Anaerobic processes in activated sludge

We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H2S, O2, NO2− and NO3−. Denitrification and sulfate reduction rates were mmeasured with 15N- and 35S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport. Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. this indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.

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Symbiosis and competition among sulfate reduction, filamentous sulfur, denitrification, and poly-p accumulation bacteria in the anaerobic-oxic activated sludge of a municipal plant

Water Science & Technology ◽

10.2166/wst.1996.0543 ◽

1996 ◽

Vol 34 (5-6) ◽

pp. 119-128 ◽

Cited By ~ 10

Author(s):

Ryoko Yamamoto-Ikemoto ◽

Saburo Matsui ◽

Tomoaki Komori ◽

E. J. Bosque-Hamilton

Keyword(s):

Organic Acids ◽

Activated Sludge ◽

Sulfate Reduction ◽

Sulfide Oxidation ◽

Sulfate Reducing Bacteria ◽

Sulfur Cycle ◽

Sulfate Reducing ◽

P Accumulation ◽

Relationship Of ◽

Reducing Bacteria

Symbiosis and competition were examined among sulfate reducing bacteria (SRB), filamentous sulfur bacteria (FSB), denitrification bacteria (DNB) and poly-P accumulation bacteria (PAB) in the activated sludge of a municipal plant operated under anaerobic-oxic conditions. Batch experiments were carried out using settled sewage from the same plant as the substrate under several conditions. Under oxic conditions, both sulfate reduction and sulfide oxidation occurred simultaneously, making a symbiotic relationship of SRB and FSB for establishment of a sulfur cycle sustaining the energy requirements. Under anoxic conditions, denitrification was dominant because DNB outcompeted PAB and SRB for organic acids. Under anaerobic conditions, phosphate release and sulfate reduction occurred simultaneously. SRB produced for moles of acetate from four moles of propionate and/or unknown substances by reduction of three moles of sulfate. PAB competed with sulfate-reducing bacteria for organic acids such as propionate. However, PAB utilized acetate produced by SRB.

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On the Occurrence of Anoxic Microniches, Denitrification, and Sulfate Reduction in Aerated Activated Sludge

Applied and Environmental Microbiology ◽

10.1128/aem.65.9.4189-4196.1999 ◽

1999 ◽

Vol 65 (9) ◽

pp. 4189-4196 ◽

Cited By ~ 78

Author(s):

Andreas Schramm ◽

Cecilia M. Santegoeds ◽

Helle K. Nielsen ◽

Helle Ploug ◽

Michael Wagner ◽

...

Keyword(s):

Activated Sludge ◽

Sulfate Reduction ◽

Laser Scanning ◽

Three Dimensional ◽

Laser Scanning Microscopy ◽

Confocal Laser ◽

Sulfate Reducing ◽

Dissimilatory Sulfite Reductase ◽

Sulfate Reduction Rates ◽

Anoxic Zones

ABSTRACT A combination of different methods was applied to investigate the occurrence of anaerobic processes in aerated activated sludge. Microsensor measurements (O2, NO2 −, NO3 −, and H2S) were performed on single sludge flocs to detect anoxic niches, nitrate reduction, or sulfate reduction on a microscale. Incubations of activated sludge with15NO3 − and35SO4 2− were used to determine denitrification and sulfate reduction rates on a batch scale. In four of six investigated sludges, no anoxic zones developed during aeration, and consequently denitrification rates were very low. However, in two sludges anoxia in flocs coincided with significant denitrification rates. Sulfate reduction could not be detected in any sludge in either the microsensor or the batch investigation, not even under short-term anoxic conditions. In contrast, the presence of sulfate-reducing bacteria was shown by fluorescence in situ hybridization with 16S rRNA-targeted oligonucleotide probes and by PCR-based detection of genes coding for the dissimilatory sulfite reductase. A possible explanation for the absence of anoxia even in most of the larger flocs might be that oxygen transport is not only diffusional but enhanced by advection, i.e., facilitated by flow through pores and channels. This possibility is suggested by the irregularity of some oxygen profiles and by confocal laser scanning microscopy of the three-dimensional floc structures, which showed that flocs from the two sludges in which anoxic zones were found were apparently denser than flocs from the other sludges.

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Interactions between filamentous sulfur bacteria, sulfate reducing bacteria and poly-P accumulating bacteria in anaerobic-oxic activated sludge from a municipal plant

Water Science & Technology ◽

10.2166/wst.1998.0725 ◽

1998 ◽

Vol 37 (4-5) ◽

pp. 599-603 ◽

Cited By ~ 4

Author(s):

Ryoko Yamamoto-Ikemoto ◽

Saburo Matsui ◽

Tomoaki Komori ◽

Edja. Kofi. Bosque-Hamilton

Keyword(s):

Activated Sludge ◽

Sulfate Reduction ◽

Reduction Rate ◽

Sulfate Reducing Bacteria ◽

Sulfate Reduction Rate ◽

Filamentous Bulking ◽

Sulfate Reducing ◽

Sulfur Bacteria ◽

Sulfate Reduction Rates ◽

Reducing Bacteria

The interactions between filamentous sulfur bacteria (FSB), sulfate reducing bacteria (SRB) and poly-P accumulating bacteria (PAB) in the activated sludge of a municipal plant operated under anaerobic-oxic conditions were examined in batch experiments using return sludge (RAS) and settled sewage. Phosphate release and sulfate reduction occurred simultaneously under anaerobic conditions. SRB were more sensitive to temperature changes than PAB. SRB played an important role in the decomposition of propionate to acetate. When the sulfate reduction rates were high, there was a tendency for the maximum release of phosphate also to be high. This was explained by the fact that PAB utilized the acetate produced by SRB. Sulfur oxidizing bacteria were sensitive to temperature change. When the sulfate reduction rate was high, the sulfide oxidizing rate was also high and filamentous bulking occurred. The results showed that sulfate reduction was a cause of filamentous bulking due to Type 021N that could utilize reduced sulfur.

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Pseudodesulfovibrio cashew sp. Nov., a Novel Deep-Sea Sulfate-Reducing Bacterium, Linking Heavy Metal Resistance and Sulfur Cycle

Microorganisms ◽

10.3390/microorganisms9020429 ◽

2021 ◽

Vol 9 (2) ◽

pp. 429

Author(s):

Rikuan Zheng ◽

Shimei Wu ◽

Chaomin Sun

Keyword(s):

Heavy Metal ◽

Sulfate Reduction ◽

Marine Sediments ◽

Deep Sea ◽

Sulfur Cycle ◽

Metal Sulfides ◽

Phenotypic Traits ◽

Dissimilatory Sulfate Reduction ◽

Metabolic Potential ◽

Sulfate Reducing

Sulfur cycling is primarily driven by sulfate reduction mediated by sulfate-reducing bacteria (SRB) in marine sediments. The dissimilatory sulfate reduction drives the production of enormous quantities of reduced sulfide and thereby the formation of highly insoluble metal sulfides in marine sediments. Here, a novel sulfate-reducing bacterium designated Pseudodesulfovibrio cashew SRB007 was isolated and purified from the deep-sea cold seep and proposed to represent a novel species in the genus of Pseudodesulfovibrio. A detailed description of the phenotypic traits, phylogenetic status and central metabolisms of strain SRB007 allowed the reconstruction of the metabolic potential and lifestyle of a novel member of deep-sea SRB. Notably, P. cashew SRB007 showed a strong ability to resist and remove different heavy metal ions including Co2+, Ni2+, Cd2+ and Hg2+. The dissimilatory sulfate reduction was demonstrated to contribute to the prominent removal capability of P. cashew SRB007 against different heavy metals via the formation of insoluble metal sulfides.

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A deep-sea sulfate reducing bacterium directs the formation of zero-valent sulfur via sulfide oxidation

10.1101/2021.03.23.436689 ◽

2021 ◽

Author(s):

Rui Liu ◽

Yeqi Shan ◽

Shichuan Xi ◽

Xin Zhang ◽

Chaomin Sun

Keyword(s):

Deep Sea ◽

Sulfide Oxidation ◽

Sulfur Cycle ◽

Cold Seep ◽

Cold Seeps ◽

Protein Activity ◽

Quinone Oxidoreductase ◽

Sulfate Reducing ◽

Thiosulfate Reductase ◽

Reducing Bacteria

Zero-valent sulfur (ZVS) is a critical intermediate in the biogeochemical sulfur cycle. Up to date, sulfur oxidizing bacteria have been demonstrated to dominate the formation of ZVS. In contrast, formation of ZVS mediated by sulfate reducing bacteria (SRB) has been rarely reported. Here, we report for the first time that a typical sulfate reducing bacterium Desulfovibrio marinus CS1 directs the formation of ZVS via sulfide oxidation. In combination with proteomic analysis and protein activity assays, thiosulfate reductase (PhsA) and sulfide: quinone oxidoreductase (SQR) were demonstrated to play key roles in driving ZVS formation. In this process, PhsA catalyzed thiosulfate to form sulfide, which was then oxidized by SQR to form ZVS. Consistently, the expressions of PhsA and SQR were significantly up-regulated in strain CS1 when cultured in the deep-sea cold seep, strongly indicating strain CS1 might form ZVS in its real inhabiting niches. Notably, homologs of phsA and sqr widely distributed in the metagenomes of deep-sea SRB. Given the high abundance of SRB in cold seeps, it is reasonable to propose that SRB might greatly contribute to the formation of ZVS in the deep-sea environments. Our findings add a new aspect to the current understanding of the source of ZVS.

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Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments

Applied and Environmental Microbiology ◽

10.1128/aem.00949-19 ◽

2019 ◽

Vol 85 (14) ◽

Cited By ~ 13

Author(s):

J. Buongiorno ◽

L. C. Herbert ◽

L. M. Wehrmann ◽

A. B. Michaud ◽

K. Laufer ◽

...

Keyword(s):

Organic Matter ◽

Primary Production ◽

Sulfate Reduction ◽

The Arctic ◽

Sulfur Cycling ◽

Glacial Retreat ◽

Sulfate Reducing ◽

Glacial Runoff ◽

Sulfate Reduction Rates ◽

Fjord Sediments

ABSTRACTGlacial retreat is changing biogeochemical cycling in the Arctic, where glacial runoff contributes iron for oceanic shelf primary production. We hypothesize that in Svalbard fjords, microbes catalyze intense iron and sulfur cycling in low-organic-matter sediments. This is because low organic matter limits sulfide generation, allowing iron mobility to the water column instead of precipitation as iron monosulfides. In this study, we tested this with high-depth-resolution 16S rRNA gene libraries in the upper 20 cm at two sites in Van Keulenfjorden, Svalbard. At the site closer to the glaciers, iron-reducingDesulfuromonadales, iron-oxidizingGallionellaandMariprofundus, and sulfur-oxidizingThiotrichalesandEpsilonproteobacteriawere abundant above a 12-cm depth. Below this depth, the relative abundances of sequences for sulfate-reducingDesulfobacteraceaeandDesulfobulbaceaeincreased. At the outer station, the switch from iron-cycling clades to sulfate reducers occurred at shallower depths (∼5 cm), corresponding to higher sulfate reduction rates. Relatively labile organic matter (shown by δ13C and C/N ratios) was more abundant at this outer site, and ordination analysis suggested that this affected microbial community structure in surface sediments. Network analysis revealed more correlations between predicted iron- and sulfur-cycling taxa and with uncultured clades proximal to the glacier. Together, these results suggest that complex microbial communities catalyze redox cycling of iron and sulfur, especially closer to the glacier, where sulfate reduction is limited due to low availability of organic matter. Diminished sulfate reduction in upper sediments enables iron to flux into the overlying water, where it may be transported to the shelf.IMPORTANCEGlacial runoff is a key source of iron for primary production in the Arctic. In the fjords of the Svalbard archipelago, glacial retreat is predicted to stimulate phytoplankton blooms that were previously restricted to outer margins. Decreased sediment delivery and enhanced primary production have been hypothesized to alter sediment biogeochemistry, wherein any free reduced iron that could potentially be delivered to the shelf will instead become buried with sulfide generated through microbial sulfate reduction. We support this hypothesis with sequencing data that showed increases in the relative abundance of sulfate reducing taxa and sulfate reduction rates with increasing distance from the glaciers in Van Keulenfjorden, Svalbard. Community structure was driven by organic geochemistry, suggesting that enhanced input of organic material will stimulate sulfate reduction in interior fjord sediments as glaciers continue to recede.

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Sulfur Isotope Enrichment during Maintenance Metabolism in the Thermophilic Sulfate-Reducing Bacterium Desulfotomaculum putei

Applied and Environmental Microbiology ◽

10.1128/aem.02948-08 ◽

2009 ◽

Vol 75 (17) ◽

pp. 5621-5630 ◽

Cited By ~ 22

Author(s):

Mark M. Davidson ◽

M. E. Bisher ◽

Lisa M. Pratt ◽

Jon Fong ◽

Gordon Southam ◽

...

Keyword(s):

Sulfate Reduction ◽

Batch Culture ◽

Marine Sediments ◽

Maintenance Phase ◽

Laboratory Culture ◽

Specific Rate ◽

Culture Vessel ◽

Isotope Enrichment ◽

Sulfate Reducing ◽

Sulfate Reduction Rates

ABSTRACT Values of Δ34S ( \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({=}{\delta}^{34}S_{HS}{-}{\delta}^{34}S_{SO_{4}}\) \end{document} , where δ34SHS and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\delta}^{34}S_{SO_{4}}\) \end{document} indicate the differences in the isotopic compositions of the HS− and SO4 2− in the eluent, respectively) for many modern marine sediments are in the range of −55 to −75‰, much greater than the −2 to −46‰ ε34S (kinetic isotope enrichment) values commonly observed for microbial sulfate reduction in laboratory batch culture and chemostat experiments. It has been proposed that at extremely low sulfate reduction rates under hypersulfidic conditions with a nonlimited supply of sulfate, isotopic enrichment in laboratory culture experiments should increase to the levels recorded in nature. We examined the effect of extremely low sulfate reduction rates and electron donor limitation on S isotope fractionation by culturing a thermophilic, sulfate-reducing bacterium, Desulfotomaculum putei, in a biomass-recycling culture vessel, or “retentostat.” The cell-specific rate of sulfate reduction and the specific growth rate decreased progressively from the exponential phase to the maintenance phase, yielding average maintenance coefficients of 10−16 to 10−18 mol of SO4 cell−1 h−1 toward the end of the experiments. Overall S mass and isotopic balance were conserved during the experiment. The differences in the δ34S values of the sulfate and sulfide eluting from the retentostat were significantly larger, attaining a maximum Δ34S of −20.9‰, than the −9.7‰ observed during the batch culture experiment, but differences did not attain the values observed in marine sediments.

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Disguised as a Sulfate Reducer: Growth of the Deltaproteobacterium Desulfurivibrio alkaliphilus by Sulfide Oxidation with Nitrate

mBio ◽

10.1128/mbio.00671-17 ◽

2017 ◽

Vol 8 (4) ◽

Cited By ~ 48

Author(s):

Casper Thorup ◽

Andreas Schramm ◽

Alyssa J. Findlay ◽

Kai W. Finster ◽

Lars Schreiber

Keyword(s):

Sulfate Reduction ◽

Elemental Sulfur ◽

Sulfide Oxidation ◽

Model Organism ◽

Sulfur Cycle ◽

High Expression ◽

Sulfate Reducer ◽

Expression Of Genes ◽

Complex Picture ◽

Pure Cultures

ABSTRACT This study demonstrates that the deltaproteobacterium Desulfurivibrio alkaliphilus can grow chemolithotrophically by coupling sulfide oxidation to the dissimilatory reduction of nitrate and nitrite to ammonium. Key genes of known sulfide oxidation pathways are absent from the genome of D. alkaliphilus. Instead, the genome contains all of the genes necessary for sulfate reduction, including a gene for a reductive-type dissimilatory bisulfite reductase (DSR). Despite this, growth by sulfate reduction was not observed. Transcriptomic analysis revealed a very high expression level of sulfate-reduction genes during growth by sulfide oxidation, while inhibition experiments with molybdate pointed to elemental sulfur/polysulfides as intermediates. Consequently, we propose that D. alkaliphilus initially oxidizes sulfide to elemental sulfur, which is then either disproportionated, or oxidized by a reversal of the sulfate reduction pathway. This is the first study providing evidence that a reductive-type DSR is involved in a sulfide oxidation pathway. Transcriptome sequencing further suggests that nitrate reduction to ammonium is performed by a novel type of periplasmic nitrate reductase and an unusual membrane-anchored nitrite reductase. IMPORTANCE Sulfide oxidation and sulfate reduction, the two major branches of the sulfur cycle, are usually ascribed to distinct sets of microbes with distinct diagnostic genes. Here we show a more complex picture, as D. alkaliphilus, with the genomic setup of a sulfate reducer, grows by sulfide oxidation. The high expression of genes typically involved in the sulfate reduction pathway suggests that these genes, including the reductive-type dissimilatory bisulfite reductases, are also involved in as-yet-unresolved sulfide oxidation pathways. Finally, D. alkaliphilus is closely related to cable bacteria, which grow by electrogenic sulfide oxidation. Since there are no pure cultures of cable bacteria, D. alkaliphilus may represent an exciting model organism in which to study the physiology of this process. IMPORTANCE Sulfide oxidation and sulfate reduction, the two major branches of the sulfur cycle, are usually ascribed to distinct sets of microbes with distinct diagnostic genes. Here we show a more complex picture, as D. alkaliphilus, with the genomic setup of a sulfate reducer, grows by sulfide oxidation. The high expression of genes typically involved in the sulfate reduction pathway suggests that these genes, including the reductive-type dissimilatory bisulfite reductases, are also involved in as-yet-unresolved sulfide oxidation pathways. Finally, D. alkaliphilus is closely related to cable bacteria, which grow by electrogenic sulfide oxidation. Since there are no pure cultures of cable bacteria, D. alkaliphilus may represent an exciting model organism in which to study the physiology of this process.

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Diversity decoupled from sulfur isotope fractionation in a sulfate reducing microbial community

10.1101/518837 ◽

2019 ◽

Author(s):

Jesse Colangelo ◽

Claus Pelikan ◽

Craig W. Herbold ◽

Ianina Altshuler ◽

Alexander Loy ◽

...

Keyword(s):

Microbial Community ◽

Microbial Ecology ◽

Sulfate Reduction ◽

Isotope Fractionation ◽

Sulfur Isotopes ◽

List Type ◽

Natural Habitats ◽

Sulfate Reducing ◽

Sulfate Reduction Rates

AbstractThe extent of fractionation of sulfur isotopes by sulfate reducing microbes is dictated by genomic and environmental factors. A greater understanding of species-specific fractionations may better inform interpretation of sulfur isotopes preserved in the rock record. To examine whether gene diversity influences net isotopic fractionation in situ, we assessed environmental chemistry, sulfate reduction rates, diversity of putative sulfur metabolizing organisms by 16S rRNA and dissimilatory sulfite reductase (dsrB) gene amplicon sequencing, and net fractionation of sulfur isotopes along a sediment transect of a hypersaline Arctic spring. In situ sulfate reduction rates yielded minimum cell-specific sulfate reduction rates <0.3 x 10−15 moles cell−1 day−1. Neither 16S rRNA nor dsrB diversity indices correlated with relatively constant (38 to 45‰) net isotope fractionation (ε34Ssulfide−sulfate). Measured ε34S values could be reproduced in a mechanistic fractionation model if 1-2% of the microbial community (10-60% of Deltaproteobacteria) were engaged in sulfate respiration, indicating heterogeneous respiratory activity within sulfate-metabolizing populations. This model indicated enzymatic kinetic diversity of Apr was more likely to correlate with sulfur fractionation than DsrB. We propose that, above a threshold alpha diversity value, the influence of the specific composition of the microbial community responsible for generating an isotope signal is overprinted by the control exerted by environmental variables on microbial physiology.Subject categoriesIntegrated genomics and post-genomics approaches in microbial ecologyMicrobial ecology and functional diversity of natural habitats

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Stimulation of Dissimilatory Sulfate Reduction in Response to Sulfate in Microcosm Incubations from Two Contrasting Temperate Peatlands near Ithaca, NY, USA

FEMS Microbiology Letters ◽

10.1093/femsle/fnab153 ◽

2021 ◽

Author(s):

Andrew R St James ◽

Ruth E Richardson

Keyword(s):

Sulfate Reduction ◽

Electron Donor ◽

Short Chain Fatty Acids ◽

Sulfur Cycle ◽

Carbon Flow ◽

Dissimilatory Sulfate Reduction ◽

Metagenomic Sequencing ◽

Community Responses ◽

Sulfate Reducing ◽

Stimulation Of

Abstract Peatlands are responsible for over half of wetland methane emissions, yet major uncertainties remain regarding carbon flow, especially when increased availability of electron acceptors stimulate competing physiologies. We used microcosm incubations to study the effects of sulfate on microorganisms in two temperate peatlands, one bog and one fen. Three different electron donor treatments were used (13C-acetate, 13C-formate, and a mixture of 12C short-chain fatty acids) to elucidate the responses of sulfate-reducing bacteria (SRB) and methanogens to sulfate stimulation. Methane production was measured and metagenomic sequencing was performed, with only the heavy DNA fraction sequenced from treatments receiving 13C electron donors. Our data demonstrate stimulation of dissimilatory sulfate reduction in both sites, with contrasting community responses. In McLean Bog (MB), hydrogenotrophic Deltaproteobacteria and acetotrophic Peptococcaceae lineages of SRB were stimulated, as were lineages with unclassified dissimilatory sulfite reductases. In Michigan Hollow Fen (MHF), there was little stimulation of Peptococcaceae populations, and a small stimulation of Deltaproteobacteria SRB populations only in the presence of formate as electron donor. Sulfate stimulated an increase in relative abundance of reads for both oxidative and reductive sulfite reductases, suggesting stimulation of an internal sulfur cycle. Together, these data indicate a stimulation of SRB activity in response to sulfate in both sites, with a stronger growth response in MB than MHF. This study provides valuable insights into microbial community responses to sulfate in temperate peatlands and is an important first step to understanding how SRB and methanogens compete to regulate carbon flow in these systems.

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