ISSN:
1432-072X
Keywords:
Key words Autotrophic CO2 fixation
;
Dissimilatory
;
nitrate reduction
;
Archaeoglobus species
;
Methanogenic Archaea
;
Methanofuran
;
Tetrahydromethanopterin
;
Coenzyme F420
;
Cytochromes
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The strictly anaerobic Archaeon Ferroglobus placidus was grown chemolithoautotrophically on H2 and nitrate and analyzed for enzymes and coenzymes possibly involved in autotrophic CO2 fixation. The following enzymes were found [values in parentheses = μmol min–1 (mg protein)–1]: formylmethanofuran dehydrogenase (0.2), formylmethanofuran:tetrahydromethanopterin formyltransferase (0.6), methenyltetrahydromethanopterin cyclohydrolase (10), F420-dependent methylenetetrahydromethanopterin dehydrogenase (1.5), F420-dependent methylenetetrahydromethanopterin reductase (0.4), and carbon monoxide dehydrogenase (0.1). The cells contained coenzyme F420 (0.4 nmol/mg protein), tetrahydromethanopterin (0.9 nmol/ mg protein), and cytochrome b (4 nmol/mg membrane protein). From the enzyme and coenzyme composition of the cells, we deduced that autotrophic CO2 fixation in F. placidus proceeds via the carbon monoxide dehydrogenase pathway as in autotrophically growing Archaeoglobus and Methanoarchaea species. Evidence is also presented that cell extracts of F. placidus catalyze the reduction of two molecules of nitrite to 1 N2O with NO as intermediate (0.1 μmol N2O formed per min and mg protein), showing that – at least in principle –F. placidus has a denitrifying capacity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002030050411
