Fungi Phycomycetes

Depending on the species, hyphae may be divided into compartments by means of septa (Eumycetes). Each septum contains a pore, which allows flow of cytoplasmic constituents from one compartment to another. The lower fungi (Phycomycetes) have aseptate (coenocytic) hyphae the mycelium is a multinucleated cell. 

A mycorrhiza (literally, fungus-root) is a symbiotic association between a fungus and a plant. Mycorrhizae occur most frequently on plant roots, but may be found on any tissue involved in uptake of elements from soil. Mycorrhizae, formed by numerous fungi in the orders Phycomycetes, Basidiomycetes, and Ascomycetes, can be divided into two broad groups those that penetrate host cells (endomycorrhizae) and those that do not (ectomycorrhizae). A few fungal species defy this neat classification, penetrating the cells of one host but not those of another. 

The fungi are classified broadly into the lower fungi, collectively known as Phycomycetes, and the higher fungi, described by the classes Ascomy-cetes, Deuteromycetes and Basidiomycetes. The classification is indistinct some taxonomists argue that the Phycomycetes are not true fungi. 

The Oomycetes, a class within the Phycomycetes, is unusual and regarded by many as being distinct from the true fungi. The taxonomic... 

Polyoxins are inhibitors of chitin biosynthesis. Chitin is a component of fungal cell walls except in Phycomycete fungi these contain cellulose as their major cell wall constituent, hence polyoxins are inactive against Plasmopara, Pythium and Phytophthora. 

Diokno-Palo, N., Palo, M. A., Cunanan, L. F. and Santos, P. S. 1979. Skim milk-coagulating activities of enzymes produced by phycomycetous fungi. Philippine J. Sci. 108, 137-151. 

As a general conclusion, it can be stated that thus far, all fungi tested, whether belonging to the Phycomycetes, the As-comycetes, or the Basidiomycetes have been found to be susceptible to certain types of tri-substituted organotin compounds. ... 

Metalaxyl is clearly fungicidal i n vitro to a variety of phycomycetous fungi. Its activity in vivo may also be enhanced by stimulation of host plant defenses including hypersensitive cell death (104), accumulation of phytoalexins such as glyceollin (121), and cal lose encasement of hyphae (122) after fungal infection of metalaxy1-treated soybeans. However, the mi vivo concentration of the compound in cell sap may be sufficient for fungitoxicity alone to account for its protective activity (123). 

Fungi can also be classified as lower (Phycomycetes) and higher (Basidiomycetes and Ascomycetes). Molds for which a sexual phase of reproduction has not yet been determined are called Deuteromycetes or Fungi Imperfecti. 

The newest active substance developed by the Rhone-Poulenc (Horriere, 1977) is ethyl hydrogen phosphonate aluminium-salt (39). Its common name is fosetyl. This fungicide is truly systemic with protectant and curative properties, primarily active against Phycomycetes fungi (Bertrand et al., 1977 Williams et al., 1977). It has been widely tested on temperate and tropical crops (Beach, 1979) and has successfully controlled many important Phytophtkora spp and downy mildew. Mixtures with... 

Certain Phycomycetes soil fungi are able to decompose carboxamides. Thus, Rhisopus japonicus metabolises the 90 per cent of carboxin to butiranilide within a three-week period (Wallnofer, 1969). 

Griseofulvin is an antifungal antibiotic. It is fungistatic to Basidiomycetes, Ascomycetes, Fungi imperfecti and certain Phycomycetes spp. (Brian, 1949). Botrytis alii fungi, on which it has a specific action, are the most sensitive. On the other hand, yeast fungi and bacteria, as well as Oomycetes from the class of Phycomycetes, are not sensitive to griseofulvin even at concentrations of 100 /ig/ml. 

Distribution and properties of GDH s in over 40 species of fungi have been reviewed by LeJohn (23) who has concluded that, whereas higher fungi of the classes Deuteromycetes, Ascomycetes, and Basidiomycetes possess two distinct enzymes, lower fungi, members of the Phycomycetes and Myxomycetes (slime molds), have only one enzyme active with NAD. However, vegetative cell homogenates of Dictyostelium discoideum possess both an enzyme that is active with NAD and NADP, and one active only with NAD 2Ji). 

GSLs are present in fungi of the most primitive class of Phycomycetes [3] as well as in the most complex Basidiomycetes [4],... 

Choline sulfate, unlike choline [43,45], has been found in all species studied [43,46] (Table VIII). These substances also occur in terrestrial fungi. However, choline sulfate does not seem to be present in phycomycetes (in [43). 

The fungi are generally sub-divided into four groups based on the structure of their sexual stages, although there is some controversy over the number. These are the Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes (Fungi Imperfecti). 

High activities have also been found in the fungi including Deuteromy-cetes, Ascomycetes, Basidiomycetes (Smith et al., 1975), and Phycomycetes (Le John and Jackson, 1968). 

Fungi of the lower orders Phycomycetes and Myxomycetes possess only one GDH enzyme which has absolute specificity for NAD. Vegetative cell homogenates of Dictyostelium discoideum, on the other hand, possess two GDH isoenzymes, one specific for NAD and one which shows dual coenzyme specificity (De Toma and Langridge, 1974). 

However, in organisms which have only one GDH enzyme, which is responsible for both ammonia assimilation and deamination of glutamate, there has been a necessity for the enzyme to evolve complex regulatory properties so that the relative rates of amination and deamination reactions can be finely controlled by the concentrations of certain metabolites, and by the energy status of the cell. This is seen in the complex regulatory properties of GDH enzymes from bovine liver and from the Phycomycetes (fungi). 

---