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The bacterial alarmone ( p ) ppGpp is required for virulence and controls cell size and survival of P seudomonas syringae on plants
Author(s) -
Chatnaparat Tiyakhon,
Li Zhong,
Korban Schuyler S.,
Zhao Youfu
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12744
Subject(s) - virulence , biology , pseudomonas syringae , stringent response , mutant , microbiology and biotechnology , swarming motility , pathogen , quorum sensing , biochemistry , gene
Summary The stringent response, mediated by second messenger ( p ) ppGpp , results in swift and massive transcriptional reprogramming under nutrient limited conditions. In this study, the role of ( p ) ppGpp on virulence of P seudomonas syringae pv. syringae B 728 a ( PssB7 28 a ) was investigated. The virulence of the relA / spoT ( ppGpp 0 ) double mutant was completely impaired on bean, and bacterial growth was significantly reduced, suggesting that ( p ) ppGpp is required for full virulence of P . syringae . Expression of T 3 SS and other virulence genes was reduced in ppGpp 0 mutants. In addition, ppGpp deficiency resulted in loss of swarming motility, reduction of pyoverdine production, increased sensitivity to oxidative stress and antibiotic tolerance, as well as reduced ability to utilize γ‐amino butyric acid. Increased levels of ppGpp resulted in reduced cell size of PssB 728 a when grown in a minimal medium and on plant surfaces, while most ppGpp 0 mutant cells were not viable on plant surfaces 24 h after spray inoculation, suggesting that ppGpp ‐mediated stringent response temporarily limits cell growth, and might control cell survival on plants by limiting their growth. These results demonstrated that ppGpp ‐mediated stringent response plays a central role in P . syringae virulence and survival and indicated that ppGpp serves as a global signal for regulating various virulence traits in PssB 728 a .