The oral pathogen Porphyromonas gingivalis gains tolerance to the antimicrobial peptide DGL13K by synonymous mutations in hagA

• Published in: PloS one Vol. 19; no. 10; p. e0312200
• Main Authors: Gorr, Sven-Ulrik, Chen, Ruoqiong, Abrahante, Juan E., Joyce, Paul B. M.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 24.10.2024
• Subjects: Acid resistance; Amino acids; Animals; Antimicrobial agents; Antimicrobial peptides; Antimicrobial Peptides - genetics; Antimicrobial Peptides - pharmacology; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biofilms; Biology and Life Sciences; Dentistry; Drug resistance in microorganisms; Enzyme-linked immunosorbent assay; Gene expression; Gene mutations; Genetic aspects; Genetic testing; Genomes; Gingipain; Gram-negative bacteria; Gum disease; Hemagglutination; Hemoglobin; Medicine and Health Sciences; Microbial Sensitivity Tests; Microbiological research; Minimum inhibitory concentration; Mutants; Mutation; Oral cavity; Pathogens; Peptides; Periodontal disease; Periodontal diseases; Phenotypes; Physiological aspects; Porphyromonas gingivalis; Porphyromonas gingivalis - drug effects; Porphyromonas gingivalis - genetics; Porphyromonas gingivalis - pathogenicity; Protein folding; Protein structure; Research and Analysis Methods; Stereoisomerism; Stereoisomers; Virulence; United States; England; United Kingdom > UK; St Louis Missouri; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0312200

Porphyromonas gingivalis is a keystone pathogen for periodontal disease. The bacteria are black-pigmented and require heme for growth. P . gingivalis exhibit resistance to many antimicrobial peptides, which contributes to their success in the oral cavity. P . gingivalis W50 was resistant to the antimicrobial peptide LGL13K but susceptible to the all-D-amino acid stereoisomer, DGL13K. Upon prolonged exposure to DGL13K, a novel non-pigmented mutant was isolated. Exposure to the L-isomer, LGL13K, did not produce a non-pigmented mutant. The goal of this study was to characterize the genomic and cellular changes that led to the non-pigmented phenotype upon treatment with DGL13K. The non-pigmented mutant showed a low minimum inhibitory concentration and two-fold extended minimum duration for killing by DGL13K, consistent with tolerance to this peptide. The DGL13K-tolerant bacteria exhibited synonymous mutations in the hagA gene. The mutations did not prevent mRNA expression but were predicted to alter mRNA structure. The non-pigmented bacteria were deficient in hemagglutination and hemoglobin binding, suggesting that the HagA protein was not expressed. This was supported by whole cell enzyme-linked immunosorbent assay and gingipain activity assays, which suggested the absence of HagA but not of two closely related gingipains. In vivo virulence was similar for wild type and non-pigmented bacteria in the Galleria mellonella model. The results suggest that, unlike LGL13K, DGL13K can defeat multiple bacterial resistance mechanisms but bacteria can gain tolerance to DGL13K through mutations in the hagA gene.