Concerning the S-R dissociation of Sh. sonnei there are abundant reports. The author obtained the following results by employing the virulent strain which had caused violent food poisoning.
At first in order to facilitate the differntiation of S-R changes the Endo culture medium was partially modified and the variation of Sh. sonnei has been observed by performing the series of cultures on the medium taking serological aspects into consideration.
1) With the S-type the series of cultures successive incubations were carried out for 300 generations and always about five per cent of them indicated R-type dissociation.
2) In the series of cultures on the medium loaded with certain sugars the R-type dissociation became less apparent and after the fifth in every generation a wholly pure S-type was obtained.
3) In the experiments comparing the virulency of the bacteria cultured under the various conditions against animals, the virulency of the bacteria cultured in the soft gruel of rice malt proved to be strongest.
4) In the experiment of reconversion of the R-type bacteria to the S-type, either by culture in the media loaded with various substances or by passage through animals, no reconversion of R-type back to S-type has taken place at least in the author's experiments.

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There are just as many reports on the l-histidine decarboxylase activity of dysentery bacilli as those on the other bacteria.
In the course of elucidation of the causative factors of violent food poisoning that occurred in the Okayama Prefecture in 1953, the author has made a report on the S-R dissociation and the virulency of Sh. sonnei in the Report 1. In the preaent report the biological nature of the virulent strain is described.
1) Sh. sonnei grow most rapidly in the medium whose optimal pH is 7.0-7.6, but when the pH falls under 4.3 the growth of bacteris is completely inhibited: and in addition, the peaks of the growth are correlated with changes in the pH of the medium.
2) In the cultures performed in test-tubes and flasks, R-type bacteia grew in the flask much better than S-type, while on the contrary in the test-tubes R-type bacteria growth was inferior to that of the S-type.
3) As for the growth of Sh. sonnei in soft gruel of rice malt, although the growth does not reach as high degree as observed in the peptone medium but it reaches the maximum growth within 12 hours. After 24-hour culture, however, the growth tends to decline.
4) On examining by paper chromatography and by Warburg's apparatus the l-histidine decarboxylase activity of the isolated strain that has been cultured in the media of peptone solution loaded with l-histidine and with additional various sugars, the excretion of carbon dioxide gas and the production of histamine are observable only in the cases where these bacteria are grown in the media containing additional glucose, maltose, or mannose.
5) Acetone powder of Sh. sonnei that has been cultured in the medium of glucose-peptone solution loaded with l-histidine possesses the l-histidine decarboxylase activity and acts specifically to the substrate.

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Amidst the COVID-19 pandemic, the opportunity of local interaction has been significantly decreased and the place of activity was moved from in-person to online. In 2021, voluntary students from Akita International University organized two online events which aimed to convey Akitas regional food by welcoming participants from domestic and overseas. This paper reflects these events and explores the possibility of online community exchange activities. Although there should be a continuous update on ICT skills and knowledge, we conclude that facilitating “active interaction” is the utmost key in designing comfortable and satisfying online events.

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