Affiliation:
1. Soil and Water Science Department, University of Florida, Gainesville, Florida, USA
2. Department of Earth, Ocean, & Atmospheric Science, Florida State University, Tallahassee, Florida, USA
Abstract
ABSTRACT
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 SO
4
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 SO
4
2−
-rich areas of WCA-2A, while the
Methanosaetaceae
were dominant over the
Methanomicrobiales
in WCA-3A (with relatively low SO
4
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 MoO
4
2−
(a specific inhibitor of SRP activity) resulted in increased methane production rates, lower apparent fractionation factors [α
app
; defined as (amount of δ
13
CO
2
+ 1,000)/(amount of δ
13
CH
4
+ 1,000)], and higher
Methanosaetaceae
mcrA
transcript levels compared to those for the controls without MoO
4
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.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
23 articles.
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