Porphyromonas gingivalis genes conferring fitness in a tobacco‐rich environment

Abstract

Smokers are more likely than non‐smokers to harbour Porphyromonas gingivalis, they are more susceptible to destructive periodontal disease and smokers may, ultimately, benefit from tobacco‐specific preventive and treatment strategies. A Mariner transposon insertion library for P. gingivalis ATCC 33277 was exploited to define 256 genes as essential for P. gingivalis survival in a tobacco‐rich environment. Genes whose products play roles in protein transport and catabolism, nicotinamide processing, protection against oxidative stress, drug resistance, and transcriptional regulation have all been identified as essential for CSE survival. Many of these tobacco‐essential genes are also requisite for epithelial colonization and abscess formation, suggestive of a core stress‐related P. gingivalis genome. Single‐gene deletions in several of the TnSeq‐implicated genes led to significantly reduced P. gingivalis fitness upon competition with the parent strain, under conditions of cigarette smoke extract‐induced stress (1,000 ng/ml nicotine equivalents). This study identifies, for the first time, a subset of P. gingivalis genes required for surviving the plethora of insults present in cigarette smoke. Such conditionally essential genes may delineate bacterial persistence strategies and represent novel therapeutic foci for the prevention of P. gingivalis infection and related diseases in smokers and in general.

The Type IX Secretion System and Its Role in Bacterial Function and Pathogenesis

“… A-LPS, A-lipopolysaccharide; GlcNAc, N-acetyl-D-glucosamine; OM, outer membrane; T9SS, Type IX Secretion System; +, essential; —, not essential. a Found to be inherently essential in at least 1 of 3 transposon sequencing studies (Klein et al 2012; Hutcherson et al 2016; Miller et al 2017). b Found to be conditionally essential and required under defined conditions: epithelial colonization (E), murine abscess formation (M), and cigarette smoke extract exposure (C) (Miller et al 2017; Hutcherson et al 2020). c Codes for a protein that is both a T9SS component and a cargo protein. d No sequence detected in transposon sequencing output pool of 1 to 2 conditions tested for fitness. …”

“… b Found to be conditionally essential and required under defined conditions: epithelial colonization (E), murine abscess formation (M), and cigarette smoke extract exposure (C) (Miller et al 2017; Hutcherson et al 2020). …”

“…Transposon sequencing (TnSeq) technology has enabled the genome-wide determination of P. gingivalis essential genes for growth and fitness. These strategies have compared the populations of saturated transposon mutagenized genes before and after planktonic growth in rich medium (Klein et al 2012; Hutcherson et al 2016), after colonization of oral epithelial cells (TIGK), after infection in a murine abscess model (Miller et al 2017), or after exposure to cigarette smoke extract (Hutcherson et al 2020). Essential genes for growth are “inherently essential” and cannot be considered for assessment for fitness in defined environments that are “conditionally essential.” The Table summarizes the P. gingivalis TnSeq data for T9SS-related genes that are inherently essential or required for fitness under 3 conditions.…”

“…a Found to be inherently essential in at least 1 of 3 transposon sequencing studies (Klein et al 2012;Hutcherson et al 2016;Miller et al 2017). b Found to be conditionally essential and required under defined conditions: epithelial colonization (E), murine abscess formation (M), and cigarette smoke extract exposure (C) (Miller et al 2017;Hutcherson et al 2020).…”

Tobacco smoke exacerbates Filifactor alocis pathogenicity

“…While there has been extensive delineation concerning how tobacco smoke influences Porphyromonas gingivalis gene activity, ultrastructure, and physiology (Bagaitkar et al, 2009(Bagaitkar et al, , 2010(Bagaitkar et al, , 2011Hutcherson et al, 2020;Miller & Scott, 2021), there are obvious fundamental differences between this established Gram-negative pathogen and F. alocis, not least architecturally. The role of F. alocis and, indeed, Gram-positive bacteria in general are not well studied, mechanistically, in the context of periodontal diseases.…”