ISSN:
1432-072X
Keywords:
Thermoproteus neutrophilus
;
Archaebacterium
;
Autotrophic
;
Reductive citric acid cycle
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Growth of Thermoproteus neutrophilus at 85°C was studied using an improved mineral medium with CO2, CO2 plus acetate, CO2 plus propionate, or CO2 plus succinate as carbon sources; sulfur reduction with H2 to H2S was the sole source of energy. None of the carbon compounds added was oxidized to CO2. The organism grew autotrophically with a generation time of 9–14 h, up to a cell density of 0.5 g dry weight per liter (2×109 cells/ml). Propionate did not stimulate, succinate slightly stimulated the growth rate. Acetate, even at low concentrations (0.5 mM), stimulated the growth rate, the generation time being shortened to 3–4 h. Acetate provided 70% of the cell carbon, which shows that Thermoproteus neutrophilus is a facultative autotroph. The path of these carbon precursors into cell compounds was studied by 14C long-term labelling and investigation of enzyme activities. Propionate could not be used as a major carbon source and was incorporated only into isoleucine, probably via the citramalate pathway. Acetate was a preferred carbon source which suppressed autotrophic CO2 fixation: acetate grown cells exhibited an incomplete citric acid cycle in which 2-oxoglutarate dehydrogenase was present, but fumarate reductase was “repressed”. The succinate incorporation pattern and enzyme pattern indicated that autotrophic CO2 fixation proceeded via a yet to be defined reductive citric acid cycle.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00403234
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