Bacterial oxidations by molecular oxygen

Abstract

IN recent studies much attention has been directed towards bacterial oxidations in which compounds have been oxidised at the expense of reducible dyes, nitrates, fumarates, etc.It is obvious however that for any organisms growing aerobically the most important hydrogen acceptor is molecular oxygen and that consequently a study of aerobic oxidations is essential if a true picture of the normal life of the cell is to be obtained.The power to effect the oxidation of their own cell material by molecular oxygen was shown by Callow [1924] to be common to aerobes and facultative anaerobes; this was demonstrated by measuring the oxygen uptake of washed bacteria suspended in buffer solution in a Barcroft manometer; organisms in these conditions take up 5 to 25 cc. of oxygen per g. of dry cell per hour; two organisms only amongst those examined were practically lacking in this faculty, viz.B. sporogenes, the only strict anaerobe reported on, and S. acidi lactici, a facultative anaerobe resembling the strict anaerobes in possessing no catalase.It is obvious that many aerobes and facultative anaerobes possess the power of oxidising not only the simple carbohydrates but also their fermenta- tion products since aerobic growth is known to occur on lactate, acetate, succinate, glycerol, etc. where these form the only source of carbon [Braun and Cahn-Bronner, 1922; Stephenson and Whetham, 1924].In the course of the present inquiry we have confined ourselves chiefly to oxidations by B. coli, though experiments have also been carried out with B. alkaligenes and with B. sporogenes; we have sought to discover (1) the degree of oxidation sustained by glucose and some of its fermentation products, viz.lactate, acetate, formate and ethyl alcohol, in conditions highly favourable to aerobic oxidation; (2) the state of the organisms responsible for the process, i.e. whether they be living or dead, and if the former whether multiplying, at rest or dying off.