In vitro antibacterial activity of recombinant protein AtlM of Staphylococcal aureus

Objective To construct the recombinant protein AtlM （rAtlM） of Staphylococcal au- reus through prokaryotic expression system and to investigate its antibacterial activity in vitro. Methods The specific primers were designed according to atlM gene sequence of Staphylococcal aureus recorded in Gen- Bank, and atlM gene was amplified by PCR from the Staphylococcal aureus strain （ATCC25923）. The re- combinant plasmid pET-32a （＋）/atIM was constructed and transformed into Transetta （DE3） to express AtlM after induced by IPTG. The expressed protein AtlM was further analyzed by SDS-PAGE and purified by electroeluting of bag filter. The minimal inhibitory concentrations （MICs） of rAtlM to ATCC25923 and oxac- illin-resistant S. aureus strain were determined by the broth microdilution method. S. aureus ATCC25923 strain and oxacillin-resistant S. aureus strain （final concentration of 5×10^5 CFU/ml） were exposed to rAtlM （50 μg/ml） respectively to test its antibacterial activity in vitro. Results The recombinant protein AtlM was expressed and purified successfully with a relative molecular weight of 80×10^3 and a concentration of 1.25 mg/L. The MICs of rAtlM to ATCC25923 strain and oxacillin-resistant S. aureus strain were 8 μg/ml and 64μg/ml, respectively. In vitro test showed that rAtlM had inhibitory effects on the growth of ATCC25923 strain and oxacillin-resistant S. aureus strain after 1 h of intervention （P=0.004 and P=0.026, respectively）, which lasted to 5 h for ATCC25923 strain （P = 0. 012） and 3 h for oxacillin-resistant strain （P= 0. 001 ）. Conclusion This study shows that rAtlM has a certain antibacterial effects on S. aureus ATCC25923 strain and oxacillin-resistant S. aureus strain, suggesting a possibility of serving as antimicrobial agent. Key words: Staphylococcal aureus ;  Autolysin ;  Antimicrobial agent;  Gene expression