Potential Influences of Bacterial Cell Surfaces and Nano-Sized Cell Fragments on Struvite Biomineralization

Abstract

Struvite (MgNH₄PO₄·6H₂O) calculi are formed as a result of urinary tract infections by <i>Proteus mirabilis</i> and other urease-producing bacteria. During struvite formation, the bacteria grow as biofilms, and thus crystals are formed in close association with bacterial cell surfaces and biofilm matrix components. Small nano-sized objects (originally termed “nanobacteria”) have been described in association with urinary calculi including struvite calculi. A much more likely explanation of these nano-structures is outer membrane vesicles (OMVs) that can be produced by <i>P. mirabilis</i> and other Gram-negative bacteria. In this brief review, we describe the association of bacterial cell surfaces and biofilm matrix components with metal binding and the generation of chemical microenvironments during struvite formation; we propose potential mechanisms whereby OMVs can influence struvite crystal growth and biomineralization.