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."