Dataset Information

Prophage encoding toxin/antitoxin system PfiT/PfiA inhibits Pf4 production in Pseudomonas aeruginosa.

ABSTRACT: Pf prophages are ssDNA filamentous prophages that are prevalent among various Pseudomonas aeruginosa strains. The genomes of Pf prophages contain not only core genes encoding functions involved in phage replication, structure and assembly but also accessory genes. By studying the accessory genes in the Pf4 prophage in P. aeruginosa PAO1, we provided experimental evidence to demonstrate that PA0729 and the upstream ORF Rorf0727 near the right attachment site of Pf4 form a type II toxin/antitoxin (TA) pair. Importantly, we found that the deletion of the toxin gene PA0729 greatly increased Pf4 phage production. We thus suggest the toxin PA0729 be named PfiT for Pf4 inhibition toxin and Rorf0727 be named PfiA for PfiT antitoxin. The PfiT toxin directly binds to PfiA and functions as a corepressor of PfiA for the TA operon. The PfiAT complex exhibited autoregulation by binding to a palindrome (5'-AATTCN5 GTTAA-3') overlapping the -35 region of the TA operon. The deletion of pfiT disrupted TA autoregulation and activated pfiA expression. Additionally, the deletion of pfiT also activated the expression of the replication initiation factor gene PA0727. Moreover, the Pf4 phage released from the pfiT deletion mutant overcame the immunity provided by the phage repressor Pf4r. Therefore, this study reveals that the TA systems in Pf prophages can regulate phage production and phage immunity, providing new insights into the function of TAs in mobile genetic elements.

SUBMITTER: Li Y

PROVIDER: S-EPMC7264888 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Prophage encoding toxin/antitoxin system PfiT/PfiA inhibits Pf4 production in Pseudomonas aeruginosa.

Li Yangmei Y Liu Xiaoxiao X Tang Kaihao K Wang Weiquan W Guo Yunxue Y Wang Xiaoxue X

Microbial biotechnology 20200404 4

Pf prophages are ssDNA filamentous prophages that are prevalent among various Pseudomonas aeruginosa strains. The genomes of Pf prophages contain not only core genes encoding functions involved in phage replication, structure and assembly but also accessory genes. By studying the accessory genes in the Pf4 prophage in P. aeruginosa PAO1, we provided experimental evidence to demonstrate that PA0729 and the upstream ORF Rorf0727 near the right attachment site of Pf4 form a type II toxin/antitoxin ...[more]

PMID: 32246813

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Project description:Type II toxin-antitoxin (TA) systems are classically composed of two genes that encode a toxic protein and a cognate antitoxin protein. Both genes are organized in an operon whose expression is autoregulated at the level of transcription by the antitoxin-toxin complex, which binds operator DNA through the antitoxin's DNA-binding domain. Here, we investigated the transcriptional regulation of a particular TA system located in the immunity region of a cryptic lambdoid prophage in the Escherichia coli O157:H7 EDL933 strain. This noncanonical paaA2-parE2 TA operon contains a third gene, paaR2, that encodes a transcriptional regulator that was previously shown to control expression of the TA. We provide direct evidence that the PaaR2 is a transcriptional regulator which shares functional similarities to the lambda CI repressor. Expression of the paaA2-parE2 TA operon is regulated by two other transcriptional regulators, YdaS and YdaT, encoded within the same region. We argue that YdaS and YdaT are analogous to lambda Cro and CII and that they do not constitute a TA system, as previously debated. We show that PaaR2 primarily represses the expression of YdaS and YdaT, which in turn controls the expression of paaR2-paaA2-parE2 operon. Overall, our results show that the paaA2-parE2 TA is embedded in an intricate lambdoid prophage-like regulation network. Using single-cell analysis, we observed that the entire locus exhibits bistability, which generates diversity of expression in the population. Moreover, we confirmed that paaA2-parE2 is addictive and propose that it could limit genomic rearrangements within the immunity region of the CP-933P cryptic prophage. IMPORTANCE Transcriptional regulation of bacterial toxin-antitoxin (TA) systems allows compensation of toxin and antitoxin proteins to maintain a neutral state and avoid cell intoxication unless TA genes are lost. Such models have been primarily studied in plasmids, but TAs are equally present in other mobile genetic elements, such as transposons and prophages. Here, we demonstrate that the expression of a TA system located in a lambdoid cryptic prophage is transcriptionally coupled to the prophage immunity region and relies on phage transcription factors. Moreover, competition between transcription factors results in bistable expression, which generates cell-to-cell heterogeneity in the population, but without, however, leading to any detectable phenotype, even in cells expressing the TA system. We show that despite the lack of protein sequence similarity, this locus retains major lambda prophage regulation features.

Dataset Information

Prophage encoding toxin/antitoxin system PfiT/PfiA inhibits Pf4 production in Pseudomonas aeruginosa.

Publications

Prophage encoding toxin/antitoxin system PfiT/PfiA inhibits Pf4 production in Pseudomonas aeruginosa.

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