TRANSFORMATION OF AUXOTROPHS OF NEISSERIA MENINGITIDIS

Pyrimidine biosynthesis in Neisseria meningitidis. 1. Demonstration of enzyme activities

Activities of the five enzymes specific for the pyrimidine biosynthetic pathway, aspartate carbamoyl-transferase (ACTase), dihydroorotase (DHOase), dihydroorotate dehydrogenase (DHOdehase), orotate phosphoribosyltransferase (OMPppase), and orotidine 5'-phosphate decarboxylase (OMPdecase) were found in cell-free extracts of Neisseria meningitidis. Extracts also contained enzyme activities corresponding to the arginine pathway enzyme ornithine carbamoyltransferase (OCTase), and to carbamoylphosphate synthetase (CPSase), the enzyme common to both pathways. N. meningitidis possessed a single glutamine-dependent CPSase.

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.

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.

Stability of pathogenic colony types of Neisseria gonorrhoeae in liquid culture by using the parameters of colonial morphology and deoxyribonucleic acid transformation

This investigation describes the surveillance of the colonial stability of the pathogenic type 1 from the gonococcal strain F62 to the nonvirulent types 3 and 4 in different liquid media. The maintenance of the colony types was monitored by the parameters of colonial morphology and deoxyribonucleic acid-mediated transformation. During growth in a complex medium, Mueller-Hinton broth, only 46.7% of the gonococcal population remained as type 1 after 12 h. The greatest change in the type 1 colony-forming units correlated with the decline in viable count. The conversion process could not be prevented by the continual maintenance of the gonococcus in logarithmic growth. The frequency of transformation from PRO(minus) (proline) to PRO(plus) was proportional to this decrease in type 1 colony-forming units. In contrast to Mueller-Hinton medium, the chemically defined minimal medium Gonococcal Genetic Medium (GGM) was capable of maintaining approximately 90% of the gonococcal population in the type 1 colonial form after 16 h of growth, despite a decrease in the viable count. Although the percentage of type 1 appeared to remain constant in GGM, the apparent transformation frequency increased approximately 24-fold from 0 to 12 h of growth. GGM appears to stimulate or maintain competence, as evidenced by an eightfold increase in transformation when cells are exposed to deoxyribonucleic acid in GGM as compared to Mueller-Hinton.

Mutator factor in Neisseria meningitidis associated with increased sensitivity to ultraviolet light and defective transformation

A variant of Neisseria meningitidis was found to carry a mutator factor which endowed the bacteria with generalized genetic instability. The reversion frequencies of several biochemical mutants were increased up to 1,000-fold when the factor was introduced. The factor is not unidirectional in preference, since the mutator induced mutants generally reverted with increased frequency in its presence. There could be found no indication of insufficient synthesis of nucleic acid precursors. Attempts to demonstrate an unusual, mutagenic base incorporated in deoxyribonucleic acid (DNA) were negative. Strains carrying the mutator factor had significantly increased sensitivity to ultraviolet light. A mutation to a more ultraviolet-resistant type coincided with a disappearance of the mutator property. The presence of the mutator factor in a competent strain resulted in a reduction of the transformation frequency to between 0.5 and 5% of that in the parental strain. A mutation to the more ultraviolet-resistant type resulted in simultaneous loss of the mutator property and reestablishment of a normal transformation efficiency. It has been suggested that this mutator factor may represent a defect in the DNA repair mechanism, which is also of importance for genetic recombination. The mutator factor showed cotransformation with the locus for streptomycin resistance, but a true linkage could not be proved.

Genetic transformation of Neisseria gonorrhoeae to streptomycin resistance

Sparling, Philip F. (Communicable Disease Center, Atlanta, Ga.). Genetic transformation of Neisseria gonorrhoeae to streptomycin resistance. J. Bacteriol. 92:1364-1371. 1966.-Eight strains of Neisseria gonorrhoeae were transformed to streptomycin resistance by deoxyribonucleic acid (DNA) extracted from a streptomycin-resistant strain of N. gonorrhoeae. In all strains, competence was greatest in the naturally occurring, virulent clonal types 1 and 2, which gave transformation frequencies up to 1%. Clonal types 3 and 4, which arise on laboratory transfer and are avirulent, gave maximal transformation frequencies of 0.00005%. Competence was maximal in lag and early log phases of growth, but was maintained throughout the growth cycle. A complex broth was required for the physiological expression of competence. The kinetics of DNA uptake, dose-response curve of DNA versus transformants, time required for phenotypic expression, and other features were similar to those in other bacterial transformation systems.

Polarity of chromosome replication in Neisseria meningitidis

Jyssum, Kaare (University of Oslo, Oslo, Norway). Polarity of chromosome replication in Neisseria meningitidis. J. Bacteriol. 90:1182-1187. 1965.-Relative frequencies of various genetic markers in the deoxyribonucleic acid of Neisseria meningitidis in exponential- and stationary-growth phases were compared by use of a transformation system. On the basis of an analysis of eight genetic markers, including a competence factor, it is assumed that a polarity exists in the chromosome replication. A genetic map has been constructed according to the model of Yoshikawa and Sueoka. Chromosome replication has been compared in genetically competent and genetically incompetent strains. The change from genetic competence to genetic incompetence seems to result in a change in the replication of the chromosome. The results are discussed in relation to findings from other transformation systems, particularly that of Bacillus subtilis.