A method for bioinformatic analysis of transposon insertion sequencing (INSeQ) results for identification of microbial fitness determinants

Transposon insertion sequencing is a process whereby microbial fitness determinants can be identified on a genome-wide scale. This process uses high-throughput next generation sequencing to screen for changes in the composition of a pool of transposon mutants after exposure to selective conditions. One commonly used process for generating transposon insertion sequencing libraries is called INSeq that works with mutant pools produced using a modified Mariner transposon. Libraries produced using the INSeq process are sequenced on the Illumina platform. In this chapter, we describe our method for processing the raw Illumina sequencing reads, aligning the reads to a reference sequence to determine read counts, and using the online transposon insertion sequencing data analysis server, ESSENTIALS, to interpret the results.