The oviducts of two grivet monkeys and three marmosets, all sexually mature animals, were inoculated with Mycoplasma genitalium at laparotomy. The mycoplasma was not recovered from the grivet monkeys, nor from the oviducts of the marmosets although it was isolated intermittently from the vagina of two of the latter animals up to 4-6 weeks after inoculation. In contrast, all of the animals developed antibody to M. genitalium measured by a micro-immunofluorescence technique. It developed rapidly in the grivet monkeys but slowly in the marmosets, being detected first about 1 month after inoculation with a maximal response by 2 months. Furthermore, despite an absence of vaginal discharge or cytological response, all the animals developed a moderate to severe endosalpingitis characterized by the infiltration of acute inflammatory cells into the tubal epithelium, together with a lumenal exudate and adhesions between the mucosal folds. The changes are similar to those produced by Chlamydia trachomatis in simian models and naturally in women.

Species of the Acholeplasmataceae differ from species of the Mycoplasmataceae and Spiroplasmataceae in many respects, including lack of a nutritional requirement for sterol, ability of most species to synthesize saturated fatty acids and polyterpenes from acetate, and several other properties related to lipid metabolism and to the incorporation and location of lipids in the cell membrane. Acholeplasma species have also been found to differ from Mycoplasma species in possessing a nicotinamide adenine dinucleotide-dependent lactate dehydrogenase that is specifically activated by fructose 1,6-diphosphate and in containing superoxide dismutase, as well as glucose-6-phosphate and 6-phosphogluconate dehydrogenases. In addition, reduced nicotinamide adenine dinucleotide oxidase activity is located in the cell membrane of Acholeplasma species and is associated with the soluble cytoplasmic fraction of Mycoplasma and Spiroplasma species. Finally, significant differences exist between the nucleic acids of the Acholeplasmataceae and the Mycoplasmataceae. The genome molecular weight for Acholeplasma species is about 1.0 × 109, compared with about 5.0 × 108 for species of the Mycoplasmataceae. Moreover, a recent comparison of ribosomal ribonucleic acid oligonucleotide catalogs has demonstrated that Acholeplasma species are more closely related phylogenetically to two clostridial species than to the Mycoplasma and Spiroplasma species tested. Because the characteristics of species of the Acholeplasmataceae differ in major respects from those of other families of the Mollicutes, we propose elevation of the family Acholeplasmataceae to the rank of a new order, Acholeplasmatales. We provide a description of the proposed taxon, the second order of the class Mollicutes.

Antisera to 10 mycoplasma species of bovine origin were produced in 10 ponies and were distributed for evaluation in growth-inhibition tests at 6 laboratories in Australia, England, Denmark, France, and the United States. Except for a few failures with some antigens produced at the 6 laboratories, the antisera induced large zones of growth inhibition in homologous, but not heterologous, systems. These antisera may be useful as standard reagents for the identification of the bovine mycoplasmas.

Although known as a separate group of organisms since 1898, the isolation in 1937 of a human genital mycoplasma represented the first observation of the association of this group of organisms with humans, a discovery that provided the impetus for extensive investigations of the interactions of mycoplasmas with the human host. These studies showed that mycoplasmas were frequent inhabitants of the mucous membranes of the urogenital and upper respiratory tracts. In early studies of human mycoplasmas, they were not speciated but were assigned to this group of organisms almost exclusively on the basis of cultural characteristics. However, differentiation between groups of human genital and oral mycoplasmas based on cultural, morphologic, biochemical, and serologic properties was achieved in 1953. A few years later formal proposals for the establishment of three human species of Mycoplasma (including Mycoplasma hominis) were made, along with suggestions for a new classification and nomenclature of the mycoplasmas. Serologic, genetic, and other data clearly show that M. hominis does constitute a relatively heterogeneous group of organisms. However, although this heterogeneity has practical implications for identification of isolates of M. hominis and for demonstration of antibodies to M. hominis, further studies are necessary to justify formal recognition of a taxonomic subdivision of M. hominis into distinct serovars. Investigations of the role of M. hominis as a potential human pathogen date back to the very first years of its discovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Various experimental monkey models have been used for the study of mycoplasmal infections of the urogenital tract. Direct inoculation of Mycoplasma hominis and Ureaplasma urealyticum into the urethra of male monkeys resulted in successful reisolation of the organisms from the urethra without giving rise to signs of urethritis during the observation period. The organisms were inoculated into the posterior fornix of the vagina of female grivet monkeys. During the ten-week observation period, there was no clinical, histologic, or serologic evidence of lower genital tract infection. Inoculation of M. hominis and M. fermentans into the upper genital tract of grivet monkeys produced parametritis and salpingitis. It was concluded that grivet monkeys are apparently suitable for study of the pathogenicity of genital mycoplasms.

The ultrastructural aspects of the interaction of Mycoplasma gallisepticum with specific rabbit antibody have been studied. In particular, fixation conditions which allow the simultaneous preservation of cellular fine structure and membrane antigenicity have been established and applied in a procedure of indirect immunological labelling of the antibody‐coated organisms with ferritin conjugated sheep anti‐rabbit IgG. The advantages of working with agar embedded organisms in a multistep labelling procedure are discussed. In membrane fractions of M. gallisepticum , prepared by osmolysis and freeze‐thawing, only sealed membranes retained their antibody‐binding capacity. Electron microscopical examination of “break‐through” colanies from immune growth inhibition zones revealed that the majority of cells in these colonies were destroyed, sometimes limited only by a single‐layered membrane and without extracellular antibody coat. An exception from this was the presumedly young cells in the periphery of colonies and in microcolonies which appeared to be intact and had a heavy antibody layer surrounding the cells. Based on these characteristics, a possible sequence of events is suggested eventually leading to destruction of mycoplasma organisms in immune growth inhibition zones.

SUMMARY It is proposed that a second family be re-established within the Mycoplasmatales for those strains not requiring sterol. Following the nomenclature of Sabin, who first made this proposal, the sewage strains of Laidlaw and Elford are renamed Sapromyces laidlawii and assigned to a family Sapromycetaceae. The status of strains not requiring sterol is discussed, including that of sewage a and b. In the light of recent evidence the pig isolates, originally named Mycoplasma granularum, seem to belong to the genus Sapromyces. Recently described tissue-culture isolates, as yet unnamed, represent another species within the Sapromycetaceae. It is questionable whether the organisms classified as M. laidlawii var. inocuum deserve the status of a named variety of S. laidlawii.

ELECTRON microscopic studies of the contour length of DNA from a mycoplasma species, Mycoplasma hominis (H 39)1, have shown that the DNA in this organism is organized in a single circular chromosome, 262 microns long, corresponding to a molecular weight of 5.0 × 108 daltons. The genome size of bacterial DNA is only well known for a very few bacteria (genome sizes, 0.8–3.0 × 109 daltons)2, but the genomes in mycoplasmas may well be smaller that those of most or all bacteria. If all or most mycoplasmas were to have this same low chromosomal DNA content, the findings might be taken as a strong indication for their having a common phylogenetic origin as well as justifying the placing of mycoplasmas as a separate class of organisms3.

Domermuth , C. H. (Statens Seruminstitut, Copenhagen, Denmark), M. H. Nielsen, E. A. Freundt, and A. Birch-Andersen . Ultrastructure of Mycoplasma species. J. Bacteriol. 88: 727–744. 1964.—The ultrastructure of 19 strains (15 species) of Mycoplasmatales grown on solid medium was studied with the aid of an electron microscope. The cells possessed a triple-layered limiting membrane 75 to 100 A thick. This membrane appeared to be symmetrical in some strains and asymmetrical in others. An electron-dense material found in close contact with the cell surface was tentatively interpreted to be a capsular substance. Ribosomes and strands of nuclear material were observed in the cytoplasm of cells of all strains. Ribosomes observed in the JA strain of M. gallisepticum were frequently arranged in a regular geometric pattern of characteristic appearance. Dense inclusions sometimes limited by triple-layered membranes (possibly developing elementary bodies), as well as membrane-surrounded vesicles, were observed in the cytoplasm of cells of some strains.

Domermuth, C. H. (Statens Seruminstitut, Copenhagen, Denmark), M. Nielsen, E. A. Freundt, and A. Birch-Andersen . Gross morphology and ultrastructure of Mycoplasma gallisepticum . J. Bacteriol. 88: 1428–1432. 1964.—The ultrastructure and gross morphology of Mycoplasma gallisepticum strains JA and W were studied with an electron microscope. Intact specimens were grown on Parlodion membranes, fixed with formaldehyde, and studied in situ . Sectioned specimens were grown on agar and were prepared for study by conventional sectioning techniques. Grossly, single and multiple (as many as four) protrusions were frequently observed extending from the surface of cells of the W strain. Single short protrusions extended from many of the cells of strain JA. In sectioned material, rows of what appeared to be developing elementary bodies (as many as four) were observed in cells of strain W, whereas, single, apparently developing elementary bodies were observed in strain JA. In both strains, these bodies were located within the protruding areas of the cell wall. The inclusion-containing portions of the cell appeared to be the protrusions which extended from the surface of the intact cell.