Controllable secretion of multilayer vesicles driven by microbial polymer accumulation

Michio Sato,Sangho Koh,Nobuhiko Nomura,Masanori Toyofuku,Seiichi Taguchi,Yuki Usukura,Kota Yamashina

doi:10.1038/s41598-022-07218-z

Abstract

Membrane vesicles (MVs) are formed in various microorganisms triggered by physiological and environmental phenomena. In this study, we have discovered that the biogenesis of MV took place in the recombinant cell of Escherichia coli BW25113 strain that intracellularly accumulates microbial polyester, polyhydroxybutyrate (PHB). This discovery was achieved as a trigger of foam formation during the microbial PHB fermentation. The purified MVs were existed as a mixture of outer MVs and outer/inner MVs, revealed by transmission electron microscopy. It should be noted that there was a good correlation between MV formation and PHB production level that can be finely controlled by varying glucose concentrations, suggesting the causal relationship in both supramolecules artificially produced in the microbial platform. Notably, the controllable secretion of MV was governed spatiotemporally through the morphological change of the E. coli cells caused by the PHB intracellular accumulation. Based on a hypothesis of PHB internal-pressure dependent envelope-disorder induced MV biogenesis, here we propose a new Polymer Intracellular Accumulation-triggered system for MV Production (designated “PIA-MVP”) with presenting a mechanistic model for MV biogenesis. The PIA-MVP is a promising microbial platform that will provides us with a significance for further study focusing on biopolymer capsulation and cross-membrane transportation for different application purposes.

Highlights

In this study, unexpectedly, we for the first time found the biogenesis of membrane vesicle (MV) in E. coli by intracellular accumulation of poly(3-hydroxybutyrate) (PHB), a most-studied PHA
The secretion of MVs was well proportioned to the PHB production level that can be finely controlled by the concentration of glucose externally added as a carbon source
The finding of MV biogenesis in our microbial system has been motivated by the reproducible appearance of a lot of bubbles during the aerobic cultivation of the PHB-producing recombinant strain of E. coli

Summary

Introduction

We for the first time found the biogenesis of membrane vesicle (MV) in E. coli by intracellular accumulation of poly(3-hydroxybutyrate) (PHB), a most-studied PHA. Most of the PHA researchers probably have overlooked this phenomenon as being used to be not special In such a sense, the appearance of foam could be a good monitoring indicator for MV biogenesis. We have demonstrated the Polymer Intracellular Accumulation-triggered system for MV Production (designated “PIA-MVP”) with several experimental findings, microscopic observations, and detailed component analysis for fractionated MVs. Notably, the secretion of MVs was well proportioned to the PHB production level that can be finely controlled by the concentration of glucose externally added as a carbon source. The secretion of MVs was well proportioned to the PHB production level that can be finely controlled by the concentration of glucose externally added as a carbon source This causal relationship between both highly-organized supramolecules was found to be spatiotemporally modulated through the morphological change of the E. coli cells. The newly identified PIA-MVP will have a significance on both research fields of the popular supramolecules, PHB and MV

Methods

Results

Conclusion