The Basics of Mycology & The Fungi
For educational purposes; quote cited references when available--
The Bacteria: Monera Schizomycophyta1
This group of organisms is discussed here because of the Actinobacteria (Actinomycetales), which have been considered as an intermediate group between fungi and bacteria. Bacteria have traditionally been difficult to classify because of their ability to mutate rapidly and their morphological similarities. Biochemical instead of morphological means of identification has been deployed more successfully.
The Class Schizomycetes, Order Eubacteriales are the true bacteria. They are non-filamentous, non-photosynthetic structures with heavy cell walls. They include the bacilli, cocci and spirilla. [See PLATE 4 for flagella arrangements]
Spirochaetales have long cells.
Myxobacteriales are the slime bacteria. In class rods are distributed in a common, mucilaginous mass. Although they are individual organisms, the whole mass behaves as a unit. The mass (sheet) concentrates in one area, assumes a stalk shape and then branches in some species.
Actinomycetales are the ray bacteria. They appear to bridge the gap between bacteria and true fungi. In acid soils the population density is relatively low, as the optimum pH for growth is between pH 7 & 8. Some genera, e.g., Streptomyces and Actinomyces, are able to decompose many substances. Phages have been known to attack this group, but no phages are known for the fungi. The mycelium ranges between 0.7 and 1.0 microns in diameter.
Characteristics that make the Actinomyctales similar to fungi are a branching aerial mycelium, the production of conidia in some species and motile spores. They are similar to bacteria in the diameter of their spores and filaments, many reproduce by rods, there is an absence of sexual reproduction, a flagella may be present, they are attacked by phages and they are not effectively attacked by antibiotics.
In the family Mycobacteriaceae the mycelium is rudimentary or absent. In these acidfast organisms there is a tendency toward filament formation and branching. A representative Genus is Mycobacterium. Some diseases caused by members of this family are leprosy and tuberculosis.
The family Actinomycetaceae has a mycelium that septates, and individual cells break away to form Arthrospores that are aerial and possess no conidia. The Genus Actinomyces is anerobic or microaerophilic, parasitic and not acidfast, while the Genus Nocardia is aerobic, partially acidfast or non-acidfast. Two species of Actinomyces act as parasites on animals causing Actinomycoses (lumpy jaw). The mycelium radiates from the site of infection in a characteristic manner. The species develop anaerobically. [See PLATE 5 for life cycle].
The genus Nocardia, with over 43 species, is aerobic, has an aerial mycelium that breaks up early in the developmental cycle and uses paraffin as a carbon source. The disease Madura Foot is associated with this group.
In the Streptomycetaceae an aerial mycelium is common and conidia are formed. The Genus Streptomyces has over 150 species, thirty percent of which are used for antibiotics production. This is different from the Actinomyces where no antibiotics are produced. Streptomyces plays an important role in the ecology of microflora. Streptomyces scabies (has been referred to as Actinomyces scabiea in the early literature) attacks potato causing the common potato scab disease. It may be controlled in acid soil. The non-septate mycelium shows profuse branching.. Apices may form spirals on the conidiopores that then form septae and finally break-up to form rod-like conidia or catenulate conidia. [See PLATE 5 for life cycle and PLATE 6 for examples of several species]].
In the Genus Micromonospora, which is widely distributed in lakes and in lake mud, there is a bulb-like cell at the top of the conidiophore.
Please see PLATE 6 for examples of Actinomycetales cultures on agar and the following for additional structures:
Plate 4 = Flagella Arrangement -- Eubacteriales
Plate 5 = Life Cycles – Actinomycetales
Plate 64 = Bacterial cell arrangements: Micrococcus, Diplococcus, Streptococcus, Staphylococcus, Sarcina,
Microbacillus, Diplobacillus, Streptobacillus, Microspirillum & Diplospirillum.
Plate 65 = Capsulated cells of bacteria.
Plate 66 = Flagella arrangements: Monotrichous, Lophotrichous, Amphitrichous & Peritrichous.
Plate 67 = Life Cycle -- Streptomyces sp.