A total of 23 phosphate solubilizing bacteria (PSB) and 35 phosphate solubilizing fungi (PSF) were isolated from 19 samples of salt affected soils. The ability of 12 selected PSB and PSF to grow and solubilize tricalcium phosphate in the presence of different concentrations of NaCl was examined. Among 12 PSB, Aerococcus sp. strain PSBCRG1-1 recorded the highest (12.15) log viable cell count at 0.4 M NaCl concentration after 7 days after incubation (DAI) and the lowest log cell count (1.39) was recorded by Pseudomonas aeruginosa strain PSBI3-1 at 2.0 M NaCl concentration after 24 h of incubation. Highest mycelial dry weight irrespective of NaCl concentrations was recorded by the Aspergillus terreus strain PSFCRG2-1 (0.567 g). The percent P i release, in general, was found to increase with increase in NaCl concentration up to 0.8 M for bacterial solubilization and declined thereafter. At 15 DAI, strain Aerococcus sp. strain PSBCRG1-1 irrespective of NaCl concentrations showed the maximum P-solubilization (12.12%) which was significantly superior over all other isolates. The amount of P i released in general among PSF was found to decrease with increase in NaCl concentration at all the incubation periods. Aspergillus sp. strain PSFNRH-2 (20.81%) recorded the maximum P i release irrespective of the NaCl concentrations and was significantly superior over all other PSF at 7 DAI.
Combined inoculation of Rhizobium and 'Phosphate-solubilizing' Pseudomonas striata or Bacillus polymyxa with and without added chemical fertilizer on chickpea yield and nutrient content was studied under greenhouse conditions. While the single inoculation of Rhizobium increased the nodulation and nitrogenase activity, the 'phosphate-solubilizers' increased the available phosphorus content of the soil. Combined inoculation of Rhizobium and P. striata or B. polymyxa increased the above parameters and also the dry matter content, the grain yield and nitrogen and phosphorus uptake significantly over the uninoculated control. The inoculation effects were more pronounced in the presence of added fertilizers. The possibilities of saving half the dose of N and replacing superphosphate with rockphosphate and inoculation with 'phosphate-solubilizers' are discussed.
Indigenous phosphate-solubilizing microorganisms (PSM) were studied in the rhizosphere and nonrhizosphere of salt-affected soils. A total of 23 phosphatesolubilizing bacteria (PSB) and 35 phosphate-solubilizing fungi (PSF) were isolated from 19 samples collected from different locations in Karnataka and Madhya Pradesh of India. The counts of PSB and PSF showed large variations. The bacterial isolates were identified using BIOLOG as belonging to Pseudomonas, Xanthomonas, Bacillus, Aerococcus, Alteromonas, Erwinia and Enterobacter. Fungal isolates were identified as Aspergillus and Penicillium based on colony morphology, microscopic observations and BIOLOG. All the PSB and PSF isolates were able to produce both indole acetic acid (IAA) and gibberellic acid (GA). Bacterial isolates produced IAA in the range of 0.74 to 9.53 μg 25 ml −1 , and GA ranged from 2.08 to 12.55 μg 25 ml −1 . The amount of IAA produced by the PSF isolates ranged from 2.33 to 8.69 μg 25 ml −1 , and GA ranged from 3.44 to 14.80 μg 25 ml −1 . Fungal isolates were superior to bacterial isolates in terms of P solubilization as measured by release of inorganic phosphate (Pi) from tricalcium phosphate, increase in stem girth, root length, root dry matter and total dry matter of sorghum plants.
Spentwash is one of the most complex and cumbersome wastewater with very high BOD, COD and other organic and inorganic toxic constituents. It is dark brown colored and diffi cult to treat by normal biological process such as activated sludge or anaerobic lagooning. The color is due to the presence of melanoidins, caramels and other polymers. These compounds have anti oxidant properties which render them toxic to microorganisms. Spentwash disposal into the environment is hazardous and has a considerable pollution potential. It affects the aesthetic merit. Its decolorization by physical or chemical methods have been investigated and were found unsuitable. In the recent past, increasing attention has been directed towards utilizing microbial activity for decolorization of spentwash. This review reveals various groups of microorganisms which have potential in spentwash decolorization. The role of enzymes in decolorization and the microbial degradation of individual compounds imparting color to spentwash are also discussed.
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