University, Soelvtofts Plads, 2800 Kgs. Lyngby, Denmark
| | - Maj-Britt Nielsen
- Department of Veterinary Disease Biology, University of Copenhagen, Stigbøjlen 4, 1870 Frederiksberg, C, Denmark
- Present address: DANSTEM Laboratory, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, N, Denmark
| | - Line E Thomsen
- Department of Veterinary Disease Biology, University of Copenhagen, Stigbøjlen 4, 1870 Frederiksberg, C, Denmark
| | - Marcel H Zwietering
- Wageningen University and Research Centre, Laboratory of Food Microbiology, P.O. Box 17, 6700 AA Wageningen, Netherlands
| | - John E Olsen
- Department of Veterinary Disease Biology, University of Copenhagen, Stigbøjlen 4, 1870 Frederiksberg, C, Denmark
| | - Carmen Pin
- Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK
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18
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ClpP deletion causes attenuation of Salmonella Typhimurium virulence through mis-regulation of RpoS and indirect control of CsrA and the SPI genes. Microbiology (Reading) 2013; 159:1497-1509. [DOI: 10.1099/mic.0.065797-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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19
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Comparison of heat stress responses of immobilized and planktonic Salmonella enterica serovar Typhimurium. Food Microbiol 2013. [DOI: 10.1016/j.fm.2012.09.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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20
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Boons K, Van Derlinden E, Mertens L, Peeters V, Van Impe JF. Effect of immobilization and salt concentration on the growth dynamics of Escherichia coli K12 and Salmonella typhimurium. J Food Sci 2013; 78:M567-74. [PMID: 23464757 DOI: 10.1111/1750-3841.12067] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 01/06/2013] [Indexed: 11/29/2022]
Abstract
Up to now, it is generally observed that (i) the microbial growth domain is confined by structure-induced stress, or (ii) a solid(-like) environment can enhance microbial survival/growth. In most studies in solid(-like) systems, structure is induced by the addition of gelatin. The aim of this study was to evaluate the effect of other structure-inducing components on the growth dynamics. Both single and binary gel systems are used. Growth is studied when simultaneously exposed to salt stress. Experiments are performed in spectrophotometer tubes, filled with 1 mL of liquid, or structured inoculated brain heart infusion. Four different (combinations of) gelling agents are tested, that is, gelatin, xanthan gum, a 50% combination of xanthan gum and gelatin, and a 50% combination of carrageenan and gelatin. Experiments determine the growth behavior of both Escherichia coli (0% to 0.5% and 1%, 2%, 3%, 4%, and 5% NaCl) and Salmonella Typhimurium (0%, 1%, 2%, 3%, 4%, and 5% NaCl) at 23.5 and 27 °C. By means of plate counting, the growth dynamics are determined. At the studied conditions, growth of E. coli and Salmonella Typhimurium seems independent of the type of structure-inducing component. However, at higher concentrations of salt (>2%), lag phases are typically shorter in solid(-like) systems than in liquid media. For the conditions tested, the effect of a structured environment on growth rate and maximal cell density can be neglected.
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Affiliation(s)
- Kathleen Boons
- Chemical and Biochemical Process Technology and Control (BioTeC), KU Leuven W. de Croylaan 46, B-3001 Leuven, Belgium
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21
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Waldner LL, MacKenzie KD, Köster W, White AP. From Exit to Entry: Long-term Survival and Transmission of Salmonella. Pathogens 2012; 1:128-55. [PMID: 25436767 PMCID: PMC4235688 DOI: 10.3390/pathogens1020128] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Revised: 09/15/2012] [Accepted: 10/10/2012] [Indexed: 02/01/2023] Open
Abstract
Salmonella spp. are a leading cause of human infectious disease worldwide and pose a serious health concern. While we have an improving understanding of pathogenesis and the host-pathogen interactions underlying the infection process, comparatively little is known about the survival of pathogenic Salmonella outside their hosts. This review focuses on three areas: (1) in vitro evidence that Salmonella spp. can survive for long periods of time under harsh conditions; (2) observations and conclusions about Salmonella persistence obtained from human outbreaks; and (3) new information revealed by genomic- and population-based studies of Salmonella and related enteric pathogens. We highlight the mechanisms of Salmonella persistence and transmission as an essential part of their lifecycle and a prerequisite for their evolutionary success as human pathogens.
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Affiliation(s)
- Landon L Waldner
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E3, Canada.
| | - Keith D MacKenzie
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E3, Canada.
| | - Wolfgang Köster
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E3, Canada.
| | - Aaron P White
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E3, Canada.
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Adaptive acid tolerance response of Listeria monocytogenes strains under planktonic and immobilized growth conditions. Int J Food Microbiol 2012; 159:160-6. [PMID: 22980026 DOI: 10.1016/j.ijfoodmicro.2012.07.027] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 05/31/2012] [Accepted: 07/18/2012] [Indexed: 12/30/2022]
Abstract
The acid resistance of Listeria monocytogenes was evaluated: (i) after short (shock) or long-term (adaptation during growth) exposure to reduced (5.5) or neutral (7.2) pH in a liquid (broth) medium or on a solid surface (agar), and (ii) after growth on the surface of ham and turkey slices or in homogenates of these products. Three L. monocytogenes strains (serotypes 1/2a, 1/2b and 4b) were individually inoculated at: (i) 10(4)-10(5)CFU/ml in tryptic soy broth with 0.6% yeast extract (TSBYE) or on tryptic soy agar with 0.6% yeast extract (TSAYE) at pH 7.2 with 1% (+G) or without (-G) glucose of or TSBYE and TSAYE with 0.25% glucose at pH 5.5 (lactic acid) and incubated at 20°C, and (ii) 10(2)-10(3)CFU/cm(2) on ham and turkey slices (pH 6.39-6.42; formulated with potassium lactate and sodium diacetate) or in their homogenates (1:4 and 1:9; representing viscous [slurry] and liquid residues [purge], respectively), and stored at 10°C. The acid resistance of each strain was assessed in TSBYE of pH 3.5 (lactic acid) for strains growing in broth or on agar surfaces, and in TSBYE of pH 1.5 (HCl) for strains growing on ham and turkey slices or in their homogenates. Habituation at pH 5.5 for 3 or 24h at 20°C increased acid (pH 3.5) resistance of all strains compared to the control (pH 7.2). Cells grown on the surface of TSAYE-G (pH 7.2 or 5.5) showed higher resistance than cells grown in broth (TSBYE-G), whereas the opposite was observed for cells grown on TSAYE + G or in TSBYE + G. Growth of L. monocytogenes on meat product slices was markedly slower than in homogenates. Pathogen reductions following exposure to pH 1.5, after 10 and 27days of storage were strain-dependent and in the ranges of 0.5-2.5, 1.3-4.5 and 4.0-7.6 log units for cells grown on product slices in 1:4 and 1:9 homogenates, respectively. The results suggest that L. monocytogenes cells growing on food surfaces or in viscous matrices may show higher resistance to lethal acid conditions than cells growing in liquid substrates.
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Abstract
Food spoilage may be defined as a process that renders a product undesirable or unacceptable for consumption and is the outcome of the biochemical activity of a microbial community that eventually dominates according to the prevailing ecological determinants. Although limited information are reported, this activity has been attributed to quorum sensing (QS). Consequently, the potential role of cell-to-cell communication in food spoilage and food safety should be more extensively elucidated. Such information would be helpful in designing approaches for manipulating these communication systems, thereby reducing or preventing, for instance, spoilage reactions or even controlling the expression of virulence factors. Due to the many reports in the literature on the fundamental features of QS, e.g., chemistry and definitions of QS compounds, in this minireview, we only allude to the types and chemistry of QS signaling molecules per se and to the (bioassay-based) methods of their detection and quantification, avoiding extensive documentation. Conversely, we attempt to provide insights into (i) the role of QS in food spoilage, (ii) the factors that may quench the activity of QS in foods and review the potential QS inhibitors that might "mislead" the bacterial coordination of spoilage activities and thus may be used as biopreservatives, and (iii) the future experimental approaches that need to be undertaken in order to explore the "gray" or "black" areas of QS, increase our understanding of how QS affects microbial behavior in foods, and assist in finding answers as to how we can exploit QS for the benefit of food preservation and food safety.
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