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.