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SUMMARY:EESS seminar talk on "Biogeochemical Controls on Arsenic Methylati
 on and Demethylation in Rice Paddy Soils"
DTSTART:20260428T121500
DTEND:20260428T131500
DTSTAMP:20260415T235845Z
UID:2ac8eb3449f2eb2e951a98f610866dcc8fbec7e72316c7d8b4449b63
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Matthew Reid\, Cornell University \nAbstract:\n\n\nArse
 nic methylation and demethylation reactions influence arsenic speciation a
 nd fate in rice paddy soils\, and understanding the balance between methyl
 ation and demethylation is important for assessing risks of arsenic toxici
 ty in rice. Rice paddy soils are rich in organic carbon\, and the conventi
 onal understanding has been that organic carbon enhances microbial arsenic
  methylation by fueling microbial activity.  This presentation will descr
 ibe a series of recent investigations — spanning pure culture to greenho
 use-scale experiments — that challenge this conceptual model.  First\, 
 the presentation will describe the role of carbon catabolite repression (C
 CR) in regulating cellular uptake and subsequent enzymatic methylation of 
 arsenite.  A combination of biosensor\, gene expression\, and arsenic spe
 ciation analyses demonstrate that sugars lead to CCR and a decrease in ars
 enic methylation\, while low molecular weight organic acids do not impact 
 arsenite uptake.  The presentation will then examine couplings between me
 thanogenesis and arsenic demethylation\, wherein a greater abundance of me
 thylotrophic carbon substrates (methanol\, methylamines) promote arsenic d
 emethylation by methanogens and limit the accumulation of methylated arsen
 ic compounds.  A genome-resolved metatranscriptomic analysis of anaerobic
  soil slurry experiments resolved links between methylotrophic substrate u
 tilization and arsenic demethylation\, while greenhouse experiments showed
  that higher levels of methanogenesis in soils were associated with lower 
 concentrations of methylated arsenic in rice grains. Taken together\, thes
 e results provide a more nuanced understanding of how utilization of disti
 nct carbon substrates impacts arsenic methylation-demethylation dynamics\,
  and provides mechanistic insights into how paddy soil management practice
 s influence arsenic speciation in rice.\n\n\n\n\n\nBiography:\n\n\n\nDr. M
 atthew Reid is an associate professor in the School of Civil and Environme
 ntal Engineering at Cornell University and directs the Biogeochemistry and
  Ecosystem Engineering Research Group. His research program focuses on bio
 geochemical element cycling in natural and nature-based systems with appli
 cations to water quality.  Research in the Reid Group spans physical sca
 les and integrates mechanistic and molecular-level investigation with fiel
 d-scale observation to build quantitative models for contaminant dynamics 
 in complex biogeochemical systems. Dr. Reid's research has been recognized
  with early career awards from NSF and DOE. Dr. Reid was a postdoctoral sc
 ientist in the Environmental Microbiology Laboratory at EPFL\, and complet
 ed his Ph.D. in Civil and Environmental Engineering at Princeton Universit
 y.\n\n
LOCATION:GC B1 10 https://plan.epfl.ch/?room==GC%20B1%2010 https://epfl.zo
 om.us/j/69011077410
STATUS:CONFIRMED
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