Electroporation of Mycobacteria

The study of mycobacterial genomes has exploded during the last 10 yr. Initially, no systems were available for the du-ect manipulation of mycobacterial genes in mycobactena, so Escherichia coli was used as the primary cloning host. Several genomic libraries were created (1 –5 ) in E. coli . Although these proved useful for the ldentification of many protein antigens (6 ), the use of E coli as a cloning host has several limitations. It is now known that many mycobacterial promoters do not function at all in E. coli ; therefore, it is difficult to study the expression and control of mycobacterial genes in such a host. In addition, certain posttranslational modifications of proteins do not take place in E. coli and therefore the antigenicity and properties of proteins expressed in E coli may differ (7 –9 ).