Protein Analysis of Sapienic Acid-Treated Porphyromonas gingivalis Suggests Differential Regulation of Multiple Metabolic Pathways
ABSTRACTLipids endogenous to skin and mucosal surfaces exhibit potent antimicrobial activity againstPorphyromonas gingivalis, an important colonizer of the oral cavity implicated in periodontitis. Our previous work demonstrated the antimicrobial activity of the fatty acid sapienic acid (C16:1Δ6) againstP. gingivalisand found that sapienic acid treatment alters both protein and lipid composition from those in controls. In this study, we further examined whole-cell protein differences between sapienic acid-treated bacteria and untreated controls, and we utilized open-source functional association and annotation programs to explore potential mechanisms for the antimicrobial activity of sapienic acid. Our analyses indicated that sapienic acid treatment induces a unique stress response inP. gingivalisresulting in differential expression of proteins involved in a variety of metabolic pathways. This network of differentially regulated proteins was enriched in protein-protein interactions (P= 2.98 × 10−8), including six KEGG pathways (Pvalue ranges, 2.30 × 10−5to 0.05) and four Gene Ontology (GO) molecular functions (Pvalue ranges, 0.02 to 0.04), with multiple suggestive enriched relationships in KEGG pathways and GO molecular functions. Upregulated metabolic pathways suggest increases in energy production, lipid metabolism, iron acquisition and processing, and respiration. Combined with a suggested preferential metabolism of serine, which is necessary for fatty acid biosynthesis, these data support our previous findings that the site of sapienic acid antimicrobial activity is likely at the bacterial membrane.IMPORTANCEP. gingivalisis an important opportunistic pathogen implicated in periodontitis. Affecting nearly 50% of the population, periodontitis is treatable, but the resulting damage is irreversible and eventually progresses to tooth loss. There is a great need for natural products that can be used to treat and/or prevent the overgrowth of periodontal pathogens and increase oral health. Sapienic acid is endogenous to the oral cavity and is a potent antimicrobial agent, suggesting a potential therapeutic or prophylactic use for this fatty acid. This study examines the effects of sapienic acid treatment onP. gingivalisand highlights the membrane as the likely site of antimicrobial activity.