The extremo-α-carbonic anhydrase (CA) from Sulfurihydrogenibium azorense,the fastest CA known,is highly activated by amino acids and amines

The α-carbonic anhydrase (CA, EC 4.2.1.1) from the extremophilic bacterium Sulfurihydrogenibium azorense (SazCA) was recently shown to be the fastest CA known. Here we investigated this enzyme for its activation with a series of amino acids and amines. The best SazCA activators were d-Phe, l-DOPA, l- and d-Trp, dopamine and serotonin, which showed activation constants in the range of 3–23 nM. l- and d-His, l-Phe, l-Tyr, 2-pyridyl-methylamine and L-adrenaline were also effective activators (K_As in the range of 62–90 nM), whereas d-Dopa, d-Tyr and several heterocyclic amines showed activity in the micromolar range. The good thermal stability, robustness, very high catalytic activity and propensity to be activated by simple amino acids and amines, make SazCA a very interesting candidate for biomimetic CO₂ capture processes.     

A highly catalytically active γ-carbonic anhydrase from the pathogenic anaerobe Porphyromonas gingivalis and its inhibition profile with anions and small molecules

Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the γ-class are present in archaea, bacteria and plants but, except the Methanosarcina thermophila enzymes CAM and CAMH, they were poorly characterized so far. Here we report a new such enzyme (PgiCA), the γ-CA from the oral cavity pathogenic bacterium Porphyromonas gingivalis, the main causative agent of periodontitis. PgiCA showed a good catalytic activity for the CO₂ hydration reaction, comparable to that of the human (h) isoform hCA I. Inorganic anions such as thiocyanate, cyanide, azide, hydrogen sulfide, sulfamate and trithiocarbonate were effective PgiCA inhibitors with inhibition constants in the range of 41–97 μM. Other effective inhibitors were diethyldithiocarbamate, sulfamide, and phenylboronic acid, with K_Is of 4.0–9.8 μM. The role of this enzyme as a possible virulence factor of P. gingivalis is poorly understood at the moment but its good catalytic activity and the possibility to be inhibited by a large number of compounds may lead to interesting developments in the field.     

Phylogenetic analysis of rhodolith formation in the Corallinales (Rhodophyta)

Although the ecological importance of rhodolith (maerl, free-living coralline algae) beds is well-known, rhodolith-forming species have been neglected in molecular phylogenetic studies. This is the first molecular systematic study aimed at understanding whether the rhodolith habit is a fixed feature in lineages and determining the relationship (phylogenetic vs. environmental) between rhodolith and crustose habits. Phylogenetic relationships of rhodolith-forming species and encrusting coralline algae at generic and species levels were analysed using SSU rDNA and psbA sequences. Extensive sampling in the European North Atlantic, Pacific and Caribbean Mexico of Phymatolithon, Lithothamnion, Lithophyllum and Neogoniolithon taxa forming rhodoliths and crusts was accompanied by examination of type or topotype material. Phylogenetic reconstruction showed that Neogoniolithon contained a monophyletic group of rhodolith-forming species whereas other rhodolith-formers were closely related to encrusting forms in the genera Phymatolithon, Lithothamnion, Mesophyllum, Hydrolithon, Spongites and Sporolithon. DNA analysis showed that the crust-forming Lithophyllum cf. incrustans/dentatum also forms rhodoliths with a stone nucleus that occur on rocky shores. In contrast, species that form beds of non-nucleate rhodoliths (e.g. Neogoniolithon spectabile, N. strictum, Lithophyllum cf. incrustans/dentatum or sp. 1 and Phymatolithon calcareum) rarely form crusts. The rhodolith habit cannot be used to delimit species for taxonomic or identification purposes. Extensive taxonomic revision will be required to deal with problems such as the position of specimens identified as Lithophyllum margaritae in two unrelated lineages.     

Hydrological attributes and rheophilic freshwater fish: stock assessment

The mathematical and statistical advances in fitting stock assessment models enabled the emergence of the paradigm of “integrated analysis”, which fits all available data to a single model of population dynamics that traditionally has total catch as the only forcing function of the system. This approach, however, allowed us to include, in a flexible way, the effect of hydrological regime as an additional forcing function. We tried to achieve this flexibility by making the annual recruitment rates and spawning biomass adjustable to the attributes of the hydrological cycle data. Our models showed that these attributes are influential in the population dynamics of Brycon hilarii of the Northern Pantanal, and their inclusion in the models allowed best partial fits (which considered fits only to the data components length- and age-compositions, CPUE of juveniles and adults) than the Base-case (without hydrological attributes). The best partial fits where obtained when the attributes “delay of floods” and “intensity of floods” were forcing the spawning biomass and the annual recruitment respectively, indicating that these characteristics of the population may be influenced by specific attributes of the water level. The use of integrated modeling contributed with the advancement of population ecology knowledge of rheophilic fish. It is recommended that freshwater fisheries management be integrated into the hydrology management.     

Clinanthus microstephium,an Amaryllidaceae Species with Cholinesterase Inhibitor Alkaloids: Structure−Activity Analysis of Haemanthamine Skeleton Derivatives

Plants of the Amaryllidaceae family are well‐known (not only) for their ornamental value but also for the alkaloids that they produce. In this report, the first phytochemical study of Clinanthus genus was carried out. The chemical composition of alkaloid fractions from Clinanthus microstephium was analyzed by GC/MS and NMR. Seven known compounds belonging to three structural types of Amaryllidaceae alkaloids were identified. An epimeric mixture of a haemanthamine‐type compound (6‐hydroxymaritidine) was tested as an inhibitor against acetyl‐ and butyrylcholinesterase enzymes (AChE and BChE, respectively), two enzymes relevant in the treatment of Alzheimer's disease, with good results. Structure–activity relationships through molecular docking studies with this alkaloid and other structurally related compounds were discussed.     

Patagonian vegetation turnovers during the Paleogene-Early Neogene: Origin of arid-adapted floras

The structure of the living Patagonian flora, dominated by the steppe, is a direct consequence of past climatic and tectonic events. These arid-adapted communities were widespread during the Late Neogene, but their origin in Patagonia can be traced back to the Paleogene. Vegetational trends throughout Paleocene-Miocene time are based on available paleobotanical and palynological information. Four major supported stages in vegetation turnovers are recognized: (1) Paleocene and Early Eocene floras were rainforest-dominated, including many angiosperms with warm-temperate affinities (e.g., palms, Juglandaceae, Casuarinaceae). However, mainly in the Early Eocene, some geographic areas influenced by warm but drier conditions are suggested by the occurrence of certain taxa (e.g., Anacardiaceae). These areas containing arid-adapted floras would have arisen in Patagonian inland regions, in a generally wet continent. (2) The Middle Eocene-Early Oligocene interval was distinguished by the invasion ofNothofagus forests. Progressive replacements of megathermal communities by meso- and microthermal rainforest are documented.Nothofagus forest expansion suggests a marked cooling trend at this time, although some megathermal elements (AquifoliaceaeIlex, Tiliaceae-Bombacaceae, Sapindaceae) were still present at the beginning of this period. Arid-loving taxa have not been recorded in abundance. (3) Late Oligocene-Early Miocene floras were characterized by the occurrence of shrubby-herbaceous elements belonging to Asteraceae, Chenopodiaceae, Ephedraceae, Convolvulaceae, Fabaceae, and Poaceae. They began to give a modern appearance to plant communities. Xerophytic formations would have occupied coastal salt marshes and pockets in inland areas. Megathermal angiosperms of the Rubiaceae, Combretaceae, Sapindaceae, Chloranthaceae, and Arecaceae occurred mainly during the Late Oligocene. Forests of Nothofagaceae, Podocarpaceae, and Araucariaceae are still documented in extra-Andean Patagonia; however, a contrast between coastal and inland environments may have developed, particularly in the Miocene. (4) Middle-Late Miocene records show an increasing diversity and abundance of xerophytic-adapted taxa, including Asteraceae, Chenopodiaceae, and ConvolvulaceaeCressa/Wilsonia. Expansion of these xerophytic taxa, coupled with extinctions of megathermal/nonseasonal elements, would have been associated with both tectonic and climatic forcing factors, led to the development of aridity and extreme seasonality. These arid-adapted Late Miocene floras are closely related to modern communities, with steppe widespread across extra-Andean Patagonia and forest restricted to the western humid upland regions.

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Resumen   Principales tendencias de la vegetación en Patagonia durante el Paleógeno-Neógeno temprano: origen de las floras adaptadas a condiciones de aridez. La estructura de la flora patagónica actual, dominada por la estepa, es consecuencia directa de los eventos tectónicos y climáticos a los que ha estado sometida. Estas comunidades, adaptadas a condiciones de extrema aridez, se expandieron durante el Neógeno tardío, aunque su origen en Pagatonia pudo haber ocurrido en el Paleógeno. En base a la información paleobotánica y palinolíogica disponible se sustentan las cuatro etapas principales de cambios en la vegetación a través del intervalo Paleoceno-Mioceno: 1-Paleoceno-Eoceno Temprano, con floras dominadas por selvas, incluyendo angiospermas con afinidades megatérmicas (ej. palmeras, Juglandaceae, Casuarinaceae). En el Eoceno Temprano, en algunas áreas geográficas habrían prevalecido condiciones cálidas pero áridas según surge de la presencia de taxones con estos requerimientos (ej. Anacardiaceae). Estos parches xerof íticos se habnían desarrollado en el interior de la Patagonia dentro de un entorno general húmedo. 2-Eoceno Medio-Oligoceno Temprano, caracterizado por la expansión de los bosques deNothofagus. Se documentó un progresivo reemplazo de comunidades megatérmicas por bosques meso y microtérmicos dominados porNothofagus y podocarpáceas, indicando un marcado enfriamiento. Al principio de este intervalo, sin embargo, todavía se reconocen algunos elementos megatérmicos (AquifoliaceaeIlex, Tiliaceae-Bombacaceae, Sapindaceae); los taxones xerofíticos, en cambio, son muy escasos. 3-Oligoceno Tardío-Mioceno Temprano, determinado por la presencia de elementos herbáceo-arbustivos de Asteraceae, Chenopodiaceae, Ephedraceae, Convolvulaceae, Fabaceae, Poaceae, que empezaron a dar una apariencia moderna a las comunidades vegetales. Las formaciones xerofíticas habrían ocupado ambientes costeros como marismas o parches abiertos en áreas internas. Angiospermas megatérmicas como Rubiaceae, Combretaceae, Sapindaceae, Chloranthaceae y Arecacea están bien representadas, en particular en el Oligoceno Tardío. Los bosques de Nothofagaceae, Podocarpaceae y Araucariaceae todavía estarían presentes en la Patagonia extra-andina, pero ya existiría un marcado contraste entre los ambientes continentales y costeros. 4-Mioceno Medio-Tardío, definido por un marcado incremento en la diversidad y abundancia de taxones xerofítícos incluyendo Asteraceae, Chenopodiaceae y ConvolvulaceaeCressa/Wilsonia. La expansión de estas formas y la extinción de elementos megatérmicos, no estacionales, habrían estado asociadas a factures tectónicos y climáticos que condujeron al desarrollo de aridez y extrema estacionalidad. Las floras áridas del Mioceno Tardío se encuentran estrechamente relacionadas con las comunidades modernas, con la estepa expandida en la Patagonia extra-andina y los bosques restringidos a la región húmeda, occidental, de los Andes.