The two studies are reported by Joseph Heitman and colleagues at Duke University Medical Center and by Fritz Mühlschlegel of the University of Kent, Jochen Buck at Cornell University, and their collaborators.
How organisms sense and respond to CO2 at the cellular level is not fully understood, but it is of great importance in understanding the biology of microbes, plants, and animals alike. For example, CO2 levels govern the detection of prey by female mosquitoes, control respiration in mammals, and of course play a critical regulatory role in photosynthesis in algae and plants; in addition, CO2 sensing and transport are involved in many cellular processes and virulence attributes of diverse pathogenic bacteria and fungi--in both B. anthracis, which causes Anthrax, and C. neoformans, which causes meningitis, CO2 induces the production of sugar-based capsules that surround and protect the invading cell from the host during infection.
In their new work, Mühlschlagel and colleagues studied the function of CO2 sensing in two major human fungal pathogens, C. albicans and C. neoformans. Both cause life-threatening, invasive infections in immunocompromised patients--for example, those infected with HIV or undergoing bone-marrow transplantation. The two fungi, which are distantly related in evolution, have different attributes governing their virulence in humans. For C. albicans, a transition between different morphological forms ("yeast" and "filamentous" forms) plays a major role,