Effect of Carbon Substrates on Rock Phosphate Solubilization by Bacteria from Composts and Macrofauna |
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Authors: | B Hameeda Y Harish Kumar Reddy OP Rupela GN Kumar Gopal Reddy |
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Institution: | (1) Department of Microbiology, Osmania University, Hyderabad, 500 007, AP, India;(2) International Crops Research Institute for Semi-Arid Tropics (ICRISAT), Patancheru, 502 324, AP, India;(3) Department of Biochemistry, M S University of Baroda, Vadodara, 390 002, India |
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Abstract: | Five of the 207 isolates from different composts, farm waste compost (FWC), rice straw compost (RSC), Gliricidia vermicompost (GVC), and macrofauna, showed rock phosphate (RP) solubilization in buffered medium in plate culture. When tested
in RP broth medium, all five strains, Enterobacter cloacae EB 27, Serratia marcescens EB 67, Serratia sp. EB 75, Pseudomonas sp. CDB 35, and Pseudomonas sp. BWB 21, showed gluconic acid production and solubilized RP. Based on cellulose-degrading and P-solubilizing ability,
two strains were selected for further studies. In the presence of different carbon sources, both strains showed a drop in
pH and solubilized RP. P released was maximum with glucose (1212 and 522 μmol) and minimum with cellobiose (455 and 306 μmol)
by S. marcescens EB 67 and Pseudomonas sp. CDB 35, respectively. Glucose dehydrogenase (GDH) activity was 63 and 77% with galactose and 35 and 46% with cellobiose
when compared to glucose (100%) by EB 67 and CDB 35, respectively. Both strains solubilized RP in the presence of different
crop residues. EB 67 and CDB 35 showed maximum cellulase activity (0.027 units) in the presence of rice straw and a mixture
of rice straw and root. P solubilized from RP in the presence of pigeonpea root was 134 and 140 μmol with EB 67 and CDB 35.
Significantly, these bacteria isolated from composts and macrofauna solubilized rock phosphate in the presence of various
pure carbon substrates and crop residues and their importance in soil/rhizosphere conditions is discussed. |
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