Rationally designed mariner vectors to allow functional genomic analysis of Actinobacillus pleuropneumoniae and other bacteria by transposon-directed insertion-site sequencing (TraDIS)

Transposon Directed Insertion Sequencing (TraDIS) is a high-throughput method for mapping insertion sites in large libraries of transposon mutants. The Himar1 (mariner) transposon is ideal for generating near-saturating mutant libraries, especially in AT-rich chromosomes, as the requirement for integration is a TA dinucleotide. In this study, we generated two novel mariner vectors, pTsodCPC9 and pTlacPC9 (differing only in the promoter driving expression of the transposase gene), in order to facilitate TraDIS identification of conditionally essential genes in Actinobacillus pleuropneumoniae and other bacteria. Using the pTlacPC9 vector, we have generated, for the first time, saturating mariner mutant libraries in both A. pleuropneumoniae and Pasteurella multocida that showed a near random distribution of insertions around the respective chromosomes. A preliminary screen of 5000 mutants each identified 8 and 15 genes, respectively, that are required for growth under anaerobic conditions.