Toxin–Antitoxin Systems in Bacteria and Archaea

bsrE/SR5 is a type I TA system from prophage-like element P6 of the B. subtilis chromosome. The 256 nt bsrE RNA encodes a 30 aa toxin. The antitoxin SR5 is a 163 nt antisense RNA. Both genes overlap at their 3 0 ends. Overexpression of bsrE causes cell lysis on agar plates, which can be neutralized by sr5 overexpression, whereas deletion of the chromosomal sr5 copy has no effect. SR5 is short-lived with a halflife of 7 min, whereas bsrE RNA is stable with a half-life of >80 min. The sr5 promoter is 10-fold stronger than the bsrE promoter. SR5 interacts with the 3 0 UTR of bsrE RNA, thereby promoting its degradation by recruiting RNase III. RNase J1 is the main RNase responsible for SR5 and bsrE RNA degradation, and PnpA processes an SR5 precursor to the mature RNA. Hfq stabilizes SR5, but is not required for its inhibitory function. While bsrE RNA is affected by temperature shock and alkaline stress, the amount of SR5 is significantly influenced by various stresses, among them pH, anoxia and iron limitation. Only the latter one is dependent on sigB. Both RNAs are extremely unstable upon ethanol stress due to rapid degradation by RNase Y.

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“…in ref. 20 ). In B. subtilis, 14 type I TA systems were proposed, 21 and 5 of them are located on prophage regions.…”

Section: Introductionmentioning

confidence: 99%

A multistress responsive type I toxin-antitoxin system:bsrE/SR5 from theB. subtilischromosome

et al. 2016

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“…Among the cassettes of CIs, a distinct type is notable, encoding members of TA families (15,83,84). TAs are addiction systems encoding a stable toxin and its labile neutralizing antitoxin.…”

Section: Toxin-antitoxin Cassettesmentioning

confidence: 99%

The Integron: Adaptation On Demand

Loot²,

et al. 2015

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The integron is a powerful system which, by capturing, stockpiling, and rearranging new functions carried by gene encoding cassettes, confers upon bacteria a rapid adaptation capability in changing environments. Chromosomally located integrons (CI) have been identified in a large number of environmental Gram-negative bacteria. Integron evolutionary history suggests that these sedentary CIs acquired mobility among bacterial species through their association with transposable elements and conjugative plasmids. As a result of massive antibiotic use, these so-called mobile integrons are now widespread in clinically relevant bacteria and are considered to be the principal agent in the emergence and rise of antibiotic multiresistance in Gram-negative bacteria. Cassette rearrangements are catalyzed by the integron integrase, a site-specific tyrosine recombinase. Central to these reactions is the single-stranded DNA nature of one of the recombination partners, the attC site. This makes the integron a unique recombination system. This review describes the current knowledge on this atypical recombination mechanism, its implications in the reactions involving the different types of sites, attC and attI, and focuses on the tight regulation exerted by the host on integron activity through the control of attC site folding. Furthermore, cassette and integrase expression are also highly controlled by host regulatory networks and the bacterial stress (SOS) response. These intimate connections to the host make the integron a genetically stable and efficient system, granting the bacteria a low cost, highly adaptive evolution potential "on demand".

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“…The prime purpose of plasmid toxin-antitoxin system is to steady the plasmid by eradicating daughter cells that are plasmid deficient by a mechanism known as post segregation killing. These systems are widespread in numerous bacteria but have not reported in pathogen Campylobacter jejuni that causes human gastroenteritis [10].…”

Section: Literature Reviewmentioning

confidence: 99%