Estudi de la biocenosi dels tapissos microbians del delta de l?Ebre

S'estudià la microzonació de la comunitat de microorganismes que composa els tapissos microbians del delta de l'Ebre mitjançant tècniques de microcòpia òptica i de microscòpia electrònica. Els tapissos microbians estudiats presentaven característiques diferents (nombre de laminacions, composició d'espècies, etc.). La laminació superior estava formada per diversos organismes fotosintètics oxigènics on dominaven les diatomees pinnades, arribant a densitats de 7,3·107 cel·cm?3. S'identificaren 12 gèneres, dels quals els més abundants foren Nitzschia, Navicula, Amphora i Mastogloia. En la laminació superficial també s'hi podien observar cianobacteris, tant filamentosos com cocoides dels quals Lyngbya aestuarii és un dels cianobacteris filamentosos més abundants que s'hi va trobar. A la segona laminació el microorganisme dominant era el cianobacteri Microcoleus chthonoplastes, que podia presentar entre 5 i més de 20 tricomes per beina. La tercera laminació pigmentada no la presentaven tots els tapissos microbians estudiats, i en els que s'observà podia variar l'espècie de microorganisme dominant. Així, el microorganisme més abundant d'aquesta laminació, en el punt de mostreig P1, era el bacteri fototròfic anoxigènic Chromatium gracile. En canvi, en el P3 el microorganisme predominant fou una nova espècie de la família Chromatiaceae, de 4,16 µm d'ample per 5,98 µm de longitud, que acumulava sofre intracel·lular i tenia el sistema intracitoplasmàtic de membranes de tipus lamel·lar. També s'hi observà la presència d'un microorganisme fototròfic filamentós embeinat, que tenia un sistema intracitoplasmàtic de membranes (ICM) de tipus lamel·lar. En la zona superior de la laminació rosa, es va observar la presència del bacteri quimiolitotròfic Beggiatoa sp i al davall de la zona fòtica, on el sediment era de color negre es van detectar bacteris reductors de sulfat dels gèneres Desulfovibrio, Desulfococcus i Desulfotomaculum.Se estudió la microzonación de la comunidad de microorganismos que forman los tapetes microbianos del delta del Ebro mediante técnicas de microscopía óptica y electrónica. Los tapetes microbianos estudiados presentaban características distintas (número de capas, composición de especies, etc.). La laminación superior estaba formada por diversos organismos fotosintéticos oxigénicos donde dominaban las diatomeas pennadas, llegando a densidades de 7,3·107 cel·cm?3. Se identificaron 12 géneros, entre los más abundantes estaban Nitzschia, Navicula, Amphora y Mastogloia. En la primera capa también se observaron cianobacterias, tanto filamentosas como cocoides, siendo Lyngbya aestuarii una de las cianobacterias filamentosas más abundantes que se detectaron. En la segunda laminación el microorganismo dominante era Microcoleus chthonoplastes, que podía presentar entre 5 y más de 20 tricomas por vaina. La tercera laminación pigmentada no la presentaban todos los tapetes estudiados, y en aquellos en los que se observó podía variar la especie de microorganismo dominante. La especie más abundante en esa laminación, en el punto de muestreo P1, era la bacteria fototrófica anoxigénica Chromatium gracile. Sin embargo, en el P3 el microorganismo predominante era una nueva especie de la familia Chromatiaceae, de 4,16 µm de diámetro por 5,98 µm de longitud, que acumulaba azufre intracelular y el sistema intracitoplasmático de membranas (ICM) era de tipo lamelar. También se observó la presencia de un microorganismo fototrófico filamentoso envainado, con un sistema ICM lamelar. En la zona superior de la laminación rosa, se observó la presencia de la bacteria quimiolitotrófica Beggiatoa sp. y por debajo de la zona fótica, donde el sedimento era de color negro se detectaron bacterias reductoras de sulfato pertenecientes a los géneros Desulfovibrio, Desulfococcus y Desulfotomaculum.The microzonation of microorganisms in the microbial mats of the Ebro Delta was studied by light microscopy andscanning and transmission electron microscopy. Microbial mats showed differences in species composition, number and colour of layers, etc. Oxygenic photosynthetic organisms grew on the surface of the mat. In this layer, the community consisted predominantly of pennate diatoms, reaching densities of 7.3·107 cel·cm?3. Twelve genera of diatoms were identified, and the most abundant were Nitzschia, Navicula, Amphora and Mastogloia. Coccoid cyanobacteria and filamentous cyanobacteria were also identified in the upper layer of the mat, where the predominant filamentous cyanobacterium was Lyngbya aestuarii. The dominant microorganism in the second layer was the filamentous cyanobacterium Microcoleus chthono plastes, which contained 5-20 trichomes within the common sheath. The third layer was not present in all the microbial mats studied, and when it was present the dominant species could be different in different sampling sites. In sampling site P1 the dominant microorganism was the anoxygenic phototrophic bacterium Chromatium gracile. But in site P3 the dominant microorganism in the purple third layer was a new species belonging to the Chromatiaceae (4,16 µm in diameter and 5,98 µm in length; the intracytoplasmic membrane system (ICM) was lamellar; and in the presence of sulphide and light, globules of sulphur are formed inside these cells). Another sheathed filamentous phototrophic microorganism with a lamellar ICM was also observed in this layer. Between the Microcoleus layer and the purple layer, the chemolithotrophic bacterium Beggiatoa sp. was found. Below the photic zone, in the black sediment, sulphate reducing bacteria belonging to the genera Desulfovibrio, Desulfococcus and Desulfotomaculum were identified

Hamiltonian facets of classical gauge theories on E-manifolds

Manifolds with boundary, with corners, b-manifolds and foliations model configuration spaces for particles moving under constraints and can be described as E-manifolds. E-manifolds were introduced in [NT01] and investigated in depth in [MS20]. In this article we explore their physical facets by extending gauge theories to the E-category. Singularities in the configuration space of a classical particle can be described in several new scenarios unveiling their Hamiltonian aspects on an E-symplectic manifold. Following the scheme inaugurated in [Wei78], we show the existence of a universal model for a particle interacting with an E-gauge field. In addition, we generalize the description of phase spaces in Yang-Mills theory as Poisson manifolds and their minimal coupling procedure, as shown in [Mon86], for base manifolds endowed with an E-structure. In particular, the reduction at coadjoint orbits and the shifting trick are extended to this framework. We show that Wong's equations, which describe the interaction of a particle with a Yang-Mills field, become Hamiltonian in the E-setting. We formulate the electromagnetic gauge in a Minkowski space relating it to the proper time foliation and we see that our main theorem describes the minimal coupling in physical models such as the compactified black hole.Preprin

Biodiversity for biocatalysis: A review of the α/β-hydrolase fold superfamily of esterases-lipases discovered in metagenomes

Review Article.Natural biodiversity undoubtedly inspires biocatalysis research and innovation. Biotransformations of interest also inspire the search for appropriate biocatalysts in nature. Indeed, natural genetic resources have been found to support the hydrolysis and synthesis of not only common but also unusual synthetic scaffolds. The emerging tool of metagenomics has the advantage of allowing straightforward identification of activity directly applicable as biocatalysis. However, new enzymes must not only have outstanding properties in terms of performance but also other properties superior to those of well-established commercial preparations in order to successfully replace the latter. Esterases (EST) and lipases (LIP) from the α/β-hydrolase fold superfamily are among the enzymes primarily used in biocatalysis. Accordingly, they have been extensively examined with metagenomics. Here we provided an updated (October 2015) overview of sequence and functional data sets of 288 EST–LIP enzymes with validated functions that have been isolated in metagenomes and (mostly partially) characterized. Through sequence, biochemical, and reactivity analyses, we attempted to understand the phenomenon of variability and versatility within this group of enzymes and to implement this knowledge to identify sequences encoding EST–LIP which may be useful for biocatalysis. We found that the diversity of described EST–LIP polypeptides was not dominated by a particular type of protein or highly similar clusters of proteins but rather by diverse nonredundant sequences. Purified EST–LIP exhibited a wide temperature activity range of 10–85 °C, although a preferred bias for a mesophilic temperature range (35–40 °C) was observed. At least 60% of the total characterized metagenomics-derived EST–LIP showed outstanding properties in terms of stability (solvent tolerance) and reactivity (selectivity and substrate profile), which are the features of interest in biocatalysis. We hope that, in the future, the search for and utilization of sequences similar to those already encoded and characterized EST–LIP enzymes from metagenomes may be of interest for promoting unresolved biotransformations in the chemical industry. Some examples are discussed in this review.The authors gratefully acknowledge the financial support provided by the European Community project MAMBA (FP7-KBBE-2008-226977), MAGIC-PAH (FP7-KBBE-2009-245226), ULIXES (FP7-KBBE-2010-266473), MicroB3 (FP7-OCEAN.2011-2-287589), KILL-SPILL (FP7-KBBE-2012-312139) and Royal Society UK-Russia Exchange Grant (IE130218). We thank EU Horizon 2020 Program for the support of the Project INMARE H2020-BG-2014-2634486. This work was further funded by grants BIO2011-25012,PCIN-2014-107 and BIO2014-54494-R from the Spanish Ministry of Economy and Competitiveness. The present investigation was funded by the Spanish Ministry of Economy and Competitiveness, the UK Biotechnology and Biological Sciences Research Council (BBSRC) and the German Federal Ministry of Education and Research (BMBF) within the ERA NET-IB2 program, grant number ERA-IB-14-030. The authors gratefully acknowledge the financial support provided by the European Regional Development Fund (ERDF).Peer reviewe

Sulfide fluxes in a microbial mat from the Ebro Delta, Spain

The sulfur cycle of Ebro Delta microbial mats was studied in order to determine sulfide production and sulfide consumption. Vertical distribution of two major functional groups involved in the sulfur cycle, anoxygenic phototrophic bacteria and dissimilatory sulfate-reducing bacteria (SRB), was also studied. The former reached up to 2.2 ×108 cfu cm-3 sediment in the purple layer, and the latter reached about 1.8×105 SRB cm-3 sediment in the black layer. From the changes in sulfide concentrations under light-dark cycles it can be inferred that the rate of H2S production was 6.2 μmol H2S cm-3 day-1 at 2.6 mm, and 7.6 μmol H2S cm-3 day-1 at 6 mm. Furthermore, sulfide consumption was also assessed, determining rates of 0.04, 0.13 and 0.005 mmol l-1 of sulfide oxidized at depths of 2.6, 3 and 6 mm, respectively

Cell Wall Composition and Structure Define the Developmental Fate of Embryogenic Microspores in Brassica napus

[EN] Microspore cultures generate a heterogeneous population of embryogenic structures that can be grouped into highly embryogenic structures [exine-enclosed (EE) and loose bicellular structures (LBS)] and barely embryogenic structures [compact callus (CC) and loose callus (LC) structures]. Little is known about the factors behind these different responses. In this study we performed a comparative analysis of the composition and architecture of the cell walls of each structure by confocal and quantitative electron microscopy. Each structure presented specific cell wall characteristics that defined their developmental fate. EE and LBS structures, which are responsible for most of the viable embryos, showed a specific profile with thin walls rich in arabinogalactan proteins (AGPs), highly and low methyl-esterified pectin and callose, and a callose-rich subintinal layer not necessarily thick, but with a remarkably high callose concentration. The different profiles of EE and LBS walls support the development as suspensorless and suspensor-bearing embryos, respectively. Conversely, less viable embryogenic structures (LC) presented the thickest walls and the lowest values for almost all of the studied cell wall components. These cell wall properties would be the less favorable for cell proliferation and embryo progression. High levels of highly methyl-esterified pectin are necessary for wall flexibility and growth of highly embryogenic structures. AGPs seem to play a role in cell wall stiffness, possibly due to their putative role as calcium capacitors, explaining the positive relationship between embryogenic potential and calcium levels.This work was supported by grant PID2020-115763RBI00 to JS-S from Spanish MICINN and by a Juan de la Cierva -Incorporacion Fellowship and a Marie Sklodowska-Curie Individual Fellowship (656579) to PC-M. RM holds a CDEIGENT (2018/023) fellowship from Generalitat Valenciana.Camacho-Fernández, C.; Seguí-Simarro, JM.; Mir Moreno, R.; Boutilier, K.; Corral-Martínez, P. (2021). Cell Wall Composition and Structure Define the Developmental Fate of Embryogenic Microspores in Brassica napus. Frontiers in Plant Science. 12:1-16. https://doi.org/10.3389/fpls.2021.7371391161

Distribution of phototrophic populations and primary production in a microbial mat from the Ebro Delta, Spain

Microbial mats arising in the sand flats of the Ebro Delta (Tarragona, Spain) were investigated during the summer season, when the community was highly developed. These mats are composed of three pigmented layers of phototrophic organisms, an upper brown layer mainly composed of Lyngbya aestuarii and diatoms, an intermediate green layer of the cyanobacterium Microcoleus chthonoplastes, and an underlying pink layer of a so-far unidentified purple sulfur bacterium. In the photic zone, oxygenic phototrophs constitute about 58% of total photosynthetic biomass, measured as biovolume, and anoxygenic phototrophs represent 42%. Diatoms constitute 11.8% of the oxygenic biomass, M. chthonoplastes 61.2%, and L. aestuarii and coccoid cyanobacteria 20.6 and 6.4%, respectively. In this laminated community, organic matter has an autochthonous origin, and photosynthesis is the most important source of organic carbon. Oxygen production reaches up to 27.2 mmol O2 m–2 h–1, measured at 1000 μE m–2 s–1 light intensity, whereas oxidation of sulfide in the light has been calculated to be 18.6 mmol S m–2 h–1. This amount represents 26% of the total photosynthetic production in terms of photoassimilated carbon, demonstrating the important role of anoxygenic phototrophs as primary producers in the pink layer of Ebro Delta microbial mats. [Int Microbiol 2004; 7(1):19–25