Abstract:

Some authors argue that pathogenic bacteria could compete against serum transferrin for iron by their siderophore. However, Aeromonas hydrophila CRI 14, the causative agent of goldfish (Carassius auratus) hemorrhage disease, could not produce detectable siderophore when incubated at iron limited medium and analyzed by the chrome azurol S method. This strain produced clear orange halos around its colonies on the blue agar only after 2 weeks of incubation, whereas it reaches the plateau phase after 36 h of incubation in goldfish serum. Incubating 1 ml of fish serum with the extracellular proteins of 1 ml culture of CRI 14 at 37 for 30 min., the transferring-bounded iron contents decreased from 1.5g•ml-1 to 0.9g•ml-1 and 1.3g•ml-1 to 0.45g•ml-1 for goldfish and bighead (Aristichthys nobilis), respectively, and the iron binding capacity also decreased from 2.3g•ml-1 to 1.8g•ml-1 and 2.7g•ml-1 to 1.0g•ml-1 for goldfish and bighead, respectively. An in situ iron-binding experiment after polyacrylamide gel electrophoresis (PAGE) further showed that both iron-binding and free transferring have been digested by A. hydrophila protease. These results showed that A. hydrophila protease can compensate its inadequacy of siderophore for iron.

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Date 1998/06/01

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