Open AccessStudies in the fat metabolism of the Timothy Grass Bacillus. II.—The carbon balance-sheet and respiratory quotient
Author(s) -
Marjory Stephenson,
Margaret Dampier Whetham
Publication year - 1923
Publication title -
proceedings of the royal society of london. series b, containing papers of a biological character
Language(s) - English
Resource type - Journals
eISSN - 2053-9185
pISSN - 0950-1193
DOI - 10.1098/rspb.1923.0032
Subject(s) - ammonium , chemistry , nitrogen , respiratory quotient , potassium , carbon dioxide , food science , aspergillus niger , kjeldahl method , phosphate , carbon fibers , zoology , biochemistry , biology , organic chemistry , materials science , composite number , composite material
It was shown in a previous communication [Stephenson and Whetham, 1922 (1)] that the Timothy Grass Bacillus can be cultivated on a synthetic medium containing potassium phosphate (KH2 PO4 : 0·4 per cent.), and magnesium sulphate (MgSO4 . 7H2 O : 0·07 per cent.), with ammonium phosphate ((NH4 )2 . HPO4 : 0·4 per cent.) as the sole source of nitrogen, and glucose (1 percent.) as the sole source of carbon. The cultivation was carried out in Roux bottles, and the hydrogen ion concentration was kept constant at PH = 8·0 by the presence of excess of calcium carbonate. Under these conditions, the glucose was completely used in about 21 days; no breakdown products other than carbon dioxide were found; the protein nitrogen and lipoid contents of the bacillus were estimated at intervals and found to attain a maximum immediately before the glucose was used up; the fat of the organism then rapidly fell off, though no decrease was detected in the protein as estimated by Kjeldahl’s method. It therefore appeared that while growing in a medium containing a sufficiency of glucose, the organism stored fat, which was oxidised when the glucose was exhausted—the organism living at the expense of its fat and saving its protein. More recently, somewhat similar work onAspergillus niger has been reported by Terroine, Wurmser and Montané [1922 (2)], who deprived the fully grown fungus of both nitrogenous and carbon-containing foodstuffs, and found a considerable fall in the percentage content of nitrogen in the organism. Kosinski [1902 (3)] had observed that the respiratory quotient ofA .nigher on a glucose-containing medium is about 1, but falls off to 0·8 during starvation. This result, taken in conjunction with their own, led Terroine, Wurmser, and Montané to the conclusion thatA .niger uses protein as a reserve material rather than cellulose. No particular observations seem to have been made on the fat content ofA .niger . The work is not exactly comparable with ours on the Timothy Grass Bacillus, as ammonia was always present in the medium in our experiments.