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Diseases of Aquatic Organisms

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DAO 115:67-80 (2015)  -  DOI:

Pseudomonas fluorescens: identification of Fur-regulated proteins and evaluation of their contribution to pathogenesis

Li Liu1,2, Heng Chi1, Li Sun1,*

1Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, PR China
2University of Chinese Academy of Sciences, Beijing 100049, PR China
*Corresponding author:

ABSTRACT: Pseudomonas fluorescens is a Gram-negative bacterium and a common pathogen to a wide range of farmed fish. In a previous study, we found that the ferric uptake regulator gene (fur) is essential to the infectivity of a pathogenic fish isolate of P. fluorescens (wild-type strain TSS). In the present work, we conducted comparative proteomic analysis to examine the global protein profiles of TSS and the P. fluorescens fur knockout mutant TFM. Twenty-eight differentially produced proteins were identified, which belong to different functional categories. Four of these proteins, viz. TssP (a type VI secretion protein), PspA (a serine protease), OprF (an outer membrane porin), and ClpP (the proteolytic subunit of an ATP-dependent Clp protease), were assessed for virulence participation in a model of turbot Scophthalmus maximus. The results showed that the oprF and clpP knockouts exhibited significantly reduced capacities in (1) resistance against the bactericidal effect of host serum, (2) dissemination into and colonization of host tissues, and (3) inducing host mortality. In contrast, mutation of tssP and pspA had no apparent effect on the pathogenicity of TSS. Purified recombinant OprF, when used as a subunit vaccine, induced production of specific serum antibodies in immunized fish and elicited significant protection against lethal TSS challenge. Antibody blocking of the OprF in TSS significantly impaired the ability of the bacteria to invade host tissues. Taken together, these results indicate for the first time that in pathogenic P. fluorescens, Fur regulates the expression of diverse proteins, some of which are required for optimal infection.

KEY WORDS: Pseudomonas fluorescens · Ferric uptake regulator · Proteomic · Infection · Virulence · Vaccine

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Cite this article as: Liu L, Chi H, Sun L (2015) Pseudomonas fluorescens: identification of Fur-regulated proteins and evaluation of their contribution to pathogenesis. Dis Aquat Org 115:67-80.

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