ISOLATION OF PROPANE-OXIDIZING RHODOCOCCI ON SELECTIVE MEDIA WITH ANTIBIOTICS

The antibiotic sensitivity of rhodococci growing on various media was studied. Under the conditions of induced propane monooxygenase activit y, rhodococci were found to drastically increase their resistance to g entiomycin, neomycin, oxacillin, erythromycin, and chloramphenicol and even more so to lincomycin, oleandomycin, and nalidixic acid. The ant ibiotic sensitivity of natural satellites of gas-oxidizing rhodococci (representatives of the genera Kocuria, Micrococcus, and Pseudomonas) was also investigated. An improved procedure for the isolation of prop ane-oxidizing rhodococci from natural bacterial associations was devel oped, which implies use of selective media with antibiotics. For ecolo gical studies, a selective medium with 20 mu g/ml chloramphenicol is p roposed as providing the highest recovery of gas-oxidizing rhodococci. For the isolation of pure cultures of propane-oxidizing rhodococci, t he medium should be supplemented with combinations of antibiotics, nam ely, lincomycin (90 mu g/ml) plus polymyxin (100 U/ml) or erythromycin (2.5 mu g/ml) plus nalidixic acid (20 mu g/ml). These media are chara cterized by selective indices as high as 85-98% (the ratios of the num ber of rhodococci isolated to the total number of isolated microorgani sms). These media can also be used for industrial cultivation of gas-o xidizing rhodococci under nonsterile conditions.