Tn-seq of Staphylococcus aureus exposed to Calprotectin

The host protein calprotectin inhibits the growth of a variety of bacterial pathogens through metal sequestration in a process known as 'nutritional immunity'. Staphylococcus aureus growth is inhibited by calprotectin in vitro and calprotectin is localized in vivo to staphylococcal abscesses during infection. However, the staphylococcal adaptations that provide defense against nutritional immunity and the role of metal-responsive regulators are not fully characterized. In this work, we define the transcriptional response of S. aureus and the role of the metal-responsive regulators, Zur, Fur, and MntR, in response to metal limitation by calprotectin exposure. Additionally, we identified genes affecting the fitness of S. aureus during metal limitation through a Transposon sequencing (Tn-seq) approach. Loss of function mutations in clpP, which encodes a proteolytic subunit of the ATP-dependent Clp protease, demonstrate reduced fitness of S. aureus to the presence of calprotectin. ClpP contributes to pathogenesis in vivo in a calprotectin-dependent manner. These studies establish a critical role for ClpP to combat metal limitation by calprotectin and reveal the genes required for S. aureus to outcompete the host for metals. This study sought to uncover genes that affect the fitness of S. aureus when the bacteria experience calprotectin-mediated metal starvation by performing a genome-wide Tn-seq screen on bacteria grown in the presence of WTCP or ∆s1CP