FERMENTATIVE DEGRADATION OF GLYCOLIC ACID BY DEFINED SYNTROPHIC COCULTURES

被引:20
作者
FRIEDRICH, M
LADERER, U
SCHINK, B
机构
[1] Lehrstuhl Mikrobiologie I der Eberhard-Karls-Universität, Tübingen, W-7400
关键词
INTERSPECIES HYDROGEN TRANSFER; METHANOGENESIS; HOMOACETOGENESIS; MALIC ENZYME; SUBSTRATE LEVEL PHOSPHORYLATION;
D O I
10.1007/BF00248717
中图分类号
Q93 [微生物学];
学科分类号
071005 ; 100705 ;
摘要
Three different defined cocultures of glycolate-degrading strictly anaerobic bacteria were isolated from enrichment cultures inoculated with freshwater sediment samples. Each culture contained a primary fermenting bacterium which used only glycolate as growth substrate. These cells were gram-positive, formed terminal oval spores, and did not contain cytochromes. Growth with glycolate was possible only in coculture with either a homoacetogenic bacterium or a hydrogen-utilizing methanogenic bacterium; the overall fermentation balance was either 4 glycolate --> 3 acetate + 2CO2, or 4 glycolate --> 3 CH4 + 5 CO2. These transformations indicate that glycolate was converted by the primary fermenting bacterium entirely to CO2 and reducing equivalents which were transferred to the partner organisms, probably through interspecies hydrogen transfer. The key enzymes of fermentative glycolate degradation were identified in cell-free extracts. An acetyl-CoA and ADP-dependent glyoxylate-converting enzyme activity, malic enzyme, pyruvate synthase, and methyl viologen-dependent hydrogenase were found at comparably high activities suggesting that these bacteria oxidize glycolate through a new pathway via malyl-CoA, and that ATP is synthesized by substrate-level phosphorylation, in a similar manner as found in a recently isolated glyoxylate-fermenting anaerobe.
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页码:398 / 404
页数:7
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