220 research outputs found
Current strategies for mobilome research
Mobile genetic elements (MGE) are pivotal for bacterial evolution and adaptation, allowing shuffling of genes even between distantly related bacterial species. The study of MGEs is biologically interesting as the mode of genetic propagation is kaleidoscopic and important, as MGEs are the main vehicles of the increasing bacterial antibiotic resistance that causes thousands of human deaths each year. The study of MGEs has previously focused on plasmids from individual isolates, but the revolution in sequencing technology has allowed the study of mobile genomic elements of entire communities using metagenomic approaches. The problem in using metagenomic sequencing for the study of MGEs is that plasmids and other mobile elements only comprise a small fraction of the total genetic content that are difficult to separate from chromosomal DNA based on sequence alone. Several different approaches have been proposed that specifically enrich plasmid DNA from community samples. Here, we review recent approaches used to study entire plasmid pools from complex environments, and point out possible future developments for and pitfalls of these approaches. Further, we discuss the use of the PacBio long-read sequencing technology for MGE discovery
Genome analysis of Staphylococcus aureus ST291, a double locus variant of ST398, reveals a distinct genetic lineage
Staphylococcus aureus ST291 has been reported as a homologue recombinant double locus variant of the livestock associated S. aureus ST398. However, whole genome sequencing show that ST291 is a unique genetic lineage with highly variable content within its accessory genome compared to both human and livestock associated genome sequenced CC398s
Effect of Air Injection on Nucleation Rates: An Approach from Induction Time Statistics
From
disruption of the supersaturated solution to improved mass
transfer in the crystallizing suspension, the introduction of a moving
gas phase in a crystallizer could lead to improved rates of nucleation
and crystal growth. In this work, saturated air has been injected
to batch crystallizers to study the effects on formation of the first
crystal and subsequent turbidity buildup. To account for the typically
large sample-to-sample variation, nucleation rates were evaluated
for a large number of replicates using probability distributions of
induction times. The slope and the intercept of the distributions
were studied independently, allowing the simultaneous determination
of the mean induction time and a certain detection delay related to
the rate of crystal growth after formation of the first nucleus. When
saturated air was injected in aqueous glycine solutions, the average
detection delay was reduced from 69 to 13 min, and the mean induction
time decreased from 128 to 36 min. The effect on aqueous solutions
of l-arginine was less apparent, with a detection delay reduction
from 15 to 3 min, and no significant changes on the rate of primary
nucleation. These results demonstrate the potential of this technique
for reduction in nucleation induction time and improved mass deposition
rates in crystallization operations
A computational model of ureteral peristalsis and an investigation into ureteral reflux.
The aim of this study is to create a computational model of the human ureteral system that accurately replicates the peristaltic movement of the ureter for a variety of physiological and pathological functions. The objectives of this research are met using our in-house fluid-structural dynamics code (CgLes-Y code). A realistic peristaltic motion of the ureter is modelled using a novel piecewise linear force model. The urodynamic responses are investigated under two conditions of a healthy and a depressed contraction force. A ureteral pressure during the contraction shows a very good agreement with corresponding clinical data. The results also show a dependency of the wall shear stresses on the contraction velocity and it confirms the presence of a high shear stress at the proximal part of the ureter. Additionally, it is shown that an inefficient lumen contraction can increase the possibility of a continuous reflux during the propagation of peristalsis
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