NEW PLASMIDS CARRYING ANTIBIOTIC-RESISTANCE CASSETTES

A series of new plasmid vectors is described that carry gene cassettes imparting resistance to the antibiotics chloramphenicol (Cm-R), kanam ycin (Km(R)), tetracycline (Tc-R) and spectinomycin/streptomycin (Sp/S m-R). The gene cassettes are symmetrically flanked by several restrict ion sites. In addition, several restriction sites that are normally fo und internal to the gene cassettes have been eliminated, thereby expan ding the number of restriction enzymes available to excise an intact a ntibiotic-resistance gene. The gene cassettes are carried by high-copy -number plasmids that confer ampicillin resistance (Ap(R)).