Location: Aquatic Animal Health Research
Title: Flagella Structure and Gene Sequences of the Fish Pathogen Edwardsiella ictaluri Authors
Submitted to: American Society of Microbiologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2008
Publication Date: June 1, 2008
Citation: Panangala, V.S., Russo, R., Van Santen, V.L., Klesius, P.H. 2008. Flagella Structure and Gene Sequences of the Fish Pathogen Edwardsiella ictaluri. In:108th General Meeting of the American Society of Microbiologists,June 1-5, 2008, Boston, MA. p. Z-025. Technical Abstract: Edwardsiella icatluri the cause of enteric septicemia in channel catfish (Ictalurus punctatus) are motile by means of peritrichous flagella, a virulence determinant. Molecular composition of this polymeric structure in E. ictaluri remains largely unknown. Methods: Monoclonal antibodies (MAbs) developed against purified flagella of E. ictaluri enabled detection of two protein bands ~ 35 and 37 kd respectively by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoelectron microscopy confirmed the specificity of the MAb for flagella antigens of E. ictaluri. Amino acid sequence analysis of the 35 and 37 kd peptides revealed several peptides in common with the flagellin proteins of E. tarda. Partial flagellin gene sequences were determined by amplification of genomic E. ictaluri DNA with degenerate primers. Complete flagellin gene sequences and their organization was determined by sequencing genomic segments selected from a lambda-ZAP phage genomic library of E. icatluri. Results: Four flagellin genes are arranged in tandem within 6 kb in the E. ictaluri genome. The second, third, and fourth genes are separated by less than 300 nt. The first and second flagellin genes are separated by 1.1 kb, which include a 172-codon ORF with homology to the amino terminal portion of a mutator-type transposase distinct from the E. ictaluri TnpA. The predicted amino acid sequences of all four genes are similar in the N terminal (AA 1-160) and C terminal (last 74 AA) portions and are divergent in the central portion of the proteins. The proteins encoded by the first three flagellin genes are more similar to each other (88-90% AA identity) than to the protein encoded by the fourth flagellin gene (76-78% AA identity). The predicted sizes of the encoded proteins range between 36 and 37.5 kd. BLAST analysis of GenBank sequences showed that all four flagellin AA sequences are more similar to those of Serratia marcescens (72-74% identity) than to those of E. tarda (equal to or less than 62% identity). Conclusion: The E. ictaluri genome encodes at least four distinct flagellin proteins, which are most similar to S. marcescens flagellin proteins.