PubMed · 306510
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1978-03-17. [Pathogen differentiation is necessary].. https://pubmed.ncbi.nlm.nih.gov/306510/
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As Earth's principal reservoir of organic carbon and microbial biomass, the deep subsurface hosts microorganisms capable of mobilizing this once-sequestered carbon. Contrary to standard assumptions of eukaryotic scarcity, this study documents abundant fungal communities, ranging from 4.2 × 103 to 6.8 × 103 fungal cells ml-1, across a methane-producing organic-rich shale 247-556 meters below the surface. Although fungal:bacterial cell ratios ranged from 1:7028 to 1:713, application of biomass conversion factors developed for oceanic systems yielded a median fungal:bacterial biomass ratio of 1:4.7. 16S ribosomal ribonucleic acid (rRNA) gene amplicons revealed bacterial and archaeal communities mirroring those found in well-characterized extremophilic, carbon-degrading environments, while sequencing of 18S rRNA gene and internal transcribed spacer rRNA spacer amplicons collectively identified a eukaryotic hotspot with 689 fungal operational taxonomic units across six phyla. The dominant fungal classes, Agaricomycetes and Dothideomycetes, are well-established degraders of recalcitrant carbon compounds at the surface, suggesting they may similarly contribute to organic matter degradation and ecosystem maintenance in the subsurface. Cultivation and isolation efforts yielded 205 fungal strains, including 13 candidate novel taxa, underscoring the deep subsurface as an underexplored eukaryotic habitat. Stable carbon isotopes indicate methane is predominantly generated via microbial conversion of the fossil carbon, while water isotopes suggest in situ geochemical conditions have been relatively stable since the Late Pleistocene, with subglacial recharge as a plausible mechanism for microbial introduction. Collectively, these findings suggest that fungi are underrecognized contributors to organic matter transformation and functional diversity in the deep biosphere, revealing a critical gap in our understanding of deep subsurface ecosystem processes.
The effects of mycorrhizal inoculation and increasing soil P levels on the expression of total proteins and peroxidase activity on passion fruit roots were evaluated. The experimental design was entirely at random, with four treatments of inoculation (a--control; b--Gigaspora albida; c--Scutellospora heterogama; d--mixture of G. albida, G. margarita, S. heterogama, and Glomus clarum) x three levels of soil P (4, 11, and 30 mg/dm3 of soil), each with three replicates. Plants were harvested 70 days after inoculation, when root colonization, shoot P level, protein content, and enzymatic activity of peroxidase (PAGE--7%) on root extract were evaluated. Regarding protein, there was no significant difference among the treatments, except between those roots receiving mixed inoculum and 11 mg P/dm3 of soil. Effect of P on protein concentration, when compared with the inoculation effect was observed. For peroxidase, there was an eletrophoretic band common to all treatments (rf: 0.43) and another that was absent only in noncolonized plants, grown in soil with lower P (rf: 0.46). Mycorrhizal specific bands were not present but a small decrease of intensity of bands in noncolonized plants was observed. Conversely, the control roots presented a single band (rf: 0.33) not observed in the other extracts, that may demonstrate an inhibitory effect of AMF on some host activities. The data showed the influence of P level in soil on the protein expression of roots, suggesting the influence of this nutrient on root genetic expression as well as on the mechanisms of symbiotic control/recognition.
The objective of this work was to estimate the disappearance of pyrimethanil, the active ingredient of Mythos 300 SC, at present, commonly used for the protection of greenhouse vegetables against diseases of fungal origin. Disappearance trends of the chemical deposits were studied on tomato plants grown in commercial greenhouses sprayed with a homogeneous 0.15% aqueous solution of the plant protection product. It was found that, on average, pyrimethanil residues on ripening fruits dropped by half and reached detection limit level in 5.7 and 13.7 days after Mythos 300 SC application, respectively. Pyrimethanil residues on tomato leaves dropped by half within 4.0 days and reached detection limit level in the first 10.5 days. Therefore, in conditions of high infection pressure, there is a need to repeat the fungicide application as early as after 3 or 4 days after previous application of Mythos 300 SC.