Over 20 gram-positive bacteria were isolated by elective culture with (-+)-a-pinene as the sole carbon source. One of these strains, Nocardia sp. strain P18.3, was selected for detailed study. c-Pinene-grown cells oxidized, without lag, a-pinene, ot-pinene oxide (epoxide), and the cis and trans isomers of 2-methyl-5-isopropylhexa-2, 5-dienal (16,17) is indicative of the second ring cleavage occurring between carbon atoms 2 and 3 of the a.-pinene. In contrast, accumulation of the cis isomer of 2-methyl-5-isopropylhexa-2,5-dienoic acid by Pseudomonas putida PX1 (9, 10) and the trans isomer of the same compound by a mutant of P. putida PIN11 (19) is indicative of the second ring cleavage occurring between carbon atoms 3 and 4 (Fig. 1).With the exception of some whole cell oxidation studies and limited characterization of perillaldehyde and perillyl alcohol dehydrogenases from a-pinene-grown Pseudomonas sp. strain PL (2,16,17), the pathways proposed for cleavage of a-pinene have not been substantiated at the subcellular level.In a recent short communication (Floyd et al., EMBO Workshop) a strain of Pseudomonas fluorescens was reported to catalyze the NADH-linked oxygenation of a-pinene to form the epoxide (a-pinene oxide), and then cleavage of both rings of the epoxide by a decyclase with the formation of a novel aldehyde.