Phosphate solubilization potentials of soil Acinetobacter strains |
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Authors: | Mehmet Ogut Fatih Er Nejdet Kandemir |
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Institution: | (1) Cumra Higher Educational College, Selcuk University, Cumra, Konya, Turkey;(2) Agricultural Faculty, Field Crops Department, Gaziosmanpasa University, Tokat, Turkey |
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Abstract: | Many phosphate solubilizing microorganisms (PSM) require external pyrroloquinoline quinone (PQQ) for strong phosphorus (P)
solubilization in vitro. The objective of this study was to isolate efficient and PQQ-independent PSM. A total of 21 PSM were
isolated from the rhizosphere soil of wheat and maize grown in the pots. Acinetobacter strains were the only PQQ-independent and most effective solubilizers of tricalcium phosphate containing agar. The mean P
dissolved in liquid cultures of Acinetobacter strains in a 5-day incubation ranged from 167 to 888 μg/ml P. The pH dropped to below 4.7 from 7.8 in six isolates, which
produced gluconic acid in concentrations ranging between 27.5 and 37.5 mM. There was a linear regression between soluble P
and gluconic acid concentrations in the bacterial cultures (P < 0.05; R
2 = 0.59). Inoculation with Acinetobacter sp. WR922 significantly (P < 0.05) increased wheat (Triticum aestivum L.) P content by 27% at 15 days after emergence (DAE) and dry matter by 15% at 30 DAE compared to the control. The plant
P content in inoculated plants at 30 DAE was linearly correlated with soluble P of the bacterial cultures (P < 0.05; R
2 = 0.69). Gluconic acid production directly affected phosphate solubilization in vitro, which in turn influenced plant P content
of inoculated plants in PQQ-independent P-solubilizing Acinetobacter strains. |
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