Summary
Previously, extracellular vesicle production in Gram-positive bacteria
was dismissed due to the absence of an outer membrane, where Gram-negative
vesicles originate, and the difficulty in envisioning how such a process could
occur through the cell wall. However, recent work has shown that Gram-positive
bacteria produce extracellular vesicles and that the vesicles are biologically
active. In this study, we show that Bacillus subtilis produces
extracellular vesicles similar in size and morphology to other bacteria,
characterized vesicles using a variety of techniques, provide evidence that
these vesicles are actively produced by cells, show differences in vesicle
production between strains, and identified a mechanism for such differences
based on vesicle disruption. We found that in wild strains of B.
subtilis, surfactin disrupted vesicles while in laboratory strains
harboring a mutation in the gene sfp, vesicles accumulated in
the culture supernatant. Surfactin not only lysed B. subtilis
vesicles, but also vesicles from Bacillus anthracis, indicating
a mechanism that crossed species boundaries. To our knowledge, this is the first
time a gene and a mechanism has been identified in the active disruption of
extracellular vesicles and subsequent release of vesicular cargo in
Gram-positive bacteria. We also identify a new mechanism of action for
surfactin.
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