The Minimum Growth Temperature of Obligately Thermophilic Bacteria as Influenced by Inhibitors in Complex Growth Media

Abstract

The inability of several obligately thermophilic bacteria to grow at or below 37°C in common laboratory media was shown to be caused by inhibitors present in these media. The inhibitors could be removed by extraction with chloroform and by adsorption on ion exchange resins or starch. It was concluded that they were of organic nature, probably bile acids. Four laboratory strains of Bacillus stearothcrtno‐philus grew readily at 37°C in detoxified media. With one of them (NCA 1503) growth was obtained at 34–35°C. A fresh soil isolate having a minimum growth temperature of 40°C in glucose nutrient broth grew at 30°C in this medium after the inhibitors had been removed.

Physiological and taxonomic aspects of Clostridium thermocellum

“…More recently (Ljunger, 1968) , obligate thermophilic bacteria have been reported that grow at mesophilic temperatures when inhibitory substances are removed from the growth medium. But to the knowledge of the author the work of Oates et (1961Oates et ( , 1963Oates et ( , 1964 was the first known report of a mesophile being able to grow at elevated temperatures; however, recent work by Dowden et al (1968) suggests that a mesophilic strain of Bacillus subtilis can be adapted to grow at elevated tempera tures .…”

Physiological and taxonomic aspects of Clostridium thermocellum

“…More recently (Ljunger, 1968) , obligate thermophilic bacteria have been reported that grow at mesophilic temperatures when inhibitory substances are removed from the growth medium. But to the knowledge of the author the work of Oates et (1961Oates et ( , 1963Oates et ( , 1964 was the first known report of a mesophile being able to grow at elevated temperatures; however, recent work by …”