Kingdom Fungi

The kingdom Fungi is a large, diverse group of organisms that range in size from simple yeast cells of less than 5 μm in diameter, up to complex fruiting bodies that may reach 1 m in size, and to diffuse colonial organisations that are reported to exist over areas of more than 800 Ha (Anon, 1992; Barnard, 2000).

The word ‘fungus’ is used to cover a huge range of shapes and types of cellular, coenocytic, spherical, filamentous, simple, complex, mobile, immobile, parasitic, symbiotic, saprophytic, microscopic, and macroscopic organisms, which makes any attempt at definition difficult. Fungi commonly are defined as “chlorophyll-lacking eukaryotes, and hence heterotrophic, with the following characteristics: uni- or multinucleate, nutrient absorption, typically chitinous cell walls, meiosis takes place within a zygote, and lysin synthesis takes place via adipicamine acid” (Alexopoulos et al., 1996).

Fungi contain five true phyla including Chytridiomycota, the Zygomycota, the Ascomycota, the Basidiomycota, and Glomeromycota. The Deuteromycota is an informal group of unrelated fungi that all share a common character – they use strictly asexual reproduction.

To name a few – the appearance of black spots on bread left outside for some days, the mushrooms and the yeast cells, which are commonly used for the production of beer and bread are also fungi. They are also found in most skin infections and other fungal diseases.

If we observe carefully, all the examples that we cited involve moist conditions. Thus, we can say that fungi usually grow in places which are moist and warm enough to support them.

Characteristic features of Kingdom Fungi • Eukaryotic • Cell walls are made up of chitin a strong but fl exible polysaccharide. • They are absorptive and heterotrophs - many of them secrete extra cellular enzymes which aid in the breaking down of complex molecules into small molecules. • Different species live as decomposers, parasites or mutualistics. • Few are unicellular, others forming multicellular fi laments called hyphae . • Septa can be found in hyphae. (division of hyphae into cells by septa – cross walls). • Septum has a hole which enables the movement of mitochondria, ribosomes, nuclei etc. • Fungi lack septa are known as coenocytic fungi (with many nuclei) • Fungal hyphae produce mycelium • Some fungi produce haustoria ( to penetrate and absorb or exchange nutrients between plants and the fungi) • Multicellular fungi produce mycelia. ( a network of branched hyphae adapted for absorption of nutrition) • They show sexual and asexual reproduction. • They produce spores.

Characteristic features of Phylum Chytridiomycota

e.g.: Chytridium • Aquatic or terrestrial . • Some are decomposers while others are parasitic.

Multicellular or unicellular when multicellular it is coenocytic. • They produce zoospores which are fl agellated. • Cell walls are made up of chitin. • Some of them form colonies with hyphae while others exit as single spherical cell.

Characteristic features of Phylum Zygomycota

e.g. Mucor , Rhizopus • Most of them are saprotrophs and some of them are parasites or commensals. • Mycelium is coenocytic and aseptate. Septa found only where reproductive cells are formed. • Asexual reproduction: Produce sporangia in which genetically identical haploid spores are produced. Also by endospores produced in sporangia. • Sexual reproduction: A Zygosporangium is produced which is a sturdy structure produced by plasmogamy and karyogamy. Zygosporangium is resistant to unfavorable environmental conditions. o Zygosporangium is a multinucleated structure which is resistant to drying and freezing. o They are metabolically inactive in adverse environmental conditions. • Zygosporangium produces genetically diverse haploid spores when environmental conditions are favourable.

Characteristic features of Phylum Zygomycota

e.g. Mucor , Rhizopus • Most of them are saprotrophs and some of them are parasites or commensals. • Mycelium is coenocytic and aseptate. Septa found only where reproductive cells are formed. • Asexual reproduction: Produce sporangia in which genetically identical haploid spores are produced. Also by endospores produced in sporangia. • Sexual reproduction: A Zygosporangium is produced which is a sturdy structure produced by plasmogamy and karyogamy. Zygosporangium is resistant to unfavorable environmental conditions. o Zygosporangium is a multinucleated structure which is resistant to drying and freezing. o They are metabolically inactive in adverse environmental conditions. • Zygosporangium produces genetically diverse haploid spores when environmental conditions are favourable.

Characteristic features of Phylum Basidiomycota

e.g. Agaricus, Puffballs, Shell fungi • They are Terrestrial. • They are major decomposers and some are symbionts. • Filamentous with septae and dikaryotic. • Mycelium is the dominant stage of the life cycle. • They produce fruiting bodies called basidiocarps during sexual reproduction. Produce basidia on the gills of the basidiocarp. • Produce basidiospores on basidium and exogenous