Phylogeny of prokaryotes involved in mercury speciation in free-living and particulate-attached fractions in Minamata Bay, Japan

IF 1.3 4区地球科学 Q4 OCEANOGRAPHY

Journal of Oceanography Pub Date : 2024-09-17 DOI:10.1007/s10872-024-00735-7

Yuya Tada, Kenji Yoshino, Katsumasa Yamada, Akito Matsuyama, Kohji Marumoto

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Abstract

Marine prokaryotes are involved in mercury (Hg) speciation in marine environments. However, information regarding the specific microbial lineages contributing to Hg speciation (namely, methylation, demethylation, and reduction) in seawater remains limited. In this study, we investigated the genes involved in methylmercury (MeHg) demethylation (merB), Hg reduction (merA), and Hg methylation (hgcA and hgcB) using a metagenome analysis encompassing free-living (FL; 0.2–3 µm) and particle-attached (PA; > 3 µm) fractions in April and June in Minamata Bay, Japan. We analyzed the total Hg (THg) and MeHg concentrations in dissolved, small particulate (0.2–3 µm), and large particulate (> 3 µm) fractions. Hg analysis showed no significant differences in THg and MeHg concentrations among the three fractions. However, THg and MeHg in the pooled particulate (fractions were higher than those in the dissolved fractions) in June. As for the Hg-related genes, a high merB abundance rather than merA was observed when compared using all samples, suggesting that microbial MeHg demethylation could be prominent rather than Hg reduction in the seawater column. Phylogenetic analyses revealed that Alphaproteobacteria and Actinobacteria were dominant in the total merA and merB-like sequences, respectively. For both merA and merB genes, some lineages appeared in either or both FL and PA fractions. A deltaproteobacteria-like hgcA was also detected in the PA fraction in April. Therefore, the link between distinct phylogenetic lineages within the PA and FL fractions could be significant for Hg speciation in Minamata Bay.

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日本水俣湾自由生物和微粒附着物中参与汞分化的原核生物的系统发育

海洋原核生物参与了海洋环境中的汞（Hg）分化。然而，有关在海水中促进汞物种形成（即甲基化、去甲基化和还原）的特定微生物系的信息仍然有限。在本研究中，我们利用元基因组分析方法，调查了日本水俣湾四月和六月的甲基汞（MeHg）脱甲基（merB）、汞还原（merA）和汞甲基化（hgcA 和 hgcB）基因，包括自由生活（FL；0.2-3 µm）和颗粒附着（PA；> 3 µm）部分。我们分析了溶解物、小颗粒物（0.2-3 微米）和大颗粒物（3 微米）中的总汞（THg）和甲基汞浓度。汞分析表明，三种馏分中的总汞和甲基汞浓度没有明显差异。不过，6 月份的总颗粒物（馏分）中的三卤甲烷和甲基汞含量高于溶解馏分。在汞相关基因方面，与所有样本相比，merB 的丰度较高，而 merA 的丰度较低。系统进化分析表明，在全部 merA 和 merB 样序列中，变形菌和放线菌分别占主导地位。在 merA 和 merB 基因中，一些菌系同时出现在 FL 和 PA 部分中。在四月份的 PA 部分中还检测到类似于 deltaproteobacteria 的 hgcA。因此，PA 和 FL 部分中不同系统发生系之间的联系可能对水俣湾的汞物种分化具有重要意义。

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来源期刊

Journal of Oceanography 地学-海洋学

CiteScore

3.50

自引率

13.00%

发文量

审稿时长

6-12 weeks

期刊介绍： The Journal of Oceanography is the official journal of the Oceanographic Society of Japan and open to all oceanographers in the world. The main aim of the journal is to promote understandings of ocean systems from various aspects including physical, chemical, biological, geological oceanography as well as paleoceanography, etc. The journal welcomes research focusing on the western North Pacific and Asian coastal waters, but the study region is not limited to the Asian Pacific. The journal publishes original articles, short contributions, reviews, and correspondence in oceanography and related fields.