The Influence of Carbohydrates on Hydrogen sulphide Production byBacillus aertrycke(Mutton)

Abstract

AN important aspect of the investigation of bacterial metabolism is the study of the substrate and its changes and of the resulting products; together with an examination of the rate of change. The present report deals with the influence of certain carbohydrates in modifying the action of one species of bacteria upon the protein molecule.Hirschler (1886) found that sugars inhibited the production of indol and other phenolic bodies, and preferred the explanation that sugars were more easily decomposed than proteins. He showed that in mixed cultures proteins are not attacked when sugars are present, although the acids formed were neutralised by calcium carbonate.Smith and also Peckham (1897) concluded that non-production of indol in sugar media was due to acid formation. This seemed to be supported by the work of Glenn (1911), who found that 05 per cent. of added lactic acid prevented indol formation, and also that the presence of sugars prevented the liquefaction of gelatine. It has, indeed, frequently been stated that organisms growing on a sugar-protein medium do not form indol, liquefy gelatine nor digest casein, and that ammonia production is greatly lessened. Acid production from sugars has been put forward as an explanation for this inhibition of the production of protein decomposition products.Fischer (1915) found that neither hydrion concentration nor total acidity influenced indol production; and suggested that glucose inhibited the action of the proteolytic enzyme. Kendall, Day and Walker (1913) adopted a very similar hypothesis, in stating that "protein sparing" is not due to acids produced from sugars, but that sugars serve the energy requirements more readily than do proteins, and that the activity of the organisms is diverted from the protein to the sugar, so that protein decomposition products are found wanting. They state that the slight ammonia production, which occurs, indicates the small amount of protein decomposition necessary for structural requirements. It is generally stated that the production of acid from sugar inhibits the liquefaction of gelatine by B. proteus, but Kendall and Walker (1915) found that enzymes from this organism reacted in the presence of glucose or of organic acids as

Preparation and Properties of a Freeze-dried B.C.G. Vaccine of Increased Stability

“…from some precursor in the medium. Heap and Cadness (1924), working with Salmonella typhimurium, demonstrated that a fermentable carbohydrate, such as glucose, produced an early enhancement of growth in peptone-water culture but that prolonged incubation caused a rapid fall in the number of viable organisms. A peptone-water culture without glucose showed a fairly constant count for a long time.…”

A Method for the Study of the Formation of Volatile Sulfur Compounds by Bacteria

“…Lead and iron salts have been added directly to the culture media by various investigators (Wilson, 1923) as a qualitative and approximately quantitative test for differentiation purposes.Recently the determination of hydrogen sulfide by titration with standard iodine solution has been advocated. Heap and Cadness (1924) employed N/100 solutions of iodine, a stream of carbon dioxide being used to carry over the hydrogen sulfide. Fellers, Shostrom, and Clark (1924) recommend N/40 iodine solutions and separation of the hydrogen sulfide by means of a current of air.…”