Sediment Microbial Community Structure and Mercury Methylation in Mercury-Polluted Clear Lake, California

Macalady, Jennifer L.; Mack, E. Erin; Nelson, Douglas C.; Scow, Kate M.

doi:10.1128/aem.66.4.1479-1488.2000

Cited by 143 publications

(82 citation statements)

References 47 publications

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“…Archaea lack ester-linked fatty acids in their membrane and are therefore undetectable in PLFA analysis. However 10Me16 : 0 and C17 MUFA are known to be especially abundant in sulphate-reducing bacteria (Macalady et al, 2000;Boschker and Middelburg, 2002), one of the syntrophic partner of anaerobic CH 4 oxidizing archaea (Knittel and Boetius, 2009). Hence, the specific labelling of 10Me16:0 and C17 MUFA in O 2 -depleted waters could indicates that a fraction of the upward flux of CH 4 was oxidized syntrophically by an archaea/bacteria consortium, and might support the hypothesis that the bacterial partner grow on CH 4 -derived carbon source supplied by anaerobic methane oxidizers within the consortium, as already suggested by the results of an in vitro labelling ( 13 CH 4 ) study (Blumenberg et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

Methanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

Morana

Borges²,

Roland³

et al. 2015

Biogeosciences

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Abstract. The permanently stratified Lake Kivu is one of the largest freshwater reservoirs of dissolved methane (CH 4 ) on Earth. Yet CH 4 emissions from its surface to the atmosphere have been estimated to be 2 orders of magnitude lower than the CH 4 upward flux to the mixed layer, suggesting that microbial CH 4 oxidation is an important process within the water column. A combination of natural abundance stable carbon isotope analysis (δ 13 C) of several carbon pools and 13 CH 4 -labelling experiments was carried out during the rainy and dry season to quantify (i) the contribution of CH 4 -derived carbon to the biomass, (ii) methanotrophic bacterial production (MBP), and (iii) methanotrophic bacterial growth efficiency (MBGE), defined as the ratio between MBP and gross CH 4 oxidation. We also investigated the distribution and the δ 13 C of specific phospholipid fatty acids (PLFAs), used as biomarkers for aerobic methanotrophs. Maximal MBP rates were measured in the oxycline, suggesting that CH 4 oxidation was mainly driven by oxic processes. Moreover, our data revealed that methanotrophic organisms in the water column oxidized most of the upward flux of CH 4 , and that a significant amount of CH 4 -derived carbon was incorporated into the microbial biomass in the oxycline. The MBGE was variable (2-50 %) and negatively related to CH 4 : O 2 molar ratios. Thus, a comparatively smaller fraction of CH 4 -derived carbon was incorporated into the cellular biomass in deeper waters, at the bottom of the oxycline where oxygen was scarce. The aerobic methanotrophic community was clearly dominated by type I methanotrophs and no evidence was found for an active involvement of type II methanotrophs in CH 4 oxidation in Lake Kivu, based on fatty acids analyses. Vertically integrated over the water column, the MBP was equivalent to 16-60 % of the average phytoplankton particulate primary production. This relatively high magnitude of MBP, and the substantial contribution of CH 4 -derived carbon to the overall biomass in the oxycline, suggest that methanotrophic bacteria could potentially sustain a significant fraction of the pelagic food web in the deep, meromictic Lake Kivu.

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Section: Discussionmentioning

confidence: 99%

Methanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

Morana

Borges²,

Roland³

et al. 2015

Biogeosciences

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“…and between sulfate reduction rate and Hg methylation rate (31)(32)(33)(34). The primary site of methylation is just below the oxic/anoxic interface, which is often near the sediment surface in aquatic systems (9,16,(35)(36)(37).…”

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confidence: 99%

Geochemical and Biological Controls over Methylmercury Production and Degradation in Aquatic Ecosystems

Benoit

Gilmour²,

Heyes

et al. 2002

ACS Symposium Series

368

434

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It is the goal of this paper to discuss the more salient recent AdvancCll in the understanding of the controls of net CH3Hg formation in Datural systems. The discussion lIighlights the gaps in knowledge and the areas where progress in understanding has occurred. In particular, this chapter focuses on recent developments in Hg bioavailability and uptake by methylating bacteria, on the competing roles of sulfate and sulfide in the control of methylation, and in pathways for demethylation. The role of sulfide in influencing methylation is discussed in detail. In addition, the impact of other environmental variables such as pH, dissolved organic carbon and temperature on mercury methylation are discussed.Lastly, we provide a synthesis of the variability in the methylation response to Hg inputs across ecosystems. We suggest that although methylation is a function of Hg concentratioD, the range of methylation rates across ecosystems is larger than the range in Hg deposition rates. Overall, we conclude that factors in addition to the amount Hg deposition playa large role in controlling CH3Hg production and bioaccumulation in aquatic ecosystems. 262to

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“…The SRB biomarkers used in this study targeted Desulfobacter, Desulfobulbus and Desulfovibrio, all are GN SRB grouped in the d-Proteobacteria (Macalady et al, 2000;Rabus et al, 2006). Despite their grouping, these genera differ in their metabolic versatility when it comes to carbon substrates.…”

Section: Discussionmentioning

confidence: 99%

Effects of ciprofloxacin on salt marsh sediment microbial communities

2007

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Fluoroquinolones, a widely used class of antibiotics, are frequently detected in sediments and surface waters. Given their antimicrobial properties, the presence of these compounds may alter the composition of microbial communities and promote antibiotic resistance in the environment. The purpose of this study was to measure sorption, and effects of ciprofloxacin on microbial community composition, in sediment samples from three California salt marshes. Sediments were exposed to a ciprofloxacin concentration gradient (0-200 lg ml À1 ciprofloxacin) and microbial community composition characterized using phospholipid fatty acid (PLFA) analysis. Sorption coefficients, expressed as log K d , were calculated from fits using the Freundlich isotherm model. Ciprofloxacin strongly sorbed to all sediments and had log K d values, ranging from 2.9 to 4.3. Clay content was positively (r 2 ¼ 0.98) and pH negatively (r 2 ¼ 0.99) correlated to K d values. Biomass, PLFA richness, sulfate reducer and Gram-negative bacteria markers increased with ciprofloxacin concentrations, while the 17 cy/precursor and saturated/unsaturated biomarker ratios, indicators of starvation stress, decreased. The magnitude of the effect of ciprofloxacin on microbial communities was inversely correlated to the degree of sorption to the sediments. Despite the fact that ciprofloxacin is a wide-spectrum antibiotic, its impact on sediment microbial communities was selective and appeared to favor sulfate-reducing bacteria and Gram-negative bacteria.

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Sediment Microbial Community Structure and Mercury Methylation in Mercury-Polluted Clear Lake, California

Cited by 143 publications

References 47 publications

Methanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

Methanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

Geochemical and Biological Controls over Methylmercury Production and Degradation in Aquatic Ecosystems

Effects of ciprofloxacin on salt marsh sediment microbial communities

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