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

Abstract

Summary. The effect of C02 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. C02 10% enhanced the mycelial growth of all strains when the medium contained an appropriate constituent to mediate its effect. The effect of C02 was most clearly demonstrated at 30°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 CO;! only blastospore growth occurred. Growth in the blastospore form was more rapid in C02 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 C02 in limited nutrient conditions, a view consistent with other reported laboratory and clinical findings.

Comparative Transcript Profiling of Candida albicans and Candida dubliniensis Identifies SFL2 , a C. albicans Gene Required for Virulence in a Reconstituted Epithelial Infection Model

“…Key events and genes for epithelial colonization have been identified in C. albicans (29,52), but less is known about the factors that trigger filamentation in the RHE. CO 2 at concentrations present in the oral cavity (48) induce filamentation in C. albicans-but not in C. dubliniensis (23)-both in vitro (37) and in the RHE (14). As shown by Klengel and coworkers (14), CO 2 /HCO 3 Ϫ directly stimulates activity of adenylyl cyclase for cyclic AMP (cAMP) production and hyphal morphogenesis in C. albicans.…”

“…We then tested morphological responses to increased CO 2 , which induces hyphae in C. albicans (14,37). To detect CO 2 -specific morphogenic responses, we used a YNB medium with 0.1% glucose and supplemented with amino acids (YNBGluc-AA [see Materials and Methods]) in which the WT formed germ tubes only in 5% CO 2 and not in ambient CO 2 (Fig.…”

“…Importantly, hyphal morphogenesis in response to many stimuli is consistently slower in C. dubliniensis than in C. albicans (8,41). Some specific triggers that induce hyphal morphogenesis in C. albicans, such as increased CO 2 /HCO 3 Ϫ and growth in mammalian tissues (14,37,52), do not induce hyphae in C. dubliniensis (14,23,41). The transcriptional regulator Nrg1 has been identified as a key regulator suppressing filamentation in C. dubliniensis, and it has been suggested that this suppression of hyphal growth may partially explain why C. dubliniensis is less virulent in the human host than C. albicans (23).…”

Rfg1, a Protein Related to the Saccharomyces cerevisiae Hypoxic Regulator Rox1, Controls Filamentous Growth and Virulence in Candida albicans

“…Previous studies of Candida have implicated O 2 levels in the control of filamentous growth (24,38); a requirement for oxygen in rapid filamentous growth, almost certainly an ATP-driven process, seems logical considering that a majority of the cell's energy needs are met by oxidative phosphorylation.…”

The Cryptococcus neoformans Capsule: a Sword and a Shield

“…In Candida albicans, 5% CO 2 triggers invasive hypha formation and disease (112,184). C. neoformans also responds strongly to host levels of carbon dioxide-in this pathogen, the important phenotype is the induction of the polysaccharide capsule (77,112,199,225).…”