Construction, expression and characterization of 11 putative flagellar apparatus genes of Aeromonas hydrophila AL09-73.

Aquaculture has been the fastest growing foodproducing sector worldwide in the past several decades and is expected to continue being crucial in the future (Brugere & Ridler 2004). Despite aquaculture’s rapid expansion, diseases have always been a very critical limiting factor in aquacultural industry. It is estimated that the U.S. catfish industry loses millions of dollars annually to various infectious diseases (Wagner et al. 2002). Recently, outbreaks of aeromonad haemorrhagic septicaemia in channel catfish in the States of Alabama and Arkansas have caused huge economic losses to catfish producers (Hemstreet 2010). The aetiologic agent is Aeromonas hydrophila. Aeromonas hydrophila, a member of the Aeromonadaceae family, is a Gram-negative, facultatively anaerobic, oxidase-positive, lysine decarboxylasepositive, arginine dihydrolase-positive, ornithine decarboxylase-negative, polar flagellar bacillus (Janda & Abbott 2010). A. hydrophila is ubiquitous in the aquatic environment and is responsible for many human and fish diseases (Thune, Stanley & Cooper 1993; Janda et al. 1994a; Austin & Adams 1996; Kuhn et al. 1997; Brouqui & Raoult 2001; Janda & Abbott 2010). The virulent factors associated with A. hydrophila pathogenesis, such as lipopolysaccharide (Merino et al. 1996; Zhang, Arakawa & Leung 2002; Canals et al. 2006a), capsules (Zhang et al. 2002), the S-layer protein (Dooley & Trust 1988a,b; Janda, Kokka & Guthertz 1994b), enterotoxin (Chakraborty et al. 1984), extracellular enzymes (Leung & Stevenson 1988; Pemberton, Kidd & Schmidt 1997), outer membrane proteins and flagella (Merino et al. 1997; Gavin et al. 2002; Sen & Lye 2007; Vilches et al. 2009) have been reported. However, the mechanism of pathogenesis has yet to be determined. Because the genomic sequence of A. hydrophila ATCC 7966 is complete and is available in the public domain (accession no.: NC_008570) (Seshadri et al. 2006), it provides us with opportunities to execute systematic and comprehensive studies on possible virulent factors of this microorganism via comparative and functional genetic approaches (Young 2001; Cliften 2004). One of these approaches is the antigen microarray, which enables us to monitor gene expression, immune responses and vaccine efficacy; detect proteins and analyse protein-protein interactions and functions (e.g. Taussig 2001, 2003; Davies et al. 2005; Kreutzberger 2006; Burbelo et al. 2010; Kunnath-Velayudhan et al. 2010; Vigil, Davies & Felgner 2010). The partial protein arrays have been developed in the following bacteria: Yersinia pestis, Treponema pallidum, Chlamydia trachomatis, Francisella tularensis, Mycobacterium avium sub. paratuberculosis, Mycobacterium tuberculosis, Pseudomonas aeruginosa and Borrelia burgdorferi (Davies et al. 2005; Li et al. 2005; McKevitt et al. 2005; Sharma et al. 2006; Bannantine et al. 2008; Barbour et al. 2008; Montor et al. 2009; Kunnath-Velayudhan et al. 2010). Correspondence H-Y Yeh, Poultry Microbiological Safety Research Unit, Richard B. Russell Research Center, Agricultural Research Service, United States Department of Agriculture, 950 College Station Road, Athens, GA 30605, USA (e-mail: hungyueh.yeh@ars.usda.gov)