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Microbiol Res. 2016 Nov;192:84-95. doi: 10.1016/j.micres.2016.06.005. Epub 2016 Jun 15.

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

Author information

1
Central Laboratory, Xinqiao Hospital, Third Military Medical University, Chongqing, China; Department of Microbiology, College of Basic Medical Sciences, Third Military Medical University, Chongqing, China.
2
Central Laboratory, Xinqiao Hospital, Third Military Medical University, Chongqing, China.
3
Central Laboratory, Xinqiao Hospital, Third Military Medical University, Chongqing, China. Electronic address: zhangkebin12@163.com.
4
Central Laboratory, Xinqiao Hospital, Third Military Medical University, Chongqing, China; Department of Microbiology, College of Basic Medical Sciences, Third Military Medical University, Chongqing, China. Electronic address: huxiaomei@tmmu.edu.cn.

Abstract

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.

KEYWORDS:

Biofilm formation; Guanosine 5′-triphosphate-3′-diphosphate; Pseudomonas aeruginosa; Quinolone quorum-sensing system; Type III secretion system; Virulence

PMID:
27664726
DOI:
10.1016/j.micres.2016.06.005
[Indexed for MEDLINE]
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