title: Isolation of conditional expression mutants in Mycobacterium tuberculosis by transposon mutagenesis.
abstract: In Mycobacterium tuberculosis identification of essential genes has been hampered by the scarcity of suitable genetic tools for genome wide screenings. We constructed two Himar1 transposon derivatives in which the Streptomyces pristinamycin I-inducible ptr promoter was inserted at one transposon end in outward orientation. These transposons, Tn-pip/pptr (which harbours the promoter and its repressor pip gene) and Tn-pptr (which depends on a host expressing the pip gene), were inserted in the thermosensitive mycobacteriophage phAE87. After transduction into M. tuberculosis H37Rv, hygromycin resistant clones were selected in the presence of pristinamycin, screened for inducer dependent growth, and the transposon insertion point mapped by sequencing. Out of 3530 Hyg(R) mutants tested, we obtained 14 (0.4%) single insertion conditional mutants. In three (leuA, mazE6, rne) pptr was located upstream of genes whose function had been assessed by experimental evidence, whereas in seven the transposon targeted genes (ftsK, glf, infB, metC, pyrD, secY, and tuf) whose function had been assigned by similarity with homologous genes and four ORFs of unknown function (Rv0883c, Rv1478, Rv2050 and Rv2204c). These results validate our mutagenesis system and provide previously unavailable conditional expression mutants in genes of known, putative and unknown functions for genetic and physiological studies.
authors.affiliation: Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy. francesca.forti@unimi.it
authors.forename: Francesca
authors.initials: F
authors.lastname: Forti
authors.forename: Veronica
authors.initials: V
authors.lastname: Mauri
authors.forename: Gianni
authors.initials: G
authors.lastname: Dehò
authors.forename: Daniela
authors.initials: D
authors.lastname: Ghisotti
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D016296:Mutagenesis / Q000187:drug effects / Q000235:genetics; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000302:isolation & purification; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification*; D025762:Pristinamycin / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D025762:Pristinamycin; C112817:TlyA protein, Mycobacterium tuberculosis