Anti-streptococcal activity of digestive juice in various stains of silkworm, Bombyx mori.

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  • 家蚕の各種系統における消化液の抗Ｓｔｒｅｐｔｏｃｏｃｃｕｓ活性について
  • カサン ノ カクシュ ケイトウ ニ オケル ショウカエキ ノ コウ Strep

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In order to elucidate the genetic control of the anti-streptococcal activity (ASA) in the digestive juice (DJ) of the silkworm, Bombyx mori, the ASA was investigated on various strains and their hybrids which were reared on mulberry leaves until the 3rd day of the 5th instar. The DJ was fractionatd by the stepwise addition of saturated ammonium sulfate at 10% intervals, and the ASA in terms of ASA90, which indicates the dilution times to attain ED90 in the inhibition on the growth of test bacterium, was assayed in vitro for each fraction. In each strain so far investigated ASA was detected between 20-80% saturation of ammonium sulfate and there were two peaks of ASA, i.e. in 30-40%, and 50-60% or 60-70% saturations. Total ASA90 was distributed in the range between 300 and 600, and the value of the hybrids was higher than those in their parents, which seemed to indicate heterosis. When the protein fraction prepared by precipitation of DJ with ammonium sulfate at 80% saturation was applied to Sepharose 6B, ASA was eluted as three peaks, which were named as A, B and C. The elution profile indicated incomplete separation between A and B but the clear separation between A or B, and C. Strain H4 had higher peaks in A and B compared with one of Kojiki and Daizo, both of which are considered to be more classical strains of the silkworms. The ASA of the hybrid, Kojiki×Daizo showed approximate value to the higher of their parents. These results suggest that the anti-streptococcal activity in the digestive juice of the silkworm, Bombyx mori might be controlled genetically.

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