The gut fungus Basidiobolus ranarum has a large genome and different copy numbers of putatively functionally redundant elongation factor genes

Fungal genomes range in size from 2.3 Mb for the microsporidian Encephalitozoon intestinalis up to 8000 Mb for Entomophaga aulicae, with a mean genome size of 37 Mb. Basidiobolus, a common inhabitant of vertebrate guts, is distantly related to all other fungi, and is unique in possessing both EF-1α and EFL genes. Using DNA sequencing and a quantitative PCR approach, we estimated a haploid genome size for Basidiobolus at 350 Mb. However, based on allelic variation, the nuclear genome is at least diploid, leading us to believe that the final genome size is at least 700 Mb. We also found that EFL was in three times the copy number of its putatively functionally overlapping paralog EF-1α. This suggests that gene or genome duplication may be an important feature of B. ranarum evolution, and also suggests that B. ranarum may have mechanisms in place that favor the preservation of functionally overlapping genes.     

Mortality of captive Canadian toads from Basidiobolus ranarum mycotic dermatitis

Twenty-six adult free-ranging Canadian toads (Bufo hemiophrys) were collected from northeastern North Dakota (USA) during the last week of August 1994 and placed in captivity. During late December and January 1995, 21 Canadian toads died. Clinical signs included increased time sitting in water bowls, darkened dorsal skin, constant arching of their backs, and hyperemia and sloughing of ventral epidermis. The condition progressively worsened until death occurred within 5 to 7 days after onset of clinical disease. Mycotic dermatitis due to Basidiobolus ranarum was diagnosed in all toads and the fungus was isolated from 11 (52%) of 21 toads. Histology of the ventral skin and digits revealed numerous fungal spherules and occasional hyphae without significant inflammatory reaction. This condition clinically resembled red leg associated with Aeromonas hydrophila and many other bacterial organisms, and the diseases could be confused without appropriate diagnostic tests. This also is the first report of B. ranarum causing clinical disease in a toad species.     

Ultrastructure of Mitochondria and Crystal-containing Bodies in Mature Ballistospores of the Fungus Basidiobolus ranarum as Revealed by Freeze-etching

By using the freeze-etch technique, a regular pattern on both sides of the outer mitochondrial membrane can be demonstrated in mature spores of Basidiobolus ranarum. Bands consisting of 5 to 10 parallel ridges, each of which is 20 nm wide, envelop the outer as well as the inner side of this membrane. Hexagonal crystals, probably representing stored protein, are enclosed in special bodies with a very smooth surrounding unit membrane. The crystals are formed by parallel rods which consist of globular subunits, 6.5 to 7.0 nm wide.     

Pathogenicity of Conidiobolus spp. and Basidiobolus ranarum to arthropods co-occurring in leaf litter

A novel method is described for the extraction and presentation of mixed arthropods from litter as targets for potentially pathogenic species of Conidiobolus and Basidiobolus (Zygomycetes: Entomophthorales). All arthropods and test fungi (except C. nr. pumilus from broad leaf litter) were from the same larch (Larix) plantation. For 8 fungus species a bioassay (and repeat), were followed by survivorship comparison tests; Breslow, Logrank (Mantel-Heinszel/Peto) and Wilcoxon (Gehan/Lee-Desau). These were applied to test and control data separately for collembola and mites. Kaplan-Meier plots of Hazard Function were made. Of possible pathogenic effects the most marked was the high mortality of collembola and mites when showered with conidia of C. coronatus. Conidiobolus thromboides (collembola and mites) and C. osmodes (mites only) were associated with enhanced death in one of their two bioassays. Of the other 5 test species, C. adiaeretus and C. iuxtagenitus gave no indication of pathogenicity; nor did C. lamprauges, C. heterosporus and C. pumilus. Ecological implications are briefly discussed.     

Fusarium udum as a mycoparasite ofMortierella subtilissima

Summary Fusarium udum was found to be a mycoparasite ofMortierella subtilissima which is a new record. Formation of chlamydospores byF. udum insideM. subtilissima was observed as a result of mycoparasitism.     

Phoma glomerata as a mycoparasite of powdery mildew

Ampelomyces and Phoma species are frequently confused with each other. Isolates previously attributed to the genus Ampelomyces were shown to be Phoma isolates through studies of their morphology and life cycle and ribosomal DNA internal transcribed spacer region 1 sequence analysis. Phoma glomerata can colonize and suppress development of powdery mildew on oak and may have utility as a mycoparasitic agent.     

Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes) as a potential mycoparasite on Sphaerotheca fuliginea (Ascomycotina: Erysiphales)

Hyphomycete Paecilomyces fumosoroseus that is well known as saprophytic and entomopatogenic fungus was investigated for its mycoparasitism on the cucumber powdery mildew pathogen. Mycoparasitism was documented by using standard bioassay and SEM. Effects of mycoparasitism were evaluated in three types of experiments. Paecilomyces fumosoroseus was applied in the form of graded suspensions into a colony of powdery mildew on a leaf segment. Interaction between both fungi was observed as the percentage of colonized area vs. experimental time. In the second experiment, young cucumber plants were sprayed with a suspension of Paecilomyces fumosoroseus 24 h before inoculation of Sphaerotheca fuliginea. Pre-treatment with P. fumosoroseus reduced development and spreading of powdery mildew infection significantly 15 days post-inoculation in contrast to pre-treatments with sulfur fungicide and distilled water. The development of pure culture powdery mildew under determined experimental conditions was observed and compared with treated variants. In the third experiment, mildewed plants were treated with a suspension of P. fumosoroseus. The control treatments with sulfur fungicide and distilled water were tested. Effects of P. fumosoroseus on the dispersion of powdery mildew during a 21-day period were observed.P. fumosoroseus suppressed the development and spread of cucumber powdery mildew significantly during the time of the experiment. The mechanical and physical damages and disruptions of vegetative and fruiting structures of powdery mildew were recorded under light microscopy and S.E.M.Results were concluded in pursuance to differences between the natural behaviour and development of S. fuliginea on cucumber plants treated with P. fumosoroseus and non-treated plants.     

Ultrastructure of the sporangiospore of Piptocephalis unispora (Mucorales)

Sporangiospore structure in Piptocephalis unispora Benjamin was studied using light microscopy, freeze-etching, scanning and transmission electron microscopy, and compared with that of other members of the Mucorales. A merosporangial wall, plasmalemmal invaginations, and wall protuberances were demonstrated in sections and their possible significance discussed.     

Ultrastructure of the Sporangiospore of Kickxella alabastrina (Mucorales)

The structure of the sporangiospore of Kickxella alabastrinawas examined by means of carbon replicas, ultrathin sectionsand chemical and physical disintegration. The wall consistsof an outer ornamented, largely amorphous complex and an inner,largely fibrillar complex. The outer complex is disrupted bytreatment in hot dilute alkali whereas the inner complex islargely unaffected. An annulus, similar to that described forCoemansia aciculifera, forms part of the central region of theinner complex and apparently develops prior to liberation ofthe spore from the pseudophialide. A labyrinthiform organelle,attached to the base of the septum which separates the sporefrom the pseudophialide, is described.     

Ultrastructure of the Sporangiospore of Coemansia aciculifera (Mucorales)

Examination of the sporangiospore of Coemansia aciculifera bymeans of carbon replicas, ultrathin sections, and fragmentsobtained by using physical and chemical disintegration techniquesshows the wall to consist of an outer spiny, largely amorphous,complex and an inner, largely fibrillar, complex. The outercomplex is disrupted by treatment in hot dilute alkali whereasthe inner complex is largely unaffected. Helically orientatedfibrils of the inner complex are arranged in layers. An annulusforms part of the central region of the inner complex which,it is suggested, might be especially involved in the processof germination.     

Statistical optimization of medium components for production of extracellular chitinase by Basidiobolus ranarum: a novel biocontrol agent against plant pathogenic fungi

The influence of concentration of medium components such as colloidal chitin, lactose, malt extract, yeast extract, and peptone on the chitinase production from Basidiobolous ranarum at the flask level were studied by using statistical tool Central Composite Design (CCD) and analysed by Response Surface Methodology (RSM). The results revealed that colloidal chitin, malt extract and peptone had significant effect (P < 0.01) on the chitinase production at their individual levels. The polynomial equation of the model developed incorporates 3 linear, 3 quadratic and 5 interactive terms. Maximum chitinase production of 3.47 U ml(-1) was achieved with 1.5% colloidal chitin, 0.125% lactose, 0.025% malt extract and 0.075% peptone. After optimization, chitinase activity was increased by 7.71 fold. A second order polynomial equation was found to be useful for the development of efficient bioprocess for chitinase production. To screen the biotechnological potential of this enzyme, degradation of fungal mycelia by ammonium sulphate precipitate of the same was studied for several pathogenic fungi-in vitro which showed promising results particularly against Rhizoctonia solani and Fusarium solani. This study provides the first evidence showing the effectiveness of RSM for the development of a robust statistical model for the chitinase production by Basidiobolus and for its application in the biocontrol of phytopathogenic fungi. (? 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).