SELECTED PAPERS 



cutting and grinding of metals are often subject to heavy bacterial 

 growth. This growth is apparently correlated with an attack on the 

 naphthenic acids used as emulsifying agents, thus rendering the cut- 

 ting compound unfit for further use. 



Anyone who beholds the mighty plant of a modern coke industry 

 in which high temperatures and high gas pressures seem to dominate 

 the scene will tend to think this industry to be impervious to microbial 

 attack. Yet I know of an instance in which the extinguishing of an 

 oven battery has been seriously taken into consideration, because of 

 the clogging of the scrubbers in which the coal gas is washed with 

 water: this clogging was directly connected with an almost incredibly 

 rapid and profuse growth of bacteria in the water in contact with the 

 gas under a pressure of 13 atmospheres. 



Perhaps still more startling is the experience in a modern nitrogen 

 fixing plant. Here the acid-fast steel cooler in which nitric acid was 

 condensed showed serious signs of corrosion, even leading to perfora- 

 tion, after a relatively short period of use. The management of the 

 factory was initially inclined to doubt the acid fastness of the steel, 

 but on second consideration there appeared to be reason to suspect 

 the tiny bugs which had accumulated in the cooling water on the 

 other side of the steel wall. In this respect I refer to the investigations 

 of von Wolzogen Kiihr in Holland, of Thaysen, Bunker and Butlin in 

 England, and of Starkey in the U.S.A. which have thrown a clear 

 light on the active part played by sulphate-reducing bacteria in the 

 anaerobic corrosion of steel and cast-iron tubes. 



These examples should suffice to show how microbes may interfere 

 with industry. It seems more important to analyze why this inter- 

 ference leads so often to undesirable effects in human proceedings. It 

 then soon becomes clear that in most cases it is not the presence of the 

 microbes as such that is the cause of our troubles, but the fact that the 

 maintenance and proliferation of a microbial population is accom- 

 panied by chemical conversions. In other words, we have to consider 

 microbes as co-practitioners of our craft, and it is evident that the 

 leader of a chemical industry cannot tolerate 'illegal' chemistry in his 

 factory. Obviously the first command for any action is 'know thine 

 enemy', and one of the first things to be attempted should be a survey 

 of the various chemical conversions brought about by micro-organ- 

 isms, or in other words a survey of microbial metabolism. 



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