In addition, an ontology analysis was done using DAVID (the Database for Annotation, Visualization and Integration Discovery) to identify over- or under-expressed ontology categories [17]. Putative changed categories were then checked manually. DAVID has proven to be useful for prokaryotes when compared with other ontology programs [18]. Energy metabolism P. gingivalis

is an asaccharolytic bacterium and cannot survive on glucose or carbohydrates alone. While some genes for carbohydrate metabolism are found in the genome, P. gingivalis derives its energy from the metabolism of amino acids [11, 13]. Takahashi and colleagues measured amino acid usage in selleckchem culture and found that glutamate/glutamine and aspartate/asparagine were preferentially metabolized [13]. When grown on dipeptides of these substrates, P. gingivalis produced different selleck amounts of metabolic byproducts. Importantly, aspartylaspartate produced significantly higher amounts selleck screening library of acetate, which is associated with ATP formation (Fig. 2 and Additional file 1: Table S1). Internalized P. gingivalis cells showed an increase in the energy pathway from aspartate/asparagine to acetate and energy (Fig. 2). The corollary of this trend is that

the intracellular environment is energy rich for P. gingivalis. Interestingly, the protein that converts glutamate, the other favored amino acid, to 2-oxoglutarate (PGN1367, glutamate dehydrogenase) showed a decrease in abundance (Fig. 2). This may represent a preference for energy production in internalized cells or be part of a more general shift in the metabolic byproducts. We also observed a decrease in protein abundance of maltodextrin phosphorolase (PGN0733). Maltodextrin phospholase plays a role in digesting starches and, despite being an asaccharolytic organism, P. gingivalis may make some use of the starches available Nabilone in the oral cavity, but restricts this activity after internalization. Figure 2 Metabolic Map of Energy and Cytotoxin Production. Proteins catalyzing each step are shown by their P. gingivalis PGN designation. Red up arrows indicate increased levels upon internalization,

green down arrows decreased levels, and yellow squares no statistical change. Acetyl-CoA appears as a substrate and product at multiple points and is shown in purple. Metabolites and metabolic precursors discussed in the text are shown in bold. Cytotoxic byproducts P. gingivalis metabolism produces several short chain fatty acid byproducts that are cytotoxic (Fig. 2) and has been found to shift production between these compounds depending on growth conditions [13]. We have found a general increase in the pathway from 2-oxoglutarate to the cytotoxin propionate while the proteins in the pathways for production of the cytotoxin butyrate showed unchanged or reduced expression (Fig. 2). This is consistent with hints that byproduct production shifts away from butyrate and towards propionate during P.