Repeatability and contingency in the evolution of a key innovation in phage lambda

The processes responsible for the evolution of key innovations, whereby lineages acquire qualitatively new functions that expand their ecological opportunities, remain poorly understood. We examined how a virus, bacteriophage λ, evolved to infect its host, Escherichia coli, through a novel pathway. Natural selection promoted the fixation of mutations in the virus's host-recognition protein, J, that improved fitness on the original receptor, LamB, and set the stage for other mutations that allowed infection through a new receptor, OmpF. These viral mutations arose after the host evolved reduced expression of LamB, whereas certain other host mutations prevented the phage from evolving the new function. This study shows the complex interplay between genomic processes and ecological conditions that favor the emergence of evolutionary innovations.     

The rise of chemodiversity in plants

Plants possess multifunctional and rapidly evolving specialized metabolic enzymes. Many metabolites do not appear to be immediately required for survival; nonetheless, many may contribute to maintaining population fitness in fluctuating and geographically dispersed environments. Others may serve no contemporary function but are produced inevitably as minor products by single enzymes with varying levels of catalytic promiscuity. The dominance of the terrestrial realm by plants likely mirrored expansion of specialized metabolism originating from primary metabolic pathways. Compared with their evolutionarily constrained counterparts in primary metabolism, specialized metabolic enzymes may be more tolerant to mutations normally considered destabilizing to protein structure and function. If this is true, permissiveness may partially explain the pronounced chemodiversity of terrestrial plants.     

A fine-scale chimpanzee genetic map from population sequencing

To study the evolution of recombination rates in apes, we developed methodology to construct a fine-scale genetic map from high-throughput sequence data from 10 Western chimpanzees, Pan troglodytes verus. Compared to the human genetic map, broad-scale recombination rates tend to be conserved, but with exceptions, particularly in regions of chromosomal rearrangements and around the site of ancestral fusion in human chromosome 2. At fine scales, chimpanzee recombination is dominated by hotspots, which show no overlap with those of humans even though rates are similarly elevated around CpG islands and decreased within genes. The hotspot-specifying protein PRDM9 shows extensive variation among Western chimpanzees, and there is little evidence that any sequence motifs are enriched in hotspots. The contrasting locations of hotspots provide a natural experiment, which demonstrates the impact of recombination on base composition.     

High-resolution protein structure determination by serial femtosecond crystallography

Structure determination of proteins and other macromolecules has historically required the growth of high-quality crystals sufficiently large to diffract x-rays efficiently while withstanding radiation damage. We applied serial femtosecond crystallography (SFX) using an x-ray free-electron laser (XFEL) to obtain high-resolution structural information from microcrystals (less than 1 micrometer by 1 micrometer by 3 micrometers) of the well-characterized model protein lysozyme. The agreement with synchrotron data demonstrates the immediate relevance of SFX for analyzing the structure of the large group of difficult-to-crystallize molecules.     

Insulinoma in dogs: a review

Insulinomas are rare malignant functional pancreatic tumors of the β cells that retain the ability to produce and secrete insulin. Insulinomas are the most common pancreatic neuroendocrine tumor in dogs that can induce a variety of clinical signs that result from hypoglycemia and secondary neuroglycopenic and adrenergic effects. Diagnosis and treatment is considered challenging, and the prognosis can be extremely variable depending on the therapeutic choices. This review aims to summarize and update classic knowledge with current trends in the diagnosis, treatment, and prognosis of insulinomas.     

Prevalence and on-farm risk factors for diarrhoea in meat lamb flocks in Western Australia

Diarrhoea is a widespread problem for sheep enterprises worldwide. A cross-sectional epidemiological study was conducted using a questionnaire to determine the prevalence of diarrhoea and associated risk factors where there was evidence of recent diarrhoea (active diarrhoea or fresh faecal soiling of breech fleece) for meat lambs on farms in southern Western Australia during 2010. The response rate was 41.4% (139/336). Evidence of recent diarrhoea was reported on 64.8% of farms, with a mean of 6.9% lambs affected per farm. Location of a farm and a higher annual rainfall were associated with an increased diarrhoea prevalence. Binary logistic regression analysis suggested that the drinking water source was associated with the incidence of diarrhoea, since lamb flocks supplied with dam water were 117 times (95% CI: 18.2, 754.8) more likely to have observed diarrhoea or fresh breech fleece faecal soiling than lamb flocks supplied with other sources of water. Faecal worm egg counts were used by 65% of respondents to determine whether an anthelmintic treatment was warranted and 74% of respondents administered a treatment to their meat lambs. In response to a range of diarrhoea scenarios presented to respondents (5%, 25% and 50% of the flock with evidence of recent diarrhoea), 15.1% would have elected to administer an anthelmintic treatment regardless of differences in prevalence.