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1.
Appl Environ Microbiol ; 84(23)2018 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-30242005

RESUMO

Methylmercury is a potent human neurotoxin which biomagnifies in aquatic food webs. Although anaerobic microorganisms containing the hgcA gene potentially mediate the formation of methylmercury in natural environments, the diversity of these mercury-methylating microbial communities remains largely unexplored. Previous studies have implicated sulfate-reducing bacteria as the main mercury methylators in aquatic ecosystems. In the present study, we characterized the diversity of mercury-methylating microbial communities of boreal lake sediments using high-throughput sequencing of 16S rRNA and hgcA genes. Our results show that in the lake sediments, Methanomicrobiales and Geobacteraceae also represent abundant members of the mercury-methylating communities. In fact, incubation experiments with a mercury isotopic tracer and molybdate revealed that only between 38% and 45% of mercury methylation was attributed to sulfate reduction. These results suggest that methanogens and iron-reducing bacteria may contribute to more than half of the mercury methylation in boreal lakes.IMPORTANCE Despite the global awareness that mercury, and methylmercury in particular, is a neurotoxin to which millions of people continue to be exposed, there are sizable gaps in the understanding of the processes and organisms involved in methylmercury formation in aquatic ecosystems. In the present study, we shed light on the diversity of the microorganisms responsible for methylmercury formation in boreal lake sediments. All the microorganisms identified are associated with the processing of organic matter in aquatic systems. Moreover, our results show that the well-known mercury-methylating sulfate-reducing bacteria constituted only a minor portion of the potential mercury methylators. In contrast, methanogens and iron-reducing bacteria were important contributors to methylmercury formation, highlighting their role in mercury cycling in the environment.


Assuntos
Bactérias/metabolismo , Ferro/metabolismo , Lagos/microbiologia , Metano/metabolismo , Compostos de Metilmercúrio/metabolismo , Microbiota , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , DNA Bacteriano/genética , Sedimentos Geológicos/microbiologia , Mercúrio/metabolismo , Oxirredução , Filogenia , RNA Ribossômico 16S/genética
2.
J Int Adv Otol ; 17(4): 372-375, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34309561

RESUMO

Middle ear (ME) benign tumors are rare, and among them is meningioma. An ME meningioma might be isolated or merely a lateral extension of a CPA meningioma. We report a case with presentation of ME effusion followed by the appearance of an aural polyp after repeated myringotomies. Computed tomography (CT) revealed a benign-looking ME and mastoid mass. After debulking and biopsy, it turned out to be a meningioma. However, when MRI was performed, a large CPA meningioma was detected. ME masses are rare; however, they might be encountered, and CT must be performed followed by biopsy or total removal. In case of detection of a tumor with probable intracranial connection as meningioma, an MRI should be performed to exclude intracranial extension.


Assuntos
Neoplasias da Orelha , Neoplasias Meníngeas , Meningioma , Otite Média com Derrame , Neoplasias da Orelha/complicações , Neoplasias da Orelha/cirurgia , Orelha Média/diagnóstico por imagem , Orelha Média/cirurgia , Humanos , Imageamento por Ressonância Magnética , Neoplasias Meníngeas/complicações , Neoplasias Meníngeas/diagnóstico por imagem , Neoplasias Meníngeas/cirurgia , Meningioma/diagnóstico por imagem , Meningioma/cirurgia , Otite Média com Derrame/diagnóstico , Otite Média com Derrame/etiologia
3.
Sci Rep ; 9(1): 518, 2019 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-30679728

RESUMO

The formation of the potent neurotoxic methylmercury (MeHg) is a microbially mediated process that has raised much concern because MeHg poses threats to wildlife and human health. Since boreal forest soils can be a source of MeHg in aquatic networks, it is crucial to understand the biogeochemical processes involved in the formation of this pollutant. High-throughput sequencing of 16S rRNA and the mercury methyltransferase, hgcA, combined with geochemical characterisation of soils, were used to determine the microbial populations contributing to MeHg formation in forest soils across Sweden. The hgcA sequences obtained were distributed among diverse clades, including Proteobacteria, Firmicutes, and Methanomicrobia, with Deltaproteobacteria, particularly Geobacteraceae, dominating the libraries across all soils examined. Our results also suggest that MeHg formation is also linked to the composition of non-mercury methylating bacterial communities, likely providing growth substrate (e.g. acetate) for the hgcA-carrying microorganisms responsible for the actual methylation process. While previous research focused on mercury methylating microbial communities of wetlands, this study provides some first insights into the diversity of mercury methylating microorganisms in boreal forest soils.


Assuntos
Bactérias/metabolismo , Mercúrio/metabolismo , Compostos de Metilmercúrio/metabolismo , Microbiologia do Solo , Bactérias/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Deltaproteobacteria/genética , Deltaproteobacteria/metabolismo , Firmicutes/genética , Firmicutes/metabolismo , Florestas , Mercúrio/análise , Compostos de Metilmercúrio/análise , Metiltransferases/genética , Metiltransferases/metabolismo , Microbiota , Filogenia , Proteobactérias/genética , Proteobactérias/metabolismo , RNA Ribossômico 16S/genética , RNA Ribossômico 16S/metabolismo , Solo/química
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