GROWTH OF ARTHROBACTER CITREUS AT AN ELEVATED TEMPERATURE: II. PROMOTION BY METALLIC IONS

Studies were undertaken to elucidate factors which promote growth of Arthrobacter citrem on nutrient agar at 37 °C. It was shown that nutrient agar was not actively inhibitory to A. citreus at this temperature. In nutrient medium, neither yeast extract, Casamino acids, nor fermentable sugars promoted growth at 37 °C. However, the ash of trypticase soy broth when added to nutrient broth supported growth at 37 °C. Na+and K+were found to have a similar growth-promoting effect. Mg++, Ca++, and Fe+++had no activity while Mn++was inhibitory. Buffered cell-suspensions of A. citreus showed a higher rate of leakage of ultraviolet-absorbing (260 mμ) materials at 37 than at 25°C. It appears that cell lysis and release of intracellular materials occur at 37 °C. Data from paper chromatographic and tracer techniques suggested that these released substances are nucleotides.