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At least 19 recordsLinked to original sources
PubMed1997

The C-terminal region of nisin is responsible for the initial interaction of nisin with the target membrane.

The interaction of nisin Z and a nisin Z mutant carrying a negative charge in the C-terminus ([Glu-32]-nisin Z) with anionic lipids was characterized in model membrane systems, and bacterial membrane systems. We focused on three possible steps in the mode of action of nisin, i.e., binding, insertion, and pore formation of nisin Z. Increasing amounts of anionic lipids in both model and natural membranes were found to strongly enhance the interaction of nisin Z with the membranes at all stages. The results reveal a good correlation between the anionic lipid dependency of the three stages of interaction, of which the increased binding is probably the major determinant for antimicrobial activity. Maximal nisin Z activity could be observed for negatively charged lipid concentrations exceeding 50-60%, both in model membrane systems as well as in bacterial membrane systems. We propose that the amount of negatively charged lipids of the bacterial target membrane is a major determinant for the sensitivity of the organism for nisin. Nisin Z induced leakage of the anionic carboxyfluorescein was more efficient as compared to the leakage of the potassium cation. This lead to the conclusion that an anion-selective pore is formed. In contrast to the results obtained for nisin Z, the binding of [Glu-32]-nisin Z to vesicles remained low even in the presence of high amounts of negatively charged lipids. The insertion and pore-forming ability of [Glu-32]-nisin Z were also decreased. These results demonstrate that the C-terminus of nisin is responsible for the initial interaction of nisin, i.e., binding to the target membrane.

Amino Acid Sequence↗
PubMed1996

Genes responsible for nisin synthesis, regulation and immunity form a regulon of two operons and are induced by nisin in Lactoccocus lactis N8.

Nisin is a small post-translationally modified lanthionine-containing peptide (lantibiotic) produced by certain Lactococcus lactis strains which has a high antimicrobial activity against several pathogenic Gram-positive bacteria. Northern blots and RT/PCR analysis of the nisin-producing strain N8 revealed that the nisZBTCIPRKFEG gene cluster, responsible for nisin biosynthesis, immunity and regulation, consists of two operons, nisZBTCIPRK and nisFEG. The promoter of the nisFEB operon was mapped. The -35 to -1 region upstream of the transcription start of the nisFEG promoter showed 73% identity with the corresponding region upstream of the nisA and nisZ gene. In contrast to earlier reports, nisin was found to be secreted during the early stages of growth was well as later in the growth cycle. The secreted nisin was adsorbed on the surface of the cells and was released to the medium during mid-exponential growth, when the pH in the medium fell below 5.5. In nisZB antisense and nisT deletion mutant strains constructed in this study the transcription of the nisin operons, nisin production and immunity were lost. Provision of external nisin restored the transcription of both operons in the mutant strains, showing that the operons are coordinately regulated by mature nisin. Nisin induction of the mutant strains also resulted in an increased amount of the NisI protein and an increase in the level of immunity. Induction using higher concentrations of nisin yielded a higher level of immunity. These results showed that the nisin promoters are under positive control in an autoregulatory manner and that antimicrobial peptides can also function as signal molecules.

Base Sequence↗
PubMed1999

Production and utilization of polyclonal antibodies against nisin in an ELISA and for immuno-location of nisin in producing and sensitive bacterial strains.

Specific nisin polyclonal antibodies (PAb) were produced in rabbits using nisin Z produced by Lactococcus lactis subsp. lactis biovar diacetylactis UL 719. Antisera were obtained from white female New Zealand rabbits that were first immunized with a nisin Z-keyhole limpet haemocyanin conjugate and boosted with free nisin Z. Nisin-specific PAb were purified by affinity chromatography with a yield of 15 mg specific antinisin 100 ml-1 serum. The detection limit of the ELISA test for nisin Z was 0.75 ng ml-1 in buffer but was 1.7 and 3.5 ng ml-1 in milk and complex media broth spiked (5, 10, 20 microg ml-1) with nisin Z, respectively. In nisin Z-spiked samples, the average concentration was between 90 and 107% of actual added amount. In contrast, when the bioassay (microtitration method) was used, only 50-63% of nisin Z biological activity could be detected. In addition, the affinity-purified nisin PAb, antirabbit IgG gold conjugate and transmission electron microscopy were successfully used to locate nisin Z on producing cells and to observe its bactericidal effects against sensitive cells.

Animals↗
PubMed1992

Novel paired starter culture system for sauerkraut, consisting of a nisin-resistant Leuconostoc mesenteroides strain and a nisin-producing Lactococcus lactis strain.

Nisin-resistant Leuconostoc mesenteroides NCK293 and nisin-producing Lactococcus lactis subsp. lactis NCK401 were evaluated separately and in combination for growth and nisin production in a model sauerkraut fermentation. Strains were genetically marked and selectively enumerated by using antibiotic-containing media. The growth and survival of L. mesenteroides were similar in the presence and absence of Lactococcus lactis subsp. lactis. The growth of Lactococcus lactis subsp. lactis was not inhibited, although the maximum cell density was reduced and the population decline was more pronounced in the presence of L. mesenteroides. Nisin was detected within 24 h, and levels were relatively constant over the 12-day test period. The maximum cell populations and nisin level achieved could be altered by changing the initial cell ratios of L. mesenteroides and lactococcus lactis subsp. lactis. Isogenic nisin-producing and nisin-negative Lactococcus lactis subsp. lactis derivatives were used in combination with nisin-resistant L. mesenteroides to demonstrate that nisin levels produced in mixed culture were sufficient to retard the onset of the growth of nisin-sensitive, homofermentative Lactobacillus plantarum ATCC 14917.

Colony Count, Microbial↗
PubMed1993

Characterization of the Lactococcus lactis nisin A operon genes nisP, encoding a subtilisin-like serine protease involved in precursor processing, and nisR, encoding a regulatory protein involved in nisin biosynthesis.

Biosynthesis of the lantibiotic peptide nisin by Lactococcus lactis NIZO R5 relies on the presence of the conjugative transposon Tn5276 in the chromosome. A 12-kb DNA fragment of Tn5276 including the nisA gene and about 10 kb of downstream DNA was cloned in L. lactis, resulting in the production of an extracellular nisin precursor peptide. This peptide reacted with antibodies against either nisin A or the synthetic leader peptide, suggesting that it consisted of a fully modified nisin with the nisin leader sequence still attached to it. This structure was confirmed by N-terminal sequencing and 1H-nuclear magnetic resonance analysis of the purified peptide. Deletion studies showed that the nisR gene is essential for the production of this intermediate. The deduced amino acid sequence of the nisR gene product indicated that the protein belongs to the family of two-component regulators. The deduced amino acid sequence of NisP, the putative product of the gene upstream of nisR, showed an N-terminal signal sequence, a catalytic domain with a high degree of similarity to those of subtilisin-like serine proteases, and a putative C-terminal membrane anchor. Cell extracts of Escherichia coli overexpressing nisP were able to cleave the nisin precursor peptide, producing active, mature nisin. A similar activation was obtained with whole cells but not with membrane-free extracts of L. lactis strains carrying Tn5276 in which the nisA gene had been inactivated. The results indicate that the penultimate step in nisin biosynthesis is secretion of precursor nisin without cleavage of the leader peptide, whereas the last step is the cleavage of the leader peptide sequence from the fully maturated nisin peptide.

Amino Acid Sequence↗
PubMed1997

The effect of nisin concentration and nutrient depletion on nisin production of Lactococcus lactis.

The kinetics of nisin production was studied in batch cultures using a construct of Lactococcus lactis subsp. lactis C2SmPrt-, containing a transposon (TnNip) that encodes nisin production. The introduction of TnNip into C2SmPrt- significantly lowered the specific growth rate and the maximum A620 reached was reduced from 15.2 to 11.0. The effect of nisin concentration and nutrient depletion on nisin production of the construct, C2SmPrt-(TnNip), was examined. Nisin production was found to be inhibited by high concentrations of nisin, when grown in excess nutrient, even though growth of the culture continued because nutrient limitation was not operating. However, in low nutrient concentrations nisin production was limited by nutrient depletion. The specific growth rate of C2SmPrt-(TnNip) was altered, by using different nutrient concentrations and different sugars, in order to examine the relationship between nisin production and growth. Nisin production was shown to be growth-associated for most of growth, but near the end of growth, when the specific growth rate was 0.05 h-1 or less, the production ceased.

DNA Transposable Elements↗
PubMed1996

Nisin Z, mutant nisin Z and lacticin 481 interactions with anionic lipids correlate with antimicrobial activity. A monolayer study.

Monomolecular layers of lipids at the air/water interface have been used as a model membrane to study membrane interactions of the lantibiotic nisin. The natural lantibiotics nisin A and nisin Z proved to have a high affinity for the anionic lipids phosphatidylglycerol and bis(phosphatidyl)glycerol (cardiolipin). The interaction with zwitterionic phopholipids or neutral lipids is very low at surface pressures higher than 32 mN/m. Nisin, nisin mutants and lacticin 481 show a remarkable correlation between anti-microbial activity and anionic lipid interaction. The results indicate that primarily the N-terminal part (residues 1-22) penetrates into the lipid phase. Reduction of the flexibility at positions 20-21 has a negative effect on monolayer interaction and activity. The C-terminal part is probably responsible for ionic interactions of nisin in monomeric or oligomeric form with anionic lipids. In mixtures of anionic and zwitterionic lipids maximal interactions are found at approximately 70 mol/100 mol anionic lipid. Gram-positive bacteria, which form the main target for nisin, are characterized by a high content of anionic lipids in the membrane. Monolayers formed of lipid extracts of bacteria sensitive to nisin were more strongly penetrated than those of bacteria relatively insensitive to nisin.

Amino Acid Sequence↗
PubMed2000

Sensitivity of nisin-resistant Listeria monocytogenes to heat and the synergistic action of heat and nisin.

Nisin, a bacteriocin produced by some strains of Lactococcus lactis, acts against foodborne pathogen Listeria monocytogenes. A single exposure of cells to nisin can generate nisin-resistant (Nisr) mutants, which may compromise the use of nisin in the food industry. The objective of this research was to compare the heat resistance of Nisr and wild type (WT) Listeria monocytogenes. The synergistic effect of heat-treatment (55 degrees C) and nisin (500 IU ml-1) on the Nisr cells and the WT L. monocytogenes Scott A was also studied. When the cells were grown in the absence of nisin, there was no significant (alpha = 0.05) difference in heat resistance between WT and Nisr cells of L. monocytogenes at 55, 60 and 65 degrees C. However, when the Nisr cells were grown in the presence of nisin, they were more sensitive to heat at 55 degrees C than the WT cells. The D-values at 55 degrees C were 2.88 and 2.77 min for Nisr ATCC 700301 and ATCC 700302, respectively, which was significantly (alpha = 0.05) lower than the D-value for WT, 3.72 min. When Nisr cells were subjected to a combined treatment of heat and nisin, there was approximately a four log reduction during the first 7 min of treatment.

Culture Media↗
PubMed1999

Effects of gene disruptions in the nisin gene cluster of Lactococcus lactis on nisin production and producer immunity.

The lantibiotic nisin is produced by several strains of Lactococcus lactis subsp. lactis. The chromosomally located gene cluster nisABTCIPRKFEG is required for biosynthesis, development of immunity, and regulation of gene expression. Inframe deletions in the nisB and nisT genes, and disruption of nisC by plasmid integration, eliminated nisin production and resulted in a strongly reduced level of immunity of the strains. The transcription of two nisin operons was inactivated in these mutant strains, but could be restored by addition of small amounts of nisin to growing cultures. The immunity levels of the mutants were also raised by adding nisin to growing cultures, albeit not to wild-type level. A strain with an in-frame deletion in the nisI gene was still able to produce active nisin, but the production and immunity levels were markedly lower. By measuring immunity levels of the knock-out strains and determining mRNA levels, it is concluded that NisI has an important function for nisin immunity and must cooperate with nisFEG-encoded proteins to provide a high level of immunity. Maximal immunity could not be obtained in the mutant strains, probably because the wild-type transcription levels from nisA and nisF promoters are not reached when essential nis genes are disrupted. Using Southern hybridization with a consensus promoter probe, no other DNA sequences similar to the nisA and nisF promoters could be detected, indicating that these two elements are probably the only ones in the chromosome regulated by nisin and are thus the only ones involved in the regulation of producer immunity.

Blotting, Northern↗
PubMed1999

Reduction of Listeria monocytogenes and Escherichia coli O157:H7 numbers on vacuum-packaged fresh beef treated with nisin or nisin combined with EDTA.

Nisin or nisin combined with EDTA was used to treat fresh beef. Beef cubes (2.5 by 2.5 by 2.5 cm) that were inoculated with approximately 7 log CFU/ml of Listeria monocytogenes Scott A or Escherichia coli O157:H7 505 B were dipped in the following solutions: (i) H2O, (ii) HCl, (iii) nisin, (iv) EDTA, or (v) nisin combined with EDTA, respectively, for 10 min each, with an exception of one set of control beef samples without treatment. Beef samples were then drip-dried for 15 min, vacuum packaged, and stored at 4 degrees C for up to 30 days. The pH on beef after different treatments was not a key factor in preventing bacterial growth. Treatment with nisin or with nisin combined with EDTA reduced the population of L. monocytogenes by 2.01 and 0.99 log CFU/cm2 as compared to the control, respectively, under the conditions of vacuum package and storage at 4 degrees C for up to 30 days. However, the effect of nisin and nisin combined with EDTA against E. coli O157:H7 505 B was marginal at 1.02 log CFU/cm2 and 0.8 log CFU/cm2 reductions, respectively.

Animals↗
PubMed1997

Nisin induces changes in membrane fatty acid composition of Listeria monocytogenes nisin-resistant strains at 10 degrees C and 30 degrees C.

Listeria monocytogenes isolates resistant to 10(5) IU ml-1 nisin were obtained at 30 degrees C (NR30) and at 10 degrees C (NR10). Nisin prolonged the lag phase of isolate NR30 at 10 degrees C. Isolates NR30 and NR10 did not produce a nisinase. Protoplasts of isolate NR30 were unaffected by exposure to nisin. The fatty acid composition from the wild-type strain and NR isolates was determined. As expected, temperature-induced differences in the C15/C17 fatty acid ratios were found. Growth of the NR strains in the presence of nisin resulted in significantly different C15/C17 ratios and a significant increase in the percentage of C16:0, C16: 1, C18:0 and C18: 1 fatty acids at 10 degrees C and 30 degrees C. Both the NR10 and NR30 isolates had similar growth rates at low temperatures, but these were slower than the wild-type strain. These results indicate that 'nisin resistance' is an environmentally defined phenotype and that nisin induces changes in the fatty acid composition of the membrane in L. monocytogenes nisin-resistant isolates regardless of the growth temperature.

Agar↗
PubMed1994

Influence of amino acid substitutions in the nisin leader peptide on biosynthesis and secretion of nisin by Lactococcus lactis.

Structural genes for small lanthionine-containing antimicrobial peptides, known as lantibiotics, encode N-terminal leader sequences which are not present in the mature peptide, but are cleaved off at some stage in the maturation process. Leader sequences of the different lantibiotics share a number of identical amino acid residues, but they are clearly different from sec-dependent protein export signal sequences. We studied the role of the leader sequence of the lantibiotic nisin, which is produced and secreted by Lactococcus lactis, by creating site-directed mutations at various positions in the leader peptide sequence. Mutations at Arg-1 and Ala-4, but not at the conserved Pro-2, strongly affected the processing of the leader sequence and resulted in the extracellular accumulation of a biologically inactive precursor peptide. Amino acid analysis and 1H NMR studies indicated that the precursor peptide with an Ala-4-->Asp mutation contained a modified nisin structural part with the (mutated) unmodified leader sequence still attached to it. The Ala-4-->Asp precursor peptide could be activated in vitro by enzymatic cleavage with trypsin, liberating nisin. These results confirmed that cleavage of the leader peptide is the last step in nisin maturation and is necessary to generate a biologically active peptide. Several mutations, i.e. Pro-2-->Gly,Pro-2-->Val, Asp-7-->Ala,Lys-9-->Leu,Ser-10-->Ala/Ser-12-->Ala and Val-11-->Asp/Val-13-->Glu in the leader peptide did not have any detectable effect on nisin production and secretion, although some of them affected highly conserved residues. When mutations were created in the -18 to -15 region of the nisin leader peptide (i.e. Phe-18-->Leu,Leu-16-->Lys,Asp-15-->Ala), no secretion or intracellular accumulation could be detected of nisin or its precursors. This suggested that these conserved residues are involved in the maturation process and may interact with lantibiotic-specific modifying enzymes.

Amino Acid Sequence↗
PubMed1996

Structure-activity relationships in the peptide antibiotic nisin: antibacterial activity of fragments of nisin.

The post-translationally modified peptide antibiotic nisin has been cleaved by a number of proteases and the fragments produced purified, characterised chemically, and assayed for activity in inhibiting the growth of Lactococcus lactis MG1614 and Micrococcus luteus NCDO8166. These results provide information on the importance of different parts of the nisin molecule for its growth-inhibition activity. Removal of the C-terminal five residues leads to approximately a 10-fold decrease in potency, while removal of a further nine residues, encompassing two of the lanthionine rings, leads to a 100-fold decrease. There are some differences between analogous fragments of nisin and subtilin, suggesting possible subtle differences in mode of action. Cleavage within, or removal of, lanthionine ring C essentially abolishes the activity of nisin. The fragment nisin1-12 is inactive itself, and specifically antagonises the growth-inhibitory action of nisin. These results are discussed in terms of current models for the mechanism of action of nisin.

Amino Acid Sequence↗
PubMed1991

Identification and characterization of the lantibiotic nisin Z, a natural nisin variant.

Lactococcus lactis strain NIZO 22186 produces an extracellular, lanthionine-containing 3.5-kDa polypeptide with antimicrobial activity. Its retention time on reversed-phase (RP) HPLC and its amino acid composition showed high similarities but no complete identity to nisin. The gene for this lantibiotic, designated nisZ, has been cloned and its nucleotide sequence was found to be identical to that of the precursor nisin gene apart from a single mutation resulting in the substitution His27Asn in the mature polypeptide. NMR studies of the natural nisin variant, which has been designated nisin Z, confirmed the His27Asn substitution and indicated that it has a similar structure to nisin.

Amino Acid Sequence↗
PubMed1996

Cell wall changes in nisin-resistant variants of Listeria innocua grown in the presence of high nisin concentrations.

Two nisin-resistant variants of a strain of Listeria innocua were isolated after growth in the presence of 500 and 4000 IU ml-1 of nisin A showed increased cell wall hydrophobicity, resistance to phage attack and three different cell wall-acting antibiotics, as well as to the peptidoglycan hydrolytic enzymes lysozyme and mutanolysin, as compared to the parental strain. Transmission electron microscopy revealed marked thickening of the wall of nisin-resistant cells with an irregular surface. Differences in thickness were lost after cell wall purification and no significant difference in gross wall composition was observed between the parental and resistant variants. Cell wall changes in nisin-resistant listeriae are attributed to abnormal cell wall synthesis and autolysin inhibition, the latter possibly associated with subtle changes in cell wall structures and function.

Anti-Bacterial Agents↗