The ATP-Dependent Protease ClpP Inhibits Biofilm Formation by Regulating Agr and Cell Wall Hydrolase Sle1 in Staphylococcus aureus.

Qian Liu,Lei He,Xing Wang,Xiaoyun Liu,Won-Sik Yeo,Sen Cheng,Min Li,Taeok Bae,Xiaowei Ma,Juanxiu Qin

doi:10.3389/fcimb.2017.00181

Abstract

Biofilm causes hospital-associated infections on indwelling medical devices. In Staphylococcus aureus, Biofilm formation is controlled by intricately coordinated network of regulating systems, of which the ATP-dependent protease ClpP shows an inhibitory effect. Here, we demonstrate that the inhibitory effect of ClpP on biofilm formation is through Agr and the cell wall hydrolase Sle1. Biofilm formed by clpP mutant consists of proteins and extracellular DNA (eDNA). The increase of the protein was, at least in part, due to the reduced protease activity of the mutant, which was caused by the decreased activity of agr. On the other hand, the increase of eDNA was due to increased cell lysis caused by the higher level of Sle1. Indeed, as compared with wild type, the clpP mutant excreted an increased level of eDNA, and showed higher sensitivity to Triton-induced autolysis. The deletion of sle1 in the clpP mutant decreased the biofilm formation, the level of eDNA, and the Triton-induced autolysis to wild-type levels. Despite the increased biofilm formation capability, however, the clpP mutant showed significantly reduced virulence in a murine model of subcutaneous foreign body infection, indicating that the increased biofilm formation capability cannot compensate for the intrinsic functions of ClpP during infection.

Highlights

Bacteria biofilms are complex communities which have intrinsic resistance to host immune defenses and antibiotic treatment (Paharik and Horswill, 2016)
ClpP mutants showed enhanced biofilm formation (Figure 1), indicating that the biofilm inhibitory effect of ClpP is likely to be universal among S. aureus strains
When biofilm formation was analyzed in the presence of shear stress (0.15 dynes/cm2), which imitates blood flow in veins, the biofilm inhibitory effect of ClpP was still observed (Figure 1B)

Summary

Introduction

Bacteria biofilms are complex communities which have intrinsic resistance to host immune defenses and antibiotic treatment (Paharik and Horswill, 2016). Staphylococcal biofilm can be polysaccharide intercellular adhesion (PIA)-dependent or proteins/ extracellular DNA (eDNA)-dependent (McCarthy et al, 2015). ClpP Inhibits Biofilm Formation the enzyme encoded by the icaADBC operon, and can be an important component of the biofilm matrix (Cramton et al, 1999; Gotz, 2002; Jefferson et al, 2004). Several studies have shown that S. aureus can form a biofilm by proteins and eDNA without PIA-involvement (Toledo-Arana et al, 2005; Rohde et al, 2007). In the PIA-independent biofilm, extracellular DNA (eDNA) is an important component of biofilm matrix (Kiedrowski et al, 2011; Okshevsky and Meyer, 2015). Secreted protease Esp inhibits biofilm formation by cleaving murein hydrolase autolysin (Atl) and preventing release of eDNA (Chen et al, 2013)

Methods

Results

Conclusion