2002 Fiscal Year Final Research Report Summary
Experimental analysis of the effects of community structure on the evolution of populations using microbial model ecosystems
| Project/Area Number |
12640615
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
生態
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| Research Institution | Ehime University |
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Principal Investigator |
NAKAJIMA Toshiyuki Ehime University, Faculty of Science, Associate Professor, 理学部, 助教授 (70314945)
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| Project Period (FY) |
2000 – 2002
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| Keywords | bacteria / ecosystem model / evolution / community structure / protozoa |
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| Research Abstract |
(1)Effects of genomic recombination on the outcome of interspecific competition
Long-term experimental cultures of bacterial populations were conducted to investigate the effects of genomic recombination on the outcome of interspecific competition on an evolutionary scale. Experimental results suggest that genomic recombination is advantageous in interspecific competition in evolutionary time due to its effect of producing more genetic variety of ecological traits.
(2)Evolutionary processes of bacterial populations in experimental communities consisting of single resource, consumer, and secondary consumer.
Long-term chemostat cultures of E.coli and T.pyriformis were conducted using glucose as the limiting resource with two replicate runs over 220 days. Three types of E.coli populations were prepared : (i) F^-, (ii) Hfr, and (iii) the mixture of both-both point mutation and recombination can occur here. The experimental analysis reveals that E.coli mutants of long-chained cell form occurre
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d in every culture type, which is less vulnerable to the predator, and coexisted with the normal cell type. The population density of T.pyriformis oscillated with larger amplitude in the system of the mixture of E.coli than the other types, suggesting that genomic recombination in the prey population destabilizes the population dynamics of predator-prey system in evolutionary time. This may be caused by the prey evolution of ecological traits (parameters) that made the system unstable.
(3)Analysis of the interaction between T.thermophila and Chlorella vulgaris in the three-species microcosm
The microcosm consisting of C.vulgaris (producer), E.coli (decomposer), and T.thermophila (consumer) was fabricated and cultured over 500 days to analyze interspecific interactions between components. In particular, the analysis reveals that the T.thermophila takes in and maintains C.vulgaris within cells. Some experiments were conducted to analyze their interaction used as an experimental model for investigating an initial step to evolve symbiogenesis. Less
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