STUDIES ON ther:mophilic bacteria . 



I. AEROBIC THERMOPHILIC BACTERIA FROM WATER' 



LETHE E. MORRISON and FRED W. TANNER 



Department of Bacteriology, Universitij of Illinois, Urbana 



Received for publication November 26, 1921 

 I. INTRODUCTION 



The discovery of microorganisms that are able to Uve at rela- 

 tively high temperatures (60^C. and above) has forced us to 

 change our ideas on the resistance of protoplasm to heat and to 

 admit that life is possible above the generally fixed limit of 42° to 

 45°C. The term thermophilic was probably first used by Miquel 

 (1879) to describe those organisms that grow at temperatures so 

 high as to be fatal to most microorganisms. This conception 

 seems to have been lost sight of by many more recent workers. 

 In order to have a better understanding of what the term 

 thermophilic means, a number of definitions of the term as 

 found in different texts on bacteriology are included. 



In his physiological classification of bacteria, Giltner designated 

 as thermophilic those that have a minimum temperature of 45°C., 

 optimum, 55°C. and maximum, 70°C. IMuir and Ritchie define 

 thermophilic bacteria as organisms that grow best at a tempera- 

 ture of from 60° to 70°C. Hiss and Zinsser say that thermophiUc 

 bacteria are high temperature bacteria obtained from hot springs 

 and from the upper layers of the soil. Rahn in Marshall's 

 Microbiology describes thermophiUc bacteria as extraordinary 

 organisms having their maximum between 70° and 80°C., a 

 temperature which coagulates albumin ; corresponding to the high 



' Abstracted from a thesis submitted in partial fulfillment of the requirements 

 for the degree of Master of Science in Bacteriology. Copies of the original thesis 

 are on file in the Library and Bacteriology Seminar of the University of Illinois. 



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