Abstract: A strain PJ3 was isolated from soil, and identified as Arthrobacter sp. by 16S rDNA. Homology tree showed that the Arthrobactersp. PJ3 had the highest homology value with carbazole-degrading bacterium IC177, followed by with biphenyl-degrading bacteria K37 and R04. In order to evaluate the degradation capability of Arthrobacter sp. PJ3 to carbazole and biphenyl, the medium pH for Arthrobacter sp. PJ3 growth was optimized, and spectrophotometry was applied to measure the growth rate of the strain on the mineral medium with different concentration carbazole or biphenyl, and the degradation rate of the two aromatic compounds. The growth rate of the strain was the same at medium pH 7, 8, and 9, and higher than that at other medium pH values. At pH 7 and 0。1 mg·ml^-1of carbazole, the growth rate of the strain on CNFMM medium was the highest. After cultured for 15 days, the degradation rate of carbazole was up to 73%. At pH 7 and 0.5 mg·ml^-1 of biphenyl, the growth state of PJ3 on MSB medium was the best. When the PJ3 was cultured on MSB medium with 0.1 and 0.5 mg·ml^-1of biphenyl for 15 days, the degradation rate of biphenyl was 80%-85%. Therefore, 0.1-0.2 mg·ml^-1 of carbazole and 0.1-0.5 mg·ml^-1 of biphenyl could be the optimal concentrations for the degradation of the two aromatic compounds by Arthrobacter sp. PJ3.

Key words: Urban Forest, Structure and benefits, CITYgreen Model