Toxin-Antitoxin Systems in Bacteria and Archaea

Abstract

Almost all bacteria and many archaea contain genes whose expression inhibits cell growth and may lead to cell death when overproduced, reminiscent of apoptotic genes in higher systems. The cellular targets of these toxins are quite diverse and include DNA replication, mRNA stability, protein synthesis, cell-wall biosynthesis, and ATP synthesis. These toxins are co-expressed and neutralized with their cognate antitoxins from a TA (toxin-antitoxin) operon in normally growing cells. Antitoxins are more labile than toxins and are readily degraded under stress conditions, allowing the toxins to exert their toxic effect. Presence of at least 33 TA systems in Escherichia coli and more than 60 TA systems in Mycobacterium tuberculosis suggests that the TA systems are involved not only in normal bacterial physiology but also in pathogenicity of bacteria. The elucidation of their cellular function and regulation is thus crucial for our understanding of bacterial physiology under various stress conditions.

Biofilm-Related Infections: Bridging the Gap between Clinical Management and Fundamental Aspects of Recalcitrance toward Antibiotics

“…Expression of toxin-antitoxin (TA) modules often leads to a shutdown of bacterial cellular processes. Although the molecular nature of TA modules varies, from protein to RNA molecules, the toxin is usually a stable component that inhibits major cellular functions, such as translation and replication (96,97). To keep a toxin in check, degradable antitoxin antagonizes the effect of the toxin through formation of an inactive complex.…”

Bacterial Genome Instability

“…TA systems are small mobile genetic modules found in bacterial chromosomes, viruses, and mobile elements (207)(208)(209)(210)(211)(212)(213)(214)(215)(216)(217)(218)(219)(220)(221)(222)(223). They are generally composed of two closely linked genes encoding a stable toxin and an unstable antitoxin.…”

“…Toxin proteins can act differently on their host organism. They can impede cell division (224), stop DNA replication (225), cleave mRNAs (226), inhibit transcription (227) or translation (228), attack the cell membrane (229), stop cell wall biosynthesis (230), or decrease ATP synthesis (222).…”

Phylogenetic distribution of extracellular guanyl-preferring ribonucleases renews taxonomic status of two <i>Bacillus</i> strains

“…Composition and arrangement of RNase-containing toxins suggest the distinct physiological role for them. Chromosome-encoded RNases are likely to be involved in stress response of bacterial cells whereas plasmid-encoded RNases serve as aggression factor (Van Melderen, 2010;Yamaguchi et al, 2011). Being the part of S-layer the RNase-containing toxins should be considered as contributing to virulence or defense strategy of the organism (Mignot et al, 2001;Sleytr and Beveridge, 1999).…”