Biology subjects

Whiteway, C.

Publications and source records attributed to Whiteway, C..

4 recordsLinked to original sources

bioRxiv2022

Genetic drivers of chromosomal integron stability

Integrons are adaptive bacterial devices that rearrange promoter less gene cassettes into variable ordered arrays under stress conditions, to sample combinatorial phenotypic diversity. Chromosomal integrons often carry hundreds of silent gene cassettes, with integrase-mediated recombination leading to rampant DNA excision and integration, posing a potential threat to genome integrity. How this activity is regulated and controlled, particularly through selective pressures, to maintain such large cassette arrays is unknown. Here we show a key role of promoter-containing toxin-antitoxin (TA) cassettes as abortive systems that kill the cell when the overall cassette excision rate is too high. These results highlight the importance of TA cassettes regulating the cassette recombination dynamics and provide insight into the evolution and success of integrons in bacterial genomes. TeaserThe accumulation of cassette functions in integrons is ensured by toxin-antitoxin systems which kill the cell when the cassette excision rate is too high.

genetics↗

bioRxiv2022

What are the reference strains of Acinetobacter baumannii referring to?

We assembled the whole genome sequence (WGS) of a collection of 43 non-redundant modern clinical isolates and four broadly used reference strains of Acinetobacter baumannii. Comparison of these isolates and their WGS confirmed the high heterogeneity in capsule loci, sequence types, the presence of virulence and antibiotic resistance genes. However, a significant portion of clinical isolates strongly differ when compared to several reference strains in the light of colony morphology, cellular density, capsule production, natural transformability and in vivo virulence. These genetic and phenotypic differences between current circulating strains of A. baumannii and established reference strains could hamper the study of A. baumannii as an entity. The broadly used reference strains led to the current state of the art of the A. baumannii field, however, we propose that established reference strains in the A. baumannii field should be carefully used, because of the high genetic and phenotypic heterogeneities. In this study, we generated a collection of high-quality nucleotide sequences of 43 modern clinical isolates with the corresponding multi-level phenotypic characterizations. Beside the contribution of novel fundamental observations generated in this study, the phenotypic and genetic data, along with the bacterial strains themselves, will be further accessible using the first open access online platform called "Acinetobase". Therefore, a rational choice of modern strains will be possible to select the ones that suit the needs of specific biological questions.

microbiology↗

bioRxiv2021

Antimicrobial activity of a repurposed harmine-derived compound on extensively drug-resistant Acinetobacter baumannii clinical isolates

SynopsisO_ST_ABSObjectivesC_ST_ABSThe spread of antibiotic resistant bacteria is an important threat for human healthcare. Acinetobacter baumannii bacteria impose one of the major issues, as multidrug- to pandrug-resistant strains have been found, rendering some infections untreatable. In addition, A. baumannii is a champion in surviving in harsh environments, being capable of resisting to disinfectants and to persist prolonged periods of desiccation. Due to the high degree of variability found in A. baumannii isolates, the search for new antibacterials is challenging. Here, we screened a compound library to identify compounds active against recent isolates of A. baumannii bacteria. MethodsA repurposing drug screen was undertaken to identify A. baumannii growth inhibitors. One hit was further characterized by determining its IC50 and testing its activity on 43 recent clinical A. baumannii isolates, amongst which 40 are extensively drug- and carbapenem-resistant strains. ResultsThe repurposing screen led to the identification of a harmine-derived compound, called HDC1, which proved to have bactericidal activity on the multidrug-resistant AB5075-VUB reference strain with an IC50 of 48.23 {micro}M. In addition, HDC1 impairs growth of all 43 recent clinical A. baumannii isolates. ConclusionsWe identified a compound with inhibitory activity on all tested, extensively drug-resistant clinical A. baumannii isolates.

microbiology↗

bioRxiv2020

Cassette recruitment in the chromosomal Integron of Vibrio cholerae

Integrons are genetic systems conferring to bacteria a rapid adaptation capability. The integron integrase is able to capture, stockpile and shuffle novel functions embedded in cassettes. This involves the recognition of both substrates, the attI site, and the cassette associated attC sites. Integrons can be sedentary and chromosomally located (SCI) or, carried by conjugative plasmids (Mobile Integron, MI), hence favoring their dissemination among bacteria. Here, for the first time, we investigate the cassette recruitment in the Vibrio cholerae SCI during conjugation and natural transformation. We demonstrated that horizontally transferred cassette can be recruited inside the chromosomal integron. The endogenous integrase expression is sufficiently triggered, after SOS response induction mediated by the entry of single-stranded cassettes during conjugation and natural transformation, to mediate significant cassette insertion. We demonstrate that the attIA insertion is preferential, despite the presence of 180 attC sites in the integron array. Thanks to the presence of a promoter in the attIA site vicinity, all these newly inserted cassettes are expressed and prone to adaptive selection. We also show that the RecA protein is critical for cassette recruitment in V. cholerae SCI but not in MIs. Moreover, a contrario to MIs, the V. cholerae SCI is not active in others bacterial hosts. MIs might have evolved from the SCIs by overcoming host factors, which would explain their large dissemination in bacteria and their role in the antibioresistance expansion.

molecular biology↗