Appl. Environ. Microbiol., 03 1997, 819-826, Vol 63, No. 3
M Casellas, M Grifoll, JM Bayona and AM Solanas
Identification of new metabolites and demonstration of key enzyme
activities support and extend the pathways previously reported for fluorene
metabolism by Arthrobacter sp. strain F101. Washed-cell suspensions of
strain F101 with fluorene accumulated 9-fluorenone, 4-
hydroxy-9-fluorenone, 3-hydroxy-1-indanone, 1-indanone, 2-indanone, 3-
(2-hydroxyphenyl) propionate, and a compound tentatively identified as a
formyl indanone. Incubations with 2-indanone produced 3- isochromanone. The
growth yield with fluorene as a sole source of carbon and energy
corresponded 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-dihydrocoumarin hydrolase and catechol 2,3- dioxygenase activities.
These results and biodegradation experiments with the identified
metabolites indicate that metabolism of fluorene by Arthrobacter sp. strain
F101 proceeds through 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 indanones. Subsequent biological Baeyer-Villiger reactions produce
the aromatic lactones 3,4-dihydrocoumarin and 3-isochromanone. Enzymatic
hydrolysis of the former gives 3-(2-hydroxyphenyl) propionate, which could
be a substrate for a beta oxidation cycle, to give salicylate. Further
oxidation of the latter via catechol and 2-hydroxymuconic semialdehyde
connects with the central metabolism, allowing the utilization of all
fluorene carbons. Identification of 4-hydroxy-9-fluorenone is consistent
with an alternative pathway initiated by monooxygenation at C-9 to give
9-fluorenol and then 9-fluorenone. Although dioxygenation at 3,4 positions
of the ketone apparently occurs, this reaction fails to furnish a
subsequent productive oxidation of this compound.
Copyright © 1997, American Society for Microbiology
New metabolites in the degradation of fluorene by Arthrobacter sp. strain F101
Departament of Microbiologia, Universitat de Barcelona, Spain.
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