Research Product

A fluorene-utilizing microorganism, identified as a species of Pseudomonas, was isolated from soil severely contaminated from creosote use, and was shown to accumulate six major metabolites from fluorene in washed cell incubations. Five of these products were identified as: 9-fluorenol, 9-fluorenone, (+)- 1, 1a-dihydroxy-1-hydro-9-fluorenone, 8-hydroxy-3,4-benzocoumarin and phthalic acid. This last compound was also identified in grown cultures supported by fluorene. Fluorene assimilation into cell biomass was estimated to be approximately 50%. The structures of accumulated products indicate that a previously undescribed pathway of fluorene catabolism is employed by Pseudomonas sp. F274. This pathway involves oxygenation of fluorene at C-9 to give 9-fluorenol, which is then dehydrogenated to the corresponding ketone, 9-fluorenone. Dioxygenase attack on 9-fluorenone adjacent to the carbonyl group gives an angular diol, 1,1a-dihydroxy-1-hydro-9-fluorenone. Identification of 8-hydroxy-3,4-benzocoumarin and phthalic acid suggests that the five-membered ring of the angular diol is opened first and the resulting 2'-carboxy-derivative of 2,3-dihydroxy-biphenyl is catabolized by reactions analogous to those of biphenyl degradation leading to the formation of phthalic acid. Cell extracts of fluorene-grown cells possessed high levels of an enzyme characteristic of phthalate catabolism, 4-5, dihydroxyphthalate decarboxylase, together with protocatechuate 4,5-dioxygenase. Based on these findings, a pathway of fluorene degradation is proposed to account for its conversion to intermediary metabolites. A range of compounds with structures similar to fluorene were acted on by fluorene-grown cells to give products consistent with the initial reactions proposed.