Microbiology (2004), 150, 103–108 DOI 10.1099/mic.0.26437-0 Bovicin HJ50, a novel lantibiotic produced by Streptococcus bovis HJ50 Haijie Xiao,1 Xiuzhu Chen,1 Meiling Chen,1 Sha Tang,3 Xin Zhao1 and Liandong Huan1,2 Correspondence Liandong Huan [email protected] Received 23 April 2003 Revised 13 October 2003 Accepted 13 October 2003 1,2 Molecular Microbiology Research Center1 and State Key Laboratory of Microbial Resources2, Institute of Microbiology, Chinese Academy of Sciences, PO Box 2714, Beijing, PR China 3 Department of Microbiology, University of California, Riverside, CA 92521, USA A bacteriocin-producing strain was isolated from raw milk and named Streptococcus bovis HJ50. Like most bacteriocins produced by lactic acid bacteria, bovicin HJ50 showed a narrow range of inhibiting activity. It was sensitive to trypsin, subtilisin and proteinase K. Bovicin HJ50 was extracted by n-propanol and purified by SP Sepharose Fast Flow, followed by Phenyl Superose and Sephadex G-50. Treatment of Micrococcus flavus NCIB8166 with bovicin HJ50 revealed potassium efflux from inside the cell in a concentration-dependent manner. The molecular mass of bovicin HJ50 was determined to be 3428?3 Da. MS analysis of DTT-treated bovicin HJ50 suggested that bovicin HJ50 contains a disulfide bridge. The structural gene of bovicin HJ50 was cloned by nested PCR based on its N-terminal amino acid sequence. Sequence analysis showed that it encodes a 58 aa prepeptide consisting of an N-terminal leader sequence of 25 aa and a C-terminal propeptide domain of 33 aa. Bovicin HJ50 shows similarity to type AII lantibiotics. Chemical modification using an ethanethiol-containing reaction mixture showed that two Thr residues are modified. INTRODUCTION Bacteriocins are antimicrobial peptides, proteins or complex proteins produced by certain bacteria (Allison & Klaenhammer, 1999; Jack et al., 1995; McAuliffe et al., 2001). Many species of bacteria produce bacteriocins, but bacteriocins produced by lactic acid bacteria (LAB) are of particular interest because of the relationship between LAB and humans. Since nisin was found in 1928, over 70 kinds of bacteriocin produced by LAB have been found. Nisin, the best studied bacteriocin, has been approved as a food preservative in over 50 countries. During the last few decades a lot of research into bacteriocins produced by LAB has been carried out. Bacteriocins are one of the antimicrobial substances produced by LAB and it is thought that they play an important role in inhibiting other bacteria in the same environment. Bacteriocins have been categorized into four groups according to their chemical properties (Klaenhammer, 1993): group I, lantibiotics which contain unusual amino acid Abbreviations: LAB, lactic acid bacteria; MALDI-TOF, matrix-assisted laser desorption/ionization-time of flight. The GenBank accession numbers for the 16S rDNA sequence of S. bovis HJ50 and bovA reported in this paper are AY173079 and AY271354. 0002-6437 G 2004 SGM residues, such as lanthionine, 3-methyllanthionine, 2,3didehydroalanine and 2,3-didehydrobutyrine; group II, small, heat-stable peptides; group III, large, heat-labile proteins; group IV, complex proteins, composed of protein plus lipid or carbohydrate. Group IV bacteriocins are somewhat questionable because of inadequate data. Bacteriocins from groups I and II are the best studied. A great deal of research into bacteriocins and their uses has been carried out, including characterization of new bacteriocins, modification of bacteriocins by protein engineering (Chen et al., 1998; Rollema et al., 1995), construction of food-grade vectors (Takala & Saris, 2002), regulation and expression of heterologous proteins (de Ruyter et al., 1996), control of flavour and other characterisitcs of fermented food, and pharmaceutical and veterinary applications of bacteriocinproducing bacteria, etc. Originally, the potential use of bacteriocins as food preservatives stimulated research into bacteriocins produced by LAB which has led to a greater understanding of these important bacteria. Many bacteriocin-producing LAB have been isolated from raw milk; Lactococcus spp., Lactobacillus spp. and Leuconostoc spp. are the most abundant. Production strains for nisin, lacticin 481 and garviecin L1-5 (Villani et al., 2001) were isolated from milk. From raw milk provided by a dairy, we isolated a strain producing a novel bacteriocin. In this paper, the biochemical and genetic characterization of this bacteriocin is studied. Downloaded from www.sgmjournals.org by IP: 93.91.26.97 On: Tue, 07 Jul 2015 07:57:32 Printed in Great Britain 103 H. Xiao and others METHODS Bacterial strains and media. The bacteriocin-producing strain (Streptococcus bovis HJ50) was isolated from raw milk provided by the Qutou Dairy of Beijing and was grown anaerobically in M17 medium with 5 g glucose l21 at 37 uC. An indicator strain, Micrococcus flavus NCIB8166, was grown in S1 medium at 30 uC. Characterization of the bacteriocin-producing strain. S. bovis HJ50 was tested for growth temperature, growth at pH 9?6, hydrolysis of arginine and aesculin, production of catalase and amylase, Voges– Proskauer reaction, growth in 6?5 % NaCl and acid production from several carbohydrates. Total DNA was extracted according to Lewington et al. (1987). Two primers were used for 16S rDNA analysis: 27f (59-AGAGTTTGATCNTGGCTCAG-39) and 1541r (59-AAGGAGGTGATCCAGCC-39). PCR was performed under the following conditions: 94 uC for 5 min followed by 30 cycles of denaturation at 94 uC for 1 min, annealing at 52 uC for 1 min and polymerization at 72 uC for 3 min. The PCR product was ligated into pGEM-T vector (Promega) for DNA sequencing. Detection of bacteriocin activity and susceptibility to proteases. A culture of S. bovis HJ50 was centrifuged to remove the cells. The cell-free supernatant was adjusted to pH 7?0 for the detection of bacteriocin activity by the well-diffusion method. A neutral solution was also used to measure activity against other bacteria to determine the antimicrobial spectrum of bovicin HJ50. Susceptibility to proteases was examined according to Aktypis et al. (1998). A neutral solution of bovicin HJ50 was also treated with trypsin, subtilisin and proteinase K at 37 uC for 1 h. Extraction and purification of bovicin HJ50. Bovicin HJ50 was extracted with n-propanol according to Cheeseman & Berridge (1957). Briefly, a culture of S. bovis HJ50 was adjusted to pH 2 with HCl. After centrifugation, 0?1 vols n-propanol was added into the broth supernatant, then 300 g NaCl was added. The supernatant/npropanol solution was collected and the residual broth was extracted with 30 ml n-propanol per litre of broth for a second time. All of the n-propanol solution was collected and 2 vols cold acetone was added to obtain a precipitate of bovicin HJ50. The precipitate was dissolved in 0?05 M citric acid buffer (pH 4?2) to obtain a crude extract of bovicin HJ50. The crude extract was dialysed against 0?05 M citric acid buffer (pH 4?2) and applied to an SP Sepharose Fast Flow column previously equilibrated with the same buffer. Bovicin HJ50 was eluted with a 0–1 M NaCl gradient by using a fast performance liquid chromatography (FPLC) system. Active fractions were combined and dialysed against 0?05 M citric acid buffer (pH 4?2) containing 1?5 M NaCl. A Phenyl Superose column was used for hydrophobic interaction chromatography, eluted with a 1?5–0 M NaCl gradient. Active fractions were combined and lyophilized. Then the bacteriocin sample was applied to a Sephadex G-50 column for gel filtration. The active fractions were collected and lyophilized. Protein concentration was measured by the method of Bradford (1976). Determination of potassium efflux. Potassium efflux was deter- mined according to Chen & Montville (1995). Cells of M. flavus NCIB8166 were grown in S1 medium supplemented with 2?5 mmol KCl l21 at 30 uC. Cells were harvested at mid-exponential phase (OD600=0?6–0?7) for cell dry weight and potassium efflux determination. Cells were washed in 0?1 M MES buffer (pH 6?3) containing 0?2 % glucose and 0?6 mmol KCl l21 and resuspended in the same volume of MES buffer. Purified bovicin HJ50 was added to the cell suspension at different concentrations. A cell suspension with no bacteriocin added served as a blank control. One hour after treatment 104 with bovicin HJ50, the suspension was centrifuged at 12 000 r.p.m. for 10 min to remove the cells. The supernatant was applied to a plasma spectrum (Prodigy; Leeman Labs) for determination of potassium. MS analysis of bovicin HJ50. The molecular mass of purified bovicin HJ50 was determined by matrix-assisted laser desorption/ ionization-time of flight (MALDI-TOF) MS on a BIFLEX III TOFMS instrument. Bovicin HJ50 treated with 4 mmol DTT l21 for 15 min at 60 uC was also used for MS analysis. N-terminal sequence analysis of bovicin HJ50. The N-terminal sequence of purified bovicin HJ50 was determined on an Applied Biosystems 477A automatic sequence analyser by using the Edman degradation method. Cloning of the gene encoding bovicin HJ50. Three degenerate primers: P1, P2 and P3 (Table 1), designed according to the Nterminal sequence of bovicin HJ50, were used to clone the gene encoding bovicin HJ50. Cys was tentatively used to substitute the third position because of the homology between bovicin HJ50 and type AII lantibiotics. PCR was performed with 2 mM each primer mix, P1 or P2 with P3, under the following conditions: 94 uC for 5 min followed by 40 cycles of denaturation at 94 uC for 50 s, annealing at 49 uC for 50 s and polymerization at 72 uC for 20 s. A 44 bp PCR product was obtained for sequence analysis. The remaining part of the gene was cloned by nested PCR. Briefly, total DNA cut with a set of restriction endonucleases was ligated into the plasmid pBluescript II SK(+) cut with the same restriction enzymes. These ligation mixtures were used as PCR templates with gene-specific (P4 and P5) and vector-specific primers (T3 and SK). The PCR product was sequenced and primer P6 was designed based on the resulting DNA sequence. PCR for chromosome walking was performed under the following conditions: 30 cycles of denaturation at 94 uC for 1 min, annealing at 53 uC for 1 min and polymerization at 72 uC for 3 min. Chemical modification of bovicin HJ50. Chemical modification of bovicin HJ50 was performed according to Meyer et al. (1994). Bovicin HJ50 (8 mg) was dried under vacuum and resuspended in 50 ml of a modification mixture. The reaction mixture was incubated under nitrogen for 1 h at 50 uC followed by the addition of 2 ml acetic acid to stop the reaction. The reaction mixture was dried under vacuum and resuspended in water for MALDI-TOF MS analysis and peptide sequencing by Edman degradation. Table 1. Primers used for cloning of bovA Primer P1 P2 P3 P4 P5 P6 SK T3 Downloaded from www.sgmjournals.org by IP: 93.91.26.97 On: Tue, 07 Jul 2015 07:57:32 Sequence (5§–3§) GA(T/C)CGNGGNTGGAT(A/T/C)AA GA(T/C)AG(A/G)GGNTGGAT(A/T/C)AA AC(A/G)TTNGG(A/G)CA(A/G)TC(T/C)TT GGGTGGATTAAGACTTTAAC GACTTTAACAAAGATTGCCC TCTAACAGGTCTCTTGTAGC CCGCTCTAGAACTAGTGGAT AATTAACCCTCACTAAAGGG Microbiology 150 Novel lantibiotic produced by S. bovis RESULTS Extraction, purification and characterization of bovicin HJ50 Identification of the bovicin HJ50-producing strain Like nisin and acidocin B (ten Brink et al., 1994), bovicin HJ50 could be extracted with n-propanol because of its hydrophobic properties. Most bovicin HJ50 remained in solution in n-propanol. In comparison with ammonium sulfate precipitation, the yield from n-propanol extraction was high (data not shown). After extraction, bovicin HJ50 was purified by ion exchange with SP Sepharose Fast Flow, followed by hydrophobic reaction chromatography with Phenyl Superose and gel filtration on Sephadex G-50. The bacteriocin-producing strain was a Gram-positive, amylase-positive, catalase-negative coccus able to grow at 45 uC and at pH 9?6. However, it failed to grow at 10 uC and in broth containing 6?5 % NaCl. It gave a negative Voges– Proskauer reaction and produced no ammonia from the hydrolysis of arginine. The hydrolysis of aesculin was negative. It showed acid production from lactose, galactose and maltose, but not from inulin, mannitol, raffinose, ribose, salicin, sorbitol and trehalose. 16S rDNA analysis showed that the strain shares 99 % homology with S. bovis NCD02127. Thus, the strain was named S. bovis HJ50. Antimicrobial spectrum and susceptibility to proteases As shown in Table 2, bovicin HJ50 was active against Lactobacillus curvatus LTH1174, Bacillus subtilis AS1.1087, Bacillus megaterium AS1.941, M. flavus NCIB8166, Leuconostoc dextranicum 181 and Leuconostoc mesenteroides AS1.2, but it showed no activity against Listeria monocytogenes. Like most other bacteriocins produced by LAB, bovicin HJ50 could only inhibit some strains of Gram-positive bacteria. Bovicin HJ50 could be inactivated by trypsin, subtilisin and proteinase K (data not shown). Bovicin HJ50 increased the potassium permeability of M. flavus NCIB8166 in a concentration-dependent fashion (data not shown) and 20 AU bovicin HJ50 ml21 gave maximum potassium efflux. MS (Fig. 1b) showed that the molecular mass of bovicin HJ50 was 3428?3 Da, which was very close to the result of Tricine/SDS-PAGE (data not shown). The molecular mass of bovicin HJ50 reduced with DTT (Fig. 1a) was about 2?4 Da higher than that of untreated bovicin HJ50, indicating that bovicin HJ50 probably contains a disulfide bridge. Edman degradation analysis revealed the N-terminal amino acid sequence of bovicin HJ50 to be Ala-Asp-Arg-Gly-TrpIle-Lys-X-Leu-X-Lys-Asp-X-Pro-Asn-Val-Ile-Ser-Ser-Ile. X at positions 8, 10 and 13 indicated blank cycles in which no Table 2. Antimicrobial spectrum of bovicin HJ50 Strain Bacillus cereus Bacillus coagulans AS1.949 Bacillus megaterium AS1.941 Bacillus subtilis AS1.1087 Escherichia coli Enterococcus faecalis Lactobacillus acidophilus Lactobacillus brevis Lactobacillus buchneri AS1.40 Lactobacillus curvatus LTH1174 Lactobacillus plantarum Leuconostoc mesenteroides AS1.2 Leuconostoc dextranicum 181 Listeria monocytogenes Micrococcus flavus NCIB8166 Pseudomonas aeruginosa 10105 Shigella flexneri 51285 Staphylococcus aureus 26071 *–, No inhibition. http://mic.sgmjournals.org No. of strains tested Zone of inhibition (mm)* 3 1 1 1 3 3 2 3 1 1 4 1 1 2 1 1 1 1 – – 14 12 – – – – – 13 – 10 13 – 21 – – – Fig. 1. MALDI-TOF mass spectrum of bovicin HJ50 treated with (a) and without (b) DTT. Downloaded from www.sgmjournals.org by IP: 93.91.26.97 On: Tue, 07 Jul 2015 07:57:32 105 H. Xiao and others Fig. 2. Nucleotide sequence of bovA. The putative ”10 region of the bovA promoter and the ribosome-binding site (RBS) region are underlined. The vertical arrow indicates the cleavage site between the leader peptide and bovicin HJ50 propeptide. The inverted repeat sequence downstream of bovA indicates the putative transcriptional terminator sequence. amino acid derivative was detected. Comparison of this sequence with sequences in the SWISS-PROT database showed that bovicin HJ50 is a novel peptide. Analysis of the gene encoding bovicin HJ50 bovA, the structural gene of bovicin HJ50, was obtained by PCR using degenerate primers based on the N-terminal amino acid sequence, followed by nested PCR. As shown in Fig. 2, DNA sequencing confirmed the results of N-terminal sequencing of bovicin HJ50. The translation initiation site was arbitrarily assigned to the first of two ATG codons. bovA encodes a 58 aa prepeptide with a leader sequence of 25 aa. The leader peptide is hydrophilic, strongly charged and predicted to contain an a-helical conformation. It shows similarity with sequences of leader peptides of type AII lantibiotics (Fig. 3), including streptococcin A-FF22 (SAFF22), lacticin 481, variacin (Pridmore et al., 1996), mutacin II (Woodruff et al., 1998) and salivaricin A (Ross et al., 1993). It contains a GG (double-glycine) motif immediately preceding the cleavage site, and a conserved EL sequence (Sablon et al., 2000; Chen et al., 2001). The leader peptide of bovicin HJ50 contains a TVS motif instead of the conserved EVT/EVS sequences. The propeptide is a 33 aa peptide with a calculated mass of 3467?96 Da and a pI of 8?2. DNA sequencing revealed that the eighth and tenth amino acids of the bovicin HJ50 propeptide are both Thr and the thirteenth is Cys. The bovicin HJ50 propeptide also shows similarity with sequences of type AII lantibiotics (Fig. 3), especially salivaricin A. Propeptides of bovicin HJ50 and salivaricin A share 29?4 % identity. Although bovicin HJ50 shows similarity with the sequences of type AII lantibiotics, the identity is low. The bovicin HJ50 propeptide is composed of 33 aa, whereas other AII lantibiotics range from 22 to 27 aa. The C-terminal sequence of bovicin HJ50 differs from that of type AII lantibiotics. Furthermore, the bovicin HJ50 propeptide contains four Cys residues, while other type AII lantibiotics contain only three. A putative promoter is underlined in Fig. 2. The promoter contains a TG doublet 1 bp upstream of the 210 region (TATTAT). Approximately half of the lactococcal promoter sequences studied possess this characteristic (de Vos & Simons, 1994). In addition, downstream of bovA, a 20 bp palindrome may serve as a r-independent transcription terminator. Chemical modification of bovicin HJ50 Chemical modification of lantibiotics has been used to determine the number of dehydrated amino acid residues in pep5, gallidermin (Meyer et al., 1994), mutacin I and mutacin III (Qi et al., 2000). To confirm that bovicin HJ50 contains modified amino acids, we performed an ethanethiol modification of bovicin HJ50. Edman degradation analysis of ethanethiol-modified bovicin HJ50 revealed the Fig. 3. Alignment of the leader peptides and propeptides of bovicin HJ50 and lantibiotics of type AII. Identical amino acid residues are indicated with black boxes. Positions where at least three amino acid residues are identical are indicated with shaded boxes. Consensus residues are shown below. The arrow indicates the cleavage site. 106 Downloaded from www.sgmjournals.org by IP: 93.91.26.97 On: Tue, 07 Jul 2015 07:57:32 Microbiology 150 Novel lantibiotic produced by S. bovis eighth and tenth amino acids were both b-methyl-Sethylcysteine. However, no derivative was detected for the thirteenth residue. Two major peaks were generated after ethanethiol modification of bovicin HJ50 (Fig. 4). The two peaks showed molecular masses of 3490 and 3552 Da, respectively, which could be accounted for by bovicin HJ50 plus one or two molecules of ethanethiol. Our results revealed that Thr8 and Thr10 are modified, but probably none of the other Thr or Ser residues are modified. DISCUSSION In this study, we isolated a bacteriocin-producing strain from raw milk. Bacterial characters and phylogenetic analysis indicated that the bovicin HJ50-producing strain was S. bovis, a normal inhabitant of the cow rumen. Like most other bacteriocins produced by LAB, bovicin HJ50 is a small cationic peptide and could cause permeabilization of the target cell membrane. Bovicin HJ50 showed a narrow range of inhibitory activity. involved in the formation of unusual amino acids. In lantibiotic sequence analysis, Edman cleavage of a residue forming lanthionine or 3-methyllanthionine would result in a blank cycle; however, the subsequent reactions would continue. Sequencing by Edman degradation is often blocked by a dehydro residue (Sahl et al., 1995). Therefore, Thr8 and Thr10 may be involved in the formation of 3methyllanthionine with two Cys residues. Another two Cys residues form a disulfide bridge. Thus, bovicin HJ50 has two thioether bridges and a disulfide bridge. This would give a peptide with a calculated molecular mass of 3429?96 Da. This value was in a good agreement with the molecular mass of 3428?3 Da obtained by MS of bovicin HJ50. MS analysis of bovicin HJ50 reduced with DTT indicated that bovicin HJ50 contains a disulfide bridge. However, when assayed in the presence of DTT, the titre of bovicin HJ50 against M. flavus NCIB8166 was neither decreased nor increased (data not shown). Lantibiotics containing a disulfide bridge are an anomaly in the bacteriocin world. To our knowledge, only sublancin 168 produced by Bacillus subtilis 168 (Paik et al., 1998) and plwa produced by Lactobacillus plantarum LMG 2379 (Holo et al., 2001) contain disulfide bridges. Antibiotics are routinely fed to beef cattle in the USA to alter ruminal fermentation. As antimicrobial substances, bacteriocins produced by ruminal bacteria may have similar effects on ruminal fermentation. Several studies have been performed to investigate whether bacteriocins produced by S. bovis in the rumen have such an effect (Lee et al., 2002, Mantovani et al., 2002, Whitford et al., 2001). Bovicin HC5 produced by S. bovis HC5 has a wide inhibitory spectrum and could inhibit a variety of freshly isolated S. bovis strains without causing adaptation. It is thought that it could be used to control the ruminal ecological environment. Further work is needed to investigate if bovicin HJ50 has a similar effect. ACKNOWLEDGEMENTS The evidence presented here shows that bovicin HJ50 is a lantibiotic. In lantibiotics, Ser, Thr and Cys are usually This work was supported by a grant (no. 39970391) from the National Natural Science Foundation of China. At present most of the bacteriocins produced by Streptococcus strains are lantibiotics, such as salivaricin A, SA-FF22, mutacin I (Qi et al., 2001), mutacin II and mutacin III (Qi et al., 1999), etc., while bovicin 255 and mutacin IV are regarded as non-lantibiotics. Bovicin HJ50 is a lantibiotic with the unusual characteristic that it contains a disulfide bridge. Fig. 4. MALDI-TOF mass spectrum ethanethiol-modified bovicin HJ50. http://mic.sgmjournals.org Downloaded from www.sgmjournals.org by IP: 93.91.26.97 On: Tue, 07 Jul 2015 07:57:32 of 107 H. Xiao and others REFERENCES derivatization procedures allow a fast access to complete Edman degradation. Anal Biochem 223, 185–190. Aktypis, A., Kalantzopoulos, G., Huis in’t Veld, J. H. J. & ten Brink, B. (1998). Purification and characterization of thermophilin T, a novel Paik, S. H., Chakicherla, A. & Hansen, J. N. (1998). Identification bacteriocin produced by Streptococcus thermophilus ACA-DC 0040. J Appl Microbiol 84, 568–576. Allison, G. E. & Klaenhammer, T. R. (1999). Genetics of bacteriocins and characterization of the structural and transporter genes for, and the chemical and biological properties of, sublancin 168, a novel lantibiotic produced by Bacillus subtilis 168. J Biol Chem 273, 23134–23142. produced by lactic acid bacteria and their use in novel industrial applications. In Manual of Industrial Microbiology and Biotechnology, 2nd edn, pp. 789–808. Edited by A. L. Demain & J. E. Davies. Washington, DC: American Society for Microbiology. Variacin, a new lanthionine-containing bacteriocin produced by Micrococcus varians: comparison to lacticin 481 of Lactococcus lactis. Appl Environ Microbiol 62, 1799–1802. Bradford, M. M. (1976). A rapid and sensitive method for the quanti- Qi, F., Chen, P. & Caufield, P. W. (1999). Purification of mutacin III tation of microgram quantities of protein utilizing the principle of protein–dye binding. Anal Biochem 72, 248–254. Cheeseman, G. C. & Berridge, N. J. (1957). An improved method from group III Streptococcus mutans UA787 and genetic analyses of mutacin III biosynthesis genes. Appl Environ Microbiol 65, 3880–3887. for preparing nisin. Biochem J 65, 603–608. Qi, F., Chen, P. & Caufield, P. W. (2000). Purification and Chen, Y. & Montville, T. J. (1995). Efflux of ions and ATP depletion biochemical characterization of mutacin I from the group I strain of Streptococcus mutans, CH43, and genetic analysis of mutacin I biosynthesis genes. Appl Environ Microbiol 66, 3221–3229. induced by pediocin PA-1 are concomitant with cell death in Listeria monocytogenes Scott A. J Appl Bacteriol 79, 684–690. Chen, P., Novak, J., Kirk, M., Barnes, S., Qi, F. & Caufield, P. W. (1998). Structure-activity study of the lantibiotic mutacin II from Streptococcus mutans T8 by a gene replacement strategy. Appl Environ Microbiol 64, 2335–2340. Chen, P., Qi, F., Novak, J., Krull, R. E. & Caufield, P. W. (2001). Effect Pridmore, D., Rekhif, N., Pittet, A.-C., Suri, B. & Mollet, B. (1996). Qi, F., Chen, P. & Caufield, P. W. (2001). The group I strain of Streptococcus mutans, UA140, produces both the lantibiotic mutacin I and a nonlantibiotic bacteriocin, mutacin IV. Appl Environ Microbiol 67, 15–21. Rollema, H. S., Kuipers, O. P., Both, P., de Vos, W. M. & Siezen, R. J. (1995). Improvement of solubility and stability of the antimicrobial of amino acid substitutions in conserved residues in the leader peptide on biosynthesis of the lantibiotic mutacin II. FEMS Microbiol Lett 195, 139–144. peptide nisin by protein engineering. Appl Environ Microbiol 61, 2873–2878. de Ruyter, P. G., Kuipers, O. P. & de Vos, W. M. (1996). Controlled Ross, K. F., Ronson, C. W. & Tagg, J. R. (1993). Isolation and gene expression systems for Lactococcus lactis with the food-grade inducer nisin. Appl Environ Microbiol 62, 3662–3667. de Vos, W. M. & Simons, G. F. M. (1994). Gene cloning and characterization of the lantibiotic salivaricin A and its structural gene salA from Streptococcus salivarius 20P3. Appl Environ Microbiol 59, 2014–2021. expression systems in Lactococci. In Genetics and Biotechnology of Lactic Acid Bacteria, pp. 52–105. Edited by M. J. Gasson & W. M. de Vos. Glasgow: Blackie. Sablon, E., Contreras, B. & Vandamme, E. (2000). Antimicrobial Holo, H., Jeknic, Z., Daeschel, M., Stevanovic, S. & Nes, I. F. (2001). Sahl, H.-G., Jack, R. W. & Bierbaum, G. (1995). Biosynthesis and peptides of lactic acid bacteria: mode of action, genetics and biosynthesis. Adv Biochem Eng Biotechnol 68, 21–60. Plantaricin W from Lactobacillus plantarum belongs to a new family of two-peptide lantibiotics. Microbiology 147, 643–651. biological activities of lantibiotics with unique post-translational modifications. Eur J Biochem 230, 827–853. Jack, R. W., Tagg, J. R. & Ray, B. (1995). Bacteriocins of Gram- Takala, T. M. & Saris, P. E. (2002). A food-grade cloning vector for positive bacteria. Microbiol Rev 59, 171–200. Klaenhammer, T. R. (1993). Genetics of bacteriocins produced by lactic acid bacteria. FEMS Microbiol Rev 12, 39–85. Lee, S. S., Hsu, J.-T., Mantovani, H. C. & Russell, J. B. (2002). The effect of bovicin HC5, a bacteriocin from Streptococcus bovis HC5, on ruminal methane production in vitro. FEMS Microbiol Lett 217, 51–55. Lewington, J., Greenaway, S. D. & Spillan, B. J. (1987). Rapid small scale preparation of bacterial genomic DNA, suitable for cloning and hybridization analysis. Lett Appl Microbiol 5, 51–53. Mantovani, H. C., Hu, H., Worobo, R. W. & Russell, J. B. (2002). Bovicin HC5, a bacteriocin from Streptococcus bovis HC5. Microbiology 148, 3347–3352. lactic acid bacteria based on the nisin immunity gene nisI. Appl Microbiol Biotechnol 59, 467–471. ten Brink, B., Minekus, M., van der Vossen, J. M. B. M., Leer, R. J. & Huis In’t Veld, J. H. J. (1994). Antimicrobial activity of lactobacilli: preliminary characterization and optimization of production of acidocin B, a novel bacteriocin produced by Lactobacillus acidophilus M46. J Appl Bacteriol 77, 140–148. Villani, F., Aponte, M., Blaiotta, G., Mauriello, G., Pepe, O. & Moschetti, G. (2001). Detection and characterization of a bacter- iocin, garviecin L1-5, produced by Lactococcus garvieae isolated from raw cow’s milk. J Appl Microbiol 90, 430–439. Whitford, M. F., McPherson, M. A., Forster, R. J. & Teather, R. M. (2001). Identification of bacteriocin-like inhibitors from rumen McAuliffe, O., Ross, R. P. & Hill, C. (2001). Lantibiotics: structure, Streptococcus spp. and isolation and characterization of bovicin 255. Appl Environ Microbiol 67, 569–574. biosynthesis and mode of action. FEMS Microbiol Rev 25, 285–308. Woodruff, W. A., Novak, J. & Caufield, P. W. (1998). Sequence Meyer, H. E., Heber, M., Eisermann, B., Korte, H., Metzger, J. W. & Jung, G. (1994). Sequence analysis of lantibiotics: chemical analysis of mutA and mutM genes involved in the biosynthesis of the lantibiotic mutacin II in Streptococcus mutans. Gene 206, 37–43. 108 Downloaded from www.sgmjournals.org by IP: 93.91.26.97 On: Tue, 07 Jul 2015 07:57:32 Microbiology 150
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