2 NEW MYCOBACTERIUM STRAINS AND THEIR ROLE IN TOLUENE DEGRADATION IN A CONTAMINATED STREAM

Two toluene-degrading strains, T103 and T104, were isolated from rock surface biomass in a freshwater stream contaminated with toluene, The strains exhibit different capacities for degradation of toluene and ot her aromatic compounds and have characteristics of the genus Mycobacte rium. Both are aerobic, rod-shaped, gram-positive, nonmotile, and acid -alcohol fast and produce yellow pigments. They have mainly straight-c hain saturated and monounsaturated fatty acids with 10 to 20 carbon at oms and large amounts of tuberculostearic acid that are typical of myc obacteria. Fatty acid analyses indicate that T103 and T104 are differe nt mycobacterial strains that are related at the subspecies level. The ir identical 16S rDNA sequences are most similar to Mycobacterium auru m and Mycobacterium komossense, and they constitute a new species of f ast-growing mycobacteria. Ecological studies reveal that toluene conta mination has enriched for toluene-degrading bacteria in the epilithic microbial community. Strains T103 and T104 play only a small role in t oluene degradation in the stream, although they are present in the hab itat and can degrade toluene. Other microorganisms are consequently im plicated in the biodegradation.