EVIDENCE FOR A NOVEL PATHWAY IN THE DEGRADATION OF FLUORENE BY PSEUDOMONAS SP STRAIN F274

A fluorene-utilizing microorganism, identified as a species of Pseudom onas, was isolated from soil severely contaminated from creosote use a nd was shown to accumulate six major metabolites from fluorene in wash ed-cell incubations. Five of these products were identified as 9-fluor enol, 9-fluorenone, (+)-1,1a-dihydroxy-1-hydro-9-fluorenone, 8-hydroxy -3,4-benzocoumarin, and phthalic acid. This last compound was also ide ntified in growing cultures supported by fluorene. Fluorene assimilati on into cell biomass was estimated to be approximately 50%. The struct ures of accumulated products indicate that a previously undescribed pa thway of fluorene catabolism is employed by Pseudomonas sp. strain F27 4. This pathway involves oxygenation of fluorene at C-9 to give 9-fluo renol, which is then dehydrogenated to the corresponding ketone, 9-flu orenone. Dioxygenase attack on 9-fluorenone adjacent to the carbonyl g roup gives an angular diol, 1,1a-dihydroxy-1-hydro-9-fluorenone. Ident ification of 8-hydroxy-3,4-benzocoumarin and phthalic acid suggests th at the five-membered ring of the angular diol is opened first and that the resulting 2'-carboxy derivative of 2,3-dihydroxy-biphenyl is cata bolized by reactions analogous to those of biphenyl degradation, leadi ng to the formation of phthalic acid. Cell extracts of fluorene-grown cells possessed high levels of an enzyme characteristic of phthalate c atabolism, 4,5-dihydroxyphthalate decarboxylase, together with protoca techuate 4,5-dioxygenase. On the basis of these findings, a pathway of fluorene degradation is proposed to account for its conversion to int ermediary metabolites. A range of compounds with structures similar to that of fluorene was acted on by fluorene-grown cells to give product s consistent with the initial reactions proposed.