Half of the microbial cells in the Earth's oceans are found in sediments. Many of these cells are members of the Archaea, single-celled prokaryotes in a domain of life separate from Bacteria and ...Eukaryota. However, most of these archaea lack cultured representatives, leaving their physiologies and placement on the tree of life uncertain. Here we show that the uncultured miscellaneous crenarchaeotal group (MCG) and marine benthic group-D (MBG-D) are among the most numerous archaea in the marine sub-sea floor. Single-cell genomic sequencing of one cell of MCG and three cells of MBG-D indicated that they form new branches basal to the archaeal phyla Thaumarchaeota and Aigarchaeota, for MCG, and the order Thermoplasmatales, for MBG-D. All four cells encoded extracellular protein-degrading enzymes such as gingipain and clostripain that are known to be effective in environments chemically similar to marine sediments. Furthermore, we found these two types of peptidase to be abundant and active in marine sediments, indicating that uncultured archaea may have a previously undiscovered role in protein remineralization in anoxic marine sediments.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Acetate is a key intermediate in anaerobic mineralization of organic matter in marine sediments. Its turnover is central to carbon cycling, however, the relative contribution of different microbial ...populations to acetate assimilation in marine sediments is unknown. To quantify acetate assimilation by
abundant bacterial populations, we incubated coastal marine sediments with
C-labeled acetate and flow-sorted cells that had been labeled and identified by fluorescence
hybridization. Subsequently, scintillography determined the amount of
C-acetate assimilated by distinct populations. This approach fostered a high-throughput quantification of acetate assimilation by phylogenetically identified populations. Acetate uptake was highest in the oxic-suboxic surface layer for all sorted bacterial populations, including deltaproteobacterial sulfate-reducing bacteria (SRB), which accounted for up to 32% of total bacterial acetate assimilation. We show that the family
also assimilates acetate in marine sediments, while the more abundant
dominated acetate assimilation despite lower uptake rates. Unexpectedly, members of
accounted for the highest relative acetate assimilation in all sediment layers with up to 31-62% of total bacterial acetate uptake. We also show that acetate is used to build up storage compounds such as polyalkanoates. Together, our findings demonstrate that not only the usual suspects SRB but a diverse bacterial community may substantially contribute to acetate assimilation in marine sediments. This study highlights the importance of quantitative approaches to reveal the roles of distinct microbial populations in acetate turnover.
Succession of redox processes is sometimes assumed to define a basic microbial community structure for ecosystems with oxygen gradients. In this paradigm, aerobic respiration, denitrification, ...fermentation and sulfate reduction proceed in a thermodynamically determined order, known as the 'redox tower'. Here, we investigated whether redox sorting of microbial processes explains microbial community structure at low-oxygen concentrations. We subjected a diverse microbial community sampled from a coastal marine sediment to 100 days of tidal cycling in a laboratory chemostat. Oxygen gradients (both in space and time) led to the assembly of a microbial community dominated by populations that each performed aerobic and anaerobic metabolism in parallel. This was shown by metagenomics, transcriptomics, proteomics and stable isotope incubations. Effective oxygen consumption combined with the formation of microaggregates sustained the activity of oxygen-sensitive anaerobic enzymes, leading to braiding of unsorted redox processes, within and between populations. Analyses of available metagenomic data sets indicated that the same ecological strategies might also be successful in some natural ecosystems.
In 1992, a handbook was published by the International Federation of Film Archives's Preservation Commission titled Characteristics of Early Films as Aids to Identification. Its author, Harold Brown, ...working since the 1950s for the National Film and Television Archive, had studied prints produced before 1914–15 by such companies as Gaumont, Pathé, Cinès, Vitagraph, and Selig. In his manual, he revealed their physical characteristics, which helped generations of archivists identify copies without titles and fragments that had somehow ended up in the collection. This handbook can be read today not only as a tool for identification but as a historical document. A study of the manual and its earlier edition from 1967 shows how the English curator developed practical ways to approach early cinema in the 1960s, when most archives considered short films from before World War I as “primitive.” His research turned these “primitives” into highly interesting historical objects. Through this, he opened the path to a reconsideration of the early years of cinema, leading finally to the legendary Brighton Congress in 1978. Harold Brown's publication can also be seen as a step toward a theory of film identification. This article looks at the theoretical side of his work, an approach based on Charles Sanders Peirce's concepts of abduction, deduction, and induction. Decades after the Brighton Congress, Brown's legacy still continues to inspire film archivists and cinema historians, as can be noted when looking at several projects from the recent past and today.
Roseobacter clade bacteria (RCB) are abundant in marine bacterioplankton worldwide and central to pelagic sulfur cycling. Very little is known about their abundance and function in marine sediments. ...We investigated the abundance, diversity and sulfur oxidation potential of RCB in surface sediments of two tidal flats. Here, RCB accounted for up to 9.6% of all cells and exceeded abundances commonly known for pelagic RCB by 1000-fold as revealed by fluorescence in situ hybridization (FISH). Phylogenetic analysis of 16S rRNA and sulfate thiohydrolase (SoxB) genes indicated diverse, possibly sulfur-oxidizing RCB related to sequences known from bacterioplankton and marine biofilms. To investigate the sulfur oxidation potential of RCB in sediments in more detail, we analyzed a metagenomic fragment from a RCB. This fragment encoded the reverse dissimilatory sulfite reductase (rDSR) pathway, which was not yet found in RCB, a novel type of sulfite dehydrogenase (SoeABC) and the Sox multi-enzyme complex including the SoxCD subunits. This was unexpected as soxCD and dsr genes were presumed to be mutually exclusive in sulfur-oxidizing prokaryotes. This unique gene arrangement would allow a metabolic flexibility beyond known sulfur-oxidizing pathways. We confirmed the presence of dsrA by geneFISH in closely related RCB from an enrichment culture. Our results show that RCB are an integral part of the microbial community in marine sediments, where they possibly oxidize inorganic and organic sulfur compounds in oxic and suboxic sediment layers.
Analog projection is increasingly endangered because strategies such as the Digital Cinema System Specification and Digital Cinema Package champion digital projection. Publicly funded institutions, ...however, like those in Western Europe whose core mission is still to preserve celluloid prints, must also provide access to them—necessitating the maintenance of analog projection facilities. This article—drawing on the case study of Cinémathèque de la Ville de Luxembourg—explores how modern film archives and cinémathèques can negotiate the current digital climate to keep their celluloid holdings relevant, functional, and accessible to the taxpaying public. Issues such as digitization, audience expectations, and print quality are discussed.
El surgimiento de la linterna mágica como herramienta para la educación en historia del arte durante la segunda mitad del siglo XIX se produce dentro del contexto más amplio de diferentes iniciativas ...para la reforma pedagógica que ponían el énfasis en la educación visual. Este estudio gira en torno a los requisitos de infraestructura previos para la divulgación a gran escala de las diapositivas de linterna mágicas de la época, que hacían posible introducir diapositivas sobre historia del arte en el aula como apoyo a la do-cencia. A continuación, se presenta el contexto general de los debates pedagógicos en el campo de la edu-cación sobre arte durante esa época en Alemania, que constituían la base de las iniciativas de reforma. En la última parte, el artículo se centra en el desarrollo práctico de las clases de historia del arte con imáge-nes proyectadas y en la forma en que transformó la relación entre el profesor, la obra de arte como obje-to de su discurso y los alumnos.
The phylogeny, abundance, and biogeography of the NOR5/OM60 clade was investigated. This clade includes “
Congregibacter litoralis” strain KT71, the first cultured representative of marine aerobic ...anoxygenic phototrophic
Gammaproteobacteria. More than 500 16S rRNA sequences affiliated with this clade were retrieved from public databases. By comparative sequence analysis, 13 subclades could be identified, some of which are currently restricted to discrete habitat types. Almost all sequences in the largest subclade NOR5-1 and related subclade NOR5-4 originated from marine surface water samples. Overall, most of the NOR5/OM60 sequences were retrieved from marine coastal settings, whereas there were fewer from open-ocean surface waters, deep-sea sediment, freshwater, saline lakes and soil.
The abundance of members of the NOR5/OM60 clade in various marine sites was determined by fluorescence
in situ hybridization using a newly designed and optimized probe set. Relative abundances in coastal marine waters off Namibia and the Yangtze estuary were up to 3% of the total 4′,6-diamidino-2-phenylindole (DAPI) counts, and in the German Bight off Helgoland the abundance was even up to 7%. In an open-ocean North Atlantic transect, between Iceland and the Azores, the NOR5/OM60 group was much less abundant (0.1–0.5%). Interestingly, the surface layer of North Sea intertidal sediments was very rich in NOR5/OM60, with absolute numbers >10
8
cells
cm
−3 (or 4% of the total DAPI). An analysis of the frequencies of NOR5/OM60 16S rRNA genes in the Global Ocean Survey datasets provided further support for a marine cosmopolitan occurrence of NOR5/OM60, and a clear preference for coastal marine waters.
Sandy coastal sediments are global hotspots for microbial mineralization of organic matter and denitrification. These sediments are characterized by advective porewater flow, tidal cycling and an ...active and complex microbial community. Metagenomic sequencing of microbial communities sampled from such sediments showed that potential sulfur oxidizing Gammaproteobacteria and members of the enigmatic BD1-5/SN-2 candidate phylum were abundant in situ (>10% and ~2% respectively). By mimicking the dynamic oxic/anoxic environmental conditions of the sediment in a laboratory chemostat, a simplified microbial community was selected from the more complex inoculum. Metagenomics, proteomics and fluorescence in situ hybridization showed that this simplified community contained both a potential sulfur oxidizing Gammaproteobacteria (at 24 ± 2% abundance) and a member of the BD1-5/SN-2 candidate phylum (at 7 ± 6% abundance). Despite the abundant supply of organic substrates to the chemostat, proteomic analysis suggested that the selected gammaproteobacterium grew partially autotrophically and performed hydrogen/formate oxidation. The enrichment of a member of the BD1-5/SN-2 candidate phylum enabled, for the first time, direct microscopic observation by fluorescent in situ hybridization and the experimental validation of the previously predicted translation of the stop codon UGA into glycine.
Between 1959 and 1962, the International Federation of Film Archives (FIAF) was divided by a serious internal conflict with long-lasting consequences. Some of the best known film archivists, such as ...Henri Langlois, Ernest Lindgren, and Jacques Ledoux, played a significant part in this, and so did FIAF president Jerzy Toeplitz. In this article, the conflict is reconstructed from the point of view of Marion Michelle, who was the secretary of FIAF and functioned as a catalyst in this affair, which accelerated a development inside FIAF that, in retrospect, appears to have been necessary to force a club of old friends to reform and become a professionally structured, worldwide association of film archives.
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