Expression of mptC of Listeria monocytogenes induces sensitivity to class IIa bacteriocins in Lactococcus lactis

Manilduth Ramnath1,2,{dagger}, Safia Arous2,{dagger}, Anne Gravesen3, John W. Hastings1 and Yann Héchard2

1 Department of Biochemistry, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa
2 Laboratory of Fundamental and Applied Microbiology, LCEE UMR CNRS 6008, University of Poitiers, 40, avenue du Recteur Pineau, 86022 Poitiers Cedex, France
3 The Royal Veterinary and Agricultural University, Department of Dairy and Food Science, Centre for Advanced Food Studies, LMC, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark

Correspondence
Yann Héchard
yann.hechard{at}univ-poitiers.fr


   ABSTRACT
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
 
Sensitivity to class IIa bacteriocins from lactic acid bacteria was recently associated with the mannose phosphotransferase system (PTS) permease, , in Listeria monocytogenes. To assess the involvement of this protein complex in class IIa bacteriocin activity, the mptACD operon, encoding , was heterologously expressed in an insensitive species, namely Lactococcus lactis, using the NICE double plasmid system. Upon induction of the cloned operon, the recombinant Lc. lactis became sensitive to leucocin A. Pediocin PA-1 and enterocin A also showed inhibitory activity against Lc. lactis cultures expressing mptACD. Furthermore, the role of the three genes of the mptACD operon was investigated. Derivative plasmids containing various combinations of these three genes were made from the parental mptACD plasmid by divergent PCR. The results showed that expression of mptC alone is sufficient to confer sensitivity to class IIa bacteriocins in Lc. lactis.


Abbreviations: PTS, phosphotransferase system

{dagger}These authors contributed equally to this work.


   INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
 
Class IIa bacteriocins are antibacterial peptides produced by lactic acid bacteria that inhibit the food-borne pathogen Listeria monocytogenes (Ennahar et al., 2000b). These peptides have been shown to exert their activity by dissipation of the proton motive force of susceptible cells, possibly via membrane pore formation (Chikindas et al., 1993; Héchard & Sahl, 2002; Montville & Chen, 1998). Several mechanisms of interaction with the target cell have been proposed, including electrostatic binding to the membrane and/or specific binding to a membrane-associated component (Abee, 1995; Héchard & Sahl, 2002; Montville & Chen, 1998). Protease treatment of membrane vesicles, derived from sensitive cells, resulted in an increased resistance to pediocin PA-1 (Chikindas et al., 1993). This was the first indication of a proteinaceous membrane component that may interact with the bacteriocin. The requirement of a chiral interaction for leucocin A activity further strengthens the hypothesis that a specific interaction between a bacteriocin and a membrane compound in the target strain is required for inducing sensitivity (Yan et al., 2000). The subunit IIAB of a mannose permease of the phosphotransferase system (PTS) was found to be missing in a spontaneous mutant of Ls. monocytogenes with resistance to leucocin A, a class IIa bacteriocin (Ramnath et al., 2000). The same observation was made for a number of spontaneous mutants of Ls. monocytogenes showing high-level resistance to class IIa bacteriocins (Gravesen et al., 2002). This IIAB is part of the permease encoded by the mptACD operon (Dalet et al., 2001). Genetic inactivation of the mptACD operon resulted in resistance to mesentericin Y105 in Ls. monocytogenes and Enterococcus faecalis (Dalet et al., 2001; HeHéchard et al., 2001). Thus has been proposed as a requirement for inhibition of the target cell by class IIa bacteriocins.

To further evaluate the role of in bacterial sensitivity to class IIa bacteriocins, we heterologously expressed the mptACD operon of Ls. monocytogenes in an insensitive Lactococcus lactis strain. Genetic constructs were made to determine the effect of expressing individual genes and combinations of genes in the operon. Our results show that the expression of mptC induces sensitivity to various class IIa bacteriocins in Lc. lactis.


   METHODS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
 
Bacterial strains and plasmids.
Bacterial strains and plasmids are described in Table 1. Lc. lactis MG 1363 and derivatives were grown at 30 °C in M17 (Difco) broth or agar, supplemented with 0·5 % glucose (w/v). Escherichia coli XL-1 Blue (Stratagene) used for molecular cloning was grown at 37 °C in Luria–Bertani broth with aeration. Ls. monocytogenes was grown at 37 °C in Brain Heart Infusion broth (Difco). When appropriate, the media were supplemented with the required antibiotics to the following final concentrations: chloramphenicol (10 µg ml–1); erythromycin (5 µg ml–1); ampicillin (100 µg ml–1). The inducible NICE system was used to heterologously express genes in Lc. lactis. The system consists of two compatible plasmids, pNZ9530 carrying the nisRK regulatory genes and pNZ8020, the expression vector, carrying the gene of interest under the control of the nisA promoter that is induced by addition of nisin A (de Ruyter et al., 1996).


View this table:
[in this window]
[in a new window]
 
Table 1. Bacterial strains and plasmids

 
DNA manipulations and plasmid constructions.
General molecular biology methods were performed according to Sambrook et al. (2000). Ls. monocytogenes EGDe (Glaser et al., 2001) chromosomal DNA was isolated as described by Mengaud et al. (1991). The mptACD operon, without its promoter but including the ribosome-binding site, was amplified by PCR using the proof-reading polymerase Pfx (Promega) with the following specific primers: MptAM, 5'-TATATTAGGAGGGAAAAAGATGGTAGG-3', and MptDV, 5'-ATTATACCGTATTCGTTTATCTGTGTC-3'. The PCR product was cloned into pGEM Easy-T (Promega) after addition of 3' A overhangs resulting in pMRI. An SphI–SacI fragment, containing the mptACD operon, was excised from pMRI and cloned into pNZ8020 yielding plasmid pNM-ACD. This plasmid was subsequently used to create pNM derivative plasmids, containing one or two genes of the mptACD operon. Divergent PCR reactions were performed with different sets of primers (Table 2 and Fig. 1) using the PfuTurbo proof reading polymerase (Stratagene), as follows: 94 °C for 2 min, followed by 30 cycles of 94 °C for 30 s, 55 °C for 30 s, 72 °C for 8 min, and a final extension at 72 °C for 10 min. The PCR products were self-ligated, giving rise to the pNM derivative plasmids, named after the gene(s) which remain present (Table 1). The pNM-C plasmid, in which both mptA and mptD were deleted, was obtained in a second step using the plasmid pNM-CD as the template. The constructions were verified by PCR and/or sequencing over the ligation site.


View this table:
[in this window]
[in a new window]
 
Table 2. Primer sets used to obtain the derivative plasmids from pNM-ACD by divergent PCR reactions

 


View larger version (11K):
[in this window]
[in a new window]
 
Fig. 1. Genetic map of the mptACD operon. Primers used to obtain the derivative plasmids from pNM-ACD by divergent PCR reactions are indicated by small arrows.

 
Lc. lactis MG 1363 was transformed with a pNM derivative plasmid by electroporation and transformants were subsequently electroporated with pNZ9530 (Table 1). A control strain, Lc. lactis MG-Con containing pNZ8020 and pNZ9530, was made in the same manner.

RT-PCR experiments.
Lc. lactis was grown to an OD630 of 0·2. Nisin A was added to the relevant cultures and grown for another 2 h to allow mptACD expression. The cells were harvested (8000 g, 10 min at 4 °C), resuspended in a lysis buffer (5 mg lysozyme ml–1, 100 g glucose l–1, 5 mM Tris-EDTA, pH 8) and incubated for 1 h at 37 °C. Total RNA was isolated with the RNAwiz kit (Ambion), according to the manufacturer's instructions, and treated with 4 units RNase-free DNase (Invitrogen) for 1 h at 37 °C. The quality of the RNA samples was assessed by 1 % formaldehyde agarose gel electrophoresis and the quantity was estimated by spectrophotometry. The expression of each gene from the mptACD operon in the various constructions was assessed by RT-PCR or quantitative RT-PCR (qRT-PCR). Reverse transcription, leading to cDNA synthesis, was performed using 2 µg total RNA, with random hexamers (15 ng ml–1) and the Superscript II RNase H kit (Invitrogen), according to the manufacturer's instructions. PCR reactions using specific primers were performed from cDNA to check that each gene of the mptACD operon had been transcribed. qPCR was performed with the TaqMan Universal PCR Master kit (Applied Biosystems) to quantify expression of the mptA operon upon nisin A induction, using specific primers (5'-CAGGACTTAATTTGCCAATGTTG-3' and 5'-CGCGAACACCTTCTTGAGCT-3') and probe (5'-Fam-AGCGCACACGAAATCGCAGCAA-Tamra-3'). The PCR reactions were performed and analysed on an ABI Prism 7700 sequence detector (Applied Biosystems) under the following conditions: 50 °C for 2 min, 95 °C for 10 min, followed by 40 cycles at 95 °C for 10 s and 60 °C for 1 min. The control templates corresponded to different dilutions of genomic DNA. All the reactions were performed in triplicate. The Ct value was defined as the cycle number at which a significant increase in amplification product occurs. For each sample, a mean Ct was calculated from triplicate reactions. The Ct value is inversely correlated to the cDNA quantity. The relative expression was calculated as 2{Delta}Ct, according to the manufacturer's instructions.

Bacteriocin preparation.
Nisin A was purchased as a 2·5 % (w/w) powder (Sigma) and reconstituted in water. Leucocin A was synthesized as described previously (Ramnath et al., 2000) and resuspended in 50 % acetonitrile to a final concentration of 2 mg ml–1. Pediocin PA-1 (Henderson et al., 1992) and enterocin A (Aymerich et al., 1996) were produced by Pediococcus acidilactici NRRL B5627 and Enterococcus faecium 336, respectively, and purified as described by Guyonnet et al. (2000). All bacteriocin stocks were stored at –20 °C until used.

Sensitivity assays.
The sensitivity assays were performed in microtitre plates where an overnight culture of Lc. lactis was added as a 1 % inoculum and growth was monitored at OD630. When an OD630 of 0·05 was reached, nisin A was added to a final concentration of 2·5 ng ml–1 and the cultures were grown for a further 1·5 h before the addition of bacteriocin extracts or gramicidin S (Sigma).


   RESULTS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
 
Nisin-induced heterologous expression of mptACD in Lc. lactis MG–ACD
Expression of the mptACD operon in Lc. lactis MG-ACD was induced by addition of 2·5 ng nisin A ml–1. This concentration is similar to levels used previously for induction of the NICE system in Lc. lactis MG1363 and is about 50 times lower than the MIC (de Ruyter et al., 1996; Eichenbaum et al., 1998; Kleerebezem et al., 1997). Expression of mptACD in nisin-induced Lc. lactis MG-ACD was confirmed by qRT-PCR. Ct values of 10·6 and 19·1 were calculated for the nisin-induced and uninduced cultures, respectively, representing a 372-fold increase in expression following nisin induction.

mptACD expression leads to Lc. lactis sensitivity
Fig. 2. shows the effect of the addition of leucocin A to nisin-induced and uninduced cultures of Lc. lactis MG-ACD as well as MG-Con. Growth of the induced MG-ACD cultures was arrested immediately following addition of leucocin in the range of 20 µg ml–1 to 156 ng ml–1 (Fig. 2a). In contrast, growth of the control strain MG-Con was unaffected by the added concentrations of nisin A and leucocin A (Fig. 2b). An additional experiment with Lc. lactis MG-Con showed that growth was not influenced by a concentration of leucocin A as high as 400 µg ml–1.



View larger version (16K):
[in this window]
[in a new window]
 
Fig. 2. Growth of Lc. lactis MG-ACD and Lc. lactis MG-Con. Dashed lines represent cultures induced with 2·5 ng nisin A ml–1 and solid lines correspond to uninduced cultures. The solid and dashed arrows indicate the point of nisin A and leucocin A addition, respectively. Leucocin A was added to final concentrations of 20 µg ml–1 (filled circles), 5 µg ml–1 (open squares), 1·25 µg ml–1 (open diamonds), 156 ng ml–1 (crosses) and 0 ng ml–1 (filled squares). Error bars represent standard deviations from triplicate samples of the same experiment.

 
A reduction in growth of the MG-ACD strain was observed upon induction with nisin A (Fig. 2a). However, this was not seen with the MG-Con strain (Fig. 2b), indicating that the reduction was likely to be due to the expression of heterologous proteins.

The effect of two other class IIa bacteriocins on nisin-induced Lc. lactis MG-ACD cultures was compared to leucocin treatment (Fig. 3). Addition of pediocin PA-1 or enterocin A resulted in a complete inhibition of growth.



View larger version (15K):
[in this window]
[in a new window]
 
Fig. 3. Effect of pediocin PA-1, leucocin A and enterocin A on Lc. lactis MG-ACD. Dashed lines represent cultures induced with 2·5 ng nisin A ml–1 and solid lines correspond to uninduced cultures. The solid and dashed arrows indicate the point of nisin A and class IIa bacteriocin addition, respectively. Approximately 2000 activity units of each bacteriocin was used as follows: leucocin A (circles), pediocin PA-1 (triangles), enterocin A (diamonds) and no class IIa bacteriocin (squares). Error bars represent standard deviations from triplicate samples of the same experiment.

 
The IIC subunit is responsible for Lc. lactis sensitivity
To test the role of the individual genes, we subsequently constructed strains carrying different combinations of the three mpt genes under control of the NICE system (Table 1). The expression of all three mpt genes was analysed by RT-PCR from nisin-induced cultures of each of the five strains: MG-CD, MG-AD, MG-AC, MG-D and MG-C. The results confirmed that the cloned genes were expressed.

The sensitivity of the nisin-induced strains to leucocin was determined (Fig. 4). In the presence of nisin A, all five strains showed a reduction in growth that was similar to Lc. lactis MG-ACD. The growth of Lc. lactis MG-CD, MG-AC and MG-C was rapidly inhibited by leucocin A to the same extent as the parental MG-ACD strain. On the contrary, the addition of leucocin A had no effect on the growth of both Lc. lactis MG-AD and Lc. lactis MG-D. Thus, mptC was the only gene present in all the sensitive strains, but not in the insensitive ones.



View larger version (27K):
[in this window]
[in a new window]
 
Fig. 4. Growth of the Lc. lactis strains MG-CD, MG-AD, MG-AC, MG-D and MG-C derived from Lc. lactis MG-ACD. Dashed lines represent cultures induced with 2·5 ng nisin A ml–1 and solid lines correspond to uninduced cultures. The solid and dashed arrows indicate the point of nisin A and leucocin A addition, respectively. Leucocin A was added to a final concentration of 20 µg ml–1 (circles). A control without leucocin A was also made (squares). Error bars represent standard deviations from triplicate samples of the same experiment.

 
The five strains were also exposed to pediocin PA-1 and enterocin A. As shown with leucocin, Lc. lactis MG-CD, MG-AC and MG-C were sensitive to both these bacteriocins, while strains MG-AD and MG-D were insensitive.

No difference in sensitivity was observed between uninduced and induced cultures to gramicidin S (no growth above 5 µg ml–1). This molecule acts non-specifically on the cytoplasmic membrane (Prenner et al., 1999), indicating that the sensitivity to the class IIa bacteriocins was not due to a membrane perturbation by the induced proteins.


   DISCUSSION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
 
Lc. lactis is known to be insensitive to class IIa bacteriocins (Eijsink et al., 1998; Guyonnet et al., 2000) and, in our study, Lc. lactis MG-Con was unaffected by a leucocin A concentration of 400 µg ml–1. Growth of the nisin-induced Lc. lactis MG-ACD was insignificant at 156 ng leucocin ml–1, which is similar to concentrations required for inhibition of Ls. monocytogenes (Gravesen et al., 2002; Vadyvaloo et al., 2002). Thus, the sensitivity to leucocin A increased at least 2500-fold when expression of mptACD was induced in Lc. lactis. Lc. lactis MG-ACD was also sensitive to two other class IIa bacteriocins tested, namely, pediocin PA-1 and enterocin A (Fig. 3). This observation substantiates previous suggestions of a common mode of action for the class IIa bacteriocins against Ls. monocytogenes based on cross-resistance to these compounds (Ennahar et al., 2000a; Rasch & Knöchel, 1998) and also agrees with the general high-level resistance mechanism proposed for class IIa bacteriocins (Gravesen et al., 2002).

We subsequently analysed the role of the three subunits of the mptACD operon in class IIa sensitivity. The results showed that expression of mptC alone is sufficient to confer sensitivity to class IIa bacteriocins in Lc. lactis. A BLAST search showed that MptC has very high identity (88 %) to the Enterococcus faecalis mannose IIC subunit, which belongs to the mannose permease associated to class IIa bacteriocin sensitivity of this organism (Héchard et al., 2001). This high level of homology was expected in proteins that may be similarly involved in the class IIa mode of action. However, the region required for sensitivity may not be extensive as the search also showed that MptC has 59 % identity to the mannose IIC subunit (PtnC) of the class IIa-insensitive Lc. lactis.

The IIC subunit of a mannose permease has been shown to be specifically involved in the transfer of bacteriophage {lambda} DNA across the inner membrane in Escherichia coli (Esquinas-Rychen & Erni, 2001).

The involvement of the IIC subunit in the sensitivity to class IIa bacteriocins was unexpected because a partial mptD deletion experiment had previously suggested that the MptD subunit was specifically involved in the sensitivity of Ls. monocytogenes (Dalet et al., 2001). However, we subsequently observed that MptA was not expressed in the mptD deletion mutant, suggesting that the entire operon is switched off in this mutant (Gravesen et al., 2002). This observation may possibly be a regulatory consequence of defective permease activity, as it is known that PTS permease activity affects its own expression (Deutscher et al., 2002). In the present work, mptACD was under the control of the inducible nis promoter to avoid possible feedback regulation of the permease and to tightly control the expression.

In summary, the results of this study show that expression of mptC renders Lc. lactis sensitive to IIa bacteriocins, and indicate that these bacteriocins could possibly exert their antimicrobial activity through interaction with the MptC subunit in the cytoplasmic membrane.


   ACKNOWLEDGEMENTS
 
S. A. was supported by a fellowship from the Région Poitou-Charentes. M. R. was partly supported by Egide. The authors are grateful for the grants from National Research Foundation of South Africa and Centre National de la Recherche Scientifique (Franco–South Africa agreement) and from the French Embassy.


   REFERENCES
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
 
Abee, T. (1995). Pore-forming bacteriocins of gram-positive bacteria and self-protection mechanisms of producer organisms. FEMS Microbiol Lett 129, 1–10.[CrossRef][Medline]

Aymerich, T., Holo, H., Havarstein, L. S., Hugas, M., Garriga, M. & Nes, I. F. (1996). Biochemical and genetic characterization of enterocin A from Enterococcus faecium, a new antilisterial bacteriocin in the pediocin family of bacteriocins. Appl Environ Microbiol 62, 1676–1682.[Abstract]

Chikindas, M. L., Garcia-Garcera, M. J., Driessen, A. J., Ledeboer, A. M., Nissen-Meyer, J., Nes, I. F., Abee, T., Konings, W. N. & Venema, G. (1993). Pediocin PA-1, a bacteriocin from Pediococcus acidilactici PAC1.0, forms hydrophilic pores in the cytoplasmic membrane of target cells. Appl Environ Microbiol 59, 3577–3584.[Abstract]

Dalet, K., Cenatiempo, Y., Cossart, P. & Héchard, Y. (2001). A sigma(54)-dependent PTS permease of the mannose family is responsible for sensitivity of Listeria monocytogenes to mesentericin Y105. Microbiology 147, 3263–3269.[Medline]

de Ruyter, P. G., Kuipers, O. P. & de Vos, W. M. (1996). Controlled gene expression systems for Lactococcus lactis with the food-grade inducer nisin. Appl Environ Microbiol 62, 3662–3667.[Abstract/Free Full Text]

Deutscher, J., Galinier, A. & Martin-Verstraete, I. (2002). Carbohydrate uptake and metabolism. In Bacillus subtilis and its Closest Relatives: from Genes to Cells. Edited by A. L. Sonenshein, J. A. Hoch & R. Losick. Washington, DC: American Society for Microbiology.

Eichenbaum, Z., Federle, M. J., Marra, D., de Vos, W. M., Kuipers, O. P., Kleerebezem, M. & Scott, J. R. (1998). Use of the lactococcal nisA promoter to regulate gene expression in gram-positive bacteria: comparison of induction level and promoter strength. Appl Environ Microbiol 64, 2763–2769.[Abstract/Free Full Text]

Eijsink, V. G., Skeie, M., Middelhoven, P. H., Brurberg, M. B. & Nes, I. F. (1998). Comparative studies of class IIa bacteriocins of lactic acid bacteria. Appl Environ Microbiol 64, 3275–3281.[Abstract/Free Full Text]

Ennahar, S., Deschamps, N. & Richard, J. (2000a). Natural variation in susceptibility of Listeria strains to class IIa bacteriocins. Curr Microbiol 41, 1–4.[CrossRef][Medline]

Ennahar, S., Sashihara, T., Sonomoto, K. & Ishizaki, A. (2000b). Class IIa bacteriocins: biosynthesis, structure and activity. FEMS Microbiol Rev 24, 85–106.[CrossRef][Medline]

Esquinas-Rychen, M. & Erni, B. (2001). Facilitation of bacteriophage lambda DNA injection by inner membrane proteins of the bacterial phosphoenol-pyruvate : carbohydrate phosphotransferase system (PTS). J Mol Microbiol Biotechnol 3, 361–370.[Medline]

Glaser, P., Frangeul, L., Buchrieser, C. & 52 other authors (2001). Comparative genomics of Listeria species. Science 294, 849–852.[Abstract/Free Full Text]

Gravesen, A., Ramnath, M., Rechinger, K. B., Andersen, N., Jansch, L., Héchard, Y., Hastings, J. W. & Knöchel, S. (2002). High-level resistance to class IIa bacteriocins is associated with one general mechanism in Listeria monocytogenes. Microbiology 148, 2361–2369.[Medline]

Guyonnet, D., Fremaux, C., Cenatiempo, Y. & Berjeaud, J. M. (2000). Method for rapid purification of class IIa bacteriocins and comparison of their activities. Appl Environ Microbiol 66, 1744–1748.[Abstract/Free Full Text]

Héchard, Y. & Sahl, H. G. (2002). Mode of action of modified and unmodified bacteriocins from Gram-positive bacteria. Biochimie 84, 545–557.[CrossRef][Medline]

Héchard, Y., Pelletier, C., Cenatiempo, Y. & Frère, J. (2001). Analysis of {sigma}54-dependent genes in Enterococcus faecalis: a mannose PTS permease (EIIMan) is involved in sensitivity to a bacteriocin, mesentericin Y105. Microbiology 147, 1575–1580.[Medline]

Henderson, J. T., Chopko, A. L. & van Wassenaar, P. D. (1992). Purification and primary structure of pediocin PA-1 produced by Pediococcus acidilactici PAC-1.0. Arch Biochem Biophys 295, 5–12.[Medline]

Kleerebezem, M., Beerthuyzen, M. M., Vaughan, E. E., de Vos, W. M. & Kuipers, O. P. (1997). Controlled gene expression systems for lactic acid bacteria: transferable nisin-inducible expression cassettes for Lactococcus, Leuconostoc, and Lactobacillus spp. Appl Environ Microbiol 63, 4581–4584.[Abstract]

Mengaud, J., Geoffroy, C. & Cossart, P. (1991). Identification of a new operon involved in Listeria monocytogenes virulence: its first gene encodes a protein homologous to bacterial metalloproteases. Infect Immun 59, 1043–1049.[Medline]

Montville, T. J. & Chen, Y. (1998). Mechanistic action of pediocin and nisin: recent progress and unresolved questions. Appl Microbiol Biotechnol 50, 511–519.[CrossRef][Medline]

Prenner, E. J., Lewis, R. N. A. H. & McElhaney, R. N. (1999). The interaction of the antimicrobial peptide gramicidin S with lipid bilayer model and biological membranes. Biochim Biophys Acta 1462, 201–221.[Medline]

Ramnath, M., Beukes, M., Tamura, K. & Hastings, J. W. (2000). Absence of a putative mannose-specific phosphotransferase system enzyme IIAB component in a leucocin A-resistant strain of Listeria monocytogenes, as shown by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Appl Environ Microbiol 66, 3098–3101.[Abstract/Free Full Text]

Rasch, M. & Knöchel, S. (1998). Variations in tolerance of Listeria monocytogenes to nisin, pediocin PA-1 and bavaricin A. Lett Appl Microbiol 27, 275–278.[CrossRef][Medline]

Sambrook, J. & Russell, D. (2000). Molecular Cloning: a Laboratory Manual, 3rd edn. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory.

Vadyvaloo, V., Hastings, J. W., van der Merwe, M. J. & Rautenbach, M. (2002). Membranes of class IIa bacteriocin-resistant Listeria monocytogenes cells contain increased levels of desaturated and short-acyl-chain phosphatidylglycerols. Appl Environ Microbiol 68, 5223–5230.[Abstract/Free Full Text]

Yan, L. Z., Gibbs, A. C., Stiles, M. E., Wishart, D. S. & Vederas, J. C. (2000). Analogues of bacteriocins: antimicrobial specificity and interactions of leucocin A with its enantiomer, carnobacteriocin B2, and truncated derivatives. J Med Chem 43, 4579–4581.[CrossRef][Medline]

Received 23 December 2003; revised 9 April 2004; accepted 28 April 2004.



This Article
Abstract
Full Text (PDF)
Alert me when this article is cited
Alert me if a correction is posted
Citation Map
Services
Email this article to a friend
Similar articles in this journal
Similar articles in PubMed
Alert me to new issues of the journal
Download to citation manager
Google Scholar
Articles by Ramnath, M.
Articles by Héchard, Y.
Articles citing this Article
PubMed
PubMed Citation
Articles by Ramnath, M.
Articles by Héchard, Y.
Agricola
Articles by Ramnath, M.
Articles by Héchard, Y.


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
INT J SYST EVOL MICROBIOL MICROBIOLOGY J GEN VIROL
J MED MICROBIOL ALL SGM JOURNALS
Copyright © 2004 Society for General Microbiology.