EVIDENCE FOR THE EXISTENCE OF ACID-SENSITIVE ACTINOMYCETES IN SOIL

Abstract

A total of 1269 actinomycetes was isolated from 10 alkaline and 6 acid Canadian soils. One hundred and seven were unable to grow on a dilute glucose–asparagines–salts agar which had been adjusted to pH 6.2, but were able to grow when the pH was adjusted to 8.5. Additional tests of 24 of the isolates showed that the lowest pH's allowing growth ranged from 6.8 to 6.1, the actual value varying with the isolate and with the composition of the medium. These isolates required a higher pH for growth on all media tested than did a typical Streptomyces which was included in the study to serve as a control. None was as sensitive to acidity, however, as the alkaline-dependent Streptomyces caeruleus Baldacci.The 107 isolates were interpreted to represent no more than 14 distinct organisms and 6 of these bore aerial hyphae and spores in chains. Nine of the 14 were some shade of orange or purple and the remainder were some shade of blue. A blue, sporulating Streptomyces (PRL 1772) resembled closely S. caeruleus.Acid-sensitive actinomycetes were found in 9 of the 10 alkaline soils and in 1 of the 6 acid soils.Four samples of beach mud from an alkaline salt lake yielded but one species of Streptomyces and it was sensitive to acidity. Its tolerance to sodium chloride was but slightly greater than that of a Streptomyces judged to be conventional in its response to acidity.