Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>

ABSTRACT Methylmercury (MeHg) production was compared among nine cultured methanogenic archaea that contain hgcAB, a gene pair that codes for mercury (Hg) methylation. The methanogens tested produced MeHg at inherently different rates, even when normalized to growth rate and Hg availability. Eight o...

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Autores principales:	Cynthia C. Gilmour, Allyson L. Bullock, Alyssa McBurney, Mircea Podar, Dwayne A. Elias
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2018
Materias:	Archaea methylmercury bioavailability complexation cysteine hgcAB Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/90e65f779a2248e0a1cf36902fc22eb7
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spelling	oai:doaj.org-article:90e65f779a2248e0a1cf36902fc22eb72021-11-15T15:53:26ZRobust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>10.1128/mBio.02403-172150-7511https://doaj.org/article/90e65f779a2248e0a1cf36902fc22eb72018-05-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02403-17https://doaj.org/toc/2150-7511ABSTRACT Methylmercury (MeHg) production was compared among nine cultured methanogenic archaea that contain hgcAB, a gene pair that codes for mercury (Hg) methylation. The methanogens tested produced MeHg at inherently different rates, even when normalized to growth rate and Hg availability. Eight of the nine tested were capable of MeHg production greater than that of spent- and uninoculated-medium controls during batch culture growth. Methanococcoides methylutens, an hgcAB+ strain with a fused gene pair, was unable to produce more MeHg than controls. Maximal conversion of Hg to MeHg through a full batch culture growth cycle for each species (except M. methylutens) ranged from 2 to >50% of the added Hg(II) or between 0.2 and 17 pmol of MeHg/mg of protein. Three of the species produced >10% MeHg. The ability to produce MeHg was confirmed in several hgcAB+ methanogens that had not previously been tested (Methanocella paludicola SANAE, Methanocorpusculum bavaricum, Methanofollis liminatans GKZPZ, and Methanosphaerula palustris E1-9c). Maximal methylation was observed at low sulfide concentrations (<100 μM) and in the presence of 0.5 to 5 mM cysteine. For M. hollandica, the addition of up to 5 mM cysteine enhanced MeHg production and cell growth in a concentration-dependent manner. As observed for bacterial Hg methylators, sulfide inhibited MeHg production. An initial evaluation of sulfide and thiol impacts on bioavailability showed methanogens responding to Hg complexation in the same way as do Deltaproteobacteria. The mercury methylation rates of several methanogens rival those of the better-studied Hg-methylating sulfate- and iron-reducing Deltaproteobacteria. IMPORTANCE Archaea, specifically methanogenic organisms, play a role in mercury methylation in nature, but their global importance to MeHg production and the subsequent risk to ecosystems are not known. Methanogenesis has been linked to Hg methylation in several natural habitats where methylmercury production incurs risk to people and ecosystems, including rice paddies and permafrost. In this study, we confirm that most methanogens carrying the hgcAB gene pair are capable of Hg methylation. We found that methylation rates vary inherently among hgcAB+ methanogens but that several species are capable of MeHg production at rates that rival those of the better-know Hg-methylating sulfate- and iron-reducing bacteria. Methanogens may need to be considered equally with sulfate and iron reducers in evaluations of MeHg production in nature.Cynthia C. GilmourAllyson L. BullockAlyssa McBurneyMircea PodarDwayne A. EliasAmerican Society for MicrobiologyarticleArchaeamethylmercurybioavailabilitycomplexationcysteinehgcABMicrobiologyQR1-502ENmBio, Vol 9, Iss 2 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	Archaea methylmercury bioavailability complexation cysteine hgcAB Microbiology QR1-502
spellingShingle	Archaea methylmercury bioavailability complexation cysteine hgcAB Microbiology QR1-502 Cynthia C. Gilmour Allyson L. Bullock Alyssa McBurney Mircea Podar Dwayne A. Elias Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>
description	ABSTRACT Methylmercury (MeHg) production was compared among nine cultured methanogenic archaea that contain hgcAB, a gene pair that codes for mercury (Hg) methylation. The methanogens tested produced MeHg at inherently different rates, even when normalized to growth rate and Hg availability. Eight of the nine tested were capable of MeHg production greater than that of spent- and uninoculated-medium controls during batch culture growth. Methanococcoides methylutens, an hgcAB+ strain with a fused gene pair, was unable to produce more MeHg than controls. Maximal conversion of Hg to MeHg through a full batch culture growth cycle for each species (except M. methylutens) ranged from 2 to >50% of the added Hg(II) or between 0.2 and 17 pmol of MeHg/mg of protein. Three of the species produced >10% MeHg. The ability to produce MeHg was confirmed in several hgcAB+ methanogens that had not previously been tested (Methanocella paludicola SANAE, Methanocorpusculum bavaricum, Methanofollis liminatans GKZPZ, and Methanosphaerula palustris E1-9c). Maximal methylation was observed at low sulfide concentrations (<100 μM) and in the presence of 0.5 to 5 mM cysteine. For M. hollandica, the addition of up to 5 mM cysteine enhanced MeHg production and cell growth in a concentration-dependent manner. As observed for bacterial Hg methylators, sulfide inhibited MeHg production. An initial evaluation of sulfide and thiol impacts on bioavailability showed methanogens responding to Hg complexation in the same way as do Deltaproteobacteria. The mercury methylation rates of several methanogens rival those of the better-studied Hg-methylating sulfate- and iron-reducing Deltaproteobacteria. IMPORTANCE Archaea, specifically methanogenic organisms, play a role in mercury methylation in nature, but their global importance to MeHg production and the subsequent risk to ecosystems are not known. Methanogenesis has been linked to Hg methylation in several natural habitats where methylmercury production incurs risk to people and ecosystems, including rice paddies and permafrost. In this study, we confirm that most methanogens carrying the hgcAB gene pair are capable of Hg methylation. We found that methylation rates vary inherently among hgcAB+ methanogens but that several species are capable of MeHg production at rates that rival those of the better-know Hg-methylating sulfate- and iron-reducing bacteria. Methanogens may need to be considered equally with sulfate and iron reducers in evaluations of MeHg production in nature.
format	article
author	Cynthia C. Gilmour Allyson L. Bullock Alyssa McBurney Mircea Podar Dwayne A. Elias
author_facet	Cynthia C. Gilmour Allyson L. Bullock Alyssa McBurney Mircea Podar Dwayne A. Elias
author_sort	Cynthia C. Gilmour
title	Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>
title_short	Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>
title_full	Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>
title_fullStr	Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>
title_full_unstemmed	Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>
title_sort	robust mercury methylation across diverse methanogenic <named-content content-type="genus-species">archaea</named-content>
publisher	American Society for Microbiology
publishDate	2018
url	https://doaj.org/article/90e65f779a2248e0a1cf36902fc22eb7
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Robust Mercury Methylation across Diverse Methanogenic <named-content content-type="genus-species">Archaea</named-content>

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