Distribution, activities, and interactions of methanogens and sulfate-reducing prokaryotes in the Florida Everglades.
To gain insight into the mechanisms controlling methanogenic pathways in the Florida Everglades, the distribution and functional activities of methanogens and sulfate-reducing prokaryotes (SRPs) were investigated in soils (0 to 2 or 0 to 4 cm depth) across the well-documented nutrient gradient in the water conservation areas (WCAs) caused by runoff from the adjacent Everglades Agricultural Area. The methyl coenzyme M reductase gene (mcrA) sequences that were retrieved from WCA-2A, an area with relatively high concentrations of SO4 (2-) (≥39 μM), indicated that methanogens inhabiting this area were broadly distributed within the orders Methanomicrobiales, Methanosarcinales, Methanocellales, Methanobacteriales, and Methanomassiliicoccales. In more than 3 years of monitoring, quantitative PCR (qPCR) using newly designed group-specific primers revealed that the hydrogenotrophic Methanomicrobiales were more numerous than the Methanosaetaceae obligatory acetotrophs in SO4 (2-)-rich areas of WCA-2A, while the Methanosaetaceae were dominant over the Methanomicrobiales in WCA-3A (with relatively low SO4 (2-) concentrations; ≤4 μM). qPCR of dsrB sequences also indicated that SRPs are present at greater numbers than methanogens in the WCAs. In an incubation study with WCA-2A soils, addition of MoO4 (2-) (a specific inhibitor of SRP activity) resulted in increased methane production rates, lower apparent fractionation factors [αapp; defined as (amount of δ(13)CO2 + 1,000)/(amount of δ(13)CH4 + 1,000)], and higher Methanosaetaceae mcrA transcript levels compared to those for the controls without MoO4 (2-). These results indicate that SRPs play crucial roles in controlling methanogenic pathways and in shaping the structures of methanogen assemblages as a function of position along the nutrient gradient.
Soil and Water Science Department, University of Florida, Gainesville, Florida, USA.
Hee-Sung
HS
Bae
Department of Earth, Ocean, & Atmospheric Science, Florida State University, Tallahassee, Florida, USA.
M Elizabeth
ME
Holmes
Department of Earth, Ocean, & Atmospheric Science, Florida State University, Tallahassee, Florida, USA.
Jeffrey P
JP
Chanton
Soil and Water Science Department, University of Florida, Gainesville, Florida, USA.
K Ramesh
KR
Reddy
Soil and Water Science Department, University of Florida, Gainesville, Florida, USA aogram@ufl.edu.
Andrew
A
Ogram
D058448:Biota; D017931:DNA Primers / Q000235:genetics; D005431:Florida; D008697:Methane / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000235:genetics; D011387:Prokaryotic Cells / Q000145:classification* / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013431:Sulfates / Q000378:metabolism*
D017931:DNA Primers; D013431:Sulfates; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; C021572:methyl coenzyme M reductase; D008697:Methane