Abstract
The skin mucus of ayu was collected from the body surface and its homogenate in phosphate buffer (pH 6.8) was fractionated by Toyopearl HW-50. Each fraction from the gel was examined on the bacteriolytic activities against Micrococcus lysodeikticus or Vibrio anguillarum, the etiological agent of vibriosis of ayu. The activity was determined by the turbidimetric method using the lyophilized cells of M. lisodeikticus or the formaline-killed and lyophilized cells of V. anguillarum.
The heighest bacteriolytic activities in the fractions against both M. lysodeikticus and V. anguillarum appeared in the same fraction. This fraction showed the maximal bacteriolytic ac-tivity against M. lysodeikticus in 0.01M Tris-HCl buffer of pH 7.2 at 30°C and also showed that against V. anguillarum in 0.01M Tris-HCl buffer of pH 7.7 at 15°C. These activities were partially inhibited by ρ-chloromercuribenzoic acid, but in contrast the lysozyme from hen egg-white was not. After this fraction was treated with chitin, the bacteriolytic activity against M. lysodeikticus disappeared. The optimal temperature for vibriolytic activity in the chitin-absorbed fraction shifted from 15 to 30°C and also the optimal pH shifted from 7.7 to 8.6.
These results suggest that the bacteriolytic enzymes in the skin mucus of ayu exhibit more than two, and these work cooperatively for the protection against penetration of bacteria from the water environment into the body.
