Phylum Mucoromycota Subphylum Mucoromycotina Mucorales part 1 Terrestrial fungi
Fig. 1 RAxML phylogenetic tree of Kingdom Fungi based on the concatenated alignment of 192 conserved orthologous proteins. All branches received 100% bootstrap partitions except where noted by number above or below respective branches. Example images include: a. Rhizopus sporangium (SEM). b. Phycomyces zygospore (LM). c. Mortierella chlamydospores (SEM). d. Rhizophagus spores and hyphae (LM). e. Conidiobolus secondary (replicative) conidia forming on primary conidium (SEM). f. Basidiobolus ballistosporic conidium (SEM). g. Piptocephalis merosporangia (SEM). h. Linderina merosporangium (SEM). LM: light micrograph, SEM: scanning electron micrograph.
Mucorales Vegetative hyphae often lack septa, walls contain chitosan rather than chitin Under certain conditions may grow as a yeast cells (e.g., anaerobic, liquid culture, warm temperature) Septa are associated with reproductive structures as are rhizoids Cell wall chitin and chitosan Hyphae or yeast cells contain one to many haploid nuclei Asexual reproduction by sporangia with non-motile, sporangiospores Sporangiospores germinate to form hyphae Sexual reproduction - gametangial fusion, zygospores (formed in zygosporangium), germ sporangium Chlamydospores may be formed saprobic, parasitic on plants, animals and other fungi or mutualistic with plants Considerable industrial use, organic acids, etc.
Food Products - Tofu or sufu (Chinese cheese) A soft cheese-type product made from cubes of soybean curd using fermentation by Actinomucor elegans Tempeh A solid cake-like product from soybeans fermented with Rhizopus oligosporus
Cunninghamella - Members of this genus are often used in studies investigating the metabolism of drugs, because these species metabolize a wide range of drugs in manners similar to mammalian enzyme systems. Many species are also capable of oxidizing polycyclic aromatic hydrocarbons, a class of stable organic molecules that tends to persist in the environment and contains many known carcinogenic and mutagenic compounds. Mucormycosis is caused by common fungi frequently found in the soil and in decaying vegetation. Most individuals are exposed to these fungi on a daily basis -- but people with immune disorders may be more susceptible to infection. As such, it usually infects those who are immunocompromised.
Murcorales Moldy strawberries covered with Rhizopus mycelium. Vegetative hyphae often lack septa!
Hyphae of Mucorales with Spitzenkörper
Hyphal apical extension Extension of hyphal apex The mechanisms underlying the growth of fungal hyphae are based on cell pressure. Internal hydrostatic pressure (turgor) is one of the major forces driving the localized expansion at the hyphal tip which causes the characteristic filamentous shape of the hypha. Turgor and pressure have additional roles in hyphal growth, such as causing the mass flow of cytoplasm from the basal mycelial network towards the expanding hyphal tips at the colony edge.
Asexual reproduction Hyphae with haploid nuclei Sexual rerproduction
Asexual Reproduction Reproduce asexually by producing sporangiospores within a sporangium. sporangiophore hypha Macrosporangia rhizoids Sporangiospores inside sporangial wall columella microsporangia
Macrosporangia yellow pigment is β-carotene
Macrosporangia response to light and gravity gravity 10-12 hrs. light The Macrosporangia of Phycomyces blakesleeanus has been investigated for the variety and sensitivity of its responses to light, particularly the phototropism (response to blue light). Other light responses investigated in detail are the regulation of sporangiophore development and the regulation of the biosynthesis of the pigment beta-carotene. In addition, the Phycomyces sporangiophore reacts to a variety of environmental stimuli, including gravity, touch, wind, and the presence of nearby objects by changing the speed and direction of growth.
Asexual reproduction Hyphae, multiple haploid nuclei Sexual reproduction
Mating system heterothallic or homothallic - + Phycomyces blakesleeanus Cunninghamella homothallica
When compatible mycelia of Phycomyces blakesleeanus meet, individual hyphae establish intimate contact, developing finger-like outgrowths and seeming to grapple with one another. This lets them exchange chemical signals which establish that they are indeed sexually compatible. Then the two hyphae grow apart again, only to loop back, swelling as they approach each other, and finally meeting head-on. They have become gametangia, which fuse when their tips touch. Note that there isn't any sexual differentiation in size or shape here: since we can't call them male and female, we simply label the mycelia '+' and '-'
Sexual Reproduction Sexual spores are called zygospore(s) contained within a zygosporangium A. F. Blakeslee in 1904 discovered that many Mucorales are heterothallic, that is, they require two compatible partners to produce sexual spores. Sex hormones are known to facilitate sexual reproduction among some zygomycetes. For example, hyphae of Mucor species with + and - mating strains are known to produce volatile pheromones (+ strain yields trisporates; - strain yields trisporins) that diffuse through the air. Volatiles stimulate progametagia production and the synthesis of carotene (a precursor for trisporic acid) and trisporic acid. A positive feedback mechanism is formed between the two compatible strains leading to physical contact of progametagia and sexual reproduction. Heterothallism (Gr. heteros = different from, thallos = shoot; the condition of being self-sterile, requiring a partner for sexual reproduction) and homothallism (Gr. homos = alike, thallos = shoot; the condition of being self fertile; able to reproduce sexually without a partner) exhibited among species of Mucorales.
Sexual Compatibility Formation of Trisporic acid trisporate trisporin