Preface

These proceedings are the output of the 6th International Conference of Indonesia Forestry Researchers - Stream 1 Emerging Environmental Quality for Better Living (INAFOR 2021 Stream 1) that was organised virtually by the Center for Standardization of Environmental Quality Instruments, Agency for Standardization of Environment and Forestry Instruments, Ministry of Environment and Forestry of Republic of Indonesia on 08 September 2021. The conference was held during the pandemic of covid-19, and due to the international and national travel restriction, the conference was carried out via online platform. The conference presented and discussed the current environmental issues in Indonesia including monitoring of environmental pollution, role of environmental laboratory and set up national standard of environmental monitoring; circular economy and environmental quality management by businesses and relevant activities; mercury pollution, progress of National Action Plan for mercury reduction and elimination as a part of the ratification of Minamata Convention on Mercury; medical wastes and disposal concerning Covid-19 pandemic and antibiotically resistance; domestic waste, hazardous and poisonous materials and wastes; restoration and remediation of contaminated lands; and freshwater litters. The conference arranged into two sessions; they were oral presentations from keynote speakers in the plenary session and scholar presenters in the parallel session. In the first session, the keynote speakers were each allocated 25-30 minutes for presentation and 30 minutes for panel discussion (Q and A). There were four international keynote speakers contributed to the plenary session. Firstly, Prof. Dr. Satoshi Murao represented Daiichi Institute of Technology, Japan, talked about Mercury Reduction from Artisanal Gold Mining Sector. Secondly, Prof. Dr. Seca Gandaseca from University Putra Malaysia presented Water Quality of Tropical Forest Ecosystems. Thirdly, the Director for Performance Evaluation of Hazardous Waste and Non-Hazardous Waste Management of the Ministry of Environment and Forestry of Republic of Indonesia discussed The Regulation of Covid-19 Medical Waste Management in Indonesia. The last, Dr. Nur Sumedi, S.Pi., M.P., as Acting Secretary of Agency for Standardization of Environment and Forestry Instruments, Ministry of Environment and Forestry of Republic of Indonesia discussed The Role of Science and Technology to Support the Improvement of Environmental Quality. In the parallel session, selected papers were presented by scholars in 10 minutes, and followed by 5 minutes discussion. The parallel session was divided into four different meeting room. Two rooms discussed the topic of anthropogenic pressure on environment and COVID-19 related mitigation: one room talked water quality of various ecosystems and another room conferred mercury, lead, and persistent organic pollutants (POPS) contamination. The conference was successfully run via a “Zoom” application meeting. At the plenary session, all participants joined in a plenary meeting “zoom” room. After this session, the participants were then assigned into a “breakout” room based on their academic or professional background. Finally, they re-joined the plenary room for the wrap up and closing ceremony. Lastly, we would like to express our sincere gratitude to the organizing committee and the members of reviewers for their kind assistance in reviewing the papers. We also thank to the chairman, scientific committees, keynote speakers, and all participants. We greatly thanks to the publisher for publishing the selected papers. We are looking forward to the next collaboration. List of Editors are available in this pdf.

Stable isotope fractionation reveals similar atomic level controls during aerobic and anaerobic microbial Hg transformation pathways

Mercury (Hg) is a global pollutant and potent neurotoxin that bioaccumulates in food webs as monomethylmercury (MeHg). The production of MeHg is driven by anaerobic and Hg redox cycling pathways such as Hg reduction, which control the availability of Hg to methylators. Anaerobes play an important role in Hg reduction in methylation hotspots, yet their contributions remain underappreciated due to how challenging these pathways are to study in the absence of dedicated genetic targets and low levels of Hg 0 in anoxic environments. In this study we used Hg stable isotope fractionation to explore Hg reduction during anoxygenic photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. We show that cells preferentially reduce lighter Hg isotopes in both metabolisms leading to mass-dependent fractionation, but mass-independent fractionation commonly induced by UV-visible light is absent. Due to variability associated with replicated experiments, we could not discern whether dedicated physiological processes drive Hg reduction during photosynthesis and fermentation. However, we demonstrate that fractionation is affected by the interplay between pathways controlling Hg recruitment, accessibility, and availability alongside metabolic redox reactions. The combined contributions of these processes lead to isotopic enrichment during anoxygenic photosynthesis that is in between the values reported for anaerobic respiratory microbial Hg reduction and abiotic photoreduction. Isotope enrichment during fermentation is closer to what has been observed in aerobic bacteria that reduce Hg through dedicated detoxification pathways. Our work suggests that similar controls likely underpin diverse microbe-mediated Hg transformations that affect Hg’s fate in oxic and anoxic habitats. IMPORTANCE Anaerobic and photosynthetic bacteria that reduce mercury affect mercury delivery to microbes in methylation sites that drive bioaccumulation in food webs. Anaerobic mercury reduction pathways remain underappreciated in the current view of the global mercury cycle because they are challenging to study, bearing no dedicated genetic targets to establish physiological mechanisms. In this study we used stable isotopes to characterize the physiological processes that control mercury reduction during photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. The sensitivity of isotope analyses highlighted the subtle contribution of mercury uptake towards the isotope signature associated with anaerobic mercury reduction. When considered alongside the isotope signatures associated with microbial pathways for which genetic determinants have been identified, our findings underscore the narrow range of isotope enrichment that is characteristic of microbial mercury transformations. This suggests that there exist common atomic-level controls for biological mercury transformations across a broad range of geochemical conditions.

Common physiological processes control mercury reduction during photosynthesis and fermentation

ABSTRACTMercury (Hg) is a global pollutant and potent neurotoxin that bioaccumulates in food webs as monomethylmercury (MeHg). The production of MeHg is driven by anaerobic and Hg redox cycling pathways such as Hg reduction, which control the availability of Hg to methylators. Anaerobes play an important role in Hg reduction in methylation hotspots, yet their contributions remain underappreciated due to how challenging these pathways are to study in the absence of dedicated genetic targets and low levels of Hg0 in anoxic environments. In this study we used Hg stable isotope fractionation to explore Hg reduction during anoxygenic photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. We show that cells preferentially reduce lighter Hg isotopes in both metabolisms leading to mass-dependent fractionation, but mass-independent fractionation commonly induced by UV-visible light is absent. We show that isotope fractionation is affected by the interplay between pathways controlling Hg recruitment, accessibility, and availability alongside metabolic redox reactions. The combined contributions of these processes lead to isotopic enrichment during anoxygenic photosynthesis that is in between the values reported for anaerobic respiratory microbial Hg reduction and abiotic photoreduction. Isotope enrichment during fermentation is closer to what has been observed in aerobic bacteria that reduce Hg through dedicated detoxification pathways. These results demonstrate that common controls exist at the atomic level for Hg reduction during photosynthesis and fermentation in H. modesticaldum. Our work suggests that similar controls likely underpin diverse microbe-mediated Hg transformations that affect Hg’s fate in oxic and anoxic habitats.IMPORTANCEAnaerobic and photosynthetic bacteria that reduce mercury affect mercury delivery to microbes in methylation sites that drive bioaccumulation in food webs. Anaerobic mercury reduction pathways remain underappreciated in the current view of the global mercury cycle because they are challenging to study, bearing no dedicated genetic targets to establish physiological mechanisms. In this study we used stable isotopes to show that common physiological processes control mercury reduction during photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. The sensitivity of isotope analyses highlighted the subtle contribution of mercury uptake towards the isotope signature associated with anaerobic mercury reduction. When considered alongside the isotope signatures associated with microbial pathways for which genetic determinants have been identified, our findings underscore the narrow range of isotope enrichment that is characteristic of microbial mercury transformations. This suggests that there exist common atomic-level controls for biological mercury transformations across a broad range of geochemical conditions.