NEW METABOLITES IN THE DEGRADATION OF FLUORENE BY ARTHROBACTER SP STRAIN F101

Identification of new metabolites and demonstration of key enzyme acti vities support and extend the pathways previously reported for fluoren e metabolism by Arthrobacter sp. strain F101. Washed-cell suspensions of strain F101 with fluorene accumulated 9-fluorenone, 4-hydroxy-9-flu orenone, 3-hydroxy-1-indanone, 1-indanone, 2-indanone, 3-(2-hydroxyphe nyl) propionate, and a compound tentatively identified as a formyl ind anone. Incubations with 2-indanone produced 3-isochromanone. The growt h yield with fluorene as a sole source of carbon and energy correspond ed to an assimilation of about 34% of fluorene carbon. About 7.4% was transformed into 9-fluorenol, 9-fluorenone, and 4-hydroxy-9-fluorenone . Crude extracts from fluorene-induced cells showed 3,4-dihydrocoumari n hydrolase and catechol 2,3 dioxygenase activities, These results and biodegradation experiments with the identified metabolites indicate t hat metabolism of fluorene by Arthrobacter sp, strain F101 proceeds th rough three independent pathways, Two productive routes are initiated by dioxygenation at positions 1,2 and 3,4, respectively, meta cleavage followed by an aldolase reaction and loss of C-1 yield the detected i ndanones, Subsequent biological Baeyer-Villiger reactions produce the aromatic lactones 3,4-dihydrocoumarin and 3-isochromanone. Enzymatic h ydrolysis of the former gives 3-(2-hydroxyphenyl) propionate, which co uld be a substrate for a beta oxidation cycle, to give salicylate. Fur ther oxidation of the latter via catechol and 2-hydroxymuconic semiald ehyde connects with the central metabolism, allowing the utilization o f all fluorene carbons, Identification of 4-hydroxy-9-fluorenone is co nsistent with an alternative pathway initiated by monooxygenation at C -9 to give 9-fluorenol and then 9-fluorenone, Although dioxygenation a t 3,4 positions of the ketone apparently occurs, this reaction fails t o furnish a subsequent productive oxidation of this compound.