Genetics of Fungi Pathogenic for Man

Abstract

Great strides have been made in research on fungi pathogenic to man and animal during the last three decades, but little progress has been made in the genetics of these microorganisms. The principal reason for such a delay in genetic research is that mechanisms for genetic recombination were not known to exist in most of the pathogens.¹ It was not until the early part of the last decade that the parasexual cycle in Aspergillus fumigatus² and heterothallism in several ringworm fungi were discovered.^3-8 The reports of heterothallism in dermatophytes stimulated medical mycologists to search for the perfect state in systemic pathogens. Within the last 5 years, heterothallism has been discovered in Blastomyces dermatitidis, Histo-plasma capsulatum, and Geotrichum candidum.^9-11 Although for the last 10 years steady progress has been made employing these fungi as genetic tools, our knowledge of the genetics of human pathogenic fungi is fragmentary compared with what is known about the saprophytes and plant pathogens. This review is restricted to the results of recent genetic studies on true fungi pathogenic to man and animals. Although pathogenic fungi, by broad definition, might include those producing poisonous effects upon ingestion and those which cause disease only rarely and under special circumstances, this review is devoted only to those fungi generally recognized as pathogens for man. An understanding of the basic principles of mycology and genetics is assumed.