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PubMed1982

Purification and certain properties of a bacteriocin from Streptococcus mutans.

An inhibition factor from Streptococcus mutans strain C3603 (serotype c) was purified and isolated, and its properties indicated that it was a bacteriocin. Bacteriocin C3603 is a basic protein with a pI value of 10 and a molecular weight of 4,800. The activity of this bacteriocin was not affected by pH over a range of 1.0 to 12.0 or by storage at 100 degrees C for 10 min at pH 2.0 to 7.0 or storage at 121 degrees C for 15 min at pH 4.0. Pronase; papain, phospholipase C, trypsin, and alpha-amylase had no effect on the activity of the bacteriocin, whereas alpha-chymotrypsin and pancreatin were partially active against it. Bacteriocin activity was greater against certain S. mutans strains of serotypes b, c, e, and f than against certain S. mutans strains of serotypes a, d, and g. Bacteriocin C3603 was also effective against selected strains of S. sanguis, S. salivarius, S. bovis, S. faecium, S. lactis, Lactobacillus casei, L. plantarum, L. fermentum, Bifidobacterium bifidum, Bifidobacterium longum, Propionibacterium acnes, and Bacteroides melaninogenicus, but it was not effective against certain strains of Escherichia coli, Klebsiella pneumoniae, Corynebacterium parvum, and Candida albicans. The inhibition of S. mutans strains BHT and PS-14 by bacteriocin C3603 was found to be due to the bacteriocidal activity of the bacteriocin. When water or a diet containing bacteriocin C3603 was consumed by gnotobiotic and specific pathogen-free rats infected with S. mutans PS-14, the caries score was found to be significantly reduced.

Animals↗
PubMed1996

Characterization of the locus responsible for the bacteriocin production in Lactobacillus plantarum C11.

Lactobacillus plantarum C11 secretes a small cationic peptide, plantaricin A, that serves as induction signal for bacteriocin production as well as transcription of plnABCD. The plnABCD operon encodes the plantaricin A precursor (PlnA) itself and determinants (PlnBCD) for a signal transducing pathway. By Northern (RNA) and sequencing analyses, four new plantaricin A-induced operons were identified. All were highly activated in concert with plnABCD upon bacteriocin induction. Two of these operons (termed plnEFI and plnJKLR) each encompass a gene pair (plnEF and plnJK, respectively) encoding two small cationic bacteriocin-like peptides with double-glycine-type leaders. The open reading frames (ORFs) encoding the bacteriocin-like peptides are followed by ORFs (plnI and -L, respectively) encoding cationic hydrophobic proteins resembling bacteriocin immunity proteins. On the third operon (termed plnMNOP), a similar bacteriocin-like ORF (plnN) and a putative immunity ORF (either plnM or -P) were identified as well. These findings suggest that two bacteriocins of two-peptide type (mature PlnEF and PlnJK) and a bacteriocin of one-peptide type (mature PlnN) could be responsible for the observed bacteriocin activity. The last operon (termed plnGHSTUV) contains two ORFs (plnGH) apparently encoding an ABC transporter and its accessory protein, respectively, known to be involved in processing and export of peptides with precursor double-glycine-type leaders. Promoter structure was established. A conserved regulatory-like box encompassing two direct repeats was identified in the promoter regions of all five plantaricin A-induced operons. These repeats may serve as regulatory elements for gene expression.

Amino Acid Sequence↗
PubMed1998

Enterocins L50A and L50B, two novel bacteriocins from Enterococcus faecium L50, are related to staphylococcal hemolysins.

Enterocin L50 (EntL50), initially referred to as pediocin L50 (L. M. Cintas, J. M. Rodríguez, M. F. Fernández, K. Sletten, I. F. Nes, P. E. Hernández, and H. Holo, Appl. Environ. Microbiol. 61:2643-2648, 1995), is a plasmid-encoded broad-spectrum bacteriocin produced by Enterococcus faecium L50. It has previously been purified from the culture supernatant and partly sequenced by Edman degradation. In the present work, the nucleotide sequence of the EntL50 locus was determined, and several putative open reading frames (ORFs) were identified. Unexpectedly, two ORFs were found to encode EntL50-like peptides. These peptides, termed enterocin L50A (EntL50A) and enterocin L50B (EntL50B), have 72% sequence identity and consist of 44 and 43 amino acids, respectively. Interestingly, a comparison of the deduced sequences of EntL50A and EntL50B with the corresponding sequences obtained by Edman degradation shows that these bacteriocins, in contrast to other peptide bacteriocins, are secreted without an N-terminal leader sequence or signal peptide. Expression in vivo and in vitro transcription/translation experiments demonstrated that entL50A and entL50B are the only genes required to obtain antimicrobial activity, strongly indicating that their bacteriocin products are not posttranslationally modified. Both bacteriocins possess antimicrobial activity on their own, with EntL50A being the most active. In addition, when the two bacteriocins were combined, a considerable synergism was observed, especially with some indicator strains. Even though the enterocins in some respects are similar to class II bacteriocins, several conserved features common to class II bacteriocins are absent from the EntL50 system. The enterocins have more in common with members of a small group of cytolytic peptides secreted by certain staphylococci. We therefore propose that the enterocins L50A and L50B and the staphylococcal cytolysins together constitute a new family of peptide toxins, unrelated to class II bacteriocins, which possess bactericidal and/or hemolytic activity.

Amino Acid Sequence↗
PubMed1977

Bacteriocin typing of streptococcal isolates from endocarditis.

A typing system based on bacteriocin production and sensitivity for Streptococcus sanguis strains was devised. Bacteriocin producer strains were grown (37degrees C) anaerobically on brain heart infusion-yeast extract agar for 18 h. Bacteriocin indicator strains were suspended to molten brain heart infusion-yeast extract agar and then overlayed onto the producer strain. After an additional 18 to 24 h of incubation, zones of bacteriocin inhibition were recorded. After establishment of the typing system, eight Streptococcus strains from bacterial endocarditis patients were characterized by the typing system. Four patient strains had identical bacteriocin reduction patterns but could be differentiated by differences in their bacteriocin sensitivity. Two isolates from the same patient had identical production and sensitivity patterns. By including both bacteriocin production and bacteriocin sensitivity, all seven epidemiologically unrelated isolates could be differentiated. On the basis of these results, there does not appear to be a correlation between bacteriocin production and infectivity, but the usefulness of the application of a typing system to a clinical situation is demonstrated.

Anaerobiosis↗
PubMed2004

Purification of antilisterial bacteriocins.

In recent years, numerous contamination outbreaks, involving various pathogens (i.e., Listeria and Salmonella), have increased concern over food preservation. Research efforts have focused on the discovery of new molecules targeting such foodborne pathogens and therefore able to inhibit and or kill them. Lactic acid bacteria (LAB) extensively used in fermented foods for thousands of years not only improve their flavor and texture but also inhibit pathogenic and spoilage microorganisms. LAB inhibitory activity is primarily owing to pH decrease and competition for substrates. Antagonistic activity of LAB also depends on secreted antimicrobial compounds with a poor selectivity, such as metabolic compounds (i.e., hydrogen peroxide, acetoin, and others) or more specific ones like bacteriocins. The latter are proteinaceous compounds, ribosomally synthesized and subsequently secreted by Gram-positive as well as Gram-negative bacteria. Their antimicrobial activity is generally restricted to strains phylogenetically related to the producers.A classification of bacteriocins produced by LAB was first proposed by Klaenhammer in 1993 and was modified by Nes et al. in 1996; class I and class II bacteriocins are the most abundant and thoroughly studied. Bacteriocins from both classes exhibit antilisterial activity. Class I bacteriocins, namely, lantibiotics, have been widely studied, and among them, nisin is used in many countries as a preservative in food products. These bacteriocins are characterized by the presence, in their primary structure, of post-translationally modified amino acid residues (i.e., lanthionine and methylanthionine) that are formed. Class II bacteriocins, containing three subclasses, consist of small peptides that do not bear any modified amino acid residue. The most studied subclass corresponds to class IIa, also termed anti-Listeria bacteriocins. These peptides share strong structural homologies in their N-terminal domain, with the presence of one disulfide bond and a net positive charge. Their C-terminal domain is more variable but appears quite hydrophobic. Moreover, some of these bacteriocins, namely, sakacin G, pediocin PA-1, enterocin A, coagulin, and divercin V41, are characterized by the presence of a second disulfide bond in the C-terminal region.

Amino Acid Sequence↗
PubMed1985

A comparative study of three bacteriocins of Bacteroides fragilis.

Three different bacteriocins produced by strains of Bacteroides fragilis were compared in terms of their production kinetics, physico-chemical nature, and action on macromolecular synthesis in a common indicator strain. Bacteriocin 78/438 was produced during the logarithmic growth phase, was thermolabile and stable between pH 5 and 9. It was susceptible to trypsin and pepsin, and affected DNA, RNA and protein syntheses in susceptible cells. Bacteriocin A49 was produced during the stationary growth phase, was thermolabile and stable between pH 7 and 9. This bacteriocin was also susceptible to trypsin and pepsin, but only RNA synthesis was affected in the indicator strain. Bacteriocin A55 differed markedly from both 78/438 and A49, and was found to be predominantly cell-bound, resistant to inactivation by high temperatures and stable over a wide pH range of 2 to 12. It was susceptible to trypsin but resistant to pepsin. A55 had a delayed effect on macromolecular synthesis with DNA synthesis being inhibited after 60 min. With all three bacteriocins, killing of the indicator strain followed single hit kinetics with the interaction of bacteriocin and target cell occurring in two stages. Killing by bacteriocin A55 was much slower than the other two and this may be related to its effect on macromolecular synthesis. The killing action of all three bacteriocins was dependent on the growth phase of the susceptible cells.

2,4-Dinitrophenol↗
PubMedDate not supplied

Bacterioides fragilis: production and sensitivity to bacteriocins.

Bacteriocin production and sensitivity to bacteriocins have been successfully applied as an epidemiological tool in several species of bacteria. However, little work has been carried out on the bacteriocins produced by Bacteroides fragilis, which is the most frequently isolated anaerobe species from clinical specimens. Thirty two clinical isolates of B. fragilis grown anaerobically on a 0.22 microm membrane filter spotted on an agar plate, were tested for bacteriocin production and used in a screen for bacteriocin sensitivity. Sensitivity to at least one bacteriocin was found in 94% of the strains, 62.5% were sensitive to two bacteriocins, whereas 34.4% were sensitive to three or more and finally one strain was found sensitive to 17 bacteriocins. Of the strains studied, 94% inhibited at least one strain, 66% inhibited two strains, and 30% inhibited at least three strains or more. Finally, one strain was extremely active by inhibiting the growth of 17 strains. Bacteriocin types are characterised by geographic variation, and their epidemiological investigation by a simple method could be promoted.

Journal Article↗
PubMed1996

Bacteriocin Typing of Burkholderia (Pseudomonas) solanacearum Race 1 of the French West Indies and Correlation with Genomic Variation of the Pathogen.

Burkholderia solanacearum race 1 isolates indigenous to the French West Indies were characterized by bacteriocin typing and two genomic fingerprinting methods: pulsed-field gel electrophoresis of genomic DNA digested by rare-cutting restriction endonucleases (RC-PFGE) and PCR with primers corresponding to repetitive extragenic palindromic (REP), enterobacterial repetitive intergenic consensus (ERIC), and BOX elements (collectively known as rep-PCR). The survey comprised 24 reference strains and 65 isolates obtained from a field trial in Guadeloupe in 1993. Comparison of the data identified RC-PFGE as the most discriminatory method, delineating 17 pulsed-field gel profile types. rep-PCR and bacteriocin typing identified nine rep-PCR profile types and nine bacteriocin groups. Independent determination of similarity coefficients and clustering of RC-PFGE and rep-PCR data identified six groups common to both sets of data that correlated to biovar and bacteriocin groups. Further study of bacteriocin production in planta gave results consistent with in vitro bacteriocin typing. It was observed that spontaneous bacteriocin-resistant mutants exhibited a cross-resistance to other bacteriocins as identified by the typing scheme and that such mutants possessed a selective advantage for growth over isogenic nonmutants in the presence of a bacteriocin. The results are significant in the search for biological control of disease by nonpathogenic mutants of the wild-type organism.

Journal Article↗
PubMed2006

Determination of bacteriocin activity with bioassays carried out on solid and liquid substrates: assessing the factor "indicator microorganism".

BACKGROUND: Successful application of growth inhibition techniques for quantitative determination of bacteriocins relies on the sensitivity of the applied indicator microorganism to the bacteriocin to which is exposed. However, information on indicator microorganisms' performance and comparisons in bacteriocin determination with bioassays is almost non-existing in the literature. The aim of the present work was to evaluate the parameter "indicator microorganism" in bioassays carried out on solid -agar diffusion assay- and liquid -turbidometric assay- substrates, applied in the quantification of the most studied bacteriocin nisin. RESULTS: The performance of characterized microorganisms of known sources, belonging to the genera of Lactobacillus, Pediococcus, Micrococcus and Leuconostoc, has been assessed in this work in the assays of plate agar diffusion and turbidometry. Dose responses and sensitivities were examined and compared over a range of assay variables in standard bacteriocin solutions, fermentation broth filtrates and processed food samples. Measurements on inhibition zones produced on agar plates were made by means of digital image analysis. The data produced were analyzed statistically using the ANOVA technique and pairwise comparisons tests. Sensitivity limits and linearity of responses to bacteriocin varied significantly among different test-microorganisms in both applied methods, the lower sensitivity limits depending on both the test-microorganism and the applied method. In both methods, however, only two of the nine tested microorganisms (Lactobacillus curvatus ATCC 51436 and Pediococcus acidilactici ATCC 25740) were sensitive to very low concentrations of the bacteriocin and produced a linear-type of response in all kinds of samples used in this work. In all cases, very low bacteriocin concentrations, e.g. 1 IU/ml nisin, were more accurately determined in the turbidometric assay. CONCLUSION: The present work shows that in growth inhibition techniques used in bacteriocin quantification, the choice of the indicator microorganism is critical. Evaluation of sensitivity levels and type of produced responses showed that they can vary widely among different test-microorganisms and different applied methods, indicating that not all microorganisms can be used successfully as indicators and that measurements of growth inhibition in liquid media produce more reliable results.

Journal Article↗
PubMed2001

Characterization of bacteriocin N15 produced by Enterococcus faecium N15 and cloning of the related genes.

Enterococcus faecium N15 was isolated from nuka (Japanese rice-bran paste), which is utilized as starter in the fermenting of vegetables, and was found to produce a bacteriocin that exhibited a broad spectrum of activity, including activity against Listeria monocytogenes and Bacillus circulans JCM2504. The bacteriocin was sensitive to proteases (alpha-chymotrypsin, proteinase K, trypsin, and pepsin) and alpha-amylase, but it was resistant to lipase. The bacteriocin was resistant to heat treatment at 100 degrees C for 2 h, but its activity was completely lost after autoclaving at 121 degrees C for 15 min. It was active over a wide pH range from 2.0 to 10.0. The bacteriocin showed bactericidal activity against Lactobacillus sake JCM1157 at a concentration of 40 AU/ml. Its molecular weight was estimated by SDS-PAGE to be about 3-5 kDa. PCR primers were designed based on the conserved amino acid sequences of class IIa bacteriocins. A 3-kb DNA fragment was amplified and three open reading frames (ORFs) were found. The first encodes a probable immunity protein of 103 amino acid residues and shows complete homology with the putative immunity protein of E. faecium DPC1146. The second and third ORFs respectively encode a probable transposase gene and an inducing factor. The upstream region of the immunity gene, in which the bacteriocin structural gene is located, was amplified. A homology search revealed that the bacteriocin produced by E. faecium N15 exhibits complete identity to enterocin A, a bacteriocin produced by E. faecium DPC1146. PCR using the primers designed in this study is a rapid and sufficient method of screening for bacteriocin-producing strains.

Journal Article↗
PubMed2026

Rgg144/SHP144-controlled streptolancidin D mediates intra-species competition in Streptococcus pneumoniae with cumulative effect from other bacteriocins and fratricide.

UNLABELLED: Streptococcus pneumoniae is a major colonizer of the human nasopharynx, where inter- and intra-strain competition plays a critical role in shaping population structure and influencing vaccine outcomes. Bacteriocins are key mediators of intra-species competition, yet many of their functions and regulatory mechanisms remain poorly understood. Here, we identify and characterize streptolancidin D, a previously uncharacterized bacteriocin encoded by the sldA-T locus, and demonstrate its contribution to pneumococcal competition. Using isogenic streptolancidin-producing and non-producing variants of a naturally colonizing strain, we show that sldA-T contributes to the inhibition of competitor strains in in vitro biofilms and during murine co-colonization. Importantly, streptolancidin D also inhibited in vitro a subset of genetically diverse pneumococcal isolates representing multiple serotypes, whereas non-producing variants showed no activity. This indicates that its effect is broad and not restricted to isogenic interactions. Genomic analysis of over 7,500 pneumococcal genomes revealed that sldA-T is present in ~12% of isolates, with lineage-associated distribution patterns, and is consistently encoded downstream of the Rgg144/SHP144 quorum sensing system. We further demonstrate that sldA-T is regulated by this system, with sldA-T promoter activity abolished in a SHP-deficient background and partially restored by exogenous peptide stimulation. Finally, we show that streptolancidin D acts in concert with other bacteriocin systems and competence-mediated fratricide, highlighting a multifactorial antimicrobial strategy that enhances pneumococcal competitiveness. Overall, our findings identify a quorum sensing-regulated bacteriocin that contributes to pneumococcal competition and helps shape population dynamics. IMPORTANCE: Bacteriocins are central to bacterial competition and niche occupation, particularly in structured environments like the human nasopharynx. While several pneumococcal bacteriocins have been characterized, the functions of many remain unknown, limiting our understanding of how these systems shape strain fitness and population dynamics. We characterize streptolancidin D, a bacteriocin that enhances intraspecies competitiveness in vitro and in vivo and contributes to the inhibition of genetically diverse pneumococcal strains. We demonstrate that its expression is tightly regulated by the conserved Rgg144/SHP144 quorum sensing system and that the locus is distributed and shows synteny across multiple pneumococcal lineages. Our findings reveal that streptolancidin D operates within a broader network of bacteriocins and competence-associated mechanisms that collectively shape competitive interactions. By integrating genomic, functional, and regulatory analyses, this work expands the known repertoire of pneumococcal antimicrobial systems and provides new insights into the mechanisms underpinning competition and population structure in S. pneumoniae.

Bacteriocins↗
PubMed1997

Multiple bacteriocin production by Leuconostoc mesenteroides TA33a and other Leuconostoc/Weissella strains.

Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins.

Bacteria↗
PubMed1994

Bacteriocins of leuconostocs isolated from meat.

Several bacteriocin-producing Leuconostoc strains have been isolated from meat and identified as Leuconostoc gelidum UAL 187, Leuconostoc paramesenteroides-La7a, Leuconostoc carnosum-Ta11a and Leuconostoc carnosum-La54a. All strains produce bacteriocins that are active against Listeria monocytogenes and other lactic acid bacteria of concern in meat spoilage. All of the bacteriocins studied are heat stable in acidic environments and are inactivated by a range of proteolytic enzymes but not by catalase or lysozyme. Most are detected early in the growth cycle and are produced at refrigeration temperatures and in a pH range of 4.0-7.0. Leucocin A-UAL187, produced by Leuconostoc gelidium UAL 187, is a small peptide (MW 3930) translated as a 61 amino acid prepeptide consisting of a 24 amino acid leader region and 37 amino acid active bacteriocin that is secreted. A probe designed from a region of the leucocin gene has been used to locate the bacteriocin genes in the other strains (La7a, La54a and Ta11a). Strong hybridization signals were detected from 8.9 MDa, 32 MDa and 8.9 MDa plasmids in strains La7a, La54a and Ta11a, respectively. The bacteriocin structural gene from Leuconostoc carnosum-Ta11a (leucocin B-Ta11a) has been cloned and sequenced and the bacteriocin shows 100% homology to leucocin A-UAL187; however, the prepeptide differs in six residues. The mature extracellular bacteriocin from strain UAL 187 was purified and characterized by precipitation, gel filtration, hydrophobic interaction chromatography followed by RP-HPLC and amino-terminal sequencing, whilst those of the other strains are in the process of being purified and characterized using similar techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2006

Antibacterial activity of a bacteriocin from Lactobacillus paracasei HL32 against Porphyromonas gingivalis.

Porphyromonas gingivalis infections cause problems in periodontal diseases and in certain systemic diseases. There is evidence that Lactobacillus spp. can control populations of P. gingivalis, but there are few data on the effects of purified bacteriocins from Lactobacillus paracasei HL32 on P. gingivalis. The objective of this study was to examine the antibacterial activity of a bacteriocin from L. paracasei HL32 and to relate this activity to its composition. A bacteriocin was purified from culture supernatants of Lactobacillus spp. using a dialysis technique followed by gel-permeation chromatography. Composition of the bacteriocin was characterised by ninhydrin tests, ultraviolet spectrophotometry, thin-layer chromatography, sodium-dodecyl sulphate-polyacrylamide gel electrophoresis, electrospray ionisation mass spectrometry and amino acid analysis. The amino acid sequence from the N-terminal of the bacteriocin was determined. Antibacterial activity was examined by the cylinder plate method, microtitre assay and scanning electron microscopy as compared with standard antibiotics. The bacteriocin had a molecular weight of approximately 56kDa, was comprised of 68% carbohydrate and 32% protein, and showed maximum peak absorbance at 214 and 254nm. The bacteriocin was found to be effective against P. gingivalis; it caused swelling and pore formation on the cell envelope at a minimum bactericidal concentration of 0.14mM, and caused death within 2h. Metronidazole killed P. gingivalis but did not affect the envelope, whereas tetracycline affected P. gingivalis with cell deformation. In conclusion, the bacteriocin from L. paracasei HL32 had the ability to kill P. gingivalis, suggesting that it could be a promising alternative chemotherapeutic agent for P. gingivalis infections.

Amino Acid Sequence↗
PubMed2000

Production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from Kimchi.

Lactococcus lactis subsp. lactis A164 was isolated from Kimchi (Korean traditional fermented vegetables). The bacteriocin produced by strain A164 was active against closely related lactic acid bacteria and some food-borne pathogens including Staphylococcus aureus, Listeria monocytogenes and Salmonella typhimurium. The antimicrobial spectrum was nearly identical to that of nisin. Bacteriocin activity was not destroyed by exposure to elevated temperatures at low pH values, but the activity was lost at high pH values. This bacteriocin was inactivated by pronase E and alpha, beta-chymotrypsin, but not by trypsin, pepsin, and alpha-amylase. Cultures of L. lactis subsp. lactis A164 maintained at a constant pH of 6.0 exhibited maximum production of the bacteriocin. It was purified to homogeneity by ammonium sulphate precipitation, sequential ion exchange chromatography, and ultrafiltration. Tricine-SDS-PAGE of purified bacteriocin gave the same molecular weight of 3.5 kDa as that of nisin. The gene encoding this bacteriocin was amplified by PCR with nisin gene-specific primers and sequenced. It showed identical sequences to the nisin gene. These results indicate that bacteriocin produced by Lactococcus lactis A164 is a nisin-like bacteriocin.

Bacteriocins↗
PubMed2001

Evidence for dual functionality of the operon plnABCD in the regulation of bacteriocin production in Lactobacillus plantarum.

The regulatory operon (plnABCD) involved in bacteriocin production in Lactobacillus plantarum C11 encodes four different proteins: a cationic prepeptide (PlnA); a histidine protein kinase (PlnB); and two highly homologous response regulators (PlnC and PlnD; over 75% sequence similarity). The mature product of PlnA, plantaricin A, serves as an extracellular pheromone that induces bacteriocin production. The exact roles of plnBCD in bacteriocin production have not been established experimentally. A reporter system containing the gusA gene fused with the plnA promoter was used to study plnABCD. We demonstrated that the plnABCD operon codes for an autoregulatory unit capable of activating its own promoter. Deletion analyses, performed in a heterologous expression host to define the roles of the individual genes, confirmed that both the inducer gene (plnA) and the kinase gene (plnB) are required for autoactivation. Apparently, the latter gene encodes a protein that serves as a receptor for the pheromone peptide. It was also demonstrated conclusively that the two regulators PlnC and PlnD, which have been shown previously to bind specifically to the DNA regulatory repeats of the plnA promoter, possess differential activities on the plnA promoter, with PlnC being much more active than PlnD. The functions of the response regulators were investigated further in the bacteriocin producer strain C11 in order to reveal their roles in bacteriocin production. Surprisingly, the two response regulators display totally opposite functions: although overexpression of plnC activated transcription and bacteriocin production, the overexpression of plnD repressed both processes, thus strongly suggesting that PlnD plays a role in the downregulation of bacteriocin synthesis. To our knowledge, this is the first evidence for a protein involved directly in negative regulation of bacteriocin production, and also it was shown for the first time that two highly homologous response regulators, with opposite functions, are encoded by genes located on the same operon.

Bacterial Proteins↗
PubMed2006

BAGEL: a web-based bacteriocin genome mining tool.

A common problem in the annotation of open reading frames (ORFs) is the identification of genes that are functionally similar but have limited or no sequence homology. This is particularly the case for bacteriocins, a very diverse group of antimicrobial peptides produced by bacteria and usually encoded by small, poorly conserved ORFs. ORFs surrounding bacteriocin genes are often biosynthetic genes. This information can be used to locate putative structural bacteriocin genes. Here, we describe BAGEL, a web server that identifies putative bacteriocin ORFs in a DNA sequence using novel, knowledge-based bacteriocin databases and motif databases. Many bacteriocins are encoded by small genes that are often omitted in the annotation process of bacterial genomes. Thus, we have implemented ORF detection using a number of published ORF prediction tools. In addition, BAGEL takes into account the genomic context, i.e. for each potential bacteriocin-encoding ORF, the sequence of the surrounding region on the genome is analyzed for genes that might encode proteins involved in biosynthesis, transport, regulation and/or immunity. These innovations make BAGEL unique in its ability to detect putative bacteriocin gene clusters in (new) bacterial genomes. BAGEL is freely accessible at: http://bioinformatics.biol.rug.nl/websoftware/bagel.

Amino Acid Motifs↗
PubMed1982

Group H streptococcal bacteriocins having no relation to bacterial transformation.

The culture filtrate of group H streptococcus strain Challis produced a competence factor (CF) for bacterial transformation as well as a bactericidal factor(s) against Wicky cells. Strain 36658, in the same streptococcal group, also produced the bactericidal factor(s) but not CF. The effect of the Challis bacteriocin was limited to strains Wicky and 58, whereas the 36658 bacteriocin affected 67% of 49 strains tested. Strain 58, one of the indicator strains, was affected by the bactericidal activity of these bacteriocins but not by CF activity, and failed to transform. No relationship between the bacteriocin-producing strains and indicator strains was observed. Both Challis and 36658 bacteriocin activities decreased markedly either when the bacteriocins were heated at 50 C for 30 min or with the addition of a protein synthesis inhibitor, but showed different sensitivities to trypsin, papain and lipase. The bacteriocins were of at least protein nature and their molecular weight was roughly estimated as 100,000 daltons by membrane filtration experiments. The 36658 bacteriocin is a new type of streptocin previously not reported. The possible absence of bacteriophage or phage-like particles in the preparations is discussed.

Bacterial Proteins↗