ISOLATION AND CHARACTERIZATION OF A 9-FLUORENONE-DEGRADING BACTERIAL STRAIN AND ITS ROLE IN SYNERGISTIC DEGRADATION OF FLUORENE BY A CONSORTIUM

Pseudomonas mendocina MC2, able to use 9-fluorenone but not fluorene a s its sole source of carbon and energy, was isolated. Identification o f metabolites in growth media and washed cell suspensions indicated th at strain MC2 metabolizes 9-fluorenone via angular dioxygenation of th e ketone, to give 1,1a-dihydroxy-1-hydro-9-fluorenone, followed by the opening of the five-membered ring and further degradation of the resu lting biphenyl derivative by reactions akin to those of biphenyl metab olism, which produce phthalate as an intermediate. The aim of this res earch was to study the biodegradation of fluorene by a co-culture of s train MC2 and Arthrobacter sp, strain F101, which grows on fluorene an d simultaneously transforms a fraction of the substrate to 9-fluorenon e, which accumulates as a dead-end product. Growing with 0.1 g fluoren e/L, Arthrobacter sp. strain F101 caused the total removal of this com pound from the cultures, but when this strain was grown with 1 g fluor ene/L, only 16% of the fluorene was used. The addition of 9-fluorenone to cultures growing on fluorene showed that 9-fluorenone inhibits flu orene degradation. Finally, when Pseudomonas mendocina MC2 and Arthrob acter sp, strain F101 were co-cultured with 1 g fluorene/L as a sole s ource of carbon and energy, the growth of the strains completely remov ed fluorene in 2 days. 9-Fluorenone did not accumulate and the carbon assimilation into cell biomass was estimated as approximately 46%.