The phylogenetic diversity of phosphate solubilizing bacteria (PSB) distributed in P-rich soils in the Dianchi Lake drainage area of China was characterized, and the tricalcium phosphate (TCP) solubilizing activities of isolated PSB were determined. Among 1328 bacteria isolated from 100 P-rich soil samples, 377 isolates (28.39% of the total) that exhibited TCP solubilization activity were taken as PSB. These PSB showed different abilities to solubilize TCP, with the concentrations of solubilized P in bacterial cultures varying from 33.48 to 69.63 mg L-1. A total of 123 PSB isolates, with relatively high TCP solubilization activity (> 54.00 mg L-1), were submitted for restriction fragment length polymorphism (RFLP) analysis, which revealed 32 unique RFLP patterns. Based on these patterns, 62 representative isolates, one to three from each RFLP pattern, were selected for 16S rRNA sequencing. Phylogenetic analysis placed the 123 PSB into three bacterial phyla, namely Proteobacteria, Actinobacteria and Firmicutes. Members of Proteobacteria were the dominant PSB, where 107 isolates represented by 26 RFLP patterns were associated with the genera of Burkholderia, Pseudomonas, Acinetobacter, Enterobacter, Pantoea, Serratia, Klebsiella, Leclercia, Raoultella and Cedecea. Firmicutes were the subdominant group, in which 13 isolates were affliated with the genera of Bacillus and Brevibacterium. The remaining 3 isolates were identified as three species of the genus Arthrobacter. This research extends the knowledge on PSB in P-rich soils and broadens the spectrum of PSB for the development of environmentally friendly biophosphate fertilizers.
