
A new study explores the role of inorganic polyphosphate (polyP) in the biofilm formation, capsule production, and virulence of hypervirulent Klebsiella pneumoniae (hvKP), a bacterial strain responsible for severe and often antibiotic-resistant infections. The study aimed to understand how polyP impacts the pathogenicity of these bacteria, as hypervirulent strains are increasingly problematic in clinical settings.
To investigate this, the researchers from the University of Chile focused on polyphosphate kinase 1 (PPK1), an enzyme involved in the synthesis of polyP. By creating mutant strains of hvKP lacking the PPK1 enzyme (Δppk1 mutants), they studied the effects of polyP deficiency on several key factors, including biofilm formation, capsule production, and virulence. Additionally, they used Dictyostelium discoideum, an amoeba model, to evaluate the impact of these mutations on bacterial virulence. A proteomic analysis was conducted to observe changes in protein expression that relate to the bacterium's virulence factors.
A key technique in this study was the use of EbbaBiolight 680 to visualise and quantify the biofilm matrix produced by the bacteria. EbbaBiolight binds to cellulose and other extracellular polymeric substances (EPS) present in the biofilm, allowing the researchers to assess the biofilm’s structure. The fluorescence intensity from EbbaBiolight staining confirmed that polyP metabolism plays a crucial role in biofilm formation.
The study concluded that the PPK1 enzyme is vital for proper biofilm assembly, capsule formation, and virulence in hvKP. Mutants lacking PPK1 produced less biofilm and capsule, weakening their ability to evade immune defences and reducing their virulence. These findings suggest that targeting polyP metabolism could be a promising strategy for developing new treatments against hypervirulent K. pneumoniae infections.
Image: EbbaBiolight 680 was used to detect cellulose and amyloid components in the extracellular polymeric substances (EPS) of biofilms. Two strains of hypervirulent K. pneumoniae, SGH10 WT and SGH10 Δppk1 (which lacks the PPK1 enzyme essential for polyP metabolism), were tested. SGH10 mutant exhibited lower EPS levels compared to the wild-type strain, confirming the critical role of polyP metabolism in biofilm formation. Image created with BioRender.