Biological and chemical characteristics of the aged microcosm and its ecological significance.

Research Project

Project/Area Number	62480004
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	生態学
Research Institution	TOHOKU UNIVERSITY
Principal Investigator	KURIHARA Yasushi Faculty of Science, Tohoku University, 理学部, 教授 (90004259)
Co-Investigator(Kenkyū-buntansha)	杉浦桂相模女子大学, 学芸学部, 講師 (30080469) SHIKANO Shuichi Faculty of Science, Tohoku University, 理学部, 助手 (70154185) KIKUCHI Eisuke Faculty of Science, Tohoku University, 理学部, 助教授 (00004482) SUGIURA Katura Sagami Women's University
Project Period (FY)	1987 – 1988
Project Status	Completed (Fiscal Year 1988)
Budget Amount *help	¥4,000,000 (Direct Cost: ¥4,000,000) Fiscal Year 1988: ¥1,500,000 (Direct Cost: ¥1,500,000) Fiscal Year 1987: ¥2,500,000 (Direct Cost: ¥2,500,000)
Keywords	Microcosm / Closed system / Community metabolism activity / Bacteria / Serial transfer / 形質変化 / 種間競争 / 低濃度培地 / 過老令化 / 開放系 / 閉鎖系 / 群集維持 / 構成種の単離
Research Abstract	We have made observation on closed microcosms (medium:air = 2:1), which did not exchange gas with the atmosphere, when flasks were stoppered with rubber plugs at 25 d of cultivation. The population densities and the diural changes of dissolved oxygen in the closed microcosms were same as those in the control microcosm, which exchanged gas with atmosphere. The concentration of gaseous oxygen were almost constant in the closed microcosms. Thus, the population densities and the level of community metabolism activity could be maintained after microcosms were totally closed at mature stage. In an attempt to clarify the significance of characteristics of bacterial populations in aged microcosms, the growth rates of bacteria were investigated. Bacteriafrom the microcosms were subjected to serial transfer at 3 d intervals in both single and two-species culture. Selection in single species populations under serial transfer favored an increased growth rate. When selection was applied to mixed populations, the growth rates of both species did not change or were sometimes reduced from that of parental strain. These results can be viewed as evidence for a trade-off between interspecitic competitive ability and growth rate. Selection was applied to adapting bacterial populations in two ways: in high nutrient (Bac-H) and low nutrient (Bac-L) medium. The growth rate of Bac-L was higher than that of Bac-H in low nutrient medium and the growth rate of Bac-L was lower than that of Bac-H in high nutrient condition.