FUNGI

Fungi

Fungi

Introduction

All fungi are chemoorganotrophs, meaning that they lack the chlorophyll necessary to produce their own food; instead, fungi excretes extracellular enzymes that break organic material into new, simpler compounds that can then be absorbed by the fungus and used as carbon and energy sources (Orson, 2006, 62). Many fungal species have a filamentous life form embodied as hyphae; hyphae that branch, intertwine, and grow together as tufts in soil and under decaying mats of organic matter collectively constitute fungal mycelia. Some mycelial mats are easily observable with the naked eye, but other soil fungi require chemical stains and microscopes to observe.

Fungi have various reproductive strategies; all groups except the Deuteromycetes have some sexual reproduction through spores, while fungal groups that reproduce asexually produce asexual spores called conidia. Fungi colonize new areas both by the extension of hyphae—which may extend several meters from the original mycelial mat—and by spore dispersal, often over great distances (Brock, 2008, 49).

Discussion

Fungi grow in very diverse habitats, including fresh and salt water; however, most fungi are terrestrial and are commonly found in soils and on dead organic matter. Soil fungi, especially the Basidiomycetes, are instrumental in the decomposition of organic matter into simpler carbon compounds. The decay fungi are especially effective at decomposing recalcitrant (i.e., difficult to decompose) plant compounds such as cellulose and lignin. Certain fungal species are also important in the mineralization of organic compounds into inorganic nutrients and minerals that are in turn used by plants and other soil organisms.

Pathogenic fungi are responsible for the majority of agricultural diseases, and can reduce crop yields and kill plants in natural systems (Brady, 2007, 22). Many fungal pathogens of crop and noncrop plant species such as the powdery mildews (Ascomycetes), rusts (Basidiomycetes), smuts (Basidiomycetes), and blights (Ascomycetes, Oomycetes) are often transmitted by windblown spores. The fungal species Ophiostoma ulmi (syn. Ceratocystis ulmi) and Cryphonectria parasitica, which cause the tree diseases Dutch elm disease and Chestnut blight, respectively, have seriously changed the species composition of deciduous forests in the United States (Orson, 2006).

People most commonly associate microbes (“germs”) with human illness, and indeed microbes act as pathogens or parasites on a great number of humans and other animals. The effects of microbial colonization of animal tissue, however, may be positive, negative, or neutral. Hair follicles are inhabited by an array of bacteria, yeasts, and filamentous fungi. Various pathogenic bacteria cause diseases such as Stapholococcus and ...