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Fernández-Fernández R, Olivenza DR, Sánchez-Romero MA. Identifying Bacterial Lineages in Salmonella by Flow Cytometry. EcoSal Plus 2022; 10:eESP00182021. [PMID: 35148202 PMCID: PMC10729938 DOI: 10.1128/ecosalplus.esp-0018-2021] [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: 04/30/2021] [Accepted: 12/21/2021] [Indexed: 12/16/2022]
Abstract
Advances in technologies that permit high-resolution analysis of events in single cells have revealed that phenotypic heterogeneity is a widespread phenomenon in bacteria. Flow cytometry has the potential to describe the distribution of cellular properties within a population of bacterial cells and has yielded invaluable information about the ability of isogenic cells to diversify into phenotypic subpopulations. This review will discuss several single-cell approaches that have recently been applied to define phenotypic heterogeneity in populations of Salmonella enterica.
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Affiliation(s)
| | - David R. Olivenza
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
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2
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Yang S, Tian L, Wang X, Wu M, Liao S, Fu J, Xiong W, Gong G. Metabolomics analysis and membrane damage measurement reveal the antibacterial mechanism of lipoic acid against Yersinia enterocolitica. Food Funct 2022; 13:11476-11488. [PMID: 36178296 DOI: 10.1039/d2fo01306a] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Yersinia enterocolitica is a pathogenic microorganism that can cause food-borne diseases. Lipoic acid (LA) has been used as an antioxidant against bacteria, but its antibacterial mechanism is rarely reported. This study aims to explore the antibacterial mechanism of LA and its effect on the metabolites of Y. enterocolitica through membrane damage and metabolomics analysis. The results showed that the minimum inhibitory concentration (MIC) of LA against Y. enterocolitica was 2.5 mg mL-1. The membrane potential was depolarized, and intracellular pH (pHin) and ATP were significantly reduced, indicating that LA destroys the cell membrane structure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) further confirmed LA-induced cell membrane damage. The metabolic profile of Y. enterocolitica following LA treatment was analyzed by liquid chromatography-mass spectrometry (LC-MS). In the metabolome evaluation, 6209 differential metabolites were screened, including 3394 up-regulated and 2815 down-regulated metabolites. Fifteen metabolic pathways of Y. enterocolitica exhibited significant changes after LA treatment, including the pathways important for amino acid and nucleotide metabolism. The results show that LA is a bacteriostatic substance with potential application value in the food industry.
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Affiliation(s)
- Siqi Yang
- College of Food and Bioengineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi, 710021, China.
| | - Lu Tian
- College of Food and Bioengineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi, 710021, China.
| | - Xuyang Wang
- College of Food and Bioengineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi, 710021, China.
| | - Mi Wu
- College of Food and Bioengineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi, 710021, China.
| | - Sichen Liao
- College of Food and Bioengineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi, 710021, China.
| | - Jiapeng Fu
- College of Food and Bioengineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi, 710021, China.
| | - Wangdan Xiong
- Grassl and Agri-Husbandry Research Center, School of Grassl and Science, Qingdao Agricultural University, Qingdao, Shandong, 266109, China.
| | - Guoli Gong
- College of Food and Bioengineering, Shaanxi University of Science and Technology, Xi'an, Shaanxi, 710021, China.
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3
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Monteiro GP, Rossi DA, Valadares Jr EC, Peres PABM, Braz RF, Notário FO, Gomes MM, Silva RR, Carrijo KF, Fonseca BB. Lactic Bacterium and Bacillus Sp. Biofilms Can Decrease the Viability of Salmonella Gallinarum, Salmonella Heidelberg, Campylobacter Jejuni and Methicillin Resistant Staphylococcus Aureus on Different Substrates. BRAZILIAN JOURNAL OF POULTRY SCIENCE 2021. [DOI: 10.1590/1806-9061-2020-1408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | - DA Rossi
- Universidade Federal de Uberlândia, Brazil
| | | | - PABM Peres
- Universidade Federal de Uberlândia, Brazil
| | - RF Braz
- Universidade Federal de Uberlândia, Brazil
| | - FO Notário
- Universidade Federal de Uberlândia, Brazil
| | - MM Gomes
- Universidade Federal de Uberlândia, Brazil
| | - RR Silva
- Universidade Federal de Uberlândia, Brazil
| | - KF Carrijo
- Universidade Federal de Uberlândia, Brazil
| | - BB Fonseca
- Universidade Federal de Uberlândia, Brazil
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Cho ER, Kim SS, Kang DH. Inactivation Kinetics and Membrane Potential of Pathogens in Soybean Curd Subjected to Pulsed Ohmic Heating Depending on Applied Voltage and Duty Ratio. Appl Environ Microbiol 2020; 86:e00656-20. [PMID: 32385086 PMCID: PMC7357481 DOI: 10.1128/aem.00656-20] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 04/28/2020] [Indexed: 11/20/2022] Open
Abstract
The aim of this research was to investigate the efficacy of the duty ratio and applied voltage in the inactivation of pathogens in soybean curd by pulsed ohmic heating (POH). The heating rate of soybean curd increased rapidly as the applied voltage increased, although the duty ratio did not affect the temperature profile. We supported this result by verifying that electrical conductivity increased with the applied voltage. Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in soybean curd were significantly (P < 0.05) inactivated by more than 1 log unit at 80 Vrms (root mean square voltage). To elucidate the mechanism underlying these results, the membrane potential of the pathogens was examined using DiBAC4(3) [bis-(1,3-dibutylbarbituric acid)trimethine oxonol] on the basis of a previous study showing that the electric field generated by ohmic heating affected the membrane potential of cells. The values of DiBAC4(3) accumulation increased under increasing applied voltage, and they were significantly (P < 0.05) higher at 80 Vrms, while the duty ratio had no effect. In addition, morphological analysis via transmission electron microscopy showed that electroporation and expulsion of intracellular materials were predominant at 80 Vrms Moreover, electrode corrosion was overcome by the POH technique, and the textural and color properties of soybean curd were preserved. These results substantiate the idea that the applied voltage has a profound effect on the microbial inactivation of POH as a consequence of not only the thermal effect, but also the nonthermal effect, of the electric field, whereas the duty ratio does not have such an effect.IMPORTANCE High-water-activity food products, such as soybean curd, are vulnerable to microbial contamination, which causes fatal foodborne diseases and food spoilage. Inactivating microorganisms inside food is difficult because the transfer of thermal energy is slower inside than it is outside the food. POH is an adequate sterilization technique because of its rapid and uniform heating without causing electrode corrosion. To elucidate the electrical factors associated with POH performance in the inactivation of pathogens, the effects of the applied voltage and duty ratio on POH were investigated. In this study, we verified that a high applied voltage (80 Vrms) at a duty ratio of 0.1 caused thermal and nonthermal effects on pathogens that led to an approximately 4-log-unit reduction in a significantly short time. Therefore, the results of this research corroborate database predictions of the inactivation efficiency of POH based on pathogen control strategy modeling.
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Affiliation(s)
- Eun-Rae Cho
- Department of Agricultural Biotechnology, Center for Food and Bioconvergence, and Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul, Republic of Korea
| | - Sang-Soon Kim
- Department of Food Engineering, Dankook University, Cheonan, Chungnam, Republic of Korea
| | - Dong-Hyun Kang
- Department of Agricultural Biotechnology, Center for Food and Bioconvergence, and Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul, Republic of Korea
- Institutes of Green Bio Science and Technology, Seoul National University, Seoul, Republic of Korea
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5
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Boix-Lemonche G, Lekka M, Skerlavaj B. A Rapid Fluorescence-Based Microplate Assay to Investigate the Interaction of Membrane Active Antimicrobial Peptides with Whole Gram-Positive Bacteria. Antibiotics (Basel) 2020; 9:antibiotics9020092. [PMID: 32093104 PMCID: PMC7168298 DOI: 10.3390/antibiotics9020092] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 02/14/2020] [Accepted: 02/17/2020] [Indexed: 01/08/2023] Open
Abstract
Background: Membrane-active antimicrobial peptides (AMPs) are interesting candidates for the development of novel antimicrobials. Although their effects were extensively investigated in model membrane systems, interactions of AMPs with living microbial membranes are less known due to their complexity. The aim of the present study was to develop a rapid fluorescence-based microplate assay to analyze the membrane effects of AMPs in whole Staphylococcus aureus and Staphylococcus epidermidis. Methods: Bacteria were exposed to bactericidal and sub-inhibitory concentrations of two membrane-active AMPs in the presence of the potential-sensitive dye 3,3′-dipropylthiadicarbocyanine iodide (diSC3(5)) and the DNA staining dye propidium iodide (PI), to simultaneously monitor and possibly distinguish membrane depolarization and membrane permeabilization. Results: The ion channel-forming gramicidin D induced a rapid increase of diSC3(5), but not PI fluorescence, with slower kinetics at descending peptide concentrations, confirming killing due to membrane depolarization. The pore-forming melittin, at sub-MIC and bactericidal concentrations, caused, respectively, an increase of PI fluorescence in one or both dyes simultaneously, suggesting membrane permeabilization as a key event. Conclusions: This assay allowed the distinction between specific membrane effects, and it could be applied in the mode of action studies as well as in the screening of novel membrane-active AMPs.
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Affiliation(s)
- Gerard Boix-Lemonche
- Department of Medicine, University of Udine, Piazzale Kolbe, 4, 33100 Udine, Italy
- Correspondence: (G.B.-L.); (B.S.)
| | - Maria Lekka
- Polytechnic Department of Engineering and Architecture, University of Udine, Via delle Scienze 206, 33100 Udine, Italy
| | - Barbara Skerlavaj
- Department of Medicine, University of Udine, Piazzale Kolbe, 4, 33100 Udine, Italy
- Correspondence: (G.B.-L.); (B.S.)
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6
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Jindal S, Yang L, Day PJ, Kell DB. Involvement of multiple influx and efflux transporters in the accumulation of cationic fluorescent dyes by Escherichia coli. BMC Microbiol 2019; 19:195. [PMID: 31438868 PMCID: PMC6704527 DOI: 10.1186/s12866-019-1561-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/31/2019] [Indexed: 12/11/2022] Open
Abstract
Background It is widely believed that most xenobiotics cross biomembranes by diffusing through the phospholipid bilayer, and that the use of protein transporters is an occasional adjunct. According to an alternative view, phospholipid bilayer transport is negligible, and several different transporters may be involved in the uptake of an individual molecular type. We recognise here that the availability of gene knockout collections allows one to assess the contributions of all potential transporters, and flow cytometry based on fluorescence provides a convenient high-throughput assay for xenobiotic uptake in individual cells. Results We used high-throughput flow cytometry to assess the ability of individual gene knockout strains of E coli to take up two membrane-permeable, cationic fluorescent dyes, namely the carbocyanine diS-C3(5) and the DNA dye SYBR Green. Individual strains showed a large range of distributions of uptake. The range of modal steady-state uptakes for the carbocyanine between the different strains was 36-fold. Knockouts of the ATP synthase α- and β-subunits greatly inhibited uptake, implying that most uptake was ATP-driven rather than being driven by a membrane potential. Dozens of transporters changed the steady-state uptake of the dye by more than 50% with respect to that of the wild type, in either direction (increased or decreased); knockouts of known influx and efflux transporters behaved as expected, giving credence to the general strategy. Many of the knockouts with the most reduced uptake were transporter genes of unknown function (‘y-genes’). Similarly, several overexpression variants in the ‘ASKA’ collection had the anticipated, opposite effects. Similar results were obtained with SYBR Green (the range being approximately 69-fold). Although it too contains a benzothiazole motif there was negligible correlation between its uptake and that of the carbocyanine when compared across the various strains (although the membrane potential is presumably the same in each case). Conclusions Overall, we conclude that the uptake of these dyes may be catalysed by a great many transporters of putatively broad and presently unknown specificity, and that the very large range between the ‘lowest’ and the ‘highest’ levels of uptake, even in knockouts of just single genes, implies strongly that phospholipid bilayer transport is indeed negligible. This work also casts serious doubt upon the use of such dyes as quantitative stains for representing either bioenergetic parameters or the amount of cellular DNA in unfixed cells (in vivo). By contrast, it opens up their potential use as transporter assay substrates in high-throughput screening. Electronic supplementary material The online version of this article (10.1186/s12866-019-1561-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Srijan Jindal
- Department of Chemistry, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK
| | - Lei Yang
- Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, 2800 Kgs, Lyngby, Denmark
| | - Philip J Day
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK
| | - Douglas B Kell
- Department of Chemistry, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK. .,Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK. .,Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, 2800 Kgs, Lyngby, Denmark. .,Department of Biochemistry, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool, L69 7ZB, UK.
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7
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Stratford JP, Edwards CLA, Ghanshyam MJ, Malyshev D, Delise MA, Hayashi Y, Asally M. Electrically induced bacterial membrane-potential dynamics correspond to cellular proliferation capacity. Proc Natl Acad Sci U S A 2019; 116:9552-9557. [PMID: 31000597 PMCID: PMC6511025 DOI: 10.1073/pnas.1901788116] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Membrane-potential dynamics mediate bacterial electrical signaling at both intra- and intercellular levels. Membrane potential is also central to cellular proliferation. It is unclear whether the cellular response to external electrical stimuli is influenced by the cellular proliferative capacity. A new strategy enabling electrical stimulation of bacteria with simultaneous monitoring of single-cell membrane-potential dynamics would allow bridging this knowledge gap and further extend electrophysiological studies into the field of microbiology. Here we report that an identical electrical stimulus can cause opposite polarization dynamics depending on cellular proliferation capacity. This was demonstrated using two model organisms, namely Bacillus subtilis and Escherichia coli, and by developing an apparatus enabling exogenous electrical stimulation and single-cell time-lapse microscopy. Using this bespoke apparatus, we show that a 2.5-second electrical stimulation causes hyperpolarization in unperturbed cells. Measurements of intracellular K+ and the deletion of the K+ channel suggested that the hyperpolarization response is caused by the K+ efflux through the channel. When cells are preexposed to 400 ± 8 nm wavelength light, the same electrical stimulation depolarizes cells instead of causing hyperpolarization. A mathematical model extended from the FitzHugh-Nagumo neuron model suggested that the opposite response dynamics are due to the shift in resting membrane potential. As predicted by the model, electrical stimulation only induced depolarization when cells are treated with antibiotics, protonophore, or alcohol. Therefore, electrically induced membrane-potential dynamics offer a reliable approach for rapid detection of proliferative bacteria and determination of their sensitivity to antimicrobial agents at the single-cell level.
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Affiliation(s)
- James P Stratford
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
- Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry, West Midlands, CV4 7AL,United Kingdom
| | - Conor L A Edwards
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Manjari J Ghanshyam
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Dmitry Malyshev
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Marco A Delise
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Yoshikatsu Hayashi
- Department of Biomedical Engineering, School of Biological Sciences, University of Reading, Reading, Berkshire, RG6 6AH, United Kingdom
| | - Munehiro Asally
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom;
- Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry, West Midlands, CV4 7AL,United Kingdom
- Bio-Electrical Engineering Innovation Hub, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
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8
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Cai J, Nichols RG, Koo I, Kalikow ZA, Zhang L, Tian Y, Zhang J, Smith PB, Patterson AD. Multiplatform Physiologic and Metabolic Phenotyping Reveals Microbial Toxicity. mSystems 2018; 3:e00123-18. [PMID: 30417115 PMCID: PMC6222046 DOI: 10.1128/msystems.00123-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 10/11/2018] [Indexed: 02/06/2023] Open
Abstract
The gut microbiota is susceptible to modulation by environmental stimuli and therefore can serve as a biological sensor. Recent evidence suggests that xenobiotics can disrupt the interaction between the microbiota and host. Here, we describe an approach that combines in vitro microbial incubation (isolated cecal contents from mice), flow cytometry, and mass spectrometry- and 1H nuclear magnetic resonance (NMR)-based metabolomics to evaluate xenobiotic-induced microbial toxicity. Tempol, a stabilized free radical scavenger known to remodel the microbial community structure and function in vivo, was studied to assess its direct effect on the gut microbiota. The microbiota was isolated from mouse cecum and was exposed to tempol for 4 h under strict anaerobic conditions. The flow cytometry data suggested that short-term tempol exposure to the microbiota is associated with disrupted membrane physiology as well as compromised metabolic activity. Mass spectrometry and NMR metabolomics revealed that tempol exposure significantly disrupted microbial metabolic activity, specifically indicated by changes in short-chain fatty acids, branched-chain amino acids, amino acids, nucleotides, glucose, and oligosaccharides. In addition, a mouse study with tempol (5 days gavage) showed similar microbial physiologic and metabolic changes, indicating that the in vitro approach reflected in vivo conditions. Our results, through evaluation of microbial viability, physiology, and metabolism and a comparison of in vitro and in vivo exposures with tempol, suggest that physiologic and metabolic phenotyping can provide unique insight into gut microbiota toxicity. IMPORTANCE The gut microbiota is modulated physiologically, compositionally, and metabolically by xenobiotics, potentially causing metabolic consequences to the host. We recently reported that tempol, a stabilized free radical nitroxide, can exert beneficial effects on the host through modulation of the microbiome community structure and function. Here, we investigated a multiplatform phenotyping approach that combines high-throughput global metabolomics with flow cytometry to evaluate the direct effect of tempol on the microbiota. This approach may be useful in deciphering how other xenobiotics directly influence the microbiota.
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Affiliation(s)
- Jingwei Cai
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Robert G. Nichols
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Imhoi Koo
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Zachary A. Kalikow
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Limin Zhang
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
- CAS Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Centre for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences (CAS), Wuhan, China
| | - Yuan Tian
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
- CAS Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Centre for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences (CAS), Wuhan, China
| | - Jingtao Zhang
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Philip B. Smith
- Metabolomics Facility, Huck Institutes of Life Sciences, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Andrew D. Patterson
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
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9
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Lőrincz ÁM, Szeifert V, Bartos B, Ligeti E. New flow cytometry-based method for the assessment of the antibacterial effect of immune cells and subcellular particles. J Leukoc Biol 2018. [DOI: 10.1002/jlb.4ta0817-317r] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Ákos M. Lőrincz
- Department of Physiology; Semmelweis University; Budapest Hungary
| | | | - Balázs Bartos
- Department of Physiology; Semmelweis University; Budapest Hungary
| | - Erzsébet Ligeti
- Department of Physiology; Semmelweis University; Budapest Hungary
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10
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Somani A, Bealin-Kelly F, Axcell B, Smart KA. Impact of Storage Temperature on Lager Brewing Yeast Viability, Glycogen, Trehalose, and Fatty Acid Content. JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS 2018. [DOI: 10.1094/asbcj-2012-0427-01] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Abhishek Somani
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK
| | | | - Barry Axcell
- SABMiller Plc., SABMiller House, Woking, Surrey GU21 6HS, UK
| | - Katherine A. Smart
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK
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11
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Brunet K, Minoza A, Portet S, Beraud G, Rodier MH, Cateau E. A 55-Year-Old French Man With Sudden Hemiparesis and Hemiplegia. Clin Infect Dis 2016. [DOI: 10.1093/cid/civ1191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Jupa R, Didi V, Hejátko J, Gloser V. An improved method for the visualization of conductive vessels in Arabidopsis thaliana inflorescence stems. FRONTIERS IN PLANT SCIENCE 2015; 6:211. [PMID: 25914701 PMCID: PMC4391271 DOI: 10.3389/fpls.2015.00211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/16/2015] [Indexed: 06/04/2023]
Abstract
Dye perfusion is commonly used for the identification of conductive elements important for the study of xylem development as well as precise hydraulic estimations. The tiny size of inflorescence stems, the small amount of vessels in close arrangement, and high hydraulic resistivity delimit the use of the method for quantification of the water conductivity of Arabidopsis thaliana, one of the recently most extensively used plant models. Here, we present an extensive adjustment to the method in order to reliably identify individual functional (conductive) vessels. Segments of inflorescence stems were sealed in silicone tubes to prevent damage and perfused with a dye solution. Our results showed that dyes often used for staining functional xylem elements (safranin, fuchsine, toluidine blue) failed with Arabidopsis. In contrast, Fluorescent Brightener 28 dye solution perfused through segments stained secondary cell walls of functional vessels, which were clearly distinguishable in native cross sections. When compared to identification based on the degree of development of secondary cell walls, identification with the help of dye perfusion revealed a significantly lower number of functional vessels and values of theoretical hydraulic conductivity. We found that lignified but not yet functional vessels form a substantial portion of the xylem in apical and basal segments of Arabidopsis and, thus, significantly affect the analyzed functional parameters of xylem. The presented methodology enables reliable identification of individual functional vessels, allowing thus estimations of hydraulic conductivities to be improved, size distributions and vessel diameters to be refined, and data variability generally to be reduced.
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Affiliation(s)
- Radek Jupa
- Department of Experimental Biology, Faculty of Science, Masaryk UniversityBrno, Czech Republic
| | - Vojtěch Didi
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology, Masaryk UniversityBrno, Czech Republic
| | - Jan Hejátko
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology, Masaryk UniversityBrno, Czech Republic
| | - Vít Gloser
- Department of Experimental Biology, Faculty of Science, Masaryk UniversityBrno, Czech Republic
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13
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Bouix M, Ghorbal S. Rapid assessment of Oenococcus oeni activity by measuring intracellular pH and membrane potential by flow cytometry, and its application to the more effective control of malolactic fermentation. Int J Food Microbiol 2015; 193:139-46. [DOI: 10.1016/j.ijfoodmicro.2014.10.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 10/03/2014] [Accepted: 10/17/2014] [Indexed: 11/28/2022]
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14
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Lloyd D. Encystment in Acanthamoeba castellanii: a review. Exp Parasitol 2014; 145 Suppl:S20-7. [PMID: 24726698 DOI: 10.1016/j.exppara.2014.03.026] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 03/02/2014] [Accepted: 03/04/2014] [Indexed: 10/25/2022]
Abstract
Differentiation of Acanthamoeba castellanii trophozoites involves massive turnover of cellular components and remodelling of organelle structure and function so as to produce a cryptobiotic cell, resistant to desiccation, heat, freezing, and chemical treatments. This review presents a summary of a decade of research on the most studied aspects of the biochemistry of this process, with emphasis on problems of biocide and drug resistances, putative new targets, molecular and cell biology of the process of encystment, and the characteristics of the encysted state. As well as the intrinsic pathogenicity of the organism towards the cornea, and the ability of related species to invade the human brain, its propensity for harbouring and transmitting pathogenic bacteria and viruses is considerable and leads to increasing concerns. The long-term survival and resistance of cysts to drugs and biocides adds another layer of complexity to the problem of their elimination.
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Affiliation(s)
- David Lloyd
- School of Biosciences, Cardiff University, Cardiff, Wales CF10 3AT, UK.
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15
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Neu TR, Lawrence JR. Investigation of microbial biofilm structure by laser scanning microscopy. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2014; 146:1-51. [PMID: 24840778 DOI: 10.1007/10_2014_272] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Microbial bioaggregates and biofilms are hydrated three-dimensional structures of cells and extracellular polymeric substances (EPS). Microbial communities associated with interfaces and the samples thereof may come from natural, technical, and medical habitats. For imaging such complex microbial communities confocal laser scanning microscopy (CLSM) is the method of choice. CLSM allows flexible mounting and noninvasive three-dimensional sectioning of hydrated, living, as well as fixed samples. For this purpose a broad range of objective lenses is available having different working distance and resolution. By means of CLSM the signals detected may originate from reflection, autofluorescence, reporter genes/fluorescence proteins, fluorochromes binding to specific targets, or other probes conjugated with fluorochromes. Recorded datasets can be used not only for visualization but also for semiquantitative analysis. As a result CLSM represents a very useful tool for imaging of microbiological samples in combination with other analytical techniques.
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Affiliation(s)
- Thomas R Neu
- Department of River Ecology, Helmholtz Centre for Environmental Research-UFZ, Brueckstrasse 3a, 39114, Magdeburg, Germany,
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Vukanti R, Model MA, Leff LG. Effect of modeled reduced gravity conditions on bacterial morphology and physiology. BMC Microbiol 2012; 12:4. [PMID: 22239851 PMCID: PMC3274431 DOI: 10.1186/1471-2180-12-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 01/12/2012] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Bacterial phenotypes result from responses to environmental conditions under which these organisms grow; reduced gravity has been demonstrated in many studies as an environmental condition that profoundly influences microorganisms. In this study, we focused on low-shear stress, modeled reduced gravity (MRG) conditions and examined, for Escherichia coli and Staphlyococcus aureus, a suite of bacterial responses (including total protein concentrations, biovolume, membrane potential and membrane integrity) in rich and dilute media and at exponential and stationary phases for growth. The parameters selected have not been studied in E. coli and S. aureus under MRG conditions and provide critical information about bacterial viability and potential for population growth. RESULTS With the exception of S. aureus in dilute Luria Bertani (LB) broth, specific growth rates (based on optical density) of the bacteria were not significantly different between normal gravity (NG) and MRG conditions. However, significantly higher bacterial yields were observed for both bacteria under MRG than NG, irrespective of the medium with the exception of E. coli grown in LB. Also, enumeration of cells after staining with 4',6-diamidino-2-phenylindole showed that significantly higher numbers were achieved under MRG conditions during stationary phase for E. coli and S. aureus grown in M9 and dilute LB, respectively. In addition, with the exception of smaller S. aureus volume under MRG conditions at exponential phase in dilute LB, biovolume and protein concentrations per cell did not significantly differ between MRG and NG treatments. Both E. coli and S. aureus had higher average membrane potential and integrity under MRG than NG conditions; however, these responses varied with growth medium and growth phase. CONCLUSIONS Overall, our data provides novel information about E. coli and S. aureus membrane potential and integrity and suggest that bacteria are physiologically more active and a larger percentage are viable under MRG as compared to NG conditions. In addition, these results demonstrate that bacterial physiological responses to MRG conditions vary with growth medium and growth phase demonstrating that nutrient resources are a modulator of response.
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Affiliation(s)
- Raja Vukanti
- Department of Biological Sciences, Kent State University, PO Box 5190, Kent, OH 44242, USA
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17
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Extracts of edible and medicinal plants damage membranes of Vibrio cholerae. Appl Environ Microbiol 2010; 76:6888-94. [PMID: 20802077 DOI: 10.1128/aem.03052-09] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The use of natural compounds from plants can provide an alternative approach against food-borne pathogens. The mechanisms of action of most plant extracts with antimicrobial activity have been poorly studied. In this work, changes in membrane integrity, membrane potential, internal pH (pH(in)), and ATP synthesis were measured in Vibrio cholerae cells after exposure to extracts of edible and medicinal plants. A preliminary screen of methanolic, ethanolic, and aqueous extracts of medicinal and edible plants was performed. Minimal bactericidal concentrations (MBCs) were measured for extracts showing high antimicrobial activity. Our results indicate that methanolic extracts of basil (Ocimum basilicum L.), nopal cactus (Opuntia ficus-indica var. Villanueva L.), sweet acacia (Acacia farnesiana L.), and white sagebrush (Artemisia ludoviciana Nutt.) are the most active against V. cholera, with MBCs ranging from 0.5 to 3.0 mg/ml. Using four fluorogenic techniques, we studied the membrane integrity of V. cholerae cells after exposure to these four extracts. Extracts from these plants were able to disrupt the cell membranes of V. cholerae cells, causing increased membrane permeability, a clear decrease in cytoplasmic pH, cell membrane hyperpolarization, and a decrease in cellular ATP concentration in all strains tested. These four plant extracts could be studied as future alternatives to control V. cholerae contamination in foods and the diseases associated with this microorganism.
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Müller S, Nebe-von-Caron G. Functional single-cell analyses: flow cytometry and cell sorting of microbial populations and communities. FEMS Microbiol Rev 2010; 34:554-87. [DOI: 10.1111/j.1574-6976.2010.00214.x] [Citation(s) in RCA: 266] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Jepras RI, Carter J, Pearson SC, Paul FE, Wilkinson MJ. Development of a robust flow cytometric assay for determining numbers of viable bacteria. Appl Environ Microbiol 2010; 61:2696-701. [PMID: 16535078 PMCID: PMC1388496 DOI: 10.1128/aem.61.7.2696-2701.1995] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several fluorescent probes were evaluated as indicators of bacterial viability by flow cytometry. The probes monitor a number of biological factors that are altered during loss of viability. The factors include alterations in membrane permeability, monitored by using fluorogenic substrates and fluorescent intercalating dyes such as propidium iodide, and changes in membrane potential, monitored by using fluorescent cationic and anionic potential-sensitive probes. Of the fluorescent reagents examined, the fluorescent anionic membrane potential probe bis-(1,3-dibutylbarbituric acid)trimethine oxonol [DiBAC(inf4)(3)] proved the best candidate for use as a general robust viability marker and is a promising choice for use in high-throughput assays. With this probe, live and dead cells within a population can be identified and counted 10 min after sampling. There was a close correlation between viable counts determined by flow cytometry and by standard CFU assays for samples of untreated cells. The results indicate that flow cytometry is a sensitive analytical technique that can rapidly monitor physiological changes of individual microorganisms as a result of external perturbations. The membrane potential probe DiBAC(inf4)(3) provided a robust flow cytometric indicator for bacterial cell viability.
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Cronin U, Wilkinson M. The potential of flow cytometry in the study of Bacillus cereus. J Appl Microbiol 2010; 108:1-16. [DOI: 10.1111/j.1365-2672.2009.04370.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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21
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Harrington BJ. The Staining of Oocysts ofCryptosporidiumWith the Fluorescent Brighteners Uvitex 2B and Calcofluor White. Lab Med 2009. [DOI: 10.1309/lm8pt49nzvvyoncb] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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22
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Davey HM, Kell DB, Weichart DH, Kaprelyants AS. Estimation of microbial viability using flow cytometry. ACTA ACUST UNITED AC 2008; Chapter 11:Unit 11.3. [PMID: 18770790 DOI: 10.1002/0471142956.cy1103s29] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
For microorganisms in particular, viability is a term that is difficult to define and a state consequently difficult to measure. The traditional (and gold-standard) usage equates viability and culturability (i.e., the ability to multiply), but the process of determining culturability is often too slow. Flow cytometry provides the opportunity to make rapid and quantitative measurements of dye uptake in large numbers of cells, and we can therefore exploit the flow cytometric approach to evaluate so-called viability stains and to develop protocols for more routine assessments of microbial viability. This unit is primarily commentary, but several basic protocols have been included to ensure that users have a firm basis for attempting these reasonably difficult assays on traditional flow cytometer instruments. What is clear is that each assay must be carefully validated with the particular microorganism of interest before being applied in any research, clinical, or service form.
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Falcioni T, Papa S, Campana R, Manti A, Battistelli M, Baffone W. State transitions of Vibrio parahaemolyticus VBNC cells evaluated by flow cytometry. CYTOMETRY PART B-CLINICAL CYTOMETRY 2008; 74:272-81. [PMID: 18500741 DOI: 10.1002/cyto.b.20427] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Vibrio parahaemolyticus, in response to environmental conditions, may be present in a viable but nonculturable state (VBNC), which can still be responsible for cases of infectious diseases in humans. METHODS The characterization of the cellular states of V. parahaemolyticus during entry into, persistence in, and resuscitation from the VBNC state, was assessed through plate culture method and epifluorescence microscope evaluation of actively respiring cells. Flow cytometry (FCM) in combination with SYBR Green I (SG) and propidium iodide allowed us to distinguish between viable, dead, and damaged-cells. Immunofluorescence labeling detected by FCM was used to study changes in antibody affinity. RESULTS Two groups of bacteria, one with High Nucleic Acid (HNA) and one having Low Nucleic Acid (LNA) content, were differentiated using SG and FCM and each was correlated with cell viability. With the aging of the microcosm, the LNA bacteria population increased while the HNA population gradually disappeared. Cytofluorimetric immunofluorescence analyses showed that the bacterial cell levels dropped from 95% at day 0 to 40% at day 26 and by day 29, antibody affinity was virtually lost. FCM analyses of light scatter signals expressed by cell population highlighted morphological changes indicating a reduction in cell size, as also shown by scanning electron microscopy images and variations in cell structure. CONCLUSIONS The methodology used has provided useful data in relation to the state transitions of V. parahaemolyticus regarding cell viability, antigenic surface components, and the quantification of morphological variations during its entry into the VBNC state.
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Affiliation(s)
- Tania Falcioni
- Centro di Citometria e Citomorfologia, Università Carlo Bo, Urbino, Italy
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Porter J. Flow cytometry and environmental microbiology. CURRENT PROTOCOLS IN CYTOMETRY 2008; Chapter 11:Unit 11.2. [PMID: 18770789 DOI: 10.1002/0471142956.cy1102s27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This survey unit discusses many of the issues involved for flow cytometry in the field of microbiology, particularly the preparative procedures, which are far more stringent than many other procedures using larger cells. For instance, it is often necessary to filter laboratory agents multiple times to obtain the true particle-free solutions needed for flow cytometry of microbes. It is difficult enough to recognize bacteria in cell extracts from soil, sediment, or sludge given the background of same-size particles. This unit provides an excellent overview of a potentially large application area in flow cytometry and is written by one of the most respected scientists in the field.
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Hansen AA, Herbert RA, Mikkelsen K, Jensen LL, Kristoffersen T, Tiedje JM, Lomstein BA, Finster KW. Viability, diversity and composition of the bacterial community in a high Arctic permafrost soil from Spitsbergen, Northern Norway. Environ Microbiol 2008; 9:2870-84. [PMID: 17922769 DOI: 10.1111/j.1462-2920.2007.01403.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The viable and non-viable fractions of the bacterial community in a 2347-year-old permafrost soil from Spitsbergen were subjected to a comprehensive investigation using culture-independent and culture-dependent methods. LIVE/DEAD BacLight staining revealed that 26% of the total number of bacterial cells were viable. Quantitatively, aerobic microcolonies, aerobic colony-forming units and culturable anaerobic bacteria comprised a minor fraction of the total number of viable bacteria, which underlines the necessity for alternative cultivation approaches in bacterial cryobiology. Sulfate reduction was detected at temperatures between -2 degrees C and 29 degrees C while methanogenesis was not detected. Bacterial diversity was high with 162 operational taxonomic units observed from 800 16S rDNA clone sequences. The 158 pure cultures isolated from the permafrost soil affiliated with 29 different bacterial genera, the majority of which have not previously been isolated from permafrost habitats. Most of the strains isolated were affiliated to the genera Cellulomonas and Arthrobacter and several of the pure cultures were closely related to bacteria reported from other cryohabitats. Characterization of viable bacterial communities in permafrost soils is important as it will enable identification of functionally important groups together with the as yet undescribed adaptations that bacteria have evolved for surviving subzero temperatures for millennia.
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Affiliation(s)
- Aviaja A Hansen
- Department of Biological Sciences, Section for Microbiology, University of Aarhus, Denmark
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Evaluating the flow-cytometric nucleic acid double-staining protocol in realistic situations of planktonic bacterial death. Appl Environ Microbiol 2008; 74:1767-79. [PMID: 18223113 DOI: 10.1128/aem.01668-07] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Since heterotrophic prokaryotes play an important biogeochemical role in aquatic ecosystems and have a high capacity to survive in extreme environments, easy-to-perform protocols that probe their physiological states and the effects of environmental variables on those states are highly desired. Some methodologies combine a general nucleic acid stain with a membrane integrity probe. We calibrated one of these, the nucleic acid double-staining (NADS) protocol (G. Grégori, S. Citterio, A. Ghiani, M. Labra, S. Sgorbati, S. Brown, and M. Denis, Appl. Environ. Microbiol. 67:4662-4670, 2001), determining the optimal stain concentrations in seawater and the response to conditions that generate prokaryote death (such as heat) and to conditions that are known to produce death in plankton, such as nutrient limitation or flagellate grazing. The protocol was validated by comparison to two methods used to detect viability: active respiration by 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and incorporation of tritiated leucine. We show that concentrations in the range of 5 to 20 microg ml(-1) of propidium iodide, simultaneous to a 10x concentration of Sybr green I, are best for detecting two separated populations of "live" (green cells) and "dead" (red cells) organisms. During exposure to heat and UVC, we observed that the number of live cells declined concurrently with that of actively respiring cells (CTC positive) and with total leucine incorporation. In seawater mesocosms, the NADS protocol allowed detection of bacterioplankton starvation-related death and flagellate predation. The protocol was also tested in deep profiles in the northwest Atlantic, demonstrating its potential for routine characterization of this fraction of the physiological diversity of marine heterotrophic prokaryotic plankton.
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Mann TS, Mikkelsen SR. Antibiotic Susceptibility Testing at a Screen-Printed Carbon Electrode Array. Anal Chem 2008; 80:843-8. [DOI: 10.1021/ac701829c] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Thomas S. Mann
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
| | - Susan R. Mikkelsen
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
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Johnson-White B, Lin B, Ligler FS. Combination of immunosensor detection with viability testing and confirmation using the polymerase chain reaction and culture. Anal Chem 2007; 79:140-6. [PMID: 17194131 DOI: 10.1021/ac061229l] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rapid and accurate differential determination of viable versus nonviable microbes is critical for formulation of an appropriate response after pathogen detection. Sensors for rapid bacterial identification can be used for applications ranging from environmental monitoring and homeland defense to food process monitoring, but few provide viability information. This study combines the rapid screening capability of the array biosensor using an immunoassay format with methods for determination of viability. Additionally, cells captured by the immobilized antibodies can be cultured following fluorescence imaging to further confirm viability and for cell population expansion for further characterization, e.g., strain identification or antibiotic susceptibility testing. Finally, we demonstrate analysis of captured bacteria using the polymerase chain reaction (PCR). PCR results for waveguide-captured cells were 3 orders of magnitude more sensitive than the fluorescence immunoassay and can also provide additional genetic information on the captured microbes. These approaches can be used to rapidly detect and distinguish viable versus nonviable and pathogenic versus nonpathogenic captured organisms, provide culture materials for further analysis on a shorter time scale, and assess the efficacy of decontamination or sterilization procedures.
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Affiliation(s)
- Brandy Johnson-White
- Center for Bio/Molecular Science & Engineering, Naval Research Laboratory, Washington, D.C. 20375-0001, USA
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29
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Manini E, Danovaro R. Synoptic determination of living/dead and active/dormant bacterial fractions in marine sediments. FEMS Microbiol Ecol 2006; 55:416-23. [PMID: 16466380 DOI: 10.1111/j.1574-6941.2005.00042.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The most widely used methods for the estimation of the living/dead fractions of bacterial cells involve specific stains that are able to reveal membrane integrity. Here, we have compared two different probes (propidium iodide and ethidium homodimer-2) that have different molecular weights and steric hindrance effects. We have also combined this method with the staining/destaining procedure that is currently used in the identification of potentially active cells. The procedure for marine sediments described here allows the synoptic (i.e. from the same filter) identification of: (i) the number of living bacteria; (ii) the number of active vs. dormant cells within this living fraction; (iii) the bacterial fraction with an intact nucleoid region without membrane integrity; and (iv) dead cells (devoid of the nucleoid region and without membrane integrity). Our results demonstrate that the concentration of propidium is crucial for the correct estimation of the dead bacterial fraction, ethidium homodimer-2 allows efficient and accurate estimates that are independent of the concentrations used and the sample storage. The active bacterial fraction represented c. 40% of the total bacterial abundance, the inactive/dormant fraction c. 30%, and the dead fraction was, on average, c. 30%. This method allows the processing of a large number of samples with high precision and at relatively low cost, and thus it provides additional synoptic insights into the metabolic state of bacteria in marine sediments.
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Affiliation(s)
- E Manini
- Department of Marine Science, University Polytechnic of Marche, Ancona, Italy
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Delgado-Viscogliosi P, Simonart T, Parent V, Marchand G, Dobbelaere M, Pierlot E, Pierzo V, Menard-Szczebara F, Gaudard-Ferveur E, Delabre K, Delattre JM. Rapid method for enumeration of viable Legionella pneumophila and other Legionella spp. in water. Appl Environ Microbiol 2005; 71:4086-96. [PMID: 16000824 PMCID: PMC1169006 DOI: 10.1128/aem.71.7.4086-4096.2005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A sensitive and specific method has been developed to enumerate viable L. pneumophila and other Legionella spp. in water by epifluorescence microscopy in a short period of time (a few hours). This method allows the quantification of L. pneumophila or other Legionella spp. as well as the discrimination between viable and nonviable Legionella. It simultaneously combines the specific detection of Legionella cells using antibodies and a bacterial viability marker (ChemChrome V6), the enumeration being achieved by epifluorescence microscopy. The performance of this immunological double-staining (IDS) method was investigated in 38 natural filterable water samples from different aquatic sources, and the viable Legionella counts were compared with those obtained by the standard culture method. The recovery rate of the IDS method is similar to, or higher than, that of the conventional culture method. Under our experimental conditions, the limit of detection of the IDS method was <176 Legionella cells per liter. The examination of several samples in duplicates for the presence of L. pneumophila and other Legionella spp. indicated that the IDS method exhibits an excellent intralaboratory reproducibility, better than that of the standard culture method. This immunological approach allows rapid measurements in emergency situations, such as monitoring the efficacy of disinfection shock treatments. Although its field of application is as yet limited to filterable waters, the double-staining method may be an interesting alternative (not equivalent) to the conventional standard culture methods for enumerating viable Legionella when rapid detection is required.
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Floriano PN, Christodoulides N, Romanovicz D, Bernard B, Simmons GW, Cavell M, McDevitt JT. Membrane-based on-line optical analysis system for rapid detection of bacteria and spores. Biosens Bioelectron 2005; 20:2079-88. [PMID: 15741078 DOI: 10.1016/j.bios.2004.08.046] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 08/06/2004] [Accepted: 08/24/2004] [Indexed: 10/26/2022]
Abstract
We report here the adaptation of our electronic microchip technology towards the development of a new method for detecting and enumerating bacterial cells and spores. This new approach is based on the immuno-localization of bacterial spores captured on a membrane filter microchip placed within a flow cell. A combination of microfluidic, optical, and software components enables the integration of staining of the bacterial species with fully automated assays. The quantitation of the analyte signal is achieved through the measurement of a collective response or alternatively through the identification and counting of individual spores and particles. This new instrument displays outstanding analytical characteristics, and presents a limit of detection of approximately 500 spores when tested with Bacillus globigii (Bg), a commonly used simulant for Bacillus anthracis (Ba), with a total analysis time of only 5 min. Additionally, the system performed well when tested with real postal dust samples spiked with Bg in the presence of other common contaminants. This new approach is highly customizable towards a large number of relevant toxic chemicals, environmental factors, and analytes of relevance to clinical chemistry applications.
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Affiliation(s)
- Pierre N Floriano
- Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712, USA
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Stress-induced physiological responses to starvation periods as well as glucose and lactose pulses in Bacillus licheniformis CCMI 1034 continuous aerobic fermentation processes as measured by multi-parameter flow cytometry. Biochem Eng J 2005. [DOI: 10.1016/j.bej.2005.01.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Reis A, da Silva TL, Kent CA, Kosseva M, Roseiro JC, Hewitt CJ. Monitoring population dynamics of the thermophilic Bacillus licheniformis CCMI 1034 in batch and continuous cultures using multi-parameter flow cytometry. J Biotechnol 2005; 115:199-210. [PMID: 15607238 DOI: 10.1016/j.jbiotec.2004.08.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Revised: 08/26/2004] [Accepted: 08/30/2004] [Indexed: 11/19/2022]
Abstract
Multi-parameter flow cytometry was used to monitor the population dynamics of Bacillus licheniformis continuous cultivations and the physiological responses to a starvation period and a glucose pulse. Using a mixture of two specific fluorescent stains, DiOC6(3) (3,3'-dihexylocarbocyanine iodide), and PI (propidium iodide), flow cytometric analysis revealed cell physiological heterogeneity. Four sub-populations of cells could be easily identified based on their differential fluorescent staining, these correspond to healthy cells (A) stained with DiOC6(3); cells or spores with a depolarised cytoplasmic membrane (B), no staining; cells with a permeabilised depolarised cytoplasmic membrane (C), stained with PI; and permeablised cells with a disrupted cytoplasmic membrane 'ghost cells' (D), stained with both DiOC6(3) and PI. Transmission electron micrographs of cells starved of energy showed different cell lysis process stages, highlighting 'ghost cells' which were associated with the double stained sub-population. It was shown, at the individual cell level, that there was a progressive inherent fluctuation in physiological heterogeneity in response to changing environmental conditions. All four sub-populations were shown to be present during glucose-limited continuous cultures, revealing a higher physiological stress level when compared with a glucose pulsed batch. A starvation period (batch without additional nutrients) increased the number of cells in certain sub-populations (cells with depolarised cytoplasmic membranes and cells with permeabilised depolarised cytoplasmic membranes), indicating that such stress may be caused by glucose limitation. Such information could be used to enhance process efficiency.
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Affiliation(s)
- Alberto Reis
- Instituto Nacional de Engenharia e Tecnologia Industrial, Departamento de Biotecnologia, Estrada do Paço do Lumiar, 22, 1649-038 Lisboa codex, Portugal.
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Laflamme C, Ho J, Veillette M, de Latrémoille MC, Verreault D, Mériaux A, Duchaine C. Flow cytometry analysis of germinating Bacillus spores, using membrane potential dye. Arch Microbiol 2004; 183:107-12. [PMID: 15611861 DOI: 10.1007/s00203-004-0750-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Revised: 11/11/2004] [Accepted: 11/15/2004] [Indexed: 10/26/2022]
Abstract
Germination of Bacillus anthracis spores is necessary for the transcription of plasmidic genes essential to the infection. Assessing germination potential is crucial to predict the risk associated with pathogenic Bacillus exposure. The aim of this study was to set up a viability assay based on membrane potential in order to predict the earliest germination event of spores. B. cereus and two strains of B. subtilis were used. The spores were isolated with a sodium bromide gradient. Approximately 10(7) spores were incubated at 37 degrees C in tryptic soy broth (TSB). Aliquots were harvested at predetermined times and stained with 3,3'-dihexyloxacarbocyanine iodide [DiOC(6)(3)] or with bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC(4)(3)]. Fluorescence characteristics were obtained using flow cytometry. The earliest detectable activation of membrane potential occurred after 15 min of incubation in TSB using DiOC(6)(3). Using DiBAC(4)(3), the earliest detectable signal was after 4 h of incubation. Control experiments using carbonyl cyanide m-chlorophenylhydrazone (CCCP)-treated spores did not show any change in the fluorescence intensity over time. Since no membrane potential and no germination were detected in CCCP-treated spores, the activation of membrane potential seems to be associated with germination. DiOC(6)(3) can be used as an early membrane potential indicator for spores. DiBAC(4)(3), by contrast, is not a early membrane potential marker.
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Affiliation(s)
- Christian Laflamme
- Institut Universitaire de cardiologie et de pneumologie, Centre de recherche Hôpital Laval, Université Laval, 2725 Chemin Ste-Foy, Ste-Foy, QC, Canada, G1V 4G5
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Strathmann M, Wingender J. Use of an oxonol dye in combination with confocal laser scanning microscopy to monitor damage to Staphylococcus aureus cells during colonisation of silver-coated vascular grafts. Int J Antimicrob Agents 2004; 24:234-40. [PMID: 15325426 DOI: 10.1016/j.ijantimicag.2003.03.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2003] [Accepted: 03/10/2004] [Indexed: 10/26/2022]
Abstract
The antimicrobial silver-coating of medical prostheses is regarded as a means to reduce the risk of bacterial colonisation after implantation. The effect of a silver-coating of vascular grafts on biofilm formation was assessed in batch cultures of Staphylococcus aureus, using confocal laser scanning microscopy. Total cells in biofilms were analysed by staining with the DNA-binding fluorochrome SYTO 62 and the proportion of damaged cells was quantified with the membrane potential-sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol. Both the extent of biofilm formation and the proportion of viable biofilm cells were significantly diminished on the surface of the silver-coated vascular grafts compared with uncoated controls, probably due to the antimicrobial activity of silver ions released from the silver-coated graft surface.
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Affiliation(s)
- Martin Strathmann
- Department of Aquatic Microbiology, Institute for Interface Biotechnology, University of Duisburg-Essen, Geibelstrasse 41, 47057 Duisburg, Germany
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37
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Haidinger W, Szostak MP, Jechlinger W, Lubitz W. Online monitoring of Escherichia coli ghost production. Appl Environ Microbiol 2003; 69:468-74. [PMID: 12514029 PMCID: PMC152429 DOI: 10.1128/aem.69.1.468-474.2003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Controlled expression of cloned phi X174 gene E in gram-negative bacteria results in lysis of the bacteria by the formation of a transmembrane tunnel structure built through the cell envelope complex. Production of bacterial ghosts is routinely monitored by classical microbiological procedures. These include determination of the turbidity of the culture and the total number of cells and the number of reproductive cells present during the time course of growth and lysis. Although conceptually simple, these methods are labor intensive and time consuming, providing a complete set of results after the determination of viable cell counts. To avoid culturing methods for bacterial growth, an alternative flow cytometric procedure is presented for the quantification of ghosts and polarized, as well as depolarized, nonlysed cells within a culture. For this method, which is based on the discriminatory power of the membrane potential-sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol, a staining protocol was developed and optimized for the maximum discrepancy in fluorescence between bacterial ghosts and viable cells. The total quantitative analysis procedure takes less than 2 min. The results derived from classical or cytometric analyses correlate with respect to the total cell numbers and the viability of the culture.
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38
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Braga PC, Bovio C, Culici M, Dal Sasso M. Flow cytometric assessment of susceptibilities of Streptococcus pyogenes to erythromycin and rokitamycin. Antimicrob Agents Chemother 2003; 47:408-12. [PMID: 12499226 PMCID: PMC148962 DOI: 10.1128/aac.47.1.408-412.2003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of erythromycin (a 14-membered ring macrolide) and rokitamycin (a 16-membered ring macrolide) on the viability of the Streptococcus pyogenes M phenotype were studied by means of flow cytometry and fluorescence microscopy by using a combination of two fluorochromes (syto 9 and propidium iodide) that stains live bacteria green and dead bacteria red. In order to apply the flow cytometry, a bacterial sonication procedure was expressly set up to separate single cells from the long, intralaced S. pyogenes chains of up to 30 to 40 cells that have previously prevented the application of flow cytometry to this type of bacteria. The association of flow cytometry using an appropriate sonication procedure, together with a combination of fluorescent probes, offered the possibility of very quickly investigating the different microbiological effects of rokitamycin at 2 microg/ml, which was active on the S. pyogenes M phenotype, and of erythromycin at doses of up to 32 microg/ml, which was not.
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Affiliation(s)
- Pier Carlo Braga
- Center of Respiratory Pharmacology, Department of Pharmacology, School of Medicine, University of Milan, Milan, Italy.
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39
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Amor KB, Breeuwer P, Verbaarschot P, Rombouts FM, Akkermans ADL, De Vos WM, Abee T. Multiparametric flow cytometry and cell sorting for the assessment of viable, injured, and dead bifidobacterium cells during bile salt stress. Appl Environ Microbiol 2002; 68:5209-16. [PMID: 12406706 PMCID: PMC129875 DOI: 10.1128/aem.68.11.5209-5216.2002] [Citation(s) in RCA: 188] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2002] [Accepted: 08/05/2002] [Indexed: 11/20/2022] Open
Abstract
Using a flow cytometry-based approach, we assessed the viability of Bifidobacterium lactis DSM 10140 and Bifidobacterium adolescentis DSM 20083 during exposure to bile salt stress. Carboxyfluorescein diacetate (cFDA), propidium iodide (PI), and oxonol [DiBAC4(3)] were used to monitor esterase activity, membrane integrity, and membrane potential, respectively, as indicators of bacterial viability. Single staining with these probes rapidly and noticeably reflected the behavior of the two strains during stress exposure. However, the flow cytometry results tended to overestimate the viability of the two strains compared to plate counts, which appeared to be related to the nonculturability of a fraction of the population as a result of sublethal injury caused by bile salts. When the cells were simultaneously stained with cFDA and PI, flow cytometry and cell sorting revealed a striking physiological heterogeneity within the stressed bifidobacterium population. Three subpopulations could be identified based on their differential uptake of the probes: cF-stained, cF and PI double-stained, and PI-stained subpopulations, representing viable, injured, and dead cells, respectively. Following sorting and recovery, a significant fraction of the double-stained subpopulation (40%) could resume growth on agar plates. Our results show that in situ assessment of the physiological activity of stressed bifidobacteria using multiparameter flow cytometry and cell sorting may provide a powerful and sensitive tool for assessment of the viability and stability of probiotics.
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Affiliation(s)
- Kaouther Ben Amor
- Laboratory of Food Microbiology, Wageningen University, EV 6700 Wageningen, The Netherlands
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40
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Assaraf MP, Ginzburg C, Katan J. Weakening and Delayed Mortality of Fusarium oxysporum by Heat Treatment: Flow Cytometry and Growth Studies. PHYTOPATHOLOGY 2002; 92:956-963. [PMID: 18944020 DOI: 10.1094/phyto.2002.92.9.956] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT Survival of Fusarium oxysporum f. sp. niveum following heat treatments was studied using flow cytometric, physiological, and microscopic assays. We exposed germinating conidia to sublethal temperatures from 36 to 42 degrees C for 60 min, followed by rhodamine 123 staining and flow cytometry, and found increasing levels of fluorescence that reflect a change in mitochondrial membrane potential, indicating a weakening induced by stress. Viability of conidia or germinating conidia of the fungus exposed to heat decreased with increasing temperature, as assessed by fluorescent staining. However, viability was higher than that assessed with the 5-day-long plate count method and was further reduced 13 and 24 h after treatment, suggesting delayed mortality of the heat-treated germinating conidia. Delayed mortality was substantiated by observing these conidia with light and fluorescent scanning electron microscopy and by subculturing single germinating conidia that had been previously heated. Programmed cell death was not observed in heat-treated conidia or germinating conidia of F. oxysporum based on the detection of plasma membrane phosphatidylserine translocation, cell-cycle measurements, detection of DNA fragmentation, or microscopic observation of apoptotic bodies. We hypothesize that propagules, which survived the heating and apparently are alive, may undergo further irreversible detrimental processes, eventually leading to their death by yet unidentified mechanisms. These findings suggest that pathogen propagules also might be affected under lower temperatures, possibly facilitating pathogen control by heating.
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41
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Abstract
Confocal microscopy offers several advantages over other conventional microscopic techniques as a tool for studying the interaction of bacteria with food and the role of food microstructure in product quality and safety. When using confocal microscopy, samples can be observed without extensive preparation processes, which allows for the evaluation of food without introducing artifacts. In addition, observations can be made in three dimensions without physically sectioning the specimen. The confocal microscope can be used to follow changes over a period of time, such as the development of the food structure or changes in microbial population during a process. Microbial attachment to and detachment from food and food contact surfaces with complex three-dimensional (3-D) structures can be observed in situ. The fate of microbial populations in food system depends on processing, distribution, and storage conditions as well as decontamination procedures that are applied to inactivate and remove them. The ability to determine the physiological status of microorganisms without disrupting their physical relationship with a food system can be useful for determining the means by which microorganisms survive decontamination treatments. Conventional culturing techniques can detect viable cells; however, these techniques lack the ability to locate viable cells in respect to the microscopic structures of food. Various microscopic methods take advantage of physiological changes in bacterial cells that are associated with the viability to assess the physiologic status of individual cells while retaining the ability to locate the cell within a food tissue system. This paper reviews the application of confocal microscopy in food research and direct observation of viable bacteria with emphasis on their use in food microbiology.
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Affiliation(s)
- K Takeuchi
- Center for Food Safety, Department of Food Science and Technology, University of Georgia, Athens 30602-2106, USA
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Grégori G, Citterio S, Ghiani A, Labra M, Sgorbati S, Brown S, Denis M. Resolution of viable and membrane-compromised bacteria in freshwater and marine waters based on analytical flow cytometry and nucleic acid double staining. Appl Environ Microbiol 2001; 67:4662-70. [PMID: 11571170 PMCID: PMC93217 DOI: 10.1128/aem.67.10.4662-4670.2001] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The membrane integrity of a cell is a well-accepted criterion for characterizing viable (active or inactive) cells and distinguishing them from damaged and membrane-compromised cells. This information is of major importance in studies of the function of microbial assemblages in natural environments, in order to assign bulk activities measured by various methods to the very active cells that are effectively responsible for the observations. To achieve this task for bacteria in freshwater and marine waters, we propose a nucleic acid double-staining assay based on analytical flow cytometry, which allows us to distinguish viable from damaged and membrane-compromised bacteria and to sort out noise and detritus. This method is derived from the work of S. Barbesti et al. (Cytometry 40:214-218, 2000) which was conducted on cultured bacteria. The principle of this approach is to use simultaneously a permeant (SYBR Green; Molecular Probes) and an impermeant (propidium iodide) probe and to take advantage of the energy transfer which occurs between them when both probes are staining nucleic acids. A full quenching of the permeant probe fluorescence by the impermeant probe will point to cells with a compromised membrane, a partial quenching will indicate cells with a slightly damaged membrane, and a lack of quenching will characterize intact membrane cells identified as viable. In the present study, this approach has been adapted to bacteria in freshwater and marine waters of the Mediterranean region. It is fast and easy to use and shows that a large fraction of bacteria with low DNA content can be composed of viable cells. Admittedly, limitations stem from the unknown behavior of unidentified species present in natural environments which may depart from the established permeability properties with respect to the fluorescing dyes.
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Affiliation(s)
- G Grégori
- Laboratoire d'Océanographie et de Biogéochimie, Université de la Méditerranée, CNRS UMR 6535, 13288 Marseille, France.
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Daugelavicius R, Bakiene E, Berzinskiene J, Bamford DH. Use of lipophilic anions for estimation of biomass and cell viability. Biotechnol Bioeng 2001; 71:208-16. [PMID: 11291030 DOI: 10.1002/1097-0290(2000)71:3<208::aid-bit1010>3.0.co;2-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A method is described to estimate the microbial biomass of a sample, to enumerate the cells, and to distinguish the portion of metabolically active cells in the population by measuring the binding of phenyldicarbaundecaborane (PCB(-)) to the cells. This method can also be used for the analysis of a complex population of microorganisms if the cells composing the sample are sensitive to different biocidal agents. In addition, the analysis of PCB(-) binding is useful for the enumeration of the phage-infected cells and phage particles.
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Affiliation(s)
- R Daugelavicius
- Department of Biochemistry and Biophysics, Vilnius University, Ciurlionio 21, LT-2009 Vilnius, Lithuania.
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Takenaka S, Iwaku M, Hoshino E. Artificial Pseudomonas aeruginosa biofilms and confocal laser scanning microscopic analysis. J Infect Chemother 2001; 7:87-93. [PMID: 11455498 DOI: 10.1007/s101560100014] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2000] [Accepted: 02/05/2001] [Indexed: 11/30/2022]
Abstract
Bacterial biofilms may be formed at various sites, including mucous membranes, teeth, and infectious lesions. To elucidate the structure and the function of biofilms, artificial biofilms of mucoid-type Pseudomonas aeruginosa organisms (strain PT1252) were made by centrifuging the organisms onto the surface of a coverglass and culturing further in broth media supplied continuously (45 ml/h). The biofilm structure at 4, 8, 12, and 24 h was visualized with fluorescent staining (SYTO9, propidium iodide [PI], and/or fluorescein isothiocyanate-concanavalin A [FITC-ConA]) by confocal laser scanning microscopy (CLSM). It was clearly demonstrated that the number of bacteria (10(4)--10(6)/ml) could be estimated by their fluorescence intensity. Sectional analysis of each biofilm layer (1-microm thickness) made it possible to demonstrate the three-dimensional development of biofilms, and revealed that the biofilms were 9 microm in height after 12 h. The live and dead organisms were differentiated by SYTO9 and PI, respectively, in situ in biofilms, and about 13% of the organisms were dead in 12-h-old biofilms. When 12-h-old biofilms were exposed to ciprofloxacin at minimum bactericidal concentration (6.26 microg/ml) for 90 min, all the organisms were killed, but some organisms (11 +/- 1.3%; n = 3) in 24-h-old biofilms with thicker and denser structure were still alive after exposure for 120 min. These results indicate that the CLSM analysis of artificial biofilms was useful for elucidating bacterial functions in biofilms, and may lead to a new quantitative system for estimating the bactericidal efficacy of antibacterial drugs in biofilms.
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Affiliation(s)
- S Takenaka
- Department of Oral Microbiology, Faculty of Dentistry, Niigata University, 5274 Gakkocho-dori 2-bancho, Niigata 951-8514, Japan
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Connell C, Rutter A, Hill B, Suller M, Lloyd D. Encystation of Acanthamoeba castellanii: Dye uptake for assessment by flow cytometry and confocal laser scanning microscopy. J Appl Microbiol 2001; 90:706-12. [PMID: 11348429 DOI: 10.1046/j.1365-2672.2001.01296.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS To develop rapid means of distinguishing between cysts and trophozoites of the opportunistic pathogen, Acanthamoeba castellanii, the causative agent of keratitis. METHODS AND RESULTS Fluorescence of Congo Red, Calcoflor White was specific for the endocyst wall; trophozoites did not become fluorescent. The anionic oxonol dye, DiBAC4(3), did not penetrate the cytoplasmic membrane after short-term (<5 min) exposure, whereas cysts are permeable and become fluorescent. Confocal scanning laser microscopy confirmed these properties and large populations of organisms were analysed by flow cytometry. CONCLUSION These data provide a rapid alternative to traditional haemocytometer or plate counts for discrimination of trophozoites from cysts. SIGNIFICANCE AND IMPACT OF THE STUDY Rapid and precise determination of the growth cycle of a dangerous ocular pathogen.
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Affiliation(s)
- C Connell
- Microbiology (BIOSI 1), Cardiff University, Wales, UK
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46
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Affiliation(s)
- S A Sincock
- Purdue Cytometry Laboratories, Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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48
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Plock A, Sokolowska-Köhler W, Presber W. Application of flow cytometry and microscopical methods to characterize the effect of herbal drugs on Leishmania Spp. Exp Parasitol 2001; 97:141-53. [PMID: 11312576 DOI: 10.1006/expr.2001.4598] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The World Health Organization has identified leishmania sis as a major public health problem, particularly in Africa, Asia, and Latin America. About 1.5 to 2 million people are affected annually by this parasitic infection. As there is no vaccine, there is still a strong need for sufficient drugs. In a preliminary screening, extracts of 50 different plants were evaluated for their possible leishmanicidal activity against the promastigote form of Leishmania mexicana amazonensis. Eighteen extracts showed at least 50% inhibition at 100 microg/ml. The ethanolic extract from Yucca filamentosa L. showed the strongest leishmanicidal activity (100% inhibition at 5 microg/ml). The bioactivity-guided fractionation of this extract led to the isolation of three main components (Yuccasaponins MC 1--3). In further experiments, the effect of Yuccasaponin MC 3 on the promastigote form of L. mexicana amazonensis was quantified and characterized using flow cytometry and specific fluorescent dyes [propidium iodide, Syto 9, and DiBAC(4)(3)]. The data revealed that the membrane of the promastigote is attacked. The effect of Yuccasaponin MC 3 on intracellular forms (amastigote) was also characterized; green fluorescent protein-transfected Leishmania major were used. By this method, an inhibition of intracellular growth of L. major was demonstrated. This paper shows that, together, flow cytometry and microscopy are quick, sensitive, and easily reproducible methods to describe the effects of drugs on parasites.
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Affiliation(s)
- A Plock
- Institute of Pharmacy, Humboldt University Berlin, Goethestr. 54, 13086 Berlin, Germany
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Favrin SJ, Jassim SA, Griffiths MW. Development and optimization of a novel immunomagnetic separation- bacteriophage assay for detection of Salmonella enterica serovar enteritidis in broth. Appl Environ Microbiol 2001; 67:217-24. [PMID: 11133448 PMCID: PMC92550 DOI: 10.1128/aem.67.1.217-224.2001] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2000] [Accepted: 10/13/2000] [Indexed: 11/20/2022] Open
Abstract
Salmonella is the second-leading cause of food-borne illness in most developed countries, causing diarrhea, cramps, vomiting, and often fever. Many rapid methods are available for detection of Salmonella in foods, but these methods are often insensitive or expensive or require a high degree of technical ability to perform. In this paper we describe development and characterization of a novel assay that utilizes the normal infection cycle of bacteriophage SJ2 for detection of Salmonella enterica serovar Enteritidis in broth. The assay consists of four main stages: (i) capture and concentration of target cells by using immunomagnetic separation (IMS); (ii) infection of the target bacterium with phage; (iii) amplification and recovery of progeny phage; and (iv) assay of progeny phage on the basis of their effect on a healthy population of host cells (signal-amplifying cells). The end point of the assay can be determined by using either fluorescence or optical density measurements. The detection limit of the assay in broth is less than 10(4) CFU/ml, and the assay can be performed in 4 to 5 h. The results of this study demonstrate that the IMS-bacteriophage assay is a rapid, simple, and sensitive technique for detection of Salmonella serovar Enteritidis in broth cultures which can be applied to preenriched food samples.
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Affiliation(s)
- S J Favrin
- Department of Food Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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50
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Enumeration of total and highly active bacteria. METHODS IN MICROBIOLOGY 2001. [DOI: 10.1016/s0580-9517(01)30043-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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