Mucor Hiemalis Research Articles

Effect of Tribolium castaneum in Qualitative and Quantitative Contamination with Fungi

The objective of this study was to estimate the quantitative contamination fungi in sound whole flour that infested with red flour beetle Tribolium castaneum under the effect of different numerical levels of insect, which are (5, 10, 20) pairs in the level of contamination. The study was accomplished under a temperature 30±2 0C and humidity 70 ±5%. The result showed the following. 13 species of fungus which belong to five genera were isolated from sound and infested whole flour samples with three numerical levels of the insect. These were (5, 10, 20) pairs and for two generations. The species isolated were: Aspergillus flavesus, A niger, A. terreus, Mucor hiemalis, Alternaria Alternaria, Paecilomyces Sp. Penicillium sp1, Penicillium sp2. Whereas at the two numerical levels (10, 20) pairs of insects, the fungus species Sterils mycelia, A.ustus, Emericella sp, Sepedonium sp. were isolated. The more frequently fungus in the samples of infested flour in the level 20 pairs of insects was A. flavus. Its frequency was (47.37%), also in level 5 pairs of the fungus A niger, which frequency ratio was (42, 58%). In the sound flour samples the more frequency. A. fumigates in level 5 pairs of insects which its frequency was (34, 48%) and in level 20 pairs of insects was the fungus A. niger which its frequency was (66.6%).The results showed that the rate of numerical of fungi increased with increasing levels of numbers of the insects ,the highest rate of fungus numerical was recorded in infested whole flours at the numerical level 10 pairs of insects was (31.41X10)2 colony/ gm. While their average numbers were (15.83×102) colony /gm at level 5 pairs of insects. It was observed that the average number of fungus in flour insects was higher than their numbers in sound flour.

Microbial Transformation of Licochalcones.

Microbial transformation of licochalcones B (1), C (2), D (3), and H (4) using the filamentous fungi Aspergillus niger and Mucor hiemalis was investigated. Fungal transformation of the licochalcones followed by chromatographic separations led to the isolation of ten new compounds 5–14, including one hydrogenated, three dihydroxylated, three expoxidized, and three glucosylated metabolites. Their structures were elucidated by combined analyses of UV, IR, MS, NMR, and CD spectroscopic data. Absolute configurations of the 2″,3″-diols in the three dihydroxylated metabolites were determined by ECD experiments according to the Snatzke’s method. The trans-cis isomerization was observed for the metabolites 7, 11, 13, and 14 as evidenced by the analysis of their 1H-NMR spectra and HPLC chromatograms. This could be useful in better understanding of the trans-cis isomerization mechanism of retrochalcones. The fungal transformation described herein also provides an effective method to expand the structural diversity of retrochalcones for further biological studies.

Isolation, identification and pathogenicity patterns of Mucor hiemalis in cultured Cyprinis carpio communis using challenged system

Oomycetes and filamentous fungi are predominantly causing disease outbreaks in cultured fisheries worldwide. Mucormycosis are infrequently occurring in an immunocompromised or immunosuppressed fish host, predisposed mostly by undesirable changes in aquatic habitats. Few reports have shown mucor mostly occurring in water and soil, thus caused infection in freshwater and marine fish. In this study, we report Mucor hiemalis infection from cultured fish farms infecting gills and skin of carp fish (Cyprinus carpio communis) and rainbow trout (Oncorhynchus mykiss). The etiological pathogen was identified by morphological features of pathogen and molecular approaches using large subunit of ribosomal RNA as the fungal barcode. Pathogenicity was characterized by experimental exposure of carp fish to M. hiemalis, followed by histopathological approach. The histopathological results revealed that the pathogen managed to establish initial infection on and inside the gills, cutaneous and subcutaneous surfaces. The infection post initial establishment through systemic blood circulation managed to suppress the defense system and predisposed host to heighten infection and systemic mycosis. Further, the M. hiemalis was also able to cause severe infectivity post two weeks of exposure which resulted in mortality of fish host. The study provides the first insight into the pathogenicity patterns of M. hiemalis on the fish host and its disease-causing potential.

EFFECTS OF STORAGE METHODS AND MYCOFLORA ON PROXIMATE COMPOSITION OF AFRICAN YAM BEAN (Sphenostylis stenocarpa Hochust ex Rich ) SEEDS

One of the limitations of African yam bean (AYB) (Sphenostylis sternocarpa) is poor storage ability due to the adverse effect of seed-borne fungi. This study was conducted to examine the effects of storage methods on nutritive composition of AYB seeds stored in three types of storage materials viz; jute bags, polypropylene bags and plastic bowls. Freshly harvested AYB seeds were stored in all the storage materials for 6 months using 2 × 3 factorial (2 AYB cultivars and 3 storage methods) in 3 replicates. The proximate analysis of the stored AYB seeds was carried out at 3 and 6 months after storage using standard methods. The temperature and relative humidity of the store room were recorded monthly. Seeds stored in jute bags gave the best values for crude protein (24.87%), ash (5.69%) and fat content (6.64%) but recorded least values for crude fibre (2.55%), carbohydrate (50.86%) and moisture content (12.68%) at the 6th month of storage. Temperature of the store room decreased from 32.9 ºC - 28.3ºC, while the relative humidity increased from 78% - 86%. Decreased incidence of field fungi namely: Rhizopus oryzae, Aspergillus flavus, Geotricum candidum, Aspergillus fumigatus and Mucor meihei was accompanied by increase in storage fungi viz: Apergillus niger, Mucor hiemalis, Penicillium espansum and Penicillium atrovenetum with prolonged storage. The study showed that out of the three storage materials, jute bag was more effective in preserving AYB seeds.

Cytotoxic, anti-biofilm and antimicrobial polyketides from the plant associated fungus Chaetosphaeronema achilleae

From extracts of the plant associated fungus Chaetosphaeronema achilleae collected in Iran, a previously unreported isoindolinone named chaetosisoindolinone (1) and a previously undescribed indanone named chaetosindanone (2) were isolated in addition to five known metabolites, 2-(2-acetyl-3,5-dihydroxyphenyl) acetic acid (3), vulculic acid (4), 2-(2-acetyl-3-hydroxy-5-methoxyphenyl)acetic acid (5), curvulin (6), and curvulol (7). Their structures were elucidated on the basis of extensive spectroscopic analysis and high-resolution mass spectrometry. The isolated compounds were tested for their antimicrobial, anti-biofilm, and nematicidal activities. Compound 2 exhibited cytotoxicity against the human breast adenocarcinoma MCF-7 cells with an IC50 value of 1.5 μg/mL. Furthermore, compounds 4 and 7 almost completely inhibited biofilm formation in Staphylococcus aureus at 256 μg/mL. Weak antimicrobial activities were also observed for some of the isolated compounds against Mucor hiemalis, Rhodoturula glutinis, Chromobacterium violaceum, and Staphylococcus aureus.

Sparticolins A-G, Biologically Active Oxidized Spirodioxynaphthalene Derivatives from the Ascomycete Sparticola junci.

To explore the chemical diversity of metabolites from new species of Dothideomycetes, the ex-type strain of Sparticola junci was investigated. Seven highly oxygenated and functionalized spirodioxynaphthalene natural products incorporating carboxyalkylidene-cyclopentanoid (1-4), carboxyl-functionalized oxabicyclo[3.3.0]octane (5-6), and annelated 2-cyclopentenone/δ-lactone (7) units, sparticolins A-G, were isolated from submerged cultures of the fungus. Their chemical structures including their relative (and absolute) configurations were established through spectroscopic and X-ray crystallographic analyses. Sparticolin B (2) exhibited inhibitory activity against the Gram-positive bacteria Bacillus subtilis, Micrococcus luteus, and Staphylococcus aureus, while sparticolin G (7) showed antifungal activities against Schizosaccharomyces pombe and Mucor hiemalis. All other sparticolins were only weakly active against S. aureus and also showed weak activities against the nematode Caenorhabditis elegans. Compounds 2 and 7 also showed moderate cytotoxic activities against seven mammalian cell lines.

Multimetal bioremediation and biomining by a combination of new aquatic strains of Mucor hiemalis

Here we describe a unique microbial biotechnology for simultaneous bioremediation and biomining of twelve ionic metals overcoming the obstacles of multimetal toxicity to microbes. After a thorough search of key microorganisms in microbiomes of many sulfidic springs in Bavaria (Germany) over an area of 200 km2, we found three new strains EH8, EH10 and EH11 of Mucor hiemalis physiologically compatible and capable of multimetal-remediation and enrichment. We combined the multimetal-resistance, hyper-accumulation and elicitation power of EH8, EH10 and EH11 to develop a novel biotechnology for simultaneous removal, fractionation and enrichment of metal ions. As a first step we showed the intracellular fixing and deposition of mercury as nanospheres in EH8’s sporangiospores. Scanning Electron Microscopy-Energy-Dispersive X-Ray analysis revealed binding and precipitation of other applied metal ions as spherical nano-particles (~50–100 nm) at the outer electro-negative cellwall-surface of EH8, EH10 and EH11 sporangiospores. Microbiomes, germinated spores and dead insoluble cellwalls of these strains removed >81–99% of applied Al, Cd, Co, Cr, Cu, Hg, Ni, Pb, U, and Zn simultaneously and furthermore enriched precious Ag, Au and Ti from water all within 48 h, demonstrating the potential of new biotechnologies for safe-guarding our environment from metal pollution and concentrating precious diluted, ionic metals.

Oxyfunctionalization of nonsteroidal anti-inflammatory drugs by filamentous-fungi.

We aimed to expand the microbial biocatalyst platform to generate essential oxyfunctionalized standards for pharmaceutical, toxicological and environmental research. In particular, we examined the production of oxyfunctionalized nonsteroidal anti-inflammatory drugs (NSAIDs) by filamentous-fungi. Four NSAIDs; diclofenac, ibuprofen, naproxen and mefenamic acid were used as substrates for oxyfunctionalization in a biocatalytic process involving three filamentous-fungi strains; Beauveriabassiana, Clitocybenebularis and Mucorhiemalis. Oxyfunctionalized metabolites that are major degradation intermediates formed by Cytochrome P450 monooxygenases in human metabolism were produced in isolated yields of up to 99% using 1gl-1 of substrate. In addition, a novel compound, 3',4'-dihydroxydiclofenac, was produced by B.bassiana. Proteomic analysis identified CYP548A5 that might be responsible for diclofenac oxyfunctionalization in B.bassiana. Efficient fungi catalysed oxyfunctionalization was achieved when using NSAIDs as substrates. High purities and isolated yields of the produced metabolites were achieved. The lack of current efficient synthetic strategies for oxyfunctionalization of NSAIDs is a bottleneck to perform pharmacokinetic, pharmacodynamic and toxicological analysis for the pharmaceutical industry. Additionally, oxyfunctionalized derivatives are needed for tracking the fate and impact of such metabolites in the environment. Herein, we described a fungi catalysed process that surpasses previously reported strategies in terms of efficiency, to synthesize oxyfunctionalized NSAIDs.

Application of Novel Adsorbent Prepared by Mucor hiemalis Biomass Impregnated with Calcium Alginate for Removal of Sr2+ from Aqueous Solutions

In this research, a novel biosorbent was prepared by Mucor hiemalis biomass combined with calcium alginate (Mucor hiemalis/Alg-Ca). The dead biomass was entrapped into alginate gel by curing method in the presence of Ca2+ ions. The synthesized biosorbent characterized by XRD, EDAX, BET, FTIR, and SEM techniques was used for removal of Sr2+ from aquatic streams under various experimental conditions and the optimized adsorption capacity of 140 mg g−1 was obtained. The selectivity of the adsorbent towards Sr2+ studied in the presence of Na+, Cs+, Ca2+ and Mg2+ was reasonably high. The adsorption process was kinetically fast and the equilibrium was established within 60 min, and followed the pseudo-second order kinetics model. The equilibrium data was well described by Langmuir isotherm model. The thermodynamics parameters (∆G°, ∆H° and ∆S°) of the process were determined. Positive ∆H° and negative ∆G° were indicative of the endothermic and spontaneous nature of the adsorption process.

Synthesis and in-vitro biological evaluation of 1,1-diaryl-2-(1,2,3)triazol-1-yl-ethanol derivatives as antifungal compounds flutriafol analogues

A small library of diverse 1,1-diaryl-2-(1,2,3)triazol-1-yl-ethanol derivatives was designed and prepared from CuAAC reaction as the key step. The molecular structure of some representative compounds was unambiguously determined from X-ray diffraction studies. In addition, synthesized 1,2,3-triazoles were evaluated for activity against filamentous fungi (Mucor hiemalis, Aspergillus fumigatus, Trichosporon cutaneum, and Rhizopus oryzae) and yeasts that belong to the genus Candida. Two compounds showed high activity against C. utilis (MIC 0.5 $$\upmu \mathrm{{g/mL}}$$ ) and A. fumigatus (MIC 4 $$\upmu \mathrm{{g/mL}}$$ ) which is close to itraconazole used as reference compound. 1,1-diaryl-2-(1,2,3)triazol-1-yl-ethanol analogues to flutriafol were prepared from CuAAC reaction and the molecular structure of some representative compounds was unambiguously determined from X-ray diffraction studies. Some of these 1,2,3-triazoles displayed activity against filamentous fungi and Candida yeasts, especially C. utilis and A. fumigatus.

Soil microbial phosphorus turnover and identity of algae and fungi in biological soil crusts along a transect in a glacier foreland

Although biological soil crusts (BSCs) are known for a variety of ecological functions, the role of individual biocrust organism species in BSCs on their P cycling is almost unknown. To evaluate the hypothesis that the contribution of defined cultivable taxa of fungi and algea might influence the microbial P storage and mobilization in the underlying soil, a transect was investigated in a glacier foreland in the mountain plateau Hardangervidda in Southern Norway. Microbial biomass P storage in soil under BSC increased continuously with increasing distance to the glacier and increasing fungal species richness. Lowest soil phosphatase activity and soil organic matter content were linked with highest number of algal and fungal in the overlaying BSCs. Enhanced soil microbial biomass P was linked with an increasing water content and decreasing pHCaCl2 of the soil. Nine to 21 algal and 5 to 10 fungal taxa were identified per test site from BSCs along the transect. Members of the Eustigmatophyceae and Xanthophyceae were observed exclusively close to the glacier, those of Klebsormidiophyceae exclusively in larger distance. The most common fungal genera in the BSCs were Lecythophora, Penicillium, Rhizoscyphus and Pholiota, whereas Cosmospora sp., Thelebolus globosus and Mucor hiemalis were found exclusively close to the glacier. The presence of usually biomass-rich taxa in the soil crusts was related to an increased microbial P storage in total. An increasing impact of microbial P storage under BSCs on the subsequent successional vegetation development is suggested.

Isolation and characterization of microorganisms associated with soft cheese produced from sheep milk using different coagulants

Milk is an ideal medium for the growth of microorganisms because it is highly nutritious. Cow milk is the major milk used for the production of cheese although milk can also be gotten from other animals such as sheep, goat, camels and buffalo. Soft cheese was produced from sheep milk and the microorganisms associated with the soft cheese were isolated and identified using colonial, morphological and biochemical characterization. Different coagulants such as Calotropis procera, Carica papaya, lemon juice and steep water from maize, millet and sorghum were used for the production. The result revealed that six different bacteria were isolated and identified and they include Bacillus cereus, Bacillus subtilis, Lactococcus lactis, Lactobacillus casei, Pseudomonas aeruginosa, Staphylococcus aureus and 8 different fungi species isolated and identified include Aspergillus niger, Aspergillus fumigatus, Rhizopus stolonifer, Penicillium chrysogenium. Mucor hiemalis, Candida albicans, Fusarium verticillioides and Saccharomyces sp. The presence of these microorganisms indicated that the soft cheese produced was not sterile and highly contaminated and it can pose serious health risk to consumers. It is therefore recommended that soft cheese should be produced under hygienic condition since it’s a ready to eat food.

Biotransformation of a major beer prenylflavonoid - isoxanthohumol.

Microbial transformations of isoxanthohumol (1), a beer prenylated flavonoid, by 51 fungi were investigated. Many of the tested fungi cultures were capable of effective transformation of 1. Mucor hiemalis and Fusarium oxysporum converted isoxanthohumol (1) into isoxanthohumol 7-O-β-d-glucopyranoside (3) and (2R)-2″-(2″'-hydroxyisopropyl)-dihydrofurano[2″,3″:7,8]-4″,5-hydroxy-5-methoxyflavanone (4), respectively. No product was obtained in the transformation of 1 by Absidia glauca conducted in a phosphate buffer. In the same medium, Beauveria bassiana converted isoxanthohumol (1) to isoxanthohumol 7-O-β-d-4″'-O-methylglucopyranoside (2).

Antifungal Prenylated Diphenyl Ethers from Arthrinium arundinis, an Endophytic Fungus Isolated from the Leaves of Tobacco (Nicotiana tabacum L.).

An endophytic fungus Arthrinium arundinis TE-3 was isolated and purified from the fresh leaves of cultivated tobacco (Nicotiana tabacum L.). Chemical investigation on this fungal strain afforded three new prenylated diphenyl ethers (1–3) as well as three known analogues (4–6). Structure elucidation of the isolated compounds was carried out by analysis of 1D and 2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS) spectra, as well as by comparison of those data with literature data. The absolute configuration of the stereogenic center at C-8 in 1 was assigned by comparison of the experimental and calculated ECD spectra. Compounds 1 and 2 showed selective antifungal activity against Mucor hiemalis with minimum inhibitory concentration (MIC) values of 8 and 4 μg/mL, respectively. Compounds 5 and 6 exhibited inhibitory activity against Alteraria alternata with an MIC value of 8 μg/mL. In the cytotoxic assay, 2, 5, and 6 displayed moderate in vitro cytotoxicity against the human monocytic cell line (THP-1 cell line), with IC50 values of 40.2, 28.3, and 25.9 μM, respectively. This study indicated that endophytic fungi possess great potential for exploring new bioactive secondary metabolites.

SEASONAL VARIATIONS IN THE AEROMYCOFLORA OF MENTHA ARVENSIS

The survey of aeromycoflora over Mentha arvensis L. plants was carried out at Raipur. During investigation period, a total of 52 fungal species were recorded. Maximum 35 species recorded during winter season and minimum 19 species during summer season. The seasonal variations showed climatic factors influence the occurrence of aeromycoflora. Syncephalastrum racemosum, Alternaria alternate, Aspergillus niger, Cladosporium cladosporoides, Curvularia lunata, and Fusarium oxysporum were recorded in all the three seasons of the year. Emericella nidulans and Aspergillus japonicus were recorded during summer and rainy season. Mucor hiemalis f. silvaticus, Rhizopus oryzae, Curvularia clavata, Fusarium equiseti and Penicillium frequentans during rainy and winter season. Mycelia sterilia (White-ii) was recorded during summer and winter season only. Maximum number of fungal species i.e. 35 was recorded during winter season because of the favourable temperature (29.1ºC) and relative humidity (62.1%). Minimum numbers of fungal species i.e. 19 were recorded during summer season due to unfavourable temperature (38.4ºC) and relative humidity (46.1%).

Rolling and Biological Control Products Affect Microdochium Patch Severity on a Sand‐Based Annual Bluegrass Putting Green

Core Ideas There is evidence that rolling an annual bluegrass putting green 5 d a wk−1 resulted in a lower severity of Microdochium patch. Two biological control products were shown to significantly lower Microdochium patch severity. Neither biological products nor rolling were shown to completely suppress Microdochium patch; therefore, turfgrass quality was not considered acceptable for any treatments. This study offers evidence of alternative disease control techniques for the management of Microdochium patch on annual bluegrass putting greens. The turfgrass disease Microdochium patch caused by the pathogen Microdochium nivale (Fries) Samuels & I.C. Hallett occurs in cool, humid regions. Fungicide applications are the predominant control method, however increasing pesticide restrictions have generated concern regarding their use. The objective of this research was to evaluate the effects of rolling 5 d wk−1 in combination with three biological control products applied every 2 wk on Microdochium patch severity on an annual bluegrass (Poa annua L.) putting green in the absence of traditional fungicides. Biological control products included; BW136N (Trichoderma harzianum Rifai strain T‐22 + Trichoderma virens (J.H. Mill. Giddens & A.A. Foster) Arx strain G‐41), Rhapsody (Bacillus subtilis strain QST 713), and Provide (a microbial solution containing unspecified strains of Bacillus subtilis, Mucor hiemalis, and Trichoderma harzianum) + ReVive (7% humic acid derived from Leonardite). Rolling was effective at inhibiting Microdochium patch as measured by area under disease progress curves (AUDPC) in both years on rolled plots compared to not rolled plots by 47 and 75%, respectively. Applications of BW136N and Rhapsody reduced the severity of Microdochium patch as measured by AUDPC compared to the control (66 and 50% reduction, respectively). The ProVide + ReVive combination did not suppress disease in this study. At the peak of disease, turfgrass quality was greatest when rolling was combined with applications of BW136N or Rhapsody. These findings suggest that rolling as well as BW136N or Rhapsody can inhibit Microdochium patch severity and further research into this management method is warranted.

In vitro evaluation of Syzygium aromaticum L. ethanol extract as biocontrol agent against postharvest tomato and potato diseases

E thanolic extract of dried flower bud of Syzygium aromaticum L. (clove) was investigated to evaluate its antifungal activity against local fungal isolates causing postharvest infections form potato and tomato. Four fungal isolates; Geotrichum candidum, Alternaria alternata, Fusarium oxysporum and Mucor hiemalis were identified. All fungal isolates were found to be inhibited by the extract; whereas the smallest inhibition zone) of S. aromaticum extract was 2.5% for M. hiemalis, A. alternata, G. candidum and 12.5% for F. oxysporum. Quantitative assessment of phytochemical compounds in clove plant revealed the presence of phenolic acids (20.80%); flavonoids (26.81%); tannins (4.90%), saponins (2.60%), alkaloids (1.60%), total protein (17.83%), total carbohydrate (2.23%) and total oil (0.90%). Biochemical profile was revealed by GC/MS which detect 18 different chemical compounds. The major compounds were eugenol (17.27%), trans-caryophyllene (0.50%), humulene (3.33%), anthracenedione (3.35%), cedran-diol (0.61%), citroflex A (5.45%) and lucenin 2 (8.25%). TLC technique and different solvent systems were employed to select the proper one based on its capacity to isolate the maximum number of fluorescent spots in crude extract.Chloroform-acetone-butanol (CAB) 85:15:20 could efficiently separate three bands (A, B and C). Each detected band was individually screened for its antifungal activity against the isolated fungi. Only band C showed a significant antifungal activity. Mass spectroscopy (MS) was used to investigate characteristics, purity as well as expectation of both chemical formula and molecular weight of the isolated compounds; which finally proved that glucoside β-sitosterol was the main compound represented in fraction -C.

Sensitivity of food spoilage fungi to a smoke generator sanitizer

Smoke generator sanitizers are easy to handle and can access to hard-to-reach places. They are a promising alternative for controlling food and air borne fungi, which are known to cause losses in the bakery, meat, and dairy industries. Therefore, the present study aimed to evaluate the efficiency of a smoke generator sanitizer based on orthophenylphenol against ten fungal species relevant to food spoilage. The tests were carried out according to the norms by the French protocol NF-T-72281, with adaptations specific for disinfectants diffused in the air. The tests were performed in an enclosed room of approximately 32 m3. Aspergillus brasiliensis (ATCC 16404), Candida albicans (ATCC 10231), Aspergillus flavus (ATCC 9643), Aspergillus chevalieri (IMI 211382), Cladosporium cladosporioides (IMI 158517), Lichtheima corymbifera (CCT 4485), Mucor hiemalis (CCT 4561), Penicillium commune (CCT 7683), Penicillium polonicum (NGT 33/12), and Penicillium roqueforti (IMI 217568) were exposed to the smoke generator sanitizer for 7 h. The product was efficient against C. albicans and C. cladosporioides, although it was unable to reduce 4 log of the other tested species. The variable sensitivity of the fungal species to the sanitizer emphasizes the importance of confronting a target microorganism (causing problems in a specific food industry) with the sanitizer aiming to control it and obtain satisfactory results in hygiene programs.

Investigating the Role of Gold Nanoparticle Shape and Size in Their Toxicities to Fungi.

Gold nanoparticles (GNPs) are increasingly being used in a wide range of applications, and such they are being released in greater quantities into the environment. Consequently, the environmental effects of GNPs, especially toxicities to living organisms, have drawn great attention. However, their toxicological characteristics still remain unclear. Fungi, as the decomposers of the ecosystem, interact directly with the environment and critically control the overall health of the biosphere. Thus, their sensitivity to GNP toxicity is particularly important. The aim of this study was to evaluate the role of GNP shape and size in their toxicities to fungi, which could help reveal the ecotoxicity of GNPs. Aspergillus niger, Mucor hiemalis, and Penicillium chrysogenum were chosen for toxicity assessment, and spherical and star/flower-shaped GNPs ranging in size from 0.7 nm to large aggregates of 400 nm were synthesised. After exposure to GNPs and their corresponding reaction agents and incubation for 48 h, the survival rates of each kind of fungus were calculated and compared. The results indicated that fungal species was the major determinant of the variation of survival rates, whereby A. niger was the most sensitive and M. himalis was the least sensitive to GNP exposure. Additionally, larger and non-spherical GNPs had relatively stronger toxicities.

Diversity of mucoralean fungi in soils of papaya (Carica papaya L.) producing regions in Mexico

Mexico is the fifth largest producer of papaya worldwide and has recently reported problems with mucoralean fungi in this crop. These fungi are considered saprophytes in the soil and are ubiquitous in nature. In this work, they were isolated from soil in regions of intensive papaya cultivation in Mexico. Collections were made in the states of Colima, Oaxaca and Veracruz in Apr 2016. A total of 72 mucorales fungal isolates was obtained and morphologically characterized and then molecular characterization (28S ribosomal region) of 25 representative isolates was carried out. Phylogenetic analysis of the sequences confirmed the presence of the species Gilbertella persicaria, Rhizopus oryzae, Rhizopus stolonifer, Mucor circinelloides and Mucor hiemalis, which cause soft rot in papaya fruits, therefore, spores of these fungi found in the orchard soils can be considered as a constant source of contamination that affects healthy fruits. Additionally, Choanephora cucurbitarum, Mucor ellipsoideus, Rhizopus homothallicus, Rhizopus microsporus, Rhizopus schipperae, Lichteimia ramosa, Gongronella butleri, Cunninghamella bertholletiae and Cunninghamella blakesleeana were identified which are considered to have agricultural, biotechnological and medical importance.