Zygospore Production Research Articles

Mooraboolomyces wintlei gen. & sp. nov. from Victoria, Australia

A new genus and species in the Mucoromycota, Mooraboolomyces wintlei, was isolated into culture from leaf litter from a national park in Victoria, Australia, and is described. The strain reproduced asexually to form sporangia and sporangiospores, with no production of zygospores, and sequencing of its genome and analysis supported a heterothallic mode of reproduction. Phylogenetic analyses using five DNA regions placed the strain within the Mucorales and Mucoraceae, clearly distinct from previously described genera. This represents the second genus in this phylum that has been identified from Australia and that is currently unique to this country.

The forgotten world of subaerial desmids (Zygnematophyceae) in the Atlantic Forest, southeast Brazil

Although desmids (Zygnematophyceae) are widely distributed, their diversity in subaerial environments remains little known and explored. Subaerial algae live above the soil in a thin water film, directly exposed to the air. Desmids possess specific strategies to face environmental stress, such as mucilaginous sheaths that enable them to adhere to the substrate and protect the cells against desiccation. Also, zygospore production may be a strategy to survive. We conducted a taxonomic survey of the subaerial desmids in the Atlantic Forest biome (Rio de Janeiro city and other municipalities in the state of Rio de Janeiro). Briefly, we analyzed their strategies to resist sudden environmental changes, especially desiccation, a common condition in this environment. From 2006 through 2008, 100 samples were taken from natural and artificial vertical wet surfaces and tree bark. The material collected was identified based on morphological and metric characteristics of the vegetative and reproductive phases of the life cycle. We identified 57 species, varieties, and taxonomic formae, distributed in 12 genera, 2 orders, and 4 families. The study revealed that most subaerial algae were previously reported for Europe and North and South America. From the total taxa, 12% are reported for the first time for Brazil and 14% for South America. Even though subaerial environments are subject to stressful conditions, only three of the 57 taxa showed adaptive structures such as thick mucilage envelopes, spores, or zygospores.

Modification of Sexual Development and Carotene Production by Acetate and Other Small Carboxylic Acids in Blakeslea trispora and Phycomyces blakesleeanus

In Phycomyces blakesleeanus and Blakeslea trispora (order Mucorales, class Zygomycetes), sexual interaction on solid substrates leads to zygospore development and to increased carotene production (sexual carotenogenesis). Addition of small quantities of acetate, propionate, lactate, or leucine to mated cultures on minimal medium stimulated zygospore production and inhibited sexual carotenogenesis in both Phycomyces and Blakeslea. In Blakeslea, the threshold acetate concentration was <1 mmol/liter for both effects, and the concentrations that had one-half of the maximal effect were <2 mmol/liter for carotenogenesis and >7 mmol/liter for zygosporogenesis. The effects on Phycomyces were similar, but the concentrations of acetate had to be multiplied by ca. 3 to obtain the same results. Inhibition of sexual carotenogenesis by acetate occurred normally in Phycomyces mutants that cannot use acetate as a carbon source and in mutants whose dormant spores cannot be activated by acetate. Small carboxylic acids may be signals that, independent of their ability to trigger spore germination in Phycomyces, modify metabolism and development during the sexual cycle of Phycomyces and Blakeslea, uncoupling two processes that were thought to be linked and mediated by a common mechanism.

Effects of chemical components and nitrogen sources on zygospore development in Phycomyces blakesleeanus

We examined the effects of chemical components and nitrogen sources on zygospore development, using 62 different ingredients based on Sutter's synthetic medium SI, which has been widely used for studies of sexual physiology in Phycomyces . An increase of inorganic microelements such as ZnSO 4 , NaMoO 4 and CaCI 2 promoted an increase in the number of zygospores per unit area. Glutamate (Glu) contained in SI as the sole nitrogen source was indispensable for sexual development, and replacement of Glu with NH 4 + (Am) strongly inhibited it, mainly because of growth inhibition. However, zygospore production was enhanced 1.8-fold by equivalent amounts of both Glu and Am as compared with Glu alone. A newly developed medium, mSI+Am, enriched with Am and the above-mentioned effective microelements doubled the number of zygospores formed per unit area (density), compared with Sutter's original SI, and increased both the density and the weight (volume) of zygospores, 1.6- and 2-fold, respectively, compared with potatodextrose- agar medium enriched with yeast extract and casitone (PDAYC). Sexual stimulation by mSI+Am was also observed in the mating of a pair of β-carotene-deficient mutants. Methionine sulfoxime, an inhibitor of glutamine synthetase, strongly inhibited the progress of mating without significant growth inhibition.

Zygomycetes in human disease.

The Zygomycetes represent relatively uncommon isolates in the clinical laboratory, reflecting either environmental contaminants or, less commonly, a clinical disease called zygomycosis. There are two orders of Zygomycetes containing organisms that cause human disease, the Mucorales and the Entomophthorales. The majority of human illness is caused by the Mucorales. While disease is most commonly linked to Rhizopus spp., other organisms are also associated with human infection, including Mucor, Rhizomucor, Absidia, Apophysomyces, Saksenaea, Cunninghamella, Cokeromyces, and Syncephalastrum spp. Although Mortierella spp. do cause disease in animals, there is no longer sufficient evidence to suggest that they are true human pathogens. The spores from these molds are transmitted by inhalation, via a variety of percutaneous routes, or by ingestion of spores. Human zygomycosis caused by the Mucorales generally occurs in immunocompromised hosts as opportunistic infections. Host risk factors include diabetes mellitus, neutropenia, sustained immunosuppressive therapy, chronic prednisone use, iron chelation therapy, broad-spectrum antibiotic use, severe malnutrition, and primary breakdown in the integrity of the cutaneous barrier such as trauma, surgical wounds, needle sticks, or burns. Zygomycosis occurs only rarely in immunocompetent hosts. The disease manifestations reflect the mode of transmission, with rhinocerebral and pulmonary diseases being the most common manifestations. Cutaneous, gastrointestinal, and allergic diseases are also seen. The Mucorales are associated with angioinvasive disease, often leading to thrombosis, infarction of involved tissues, and tissue destruction mediated by a number of fungal proteases, lipases, and mycotoxins. If the diagnosis is not made early, dissemination often occurs. Therapy, if it is to be effective, must be started early and requires combinations of antifungal drugs, surgical intervention, and reversal of the underlying risk factors. The Entomophthorales are closely related to the Mucorales on the basis of sexual growth by production of zygospores and by the production of coenocytic hyphae. Despite these similarities, the Entomophthorales and Mucorales have dramatically different gross morphologies, asexual reproductive characteristics, and disease manifestations. In comparison to the floccose aerial mycelium of the Mucorales, the Entomophthorales produce a compact, glabrous mycelium. The asexually produced spores of the Entomophthorales may be passively released or actively expelled into the environment. Human disease with these organisms occurs predominantly in tropical regions, with transmission occurring by implantation of spores via minor trauma such as insect bites or by inhalation of spores into the sinuses. Conidiobolus typically infects mucocutaneous sites to produce sinusitis disease, while Basidiobolus infections occur as subcutaneous mycosis of the trunk and extremities. The Entomophthorales are true pathogens, infecting primarily immunocompetent hosts. They generally do not invade blood vessels and rarely disseminate. Occasional cases of disseminated and angioinvasive disease have recently been described, primarily in immunocompromised patients, suggesting a possible emerging role for this organism as an opportunist.

Zygomycetes in Human Disease

The Zygomycetes represent relatively uncommon isolates in the clinical laboratory, reflecting either environmental contaminants or, less commonly, a clinical disease called zygomycosis. There are two orders of Zygomycetes containing organisms that cause human disease, the Mucorales and the Entomophthorales. The majority of human illness is caused by the Mucorales. While disease is most commonly linked to Rhizopus spp., other organisms are also associated with human infection, including Mucor, Rhizomucor, Absidia, Apophysomyces, Saksenaea, Cunninghamella, Cokeromyces, and Syncephalastrum spp. Although Mortierella spp. do cause disease in animals, there is no longer sufficient evidence to suggest that they are true human pathogens. The spores from these molds are transmitted by inhalation, via a variety of percutaneous routes, or by ingestion of spores. Human zygomycosis caused by the Mucorales generally occurs in immunocompromised hosts as opportunistic infections. Host risk factors include diabetes mellitus, neutropenia, sustained immunosuppressive therapy, chronic prednisone use, iron chelation therapy, broad-spectrum antibiotic use, severe malnutrition, and primary breakdown in the integrity of the cutaneous barrier such as trauma, surgical wounds, needle sticks, or burns. Zygomycosis occurs only rarely in immunocompetent hosts. The disease manifestations reflect the mode of transmission, with rhinocerebral and pulmonary diseases being the most common manifestations. Cutaneous, gastrointestinal, and allergic diseases are also seen. The Mucorales are associated with angioinvasive disease, often leading to thrombosis, infarction of involved tissues, and tissue destruction mediated by a number of fungal proteases, lipases, and mycotoxins. If the diagnosis is not made early, dissemination often occurs. Therapy, if it is to be effective, must be started early and requires combinations of antifungal drugs, surgical intervention, and reversal of the underlying risk factors. The Entomophthorales are closely related to the Mucorales on the basis of sexual growth by production of zygospores and by the production of coenocytic hyphae. Despite these similarities, the Entomophthorales and Mucorales have dramatically different gross morphologies, asexual reproductive characteristics, and disease manifestations. In comparison to the floccose aerial mycelium of the Mucorales, the Entomophthorales produce a compact, glabrous mycelium. The asexually produced spores of the Entomophthorales may be passively released or actively expelled into the environment. Human disease with these organisms occurs predominantly in tropical regions, with transmission occurring by implantation of spores via minor trauma such as insect bites or by inhalation of spores into the sinuses. Conidiobolus typically infects mucocutaneous sites to produce sinusitis disease, while Basidiobolus infections occur as subcutaneous mycosis of the trunk and extremities. The Entomophthorales are true pathogens, infecting primarily immunocompetent hosts. They generally do not invade blood vessels and rarely disseminate. Occasional cases of disseminated and angioinvasive disease have recently been described, primarily in immunocompromised patients, suggesting a possible emerging role for this organism as an opportunist.

Correlation between β-carotene content, several physical factors and the formation of zygospores in Mucor spp.

Mating experiments were performed to study the correlation between carotene content in the mycelium of strains of Mucor and zygospore production. The dominance of (-) strains in the M. circinelloides group and (+) strains in the M. hiemalis group was observed. Zygospore production was possible under both light and dark conditions, irrespective of temperature and media. Interspecific crosses between M. odoratus and M. hiemalis revealed the close relation between the two species.

Zygospore formation in Mortierella capitata

A novel type of zygospore formation is described in the heterothallic speciesMortierella capitata, which was repeatedly isolated from soils inhabited by pillbugs (Armadillidium vulgare, Isopoda). Zygospore formation was induced on media containing sterilized arthropods. Anisogamy and colorless zygospore walls are shared with other zygosporic species ofMortierella, but a unique feature ofM. capitata is the production of zygospores on elongated macrosuspensors which are covered by branches of the microsuspensors. This kind of zygosporogenesis is termed “capitata-type” here. The taxonomic position ofM. capitata is discussed based on the zygospore characteristics.

Factors Affecting Zygosporogenesis in Mucor piriformis and Gilbertella persicaria

The effects of four factors, namely temperature, light, pH, and type of medium on zygosporogenesis of Mucor piriformis and Gilbertella persicaria were studied. In addition, the effects of ratios of (+):(-) mating types on zygosporogenesis of M. piriformis were evaluated. For M. piriformis, rich media, temperature lower than 15 C, medium pH of 3.5 to 8, and darkness favored zygospore development. For G. persicaria, rich media, temperature of 20 C, darkness, and medium pH of 4 to 6 favored zygospore development. Zygospores of M. piriformis were not produced when cultures containing pairs of (+) and (-) mating types were continuously incubated at 20 and 23 C for 30 d. However, as many as 6000 zygospores developed when cultures were incubated continuously at 0, 5, 10, or 15 C for 30 d. Optimum temperature for zygospore production was 10 C for M. piriformis and 20 C for G. persicaria. Significantly fewer zygospores of M. piriformis were produced after incubation of cultures continuously at 15 C than at 0, 5, or 10 C with or without 2-d of preincubation at 20 C. Zygosporogenesis was favored by low temperatures and inhibited by continuous light in M. piriformis. In contrast, zygosporogenesis of G. persicaria was inhibited by low temperatures and significantly reduced by continuous light. Although rich nutrient favored the production of more zygospores than less rich media in both species studied, zygosporogenesis of G. persicaria was less dependent on high nutrients than that of M. piriformis. The numbers of zygospores produced by M. piriformis depended on both total levels of propagules and ratios of (+):(-) mating types.

Factors affecting zygosporogenesis in Mucor piriformis and Gilbertella persicaria

The effects of four factors, namely temperature, light, pH, and type of medium on zygosporogenesis of Mucor piriformis and Gilbertella persicaria were studied. In addition, the effects of ratios of (+):(-) mating types on zygosporogenesis of M. piriformis were evaluated. For M. piriformis, rich media, temperature lower than 15 C, medium pH of 3.5 to 8, and darkness favored zygospore development. For G. persicaria, rich media, temperature of 20 C, darkness, and medium pH of 4 to 6 favored zygospore development. Zygospores of M. piriformis were not produced when cultures containing pairs of (+) and (-) mating types were continuously incubated at 20 and 23 C for 30 d. However, as many as 6000 zygospores developed when cultures were incubated continuously at 0, 5, 10, or 15 C for 30 d. Optimum temperature for zygospore production was 10 C for M. piriformis and 20 C for G. persicaria. Significantly fewer zygospores of M. piriformis were produced after incubation of cultures continuously at 15 C than at 0, 5, or 10 C with or without 2-d of preincubation at 20 C. Zygosporogenesis was favored by low temperatures and inhibited by continuous light in M. piriformis. In contrast, zygosporogenesis of G. persicaria was inhibited by low temperatures and significantly reduced by continuous light. Although rich nutrient favored the production of more zygospores than less rich media in both species studied, zygosporogenesis of G. persicaria was less dependent on high nutrients than that of M. piriformis. The numbers of zygospores produced by M. piriformis depended on both total levels of propagules and ratios of (+):(-) mating types.

ENVIRONMENTAL FACTORS AND SEXUAL EXPRESSION INCHLOROCOCCUM ECHINOZYGOTUM(CHLOROPHYCEAE)1

ABSTRACTSeveral environmental factors affected total growth and zygospore production inChlorococcum echinozygotumStarr. The temperature range at which zygospore production occurred was more restricted than the range that supported vegetative growth. Light intensity had little effect upon zygospore formation: gamete production and gamete pairing occurred in darkness. Zygospore production occurred over a wide pH range; bicarbonate had a minor effect upon zygospore formation. Nitrogen concentration was the factor of primary importance. As the level of nitrogen supplied as nitrate, ammonia, urea and asparagine in the medium was increased, zygospore production first increased (over no nitrogen) at low levels and then decreased at high levels. All levels of glutamine supplied reduced zygospore production. A possible way in which nitrogen concentration in the medium and sexual expression are linked is discussed.

Effect of salinity on the reproduction of terrestrial and marine fungi

The effect of salinity on the sporulation of twenty selected fungi, which included terrestrial (10), fresh-water (2) and marine (8) species, was investigated using a variety of techniques, e.g. growth on agar plates, shake culture, a range of substrates and perfusion chambers. Sporangiospores of terrestrial mucoraceous fungi were produced over the whole range of salinities tested but zygospore production was inhibited at higher salinities. Terrestrial ascomycetes showed limited tolerance to high salinity and this may be affected by the available growth factors present. Marine ascomycetes have a wide tolerance to low-salinity conditions and may be less conditioned by the available substrate. The sporulation of the majority of the fungi imperfecti, irrespective of their ecological origin, exhibited a broad tolerance to highland low-salinity conditions. Exceptions were the appendaged marine hyphomycetes which are intolerant of extreme low-salinity conditions, and the appendaged fresh-water hyphomycetes which were inhibited by high-salinity conditions. In Chaetomium globosum Kunze ex Fr. the effect of salinity on perithecial development depends on when the sea-water concentration is added to the perfusion medium. The significance of these observations in relation to the ecological distribution of aquatic fungi is discussed, and what is meant by the term ‘marine fungi’ briefly considered.

Induction of zygospore production in Mucor saximontensis, an agamic strain of Zygorhynchus moelleri

Induction of zygospore production in Mucor saximontensis, an agamic strain of Zygorhynchus moelleri

Trichomycetes inhabiting the digestive tract of Simulium equinum larvae

Both the mid and hind guts of Simulium equinum L. larvae, collected from a stream in Dorset, are shown to contain several species of Trichomycetes. Thalli attached to the peritrophic membrane lining the mid gut belong to Harpella melusinae Leger & Duboscq, whilst those attached to the hind gut are Paramoebidiutn chattonii Duboscq, Leger & Tuzet, unidentified species of Smittium , and two morphologically distinct species of Stipella . Thalli of H. melusinae occur in their vegetative and asexual reproductive forms, zygospore production not having been observed. Smittium thalli are epiphytic upon P. chattonii , are characterized by a unique form of branching, the distal regions of which often bear appendaged conidia, and on one thallus a conjugation between adjacent hyphae resulted in the formation of an anvil-shaped zygospore. The two morphologically distinct species of Stipella differ mainly in the foim of the holdfast and in the shape and arrangement of the conidial appendages. They both occur in vegetative, asexual and sexual reproductive conditions, with the conidia-bearing thalli restricted to the posterior region of the hind gut and zygospore-bearing thalli to the anterior region.

Reproduction and growth of the mixotrophic flagellate furcilla stigmatophora (Skuja) Korshikov (volvocales)

1. The morphology, asexual and sexual reproduction, and zygospore germination of the green flagellate Furcilla stigmatophora is described from naturally occurring and cultured material. 2. Combinations of nine clones were cultured and examined for evidence of mating and zygospore production. There appear to be two mating types. 3. The effects of dry heat and other factors on zygospore germination were tested. 4. Negative phototaxis, positive chemotaxis and positive reaction to higher oxygen concentration were established, while geotaxis was not observed. 5. Growth under various anaerobic and aerobic, light and dark conditions was compared. 6. No evidence of holozoic nutrition was found.

A volatile substance controlling early stages of zygospore formation in Rhizopus sexualis.

SUMMARY: The inhibitory effect of low temperature (c. 10°) on initiation and early development of zygospores of Rhizopus sexualis is less severe in mature cultures (in which numerous zygospores have already been formed before transfer to the low temperature) than in young ones. The severe effect of low temperature on immature cultures is not counteracted by any of a number of known growth substances, by extracts of mature mycelium and zygospores, or by used culture media. The effect of mature cultures in counteracting low temperature inhibition of zygospore production in young ones is able to pass across a gap of 5 mm. between the cultures and must therefore be due to a volatile substance (or substances) produced by the mature mycelium. By the use of small chambers which allow young test cultures to be kept at 10° while a stream of air from mature ones growing at 20° passes over them, it is confirmed that the active factor is volatile. This substance is not carbon dioxide or ammonia and is basic in nature. Its probable identity is discussed and comparison is made with some other volatile substances reported to influence growth and development of fungi.

A Possible Relationship between Nucleic Acid Metabolism and the Initiation of Zygospores of Rhizopus sexualis

IT has been observed1 in the homothallic fungus Rhizopus sexualis (Smith) Callen that the initiation and early stages of maturation of zygospores, which at 20–25° C. occur within a few days of inoculation, are completely inhibited at temperatures below 10° C. Later stages in the maturation of zygospores initiated at room temperature and afterwards transferred to low temperature are not inhibited; this suggests that a possible cause of the inhibition is a block in the synthesis of some compound or compounds essential for the early stages of zygospore production.

The inhibitory effect of low temperature on early stages of zygospore production in Rhizopus sexualis.

SUMMARY: Colonies of Rhizopus sexualis (Smith) Callen on 1% (w/v) malt agar at 20. show the first stages in conjugation approximately 40 hr. after inoculation and the first mature zygospores after a further 32–34 hr. Transfer to 5–10. prevents the initiation of conjugation and inhibits the further development of the majority of pairings in which the gametangia are not fully delimited at the time of transfer. Fully delimited gametangia continue to develop and to produce mature zygospores at the low temperature. This effect is almost entirely independent of the composition and pH value of the medium. Sporangia are produced in greater numbers at the low temperature than at 20. The effect of low temperature on formation of zygospores of Mucor hiemalis, Zygorrhynchus macrocarpus and Z. moelleri is essentially similar to that with R. sexualis, but Phycomyces blakesleeanus shows only slight inhibition at 5. and none at 7. or over. The significance of the inhibitory effect is discussed.

Factors Affecting the Production of Zygospores by Choanephora cucurbitarum

SUMMARYThe mycelia of the (+) and (-) sexes of C. cucurbitarum isolated from the same source were found to differ slightly in appearance on certain media.In the presence of mixed (+) and (-) mycelia zygospores develop abundantly within a few days on a wide variety of agar and liquid media. The range of favorable temperature was approximately 15–37° C. Light was not required and had no apparent effect, except at 15° C, where it was inhibitory. Zygospores formed in an atmosphere containing as much as ten percent carbon dioxide.Zygospore production coincided with the exhaustion of the available carbon supply in the medium and was induced by subjecting well nourished mycelium to starvation conditions. Some sugars which were poor for mycelial growth favored quick zygospore production. All nitrogen sources tested favored their formation, provided the medium did not become too acid. The favorable pH range was approximately 4.5 to 8.5.A simple culture tube designed for the slow continuous flow of liquid medium over growing mycelium is described. This method was used to maintain constant pH of the medium.In mixed cultures of (+) and (-) mycelia, particularly in liquid media, there is produced a greatly increased amount of beta-carotene, apparently stimulated by hormone-like substances secreted by the mycelium of the opposite sex. The beta-carotene becomes concentrated in the suspensors and is suspected of having some function in sexual reproduction of this fungus.Mature typical zygospores were found in moist, well-decayed pumpkin flowers collected from a garden where both sexes had been found previously.

Factors Affecting the Production of Zygospores by Choanephora Cucurbitarum

The mycelia of the (+) and (-) sexes of C. cucurbitarum isolated from the same source were found to differ slightly in appearance on certain media.In the presence of mixed (+) and (-) mycelia zygos...