Explosive cell lysis as a mechanism for the biogenesis of bacterial membrane vesicles and biofilms

Lynne Turnbull,Ulrich Omasits,Erin S Gloag,Satoshi Ito,Nicola K Petty,Amelia L Hynen,Leo Eberl,Sarah R Osvath,Cynthia B Whitchurch,Gerardo Cárcamo-Oyarce,Xinhui Yap,Raz Shimoni,Christian H Ahrens,Ian G Charles,Gabriella Pessi,Masaharu Kurosawa,Masanori Toyofuku,Rosalia Cavaliere,Leigh G Monahan,Nobuhiko Nomura

doi:10.1038/ncomms11220

Abstract

Many bacteria produce extracellular and surface-associated components such as membrane vesicles (MVs), extracellular DNA and moonlighting cytosolic proteins for which the biogenesis and export pathways are not fully understood. Here we show that the explosive cell lysis of a sub-population of cells accounts for the liberation of cytosolic content in Pseudomonas aeruginosa biofilms. Super-resolution microscopy reveals that explosive cell lysis also produces shattered membrane fragments that rapidly form MVs. A prophage endolysin encoded within the R- and F-pyocin gene cluster is essential for explosive cell lysis. Endolysin-deficient mutants are defective in MV production and biofilm development, consistent with a crucial role in the biogenesis of MVs and liberation of extracellular DNA and other biofilm matrix components. Our findings reveal that explosive cell lysis, mediated through the activity of a cryptic prophage endolysin, acts as a mechanism for the production of bacterial MVs.

Highlights

Many bacteria produce extracellular and surface-associated components such as membrane vesicles (MVs), extracellular DNA and moonlighting cytosolic proteins for which the biogenesis and export pathways are not fully understood
We show that extracellular DNA (eDNA) is produced by P. aeruginosa through explosive cell lysis events mediated by a cryptic prophage endolysin encoded in the R- and F-pyocin gene cluster
In this study, we have shown that explosive cell lysis accounts for the efficient liberation of a variety of cellular components including cytosolic proteins, eDNA and MVs that may serve as public goods in P. aeruginosa biofilms

Summary

Introduction

Many bacteria produce extracellular and surface-associated components such as membrane vesicles (MVs), extracellular DNA and moonlighting cytosolic proteins for which the biogenesis and export pathways are not fully understood. Super-resolution microscopy reveals that explosive cell lysis produces shattered membrane fragments that rapidly form MVs. A prophage endolysin encoded within the R- and F-pyocin gene cluster is essential for explosive cell lysis. A number of cytosolic proteins have been shown to have moonlighting roles in biofilm formation or virulence when released from the cytosol of the cell[10,11] It is currently unclear how many of these biofilm matrix components and moonlighting proteins are liberated into the extracellular milieu or transported to the cell surface. We show that eDNA is produced by P. aeruginosa through explosive cell lysis events mediated by a cryptic prophage endolysin encoded in the R- and F-pyocin gene cluster. Using live-cell super-resolution imaging we show that these explosive cell lysis events produce MVs through vesicularization of shattered membrane fragments

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Results

Conclusion