Potential of a novel endophytic diazotrophic Serratia sp. Wed4 for pyrene biodegradation

Endophytic diazotrophic Serratia sp. Wed4 with high nitrogenase activity (1260.9 +/- 8.3 nmol C2H4 mL(- 1)h(- 1)) was isolated from Glycine max Linn growing in PAH contaminated soil for improving PAH removal and crop growth. Strain Wed4 biodegraded 37.0% of pyrene within 14 d via phthalate pathway in vitro and could bio-degraded other PAHs with 2-5 rings effectively. Its capabilities on promoting crop growth included indole acetic acid (IAA) production (30.8 +/- 3.3 mu g mL(-1)), iron carrier production (A/Ar = 0.841 +/- 0.002), inorganic phosphate dissolution (D/d = 1.184 +/- 0.032) and organic phosphate dissolution (D/d = 1.154 +/- 0.025). Strain Wed4 successfully colonized in barley tissues (>10(4) CFU g(-1) FW), significantly promoted barley growth and nitrogen nutrition, reduced pyrene residues especially in shoots. Under sufficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 18.9%-33.9%, and decreased the pyrene residues by 46.4% in shoots and by 32.1% in roots. Meanwhile, under the deficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 40.1%-63.3% and decreased the pyrene residues by 39.0% in shoots and by 28.0% in roots. The pyrene contents were significantly negatively correlated with the total nitrogen contents in barley tissues, suggesting that nitrogen fixation of strain Wed4 also stimulated the pyrene removal. Based on its performance, Serratia sp. Wed4 provided a great potential to increasing crop yield and reducing PAH pollution in nitrogen deficient soils.