UC San Diego

Staphylococcus aureus bacteria are gram-positive cocci that are notorious for causing various skin infections. Since the emergence of antibiotic resistant strains, the increasing incidence of bacterial infections has become worldwide concern. Therefore, continued investigation on mechanisms that may play a role in fighting bacterial infections is critical. It is our working hypothesis that the calcification of live S. aureus bacteria by the previously discovered serum calcification factor may be involved in a vertebrate's immunological response against bacterial infections. Previous in vitro studies performed in our lab demonstrated that dead S. aureus bacteria are calcified in serum [1]. The goal of our study was to further understand the role of bacterial calcification in the defense against infections. To accomplish this, we developed a serum-free calcifying system where all parameters were defined. This system allowed us to investigate the consequences of calcifying living bacteria, a phenomenon that was not previously explored. Without any serum factors, we are able to understand the repercussions solely due to the calcification of the bacteria. The results show that mineralization affects the viability and growth rate of the bacteria. Our studies also show that live S. aureus bacteria are likely to be calcified in blood by a mechanism that targets the size exclusion characteristics of the cell wall, a feature unique to bacteria. Future studies have been proposed to better understand the role of bacterial calcification in vivo