In the course of screening for novel antimicrobial substances (antibiotics) from soil samples, antibiotic-producing actionmycete cultures were recorded from soil samples taken in Belgaum, Karnataka, India. As stated earlier, actinomycetes have provided many important bioactive compounds of high commercial value and continue to be routinely screened for new bioactive substances. In the present study, nine actinomycetes were isolated from soil samples with the aid of isolation media - soyabean-casein digest medium (SBCD), actinomycetes isolation agar (AIA) and starch-casein agar, having pinpoint colonies with zone of inhibition, cultured by crowded plate technique. Addition of CaCO3 and heat treatment aids the development of actinomycetes populations in the soil [3-7]. The presence of relatively large populations of actinomycetes in the soil samples of Belgaum indicates that it is a suitable ecosystem that promotes the isolation of actinomycetes during screening programmes.
It can be deduced from the results that the number of actinomycetes generally decreased with heavy rainfall which increases greatly the moisture content of soil. Furthermore, the growth of actinomycetes was favoured by neutral or slightly alkaline conditions. The fact that actinomycetes number was lower on the soil surface than 11-15 cm deep down into the soil may be attributed to the favourable combination of suitable pH and water content. The number of actinomycetes in black-alkaline sandy soil was very high.