Bacteriocin Susceptibility of Clostridium perfringens: a Provisional Typing Schema

Ninety-four strains of Clostridium perfringens were examined for bacteriocin production. Bacteriocins produced by ten of these strains were selected for typing 274 cultures of C. perfringens. The bacteriocins were prepared by growing the producer strains in broth and precipitating the active principle from the supernatant fluids of centrifuged cultures with ammonium sulfate. All bacteriocins were titrated against a common indicator strain, adjusted to equivalent titers, and spotted onto blood agar plates seeded with the test organisms. Fifty different bacteriocin sensitivity patterns were observed. These patterns were organized into seven groups bearing some relationship, and the largest number of strains falling into any one pattern did not exceed 16% of the total strains tested. Ninety-nine percent of all isolates were typable. The new method should prove useful in studies where strains must be fingerprinted.     

Characterisation of the bacteriocins produced by two probiotic Lactobacillus isolates from idli batter

Lactobacillus plantarum JJ18 and Lactobacillus plantarum subsp. plantarum JJ60, probiotics from idli batter, produce bacteriocins JJ18 and JJ60 having a wide spectrum of activity. After optimising the environmental conditions for bacteriocin production the effect of various media components was determined. Maximum bacteriocin production was observed in MRS broth, pH 6.4 at 37 °C after 36 h. Tryptone (as nitrogen source) and glucose (as carbon source) are required for optimal production of bacteriocins JJ18 and JJ60. Activity was not affected by surfactants like Triton X-100, Tween 80 and Tween 20 or by treatment with NaCl, urea and EDTA. Protease treatment resulted in complete loss of activity of the partially purified bacteriocins JJ18 and JJ60, while lipase and α-amylase had no effect, indicating that the bacteriocin is a simple protein. Tris tricine SDS-PAGE electrophoresis depicted a single band of less than 3.5 kDa. However, the strain Lactobacillus plantarum JJ18 was inhibited by bacteriocin JJ60 and Lactobacillus plantarum JJ60 by bacteriocin JJ18, whereas no inhibition was observed against the respective producer strains, indicating that the two bacteriocins are different. The bacteriocins remained active over a wide range of pH and temperature. The bacteriocins were able to adsorb onto producer and target cells, Lactobacillus plantarum and Listeria monocytogenes and differentially in the presence of various surfactants, salts and solvents. A bactericidal mode of action was observed against Listeria monocytogenes. Given their wide spectrum of activity against various pathogens, the bacteriocins JJ18 and JJ60 can be applied as bio-preservatives in the food industry.     

Computerized evaluation procedure for comparing the electrophoretic protein patterns of bacterial strains

Among 46 isolates of Staphylococcus aureus obtained from cattle in the State of Paraíba, Brazil, four were shown to produce antimicrobial substances (AMS). The two best AMS producers carried single plasmids of about 8·0 kbp and 50 kbp, respectively, which were designated pRJ34 and pRJ35. Curing experiments and molecular analysis associated the AMS production with the presence of these plasmids in the cells. The biochemical properties exhibited by the AMS suggested that they might be bacteriocins (Bac). The bacteriocin encoded by pRJ34 showed properties identical to those of the bacteriocins encoded by other small staphylococcal Bac plasmids. However, the bacteriocin encoded by the large plasmid pRJ35 has shown some properties which distinguish it from the other bacteriocins of Staph. aureus described so far, suggesting it may be a new member of the staphylococcal bacteriocin family.     

Effects of prebiotic oligosaccharides and trehalose on growth and production of bacteriocins by lactic acid bacteria

AIMS: To investigate the effects of two prebiotics and trehalose on the production of bacteriocins. METHODS AND RESULTS: Four carbohydrates [dextrose, fructo-oligosaccharides (FOS), raffinose, and trehalose] were used as the sole carbon source in a simple broth. Five bacteriocin-producing strains of bacteria, including those producing nisin, enteriocin, and other bacteriocins, were used, and their inhibitory activities when grown on each carbohydrate were determined. The inhibitory activity assay was performed using the agar well diffusion method, and Lactobacillus sakei JCM 1,157(T) was used as the indicator strain. Effective enhancement of bacteriocin production was observed with FOS and trehalose incubation. CONCLUSIONS: The results suggest that FOS and trehalose can effectively enhance the production of the five kinds of bacteriocins evaluated in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: This study offers useful information for not only a new application of FOS and trehalose, but also the potential improvement of food preservation.     

Antimicrobial substances produced by Staphylococcus aureus strains isolated from cattle in Brazil

Among 46 isolates of Staphylococcus aureus obtained from cattle in the State of Paraíba, Brazil, four were shown to produce antimicrobial substances (AMS). The two best AMS producers carried single plasmids of about 8·0 kbp and 50 kbp, respectively, which were designated pRJ34 and pRJ35. Curing experiments and molecular analysis associated the AMS production with the presence of these plasmids in the cells. The biochemical properties exhibited by the AMS suggested that they might be bacteriocins (Bac). The bacteriocin encoded by pRJ34 showed properties identical to those of the bacteriocins encoded by other small staphylococcal Bac plasmids. However, the bacteriocin encoded by the large plasmid pRJ35 has shown some properties which distinguish it from the other bacteriocins of Staph. aureus described so far, suggesting it may be a new member of the staphylococcal bacteriocin family.     

Searching for bacteriocin-producing lactic acid bacteria in soil

A survey was conducted on the isolation and characterization of bacteriocin-producing lactic acid bacteria in soil. Forty-two acid-producing bacterial strains were isolated from 55 soil samples collected in Yamanashi prefecture, Japan. Investigation of antibacterial activities of isolates revealed that three isolates, Lactobacillus animalis C060203, Enterococcus durans C102901 and Leuconostoc mesenteroides subsp. mesenteroides C060204, showed antibacterial activities against the indicator strain of Lactobacillus sakei JCM 1157T. Bacteriocin from Enterococcus durans C102901 showed different characteristics from the known durancin L28-1A, produced by Enterococcus durans L28-1. Furthermore, this is the first report of a bacteriocin being produced by Lactobacillus animalis. Viewing from the species, bacteriocins from strains C102901 and C060203 showed high possibilities for the novel substances. These significant findings suggest that soil may be a common source for the isolation of novel bacteriocin-producing lactic acid bacteria.     

Detection and characterization of a novel antibacterial substance produced by a Lactobacillus delbrueckii strain 1043

A novel antibacterial substance produced by a strain isolated from Bulgarian yellow cheese was characterized. The producer strain was identified by molecular typing to belong to the species Lactobacillus delbrueckii , which is a rare producer of bacteriocins. The inhibitory agent was heat stable and active against lactic acid bacteria species and several food-borne pathogens : Listeria monocytogenes , Staphylococcus aureus , Enterococcus faecalis , Escherichia coli , Yersinia enterocolitica and Y. pseudotuberculosis . Its sensitivity to amylolitic enzymes and lipase suggested that a lipid and carbohydrate moiety could be important for the activity. The amino acid content of the purified bacteriocin was estimated to 29 amino acids. The bacteriocin was shown to be small (3·6–6 kDa) by three different methods : HPLC gel-filtration, SDS-PAGE and amino acid contents.     

Identification and production of a bacteriocin from Enterococcus mundtii QU 2 isolated from soybean

AIMS: Identification of the bacteriocin produced by Enterococcus mundtii QU 2 newly isolated from soybean and fermentative production of the bacteriocin. METHODS AND RESULTS: The bacteriocin produced by Ent. mundtii QU 2 inhibited the growth of various indicator strains, including Enterococcus, Lactobacillus, Leuconostoc, Pediococcus and Listeria. The bacteriocin activity was stable at wide pH range and against heat treatment, but completely abolished by proteolytic enzymes. The bacteriocin was purified from the culture supernatant by the three-step chromatographic procedure. Mass spectrometry, amino acid sequencing and DNA sequencing revealed that the bacteriocin was similar to class IIa bacteriocins produced by other Ent. mundtii strains. The bacteriocin production decreased in the absence of glucose, nitrogen sources, or Tween 80 in MRS medium. Additionally, it was strongly suppressed by addition of Ca(2+) (CaCO(3) or CaCl(2)). In pH-controlled fermentations, the highest bacteriocin production was achieved at pH 6.0, whereas the highest cell growth was obtained at pH 7.0. CONCLUSIONS: Ent. mundtii QU 2 produced a class IIa bacteriocin. Some growth factors (e.g. Ca(2+) and pH) influenced the bacteriocin production. SIGNIFICANCE AND IMPACT OF THE STUDY: A new soybean isolate, Ent. mundtii QU 2 was found to be a class IIa bacteriocin producer. Factors influencing the bacteriocin production described herein are valuable for applications of the bacteriocins from Ent. mundtii strains.     

Antimicrobial activity and occurrence of bacteriocin structural genes in Enterococcus spp. of human and animal origin isolated in Portugal

The main objective of this study was to detect the antimicrobial activity and the presence of bacteriocin structural genes in 224 enterococcal isolates from fecal origin obtained from humans, pets, wild animals and birds. Direct antimicrobial activity against Listeria monocytogenes CECT4032 was detected in 102 (45.6%) of the tested isolates. From these, only 22 displayed bacteriocin activity against this indicator. The bacteriocinogenic strains contained one or more of the bacteriocin structural genes tested in this study, with those of enterocins P, A and L50 (L50A and L50B) being the most abundant. Our results show a high occurrence of the combination of different bacteriocin structural genes in the enterococcal isolates analyzed, indicating an elevated genetic potential of these strains to produce various bacteriocins.     

Isolation and partial characterization of a bacteriocin produced by Pediococcus pentosaceus K23-2 isolated from Kimchi

Aims:  Screening and partial characterization of a bacteriocin produced by Pediococcus pentosaceus K23-2 isolated from Kimchi, a traditional Korean fermented vegetable.
Methods and Results:  A total of 1000 lactic acid bacteria were isolated from various Kimchi samples and screened for the production of bacteriocin. Pediocin K23-2, a bacteriocin produced by the Pediococcus pentosaceus K23-2 strain, showed strong inhibitory activity against Listeria monocytogenes . The bacteriocin activity remained unchanged after 15 min of heat treatment at 121°C or exposure to organic solvents; however, it diminished after treatment with proteolytic enzymes. The bacteriocin was maximally produced at 37°C, when the pH of the culture broth was maintained at 5·0 during the fermentation, although the optimum pH for growth was 7·0. The molecular weight of the bacteriocin was about 5 kDa according to a tricine SDS-PAGE analysis.
Conclusions:  Pediococcus pentosaceus K23-2 isolated from Kimchi produces a bacteriocin, which shares similar characteristics to the Class IIa bacteriocins. The bacteriocin is heat stable and shows wide antimicrobial activity against Gram-positive bacteria, especially L. monocytogenes .
Significance and Impact of the Study:  Pediocin K23-2 and pediocin K23-2-producing P. pentosaceus K23-2 could potentially be used in the food and feed industries as natural biopreservatives, and for probiotic application to humans or livestock.     

Intra-specific variation of Lactobacillus plantarum and Lactobacillus pentosus in sensitivity towards various bacteriocins

Fifty-two strains belonging to the Lactobacillus plantarum species group were identified and typed. They represented 32 clones of Lactobacillus plantarum and 7 clones of Lactobacillus pentosus. Sensitivity of all strains towards bacteriocins of four different producer strains was investigated using a deferred inhibition test (DIT). Substantial intra-specific variation in sensitivity of clones was observed towards bacteriocinogenic lactic acid bacteria producing nisin ( Lactococcus lactis ATCC 11454) or pediocin PA-1 ( Pediococcus acidilactici PAC-1.0), while none of the strains were sensitive towards the two remaining bacteriocin producers. The minimum inhibitory concentration (MIC) of nisin towards selected strains confirmed the DIT results. No correlation between the susceptibility of fourteen selected strains towards nisin and an array of antibiotics was found. The present study indicates that the variation in bacteriocin-sensitivity within target species might be a potential limitation for the application of bacteriocins as biopreservatives.     

Further development of a bacteriocin typing system for Clostridium perfringens

The specificity of typing Clostridium perfringens with bacteriocins was improved by adding new bacteriocins and deleting others from the original typing set of ten. A total of 516 new isolates of Cl. perfringens were screened for bacteriocin production and, of these, 162 strains (31%) were found to be producers. The sensitivity patterns obtained by testing 40 bacteriocins against 200 isolates of Cl. perfringens were recorded and the data subjected to a computer analysis. A total of 18 bacteriocins capable of dividing the 200 isolates into 98 typing patterns was selected. The repro-ducibility of the new system was tested by performing three sequential typings of 60 strains of Cl. perfringens. No variation was found in 73% of the strains, while a further 16% of the strains demonstrated a change in sensitivity to only one bacteriocin. Common serological types of Cl. perfringens were divisible into subtypes based upon both their ability to produce bacteriocins and their sensitivity to bacteriocins, suggesting a useful role for bacteriocin typing in conjunction with an already well-established tool for typing Cl. perfringens.     

Antimicrobial activity of lactic acid bacteria isolated from sour doughs: purification and characterization of bavaricin A, a bacteriocin produced by Lactobacillus bavaricus MI401

Three hundred and thirty-five lactic acid bacteria were isolated from sour doughs and screened for antagonistic activity. Of these 145 showed activity against one or several of the indicator strains used in the screening. The antimicrobial activity of 18 isolates were due to a proteinaceous compound. These 18 isolates belonged to three different Lactobacillus species: Lactobacillus bavaricus, Lactobacillus curvatus and Lactobacillus plantarum. The spectrum of antimicrobial activity for the three species suggested that the inhibitory components were different. The inhibitory compound from Lact. bavaricus MI401 was chosen for further study. The proteinaceous nature, antimicrobial activity against closely-related species, heat resistance and sensitivity to alkaline treatment strongly indicated that this substance was a bacteriocin, which we designated bavaricin A. The bacteriocin was purified to homogeneity by ammonium sulphate precipitation, ion exchange, hydrophobic interaction and reverse-phase chromatography. The purification resulted in 193000-fold increase in specific activity. SDS-PAGE of bavaricin A showed a molecular weight of 3500—4000 Da. By amino acid sequencing 41 amino acids were determined. Bavaricin A had a bactericidal mode of action and inhibited nine out of 10 Listeria monocytogenes. Lactobacillus bavaricus MI401 produced bavaricin A at temperatures from 4°C to 30°C. The production of active bavaracin A was inhibited at increasing sodium chloride concentration. In the presence of 3% sodium chloride at 4°C no active bavaricin A could be detected. Nitrite (100 ppm) did not affect the production of active bavaricin A.     

Diversity of bacteriocins and activity spectrum in Streptococcus pneumoniae

The production of bacteriocins can be favorable for colonization of the host by eliminating other bacterial species that share the same environment. In Streptococcus pneumoniae, the pnc (blp) locus encoding putative bacteriocins, immunity, and export proteins is controlled by a two-component system similar to the comCDE system required for the induction of genetic competence. A detailed comparison of the pnc clusters of four genetically distinct isolates confirmed the great plasticity of this locus and documented several repeat sequences. Members of the multiple-antibiotic-resistant Spain23F-1 clone, one member of the Spain9V-3 clone, sensitive 23F strain 2306, and the TIGR4 strain produced bactericidal substances active against other gram-positive bacteria and in some cases against S. pneumoniae as well. However, other strains did not show activity against the indicator strains despite the presence of a bacteriocin cluster, indicating that other factors are required for bacteriocin activity. Analysis of strain 2306 and mutant derivatives of this strain confirmed that bacteriocin production was dependent on the two-component regulatory system and genes involved in bacteriocin transport and processing. At least one other bacteriocin gene, pncE, is located elsewhere on the chromosome and might contribute to the bacteriocin activity of this strain.     

Factors affecting the adsorption of bacteriocins ST194BZ and ST23LD to Lactobacillus sakei and Enterococcus sp

Bacteriocins ST194BZ and ST23LD, produced by Lactobacillus plantarum, inhibit Gram-positive and Gram-negative bacteria. Images obtained by atomic force microscopy showed clear signs of membrane damage of Lactobacillus sakei, accompanied by the leakage of DNA and beta-galactosidase. Adsorption of the bacteriocins to cells was increased when cells were treated with buffers at pH values above neutral. An increase in bacteriocin ST194BZ adsorption to cells of Enterococcus sp. and L. sakei was observed with an increase in incubation temperatures, but at different rates for the two species. Treatment of the two species with various inorganic salts and solvents gave different results regarding the adsorption of the two bacteriocins. In general, pre-treatment of the two sensitive cells with Triton X-100, Triton X-114 and chloroform increased the adsorption of the two bacteriocins. Increased adsorption of bacteriocin ST23LD to L. sakei was recorded when the cells were pre-treated with Tris and NH4-citrate. Treatment of Enterococcus sp. and L. sakei with Na-EDTA and SDS decreased the adsorption of the two bacteriocins. Variable results were recorded with inorganic salts.     

Native and heterologous production of bacteriocins from gram-positive microorganisms

In nature, microorganisms can present several mechanisms for setting intercommunication and defense. One of these mechanisms is related to the production of bacteriocins, which are peptides with antimicrobial activity. Bacteriocins can be found in Gram-positive and Gram-negative bacteria. Nevertheless, bacteriocins produced by Gram-positive bacteria are of particular interest due to the industrial use of several strains that belong to this group, especially lactic acid bacteria (LAB), which have the status of generally recognized as safe (GRAS) microorganisms. In this work, we will review recent tendencies in the field of invention and state of art related to bacteriocin production by Gram-positive microorganism. Hundred-eight patents related to Gram-positive bacteriocin producers have been disclosed since 1965, from which 57% are related bacteriocins derived from Lactococcus, Lactobacillus, Streptococcus, and Pediococcus strains. Surprisingly, patents regarding heterologous bacteriocins production were mainly presented just in the last decade. Although the major application of bacteriocins is concerned to food industry to control spoilage and foodborne bacteria, during the last years bacteriocin applications have been displacing to the diagnosis and treatment of cancer, and plant disease resistance and growth promotion.     

Isolation and characterization of bacteriocin‐producing bacteria from the intestinal microbiota of elderly Irish subjects

Aims

To isolate and characterize bacteriocins produced by predominant species of lactic acid bacteria from faeces of elderly subjects.

Methods and Results

Screening over 70 000 colonies, from faecal samples collected from 266 subjects, using the indicator organisms Lactobacillus bulgaricus LMG 6901 and Listeria innocua DPC 3572, identified 55 antimicrobial‐producing bacteria. Genomic fingerprinting following ApaI digestion revealed 15 distinct strains. The antimicrobial activities associated with 13 of the 15 strains were sensitive to protease treatment. The predominant antimicrobial‐producing species were identified as Lactobacillus salivarius, Lactobacillus gasseri, Lactobacillus acidophilus, Lactobacillus crispatus and Enterococcus spp. A number of previously characterized bacteriocins, including ABP‐118 and salivaricin B (from Lact. salivarius), enterocin B (Enterococcus faecium), lactacin B (Lact. acidophilus), gassericin T and a variant of gassericin A (Lact. gasseri), were identified. Interestingly, two antimicrobial‐producing species, not generally associated with intestinally derived microorganisms were also isolated: Lactococcus lactis producing nisin Z and Streptococcus mutans producing mutacin II.

Conclusion

These data suggest that bacteriocin production by intestinal isolates against our chosen targets under the screening conditions used was not frequent (0·08%).

Significance and Impact of the Study

The results presented are important due to growing evidence indicating bacteriocin production as a potential probiotic trait by virtue of strain dominance and/or pathogen inhibition in the mammalian intestine.     

Bioassay for the rapid detection of bacteriocins in fermentation broth

A bioassay for the rapid detection of bacteriocins by detecting efflux of K⁺ ions from a bacteriocin-sensitive indicator strain was developed. There was a rapid increase in concentration of K⁺ in the medium from approximately 1.6 to 9.5 mM when the crude bacteriocin was added to the sensitive strain. A bacteriocin activity of 8.25 AU ml^–1 produced the lowest detectable concentration of K⁺ (0.179 mM) and the smallest inhibition zone (0.4 mm). The smallest cell dry mass of the indicator strain capable of releasing a detectable level of K⁺ (0.102 mM) was 0.76 mg. Detection of the bacteriocin by measuring the efflux of K⁺ compares well with the conventional agar well diffusion assay. Low activities of bacteriocin and low amounts of the sensitive indicator strain biomass can be used with this bioassay.     

Plantaricins S and T, Two New Bacteriocins Produced by Lactobacillus plantarum LPCO10 Isolated from a Green Olive Fermentation

Twenty-six strains of Lactobacillus plantarum isolated from green olive fermentations were tested for cross-antagonistic activities in an agar drop diffusion test. Cell-free supernatants from four of these strains were shown to inhibit the growth of at least one of the L. plantarum indicator strains. L. plantarum LPCO10 provided the broadest spectrum of activity and was selected for further studies. The inhibitory compound from this strain was active against some gram-positive bacteria, including clostridia and propionibacteria as well as natural competitors of L. plantarum in olive fermentation brines. In contrast, no activity against gram-negative bacteria was detected. Inhibition due to the effect of organic acids, hydrogen peroxide, or bacteriophages was excluded. Since the inhibitory activity of the active supernatant was lost after treatment with various proteolytic enzymes, this substance could be classified as a bacteriocin, designated plantaricin S. Plantaricin S was also sensitive to glycolytic and lipolytic enzymes, suggesting that it was a glycolipoprotein. It exhibited a bactericidal and nonbacteriolytic mode of action against indicator cells. This bacteriocin was heat stable (60 min at 100 degrees C), active in a pH range of 3.0 to 7.0, and also stable in crude culture supernatants during storage. Ultrafiltration studies indicated that plantaricin S occurred as multimolecular aggregates and that the size of the smallest active form is between 3 and 10 kDa. In sodium dodecyl sulfate-polyacrylamide gels, plantaricin S migrated as a peptide of ca. 2.5 kDa. Maximum production of plantaricin S was obtained in a fermentor system in unregulated pH and log-phase cultures of L. plantarum LPCO10 in MRS broth plus 4% NaCl. In these culture conditions, a second bacteriocin (designated plantaricin T) was produced in late-stationary-phase cultures of L. plantarum LPCO10. On the basis of its biological activity, its sensitivity to various enzymes, and its molecular weight (lower than that of plantaricin S) as assessed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, plantaricin T appeared different from plantaricin S. Curing experiments with L. plantarum LPCO10 resulted in the appearance of variants that no longer produced either of the two bacteriocins but that were still immune to both of them.     

An analysis of bacteriocins produced by lactic acid bacteria isolated from malted barley

AIMS: The aim of this study was to perform a detailed characterization of bacteriocins produced by lactic acid bacteria (LAB) isolated from malted barley. METHODS AND RESULTS: Bacteriocin activities produced by eight LAB, isolated from various types of malted barley, were purified to homogeneity by ammonium sulphate precipitation, cation exchange, hydrophobic interaction and reverse-phase liquid chromatography. Molecular mass analysis and N-terminal amino acid sequencing of the purified bacteriocins showed that four non-identical Lactobacillus sakei strains produced sakacin P, while four Leuconostoc mesenteroides strains were shown to produce bacteriocins highly similar or identical to leucocin A, leucocin C or mesenterocin Y105. Two of these bacteriocin-producing strains, Lb. sakei 5 and Leuc. mesenteroides 6, were shown to produce more than one bacteriocin. Lactobacillus sakei 5 produced sakacin P as well as two novel bacteriocins, which were termed sakacin 5X and sakacin 5T. The inhibitory spectrum of each purified bacteriocin was analysed and demonstrated that sakacin 5X was capable of inhibiting the widest range of beer spoilage organisms. CONCLUSION: All bacteriocins purified in this study were class II bacteriocins. Two of the bacteriocins have not been described previously in the literature while the remaining purified bacteriocins have been isolated from environments other than malted barley. SIGNIFICANCE AND IMPACT OF THE STUDY: This study represents a thorough analysis of bacteriocin-producing LAB from malt and demonstrates, for the first time, the variety of previously identified and novel inhibitory peptides produced by isolates from this environment. It also highlights the potential of these LAB cultures to be used as biological controlling agents in the brewing industry.