A novel rhizobacterium Bk7 for biological control of brown sheath rot of rice caused by Pseudomonas fuscovaginae and its mode of action
A bacterial strain (AD26) capable of utilizing atrazine as a sole nitrogen source for growth was isolated from an industrial wastewater sample by enrichment culture. The 16S rRNA gene sequencing identified AD26 as an Arthrobacter sp. PCR assays indicated that AD26 contained atrazine-degrading genes trzN and atzBC. The trzN gene of AD26 only differs from the trzN of Arthrobacter aurescens TC1 by one base (A-->T at 907) and one amino acid (Met-->Leu at 303). The specific activity of trzN of AD26 in crude atrazine-containing minimal media than two well characterized atrazine-degrading bacteria, Pseudomonas sp. ADP and Arthrobacter aurescens TC1. After incubating for 48 h at 30 degrees C, the OD(600) of AD26 reached 2.6 compared with 1.33 of ADP. AD26 was capable of degrading 500 mg/L of atrazine in minimal medium at 95% in 72 h, while the degradative rates by TC1 and ADP were only 90% and 86%, respectively. A bioremediation trial of contaminated soil has indicated that AD26 can degrade as high as 98% of atrazine contained in soil (300 mg/kg) after incubating for 20 d at 26 degrees C, nominating this strain as a good candidate for use in bioremediation programs.