Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons

Seabed-hugging flows called turbidity currents are the volumetrically most important process transporting sediment across our planet and form its largest sediment accumulations. We seek to understand the internal structure and behavior of turbidity currents by reanalyzing the most detailed direct measurements yet of velocities and densities within oceanic turbidity currents, obtained from weeklong flows in the Congo Canyon. We provide a new model for turbidity current structure that can explain why these are far more prolonged than all previously monitored oceanic turbidity currents, which lasted for only hours or minutes at other locations. The observed Congo Canyon flows consist of a short-lived zone of fast and dense fluid at their front, which outruns the slower moving body of the flow. We propose that the sustained duration of these turbidity currents results from flow stretching and that this stretching is characteristic of mud-rich turbidity current systems. The lack of stretching in previously monitored flows is attributed to coarser sediment that settles out from the body more rapidly. These prolonged seafloor flows rival the discharge of the Congo River and carry ~2% of the terrestrial organic carbon buried globally in the oceans each year through a single submarine canyon. Thus, this new structure explains sustained flushing of globally important amounts of sediment, organic carbon, nutrients, and fresh water into the deep ocean

Co-Circulation of 72bp Duplication Group A and 60bp Duplication Group B Respiratory Syncytial Virus (RSV) Strains in Riyadh, Saudi Arabia during 2014 - Fig 3

<p><b>(A) Deduced amino acid alignment and mutations in the second variable region of G protein of the ON1 genotype.</b> The figure includes alignment of study ON1 strains with the prototype strain from Canada (JN257694). The amino acids sequence alignment corresponds to 227–321 amino acids of the prototype strain. Identical residues are indicated by dashes. The two copies of the duplicated 24-amino-acid region in group ON1 strains are indicated by rectangular boxes. Stop codons are indicated by asterisks. Potential N-glycosylation sites (NXT, where X is not proline) are indicated by grey shading. The potential sites for extensive O-glycosylation KPX - - - TTKX motifs are underlined. <b>(B) The amino acid sequence of ON1 genotype showing mutations in the study strains.</b> The sequence corresponds to the 227–321 amino acids of the ON1 prototype strain. The rectangular boxes represent the analogous 24 amino acid region followed by duplicated 24 amino acid region in ON1 strains. Changes at amino acid positions in study strains are shown by arrows.</p

Age wise distribution of the RSV positive cases.

<p>Age wise distribution of the RSV positive cases.</p

Global amino acid variability of the 2^nd HVR of G gene of BA9 lineage is represented by Shannon entropy plot.

<p>BioEdit software was used for calculation of entropy values of every amino acid at a particular position. Entropy values <0.2 were considered conserved whereas amino acids with >0.2 values are considered variable. High entropy value showed maximum variability at that particular position.</p

Shannon entropy plots of deduced amino acid sequences of the second hypervariable region of the G protein.

<p>The data set includes <b>(A)</b> RSV-A: NA1 genotype, n = 26 <b>(B)</b> ON1 genotype, n = 05 and <b>(C)</b> RSV-B: BA genotype, n = 11 of Saudi strains with their respective prototype strains. The entropy plots show the amino acid variability in the second hypervariable region of the G protein gene determined by BioEdit software. The threshold value was set at 0.2. Amino acid sites with entropy values <0.2 are considered conserved and values >0.2 are considered variable.</p

BA9 lineage of respiratory syncytial virus from across the globe and its evolutionary dynamics

<div><p>Respiratory syncytial virus (RSV) is an important pathogen of global significance. The BA9 is one of the most predominant lineages of the BA genotype of group B RSV that has acquired a 60bp duplication in its G protein gene. We describe the local and global evolutionary dynamics of the second hyper variable region in the C- terminal of the G protein gene of the BA9 lineage. A total of 418 sequences (including 31 study and 387 GenBank strains) from 29 different countries were used for phylogenetic analysis. This analysis showed that the study strains clustered with BA (BA9 and BA8) and SAB4 genotype of group B RSV. We performed time-scaled evolutionary clock analyses using Bayesian Markov chain Monte Carlo methods. We also carried out glycosylation, selection pressure, mutational, entropy and Network analyses of the BA9 lineage. The time to the most recent common ancestor (tMRCA) of the BA genotype and BA9 lineage were estimated to be the years 1995 (95% HPD; 1987–1997) and 2000 (95% HPD; 1998–2001), respectively. The nucleotide substitution rate of the BA genotype [(4.58×10⁻³ (95% HPD; 3.89–5.29×10⁻³) substitution/site/year] was slightly faster than the BA9 lineage [4.03×10⁻³ (95% HPD; 4.65–5.2492×10⁻³)]. The BA9 lineage was categorized into 3 sub lineages (I, II and III) based on the Bayesian and Network analyses. The local transmission pattern suggested that BA9 is the predominant lineage of BA viruses that has been circulating in India since 2002 though showing fluctuations in its effective population size. The BA9 lineage established its global distribution with report from 23 different countries over the past 16 years. The present study augments our understanding of RSV infection, its epidemiological dynamics warranting steps towards its overall global surveillance.</p></div

Clinical manifestations of the study patients.

<p>Clinical manifestations of the study patients.</p

Neighbor-joining phylogenetic tree of the 2^nd HVR of G gene of group B RSV; the tree was constructed using Kimura-2 parameter with 1,000 bootstrapping replicates.

<p>Only bootstrap values greater than 70% are shown at the branch nodes. The genotypes are indicated at the right by brackets. Prototype strains (M17213/USA/62) were used as an out-group. The study sequences are indicated by solid colored triangles.</p

Estimated mean evolutionary rate and tMRCA of group B RSV.

<p>Estimated mean evolutionary rate and tMRCA of group B RSV.</p