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Microbial Mats and Microbialites: Ingredients of Lithification

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Microbial Mats and Microbialites: Ingredients of Lithification Microbial Mats and Microbialites: Ingredients of Lithification Pieter T. Visscher, Joan Bernhard, Brendan Burns, Olivier Braissant, Lindsay Collins, Alan Decho, David Des Marais, Christophe Dupraz, Ginny Edgcomb, Jamie Foster, Kim Gallagher, Kristen Myshrall, Brett Neilan, Kim Gallagher, Ricardo Jahnert, Therese Morris, Noah Planavsky, Pamela Reid, Roger Summons, Malcolm Walter Center for Integrative Geosciences Department of Marine Sciences University of Connecticut – Storrs, USA Symposium on Research and Conservation: South West Australian WA’s Microbialites, Kensington, Oct 2012 Outline of this talk: - Microbial Mats 101 - Microbial Mats vs. Microbialites - Three Ingredients of Lithification - Words of Warning PRE - MAT DEPTH IPRENITIAL - MAT MAT DEPTH N2-Fixing Cyano’s INITIALPRECYANO’S - MAT MATAND A EROBIC HETEROROPHS DEPTH N2-Fixing Cyano’s Cyanobacteria Aerobic Heterotrophs AINITIALPRENAEROBIC - MAT MAT H ETEROTROPHS APPEAR DEPTH N2-Fixing Cyano’s Cyanobacteria Aerobic Heterotrophs Anaerobic Heterotrophs MATUREINITIALPRE M - ATMAT :MAT M ETABOLLICALLY DIVERSE DEPTH N2-Fixing Cyano’s Cyanobacteria Aerobic Heterotrophs Anaerobic Heterotrophs Anoxygenic Phototrophs Sulfide Oxidizers Characteristics of Microbial Mats Organo-sedimentary biofilms, some almost completely inorganic, typically containing copious amounts of EPS Bind and trap sediment; precipitate/dissolve minerals Lamination due to stratification of phototrophs (light regime), with strong resemblance to fossil record Inventors of oxygenic photosynthesis High productivity (up to 5.5 g C m-2 d-1) Semi-closed; highly efficient in element cycling (tight coupling of P and R) Limited number of functional groups of microbes 5 cm or, limited “heap of genes to make them tick” Stromatolitic reefs Thrombolitic reefs Foster, Dupraz, Reid, Visscher crusty (% sequence similarity) soft Ingredients of Lithification 1. The Alkalinity Engine Microbial Metabolism: Photosynthesis removal of CO2 from a bicarbonate buffered environment results in an increase in alkalinity: CO2 + H2O [CH2O] + O2 - - HCO3 CO2 + OH 2+ - + Ca + HCO3 CaCO3 + H + - H + OH H2O - 2+ sum: 2HCO3 + Ca [CH2O] + CaCO3+ O2 +1 CaCO3 per CO2 fixed Metabolic pathways in (lithifying) microbial mats Dupraz et al. 2009 Metabolic pathways in (lithifying) microbial mats Dupraz et al. 2009 SI = log (IAP/kSP) = log (Q/k) 2+ 2- IAP = ion activity product = {Ca } x {CO3 } kSP = solubility product constant 2+ 2- Ca + CO3 CaCO3 2+ 2- -8.42 -8.22 Ca x CO3 /CaCO3 = 10 (calcite);10 (aragonite) IAP > kSP then supersaturated and precipitation likely photosynthesis (cyanobacteria) - 2+ 2HCO3 + Ca [CH2O] + CaCO3 + O2 - [CH2O] + CaCO3 + O2 HS + 2O2 + CaCO3 - 2+ - 2+ 2- 2HCO3 + Ca HCO3 + Ca + SO4 2- 2+ - - 2[CH2O] + SO4 + Ca + OH CaCO3 + CO2 + 2H2O + HS SRB metabolism using ΔDIC ΔTA ΔH+ /mole eq/mole donor donor ethanol: 2- - - - 2C2H6O + 3SO4 + OH 4HCO3 + 3HS + 3H2O 2 3 +½ lactate: - 2- - - - 2C3H5O3 + 3SO4 + OH 6HCO3 + 3HS + H2O 3 3 +½ formate: - 2- - - - 4CHO2 + SO4 + H2O 4HCO3 + HS + OH 1 ½ -¼ acetate: - 2- - - C2H3O2 + SO4 2HCO3 + HS 2 1 0 Ingredients of Lithification 2. Extracellular Organic Matrix EPS Matrix CaCO3 Precipitate Ooid Ooid Key Role in: 1.Precipitation (CaCO3) 2.Chemical Communication (Quorum Sensing) 3. Sediment Stabilization (Gel Formation), etc Surface biofilm in Bahamian stromatolite Initial EPS Production and Ca2+ Binding Calcium binding capacity 0.15 g Ca2+/g EPS (0.29 g/g) Acid-Base Titration “S” group Amino group Carboxyl group FT-IR Spectrometry After: Braissant, 2005 Potential Consumption of EPS Substrate AR SR 2- (dO2/dt) (dS /dt)*2 µmol/.ml slurry.h Endogenous 6.4±0.8 0.5±0.2 Acetate 32.1±3.3 12.8±3.8 Lactate 26.9±1.9 13.0±5.9 Glucose 37.2 ±2.5 8.0±2.2 Xylose 35.1±2.1 8.4 ±3.6 Mannose 33.5±2.1 8.2 ± 2.6 Xanthan 9.4 ±2.0 1.3 ±0.8 Site EPS 18.2±2.0 5.6±2.6 D. auto EPS 11.1±2.4 1.6±0.6 Desulfovibrio EPS 18.3±2.5 3.8±1.2 Schizothrix EPS 11.5±2.9 4.1±2.0 „Fossilized EPS‟ Example from the Silurian from Morocco Barbieri et al. 2004 Ingredients of lithification: 3. Chemical Communication? AHL O AIP O Phe Asp ile O R NH ile Cys Met S Asn O AI-2 HO OH -butyrolactones - B OH CH O O O 3 HO CH3 O CH3 O O HO O O O PQS OH C-HSL O NH N CH3 H HO Decho, Visscher and Norman 2010 Chemical Communication or Quorum Sensing Acylated Homoserine Lactone (C6) Acylated Homoserine Lactones from Cultures, Mats Sample Designation Major AHL detected Desulfovibrio ATCC 33405D C4, C8 vulgaris D. sp. strain H0407- GenBank C4, C6, C7, C8 12.1Lac DQ822785 t½ = 4.2h (pH 8.2); 0.5h (pH 9.6) D. sp. GenBank C4, C6, C7, C10, Strain H0407- DQ822786 C12 2.3jLac t½ = 22h (pH 8.2); 1.1h (pH 9.6) Natural mat - C4, C6, C7, C8, samples C10, C12, C14 t½ = 36h (pH 8.2); 11.4h (pH 9.6) Decho, Visscher et al. 2009 Words of warning: - Open (marine) systems vs. closed (lacustrine) ones (different models!) - Mats vs. microbialites - Rates matter (not species or genes) - Not only cyanobacteria – the entire community matters - Need to know plasticity of the community - Stressors? Light! Temperature, salinity, nutrients, “water quality”………. ORGANOMINERALIZATION .
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