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Porphyromonas gingivalis is a Gram-negative anaerobe considered to be a keystone pathogen in the development of the bacterial-associated inflammatory oral disease chronic periodontitis. Although post-translational modifications (PTMs) of proteins are commonly found to modify protein function in eukaryotes and prokaryotes, PTMs such as lysine acetylation have not been examined in P. gingivalis. Lysine acetylation is the addition of an acetyl group to a lysine which removes this amino acid's positive charge and can induce changes in a protein's secondary structure and reactivity. A proteomics based approach combining immune-affinity enrichment with high sensitivity Orbitrap mass spectrometry identified 130 lysine acetylated peptides from 92 P. gingivalis proteins. The majority of these peptides (71) were attributed to 45 proteins with predicted metabolic activity; these proteins could be mapped to several P. gingivalis metabolic pathways where enzymes catalysing sequential reactions within the same pathway were often found acetylated. In particular, the catabolic pathways of complex anaerobic fermentation of amino acids to produce energy had 12 enzymes lysine acetylated. The results suggest that lysine acetylation may be an important mechanism in metabolic regulation in P. gingivalis, which is vital for P. gingivalis survival and adaptation of its metabolism throughout infection. Statement of significance. Porphyromonas gingivalis is a keystone pathogen in the development of chronic periodontitis, an inflammatory disease of the supporting tissues of the teeth. The ability of the pathogen to induce dysbiosis and disease is related to an array of specific virulence factors and metabolic regulation that enables the bacterium to proliferate in an inflamed periodontal pocket. The mechanisms P. gingivalis uses to adapt to a changing and hostile environment are poorly understood and here we show, for the first time, that enzymes of critical metabolic pathways for energy production in this bacterium were acetylated on certain lysine residues. These enzymes were often found catalysing sequential reactions within the same catabolic pathway. The results suggest that lysine acetylation is an important mechanism of metabolic regulation in P. gingivalis vital for its adaptation and proliferation to produce disease., (Copyright © 2015 Elsevier B.V. All rights reserved.)