Project description:Anaerobic bacteria in the oral cavity can cause respiratory infections. However, their precise mechanisms of action remain elusive. Unexpectedly, bacterial flora analysis using 16s rRNA revealed ‘hidden’ mixed infections of anaerobic bacteria and commensal oral Streptococcus species in community-acquired pneumonia. The purpose of this study is to elucidate the mechanisms by which Prevotella intermedia exacerbates oral streptococcal pneumonia.
Project description:Protein secretion into extracellular space is an important virulence mechanism both among Gram negative and Gram-positive bacteria. Prevotella intermedia, an important species associated with periodontitis, is known to be resistant to several antibiotics. Since P. intermedia is a part of normal oral microbiota, its complete elimination is not possible. Despite the remarkable clinical significance P. intermedia has, 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. Proteins in the secretome preparations were identified by nanoLC-ESI-MS/MS. 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. Proteins with predicted virulence potential were 39 in biofilm and 44 in planktonic secretomes, respectively. Gene ontology analysis revealed that the biofilm secretome displayed a markedly higher percent proteins compared to planktonic secretome in terms of cellular amino acid metabolic process, nitrogen compound metabolic process, protein binding and methyltransferase and kinase activities. In conclusion, this study revealed differences in the protein profiles of P. intermedia biofilm and planktonic secretomes. This may set a basis for asking further questions into molecular mechanisms how this species exerts its virulence potential in the oral cavity.
Project description:Prevotella intermedia is a Gram-negative bacterium belonging to the Bacteroidetes phylum and is notably linked to periodontitis. Several other species within this phylum have been reported to possess the general O-glycosylation system, and the O-glycoproteome has been well characterized in Tannerella forsythia, Porphyromonas gingivalis, and Flavobacterium johnsoniae. In this study, we used electron cryotomography (cryoET) to view the ultrastructure of P. intermedia for the first time, revealing an electron dense surface layer surrounding both cells and outer membrane vesicles (OMVs). Interestingly, the OMVs were frequently large (>200 nm) and were of two types, with the lumens being either electron dense or translucent. LC-MS/MS analyses of OMVs and various cell fractions of P. intermedia resulted in the identification of 1655 proteins including 62 predicted T9SS cargo proteins. Consistent with the presence of large OMVs with electron dense lumens, periplasmic proteins contributed to nearly half the protein content of OMVs. For the glycoproteome, 445 unique O-glycosylation sites within 226 glycoproteins were identified. The O-glycosylation motif exhibited a much broader range than reported in other species, with O-glycosylation found at D(S/T)(A/I/L/M/T/V/S/C/G/F/N/E/Q/D/P). A single major O-glycan was identified of delta mass 1531.48 Da and its sequence was determined by MS2 and MS3 analyses using a combination of CID and HCD fragmentation modes. Following partial deglycosylation with trifluoromethanesulfonic acid, the O-glycan sequence was confirmed to be dHex-dHex-HexNAc(HPO3-C6H12O5)-dHex-Hex-HexA-Hex(dHex). Bioinformatic analyses of O-glycoprotein localization predicted 73 periplasmic proteins, 53 inner membrane proteins, 52 lipoproteins, 26 outer membrane proteins, and 14 proteins secreted by the T9SS.
