Role of ppGpp in Pseudomonas aeruginosa acute pulmonary infection and virulence regulation

• DOI: 10.1016/j.micres.2016.06.005
• Publication Date: 2016-06-18T18:48:14Z
• Authors: Xiaohui Xu; Hua Yu; Di Zhang; Junzhi Xiong; Jing Qiu; Rong Xin; Xiaomei He; Halei Sheng; Wenqiang Cai; Lu Jiang; Kebin Zhang; Xiaomei Hu
• Keywords: Male; 0301 basic medicine; Microbial Viability; Virulence; Virulence Factors; Guanosine Pentaphosphate; Quorum Sensing; 3. Good health; Disease Models, Animal; Mice; 03 medical and health sciences; Phenotype; Bacterial Proteins; A549 Cells; Biofilms; Pseudomonas aeruginosa; Pneumonia, Bacterial; Type III Secretion Systems; Animals; Humans; Pseudomonas Infections; Gene Deletion

During infection, bacteria might generate adaptive responses to facilitate their survival and colonization in the host environment. The alarmone guanosine 5'-triphosphate-3'-diphosphate (ppGpp), the levels of which are regulated by the RelA and SpoT enzymes, plays a critical role in mediating bacterial adaptive responses and virulence. However, the mechanism by which ppGpp regulates virulence-associated traits in Pseudomonas aeruginosa is poorly understood. To investigate the regulatory role of ppGpp, the ppGpp-deficient strain ΔRS (relA and spoT gene double mutant) and the complemented strain ΔRS(++) (complemented with relA and spoT genes) were constructed. Herein, we reported that the ΔRS strain showed decreased cytotoxicity towards A549 human alveolar adenocarcinoma cell lines and led to reduced mortality, lung edema and inflammatory cell infiltration in a mouse model of acute pneumonia compared to wild-type PAO1 and the complemented strain ΔRS(++). Subsequent analyses demonstrated that the ΔRS strain displayed reduced T3SS expression, decreased levels of elastase activity, pyocyanin, pyoverdin and alginate, and inhibited swarming and biofilm formation compared to PAO1 and the complemented strain ΔRS(++). In addition, the results demonstrate that ppGpp-mediated regulation of T3SS, virulence factor production, and swarming occurs in a quinolone quorum-sensing system-dependent manner. Taken together, these results suggest that ppGpp is required for virulence regulation in P. aeruginosa, providing new clues for the development of interference strategies against bacterial infection.