Abstract: Through the high-throughput screening technique, a highly effective phenanthrene-degrading bacterium was screened and isolated from the oil sludge of the Shengli Oilfield, China. By means of 16S rDNA sequencing, the strain was identified asPseudarthrobacter phenanthrenivoransand named as A-5. Physiological responses of strain A-5 were investigated in the face of different levels of salt stresses (with 0, 1%, 3%, 5% and 7% NaCl added, respectively). The results showed that the strain A-5 exhibited a high degradation capacity of phenanthrene under salinities of less than 3%, with a weekly degradation rate of 95.45%, 91.20% and 79.54%, respectively. However, when added NaCl above 5%, its degradation efficiency decreased significantly to 2.98% and 1.56%, respectively. The growth rate of strain A-5 was gradually inhibited with the increase of LB medium salinity. When the ambient salinity increased, contents of saturated fatty acids in cell membrane of strain A-5 decreased, while the contents of unsaturated fatty acids and the intracellular ectoine increased.

Key words: oilfield, soil salinization, PAHs, growth curve, membrane fatty acids, ectoine