Shokubutsugaku Zasshi
Online ISSN : 2185-3835
Print ISSN : 0006-808X
ISSN-L : 0006-808X
Studies on the physiology of soil actinomycetes
Syûzo Masumoto
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1946 Volume 59 Issue 697-702 Pages 104-116


1. The optimum temperature for the growth of most soil actinomycetes is about 30°C with the minimum of 10°or below. The maximum temperature ranges between 36°and 55°, the same being between 41°and 45°for about one half of the examined strains.
2. There are two groups of actinomycetes with respect to their reaction to the pH of culture media; the one having its optimum of about 5.5 and the other, which comprises most soil forms, of about 7.4. The pH of culture medium is changed with the growth of actinomycetes. This decidedly influences the development of the aerial mycelium. In most species the development of the aerial mycelium is generally favored when the medium is inclined to slight alkalinity (pH 7.6 8.0), but reduced when the reaction becomes more alkaline or acid.
3. Glycerol and dextrose proved to be the best among the various carbon sources for growth, maltose the next and starch somewhat more inferior. Inulin makes a poor source in general. Saccharose, lactose and mannitol are well utilized by some actinomycetes, while by others they may be hardly utilized. Fructose, galactose and mannose are almost alike being far inferior to dextrose. Xylose, arabinose, sorbitol, dulcitol and glycol are of little value. Among the organic acids citric, succinic and acetic are rather good sources, fumaric and malic less available, and lactic, tartaric, glycolic and formic almost unavailable.
4. The examination of Ca-oxalate formation from various carbon compounds used in culture media showed the course of oxalate formation by some actinomycetes to be as follows:
Acetic acid→Glycolic acid→Glyoxalic acid→Formic acid→Oxalic acid
5. Almost all the“chromogenus”strains exhibit tyrosinase activity making the tyrosine-agar (glycerol 10g, asparagine 0.5g, tyrosine 0.5g, K2HPO4 0.5g, MgSO4 0.5g, dist. water 1000cc, agar 20g, pH7.2) black, but the“non-chromogenus” ones never show this activity. It is more reliable to divide actinomycetes into two groups, namely tyrosinase-positive and -negative groups, than to usual“chromogenus” and“non-chromogenus”species.
6. The original characters which are often lost or changed during cultivation are sometimes regained by“soil-passage”. This is especially true in some strains whose ability to form aerial mycelium or pigments has been reduced or lost.
7. Even among strains belonging to one species there are occasionally some showing variations in morphology as well as in physiological characters. This is most conspicuous in relation to the utilization of different carbon sources. The variants that arose through colonial dissociation while in culture often coincide in character with those isolated from soil and this fact seems to explain the occurrence of such variations taking place in nature.

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