Distribution of catabolic pathways in some hydrocarbon-degrading bacteria from a subsurface polluted soil

Enrichment cultures on naphtha solvent were used to select aromatic hydroca rbon-degrading bacteria from a BTEX (benzene, toluene, ethylbenzene, xylene )-contaminated subsoil obtained from beneath a paint factory located in Mil an, Italy. Fifteen isolated strains were studied for their different biodeg radative capacities. Among these, 13 were able to grow on naphtha solvent. Ten were identified as Pseudomonas putida and three as Pseudomonas aureofac iens. Two other degraders were identified as Pseudomonas aeruginosa and Alc aligenes xylosoxidans subsp, denitrificans. Further molecular characterizat ion of the isolates was carried out by randomly amplified polymorphic DNA a nalysis to ascertain that all the studied strains belonged to different hap lotypes. The isolates were characterized for the presence of genes encoding for toluene dioxygenase, xylene monooxygenase and catechol 2,3-dioxygenase by polymerase chain reaction analysis and by Southern analysis. P, putida strain CM23, which showed homology with xylA,M, xylE and todC1C2BA genes, p ossessed multiple pathways which enabled the strain to grow on benzene, tol uene and m-xylene. (C) 2000 Editions scientifiques et medicales Elsevier SA S.