Glacial-interglacial transitions in microbiomes recorded in deep-sea sediments from the western equatorial Atlantic.

In the late Quaternary, glacial-interglacial transitions are marked by major environmental changes. Glacial periods in the western equatorial Atlantic (WEA) are characterized by high continental terrigenous input, which increases the proportion of terrestrial organic matter (e.g. lignin, alkanes), nutrients (e.g. iron and sulphur), and lower primary productivity. On the other hand, interglacials are characterized by lower continental contribution and maxima in primary productivity. Microbes can serve as biosensors of past conditions, but scarce information is available on deep-sea sediments in the WEA. The hypothesis put forward in this study is that past changes in climate conditions modulated the taxonomic/functional composition of microbes from deep sediment layers. To address this hypothesis, we collected samples from a marine sediment core located in the WEA, which covered the last 130 kyr. This region is influenced by the presence of the Amazon River plume, which outputs dissolved and particulate nutrients in vast oceanic regions, as well as the Parnaiba river plume. Core GL-1248 was analysed by shotgun metagenomics and geochemical analyses (alkane, lignin, perylene, sulphur). Two clusters (glacial and interglacial-deglacial) were found based on taxonomic and functional profiles of metagenomes. The interglacial period had a higher abundance of genes belonging to several sub-systems (e.g. DNA, RNA metabolism, cell division, chemotaxis, and respiration) that are consistent with a past environment with enhanced primary productivity. On the other hand, the abundance of Alcanivorax, Marinobacter, Kangiella and aromatic compounds that may serve as energy sources for these bacteria were higher in the glacial. The glacial period was enriched in genes for the metabolism of aromatic compounds, lipids, isoprenoids, iron, and Sulphur, consistent with enhanced fluvial input during the last glacial period. In contrast, interglacials have increased contents of more labile materials originating from phytoplankton (e.g. Prochlorococcus). This study provides new insights into the microbiome as climatic archives at geological timescales.

A new genomic taxonomy system for the Synechococcus collective.

Cyanobacteria of the genus Synechococcus are major contributors to global primary productivity and are found in a wide range of aquatic ecosystems. This Synechococcus collective (SC) is metabolically diverse, with some lineages thriving in polar and nutrient-rich locations and others in tropical or riverine waters. Although many studies have discussed the ecology and evolution of the SC, there is a paucity of knowledge on its taxonomic structure. Thus, we present a new taxonomic classification framework for the SC based on recent advances in microbial genomic taxonomy. Phylogenomic analyses of 1085 cyanobacterial genomes demonstrate that organisms classified as Synechococcus are polyphyletic at the order rank. The SC is classified into 15 genera, which are placed into five distinct orders within the phylum Cyanobacteria: (i) Synechococcales (Cyanobium, Inmanicoccus, Lacustricoccus gen. Nov., Parasynechococcus, Pseudosynechococcus, Regnicoccus, Synechospongium gen. nov., Synechococcus and Vulcanococcus); (ii) Cyanobacteriales (Limnothrix); (iii) Leptococcales (Brevicoccus and Leptococcus); (iv) Thermosynechococcales (Stenotopis and Thermosynechococcus) and (v) Neosynechococcales (Neosynechococcus). The newly proposed classification is consistent with habitat distribution patterns (seawater, freshwater, brackish and thermal environments) and reflects the ecological and evolutionary relationships of the SC.

Valor del tránsito esofágico con Tc 99 en pacientes operados por acalasia de esófago / Value of esophageal transit with Tecnetium 99 in operated patients by esophageal achalasia

Se analiza un método radioisotópico de estudio para la acalasia de esófago, efectuado en el preoperatorio de 35 enfermos con operación de Heller modificada y en el postoperatorio de 21 de ellos. Se practicó tránsito esofágico con tecnecio 99, administrando 500 microcuries diluidos en 15 ml de agua por vía oral, con el paciente de pie. Se determinó el tiempo medio y retención a los 60 segundos; estos valores fueron elevados con respecto a los normales. No se pudieron establecer diferencias significativas entre estas cifras y la gravedad de la disfagia presente en el preoperatorio. Los valores de tiempo medio y retención en el postoperatorio se correspondieron con la mejoría clínica. En los buenos resultados se observó correlación entre los valores de presión del esfínter esofágico inferior y de tiempo medio y retención. Puede concluirse que el método radioisotópico con Tc 99 es una técnica no invasiva, comúnmente aceptada por el paciente y que permite evaluar en forma cuantitativa los resultados del tratamiento quirúrgico en la acalasia esofágica.

Evaluación del reflujo gastroesofágico mediante pHmetría intraesofágica ambulatoria de 24 horas / Ambulatory intraesophageal pHmetry for evalution of gastroesophageal reflux

Se evaluaron 20 pacientes con síntoma de reflujo gastroesofágico mediante pHmetría intraesofágica ambulatoria de 24 hs. Los resultados fueron comparados con aquellos obtenidos en 5 personas asintomáticas. Se estudió el número de reflujo, hora duración relativa del reflujo en porciento y duración promedio; hubo diferencias en los primeros valores y se estableció una buena correlación entre éstos y los hallazgos endoscópicos. En los pacientes con ausencia de esofagitis o inflamación leve de mucosa, los valores patológicos se observaron a predominio de la fase de vigilia, mientras que en aquellos con esofagitis moderadas y graves, los resultados anormales se presentaron tanto en vigilia como en sueño y en general el predominio de esta última. La pHmetría de 24 hs permite cuantificar la presencia de reflujo gastroesofágico en pacientes sintomáticos, enfatizando su utilidad en aquellos casos con síntomas típicos o atípicos y ausencia de manisfestaciones endoscópicas.