ARS | Publication request: Urease Activity and Virulence in Edwardsiella ictaluri

Submitted to: Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: March 16, 2007
Publication Date: June 5, 2007
Citation: Booth, N.J., Beekman, J., Thune, R.L. 2007. Urease Activity and Virulence in Edwardsiella ictaluri. Aquaculture.

Technical Abstract: Edwardsiella ictaluri encodes a urease complex that is required for infection of the channel catfish host and for replication in channel catfish macrophages. The complex is comprised of nine genes, including ureA, B and C, which encode the primary enzymatic subunits, ureD, E, F and G, which encode accessory proteins, ureI, which encodes a urea transporter, and amtB, which encodes an ammonium transporter. E. ictaluri is very acid tolerant and is able to survive for at least 2 hours when suspended in phosphate buffered saline down to pH 3, but the pH must be at least 6 for growth to occur. Wild-type E. ictaluri, however, can increase media pH in broth at pH 5 when urea is available in the media, and increased pH is accompanied by bacterial growth. No pH increase or growth occurs when a strain carrying a mutation in the urease essential ureG gene is used. Using two-dimensional polyacrylamide gel electrophoresis (pH 4.7-5.9) and mass spectrometry, the UreA, UreC, and UreG proteins were identified from cells grown at both pH 5.5 and 7.0 in the presence of 6 mM urea. Ammonia production, however, is only detected when E. ictaluri is grown at pH 5.0, suggesting that inactive enzyme was produced at pH 7.