Different types of molecular markers are available for use in evolutionary and population studies of microscopic fungi. These approaches have proved their merits and have been successfully applied to a wide range of fungal species belonging in the Ascomycetes and Basidiomycetes. Species in the class Zygomycetes have been rather neglected from this aspect. This review discusses the information available from investigations of the genotypic variability in this group of fungi.
Authors:Gyöngyi Lukács, M. Takó, and Ildikó Nyilasi
The separation of chromosome-size DNA molecules by pulsed-field gel electrophoresis (PFGE) has become a well-established technique in recent years. Although it has very wide-ranging applications, it made a real breakthrough for fungal genome analysis. Because of the small size of fungal chromosomes, their investigation was not possible earlier. Different PFGE approaches allowed the separation of DNA molecules larger than 10 megabase pairs in size, and electrophoretic karyotypes for numerous previously genetically uncharacterized fungal species could be established. This review discusses the applicability of these electrophoretic karyotypes for the investigation of genome structure, for strain identification and for species delimitation.
Authors:Ildikó Nyilasi, T. Papp, M. Takó, Erzsébet Nagy, and Cs. Vágvölgyi
Iron is an essential nutrient for most organisms because it serves as a catalytic cofactor in oxidation-reduction reactions. Iron is rather unavailable because it occurs in its insoluble ferric form in oxides and hydroxides, while in serum of mammalian hosts is highly bound to carrier proteins such as transferrin, so the free iron concentration is extremely low insufficient for microbial growth. Therefore, many organisms have developed different iron-scavenging systems for solubilizing ferric iron and transporting it into cells across the fungal membrane. There are three major mechanisms by which fungi can obtain iron from the host: (a) utilization of a high affinity iron permease to transport iron intracellularly, (b) production and secretion of low molecular weight iron-specific chelators (siderophores), (c) utilization of a hem oxygenase to acquire iron from hemin. Patients with elevated levels of available serum iron treated with iron chelator, deferoxamine to remedy iron overload conditions have an increased susceptibility of invasive zygomycosis. Presumably deferoxamine predisposes patients to Zygomycetes infections by acting as a siderophore. The frequency of zygomycosis is increasing in recent years and these infections respond very poorly to currently available antifungal agents, so new approaches to develop strategies to prevent and treat zygomycosis are urgently needed. Siderophores and iron-transport proteins have been suggested to function as virulence factors because the acquisition of iron is a crucial pathogenetic event. Biosynthesis and uptake of siderophores represent possible targets for antifungal therapy.
Authors:Á. Csernetics, Zs. Péteri, B. Linka, and M. Takó
Mucor piriformis, Gilbertella persicaria and the members of the Rhizopus genus (especially R. stolonifer and R. oryzae) are the most important agents of post-harvest decay among the fungi belonging in the order Mucorales (Zygomycetes). Epidemiological studies and control of post-harvest losses require reproducible methods with which to distinguish and characterize the isolates. This review summarizes the available information regarding the genetic and physiological variability, strain typing and taxonomy of this fungal group.
Authors:M. Takó, Elvira Farkas, Szabina Lung, Judit Krisch, Cs. Vágvölgyi, and T. Papp
Extracellular β-glucosidase activity of 94 strains, representing 24 species of the genera
Gilbertella, Mucor, Rhizomucor
was evaluated in submerged culture and under solid state fermentation on wheat bran.
G1 isolate showed the highest activity (70.9 U ml
) followed by other
(58.6–59.0 U ml
isolates (29.2–42.0 U ml
). Optimum temperature for enzyme production was 25 °C for
, and 30 °C for
strains. Enzymes of
strains proved to be thermotolerant preserving up to 92.8% residual activity after heating to 75 °C in the presence of cellobiose substrate. Enzymes of
chibinensis, R. miehei
strains were activated at acidic condition (pH 4). Glucose was a strong inhibitor for each fungal β-glucosidase tested but some of them showed ethanol tolerance up to 20% (v/v). Ethanol also activated the enzyme in these strains suggesting glycosyl transferase activity.