Plant roots are tentacles of life for plants. For molds (filamentous fungi) it is all about the hyphae. Hyphae are nourishment, anchoring, and growth tubes of molds. Hyphae stretch, reach and grow at their tips, as do roots and stems. All growth occurs at the tips. The mold tips extend straight, sometimes bend left, sometimes right, and often, they send out new, side branches. All this activity generates the familiar mold. A mold is a mass of these hyphae. Usually, some filaments change and modify into structures to make reproductive spores that can germinate to make more mold. The hyphae deserve a closer look.
Hyphae, Microscopic Features and Chitin Cellulose Biochemistry
Hyphae are simple on first viewing. Closer inspection and analysis reveal more.
There are narrow (thin) hyphae and broad (wide) hyphae. These two main types of hyphae are based on diameter. The narrow hyphae, about 2-3 micrometers in diameter, are characteristic of Ascomycota and Basidiomycota, two of the four fungal phyla. Narrow hyphae are seen among many imperfect fungi (Deuteromycota, these fungi with no mating phase and no special ascospores, basidiospores or zygospores). In summary, most fungi, have narrow hyphae. These narrow hyphae also have regular crosswalls.
Broad hyphae are characteristic of Zygomycota. Fungi of genera like Absidia, Mucor and Rhizopus are representative of this phylum. The hyphae are 3–7 micrometers in diameter and crosswalls are infrequent and distant from one another. The hyphae of these fungi are truly coenocytic, or multinucleate, with many nuclei seen within walled sections of the hyphae.
Biochemically, the hyphae vary. Most fungi have walls of chitin and glycomannan-protein complexes. The narrow-walled fungi are typically of these types. Chitin complex walls are tough and resilient. Chitin also forms the exoskeleton of insects. Therefore, biochemically the skin of fungi and insects share a feature, chitin. Chitin is N-acetylglucoseamine (glucose with attached amino and acetyl groups) linked together in long chains and the glycomannan-proteins provide more strength and stability. Some of the fungal wall proteins are enzymes (protein catalysts) embedded in the cell walls.
Zygomycete hyphae are composed mainly of cellulose, also found in plant cell walls. Cellulose is glucose chemically linked in long chains (polyglucose or glucans).
Hyphal Color is Helpful for Mold Identification
The natural color of mold hyphae is another useful feature that helps in identification and placement of fungi. Most molds have clear or hyaline hyphae. Some molds have darker hyphae, pigmented by melanin. These fungi are termed dematiaceous fungi. Dematiaceous molds with their dark hyphae invariably form dark spores. These features further help determine the kind or variety of mold that is present. Mold sporulation, and the resulting spores, help in the final identification of a mold to its genus and species levels. Spores have characteristic shapes, sizes and markings.
Mycology of Hyphae Has Value in Pathology, Forensics Disease Analyses
Features of mold hyphae are useful and helpful for diagnosis of disease and causes of death. Pathologists and forensic specialists in their analyses of diseases and death make good use of the character of mold hyphae. In the photos (see below) the hyphae of Mucor and Rhizopus (zygomycetes) and Aspergillus are shown in stained tissue specimens. Note that hyphae of Aspergillus are narrow . The zygomycete hyphae are broad. Click to enlarge each picture and see the frequent crosswalls in aspergillosis and infrequent, rarer crosswalls in zygomycosis.
The hyphae of the molds contain useful information and reveal much about molds.
Read and see more about molds and yeasts: Importance and Significance of Molds and Yeasts
Sources
J.G. Black. Microbiology, Principles and Explorations. 1999. John Wiley & Sons, Inc., New York. 786 pp.
Campbell, N.A., L.G. Mitchell, and J.B. Reece. 2000. Biology, Concepts and Connections. Addison Wesley Longman, Inc. , San Francisco. 809pp
Tortora,G.J., B.R. Funke, and C.L. Case. 2001. Microbiology An Introduction.7th ed., Benjamin Cummings / Addison Wesley Longman, Inc. San Francisco 887pp
Donald Reinhardt - Think, read, write & live well always. DJR has a PhD in Biology/Microbiology & is a Fellow & Diplomate, ASM Amer Acad Micro.
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