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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Microbiol. | doi: 10.3389/fmicb.2019.02708

Vesicles from Vibrio cholerae contain AT-rich DNA and shorter mRNAs that do not correlate with their protein products

  • 1Section of Pharmacology and Pharmaceutical biosciences, Department of Pharmacy, University of Oslo,, Norway
  • 2Centre for Integrative Microbial Evolution (CIME) , University of Oslo, Norway
  • 3Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Norway

Extracellular vesicles secreted by Gram-negative bacteria have proven to be important in bacterial defense, communication and host-pathogen relationships. They resemble smaller versions of the bacterial mother cell, with similar contents of proteins, LPS, DNA and RNA. Vesicles can elicit a protective immune response in a range of hosts, and as a potential vaccine candidates, it is of interest to characterize their cargo. Genetic sequencing data is already available for vesicles from several bacterial strains, but it is not yet clear how the genetic makeup of vesicles differ from that of their parent cells, and which properties that may characterize potentially enriched genetic material.

The present study provides evidence for DNA inside vesicles from Vibrio cholerae O395, and key characteristics of their genetic and proteomic content are compared to that of whole cells. DNA analysis reveals enrichment of fragments containing ToxR binding sites, as well as a positive correlation between AT-content and enrichment. Some mRNAs were highly enriched in the vesicle fraction, such as membrane protein genes ompV, ompK and ompU, DNA-binding protein genes hupA, hupB, ihfB, fis and ssb, and a negative correlation was found between mRNA enrichment and transcript length, suggesting mRNA inclusion in vesicles may be a size-dependent process. Certain non-coding and functional RNAs were found to be enriched, such as VrrA, GcvB, tmRNA, RNase P, CsrB2 and CsrB3. Mass spectrometry revealed enrichment of outer membrane proteins, known virulence factors, phage components, flagella and extracellular proteins in the vesicle fraction, and a low, negative correlation was found between transcript\textendash, and protein enrichment. This result opposes the hypothesis that a significant degree of protein translation occurs in vesicles after budding. The abundance of viral- and flagellar proteins in the vesicle fraction underlines the importance of purification during vesicle isolation.

Keywords: Vibrio cholerae, non-coding RNAs, Bacteriophages, Extracellular vesicles (EVs), Extracellular genetics, Extracellular proteomics

Received: 06 Aug 2019; Accepted: 08 Nov 2019.

Copyright: © 2019 Langlete, Krabberød and Winther-Larsen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Hanne C. Winther-Larsen, Section of Pharmacology and Pharmaceutical biosciences, Department of Pharmacy, University of Oslo,, Oslo, Norway, hannewi@farmasi.uio.no