Isolation And Identification Of Organophosphate-dissolving Bacteria From Soil & Screening Of The Phosphate-dissolving Mutants

Phosphrus is an essential element for plant growth. Excessive phosphate fertilizer use has caused a lot of problems like resource waste and environment contamination. Nowadays more and more researhers focus on how to solve this problem through the bio-system in the plant root which relates closely to the phosphate cycle. Phosphate-dissolving microorgnism plays an important role in this bio-system.In this experiment, 7 strains of organophosphorous bacteria were isolated from the soil collected in rural areas of Beijing. Their physiological and biochemical features were studied and phylogenetic trees based on 16S rDNA sequences were analyzed. Our results showed that isolated S2, S3, X1 and He belong to the genus Pseudomonas, Y1 belongs to the genus Bacillus, H1 belongs to the genus Acinetobacter and H2 belongs to the genus Stenotrophomonas. According to the results of DNA-DNA hybridization, isolated S2, S3 and X1 were identified as Pseudomonas.alcaligenes and isolated Y1 was identified as Bacillus cereus.Isolated S2 was mutated by Tn5 transponson and 7 mutants with enlarged phosphate-dissolving ability and 1 mutant with no phosphate- dissolving ability were obtained from 2,500 exconjugants . Tn5 insertion in the S2 chromosome of the mutants were testified by PCR method. Phosphomolybdenum blue colorimetry was applied to measure the phosphate-dissolving ability of the mutants.