1993 Fiscal Year Final Research Report Summary
Bacterial Adaptaion to an alkaline Enviroment
| Project/Area Number |
04671342
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Biological pharmacy
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| Research Institution | Chiba University |
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Principal Investigator |
KOBAYASHI Hiroshi Chiba University, Faclty of Phrmaceutical Sciences, Associate Professor., 薬学部, 助教授 (00090473)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Escherichia coli / Bacteria / Adaptation to Alkaline pH / Ebironmental adaptation |
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| Research Abstract |
Nicroorganisms are good materials for clarifying the adaptationof living things to ensironmental changes, since their habitat encompasses all surface of the earth. We have studied the bacterial adaptation to change in environmental pH, and found that the change in cellular metabolisms to ones resistant to alkaline pH is essential for the adaptation to an alkaline pH, rather than the maintenance of the neutral cytoplasm. In the present study, we have carried out biochemical and genetical studies of genes which are essential for growth in an alkaline medium, and following results have been obtained. (1) In desagreenent with the previous propasal that Na^+/H^+ antiporter maintains the neutral cytoplasm of E.coli growing in an alkaline medium, it is suggested that the physiological functionof this antiporter is to maintain the internal sodium ion concentration at a low level in an alkaline medium as well as neutral and acidic madia. (2) We have found that ChaA, which was originally reported to be a Ca^<++>/ antiporter, is a third system for sodium ion extrusion fuctioning at an alkaline pH.Our present data suggest that E.coli uses NhaB to extrude sodium ion in neutral and acidec media, and that NhaA and ChaA are used at an alkaline pH.(3) We have isolated mutants which are unable to grow at an alkaline pH, even if the medium level of sodium ion is low. It is therefore suggested that, in addition to nhaA and chaA, E.cli has other genes fumctioning at a high pH.
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