Abstract: The present invention describes the development of a positive selection vector based on regulatory element modulation, wherein such modulation is achieved via insertional reconstruction or destruction of a regulatory element controlling transcription, translation, DNA replication and termination. A positive selection cloning vector pREM5Tc has been developed based on insertional reconstruction of a regulatory element of a reporter gene. The vector pREM5Tc carries the tetracycline resistance reporter gene with no functional −35 region of its promoter, a regulatory element, thus resulting in no expression of the tetracycline resistance gene. Hence a host cell carrying the vector pREM5Tc is unable to produce the tetracycline resistance gene protein resulting in inhibition of its growth in presence of tetracycline. An E.