March 8, 2023, 10:30 - 11:00
Pneumococci colonize as harmless commensals the nasopharynx, while encountering as harmful pathogens the lungs, blood and CSF. By employing an in vivo pathoproteomics approach we recently identified pneumococcal antigens like ComDE and AliB essential for pneumococcal meningitis (Schmidt et al., 2019 PLoS Pathog 15: e1007987). Here, we deciphered the in vivo proteome and adaptation of pneumococci during colonization of mice. After intranasal infection with GFP-expressing S. pneumoniae serotype 19F pneumococci recovered from the nasopharynx were sorted by FACS. After tryptic on-filter digestion peptides were measured using LC-MS/MS in a data-independent acquisition mode (DIA) and generated data were analysed with the SpectronautTM software.
Approximately 1000 bacterial pneumococcal proteins were identified per sample. S. pneumoniae 19F showed host-compartment and media specific-proteome profiles as demonstrated by principal component analysis. In vivo colonization is associated with higher abundance of enzymes and adhesins and the higher abundance of fitness proteins is indicative of an optimized physiology for residing in the nasopharynx. Competence and cell wall synthesis are reduced during colonization as suggested e.g., by the lower abundance of cell division proteins. In conclusion, the selective pressure and availability of nutrients results in host-compartment specific protein expression to foster adaption and pneumococcal fitness.