Bacteriophages specific for Bacillus megaterium were isolated and were found to be common in soil of the Experimental Farm of Fac. Agric., Minia Univ., Egypt. A bacteriophage resistant mutant of B. megaterium was successfully isolated. The efficiency of the isolated mutant, free and immobilized cells of B. megaterium in dissolving insoluble phosphate and their susceptibility to phages were studied in pure liquid cultures (in vitro) and under cultivated soil conditions (in vivo).