Hyper-stimulation of Pyrococcus furiosus CRISPR DNA uptake by a self-transmissible plasmid.

Pyrococcus furiosus is a hyperthermophilic archaeon with three effector CRISPR complexes (types I-A, I-B, and III-B) that each employ crRNAs derived from seven CRISPR arrays. Here, we investigate the CRISPR adaptation response to a newly discovered and self-transmissible plasmid, pT33.3. Transconjugant strains of Pyrococcus furiosus exhibited dramatically elevated levels of new spacer integration at CRISPR loci relative to the strain harboring a commonly employed, laboratory-constructed plasmid. High-throughput sequence analysis demonstrated that the vast majority of the newly acquired spacers were preferentially selected from DNA surrounding a particular region of the pT33.3 plasmid and exhibited a bi-directional pattern of strand bias that is a hallmark of primed adaptation by type I systems. We observed that one of the CRISPR arrays of our Pyrococcus furiosus laboratory strain encodes a spacer that closely matches the region of the conjugative plasmid that is targeted for adaptation. The hyper-adaptation phenotype was found to strictly depend both on the presence of this single matching spacer as well as the I-B effector complex, known to mediate primed adaptation. Our results indicate that Pyrococcus furiosus naturally encountered this conjugative plasmid or a related mobile genetic element in the past and responds to reinfection with robust primed adaptation.

Analysis of editor in chief gender and associated journal variables among 126 pathology journals.

OBJECTIVES: Gender equity studies have shown that women are underrepresented in journal editor in chief positions, which confer major professional opportunities and influence. We sought to systematically investigate editor in chief gender and journal attributes within pathology. METHODS: We constructed a journal data set using the Scimago Journal & Country Rank and Clarivate Journal Citation Reports databases. We also included official journals of the major medical societies for the 12 pathology subspecialties recognized by the Association of American Medical Colleges. The final data set included 126 journals. We obtained editor in chief gender, impact factor, publication model (ie, hybrid access vs open access), year of founding, and geographic location for all included pathology journals. RESULTS: Women made up only 18% of the 141 total editor in chief positions. This inequity was present irrespective of all pathology journal variables studied. Among 10 journals with 2 editor in chief positions, 5 had only men and 5 had 1 man and 1 woman. All 3 journals with 3 editor in chief positions had 2 men and 1 woman. CONCLUSIONS: Women are significantly underrepresented among editor in chiefs across pathology journals. Journals and affiliated members should advocate for diversity among these influential positions, given their impact on research, science, and medicine.

Histones direct site-specific CRISPR spacer acquisition in model archaeon.

CRISPR-Cas systems provide heritable immunity against viruses and other mobile genetic elements by incorporating fragments of invader DNA into the host CRISPR array as spacers. Integration of new spacers is localized to the 5' end of the array, and in certain Gram-negative Bacteria this polarized localization is accomplished by the integration host factor. For most other Bacteria and Archaea, the mechanism for 5' end localization is unknown. Here we show that archaeal histones play a key role in directing integration of CRISPR spacers. In Pyrococcus furiosus, deletion of either histone A or B impairs integration. In vitro, purified histones are sufficient to direct integration to the 5' end of the CRISPR array. Archaeal histone tetramers and bacterial integration host factor induce similar U-turn bends in bound DNA. These findings indicate a co-evolution of CRISPR arrays with chromosomal DNA binding proteins and a widespread role for binding and bending of DNA to facilitate accurate spacer integration.