S U M M A R YThe guanine + cytosine (GC) base compositions of deoxyribonucleic acids (DNA) of avian mycoplasmas, as well as strains from other sources, were determined from buoyant density in CsCl. The values from our work ranged from 24.0 to 35-7 moles yo. There were small clusters at about 35 yo and 32 yo but the rest of the values ranged continuously from 24.0 yo to 30.5 yo. From reports in the literature, the values for the Mycoplasma group ranged from 22.8 to 41.0.
KELTON, WILLIAM H. (University of Massachusetts, Amherst). Synchronized division of avian pleuropneumonia-like organisms. J. Bacteriol. 83:948-955. 1962.-Evidence indicates that phosphate-buffered 0.85% saline (pH 7.0) is toxic when used for diluting cultures of pleuropneumonia-like organisms (PPLO). A technique for picking single PPLO colonies and streaking on agar medium is described. Growth curves of eight strains of PPLO of avian origin are described. Strain S-6 showed a typical growth curve. The other strains presented the lag and logarithmic phases of growth, followed by a rapid decline in viable numbers and peaks of growth later. Additional studies showed that growth was logarithmic in young cultures of all strains. Synchronization of division of two avian strains of PPLO appeared to have been induced by starvation for horse serum. Studies of small I This work was completed while the author was on assignment with H.
Kelton, William
H. (National Animal Disease Laboratory, Ames, Iowa). Storage of
Mycoplasma
strains. J. Bacteriol.
87:
588–592. 1964.—Survival of
Mycoplasma
strains (19 of avian origin, 3 human, 3 canine, and 1 saprophyte) in the lyophilized state and at various storage temperatures was studied. The effect of alternate freezing and thawing was also studied. All strains survived the freeze-drying process and at least 3 or 4 years of storage in the lyophilized state. At −26 C, they survived for at least 10 months, but changes were noted in colony size and growth rate of cultures stored longer than 10 months. At −65 C, however, there was little loss in viable numbers from 12 months of storage, and no changes in the organisms were apparent. There was considerable variation from strain to strain in resistance to alternate freezing and thawing. Of 16 strains tested, 13 withstood the freezing and thawing better than did the bacterium
Escherichia coli
. At 5 C, again, there was considerable variation in survival between strains. The saprophytic strain, C-15, showed no apparent loss after 9 weeks at 5 C. Most other strains showed rather rapid loss of viable numbers when stored at 5 C.
Sterigmatocystin was produced by 59% of
Aspergillus flavus
cultures and by 16% of
A. parasiticus
cultures. All sterigmatocystin-producing cultures of the
A. flavus
group also simultaneously produced aflatoxin or
O
-methylsterigmatocystin. Sterigmatocystin was produced by
A. chevalieri, A. ruber
, and
A. amstelodami
, species not previously reported to produce the compound. In 5-day-old chicken embryos, the no-effect level of toxicity of sterigmatocystin was between 1 and 2 μg/egg; the mean lethal dose was 5 to 7 μg; and 90 to 100% of the embryos were killed with 10 μg. Teratogenic effects and weight reduction were generally associated with nonlethal doses.
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