THERMOPHILIC BACTERIA

Abstract

True thermophilic bacteria are those that grow at temperatures above the maximum temperature for the great majority of bacteria , especially the pathogenic forms. The maximum temperature for the pathogenic bacteria is about 45°C. Their optimum temperature is about 37.50C. The true thermophiles show no growth, or only very feeble growth, below 40 to 450C. Their development requires temperatures above 500C., and some are able to develop at a temperature of 800C., though most abundant growth is shown at 60 to 70°0. A group of facultative thermophilic bacteria has been discovered which develop at room temperature, about 200C., and have their optimum temperature at about 500C., and their maximum temperature at about 600C. In this group belong some of the well-known spore-forming soil organisms. Two distinct types of true thermophilic bacteria have been found in the laboratory, viz., spore-forming and non-spore-forming rods, and thread forms belonging in the class of Nocardia. Most of the thermophilic bacteria studied belonged to the spore-forming class and these varied in size of rods, size and location of the spores, and to a less degree in their biological characters. The sources from which these bacteria are obtained indicate that this group is widely distributed in nature. They were found in the dust collected on apparatus in the laboratory, on clothes, in soil, in sewage, in the gastro-intestinal contents and feces of rabbits and guinea-pigs, on grain and in horse manure.