Physiological roles of pneumococcal peptidases

Pathogenicity and virulence of Streptococcus pneumoniae: Cutting to the chase on proteases

Bacterial proteases and peptidases are integral to cell physiology and stability, and their necessity in Streptococcus pneumoniae is no exception. Protein cleavage and processing mechanisms within the bacterial cell serve to ensure that the cell lives and functions in its commensal habitat and can respond to new environments presenting stressful conditions. For S. pneumoniae, the human nasopharynx is its natural habitat. In the context of virulence, movement of S. pneumoniae to the lungs, blood, or other sites can instigate responses by the bacteria that result in their proteases serving dual roles of self-protein processors and virulence factors of host protein targets.

Biological imaging of chemical bonds by stimulated Raman scattering microscopy

All molecules consist of chemical bonds, and much can be learned from mapping the spatiotemporal dynamics of these bonds. Since its invention a decade ago, stimulated Raman scattering (SRS) microscopy has become a powerful modality for imaging chemical bonds with high sensitivity, resolution, speed and specificity. We introduce the fundamentals of SRS microscopy and review innovations in SRS microscopes and imaging probes. We highlight examples of exciting biological applications, and share our vision for potential future breakthroughs for this technology.

Phosphonopeptide antibacterial agents related to alafosfalin: design, synthesis, and structure-activity relationships

Dipeptide variants of alafosfalin (L-alanyl-L-1-aminoethylphosphonic acid) with substantial differences in potency and antibacterial spectrum in vitro and in vivo have been synthesized. Certain dipeptides with alternatives to the L-alanyl residue had broader antibacterial spectra; activity against Pseudomonas aeruginosa was included. Some compounds had better in vivo activity than alafosfalin when introduced into infected rodents orally, but for the majority of the more active phosphonodipeptides, parenteral administration was more effective. Certain oligopeptides derived from the more active phosphonodipeptides possessed good in vitro activity against an extended range of organisms; they included Haemophilus influenzae, Streptococcus faecalis, and Streptococcus pneumoniae. The in vivo activity of some of these phosphono-oligopeptides was significantly greater than that of the parent dipeptide and correlated well with the in vitro results. This indicates that phosphono-oligopeptides exert part of their in vivo action directly, in addition to that arising from smaller peptides produced by peptidase cleavage.