Abstract: Extracellular polymeric substances (EPSs) of a high efficient PAHs-degrading bacterium strain were extracted by four methods including cation exchange resin method, ultrasonic method, ultrasoniccation exchange resin method and heating method, and the properties of EPSs extracted by the four methods were analyzed by infrared spectrum, threedimensional fluorescence spectrum and transmission electron microscope. The maximum total content of protein and polysaccharide in EPSs by the heating method was 328.36 mg·L^-1. The adsorption peaks of C(N)═O, N―H (protein) and O―H (polysaccharides) were all present on the infrared spectrum of EPSs obtained by the four methods, and the peaks of C(N)═O and N―H on the spectra of EPSs extracted by the heating method were the widest and strongest. The threedimensional fluorescence spectrum analysis showed that the intensities of two proteinoid peaks in EPSs obtained by the heating method were maximum, being 13.8 and 118.2 a.u., respectively, while the proteinoid peak was weaker and the humiclike and fulviclike acids were stronger in EPSs obtained by the other three methods. Transmission electron microscopy analysis showed that the damage of bacterial cell was least and no intracellular substances dissolved out during the process of heating. According to the characteristics of the EPSs obtained by the four methods, the heating method was considered as the better EPS extraction method due to its highest efficiency and moderate impact on bacterial cell.

Key words: population structure, interspecific association, point pattern analysis