(Kyushu University)

12月11日（火）13：30〜 理学部3号館6階数理生物学セミナー室
(at Room 3631, 6th floor of building 3 of the Faculty of Sciences)

Organisms often alter physicochemical conditions (e.g. Temperature, pH and humidity) and the conditions constrains and naturally selects organisms. This connection indicates feedback between life and its environment. We investigated the possibility of negative feedback, which could counteract changes of physicochemical conditions. For this purpose, we examined an interaction between pH and pH-affecting bacteria (e.g. cyanobacteria), using a chemostat model, which has been well- studied model of an open system with purely exploitative competition. We considered two cases where only 1 species or 2 species existed in the chemostat. We show that a pH stability against acid loads arises for both the cases, however, pH can be loosely stabilized at extremely alkaline or acidic level when only 1 species exists, while it can be maintained constant at more mild level when 2 species coexist. It may imply a link between the coexistence of species and the stability and habitability of physicochemical conditions.

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