الفهرس 
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Abstract
Intensification of agriculture and increases in population pressure has reduced the structural stability of soil. To cope with low productivity, inorganic fertilizers have been intensively used. The large scale use of chemical fertilizers causes pollution of soil as well as soil problems including structural degradation, reduction of organic matter, soil colloidal content. Among fertilizers constituents, phosphorous is one of the major nutrients for plants. It is one of the major macronutrient for biological growth and development. It is a major component of DNA, RNA, ATP, ADP, ribosomes, microbial cell surfaces, and other cell materials. Phosphorous is vital to energy production and storage in a cell.
The majority of agricultural soils contain large reserves of phosphorous and despite the wide distribution of phosphorous in nature; it is a deficient nutrient in most soils, as a considerable part of it is accumulated as a consequence of regular applications of phosphatic fertilizers or because of mineral phase reprecipitation. The insoluble soil phosphate has low mobility and thus causes low phosphate concentration in soil solution, or low phosphate availability for the plant absorption. The soil available phosphates combined easily with Ca, Fe or Al to form Ca-P, Fe-P and Al-P complexes, which are the major constituents of soil inorganic phosphate.
Given the negative environmental impact of chemical fertilizers and their increasing costs, the use of microorganisms capable of solubilizing phosphate is advantageous for sustainable agriculture. Phosphate-solubilizing bacteria can convert fixed phosphates into the available forms, and thus plants can more effectively absorb phosphate. This process not only compensates for higher cost of manufacturing fertilizers in industry, but also mobilizes the fertilizers added to the soil. Therefore, the use of microorganisms as biofertilizers in agriculture has been a focus of research for a number of years.
AIM OF THE WORK
The proposed work seeks to isolate and exploit novel aerobic heterotrophic bacterial strains from different habitats, capable to convert insoluble phosphate into soluble forms. Further, selection of the most potent isolates and factors affecting solubilization process will be evaluated. Finally, the potential use of the bacterial isolate(s) in soil improvement will be demonstrated
PLAN OF WORK
1. Enrichment, isolation, and purification of phosphate solubilizing bacteria from different habitats
2. Selection of the most potent bacterial isolate(s)
3. Biochemical and physiological characterization of the selected isolate(s)
4. Optimization of culture conditions for improving phosphate solubilization
5. Exploring the potentiality of the selected strain(s) in biotechnological application
2. REVIEW OF LITERATURE
2
2. REVIEW OF LITERATURE
2.1. Phosphorus
Phosphorus (P) is one of the most abundant elements in cells. It is second only to nitrogen.