Biomedical subjects

K Jyssum

Publications and source records attributed to K Jyssum.

At least 19 recordsLinked to original sources

PubMed1984

Inhibitory spectrum of bacteriocin-like agents from Neisseria meningitidis.

Bacteriocin-like agents from five strains of Neisseria meningitidis were active against other meningococci and some other Neisseria species. Meningococci belonging to the same serogroup or serotype could be subdivided into distinct bacteriocin types. Insensitivity to the inhibitory agents was observed more frequently among serologically groupable strains than among non-groupable. Strains belonging to serogroup B were more often insensitive to the inhibitors released by four of the donor strains (P201, P213, P241, 99/79) than other groupable strains. Insensitivity to the bacteriocin-like activity of the fifth donor strain (77/79A) seemed to be evenly distributed among strains of different groups. Strains of serotype 15 were more often insensitive to the five inhibitors than strains belonging to other types. Group B and type 15 are most frequently observed among strains isolated from clinical cases in Norway.

Bacteriocins↗

PubMed1984

Activity of bacteriocin-like agents from Neisseria meningitidis on strains isolated from patients and carriers.

Strains of Neisseria meningitidis isolated from patients were more often completely insensitive to five bacteriocin-like agents than carrier strains, but no particular bacteriocin type could be associated with patient strains. Two genetically distinct types of insensitivity could be separated by transformation. Insensitivity to four bactericidal agents (from the strains P201, P213, P241 and 99/79) was caused by one common genetic marker whereas insensitivity to a bacteriostatic agent (from the strain 77/79) was caused by another. Insensitivity to the bactericidal agents was more often found among strains belonging to serogroup B than among strains belonging to other groups. But group B strains from patients were more often insensitive than similar strains from carriers. Insensitivity to the bacteriostatic agent seemed evenly distributed among strains of various serogroups. All insensitive patient strains tested showed reduced binding/destruction of inhibitor, indicating that resistance and not tolerance is associated with patient strains.

Bacteriocins↗

PubMed1983

Expression of bacteriocin-like activity in batch cultures of Neisseria meningitidis and consequences for genetic recombination.

The bactericidal activity found in four strains of Neisseria meningitidis and the bacteriostatic effect observed in one were expressed in the exponential phase of batch cultures and continued during the stationary phase. The active material was stable for more than 50 hours in agar media. In mixed cultures a strain with inhibitory activity eradicated a sensitive strain, and dominated the culture in the latter part of the exponential phase. Recombination took place in mixed cultures when at least one of the strains had the genetic properties which determine competence in transformation. The presence of inhibitory activity increased the recombination frequency at least ten-fold. Genetic markers were introduced into a strain with inhibitory activity from sensitive strains of N. meningitidis and from N. cinerea.

Bacteriocins↗

PubMed1983

Influence of blood cells on the expression of bacteriocin-like activity in Neisseria meningitidis.

The inhibitors responsible for the bactericidal activity found in four strains of Neisseria meningitidis were strongly bound to or inactivated by blood cells. The bactericidal effects were specifically influenced by human cells of types O, A, B and AB. Cells from horse, sheep and rabbit had no significant effect. The bacteriostatic effect observed in one strain of N. meningitidis was more moderately reduced in the presence of animal cells as well as human cells. The effects of the blood cells were connected with pellets from lysates of the blood cells. The bacteriostatic effect was also moderately reduced in the presence of plasma, hemoglobin and methemoglobin regardless of origin, and to some extent of cytochrome C. CaCl2 slightly enhanced the bacteriostatic effect.

Animals↗

PubMed1982

Three types of growth inhibition among strains of Neisseria meningitidis isolated from patients in Norway.

A survey has been made of Neisseria meningitidis strains isolated from patients in order to determine the prevalence of diffusible growth inhibitory substances active against other meningococci. Three types of growth inhibitory activity could be distinguished. The first type was release in cultures of nearly all strains after treatment with chloroform vapour. This activity inhibited all meningococci tested, including the donor strains. The properties were similar to those of the non-specific growth inhibitors observed among most strains of N. gonorrhoeae. The second type was demonstrated in cultures from four strains among 215 strains tested and may be present in a fifth strain. Bactericidal activity with high strain specificity was spontaneously released from cultures of the four strains. This type of activity was found to fit the description of a bacteriocin. The third type of inhibition was observed in one strain among the 215 strains tested. Cultures of this strain spontaneously released bacteriostatic activity. Products from the strain could inhibit almost all meningococcal strains except the donor strain itself. This activity was not entirely blocked by bovine serum albumin; it was not abolished by pronase and it was not stopped by dialysis membranes with cut-off 12000.

Bacteriocins↗

PubMed1979

Metabolism of pyrimidine bases and nucleosides in Neisseria meningitidis.

In Neisseria meningitidis, uridine, deoxyuridine, cytosine, cytidine, or deoxycytidine could not be used by uracil-requiring mutants as pyrimidine sources. Consistent with these findings, only 5-fluorouracil of the different fluoropyrimidine bases and nucleosides showed any inhibitory effect on the growth of four prototrophic strains of N. meningitidis. Likewise, only radioactive uracil was readily incorporated into nucleic acids, whereas uptake of radioactive uridine, cytosine, or cytidine could not be demonstrated. Uracil was converted to uridine 5'-monophosphate by uracil phosphoribosyltransferase, whereas enzyme activities for conversion of cytosine or any of the nucleosides were not detectable in meningococcal extracts.

Cell-Free System↗

PubMed1976

Osmotically induced changes of cell spaces in Neisseria meningitidis competence variants.

The volume of the whole cell and the fraction of the intact cell bounded by the cytoplasmic membrane (protoplast volume) have been measured by dextran and 14C-sucrose exclusion spaces in Neisseria meningitidis competence variants. Increase in external osmotic pressure causes contraction of the protoplast volume. Increasing osmolality due to NaCl and MgCl2 also causes contraction of the volume of the whole cell, whereas increasing concentrations of sucrose cause little or no change in the whole cell volume. The experiments demonstrate a significant difference between competent (cp+) and incompetent (cp-) cells. The cp+ protoplast have a far higher capacity for swelling during decreasing osmolality, and for shrinkage during increasing osmolality. Comparison of spheroplasts obtained by autolysis as well as by the penicillin technique indicates that the average cp+ spheroplast is larger than the average cp- one. The significance of the difference in structure of cp+ and cp- protoplasts has been discussed.

Cell Wall↗

PubMed1976

Effects of exposure to high and low osmotic pressure upon Neisseria meningitidis transformation.

Transformation efficiency in competent variants of the Neisseria meningitidis Strain M1 increased more than three-fold after exposure of the recipient cells to approximately 35 atmospheres osmotic pressure for 20 min. Growth of the recipient cells at increased osmotic pressure contantly reduced the transformation efficiency. Exposure of the cells to hypotonic conditions reduced transformability significantly and attempts to restore transformability by means of supernatant solutions from competent cultures were unsuccessful. Incompetent variants of the Strain M1 could not be rendered competent by exposure to increased tonicity. The findings have been discussed in relation to the effects of tonicity variation on N. meningitidis competence variants.

DNA, Bacterial↗

PubMed1976

Separation of Neisseria meningitidis competence variants by sucrose gradient centrifugation.

Transformable (cp+) and non transformable (cp-) variants of the Neisseria meningitidis Strain M1 could be separated on the basis of their sedimentation velocity in sucrose gradients. The cp+ cells sedimented slightly more slowly than the cp- ones. This supports previous observations that the change from cp+ to cp- is followed by alterations in cell structures. In cp+ populations, the transformable fraction banded with the bulk of the cells in sucrose gradients, indicating that the density of the phenotypically competent cell is identical to the rest of the cp+ population.

Bacteriological Techniques↗

PubMed1975

Influence of osmotic pressure on transformable and non transformable variants of Neisseria meningitidis. 2. Growth and induction of autolysis.

The Neisseria meningitidis Strain M1 could grow in media made hypertonic with 0.7 M sucrose, but the growth rate was much reduced. The reduction was more pronounced in the competent (cp+) variant than in the incompetent (cp-) one. After exposure to increased osmotic pressure, growth was resumed after a pronounced lag which was regularly longer in the cp- variant. Cellular lysis took place during the lag. The lag could be shortened by the addition of MgCl2. N. meningitidis cells lysed slowly when suspended in various isotonic solutes, but rapid lysis was activated in exponential phase cells by exposure to hypotonic as well as to hypertonic conditions. This activation was more pronounced in the cp- variant than in the cp+ variant. In stationary phase cells there was very little activation of autolysis. The rate of autolysis was inhibited by MgCl2 and CaCl2 in low concentration. Osmotic fragility developed during autolysis in the presence of high concentrations of acetate or sucrose but not in the presence of high concentrations of NaCl or phosphate. MgCl2 increased the osmotic stabilization caused by acetate or sucrose, whereas CaCl2 in low concentration abolished the stabilizing effect of these solutes.

Acetates↗

PubMed1975

Influence of osmotic pressure on transformable and non transformable variants of Neisseria meningitidis. 3. Fragility of the cell membranes.

Penicillin spheroplasts from competent (cp+) and incompetent (cp-) variants of Neisseria meningitidis Strain M1 were equally fragile as determined by the osmotic strength necessary for stabilization. Exponential phase cells adapted to growth under increased osmotic pressure and suspended in acetate or phosphate became osmotically fragile within 2-4 hour when stabilized by sucrose plus MgCl2. Spheroplasts were formed during the succeeding 6-12 hours. Cells that were not adapted to growth at high tonicity but exposed to the stabilizing fluid under conditions leading to plasmolysis, developed osmotic fragility more rapidly, but at the same time lysis of the membranes was activated. Under these conditions, membrane lysis occurred far more rapidly in the cp-variant than in the cp+ variant. Membrane lysis was inhibited by MgCl2 and enhanced by CaCl2 in low concentration. The findings support the notion that osmotic stress in N. meningitidis activates membrane lysis as well as cell wall lysis, and that both activations are far more pronounced in the cp- variant. But the relative protection of the cp+ variant cannot be due to higher tensile strength of the membranes.

Acetates↗

PubMed1975

Purine metabolism in neisseria meningitidis. 4. Interconversion of purine ribonucleotides.

Radioactive hypoxanthine and adenine were readily incorporated into the nucleic acids (RNA + DNA) of the prototrophic strain M1 of Neisseria meningitidis with labelling of the purine bases adenine and guanine. Contrary to this, adenine was incorporated into the nucleic acids with labelling of adenine only in the purine mutant 6-1c which requires adenine and guanine for growth. Guanine was in both strains incorporated into the nucleic acids with labelling of the purine base guanine only. Crude meningococcal extracts from the prototrophic strain M1 and strain 6-1b requiring histidine, proline, adenine and guanine for growth (his pro A G) were found to have activities corresponding to adenylosuccinate synthetase (EC 6.3.4.4), adenylosuccinate lyase (EC 4.3.2.2.), inosine 5'-phosphate dehydrogenase (EC 1.2.1.14)) and guanosine 5'-phosphate synthetase (EC 6.3.5.2). This last enzyme was active also with (NH4)2SO4 as amino donor. No activity corresponding to guanosine 5'-phosphate reductase (EC 1.6.6.8) could be demonstrated in either strain. The findings show that the mutant strains 6-1b and 6-1c are both blocked between aminoimidiazolcarboxamide ribonucleotide (AICA-R) and inosine 5'-phosphate (IMP). Transformation experiments with mutants requiring adenine and guanine for growth indicate that the negative property of these mutants is due to a lesion in one genetic locus or at least in loci that are very closely linked.

Adenine↗

PubMed1974