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At least 19 recordsLinked to original sources

PubMed1986

In vivo significance of bacteriocins and bacteriocin receptors.

Bacteriocins are protein or protein-complex antibiotics produced by a wide variety of bacterial species. By conventional definition, bacteriocins differ from most other antibiotics in that the producer strain is immune to the action of its own bacteriocin and the inhibitory activity of individual bacteriocins is directed only to bacteria which are closely related to the strains which produce them. Bacteriocin production is regulated by plasmid or chromosomal elements and bacteriocin activity is initiated by adsorption of bacteriocin to specific outer membrane receptors on susceptible cells. In Darwinian terms, production of bacteriocin by a bacterial strain, within a particular ecological niche, could be considered advantageous by ensuring elimination of other closely related, and thus competitive, bacteria. In contrast, conservation of bacteriocin receptors appears suicidal if their only function is to initiate cell death. The paper will illustrate the ubiquity of bacteriocins and discuss evidence for their in vivo function in terms of bacterial survival. Evidence will also be presented to indicate that bacteriocin receptors in Escherichia coli and Pseudomonas aeruginosa have important alternative physiological functions in outer-membrane mediated nutrient uptake, particularly with respect to bacterial iron metabolism.

Bacteriocins↗

PubMed1992

Cloning, sequencing, and expression in Escherichia coli of lcnB, a third bacteriocin determinant from the lactococcal bacteriocin plasmid p9B4-6.

On the bacteriocin plasmid p9B4-6 of Lactococcus lactis subsp. cremoris 9B4, a third bacteriocin determinant was identified. The genes encoding bacteriocin production and immunity resided on a 1.2-kb CelII-ScaI fragment and were located adjacent to one of two previously identified bacteriocin operons (M. J. van Belkum, B. J. Hayema, R. E. Jeeninga, J. Kok, and G. Venema, Appl. Environ. Microbiol. 57:492-498, 1991). The fragment was sequenced and analyzed by deletion and mutation analyses. The bacteriocin determinant consisted of two genes which were transcribed as an operon. The first gene (lcnB), containing 68 codons, was involved in bacteriocin activity. The second gene (lciB) contained 91 codons and was responsible for immunity. The specificity of this novel bacteriocin, designated lactococcin B, was different from that of the other two bacteriocins specified by p9B4-6. Part of the nucleotide sequence of the lactococcin B operon was similar to a nucleotide sequence also found in the two other bacteriocin operons of p9B4-6. This conserved region encompassed a nucleotide sequence upstream of the bacteriocin gene and the 5' part of the gene. When the lactococcin B operon was expressed in Escherichia coli by using a T7 RNA polymerase-specific promoter, antagonistic activity could be detected.

Amino Acid Sequence↗

PubMed1969

Concomitant synthesis of bacteriocin and bacteriocin inactivator from Serratia marcescens.

We have found that Serratia marcescens strain P & S is bacteriocinogenic. However, the phenotypic expression of bacteriocin activity depends upon the temperature at which the cells are grown. When the organism is grown at 30 to 37 C, no bacteriocin activity can be demonstrated, whereas when it is grown at 39 C bacteriocin activity is readily observed. It appears that the P & S strain concomitantly synthesizes a bacteriocin and a substance which not only can inactivate the bacteriocin but also has a high activation energy for inactivation. This inactivator readily loses its activity when heated at 39 C for 1 hr. Two mutants were isolated from the P & S strain which can produce active bacteriocin when grown at temperatures from 30 to 39 C. It is significant that these mutants have considerably less bacteriocin inactivator. The data suggest that the inactivator is an extracellular protease. The ability of one of these mutants, JF58-12, to produce active bacteriocin at temperatures between 30 and 39 C is a stable property, whereas in the other mutant, JF48W, this property is unstable. JF48W was selected from the P & S strain in two steps: first a streptomycin-resistant variant (strain A-10) was isolated and from this mutant a strain (JF48W) was isolated which not only synthesized little of the inactivator but also did not synthesize the red pigmnet prodigiosin. This latter pleiotropic mutant appears to revert in one step to a phenotype similar to the P & S strain, since it is streptomycin-sensitive and produces prodigiosin and normal amounts of inactivator and the demonstration of bacteriocin activity is temperature-dependent.

Bacteriocins↗

PubMed1976

Studies on group A (phage tail) bacteriocins of Serratia marcescens. V. Serological characterization of subgroup I and II bacteriocins.

Neutralization tests with rabbit hyperimmune sera revealed a close, if not identical, serological relationship among 7 group A (phage tail) bacteriocins of Serratia marcescens of subgroup I, and among 3 phage tail bacteriocins of subgroup II, respectively. On the other hand, subgroup I and II phage tail bacteriocins were found to be serologically unrelated, as determined with neutralization tests and Ouchterlony immunodiffusion experiments. Immunoelectrophoretic tests, employing a representive phage tail bacteriocin of each of the two subgroups, disclosed the electrophoretic mobility of bacteriocin no. 5 (subgroup I), whereas bacteriocin no. 16 (subgroup II) remained stationary. Thus, two additional differential criteria, i.e., differences in antigenicity and electrophoretic mobility, were obtained for the characterization of subgroup I and II group A (phage tail) bacteriocins of S. marcescens.

Animals↗

PubMed1983

Molecular structure and function of the bacteriocin gene and bacteriocin protein of plasmid Clo DF13.

In this paper we present the complete nucleotide sequence of the bacteriocin gene of plasmid Clo DF13. According to the predicted aminoacid sequence the bacteriocin, cloacin DF13, consists of 561 aminoacids and has a molecular weight of 59,293 D. To obtain insight into the structure and function of specific parts of the cloacin molecule, we constructed a hydration profile and we predicted the secondary structure of the protein. According to our predictions, the N-terminus of cloacin DF13 (corresponding to the first 150-180 aminoacids) is relatively hydrophobic and is rich in glycine residues. The data obtained support previous findings that the N-terminal part of cloacin DF13 is involved in translocation of this protein across the cell membrane. The C-terminal part of the cloacin protein is rich in positively charged aminoacids; this might reflect the RNase activity located within this domain. A comparison of the bacteriocin genes and corresponding proteins of Clo DF13 and Col E1 did not reveal any homology at the level of either the nucleotide or the aminoacid sequence. The codon usage of both genes, however, exhibits striking similarities. The sequence data obtained during this study enabled us to present the nucleotide sequence of the entire cloacin operon. The structure of this operon and the regulation of expression of the genes, located within this operon, is discussed.

Amino Acid Sequence↗

PubMed1989

Cloning of two bacteriocin genes from a lactococcal bacteriocin plasmid.

Lactococcus lactis subsp. cremoris 9B4 plasmid p9B4-6 (60 kilobases [kb]), which specifies bacteriocin production and immunity, was analyzed with restriction endonucleases, and fragments of this plasmid were cloned into shuttle vectors based on the broad-host-range plasmid pWVO1. Two regions on p9B4-6 were identified which specify inhibitory activity on L. lactis indicator strains: one that could be confined to a 1.8-kb ScaI-ClaI fragment with low antagonistic activity and a 15-kb XbaI-SalI fragment specifying high antagonistic activity. The inhibitory substances produced by these two clones were sensitive to proteolysis. A 4-kb HindIII fragment derived from the 15-kb fragment strongly hybridized with the 1.8-kb fragment. The antagonistic activity specified by the 4-kb fragment was somewhat reduced as compared with that of the 15-kb fragment. A 1.3-kb ScaI-HindIII subfragment of the 4-kb fragment contained both the immunity and bacteriocin genes. Inhibition studies showed that the two bacteriocins had different specificities.

Bacteriocins↗

PubMed1976

Studies on group A (phage tail) bacteriocins of Serratia marcescens. VI. Calcium ion-dependent biological activity of subgroup II bacteriocins.

The biological activity of subgroup II group A (phage tail) bacteriocins of Serratia marcescens against susceptible indicator cells was completely abolished on two defined, Agarose-containing media. The addition of 0.002 M CaC12 to these two media fully restored the lethal activity of these phage tails. Subgroup I phage tail bacteriocins, on the other hand, were found to have no requirement for divalent cations. These observations furnished an additional biological criterion for the differentiation of subgroup I and II phage tail bacteriocins of S. marcescens.

Bacteriocins↗

PubMed1987

Restriction enzyme analysis of lactose and bacteriocin plasmids from Streptococcus lactis subsp. diacetylactis WM4 and cloning of BclI fragments coding for bacteriocin production.

The 131.1-kilobase (kb) bacteriocin production (Bac) plasmid pNP2 and the 63.6-kb lactose metabolism (Lac) plasmid pCS26, from Streptococcus lactis subsp. diacetylactis WM4, as well as pWN8, a 116.7-kb recombinant plasmid from a Lac+ transconjugant, were analyzed with restriction enzymes to determine the origin of pWN8. Plasmid pWN8 conferred a Lac+ Bac- phenotype, contained DNA derived from pCS26 and pNP2, and, like pNP2, exhibited self-transmissibility (Tra+). In cloning attempts, Bac+ transformant S. lactis KSH1 was isolated. The recombinant plasmid, pKSH1, contained three BclI fragments from pNP2. Bac- transformants which individually contained each of the three fragments were also identified. Comparison of restriction maps of pKSH1 and pNP2 revealed an 18.4-kb region common to both plasmids, involving two of the three BclI fragments. S. lactis KSH1 also exhibited greater inhibitory activity against the indicator strain S. diacetylactis 18-16 than did a strain containing the 131.1-kb Bac plasmid.

Bacteriocin Plasmids↗

PubMed1966