A METHOD FOR THE SELECTIVE ISOLATION OF MICROTETRASPORA-GLAUCA AND RELATED 4-SPORED ACTINOMYCETES FROM SOIL

An effective plate culture method for the isolation and enumeration of four-spored actinomycetes belonging to the Microtetraspora glauca gro up of Thiemann et al. is described, in which a water suspension of a s oil sample given dry heat (110 degrees C, 1 h) is subjected to a treat ment with 0 degrees 05% benzethonium chloride (BC) and cultured on the new medium LSV-SE agar which is supplemented with kanamycin, norfloxa cin and nalidixic acid. The LSV-SE agar, based on a commercial lignin (dealkaline; 1 g l(-1)) as the major carbon source, specifically suppo rted adequate growth and good sporulation for the M. glauca-group spec ies, thus facilitating the detection and enumeration of this rare acti nomycete group in the sample. The addition of the antibacterial agents to the LSV-SE agar, as well as the dry heat and BC treatment, provide d a selective effect of reducing the non-filamentous bacteria and unde sirable actinomycetes associates occurring on the isolation plates. A total of 26 different natural samples were examined. From 18 samples ( 16 of field and forest soils, and two of stream and lake sediments), t he new method consistently achieved the selective isolation of the M. glauca group, which accounted for 2-27% of the total population recove red. Definite evidence of biological activity which degrades the grass lignocellulose was found in all of the 39 test M. glauca-group isolat es. Of these, 14, or 36%, possessed antimicrobial activity.