title: Extracellular vesicle proteomes reflect developmental phases of Bacillus subtilis.
abstract: BACKGROUND
  Extracellular vesicles (EV) are spherical membrane-bound vesicles with nano-scale diameters, which are shed to the extracellular region by most eukaryotic and prokaryotic cells. Bacterial EV are proposed to contribute to intercellular communication, bacterial survival and human pathogenesis as a novel secretion system. EV have been characterized from many Gram-negative species and, more recently, from several vegetative Gram-positive bacteria. Further characterization of EV and their molecular cargos will contribute to understanding bacterial physiology and to developing therapeutic approaches.
  
  
  RESULTS
  Bacillus subtilis were observed to release EV to a similar extent during sporulation as during the vegetative growth phase. However, the two vesicular cargos show qualitatively and quantitatively different proteomes. Among 193 total proteins identified across both samples, 61 were shown to be significantly more abundant in EV shed by sporulating cells, with (log) ratio of spectral counts RSC > 1 and Fisher-exact test FDR < 5 %. Sixty-two proteins were found to be significantly more abundant in EV shed by vegetative cells. Membrane fusion was shown to take place between these EVs and Gram-positive cells.
  
  
  CONCLUSIONS
  Biogenesis of EV is a continuous process over the entire life cycle of this sporulating bacterium. The formation of EV during sporulation is strongly supported by the delineation of protein content that differs from the proteome of EV formed by vegetative spores.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742 USA.
authors.forename: Yeji
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC 20057 USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Edwards
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742 USA.
authors.forename: Catherine
authors.identifier: 0000-0003-4979-0229
authors.initials: C
authors.lastname: Fenselau
keywords: Bacillus subtilis; Extracellular vesicles; Label-free quantification; Secretome; Sporulation