Parallel evolution in the emergence of highly pathogenic avian influenza A viruses

Abstract: Parallel molecular evolution and adaptation are important phenomena commonly observed in viruses. Here, we exploit parallel molecular evolution to understand virulence evolution in avian influenza viruses (AIV). Highly-pathogenic AIVs evolve independently from low-pathogenic ancestors via acquisition of polybasic cleavage sites. Why some AIV lineages but not others evolve in this way is unknown. We hypothesise that the parallel emergence of highly-pathogenic AIV may be facilitated by permissive or compensatory mutations occurring across the viral genome. We combine phylogenetic, statistical and structural approaches to discover parallel mutations in AIV genomes associated with the highly-pathogenic phenotype. Parallel mutations were screened using a statistical test of mutation-phenotype association and further evaluated in the contexts of positive selection and protein structure. Our resulting mutational panel may help to reveal new links between virulence evolution and other traits, and raises the possibility of predicting aspects of AIV evolution

Arthroscopic meniscal repair with an absorbable screw: results and surgical technique

The results of a new method for arthroscopic all-inside meniscus repair using a biodegradable cannulated screw (Clearfix meniscal screw) were assessed in a medium-term follow-up prospective study. The Clearfix meniscal screw system consists of delivery cannulae, screw driver, and screw implants. After tear debridement, a screw is located on the driver and passed through the cannula to the insertion site, holding the two sides of the tear together under linear compression. Forty-eight patients (48 repairs) with a mean age of 32.7 years were included in the study. Ligament stabilizing procedures were done in 39 patients (81%) who had anterior cruciate ligament deficient knees. Only longitudinal lesions in the red/red or red/white zone were repaired. Follow-up averaged 19 months, with a range from 12 to 48 months. Patients were evaluated using clinical examination, the "Orthopaedische Arbeitsgemeinschaft Knie (OAK)" knee evaluation scheme and magnetic resonance imaging (MRI). Criteria for clinical success included absence of joint-line tenderness, absence of swelling and a negative McMurray test. Postoperatively, there were no complications directly associated with the device. Twelve of 48 repaired menisci (25%) were considered failures according to the above-mentioned criteria. According to the OAK knee evaluation scheme, 38 patients (79%) had an excellent or good result. MRI, however, showed persisting grade III or IV lesions in 35 patients (73%). Analysis showed that age, length of tear, and simultaneous anterior cruciate ligament reconstruction did not affect the clinical outcome. In contrast, risk factors for failure of meniscus repair are chronicity of injury, location of tear more than 3 mm from the meniscosynovial junction and meniscus side (medial)

Hailstones: A Window into the Microbial and Chemical Inventory of a Storm Cloud

Storm clouds frequently form in the summer period in temperate climate zones. Studies on these inaccessible and short-lived atmospheric habitats have been scarce. We report here on the first comprehensive biogeochemical investigation of a storm cloud using hailstones as a natural stochastic sampling tool. A detailed molecular analysis of the dissolved organic matter in individual hailstones via ultra-high resolution mass spectrometry revealed the molecular formulae of almost 3000 different compounds. Only a small fraction of these compounds were rapidly biodegradable carbohydrates and lipids, suitable for microbial consumption during the lifetime of cloud droplets. However, as the cloud environment was characterized by a low bacterial density (Me = 1973 cells/ml) as well as high concentrations of both dissolved organic carbon (Me = 179 µM) and total dissolved nitrogen (Me = 30 µM), already trace amounts of easily degradable organic compounds suffice to support bacterial growth. The molecular fingerprints revealed a mainly soil origin of dissolved organic matter and a minor contribution of plant-surface compounds. In contrast, both the total and the cultivable bacterial community were skewed by bacterial groups (γ-Proteobacteria, Sphingobacteriales and Methylobacterium) that indicated the dominance of plant-surface bacteria. The enrichment of plant-associated bacterial groups points at a selection process of microbial genera in the course of cloud formation, which could affect the long-distance transport and spatial distribution of bacteria on Earth. Based on our results we hypothesize that plant-associated bacteria were more likely than soil bacteria (i) to survive the airborne state due to adaptations to life in the phyllosphere, which in many respects matches the demands encountered in the atmosphere and (ii) to grow on the suitable fraction of dissolved organic matter in clouds due to their ecological strategy. We conclude that storm clouds are among the most extreme habitats on Earth, where microbial life exists

Arthroscopic meniscal repair: a comparative study between three different surgical techniques

The purpose of this prospective study was to evaluate and compare the results of arthroscopic meniscal repair using three different techniques. Between January 2002 and March 2004, 57 patients who met the inclusion criteria underwent an arthroscopic meniscal repair. The outside-in technique was used in 17 patients (group A), the inside-out in 20 patients (group B), while the rest of the 20 patients (group Q were managed by the all-inside technique using the Mitek RapidLoc soft tissue anchor (Mitek Surgical Products, Westwood, MA, USA). Anterior cruciate ligament (ACL) reconstruction was performed in 29 patients (51%). The criteria for clinical success included absence of joint line tenderness, locking, swelling, and a negative McMurray test. The minimum follow-up was one year for all groups. The mean follow-up was 23 months for group A, 22 months for group B, and 22 months for group C. All meniscal repairs were considered healed according to our criteria in group A, while 19 out of 20 repairs (95%) healed in group B. Finally 7 of 20 repairs (35%) were considered failures in group C and this difference was statistically significant in comparison with other groups. The time required for meniscal repair averaged 38.5 min for group A, 18.1 min for group B, and 13.6 min for group C. Operation time for meniscal repair in group A was statistically longer in comparison with other groups. There were no significant differences among the three groups concerning complications. According to our results, arhtroscopic meniscal repair with the inside-out technique seems to be superior in comparison with the other methods because it offers a high rate of meniscus healing without prolonged operation time

Function-specific response to depletion of microbial diversity

Recent meta-analyses suggest that ecosystem functioning increases with biodiversity, but contradictory results have been presented for some microbial functions. Moreover, observations of only one function underestimate the functional role of diversity because of species-specific trade-offs in the ability to carry out different functions. We examined multiple functions in batch cultures of natural freshwater bacterial communities with different richness, achieved by a dilution-to-extinction approach. Community composition was assessed by molecular fingerprinting of 16S rRNA and chitinase genes, representing the total community and a trait characteristic for a functional group, respectively. Richness was positively related to abundance and biomass, negatively correlated to cell volumes and unrelated to maximum intrinsic growth rate. The response of chitin and cellulose degradation rates depended on the presence of a single phylotype. We suggest that species identity and community composition rather than richness matters for specific microbial processes