Oh My Vesicle!

A new general mechanism regulating OMV production on Gm negative bacteria

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An interesting paper was just published in Nature Communications linking the putative phospholipid transport system Vac/Yrb to outer membrane vesicle (OMV) formation in Haemophilus influenzae and Vibrio cholerae.

A novel mechanism for the biogenesis of outer membrane vesicles in Gram-negative bacteria

Sandro Roier, Franz G. Zingl, Fatih Cakar, Sanel Durakovic, Paul Kohl, Thomas O. Eichmann, Lisa Klug, Bernhard Gadermaier, Katharina Weinzerl, Ruth Prassl, Achim Lass, Günther Daum, Joachim Reidl, Mario F. Feldman & Stefan Schild

Nature Communications 7, Article number: 10515 doi:10.1038/ncomms10515

As the authors nicely describe, there are three leading theories to describe the mechanism governing OMV; loss of covalent contact between the OM and peptidoglycan (PG) allow the OM to protrude and the vesiculate; accumulation of misfolded protein and PG fragments exert a turf or pressure on the OM causing it to bulge, leading to vesiculation; enrichment of membrane curvature inducing molecules result in bulging and ultimately vesicle formation.

Now Roier et al add a fourth, with the identification of Vac/Yrb via a transposon mutagenesis screen for genes that impact OMV production in Haemophilus. They see that gene deletions of vacJ and yrbE leads to increases in OMV production in both H. influenzae and V. cholerae while analysis of the lipidome of these vesicles reveals that they are enriched on phospholipids and some fatty acids. The authors also see that Vac and YrbE levels respond to iron starvation.

They propose a model whereby loss of vacJ or Yrb genes leads to increased phospholipid in the outer leaflet of the OM leading to an outward bulging. Why would this be iron regulated? They hypothesize that when the bacteria encounter iron limiting conditions in vivo, down regulation of these genes resulting in increased production of OMVs which counteract host serum and complement defences.

It's an interesting model that will bear some further testing but at the least this study supports the growing interest in how OMVs are produced and what functions they carry out.

Andrew Jermy

Consultant, Germinate

Andrew gained his PhD in Molecular Biology from the University of Manchester, UK, studying fungal protein trafficking and secretion. He was subsequently a microbiology editor at Nature for more than a decade, joining Nature Reviews Microbiology in 2008 as an Associate Editor after a brief stint as locum editor on Nature Cell Biology. Over the following 4.5 years Andrew developed a passion for the field, commissioning Reviews and writing on all aspects of microbiology. He also took a keen interest in developing new approaches to communicate with the microbiology community. In January 2013 Andrew joined the Nature team as Senior Editor, handling primary manuscripts from across the field and championing microbiology in Nature’s pages and beyond. Andrew left Nature in April 2015 to become the Chief Editor for the launch of Nature Microbiology. Having helped to establish Nature Microbiology as one of the premier journals in the microbiology publishing landscape, and in search of a better work-life balance, in January 2019 he left Nature to become Chief Publishing Officer (and tea boy) for the family GCSE and A-Level educational resources business established by his wife over the preceding three years.