| Summary: | 碩士 === 國立臺灣大學 === 漁業學系 === 82 === Cecropin A, cecropin P1 and lysozyme susceptibilities of the
common aquatic pathogens were tested with an inhibition
zone assay. Results showed that cecropins could inhibit growth
of the 16 stains of bacteria, including Aeromonas hydrophila,
A. salmo- nicida, Escherichia coli, Vibrio alginolyticus, V.
anguillarum, V. carchariae, V. damsela, V. fluvialis, V.
harveyi, V. ordalii , V, parahemolytics, V. tubiashii and V.
vulnificus. Cecropins also inhibited growth of 2 pathogenic
yeast stains, Debaryomyces hansenii. However, antibacterial
activities of cecropins could not reach to Edwardsiella
tarda, as well as, V. vulnificus strains isolated from a
diseased eel. Microbicidal activity pro- vided by the lysozyme
only acted on D. hansenii. We used the inhibition zone assay
to detecte the presence of antimicrobial substances produced
by giant freshwater prawn (Ma- crobrachium rosenbergii). When
prawn were injected into the peri- cardial cavity with E.
coli cells, hemolymph were collected at
1,2,3,4,5,6,12,18,24,48,72 hours post-injection. Assay of
the partially purified and concentrated plasma on E. coli
agarose plate showed an induced bacterial substance(s). The
antibacterial activity appeared in 31% of tested prawn
plasma 6 hrs post- injection. Same activity was shown in 79%
of tested plasma 24 hrs post-injection. However, it was not
detected in all tested plasma 72 hrs post-injection. It
suggests that most of the prawn will synthesize
antibacterial substance(s) once stimulated. However, this
activity was short-term and concentration was estimated no
more than 0.21uM in prawn plasma. Western blot analysis of
plasma with an antibacterial acti- vity showed an induced 35kd
substance when it was stained with a rabbit-anti-cecropin A
serum. These results indicated that the antibacterial
substance induced in giant freshwater prawn may be a cecropin-
like.
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