Hydrogen metabolism in the hindgut of lower termites.

Die vorliegende Arbeit umfasst eine Reihe von Studien, die sich mit der quantitativen Analyse des Lignocelluloseabbaus im Enddarm von niederen Termiten beschäftigt. Das Hauptaugenmerk der Untersuchungen lag auf den Zwischenprodukten des Abbaus, im Besonderen auf Wasserstoff, sowie deren Umsatz und den dafür verantwortlichen Mikroorganismen. Die Termiten Reticulitermes santonensis, Zootermopsis nevadensis und Cryptotermes secundus, welche die drei artenreichsten Familien niederer Termiten repräsentieren, wurden als Modellorganismen verwendet. Untersuchungen zur intestinalen Wasserstoffkonzentration offenbarten extrem hohe Unterschiede in den verschieden Termitenarten, wobei in Z. nevadensis Wasserstoff in Mengen nahe dem Sättigungsbereich vorlag, während in C. secundus sich die Konzentration des Wasserstoffs nahe der Nachweisgrenze befand (<1 kPa). Trotz dieser unterschiedlichen Konzentrationen war Wasserstoff das wichtigste Zwischenprodukt des Lignocelluloseabbaus in den drei Termitenarten. Dabei betrug der Anteil des gesamten Elektronenflusses, der durch den Wasserstoffpool fließt, 22–26%. Die reduktive Acetogenese war der dominierende Wasserstoff-verbrauchende Prozess, während die hydrogenotrophe Methanogenese, die aerobe Wasserstoffoxidation sowie die Emission von Wasserstoff aus der Termite eine unwesentliche oder keine Rolle spielten. Eine Unterbestimmung der Methanogeneserate durch aerobe bzw. anaerobe Methanoxidation wurde experimentell ausgeschlossen. Weiterhin wurde Laktat als zweites wichtiges Zwischenprodukt in allen untersuchten Termiten identifiziert. Formiat stellte ebenfalls ein Zwischenprodukt dar. Allerdings war Formiat nur in C. secundus von Bedeutung, wo es durch die Formiat-abhängige reduktive Acetogenese umgesetzt wurde. Basierend auf diesen Kohlenstoff- und Elektronenflussmessungen wurden quantitative Modelle der Abbauprozesse im Enddarm der einzelnen Termitenarten postuliert. Die Identität und Diversität homoacetogener Bakterien im Enddarm wurde mit Hilfe des funktionellen Markergens fhs analysiert. Dieses Gen kodiert die Formyl-Tetrahydrofolat-Synthetase – ein Enzym des Acetyl-CoA-Weges. In allen untersuchten Termiten dominierten zahlenmässig fhs-Gene, die dem „Termiten-Treponemen-Cluster“ angehören. Weiterhin ergaben Expressionsanalysen, dass ausschließlich fhs-Gene des „Termiten-Treponemen-Cluster“ transkribiert wurden. Zusammenfassend deuten die Ergebnisse dieser Studie und die vorangegangene Kultivierung eines homoacetogenen Spirochäten aus dem Termitenenddarm stark darauf hin, dass Spirochäten der Gattung Treponema für die effiziente Wiederverwertung des Wasserstoffs durch die reduktive Acetogenese verantwortlich sind

The Active Sulfate-Reducing Microbial Community in Littoral Sediment of Oligotrophic Lake Constance

Active sulfate-reducing microorganisms (SRM) in freshwater sediments are under-examined, despite the well-documented cryptic sulfur cycle occurring in these low-sulfate habitats. In Lake Constance sediment, sulfate reduction rates of up to 1,800 nmol cm-3 day-1 were previously measured. To characterize its SRM community, we used a tripartite amplicon sequencing approach based on 16S rRNA genes, 16S rRNA, and dsrB transcripts (encoding the beta subunit of dissimilatory sulfite reductase). We followed the respective amplicon dynamics in four anoxic microcosm setups supplemented either with (i) chitin and sulfate, (ii) sulfate only, (iii) chitin only, or (iv) no amendment. Chitin was used as a general substrate for the whole carbon degradation chain. Sulfate turnover in sulfate-supplemented microcosms ranged from 38 to 955 nmol day-1 (g sediment f. wt.)-1 and was paralleled by a decrease of 90–100% in methanogenesis as compared to the respective methanogenic controls. In the initial sediment, relative abundances of recognized SRM lineages accounted for 3.1 and 4.4% of all bacterial 16S rRNA gene and 16S rRNA sequences, respectively. When normalized against the 1.4 × 108 total prokaryotic 16S rRNA gene copies as determined by qPCR and taking multiple rrn operons per genome into account, this resulted in approximately 105–106 SRM cells (g sediment f. wt.)-1. The three amplicon approaches jointly identified Desulfobacteraceae and Syntrophobacteraceae as the numerically dominant and transcriptionally most active SRM in the initial sediment. This was corroborated in the time course analyses of sulfate-consuming sediment microcosms irrespective of chitin amendment. Uncultured dsrAB family-level lineages constituted in sum only 1.9% of all dsrB transcripts, with uncultured lineage 5 and 6 being transcriptionally most active. Our study is the first holistic molecular approach to quantify and characterize active SRM including uncultured dsrAB lineages not only in Lake Constance but for lake sediments in general

Three manganese oxide-rich marine sediments harbor similar communities of acetate-oxidizing manganese-reducing bacteria

Dissimilatory manganese reduction dominates anaerobic carbon oxidation in marine sediments with high manganese oxide concentrations, but the microorganisms responsible for this process are largely unknown. In this study, the acetate-utilizing manganese-reducing microbiota in geographically well-separated, manganese oxide-rich sediments from Gullmar Fjord (Sweden), Skagerrak (Norway) and Ulleung Basin (Korea) were analyzed by 16S rRNA-stable isotope probing (SIP). Manganese reduction was the prevailing terminal electron-accepting process in anoxic incubations of surface sediments, and even the addition of acetate stimulated neither iron nor sulfate reduction. The three geographically distinct sediments harbored surprisingly similar communities of acetate-utilizing manganese-reducing bacteria: 16S rRNA of members of the genera Colwellia and Arcobacter and of novel genera within the Oceanospirillaceae and Alteromonadales were detected in heavy RNA-SIP fractions from these three sediments. Most probable number (MPN) analysis yielded up to 10(6) acetate-utilizing manganese-reducing cells cm(−3) in Gullmar Fjord sediment. A 16S rRNA gene clone library that was established from the highest MPN dilutions was dominated by sequences of Colwellia and Arcobacter species and members of the Oceanospirillaceae, supporting the obtained RNA-SIP results. In conclusion, these findings strongly suggest that (i) acetate-dependent manganese reduction in manganese oxide-rich sediments is catalyzed by members of taxa (Arcobacter, Colwellia and Oceanospirillaceae) previously not known to possess this physiological function, (ii) similar acetate-utilizing manganese reducers thrive in geographically distinct regions and (iii) the identified manganese reducers differ greatly from the extensively explored iron reducers in marine sediments

Sulfate-Reducing Microorganisms in Wetlands – Fameless Actors in Carbon Cycling and Climate Change

Freshwater wetlands are a major source of the greenhouse gas methane but at the same time can function as carbon sink. Their response to global warming and environmental pollution is one of the largest unknowns in the upcoming decades to centuries. In this review, we highlight the role of sulfate-reducing microorganisms (SRM) in the intertwined element cycles of wetlands. Although regarded primarily as methanogenic environments, biogeochemical studies have revealed a previously hidden sulfur cycle in wetlands that can sustain rapid renewal of the small standing pools of sulfate. Thus, dissimilatory sulfate reduction, which frequently occurs at rates comparable to marine surface sediments, can contribute up to 36–50% to anaerobic carbon mineralization in these ecosystems. Since sulfate reduction is thermodynamically favored relative to fermentative processes and methanogenesis, it effectively decreases gross methane production thereby mitigating the flux of methane to the atmosphere. However, very little is known about wetland SRM. Molecular analyses using dsrAB [encoding subunit A and B of the dissimilatory (bi)sulfite reductase] as marker genes demonstrated that members of novel phylogenetic lineages, which are unrelated to recognized SRM, dominate dsrAB richness and, if tested, are also abundant among the dsrAB-containing wetland microbiota. These discoveries point toward the existence of so far unknown SRM that are an important part of the autochthonous wetland microbiota. In addition to these numerically dominant microorganisms, a recent stable isotope probing study of SRM in a German peatland indicated that rare biosphere members might be highly active in situ and have a considerable stake in wetland sulfate reduction. The hidden sulfur cycle in wetlands and the fact that wetland SRM are not well represented by described SRM species explains their so far neglected role as important actors in carbon cycling and climate change

Postglacial adaptations enabled colonization and quasi-clonal dispersal of ammonia-oxidizing archaea in modern European large lakes

Ammonia-oxidizing archaea (AOA) play a key role in the aquatic nitrogen cycle. Their genetic diversity is viewed as the outcome of evolutionary processes that shaped ancestral transition from terrestrial to marine habitats. However, current genome-wide insights into AOA evolution rarely consider brackish and freshwater representatives or provide their divergence timeline in lacustrine systems. An unbiased global assessment of lacustrine AOA diversity is critical for understanding their origins, dispersal mechanisms, and ecosystem roles. Here, we leveraged continental-scale metagenomics to document that AOA species diversity in freshwater systems is remarkably low compared to marine environments. We show that the uncultured freshwater AOA, "Candidatus Nitrosopumilus limneticus," is ubiquitous and genotypically static in various large European lakes where it evolved 13 million years ago. We find that extensive proteome remodeling was a key innovation for freshwater colonization of AOA. These findings reveal the genetic diversity and adaptive mechanisms of a keystone species that has survived clonally in lakes for millennia

PILAR: Sharing VISIR Remote Labs Through a Federation

Social demands have promoted an educational approach based on an “anywhere and anytime” premise. Remote laboratories have emerged as the answer to the demands of technical educational areas for adapting themselves to this scenario. The result has not only benefit distance learning students but has provided new learning scenarios both for teachers and students as well as allowing a flexible approach to experimental topics. However, as any other solution for providing practical scenarios (hands-on labs, virtual labs or simulators), remote labs face several constraints inherited from the subsystems of its deployment -hardware (real instruments, equipment and scenario) and software (analog/digital conversions, communications, workbenches, etc.)-. This paper describes the Erasmus+ project Platform Integration of Laboratories based on the Architecture of visiR (PILAR) which deals with several units of the federation installed in different educational institutions and devoted to analog electronics and electrical circuits. Based on the limitations of remote labs, the need for the federation will be justified and its benefits will be described.The authors acknowledge the support of the Escuela de Doctorado de la UNED, the S2013/ICE-2715 - eMadrid project, VISIR+ project Erasmus+ Capacity Building in Higher Education 2015 nº 561735-EPP-1-2015-1-PT-EPPKA2-CBHE-JP and PILAR project Erasmus+ Strategic Partnership nº 2016-1-ES01-KA203-025327 (Platform Integration of Laboratories based on the Architecture of visiR). As well as to the Education Innovation Project (PIE) of UNED, “Desarrollos Avanzados Multi-Objetivo de Laboratorios Remotos para Actividades Educativas – DAMO-LRAE”, from the Vicerrectorado de Ordenación Académica y Calidad and the Instituto Universitario de Educación a Distancia (IUED) of the UNED and to the project 2018-IEQ18 from the Escuela Superior de Ingenieros Industriales of UNED.info:eu-repo/semantics/publishedVersio

Peatland <i>Acidobacteria </i>with a dissimilatory sulfur metabolism

Sulfur-cycling microorganisms impact organic matter decomposition in wetlands and consequently greenhouse gas emissions from these globally relevant environments. However, their identities and physiological properties are largely unknown. By applying a functional metagenomics approach to an acidic peatland, we recovered draft genomes of seven novel Acidobacteria species with the potential for dissimilatory sulfite (dsrAB, dsrC, dsrD, dsrN, dsrT, dsrMKJOP) or sulfate respiration (sat, aprBA, qmoABC plus dsr genes). Surprisingly, the genomes also encoded DsrL, which so far was only found in sulfur-oxidizing microorganisms. Metatranscriptome analysis demonstrated expression of acidobacterial sulfur-metabolism genes in native peat soil and their upregulation in diverse anoxic microcosms. This indicated an active sulfate respiration pathway, which, however, might also operate in reverse for dissimilatory sulfur oxidation or disproportionation as proposed for the sulfur-oxidizing Desulfurivibrio alkaliphilus. Acidobacteria that only harbored genes for sulfite reduction additionally encoded enzymes that liberate sulfite from organosulfonates, which suggested organic sulfur compounds as complementary energy sources. Further metabolic potentials included polysaccharide hydrolysis and sugar utilization, aerobic respiration, several fermentative capabilities, and hydrogen oxidation. Our findings extend both, the known physiological and genetic properties of Acidobacteria and the known taxonomic diversity of microorganisms with a DsrAB-based sulfur metabolism, and highlight new fundamental niches for facultative anaerobic Acidobacteria in wetlands based on exploitation of inorganic and organic sulfur molecules for energy conservation

PILAR: a Federation of VISIR Remote Laboratory Systems for Educational Open Activities

Social demands have promoted an educational approach based on an “anywhere and anytime” premise. Remote laboratories have emerged as the answer to the demands of technical educational areas for adapting themselves to this scenario. The result has not only benefit distance learning students but has provided new learning scenarios both for teachers and students as well as allowing a flexible approach to experimental topics. However, as any other solution for providing practical scenarios (hands-on labs, virtual labs or simulators), remote labs face several constraints inherited from the subsystems of its deployment hardware (real instruments, equipment and scenario) and software (analog/digital conversions, communications, workbenches, etc.). This paper describes the Erasmus+ project Platform Integration of Laboratories based on the Architecture of visiR (PILAR) which deals with several units of the federation installed in different educational institutions and devoted to analog electronics and electrical circuits. Based on the limitations of remote labs, the need for the federation will be justified and its benefits will be described by taking advantage of its strengths. The challenges that have come up during the different stages and the different approaches to design are also going to be described and analyzedinfo:eu-repo/semantics/publishedVersio