The arms race between prokaryotes and their perpetually evolving predators has fueled the evolution of a defense arsenal. The so-called CRISPR-Cas systems--clustered regularly interspaced short palindromic repeats and associated proteins--are adaptive immune defense systems found in bacteria and archaea. The recent exponential growth of research in the CRISPR field has led to the discovery of a diverse range of CRISPR-Cas systems and insight into their defense functions. These systems are divided into two major classes and six types. Each system consists of two components: a locus for memory storage (the CRISPR array) and cas genes that encode the machinery driving immunity.
It is a truly viral movie unlike any seen before - and could change the future of computing. Researchers have revealed the first film stored in bacterial DNA, and say it could herald a revolution in digital storage. The tiny movie, consisting of just five frames, shows a galloping thoroughbred mare named Annie G galloping in 1887, and were taken by the pioneering photographer for his photo series titled Human and Animal Locomotion, one of the first motion pictures ever made. The tiny movie, consisting of just five frames, shows a galloping thoroughbred mare named Annie G galloping in 1887. To the left are the original frames.
Bacteria have a highly adaptable DNA-detecting and -editing machine called CRISPR-Cas to ward off virus attack. The Cas1-Cas2 integrase, with the help of an accessory protein called IHF (integration host factor), captures foreign DNA motifs into bacterial CRISPR loci. These motifs then act as sensors of any further invaders. By analyzing the integrase complex structure, Wright et al. show how Cas1-Cas2 recognizes the CRISPR array for site-specific integration (see the Perspective by Globus and Qimron). IHF sharply bends DNA, which allows DNA to access two active sites within the integrase complex to ensure sequence specificity for the integration reaction.
Phage Defense Bacteria have diverse mechanisms to protect themselves against phage. Some, such as the CRISPR-Cas system, are always ready to recognize and eliminate invaders. Others, such as toxin-antitoxin systems, are only activated after phage infection. Guegler and Laub investigated the toxIN system that protects Escherichia coli against several bacteriophages. The toxin, toxN, is a ribonuclease and the antitoxin, toxI , is an RNA with an array of repeats. Under normal conditions, toxN cuts toxI and binds the single motif. Infection by the phage T4 shuts off host transcription, including transcription of toxIN . Because toxI is unstable, toxN is released to cleave mRNA in the cell, which by this time is mainly phage derived. This prevents the production of new phage particles. Thus, by appropriating the host's replicative machinery, phage also risk releasing their toxIN nemesis. Mol. Cell 10.1016/j.molcel.2021.03.027 (2021).
Testing for COVID-19 is a critical component in fighting the pandemic. The key is to have accurate and widespread testing. On April 16, 2020, scientists at the University of California San Francisco and Mammoth Biosciences published in Nature Biotechnology a study that uses CRISPR to detect SARS-CoV-2, the coronavirus that causes the COVID-19 disease, in less than an hour. The CRISPR-based diagnostic test for COVID-19 may offer certain advantages over both serology (blood serum) and real-time reverse transcription–polymerase chain reaction (RT-PCR) tests according to the research team. "Although serology tests are rapid and require minimal equipment, their utility may be limited for diagnosis of acute SARS-CoV-2 infection, because it can take several days to weeks following symptom onset for a patient to mount a detectable antibody response," the researchers wrote in the study.