Isolation and Characterization of a Halotolerant, Hydrocarbon-Degrading Endophytic Bacterium from Halobiotic Reeds (Phragmites australis) Growing in Petroleum-Contaminated Soils

Seventeen strains of hydrocarbon-degrading endophytic bacteria were isolated from reeds (Phragmites australis) that were growing on petroleum-contaminated saline soils in the Yellow River Delta, China. Among them, an isolate showed high activity for degrading diesel oil. Based on 16S rRNA sequences analysis and biochemical characteristics, the strain was identified as Pseudomonas stutzeri Z11. P. stutzeri Z11 grew in LB broths supplemented with 0–100 g/L NaCl, which indicated its strong salt-tolerant ability. In a mineral salts (MS) liquid medium supplemented with 3 different concentrations of NaCl (20, 60 and 100 g/L), the curve of diesel oil degradation by P. stutzeri Z11 was consistent with the first-order reaction, with the degradation rate constants as 0.1568, 0.1655 and 0.0742 d^{– 1}, respectively. P. stutzeri Z11 was capable of degrading diesel n-alkanes (n-C11 to n-C28) and the degradation rate of short-chain n-alkanes (n-C11 to n-C23) was higher than that of long-chain n-alkanes (n-C24 to n-C28). In mineral salts medium with 60 g/L NaCl, degradation rate of total n-alkanes by strain Z11 reached 79.5%. These characterizations of hydrocarbon-degrading endophytic strain Z11 presented here have important implications for the application of phytoremediation in petroleum-polluted saline soils.