An Activatable Long-Fluorescence-Lifetime Probe for Exploring the Dual Function of StrH in Biofilm Formation and Necroptosis.

Abstract

Streptococcus pneumoniae infections, particularly those associated with biofilm formation, pose significant therapeutic challenges due to their increased resistance to antibiotics and immune evasion. Identifying new biomarkers is crucial for accurate diagnosis and the development of innovative treatment strategies. StrH is recognized as a key enzyme in S. pneumoniae carbohydrate metabolism, however, its specific role in biofilm formation and its interactions with the host remain poorly understood. In this study, a highly sensitive and selective turn-on long-lifetime fluorescence probe, "HBT-PXZ-St," is designed to detect StrH activity and to reveal its functions. Using fluorescence lifetime imaging microscopy (FLIM), "HBT-PXZ-St" can quantify StrH activity and image live S. pneumoniae cells, achieving a fluorescence lifetime of ≈2 µs, which effectively minimizes background short-lived fluorescence interference. Additionally, the findings suggest that StrH activity significantly contributes to biofilm development and induces necroptosis in A549 host cells via the receptor-interacting serine/threonine-protein kinase 1 (RIPK1) pathway, thereby promoting bacterial colonization and invasion. This study provides insight into StrH's dual role as both a "sword and shield" during colonization and invasion, suggesting its potential as a therapeutic target for novel treatments against S. pneumoniae infections.