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PRODID:-//Memento EPFL//
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SUMMARY:Metals\, minerals and microbes: Geosymbiotic interactions of the M
 n cycle
DTSTART:20111011T161500
DTSTAMP:20260929T042750Z
UID:d5247ecddceb51e99de9f833894075ec74dcbbda998fc9e63e68ee16
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Jasquelin Peña\, Institute of Mineralogy and Geochemistry\
 , UNIL\nBiogenic manganese oxides (MnO2) are ubiquitous nanoparticulate mi
 nerals that contribute to the adsorption of nutrient and toxicant metals\,
  the oxidative degradation of various organic compounds\, and the respirat
 ion of metal-reducing bacteria in aquatic and terrestrial environments.  T
 he formation of these minerals is catalyzed by a diverse and widely-distri
 buted group of bacteria and fungi\, often through the enzymatic oxidation 
 of aqueous Mn(II) to Mn(IV).  The biogenic Mn(IV) oxide found in field set
 tings\, as well as that produced by model bacteria in laboratory culture\,
  is typically a poorly crystalline layer-type hexagonal birnessite enmeshe
 d in an organic matrix of bacterial cells and extracellular polymeric subs
 tances.  In this talk\, I describe the reactivity of various trace metals 
 in preformed and actively-growing Pseudomonas putida-birnessite assemblage
 s. We combined sorption and microbiological experiments with X-ray absorpt
 ion spectroscopy and first-principles calculations based on density functi
 onal theory to elucidate the mechanisms of metal sorption by biogenic MnO2
  and to quantify the influence of elevated metal concentrations on bacteri
 al growth\, enzymatic MnO2 precipitation\, and metal attenuation. This res
 earch advances fundamental understanding of metal retention by biogenic Mn
 O2 nanoparticles and highlights the geosymbiotic nature of metal microbe-m
 ineral interactions that regulate the concentrations and distribution of t
 oxicant metals in contaminated ecosystems.
LOCATION:GR C0 01
STATUS:CONFIRMED
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