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This Week in PNAS: Jul 17, 2012

In a paper published online in advance in PNAS this week, an international team led by investigators at the University of British Columbia compares the genomes of four microsporidia of the genus Encephalitozoon. "Overall, these data suggest that a recent common ancestor of E. hellem and E. romaleae assembled a complete metabolic pathway from multiple independent HGT [horizontal gene transfer] events and that one descendent already is dispensing with much of this new functionality, highlighting the transient nature of transferred genes," the authors write.

The Johns Hopkins Bloomberg School of Public Health's Marcelo Jacobs-Lorena and his colleagues "describe a strategy that uses symbiotic bacteria to deliver anti-malaria effector molecules to the mid-gut lumen, thus rendering host mosquitoes refractory to malaria infection" in PNAS this week. Jacobs-Lorena and his team used the Escherichia coli hemolysin A secretion system to promote the secretion of a variety of anti-Plasmodium effector proteins by the common mosquito symbiotic bacterium Pantoea agglomerans. "These engineered P. agglomerans strains inhibited development of the human malaria parasite Plasmodium falciparum and rodent malaria parasite Plasmodium berghei by up to 98 percent," the authors write, adding that "the proportion of mosquitoes carrying parasites (prevalence) decreased by up to 84 percent for two of the effector molecules," scorpine and (EPIP)4.

A trio of investigators at Princeton University this week shows, in transposon-mutagenized E. coli cells, that there is "a large mutational target size for increasing persistence frequency," which it says "has fundamental implications for the emergence of antibiotic tolerance in the clinical setting."

Elsewhere in this week's PNAS Early Edition, researchers at the University of California, Davis, and at Wageningen University in The Netherlands discuss the "historical genomics of North American maize." Overall, the UC Davis-Wageningen team reports finding that "selection has had limited impact on genome-wide patterns of diversity and ancestry, with little evidence for individual lines contributing disproportionately to the accumulation of favorable alleles in today's elite germplasm."

The Scan

Study Finds Sorghum Genetic Loci Influencing Composition, Function of Human Gut Microbes

Focusing on microbes found in the human gut microbiome, researchers in Nature Communications identified 10 sorghum loci that appear to influence the microbial taxa or microbial metabolite features.

Treatment Costs May Not Coincide With R&D Investment, Study Suggests

Researchers in JAMA Network Open did not find an association between ultimate treatment costs and investments in a drug when they analyzed available data on 60 approved drugs.

Sleep-Related Variants Show Low Penetrance in Large Population Analysis

A limited number of variants had documented sleep effects in an investigation in PLOS Genetics of 10 genes with reported sleep ties in nearly 192,000 participants in four population studies.

Researchers Develop Polygenic Risk Scores for Dozens of Disease-Related Exposures

With genetic data from two large population cohorts and summary statistics from prior genome-wide association studies, researchers came up with 27 exposure polygenic risk scores in the American Journal of Human Genetics.