Outer membrane protein profiles of Edwardsiella ictaluri from fish
Newton, J.C.; Blevins, W.T.; Wilt, G.R.; Wolfe, L.G.
American Journal of Veterinary Research 51(2): 211-215
1990
ISSN/ISBN: 0002-9645 PMID: 1689127 Document Number: 367174
Outer membrane proteins (OMP) prepared with sodium N-lauroyl sarcocinate (SLS) from 33 Edwardsiella ictaluri isolates from fish were examined by electrophoresis. Twenty-eight isolates from channel catfish (Ictalurus punctatus) had similar OMP profiles. Ten bands (71 kilodaltons [kD] to 19.5 kD) were identified in all isolates from channel catfish. One major 35-kD protein comprised most of the protein content of the outer membrane is isolates from channel catfish. Differences existed among isolates in the amount of protein within minor OMP bands. Edwardsiella ictaluri ATCC 33202 contained larger quantities of the 38.5- and 37-kD proteins than did the other isolates. Outer membrane protein profiles of E. ictaluri derived from Bengal danio (Danio devario) and walking catfish (Clarias batrachus) were identical to OMP profiles of isolates from channel catfish. In contrast, OMP profiles from single isolates from green knife fish (Eigemannia virescens) and white catfish (Ictalurus catus) were different. Variations in incubation time, SLS extraction time, SLS extraction number, and in vivo and in vitro passage had no effect on the OMP profile of E. ictaluri ATCC 33202. An increase in duration of sample solubilization did affect the OMP profile of E. ictaluri ATCC 33202 by decreasing the amount of protein in 52-, 46-, and 43.5-kD bands. Accompanying in the 31.5- and 28.5-kD bands and the appearance of 4 new bands (34, 33, 25.5, and 22.5 kD). Edwardsiella ictaluri, a gram-negative bacterium in the family Enterobacteriaceae, is the cause of enteric septicemia of catfish,1,2 The organism was first isolated in 1976 and is now recognized as the most important bacterial pathogen in commercially raised channel catfish3. Mechanisms used by E. ictaluri to cause enteric septicemia of catfish are poorly understood. The outer membrane of many gram-negative organisms is the site of several virulence factors including fimbriae, lipopolysaccharide, and outer membrane proteins (OMP),4-6 Edwardsiella ictaluri is fimbriated, and the lipopolysaccharide component of the outer membrane of the type strain of E. ictaluri (ATCC 33202) has been characterized,7,a However, little is known about the OMP of this organism. Potentially useful virulence markers and important epizoologic and morphologic membrane characteristics have been identified in many other gram-negative pathogens after separation of OMP with sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE).6 The purpose of the study reported here was to examine and partially characterize OMP of E. ictaluri. Outer membrane protein profiles of E. ictaluri isolates derived from channel catfish raised in various geographic locations and from fish other than channel catfish were compared after SDS-PAGE. Effects of culture conditions (length of incubation, passage on artificial medium), and OMP samples preparation (variation in sodium N-lauroyl sarcocinate [SLS] extraction procedure and OMP solubilization conditions) were also examined.