[Relationship between ureolytic activity expression of Streptococcus salivarius urease genes ureIABCEFGD in Escherichia coli and nickel ions].

ABSTRACT

PURPOSE: To obtain the clone of Streptococcus salivarius 57.I urease genes ureIABCEFGD and investigate the relationship between ureolytic activity expression of this clone in Escherichia coli and nickel ions. METHODS: The target gene was cloned by polymerase chain reaction in 2 parts separately. Then, 2 plasmids were digested by specific restriction enzymes and ligated together. The obtained plasmids were subjected to nucleotide sequence analysis and transformed into E.coli TG-1. The recombinant E.coli was added without or with different level of NiCl2. The amount of ammonia generated by ureolytic activity of each sample was measured by Nessler's assay. SPSS 17.0 software package was used for correlation analysis. RESULTS: The clone of urease genes ureIABCEFGD was proved by sequence analysis and BLAST search. The amount of ammonia generated by the recombinant strain had a positive correlation with the level of NiCl2(r=0.9714,P<0.01). When the level of NiCl2 was 50 µmol/L, the amount of ammonia reached maximum and would have little variance despite the increase of NiCl2 level. CONCLUSIONS: Ureolytic activity expression of ureIABCEFGD has a positive correlation with the level of added NiCl2 not exceeding 50 µmol/L. The present clone can be used to further investigate the regulation of the ureolytic activity expression of Streptococcus salivarius urease gene. Supported by Natural Science Foundation of Shanghai Municipality(08ZR1416800) and Research Fund of Science and Technology Committee of Shanghai Municipality(11411950900).