Researchers from Israel, the US, and the UK explore the evolutionary events that may reintroduce virulence to the attenuated polio virus strain used in vaccines. The team did a phylogenetic analysis focused on more than 400 circulating vaccine-derived polioviruses, folding in theoretical analyses and findings from new genome sequencing on attenuated oral polio vaccine type 2 viruses that were shed a couple weeks after vaccination in 11 vaccinated individuals. In most of the virulent, vaccine-derived isolates, the group identified recombinant events affecting a limited number of genome regions — results supported by subsequent cell line and mouse model experiments.
A team based at Boston University and Massachusetts Institute of Technology considers the possibility that an ancient, phosphate-free form of metabolism preceded the phosphate-dependent metabolic methods employed by living organisms today. By computationally constructing metabolic networks that contained compounds that would have existed prebiotically but did not contain phosphate-dependent reactions, the researchers found evidence that a network rich in iron-sulfur-using enzymes could have produced "a broad category of key biomolecules." The authors note that "[o]ur results corroborate and expand previous proposals that a putative thioester-based metabolism could have predated the incorporation of phosphate and an RNA-based genetic system."
Swiss researchers report on regulatory RNAs formed through "concatenation and circularization of excised DNA segments." Using the Paramecium tetraurelia model organism, the team did a series of genomics-informed experiments and small RNA sequencing analyses to look at mechanisms by which Piwi-associated small RNAs become formed from very short, transposon-derived DNA sequences called internal eliminated sequences. "The generation of [internal eliminated sequence RNAs] has been a mystery due to the very short length of the supposed template," the study's authors say. "Here, we demonstrate that Paramecium has evolved a previously undescribed mechanism for transcribing short DNA pieces — their concatenation and circularization."