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PNAS Papers on EHEC Adaptations, Malaria Mosquito Gene Drive, Antarctic Invertebrates

Editor's Note: Some of the articles described below are not yet available at the PNAS site, but they are scheduled to be posted some time this week.

For a paper scheduled to appear in PNAS this week, researchers from the University of Glasgow, Newcastle University, and the University of Strathclyde profile genomic features in enterohemorrhagic Escherichia coli (EHEC) strains that do not show characteristic responses to D-serine, an amino acid that is present in urine and normally staunches EHEC. The team used whole-genome sequencing, RNA sequencing, and other approaches to assess D-serine-adapted forms of EHEC, uncovering alterations that appear to affect the bug's ability to take in or degrade D-serine. "These findings highlight the importance of pathogen evolution in determining how host molecules regulate colonization," the authors say, noting that the interactions uncovered in the study "underpin a process known as niche restriction that is important for pathogen success within the host."

A University of California, Irvine-led team proposes a malaria mosquito-modifying gene drive approach called AgNosCd-1. The team focused the AgNosCd-1 strategy — hinging on the Cas9 guide RNA — on a red eye color-related gene known as cardinal in a genetically engineered Anopheles gambiae mosquito species, a known malaria parasite vector. There, the authors report between 98 percent and 100 percent gene drive in mosquito cage trials tracked for several generations, with relatively rare resistance to gene drive at the alleles targeted. "This system is designed to achieve mosquito population modification when coupled with genes encoding anti-parasite effector molecules," they report, "and result in stable and sustainable blocking of malaria parasite transmission."

Researchers from New Zealand, Canada, and elsewhere track genetic diversity in soil invertebrates collected in Antarctica from the late 1990s to 2018, focusing on half a dozen Collembola microarthropod species. Using nearly mitochondrial cytochrome c oxidase enzyme subunit sequences from 91 sites in southern Victoria Land and the Transantarctic Mountains, the team saw signs of site-specific sequence divergence in several Collembola species considered, along with clues to lineages that appeared to split off some 5.5 million years ago. "As Collembola are a living record of past landscape evolution within Antarctica, these findings provide biological evidence to support geological and glaciological estimates of historical [West Antarctic Ice Sheet] dynamics over the last [5 million years]," the authors write, noting that their results "corroborate climate reconstructions and estimates of past warm periods of reduced ice and absent ice shelf in the Ross Sea region, during which time open seaways would have facilitated dispersal of Collembola, and possibly other taxa."