Ontology highlight
ABSTRACT:
PROVIDER: PRJNA1160183 | ENA |
REPOSITORIES: ENA
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Project description:Integrons are genetic platforms that acquire new genes encoded in integron cassettes (ICs), building arrays of adaptive functions for bacteria. ICs generally encode promoterless genes, whose expression relies on the PC promoter within the integron platform. Cassette arrays are assumed to be operon-like structures in which expression is dependent on the distance to the Pc. This is especially relevant in large sedentary chromosomal integrons (SCIs,) like the ones in Vibrio species. We have identified 29 gene-less cassettes in 4 Vibrio SCIs, and explored whether their function could be related to regulating the transcription of adjacent ICs. We show that most gene-less cassettes have promoter activity on the sense strand, enhancing the expression of downstream cassettes. Accordingly, we found that most of the superintegron in Vibrio cholerae is not silent. These promoter cassettes can trigger the expression of a silent dfrB9 resistance cassette downstream, increasing trimethoprim resistance >512-fold in V. cholerae and Escherichia coli. Additionally, one cassette had an antisense promoter capable of reducing trimethoprim resistance through transcriptional interference. Our findings highlight the regulatory role of gene-less cassettes in the expression of adjacent cassettes, emphasizing their significance in large SCIs and their clinical importance if captured by mobile integrons.
2023-04-17 | GSE229776 | GEO
Project description:Integrons are genetic elements that enable bacterial adaptation by collecting new genes encoded in integron cassettes (ICs) to create a reservoir of adaptive functions. These cassettes typically lack their own promoters and rely on the integron platform for their expression. Integrons, well-known for spreading antibiotic resistance genes in clinically relevant Gram-negative species, include Mobile Integrons (MIs), that transport over 170 resistance genes. In contrast, Sedentary Chromosomal Integrons (SCIs), ubiquitous in Vibrio species, are primarily found within bacterial chromosomes. However, their functions are not related to antimicrobial resistance and are largely unexplored. SCIs, typified by the Superintegron (SI) in Vibrio cholerae, represent ancient and highly variable regions in bacterial genomes. The SI is extensive, housing 179 integron cassettes, mostly with unknown functions. Although 19 cassettes encode toxin-antitoxin (TA) systems, which stabilize the array, the intricacies of the SI are challenging to study due to its size and unique integrase. To investigate the SI's impact on V. cholerae, we developed the SeqDelTA approach, enabling the gradual deletion of the SI. This deletion facilitates the use of standard genetic tools without SI interference. Our in-depth analysis of the resulting ∆SI strain, covering various aspects, demonstrated no significant alterations in V. cholerae's physiology. Despite their extended coevolution, SCIs appear to be genetically isolated from the host genome.
2023-11-23 | GSE247496 | GEO
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