Proteomic analysis of the fish pathogen Flavobacterium columnare

Proteins identified in this study and predicted from the draft F. columnare genome were clustered into functional groups using clusters of orthologous groups (COGs), and their subcellular locations were predicted. Possible functional relations among the identified proteins were determined using pathway analysis. The total number of unique F. columnare proteins identified using both 2-D LC and 2-DE approaches was 621, of which 10.95% (68) were identified by both methods, while 77.29% (480) and 11.76% (73) were unique in 2-D LC and 2-DE, respectively. COG groupings and subcellular localizations were similar between our data set and proteins predicted from the whole genome. Twenty eight pathways were significantly represented in our dataset (P < 0.05).Results from this study provide experimental evidence for many proteins that were predicted from the F. columnare genome annotation, and they should accelerate functional and comparative studies aimed at understanding virulence mechanisms of this important pathogen.Flavobacterium columnare is a long Gram-negative rod in the family Flavobacteriaceae, one of the main phyletic lines within the Bacteroidetes group from the domain Bacteria [1]. Several species in Flavobacteriaceae cause disease in fish. F. columnare is the causative agent of columnaris disease [2], which exists both in fresh and brackish water throughout the world [3]. Outbreaks may result in high mortality, especially during spring and autumn, and are most likely associated with poor environmental conditions causing stress [4,5]. Stressful conditions are common in commercial aquaculture where production is kept at maximum levels.Columnaris disease generally begins as an external infection on the skin, fins, gills, or oral cavity [6]. On the skin and fins, lesions are characterized by dull, grayish-white or yellow erosive lesions that can progress to deep ulcers in the underlying muscle. External infection often is concurrent with systemic infection and subacu