Characterization of phosphate solubilising and mineralizing bacteria from grain legumes
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Date
2016
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Punjab Agricultural University, Ludhiana
Abstract
The present study was conducted on characterization of phosphate solubilizing and mineralizing bacteria from grain legumes. Out of 62 bacterial isolates total 38 potential isolates of PSB formed clear halos around their colonies on NBRIP medium. Further, 13 putative isolates viz. PSB-1, PSB-2, PSB-8, PSB-18, LSBR-3, LSMR-1, LGR-33, RB-1, RB-3, RB-4, RB-5, RB-6 and RB-7 were identified with twin activities of P-solubilisation in Pikovskaya's(PVK) and mineralization in phytate screening agar media, respectively. Maximum phosphate solubilizing index (PSI) was recorded with PSB-18(1.90) and maximum phosphate mineralizing index (PMI) was recorded with PSB-18(4.01). Of 38 isolates of PSB, 10.5% and 89.5% were tested positive for organic acids with methyl red and Voges-Proskauer tests, respectively. Significantly high phytase enzyme activity was recorded with isolate RB-1(32.93 μg Pi/ml/hr) followed by PSB-18(31.37 μg Pi/ml/hr). Significantly high P-solubilisation along with pH drop at 9th day was noticed with isolate PSB-18 (41.49µgml-1 and 37.54µgml-1) followed by PSB-8(24.92µgml-1 and 21.52µgml-1) in PVK broth amended with tri calcium phosphate (TCP) and single super phosphate (SSP), respectively. Significantly high alkaline and acid phosphatase activities were observed for isolate of PSB-18 (283.86 and 297.38 µg p-nitrophenol/ml/hr) and (179.47 and 208.83 µg p-nitrophenol/ml/hr) with TCP and SSP as inorganic P source in PVK broth, respectively. Isolate PSB-18 exhibited significantly high P solubilisation (8.92 and 31.91 µgml-1) in high carbon and low nitrogen (HCLN) and low carbon and high nitrogen (LCHN) (7.56 and 30.86 µgml-1) amended with TCP and SSP, respectively in liquid MNBRI broth. There was significantly high production of IAA with isolate PSB-18 (46.14 and 4.68 μgml-1) followed by the isolate of PSB-8 (44.78 and 3.68µgml-1) in the presence as well as in the absence of tryptophan, respectively. Significantly high amount of GA production was observed in PSB-18(4.08 μgml-1) followed by PSB-8(3.93 μgml-1). All the 38 isolates of PSMB were positive for siderophore production on CAS agar medium. A highest intrinsic antibiotic resistance (IAR) spectrum was recorded with isolate RB-4 (87.5%). Maximum 63.2% resistance for antibiotic ampicillin @10 μg/disc was recorded with different PSMB isolate. On the basis of molecular characterization, of 13 potential isolates of PSMB 5 (PSB-1, PSB-2, RB-1, RB-4 and RB-5) were detected as Pseudomonas sp. with genus specific marker of band size 300 bp.
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Keywords
Microbiology, Phosphatase, Biochemistry, Phytase, Mineralization, Solubilization