Deletion of SarX Decreases Biofilm Formation of Staphylococcus aureus in a Polysaccharide Intercellular Adhesin (PIA)-Dependent Manner by Downregulating spa

Zhihao Hao,1,* Yinjuan Guo,2,* Lulin Rao,3 Jingyi Yu,3 Qing Zhan,4 Yanlei Xu,4 Bingjie Wang,2 Xiaocui Wu,2 Fangyou Yu2 1Department of Laboratory Medicine, Shandong Provincial Third Hospital, Cheeloo College of Mdicine, Shandong University, Ji Nan, 250000, People’s Republic of China; 2Department of Laboratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, 200082, People’s Republic of China; 3Department of Laboratory Medicine, Wenzhou Medical University, Wenzhou, 325000, People’s Republic of China; 4Department of Laboratory Medicine, Nanchang University, Nanchang, 330000, People’s Republic of China*These authors contributed equally to this workCorrespondence: Fangyou YuDepartment of Laboratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, 507 Zhengmin Road, Yangpu District, Shanghai, 200082, People’s Republic of ChinaEmail wzjxyfy@163.comIntroduction: Biofilm formation by Staphylococcus aureus is an important virulence determinant mediated by the polysaccharide intercellular adhesin (PIA) encoded by the ica operon or mediated by surface and extracellular proteins. SarX is a 250-residue two-domain SarA homolog that activates spa transcription. Previous studies demonstrated that Staphylococcus epidermidis SarX protein regulated the transcriptional activity of the agr and ica loci and controlled the biofilm phenotype, primarily by regulating icaADBC transcription and PIA production.Results: In this study, biofilm formation and detachment of the clinical isolate S. aureus SA75 were significantly decreased in the sarX mutant strain. The effect of sarX mutation on S. aureus biofilm formation was related to the production of PIA and not to that of eDNA. Deletion of sarX was associated with a 1.8-fold reduction in spa transcription as determined by RT-PCR analysis, and this reduction could be restored by chromosomal complementation of sarX. Expression of Sp