Integrational plasmids for the tetracycline-regulated expression of genes in Streptococcus pneumoniae

Plasmids for the tetracycline regulated gene expression in Streptococcus pn eumoniae have been developed. The plasmids were used for the tetracycline-d ependent production of firefly luciferase in streptococci. The production o f luciferase can be induced fivefold by the addition of tetracycline. By us ing two promoters of different strength and depending on the presence or ab sence of tetracycline, an 80-fold range of luciferase activities can be cov ered. The system was also used to construct strains that depend on the addi tion of tetracycline for the production of the A subunit of DNA gyrase, an essential streptococcal protein. The growth of such a strain depends on the addition of tetracycline to the medium. Tn the absence of tetracycline, th e cells cease to grow and are not viable. The system presented in this repo rt should be useful for the characterization of gene networks in S. pneumon iae. It especially allows one to study the function of essential genes that can not be investigated by standard knock-out techniques. (C) 1999 Elsevie r Science B.V. All rights reserved.