| 1. |
- Bravo, Andrea G., et al.
(author)
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Methanogens and iron-reducing bacteria : the overlooked members of mercury-methylating microbial communities in boreal lakes
- 2018
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In: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 84:23
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Journal article (peer-reviewed)abstract
- ABSTRACT: 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.
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| 2. |
- Bravo, Andrea Garcia, et al.
(author)
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Methanogens and Iron-Reducing Bacteria : the Overlooked Members of Mercury-Methylating Microbial Communities in Boreal Lakes
- 2018
-
In: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 84:23
-
Journal article (peer-reviewed)abstract
- 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 di- versity of these mercury-methylating microbial communities remains largely unex- plored. Previous studies have implicated sulfate-reducing bacteria as the main mer- cury methylators in aquatic ecosystems. In the present study, we characterized the diversity of mercury-methylating microbial communities of boreal lake sediments us- ing high-throughput sequencing of 16S rRNA and hgcA genes. Our results show that in the lake sediments, Methanomicrobiales and Geobacteraceae also represent abun- dant members of the mercury-methylating communities. In fact, incubation experi- ments with a mercury isotopic tracer and molybdate revealed that only between 38% and 45% of mercury methylation was attributed to sulfate reduction. These re- sults suggest that methanogens and iron-reducing bacteria may contribute to more than half of the mercury methylation in boreal lakes.
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| 3. |
- Molander, Peter, et al.
(author)
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Internet-based acceptance and commitment therapy for psychological distress experienced by people with hearing problems: a pilot randomized controlled trial
- 2018
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In: Cognitive Behaviour Therapy. - : Informa UK Limited. - 1650-6073 .- 1651-2316. ; 47:2, s. 169-184
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Journal article (peer-reviewed)abstract
- © 2017 Swedish Association for Behaviour Therapy. Psychological distress is common among people with hearing problems, but treatments that specifically target this aspect have been almost non-existent. In this pilot randomized controlled trial, an eight-week long Internet-based treatment, informed by Acceptance and Commitment Therapy, was administered to explore the feasibility and efficacy of such a treatment. Included participants were randomized to either treatment (n=31) or wait-list control (n=30) condition. All participants were measured prior to randomization and immediately after treatment ended using standardized self-report instruments measuring hearing-related emotional and social adjustment (Hearing Handicap Inventory for the Elderly–S, HHIE-S), quality of life (Quality of Life Inventory, QOLI), and symptoms of depression and anxiety (Patient health Questionnaire, PHQ-9 and Generalized Anxiety Disorder scale, GAD-7). Linear mixed effects regression analysis using the full intention-to-treat sample demonstrated that the treatment had superior outcomes on the main outcome measure as compared with the control group, Cohen’s d=0.93, 95% CI [0.24, 1.63]. The benefits of treatment over control were also evident in scores of depression, Cohen’s d=0.61, 95% CI [0.04, 1.19], and quality of life, Cohen’s d=0.88, 95% CI [0.14, 1.61]. The results provide preliminary support for Internet-delivered acceptance and commitment therapy as a potentially effective treatment of psychological symptoms associated with hearing problems.
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| 4. |
- Molander, Peter, et al.
(author)
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Internet-Based Acceptance and Commitment Therapy for Psychological Distress Experienced by People With Hearing Problems: Study Protocol for a Randomized Controlled Trial
- 2015
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In: American Journal of Audiology. - : American Speech-Language-Hearing Association. - 1059-0889 .- 1558-9137. ; 24:3, s. 307-310
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Journal article (peer-reviewed)abstract
- © 2015 American Speech-Language-Hearing Association. Purpose: Psychological distress and psychiatric symptoms are prevalent among people with hearing loss or other audiological conditions, but psychological interventions for these groups are rare. This article describes the study protocol for a randomized controlled trial for evaluating the effect of a psychological treatment delivered over the Internet for individuals with hearing problems and concurrent psychological distress. Method: Participants who are significantly distressed will be randomized to either an 8-week Internet-delivered acceptance-based cognitive behavioral therapy (i.e., acceptance and commitment therapy [ACT]), or wait-list control. We aim to include measures of distress associated with hearing difficulties, anxiety, and depression. In addition, we aim to measure acceptance associated with hearing difficulties as well as quality of life. Conclusion: The results of the trial may further our understanding of how to best treat people who present problems with both psychological distress and hearing in using the Internet.
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