Variation in the Phosphate Solubilizing Bacteria from Virgin and the Agricultural Soils of Punjab

Bacteria with phosphorus (P) solubilization potential are considered vital in promoting bioavailability of phosphorus in soil. The present study was conducted to isolate and study the variation of phosphate solubilizing potential of bacteria isolated from virgin and agricultural soils. Total 30 isolates from virgin soil and 4 isolates from agricultural soil which retained their activity on repeated subculturing were selected. Among the isolates, there was insignificant difference in the total bacterial count from virgin and agricultural soils, however, a significant difference was found in the phosphate solubilizing bacteria (PSB) count and their P solubiling potential. Soil organic matter and available P content were correlated with PSB count. The mean solubilization index (SI) was higher from the isolates from virgin soils. Equal distribution method was employed to categorize the bacterial isolates into low, medium, and high P solubilizers which depicted H ≥ 89.44 and L ≤ 68. Among all the isolates, 23.53% were high P solubilizers (P-89.44-110.88 µg/ml), 55.88% were medium P solubilizers (P- 68-89.44 µg/ml), and 20.58% isolates produced low soluble P (46.56-68 µg/ml). Analysis of the data showed that all the isolates categorized under high P solubilizers belonged to the virgin soil. The isolates were characterized based upon biochemical characterization and belonged to Pseudomonadaceae, Enterobacteriaceae, Bacillaceae, Paenibacillaceae, Micrococcaceae, Burkholderiaceae, Flavobacteriaceae, and Streptococcaceae families. 16 sRNA sequencing of the two isolates showing maximum P solubilization were characterized as Enterobacter hormaechi. However, they differ appreciably in their P solubilization at different temperatures.