Effect of carbon dioxide on the growth and form of Candida albicans

The effect of CO2 on the growth of 31 strains of Candida albicans was studied in serum and in a defined medium containing urea, ammonium chloride, asparagine, glutamine or acetamide as the nitrogen source. CO2 10% enhanced the mycelial growth of all strains when the medium contained an appropriate constituent to mediate its effects. The effect of CO2 was most clearly demonstrated at 30 degrees C when it induced a characteristic growth form consisting of a single swollen blastospore giving rise to a long, unbranched mycelial tube with few secondary blastospores; in atmospheric concentrations of CO2 only blastospore growth occurred. Growth in the blastospore form was more rapid in CO2 10% than in air. Bicarbonate ions had no effect on mycelium formation. The result suggest that the induction of germ-tubes and mycelial growth is essentially a physical phenomenon caused by the intracellular accumulation of CO2 in limited nutrient conditions, a view consistent with other reported laboratory and clinical findings.