Removal of mobile genetic elements from the genome of Clostridioides difficile and the implications for the organism's biology.

Clostridioides difficile is an emerging pathogen of One Health significance. Its highly variable genome contains mobile genetic elements (MGEs) such as transposons and prophages that influence its biology. Systematic deletion of each genetic element is required to determine their precise role in C. difficile biology and contribution to the wider mobilome. Here, Tn5397 (21 kb) and ϕ027 (56 kb) were deleted from C. difficile 630 and R20291, respectively, using allele replacement facilitated by CRISPR-Cas9. The 630 Tn5397 deletant transferred PaLoc at the same frequency (1 × 10-7) as 630 harboring Tn5397, indicating that Tn5397 alone did not mediate conjugative transfer of PaLoc. The R20291 ϕ027 deletant was sensitive to ϕ027 infection, and contained two unexpected features, a 2.7 kb remnant of the mutagenesis plasmid, and a putative catalase gene adjacent to the deleted prophage was also deleted. Growth kinetics of R20291 ϕ027 deletant was similar to wild type (WT) in rich medium but marginally reduced compared with WT in minimal medium. This work indicates the commonly used pMTL8000 plasmid series works well for CRISPR-Cas9-mediated gene deletion, resulting in the largest deleted locus (56.8 kb) described in C. difficile. Removal of MGEs was achieved by targeting conjugative/integrative regions to promote excision and permanent loss. The deletants created will be useful strains for investigating Tn5397 or ϕ027 prophage contribution to host virulence, fitness, and physiology, and a platform for other mutagenesis studies aimed at functional gene analysis without native transposon or phage interference in C. difficile 630 and R20291.

Development of a T-ARMS-PCR Assay for Detecting Genetic Polymorphism in the Catalase (rs7943316) Gene in the Iraqi Population with Breast Cancer.

Numerous investigations have demonstrated that oxidative stress is markedly increased in breast cancer patients compared to their healthy counterparts. Catalase (CAT), a crucial antioxidant enzyme, plays a pivotal role in safeguarding cells against oxidative damage initiated by reactive oxygen species (ROS). The CAT (rs7943316) gene encodes catalase, and certain genetic variations in this gene have been observed to modify catalase activity and levels. Such changes can lead to an altered response to oxidative stress, potentially increasing the risk of breast cancer. In light of this, a novel tetra-primer amplification-refractory mutation system (T-ARMS)-PCR assay was developed to investigate the possible correlation between the CAT (rs7943316) gene polymorphism and the development of breast cancer in patients. This method employs a one-step PCR, which is faster, more cost-effective, and more precise than existing techniques. Sanger sequencing was performed to validate the accuracy of our findings. The T-ARMS-PCR assay revealed a significant association between the A/T allele of the CAT (rs7943316) gene and breast cancer. Specifically, individuals with the TT genotype had a higher risk of developing breast cancer than those with the AA genotype. The T allele frequency was greater among breast cancer patients than in the control group, and genotype frequencies were consistent with the principles of the Hardy-Weinberg Equilibrium. This study is the first to showcase a rapid, cost-effective, and high-throughput method for detecting the SNP in the CAT (rs7943316) gene. This method has the potential to be employed in large-scale clinical trials.