Figure 1: Exploitation of transposon sequencing libraries to identify P. gingivalis genes essential for fitness in multiple environments.

Highly saturated P. gingivalis TnSeq libraries have been used to identify genes that are conditionally essential for (A) murine abscess formation [14]; (B) epithelial colonization [14]; (C) survival of cigarette smoke toxins [28]; (D) black pigmentation [12]; and (E) maintenance of a functional T9SS [27]. High throughput sequencing allows for the identification and quantification of multiple transposon insertion sites simultaneously among a large mixture of mutants. Varying library generation and analytical methods have been employed, while the technology is rapidly evolving, e.g., [21, 79–81]. Generally, however, subtraction of the sequenced output library (non-essential mutants) from the larger input library (essential and non-essential mutants) allows elucidation of those individual strains that are required for survival under a specific condition of interest and, so, unable to propagate, are absent or under-represented in the output library. Herein, we focus particularly on those P. gingivalis protease-encoding genes that are essential in several disease-related environments, assigning high potential therapeutic value to communal environmental fitness determinant(s).