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Title: Proteomic analysis of Flavobacterium psychrophilum cultured in vivo and in iron-limited media

Author
item Lafrentz, Benjamin
item LAPATRA, SCOTT - CLEAR SPRINGS FOODS, INC.
item CALL, DOUGLAS - WASHINGTON ST. UNIV.
item Wiens, Gregory - Greg
item CAIN, KENNETH - UNIV. OF IDAHO

Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2009
Publication Date: 12/3/2009
Citation: Lafrentz, B.R., Lapatra, S.E., Call, D.R., Wiens, G.D., Cain, K.D. 2009. Proteomic analysis of Flavobacterium psychrophilum cultured in vivo and in iron-limited media. Diseases of Aquatic Organisms. 87:171-182.

Interpretive Summary: Flavobacterium psychrophilum is the causative agent of bacterial coldwater disease and represents a significant threat to salmonid production in the United States and worldwide. The mechanisms that this bacterial pathogen uses to induce disease are not fully understood and increased knowledge of this may lead to the development of novel control strategies. This study used a proteomic approach to identify proteins of F. psychrophilum up-regulated during growth in vivo as well as under iron-limited growth conditions. A number of different proteins were identified to be up-regulated following growth in the aforementioned conditions, some of which are likely involved in pathogenesis based on functions of homologous proteins in other pathogenic bacterial species. Additionally, the identified proteins may represent potential candidate antigens for a subunit vaccine. This research lays a foundation for further experimentation to determine the precise roles of the identified proteins in pathogenesis and to evaluate their potential for use in vaccine formulations for the prevention of bacterial coldwater disease is salmonid fish.

Technical Abstract: Flavobacterium psychrophilum is the etiologic agent of bacterial coldwater disease, and the pathogenic mechanisms of this important fish pathogen are not fully understood. Identifying bacterial genes of F. psychrophilum differentially expressed in vivo may lead to a better understanding of pathogenesis and provide potential targets for vaccine development. Therefore, this study used a proteomic approach to identify proteins of F. psychrophilum expressed during in vivo as well as under iron-limited growth conditions. A total of 20 proteins were found to be differentially expressed following culture of the bacterium in vivo and were positively identified by LC-MS/MS analysis and Mascot searches of the F. psychrophilum genome. A number of proteins exhibited increased expression in vivo, and these included: several chaperone and heat shock proteins, gliding motility protein GldN, outer membrane protein OmpH, two probable outer membrane proteins (OmpA family), probable aminopeptidase precursor, probable lipoprotein precursor, 3-oxoacyl-[acyl-carrier-protein]-reductase, and several proteins with unknown function. Two proteins exhibited decreased expression in vivo and were identified as ferritin FtnA and outer membrane protein OmpA (P60). Culture of F. psychrophilum in iron-limited media resulted in similar expression for six of the twenty proteins identified with differential expression in vivo. Results from this study suggest a role of upregulated proteins in the pathogenesis of F. psychrophilum and these may represent potential vaccine candidate antigens.