Defining essential genes and identifying virulence factors of Porphyromonas gingivalis by massively parallel sequencing of transposon libraries (Tn-seq).

Porphyromonas gingivalis is a keystone pathogen in the development and progression of periodontal disease. Obstacles to the development of saturated transposon libraries have previously limited transposon mutant-based screens as well as essential gene studies. We have developed a system for efficient transposon mutagenesis of P. gingivalis using a modified mariner transposon. Tn-seq is a technique that allows for quantitative assessment of individual mutants within a transposon mutant library by sequencing the transposon-genome junctions and then compiling mutant presence by mapping to a base genome. Using Tn-seq, it is possible to quickly define all the insertional mutants in a library and thus identify nonessential genes under the conditions in which the library was produced. Identification of fitness of individual mutants under specific conditions can be performed by exposing the library to selective pressures.