Proteomic analysis of the periodontal pathogen Prevotella intermedia secretomes in biofilm and planktonic lifestyles.

Prevotella intermedia is an important species associated with periodontitis. Despite the remarkable clinical significance, little is known about the molecular basis for its virulence. The aim of this study was to characterize the secretome of P. intermedia in biofilm and planktonic life mode. The biofilm secretome showed 109 proteins while the planktonic secretome showed 136 proteins. The biofilm and the planktonic secretomes contained 17 and 33 signal-peptide bearing proteins, 13 and 18 lipoproteins, respectively. Superoxide reductase, sensor histidine kinase, C40 family peptidase, elongation factor Tu, threonine synthase etc. were unique to biofilm. Of the ~ 30 proteins with predicted virulence potential from biofilm and planktonic secretomes, only 6 were common between the two groups, implying large differences between biofilm and planktonic modes of P. intermedia. From Gene Ontology biofilm secretome displayed a markedly higher percent proteins compared to planktonic secretome in terms of cellular amino acid metabolic process, nitrogen compound metabolic process etc. Inflammatory cytokine profile analysis revealed that only the biofilm secretome, not the planktonic one, induced important cytokines such as MIP-1α/MIP-1β, IL-1β, and IL-8. In conclusion, the revealed differences in the protein profiles of P. intermedia biofilm and planktonic secretomes may trigger further questions about molecular mechanisms how this species exerts its virulence potential in the oral cavity.