TheHAasegenewasisolatedfromStrep(VeterinaryCulture CollectionCenterofChina)﹒ EscherichiacoliDH5 α(LifeTechnologies,Rockville,MD)wasrou tinelyusedfortransformationandpr ﹒ E ﹒ coliJM109(Stratagene,LaJolla。CA)wasusedasthehoststrainforgeneexp ﹒ pBV220(Stratag ......