Urease producing bacteria can precipitate calcite nano-crystals by producing urease in the presence of urea and calcium. Calcite precipitation resulting from microbial activity is a process that causes cementation of soil particles in nature. The purpose of this study was to isolate urease producing halophilic bacteria in order to precipitate of calcite in saline soil. Natural samples including soil and saline waters were selected for this purpose. At first, halophilic bacteria were isolated on the salt containing TSA medium, then, a selective medium containing phenol red and urea permitted the isolation of urease producing bacteria. Hydrolysis of urea by urease causes alkalization of the medium and formation of pink halo around colonies. The best isolate was selected for further study by measuring the release of ammonium using the Nessler method. The ability of calcite production was investigated on precipitation medium with different salt concentration for 10 days. A total of 110 halophilic strains were isolated, from which 58 isolates had the ability of urease production. The microscopic studies of colonies showed that only 5 isolates were able to produce crystals on precipitation medium. The calcite and the properties of the strains were further analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) detector. The XRD studies showed that the size of these particles in the range of 40-60 nm. The results revealed that all the isolates were able to produce calcite in the precipitation medium. Strain 3 showed the most amount of calcite production on precipitation medium containing 5% salt in compression with other strains. This strain also produced calcite precipitate on precipitation medium containing 15% salt. Studies on strain 6 also showed that these strains can also produce calcite precipitate on a precipitation medium containing 10% salt. These strains were identified by biochemical and molecular analysis. The 16s rRNA gene sequence of the strains 1, 3, 4 and 5 showed the most similarity with Staphylococcus saprophyticus and strain 6 with Staphylococcus xylosus. Phylogenetic analysis indicated that these isolates are about 99-100 % similar to Staphylococcus saprophyticus and Staphylococcus xylosus. Their 16S rRNA sequences were deposited in GenBank under the accession numbers of MG655151, MG655152, MG655153, MG655154 and MG655155, respectively. Today, many efforts have been made to produce environmental friendly cements and therefore, use of urease producing halophilic or halotolerant bacteria is an appropriate candidate for bio-cementing in saline environments.

 Asparagine is a nutritional requirement of both normal and tumor cells. Unlike normal cells, certain leukemic cells cannot synthesize asparagine and must consequently rely on an external supply in the plasma and tissues. L-Asparaginase belongs to a group of homologous amidohydrolases family, that catalyses the hydrolysis of the aminoacid L-asparagine to L-aspartate and ammonia So this enzyme has been widely used as effective therapeutic agent against acute lymphoblastic leukemia and lymphosarcoma.The aim of this study was isolation of L-asparaginase producing microorganisms from environmental samples. e.g. soil, different parts of plants, bird feces and water. After culturing on diffretial medium containing l-asparagine and phenol red for 1 days, 70 strains had a purple halo zone around the colony. Ten isolates showed high potential level of l-asparaginase activity. Three strains selected for identification and enzyme activity study on different carbons and nitrogen sources and pH. These isolates were identified as Serratia marcescens 100, Delftia tsuruhatensis 104 and Entrobacter sp. 105 by biochemical properties and analysis of 16S rRNA sequences. The optimal conditions for l-asparaginase production by Serratia marcescen 100 were; 24 hrs incubation period; 1.5 % (w/v) maltose as carbon source ; 1 % (w/v) ammonium sulfate as the nitrogen source and pH 7. The optimal conditions for l-asparaginase production by Delftia tsuruhatensis 104 were; 24 hrs incubation period; 1 % (w/v) glucose as carbon source; 1.5 % (w/v) yeast extract as the nitrogen source and pH 7. These conditions for Entrobacter sp. 105 were; 1.5 % (w/v) starch as carbon source; 1.5 % (w/v) ammonium sulfate as the nitrogen source and pH 6. L-asparaginase specific activity were determined for these strains at the best their conditions, that were as following: 8.92, 9.921 and 9.42 U/ mg of protein, respectively, This study showed that Serratia marcescens 100 and Delftia tsuruhatensis 104 did not exhibit measurable glutaminase activity.