Generalist arbuscular mycorrhizal fungi dominated heavy metal polluted soils at two artisanal and small - scale gold mining sites in southeastern Ecuador.

BACKGROUND: Artisanal and small-scale gold mining activities are producing contamination with heavy metals and metalloids (HMM) into soils and water worldwide. The HMM are considered as one of the major abiotic stresses due to their long-term persistence in soil. In this context, arbuscular mycorrhizal fungi (AMF) confer resistance to a variety of abiotic plant stressors including HMM. However, little is known regarding the diversity and composition of AMF communities in heavy metal polluted sites in Ecuador. METHODS: In order to investigate the AMF diversity, root samples and associated soil of six plant species were collected from two sites polluted by heavy metals, located in Zamora-Chinchipe province, Ecuador. The AMF 18S nrDNA genetic region was analyzed and sequenced, and fungal OTUs were defined based on 99% sequence similarity. Results were contrasted with AMF communities from a natural forest and from reforestation sites located in the same province and with available sequences in GenBank. RESULTS: The main pollutants in soils were Pb, Zn, Hg, Cd and Cu with concentrations exceeding the soil reference value for agricultural use. Molecular phylogeny and OTU delimitation showed 19 OTUs, the family Glomeraceae was the most OTU-rich followed by Archaeosporaceae, Acaulosporaceae, Ambisporaceae and Paraglomeraceae. Most of the OTUs (11 of 19) have been found at other locations worldwide, 14 OTUs were proven from nearby non-contaminated sites in Zamora-Chinchipe. CONCLUSION: Our study showed that there are no specialized OTUs at the studied HMM polluted sites, but rather generalists adapted to a wide variety of habitats. Their potential role in phytoremediation approaches remains to be investigated.

Fungi's Swiss Army Knife: Pleiotropic Effect of Melanin in Fungal Pathogenesis during Cattle Mycosis.

Fungal threats to public health, food security, and biodiversity have escalated, with a significant rise in mycosis cases globally. Around 300 million people suffer from severe fungal diseases annually, while one-third of food crops are decimated by fungi. Vertebrate, including livestock, are also affected. Our limited understanding of fungal virulence mechanisms hampers our ability to prevent and treat cattle mycoses. Here we aim to bridge knowledge gaps in fungal virulence factors and the role of melanin in evading bovine immune responses. We investigate mycosis in bovines employing a PRISMA-based methodology, bioinformatics, and data mining techniques. Our analysis identified 107 fungal species causing mycoses, primarily within the Ascomycota division. Candida, Aspergillus, Malassezia, and Trichophyton were the most prevalent genera. Of these pathogens, 25% produce melanin. Further research is required to explore the involvement of melanin and develop intervention strategies. While the literature on melanin-mediated fungal evasion mechanisms in cattle is lacking, we successfully evaluated the transferability of immunological mechanisms from other model mammals through homology. Bioinformatics enables knowledge transfer and enhances our understanding of mycosis in cattle. This synthesis fills critical information gaps and paves the way for proposing biotechnological strategies to mitigate the impact of mycoses in cattle.

Mercury Phytotoxicity and Tolerance in Three Wild Plants during Germination and Seedling Development.

By examining plant responses to heavy metal stress during the early stages of the life cycle, we can predict their tolerance and survival in polluted areas as well as their potential for bioremediation. The objective of our study was to evaluate the effect of exposure to mercury (Hg) on the germination and in vitro development of three plant species: Bidens pilosa, Taraxacum officinale (Asteraceae), and Heliocarpus americanus (Malvaceae). These are wild ecotypes adapted to local edaphoclimatic conditions in southern Ecuador, an area which has been historically affected by artisanal and small-scale gold mining (SSGM). For comparison, we additionally used a known Hg-tolerant plant, Lactuca sativa (Asteraceae). We tested biorelevant concentrations of Hg, equivalent to those occurring in soils affected by SSGM, i.e., up to 4.0 mg/L of Hg. The relative inhibitory effects of the treatments (0.6, 2.0, and 4.0 mg/L of Hg) on the germination percentage were most evident in T. officinale, followed by B. pilosa, while L. sativa and H. americanus were not affected. In terms of the time needed to reach 50% germination (T50), B. pilosa exposed to higher concentrations of Hg showed an increase in T50, while H. americanus showed a significant reduction compared to the control treatment. The reduction in radicle length at 4.0 mg/L Hg compared to the control was more evident in L. sativa (86%) than in B. pilosa (55.3%) and H. americanus (31.5%). We concluded that, in a scenario of Hg contamination in the evaluated concentration range, the grass B. pilosa and the tree H. americanus could have a higher probability of establishment and survival.

Native Hyperaccumulator Plants with Differential Phytoremediation Potential in an Artisanal Gold Mine of the Ecuadorian Amazon.

In tropical forests of southern Ecuador, artisanal gold mining releases heavy metals that become xenobiotic with indefinite circulation and eventual bioaccumulation. Restoration and rehabilitation of degraded mining sites represent a major ecological, technological and economic issue. In this study, we estimate the capacity of two native woody plants to accumulate cadmium (Cd), lead (Pb), zinc (Zn) and mercury (Hg), with the goal of developing effective strategies for phytoremediation of mining sites. Individuals of Erato polymnioides and Miconia sp., as well as their rhizospheric soils, were sampled from a natural zone (NZ) of montane cloud forest, used as a control, and a polluted zone (PZ) subjected to active gold mining. Concentrations of the four heavy metals were analyzed using atomic absorption spectrophotometry. Cd, Zn and Hg concentrations were higher in soils of PZ than NZ. Bioaccumulation (BCF) and translocation factors (TF) showed that Miconia sp. has potential for Cd and Zn phytostabilization, E. polymnioides has potential for Cd and Zn phytoextraction, and both species have potential for Hg phytoextraction. Despite the low productivity of these species, their adaptability to the edaphoclimatic conditions of the region and the possibility of using amendments to increase their biomass could compensate for the effectiveness of these species in reclaiming soils contaminated by mining.

Erato polymnioides - A novel Hg hyperaccumulator plant in ecuadorian rainforest acid soils with potential of microbe-associated phytoremediation.

Mercury (Hg) accumulation capacity was assessed in three plant species (Axonopus compressus, Erato polymnioides, and Miconia zamorensis) that grow on soils polluted by artisanal small-scale gold mines in the Ecuadorian rainforest. Individuals of three species were collected at two sampling zones: i) an intensive zone (IZ, 4.8 mg Hg kg-1 of soil) where gold extraction continues to occur, and ii) a natural zone (NZ, 0.19 mg Hg kg-1 of soil). In addition, the percentage of arbuscular mycorrhizal fungi (AMF) colonization was determined in plant roots and seven fungal morphotypes isolated from rhizospheric soil. Results suggest a facilitation role of native and pollution adapted AMF on Hg phytoaccumulation. E.g., E. polymnioides increased Hg accumulation when growing with greater AMF colonization. We concluded that E. polymnioides is a good candidate for the design of microbe-assisted strategies for Hg remediation at gold mining areas. The consortia between E. polymnioides and the AMF isolated in this study could be instrumental to get a deeper understanding of the AMF role in Hg phytoaccumulation.

Cambios en la biomasa de raíces y micorrizas arbusculares en cultivos itinerantes del Amazonas Venezolano / Changes in root biomass and arbuscular mycorrhizae in shifting crops of the Venezuelan Amazon / Mudanças na biomassa de raízes e micorrizas arbusculares em cultivos itinerantes do Amazonas Venezolano

La asignación de biomasa a la producción de raíces finas en plantas terrestres y la formación de asociaciones simbióticas micorrízico arbusculares (MA) constituyen de importantes adaptaciones en condiciones de baja fertilidad. En un mosaico de agricultura itinerante, conformado por dos áreas de cultivo (conucos), dos áreas de 2-4 y de 4-6 años de abandono después de ser cultivadas (barbechos) y un área de bosque lluvioso poco perturbado, se compararon la biomasa de raíces finas (diámetro <2mm), el potencial infectivo del suelo y la densidad de esporas de hongos micorrízicos arbusculares (HMA). Muestras de suelo y raíces fueron colectadas al azar en los primeros 15cm de profundidad. Se observó una proporción significativamente mayor de raíces finas en el manto superficial de raíces (estera) respecto al suelo mineral del bosque. La biomasa de raíces finas disminuyó marcadamente y la estera de raíces fue eliminada con la conversión de bosque a conuco; sin embargo, se formó una estera de raíces incipiente en un periodo de barbecho de seis años. La colonización MA, el número de esporas y el potencial infectivo del suelo aumentaron significativamente en el conuco y en los barbechos respecto al bosque. Los resultados muestran que los efectos adversos que pudiese tener el fuego sobre los HMA son revertidos durante la etapa de cultivo, debido posiblemente a la siembra de plantas altamente susceptibles a la colonización MA. Estas tendencias apoyan el carácter sustentable de la agricultura itinerante de la etnia piaroa cuando es practicada en su forma tradicional.

The allocation of biomass to the production of fine roots in terrestrial plants and arbuscular mycorrhizal (AM) symbiotic partnerships are important adaptations under conditions of low fertility. In a mosaic of shifting cultivation, comprising two growing areas (conucos) and two 2-4 and 4-6 years deserted areas after being cultivated (fallow), and a little disturbed rain forest area, differences in fine root biomass (diameter <2mm), infective potential of soil and spore density of arbuscular mycorrhizal fungi (AMF) were assessed. Roots and soil samples were collected at random in the first 15cm of depth. There was a significantly higher proportion of fine roots in the mantle root surface (mat) with respect to the mineral soil of the forest. Fine root biomass decreased markedly and the root mat was eliminated with the conversion of forest to conuco; however, within a six year fallow period an incipient root mat formed. AM colonization, number of spores and infective potential of the soil increased significantly in conuco and fallows with respect to the forest. The results show that the adverse effects that fire might have on the AMF were reversed during cultivation, possibly due to the planting of species that are highly susceptible to AM colonization. These trends support the sustainable nature of the piaroa ethnic group shifting cultivation, when it is practiced in its traditional form.

A designação de biomassa a produção de raízes finas em plantas terrestres e a formação de associações simbióticas micorrízico arbusculares (MA) constituem adaptações de importância em condições de baixa fertilidade. Em um mosaico de agricultura itinerante, conformado por duas áreas de cultivo (parcelas), duas áreas de 2-4 e de 4-6 anos de abandono depois de ser cultivadas (pousios) e uma área de bosque chuvoso pouco perturbado, se compararam a biomassa de raízes finas (diâmetro <2mm), o potencial infectivo do solo e a densidade de esporas de fungos micorrízicos arbusculares (HMA). Amostras de solo e raízes foram coletadas aleatoriamente nos primeiros 15cm de profundidade. Observou-se uma proporção significativamente maior de raízes finas no manto superficial de raízes (estera) relativo ao solo mineral do bosque. A biomassa de raízes finas diminuiu marcadamente e a esteira de raízes foi eliminada com a conversão de bosque a parcelas; No entanto, se formou uma esteira de raízes incipiente em um período de pousio de seis anos. A colonização MA, o número de esporas e o potencial infectivo do solo aumentaram significativamente nas parcelas e nos pousios relativo ao bosque. Os resultados mostram que os efeitos adversos que pudese ter o fogo sobre os HMA são revertidos durante a etapa de cultivo, devido possivelmente a plantações altamente susceptíveis à colonização MA. Estas tendências apóiam o caráter sustentável da agricultura itinerante da etnia piaroa quando é praticada em sua forma tradicional.