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Ruiz L, Ruas-Madiedo P, Gueimonde M, de los Reyes-Gavilán CG, Margolles A, Sánchez B. How do bifidobacteria counteract environmental challenges? Mechanisms involved and physiological consequences. GENES & NUTRITION 2011; 6:307-18. [PMID: 21484166 PMCID: PMC3145062 DOI: 10.1007/s12263-010-0207-5] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 12/26/2010] [Indexed: 01/04/2023]
Abstract
An effective response to stress is of paramount importance for probiotic bifidobacteria administered in foods, since it determines their performance as beneficial microorganisms. Firstly, bifidobacteria have to be resistant to the stress sources typical in manufacturing, including heating, exposure to low water activities, osmotic shock and presence of oxygen. Secondly, and once they are orally ingested, bifidobacteria have to overcome physiological barriers in order to arrive in the large intestine biologically active. These barriers are mainly the acid pH in the stomach and the presence of high bile salt concentrations in the small intestine. In addition, the large intestine is, in terms of microbial amounts, a densely populated environment in which there is an extreme variability in carbon source availability. For this reason, bifidobacteria harbours a wide molecular machinery allowing the degradation of a wide variety of otherwise non-digestible sugars. In this review, the molecular mechanisms allowing this bacterial group to favourably react to the presence of different stress sources are presented and discussed.
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Affiliation(s)
- Lorena Ruiz
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Asturias, Spain
| | - Patricia Ruas-Madiedo
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Asturias, Spain
| | - Miguel Gueimonde
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Asturias, Spain
| | - Clara G. de los Reyes-Gavilán
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Asturias, Spain
| | - Abelardo Margolles
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Asturias, Spain
| | - Borja Sánchez
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Asturias, Spain
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Hamon E, Horvatovich P, Izquierdo E, Bringel F, Marchioni E, Aoudé-Werner D, Ennahar S. Comparative proteomic analysis of Lactobacillus plantarum for the identification of key proteins in bile tolerance. BMC Microbiol 2011; 11:63. [PMID: 21447177 PMCID: PMC3073879 DOI: 10.1186/1471-2180-11-63] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Accepted: 03/29/2011] [Indexed: 01/01/2023] Open
Abstract
Background Lactic acid bacteria are commonly marketed as probiotics based on their putative or proven health-promoting effects. These effects are known to be strain specific but the underlying molecular mechanisms remain poorly understood. Therefore, unravelling the determinants behind probiotic features is of particular interest since it would help select strains that stand the best chance of success in clinical trials. Bile tolerance is one of the most crucial properties as it determines the ability of bacteria to survive in the small intestine, and consequently their capacity to play their functional role as probiotics. In this context, the objective of this study was to investigate the natural protein diversity within the Lactobacillus plantarum species with relation to bile tolerance, using comparative proteomics. Results Bile tolerance properties of nine L. plantarum strains were studied in vitro. Three of them presenting different bile tolerance levels were selected for comparative proteomic analysis: L. plantarum 299 V (resistant), L. plantarum LC 804 (intermediate) and L. plantarum LC 56 (sensitive). Qualitative and quantitative differences in proteomes were analyzed using two-dimensional electrophoresis (2-DE), tryptic digestion, liquid chromatography-mass spectrometry analysis and database search for protein identification. Among the proteins correlated with differences in the 2-DE patterns of the bacterial strains, 15 have previously been reported to be involved in bile tolerance processes. The effect of a bile exposure on these patterns was investigated, which led to the identification of six proteins that may be key in the bile salt response and adaptation in L. plantarum: two glutathione reductases involved in protection against oxidative injury caused by bile salts, a cyclopropane-fatty-acyl-phospholipid synthase implicated in maintenance of cell envelope integrity, a bile salt hydrolase, an ABC transporter and a F0F1-ATP synthase which participate in the active removal of bile-related stress factors. Conclusions These results showed that comparative proteomic analysis can help understand the differential bacterial properties of lactobacilli. In the field of probiotic studies, characteristic proteomic profiles can be identified for individual properties that may serve as bacterial biomarkers for the preliminary selection of strains with the best probiotic potential.
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Affiliation(s)
- Erwann Hamon
- Equipe de Chimie Analytique des Molécules Bio-Actives, IPHC-DSA, Université de Strasbourg, CNRS, 67400, Illkirch, France
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Technological and probiotic selection criteria of a bile-adapted Bifidobacterium animalis subsp. lactis strain. Int Dairy J 2010. [DOI: 10.1016/j.idairyj.2010.06.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Falentin H, Deutsch SM, Jan G, Loux V, Thierry A, Parayre S, Maillard MB, Dherbécourt J, Cousin FJ, Jardin J, Siguier P, Couloux A, Barbe V, Vacherie B, Wincker P, Gibrat JF, Gaillardin C, Lortal S. The complete genome of Propionibacterium freudenreichii CIRM-BIA1, a hardy actinobacterium with food and probiotic applications. PLoS One 2010; 5:e11748. [PMID: 20668525 PMCID: PMC2909200 DOI: 10.1371/journal.pone.0011748] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 06/29/2010] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Propionibacterium freudenreichii is essential as a ripening culture in Swiss-type cheeses and is also considered for its probiotic use. This species exhibits slow growth, low nutritional requirements, and hardiness in many habitats. It belongs to the taxonomic group of dairy propionibacteria, in contrast to the cutaneous species P. acnes. The genome of the type strain, P. freudenreichii subsp. shermanii CIRM-BIA1 (CIP 103027(T)), was sequenced with an 11-fold coverage. METHODOLOGY/PRINCIPAL FINDINGS The circular chromosome of 2.7 Mb of the CIRM-BIA1 strain has a GC-content of 67% and contains 22 different insertion sequences (3.5% of the genome in base pairs). Using a proteomic approach, 490 of the 2439 predicted proteins were confirmed. The annotation revealed the genetic basis for the hardiness of P. freudenreichii, as the bacterium possesses a complete enzymatic arsenal for de novo biosynthesis of aminoacids and vitamins (except panthotenate and biotin) as well as sequences involved in metabolism of various carbon sources, immunity against phages, duplicated chaperone genes and, interestingly, genes involved in the management of polyphosphate, glycogen and trehalose storage. The complete biosynthesis pathway for a bifidogenic compound is described, as well as a high number of surface proteins involved in interactions with the host and present in other probiotic bacteria. By comparative genomics, no pathogenicity factors found in P. acnes or in other pathogenic microbial species were identified in P. freudenreichii, which is consistent with the Generally Recognized As Safe and Qualified Presumption of Safety status of P. freudenreichii. Various pathways for formation of cheese flavor compounds were identified: the Wood-Werkman cycle for propionic acid formation, amino acid degradation pathways resulting in the formation of volatile branched chain fatty acids, and esterases involved in the formation of free fatty acids and esters. CONCLUSIONS/SIGNIFICANCE With the exception of its ability to degrade lactose, P. freudenreichii seems poorly adapted to dairy niches. This genome annotation opens up new prospects for the understanding of the P. freudenreichii probiotic activity.
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Affiliation(s)
- Hélène Falentin
- INRA, UMR 1253, Science et Technologie du Lait et de l'OEuf, Rennes, France.
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Waddington L, Cyr T, Hefford M, Hansen LT, Kalmokoff M. Understanding the acid tolerance response of bifidobacteria. J Appl Microbiol 2010; 108:1408-20. [DOI: 10.1111/j.1365-2672.2009.04540.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Gueimonde M, Garrigues C, van Sinderen D, de los Reyes-Gavilán CG, Margolles A. Bile-inducible efflux transporter from Bifidobacterium longum NCC2705, conferring bile resistance. Appl Environ Microbiol 2009; 75:3153-60. [PMID: 19304838 PMCID: PMC2681658 DOI: 10.1128/aem.00172-09] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 03/10/2009] [Indexed: 12/28/2022] Open
Abstract
Bifidobacteria are normal inhabitants of the human gut. Some strains of this genus are considered health promoting or probiotic, being included in numerous food products. In order to exert their health benefits, these bacteria must overcome biological barriers, including bile salts, to colonize and survive in specific parts of the intestinal tract. The role of multidrug resistance (MDR) transporters in bile resistance of probiotic bacteria and the effect of bile on probiotic gene expression are not fully understood. In the present study, the effect of subinhibitory concentrations of bile on the expression levels of predicted MDR genes from three different bifidobacterial strains, belonging to Bifidobacterium longum subsp. longum, Bifidobacterium breve, and Bifidobacterium animalis subsp. lactis, was tested. In this way, two putative MDR genes whose expression was induced by bile, BL0920 from B. longum and its homolog, Bbr0838, from B. breve, were identified. The expression of the BL0920 gene in Escherichia coli was shown to confer resistance to bile, likely to be mediated by active efflux from the cells. To the best of our knowledge, this represents the first identified bifidobacterial bile efflux pump whose expression is induced by bile.
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Affiliation(s)
- Miguel Gueimonde
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Villaviciosa, Asturias, Spain
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Ruiz L, Couté Y, Sánchez B, de los Reyes-Gavilán CG, Sanchez JC, Margolles A. The cell-envelope proteome of Bifidobacterium longum in an in vitro bile environment. Microbiology (Reading) 2009; 155:957-967. [DOI: 10.1099/mic.0.024273-0] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Host–bacteria interactions are often mediated via surface-associated proteins. The identification of these proteins is an important goal of bacterial proteomics. To address how bile can influence the cell-envelope proteome of Bifidobacterium longum biotype longum NCIMB 8809, we analysed its membrane protein fraction using stable isotope labelling of amino acids in cell culture (SILAC). We were able to identify 141 proteins in the membrane fraction, including a large percentage of the theoretical transporters of this species. Moreover, the envelope-associated soluble fraction was analysed using different subfractionation techniques and differential in-gel fluorescence electrophoresis (DIGE). This approach identified 128 different proteins. Some of them were well-known cell wall proteins, but others were highly conserved cytoplasmic proteins probably displaying a ‘moonlighting’ function. We were able to identify 11 proteins in the membrane fraction and 6 proteins in the envelope-associated soluble fraction whose concentration varied in the presence of bile. Bile promoted changes in the levels of proteins with important biological functions, such as some ribosomal proteins and enolase. Also, oligopeptide-binding proteins were accumulated on the cell surface, which was reflected in a different tripeptide transport rate in the cells grown with bile. The data reported here will provide the first cell-envelope proteome map for B. longum, and may contribute to understanding the bile tolerance of these bacteria.
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Affiliation(s)
- Lorena Ruiz
- Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (CSIC), Ctra Infiesto s/n, 33300, Villaviciosa, Asturias, Spain
| | - Yohann Couté
- Biomedical Proteomics Research Group, Department of Structural Biology and Bioinformatics, University of Geneva, 1 Rue Michel Servet, 1211 Geneva 14, Switzerland
| | - Borja Sánchez
- UMR 5248 CBMN, CNRS-Université Bordeaux 1-ENITAB, Laboratoire de Microbiologie et Biochimie Appliquée, 1 cours du Général de Gaulle, 33175 Gradignan CEDEX, France
| | - Clara G. de los Reyes-Gavilán
- Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (CSIC), Ctra Infiesto s/n, 33300, Villaviciosa, Asturias, Spain
| | - Jean-Charles Sanchez
- Biomedical Proteomics Research Group, Department of Structural Biology and Bioinformatics, University of Geneva, 1 Rue Michel Servet, 1211 Geneva 14, Switzerland
| | - Abelardo Margolles
- Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (CSIC), Ctra Infiesto s/n, 33300, Villaviciosa, Asturias, Spain
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Bile affects the synthesis of exopolysaccharides by Bifidobacterium animalis. Appl Environ Microbiol 2008; 75:1204-7. [PMID: 19088310 DOI: 10.1128/aem.00908-08] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
By using cryo-scanning electron microscopy and quantification with lectin-conjugated probes, we have detected the production of exopolysaccharides (EPS) in Bifidobacterium animalis subsp. lactis in the presence of bile. In addition, the expression of gtf01207, which codifies a putative priming glycosyltransferase involved in EPS synthesis, was induced by bile.
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Guglielmetti S, Ciranna A, Mora D, Parini C, Karp M. Construction, characterization and exemplificative application of bioluminescent Bifidobacterium longum biovar longum. Int J Food Microbiol 2008; 124:285-90. [DOI: 10.1016/j.ijfoodmicro.2008.03.033] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Revised: 03/25/2008] [Accepted: 03/25/2008] [Indexed: 11/30/2022]
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Sánchez B, Champomier-Vergès MC, Stuer-Lauridsen B, Ruas-Madiedo P, Anglade P, Baraige F, de los Reyes-Gavilán CG, Johansen E, Zagorec M, Margolles A. Adaptation and response of Bifidobacterium animalis subsp. lactis to bile: a proteomic and physiological approach. Appl Environ Microbiol 2007; 73:6757-67. [PMID: 17827318 PMCID: PMC2074956 DOI: 10.1128/aem.00637-07] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Bile salts are natural detergents that facilitate the digestion and absorption of the hydrophobic components of the diet. However, their amphiphilic nature makes them very inhibitory for bacteria and strongly influences bacterial survival in the gastrointestinal tract. Adaptation to and tolerance of bile stress is therefore crucial for the persistence of bacteria in the human colonic niche. Bifidobacterium animalis subsp. lactis, a probiotic bacterium with documented health benefits, is applied largely in fermented dairy products. In this study, the effect of bile salts on proteomes of B. animalis subsp. lactis IPLA 4549 and its bile-resistant derivative B. animalis subsp. lactis 4549dOx was analyzed, leading to the identification of proteins which may represent the targets of bile salt response and adaptation in B. animalis subsp. lactis. The comparison of the wild-type and the bile-resistant strain responses allowed us to hypothesize about the resistance mechanisms acquired by the derivative resistant strain and about the bile salt response in B. animalis subsp. lactis. In addition, significant differences in the levels of metabolic end products of the bifid shunt and in the redox status of the cells were also detected, which correlate with some differences observed between the proteomes. These results indicate that adaptation and response to bile in B. animalis subsp. lactis involve several physiological mechanisms that are jointly dedicated to reduce the deleterious impact of bile on the cell's physiology.
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Affiliation(s)
- Borja Sánchez
- Unité Flore Lactique et Environnement Carné (UR309), INRA, Domaine de Vilvert, F-78350 Jouy-en-Josas, France
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61
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Sánchez B, Champomier-Vergès MC, Collado MDC, Anglade P, Baraige F, Sanz Y, de los Reyes-Gavilán CG, Margolles A, Zagorec M. Low-pH adaptation and the acid tolerance response of Bifidobacterium longum biotype longum. Appl Environ Microbiol 2007; 73:6450-9. [PMID: 17720838 PMCID: PMC2075061 DOI: 10.1128/aem.00886-07] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Bifidobacteria are one of the main microbial inhabitants of the human colon. Usually administered in fermented dairy products as beneficial microorganisms, they have to overcome the acidic pH found in the stomach during the gastrointestinal transit to be able to colonize the lower parts of the intestine. The mechanisms underlying acid response and adaptation in Bifidobacterium longum biotype longum NCIMB 8809 and its acid-pH-resistant mutant B. longum biotype longum 8809dpH were studied. Comparison of protein maps, and protein identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis, allowed us to identify nine different proteins whose production largely changed in the mutant strain. Furthermore, the production of 47 proteins was modulated by pH in one or both strains. These included general stress response chaperones and proteins involved in transcription and translation as well as in carbohydrate and nitrogen metabolism, among others. Significant differences in the levels of metabolic end products and in the redox status of the cells were also detected between the wild-type strain and its acid-pH-resistant mutant in response to, or as a result of, adaptation to acid. Remarkably, the results of this work indicated that adaptation and response to low pH in B. longum biotype longum involve changes in the glycolytic flux and in the ability to regulate the internal pH. These changes were accompanied by a higher content of ammonium in the cytoplasm, likely coming from amino acid deamination, and a decrease of the bile salt hydrolase activity.
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Affiliation(s)
- Borja Sánchez
- Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Científicas (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Asturias, Spain
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Masco L, Crockaert C, Van Hoorde K, Swings J, Huys G. In Vitro Assessment of the Gastrointestinal Transit Tolerance of Taxonomic Reference Strains from Human Origin and Probiotic Product Isolates of Bifidobacterium. J Dairy Sci 2007; 90:3572-8. [PMID: 17638965 DOI: 10.3168/jds.2006-548] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Next to health promoting effects, the functional aspect of probiotic strains also involves their capacity to reach the colon as viable metabolically active cells. The present study aimed to assess the potential of 24 probiotic product isolates and 42 human reference strains of Bifidobacterium to survive gastrointestinal transit under in vitro conditions. The survival capacity of exponential and stationary phase cultures upon exposure to gastric and small intestinal juices was determined using a recently developed microplate-based assay in combination with the LIVE/DEAD BacLight Bacterial Viability kit. All 66 strains tested displayed a considerable loss in viability during exposure to an acidic pepsin containing solution (pH 2.0). Among the 10 taxa tested, cultures of B. animalis ssp. lactis appeared to be most capable to survive gastric transit. Although to a lesser extent, the presence of bile salts also affected the viability of most of the strains tested. Except for 3 strains, all 66 strains showed bile salt hydrolase activity using an agar-based assay. In contrast, the bifidobacterial strains used in this study appeared to possess a natural ability to survive the presence of pancreatin (pH 8.0). Although the effect was not significant, a slightly enhanced tolerance to gastrointestinal transit was observed when cells were in the stationary phase, especially when exposed to acid, compared with cells being in the exponential phase. Survival in the gastrointestinal tract appeared to be largely strain-dependent and hence implies that different strains will likely display a different behavior in functionality. The assay used in this study allows an initial assessment of strains for use as probiotic cultures prior to selecting potential candidate strains for further investigation in vivo.
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Affiliation(s)
- L Masco
- Laboratory of Microbiology, Ghent University, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium.
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Solheim M, Aakra A, Vebø H, Snipen L, Nes IF. Transcriptional responses of Enterococcus faecalis V583 to bovine bile and sodium dodecyl sulfate. Appl Environ Microbiol 2007; 73:5767-74. [PMID: 17660310 PMCID: PMC2074917 DOI: 10.1128/aem.00651-07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Resistance to bile is a prerequisite property of the gastrointestinal bacterial flora. Bile acids are powerful detergents, and resistance to sodium dodecyl sulfate (SDS) has therefore often been considered relevant to studies of bile resistance. We have studied the effects of bovine bile (BB) and SDS on Enterococcus faecalis V583 by traditional growth studies and microarrays. Transcriptional responses were studied by time course experiments. In the presence of BB (V583-BB) or SDS (V583-SDS), 308 and 209 genes were identified as differentially expressed at one or more time points, respectively. In V583 treated with both BB and SDS (V583-BB-SDS), 254 genes showed differential expression. Detergents exert their toxic effects primarily on the microbial membrane. The enrichment of differentially transcribed genes that encode proteins with membrane-associated functions and/or locations indicates a major impact of all three treatments on the integrity and functionality of the cell membrane. Two gene clusters involved in fatty acid biosynthesis were repressed in V583-BB and V583-BB-SDS and partly induced in V583-SDS. Furthermore, two EmrB/QacA family drug resistance transporters and a vacuolar-type ATPase were induced in V583-BB and V583-BB-SDS. None of the putative bile salt hydrolase homologs in V583 showed differential expression during the bile treatments. The transcriptional profile of V583-BB-SDS was qualitatively more similar to the response in V583-BB than to that in V583-SDS, suggesting that the presence of bile suppresses the effects of SDS in V583-BB-SDS. The overall results presented here indicate that different mechanisms are involved in detergent resistance in E. faecalis.
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Affiliation(s)
- Margrete Solheim
- Laboratory of Microbial Gene Technology and Food Microbiology, The Norwegian University of Life Sciences, PO Box 5003, N-1432 As, Norway.
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