A mycoplasma capable of producing polyarthritis in mice has been isolated from the liver of a mouse suffering from Tyzzer disease. It was designated as strain OK.
(1) Biological properties of strain OK.
Strain OK could grow well at 37°C under aerobic conditions in a culture medium containing the components of the basal PPLO medium of Morton, Smith and Leberman (Difco PPLO agar, dehydrated) and supplemented with 20ml of pooled horse serum per deciliter and 10ml of a 25% extract of fresh baker's yeast per deciliter.
After ten days' incubation the largest colonies of organisms grown on the agar medium were 1mm in diameter. The colonies remained colorless and transparent for 3 to 5 days after the incubation. They turned to be yellowish white and turbid thereafter.
Microscopic examination revealed large bodies scattered in the colonies. Upon phase-microscopic examination of the organism, it was found that there were several fine granules linked together with filaments in a tangled string in each small transparent capsule.
The organism fermented dextrose, maltose, and dextrin, but it was inactive against galactose and lactose. When 48-hour cultures were tested, the reduction of methylene blue was rapid and complete.
The colonies did not adsorb sheep erythrocytes, but produced β-hemolysis against these cells within 2 days. They did not reduce 2, 3, 5-triphenyl-tetrazolium chloride (TTC) under aerobic conditions.
(2) Pathogenicity of strain OK.
Intravenous inoculation into mice with 3×10^7CFU/ml of strain OK suspension in saline caused purulent polyarthritis in 7 to 10 days, but all the mice survived throughout the observation period.
The pathogenicity of the strain remained unchanged even after 60 subcultures, i.e., 2 years after the strain was isolated. Neither intranasal nor intraperitoneal inoculation caused such polyarthritis. After intranasal inoculation of 10 mice with the strain, periauricular depilation was noticed in 7 mice and pneumonia in 3 mice. After intravenous inoculation of 31 mice with the strain, pneumonia was seen in 11 mice, periauricular dipilation in 3 mice, and liver abscess in 1 mouse.
(3) Histopathological findings on polyarthritis caused by strain OK in mice.
Acute purulent polyarthritis was produced in 8 mice of the ten intravenously inoculated with the strain.
(4) Identification of strain OK.
Strain OK was considered to be a mycoplasma from its biological properties. It has been found by growth inhibition tests and gel diffusion tests that strain OK is serologically identical with Mycoplasma pulmonis.
It was indicated, however, that strain OK was similar to M. pulmonis and M. neurolyticum in sugar fermentation and similar to M. neurolyticum in Mb reduction tests.
In conclusion, strain OK was different from M. pulmonis in the pathogenicity for mice, since it was found to cause polyarthritis.

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The mode of nuclear separation and the accompanying behavior of mitochondria in budding yeast-like cells of the genus Candida were studied at the electron microscopical level.
In this fungus, the nucleus showed to separate in the fission manner analogous in nature to that reported in the genus Saccharomyces. In the process of bud formation, the dumbell-shaped nucleus migrated from the mother cell into the bud separates as if it were pulled apart. The nuclear separation occurred in a narrow neck region of the cytoplasm slightly inside a bud cell. Then one of the daughter nuclei withdrew into the mother cell. There was no evidence suggesting definitely that the nucleus might separate completely in the mother cell at the initial stage of bud formation, and that one of the two nuclei might migrate into the bud cell.
Some of the mitochondria migrated into the bud cell prior to the nuclear migration, and others were observed to be situated along the migrating nucleus or at the nuclear site where the separation had occurred. These configuration might indicate that mitochondria played an active role in the migration and separation of the nucleus during the process of bud formation.
The nucleoplasm of Candida was generally homogeneous, although less electron-dense areas sometimes were visible scattered within the nucleus. In the present study, therefore, the significance of chromosome- or chromatin-division during the process of bud formation remained to be clarified in future.

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Yeast-like cells (blastospores) of Candida albicans and C. stellatoidea present two types of cell wall formation in the process of cell growth. One type occurs in the bud formation, and the other in the germination. The present paper deals with the mechanism of these types of cell wall formation at the electron microscopical level.
Bud formation occurred mostly when the yeast-like cells were cultured on Sabouraud's agar medium. The bud wall was produced by extension of the whole layers of the mother cell wall. After the bud cell developed fully in size, as well as in contents, the septal wall was formed in it, first on the mother-cell side and then on the bud-cell side. It was characteristic of electron-dense granules to be seen associated with membranous structures around the newly formed septal wall. These results suggested some possible mechanism for the septal-wall formation.
The septal wall may be produced by the accumulation of structural substances activated by the aid of these granules observed, mitochondria, and other membranous structures. It may not be produced by an inward extension of the cell wall, nor by simple fission.
The germination of blastospores took place easily with a diversity of unknown environmental factors. After the outer wall ruptured in the germinating region, the inner most layer of the cell wall, which was thin and transparent in electron density, protruded to be thick, so that an intact wall might develop in the daughter cell.
In an elongated germ-tube, septal walls were observed. They
were similar in appearance to those
of mycelial fungi.
It is interesting to note that the same type of cells (blastospores) takes a different growth phase depending upon the kind of culture.

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Changes in ultrastructure during the germination of chlamydospores of Candida stellatoidea and C. albicans were studied by the electron microscope.
The germination could be seen when relatively immature chlamydospores were transferred to nutrient medium from chlamydospore-formation medium. The cell wall of the chlamydospore was composed of four major layers. The present observation revealed that the three outer layers had ruptured to form the germ pore, and that the fourth, or the innermost, layer of electron transparent material was continuous to the whole cell wall of the germ bulb.
This appearance was generally analogous to that of the blastospore of this fungus, that of the ascospore of Saccharomyces or Neurospora, and that of the aeciospore of Cronartium.
In the germination of the chlamydospore, most of the intracytoplasmic organelles (nucleus, mitochondria, endoplasmic reticulm, and vacuoles) migrated into the germ bulb. The chlamydospore itself became empty or occupied entirely with a large spongioid vacuole. This type of chlamydospores could not germinate any more.
On the other hand, the blastospore had an ability to perform germination a few successive times.
A chlamydospore which had advanced in maturation failed to germinate. In the chlamydospore, the electron-dense third layer of the cell wall was extremely thick and the fourth layer little visible.

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