Toxin-Antitoxin Systems as Phage Defense Elements
Tóm tắt
Toxin-antitoxin (TA) systems are ubiquitous genetic elements in bacteria that consist of a growth-inhibiting toxin and its cognate antitoxin. These systems are prevalent in bacterial chromosomes, plasmids, and phage genomes, but individual systems are not highly conserved, even among closely related strains. The biological functions of TA systems have been controversial and enigmatic, although a handful of these systems have been shown to defend bacteria against their viral predators, bacteriophages. Additionally, their patterns of conservation—ubiquitous, but rapidly acquired and lost from genomes—as well as the co-occurrence of some TA systems with known phage defense elements are suggestive of a broader role in mediating phage defense. Here, we review the existing evidence for phage defense mediated by TA systems, highlighting how toxins are activated by phage infection and how toxins disrupt phage replication. We also discuss phage-encoded systems that counteract TA systems, underscoring the ongoing coevolutionary battle between bacteria and phage. We anticipate that TA systems will continue to emerge as central players in the innate immunity of bacteria against phage.
Từ khóa
Tài liệu tham khảo
Bobonis J, Mateus A, Pfalz B, Garcia-Santamarina S, Galardini M, et al. 2020. Bacterial retrons encode tripartite toxin/antitoxin systems. bioRxiv 2020.06.22.160168. https://doi.org/10.1101/2020.06.22.160168
Bobonis J, Mitosch K, Mateus A, Kritikos G, Elfenbein JR, et al. 2020. Phage proteins block and trigger retron toxin/antitoxin systems. bioRxiv 2020.06.22.160242. https://doi.org/10.1101/2020.06.22.160242
LeRoux M, Srikant S, Littlehale ML, Teodoro G, Doron S, et al. 2021. The DarTG toxin-antitoxin system provides phage defense by ADP-ribosylating viral DNA. bioRxiv 2021.09.27.462013. https://doi.org/10.1101/2021.09.27.462013
Lin L. 1992. Study of bacteriophage T7 gene 5.9 and gene 5.5. Ph.D. Thesis. State University of New York at Stony Brook. 172 pp.
PNAS, 2018, PNAS, 115, E2901