A Point Mutation in carR Is Involved in the Emergence of Polymyxin B-Sensitive Vibrio cholerae O1 El Tor Biotype by Influencing Gene Transcription
| Autor: | Daisuke Imamura, Asish K. Mukhopadhyay, Masatomo Morita, Sreeja Shaw, Prosenjit Samanta, Thandavarayan Ramamurthy, Shanta Dutta, Amit Ghosh, Priyanka Ghosh, Makoto Ohnishi, Rahul Shubhra Mandal, Rudra Narayan Saha |
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| Rok vydání: | 2020 |
| Předmět: |
0301 basic medicine
Genetics Mutation biology Operon Point mutation 030106 microbiology Immunology medicine.disease_cause medicine.disease biology.organism_classification Microbiology Cholera El Tor 03 medical and health sciences 030104 developmental biology Infectious Diseases Vibrio cholerae medicine Parasitology Allele Polymyxin B medicine.drug |
| Zdroj: | Infection and Immunity. 88 |
| ISSN: | 1098-5522 0019-9567 |
| DOI: | 10.1128/iai.00080-20 |
| Popis: | Antimicrobial peptides play an important role in host defense against Vibrio cholerae. Generally, the V. cholerae O1 classical biotype is polymyxin B (PB) sensitive and El Tor is relatively resistant. Detection of classical biotype traits like the production of classical cholera toxin and PB sensitivity in El Tor strains has been reported in recent years, including in the devastating Yemen cholera outbreak during 2016-2018. To investigate the factor(s) responsible for the shift in the trend of sensitivity to PB, we studied the two-component system encoded by carRS, regulating the lipid A modification of El Tor vibrios, and found that only carR contains a single nucleotide polymorphism (SNP) in recently emerged PB-sensitive strains. We designated the two alleles present in PB-resistant and -sensitive strains carRr and carRs alleles, respectively, and replaced the carRs allele of a sensitive strain with the carRr allele, using an allelic-exchange approach. The sensitive strain then became resistant. The PB-resistant strain N16961 was made susceptible to PB in a similar fashion. Our in silico CarR protein models suggested that the D89N substitution in the more stable CarRs protein brings the two structural domains of CarR closer, constricting the DNA binding cleft. This probably reduces the expression of the carR-regulated almEFG operon, inducing PB susceptibility. Expression of almEFG in PB-sensitive strains was found to be downregulated under natural culturing conditions. In addition, the expression of carR and almEG decreased in all strains with increased concentrations of extracellular Ca2+ but increased with a rise in pH. The downregulation of almEFG in CarRs strains confirmed that the G265A mutation is responsible for the emergence of PB-sensitive El Tor strains. |
| Databáze: | OpenAIRE |
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