Studies of the metabolism of the strict anaerobes (genus: Clostridium )

Abstract

OUR knowledge of the metabolism of the spore-forming anaerobes has until now been rather restricted. This is due in part to the fact that from the biochemical point of view little attention has been given to this genus. This is regrettable, since this group of microorganisms has the unique property of being able to live and multiply actively under anaerobic conditions with proteins as the only source of energy. A study of the metabolism of these organisms, therefore, may yield valuable information on protein metabolism in general. Previous investigations consisted mainly in the detection of dissimilation products produced by members of this group of organisms. Later investigators, especially Fildes, Knight and Pappenheimer [1933-35] made useful contributions on a broader scale, dealing mainly with growth studies. The most fundamental discovery, however, was made by Stickland [1934; 1935] who showed that a cell suspension of Cl. sporogenes is able to activate some amino-acids as hydrogen acceptors and others as hydrogen donators, thus enabling an intermolecular reaction between two amino-acids to occur, one being oxidized, the other reduced. This study of coupled reactions between pairs of amino-acids, brought about by a suspension of Cl. sporogenes, was continued and enlarged by Woods [1936]. It is striking that among the many naturally occurring amino-acids there is such a limited number that can be used either as hydrogen donators or acceptors. It has been shown, for instance, that tryptophan belongs to the "essential" amino-acids for the growth of Cl. sporogene8; but, so far as can be deduced from previous work, this amino-acid plays no role as acceptor or donator. The question is whether or not the " Stickland reaction" is the only reaction which provides Cl. sporogenes with the necessary energy. It has also been shown that bacteria belonging to the facultative anaerobic group are able to activate as hydrogen donators many biochemically interesting compounds, such as alcohol, formic acid, succinic acid, glucose etc. The work of Stickland, on the other hand, suggests that in the case of Cl. spjorogenes there are certain amino-acids that can be activated as hydrogen donators (or acceptors), while non-amino-acids do not seem to play any important role in this respect. Nevertheless, Cl. sporogenes actively ferments certain carbohydrates and, since a correlation between fer-mentability of sugars and their suitability to act as powerful hydrogen donators is always found, one wonders why glucose is not a better hydrogen donator. This paper presents information on the conditions under which various substrates act as hydrogen donators, and the influence of different factors involved, in the metabolism of the anaerobes, particularly Cl. 8porogenes. It (437) 28-2