Partial Reassociation Between the Deoxyribonucleic Acids of Neisseria lactamicus and Neisseria meningitidis.

The similarity in polynucleotide sequence of seven strains of Neisseria lactamicus to N. meningitidis and to each other was investigated. The per cent reassociation between single-stranded N. lactamicus deoxyribonucleic acid (DNA), immobilized on membrane filters, with labeled single-stranded DNA fragments derived from strain SD-6 (group C) of N. meningitidis varied from 75 to 56. With strain ATCC 23972 of N. lactamicus furnishing the labeled DNA fragments, reassociation was 72% with N. meningitidis, 31% with N. subflava, and 98 to 72% with the other strains of N. lactamicus. It is concluded that on the basis of DNA reassociation N. lactamicus can be distinguished from N. meningitidis and N. subflava, but constitutes a relatively heterogeneous species.

Deoxyribonucleic Acid Heterogeneity Between Human and Murine Strains of Chlamydia trachomatis.

We compared the polynucleotide sequence relationships of three strains of Chlamydia trachomatis of human origin (MRC-1/G, TW-3, and Lgv), one of murine origin (MoPn), and the MN strain of C. psittaci. The four strains of C. trachomatis have the same base ratio, about 42.5 moles per cent guanine plus cytosine, which is significantly higher than the base ratio of MN (39.5). Single strands of deoxyribonucleic acid (DNA) fragments of MRC-1/G reassociated with immobilized DNA of TW-3 and Lgv almost as well as with the homologous DNA. The duplexes produced in these reactions were about equally thermostable. On the other hand, reassociations between MRC-1/G and MoPn involved 60 or 30% of the DNA, depending on the stringency of the conditions for reassociation, and the duplexes were thermolabile. MoPn reassociated only to a very small degree with MN. We also compared glucose catabolism of MRC-1/G, MoPn, and MN under several sets of conditions. These tests failed to reveal any qualitative phenotypic differences among the three strains. It can be concluded that, judging by polynucleotide sequence, the three human strains of C. trachomatis are closely related but appreciably different from a murine strain.

Lipid synthesis by isolated Chlamydia psittaci.

The isolated cells of the host-dependent meningopneumonitis agent, Chlamydia psittaci, were shown to incorporate radioactive carbon from aspartate, isoleucine, and glucose-6-phosphate into cell lipids. The nature of this incorporation was investigated. Radioactivity was found only in the fatty acids and primarily in the phosphatidyl ethanolamine, and, to a lesser extent, in the phosphatidyl choline fractions. Branched-chain fatty acids, not found in host lipid, were shown to constitute a large proportion of the fatty acid content of phosphatidyl ethanolamine. The reasons why only fatty acid synthesis took place under the conditions of our experiments with isolated meningopneumonitis agent cells remain obscure.

Role of exogenous adenosine triphosphate in catabolic and synthetic activities of Chlamydia psittaci.

The synthetic activities of isolated cells of the meningopneumonitis strain (MN) of Chlamydia psittaci were investigated and further observations were made on their catabolic reactions. These observations included the demonstration of CO(2) production from aspartate in the presence of pyruvate and the formation of pyruvate from glucose-6-phosphate. Both reactions were enhanced by added adenosine triphosphate (ATP). Of a large number of compounds tested, only glucose-6-phosphate, pyruvate, aspartate, and isoleucine were shown to furnish carbons that were incorporated into molecules precipitated by trichloroacetic acid. The reactions with pyruvate, aspartate, and isoleucine were dependent entirely, or almost entirely, on added ATP, and the reaction with glucose-6-phosphate was enhanced by ATP. Except for CO(2), which greatly stimulated the reactions, the addition of a number of other compounds or a combination of compounds, such as cofactors, amino acids, and purine and pyrimidine bases, did not greatly affect incorporation. About 95% of the activity of the trichloroacetic acid precipitates was recovered in the chloroform-methanol soluble fraction.