Microbiology Editor's Choice: understanding bacterial production of bioplastics

Posted on October 1, 2019   by Microbiology Society

Each month, a manuscript published in our flagship journal Microbiology is chosen by a member of the Editorial Board. This month, the paper is titled 'Outer membrane protein I is associated with poly-β-hydroxybutyrate granules and is necessary for optimal polymer accumulation in Azotobacter vinelandii on solid medium.' It was chosen by Professor Christiane Dahl.

Polyhydroxyalkanotes (PHAs) are formed as carbon and energy reserves by many bacteria and archaea. Furthermore, they are of considerable industrial benefit, serving in the production of biodegradable plastic. In their interesting paper, Moreno et al. show the surprising effect of outer membrane protein I (OprI) on PHA formation.
The authors prove that OprI is present in preparations of PHA granules isolated from wildtpye Azotobacter vinelandii and provide good evidence that the accumulation of poly-β-hydroxybutyrate (PHB) is reduced in strains lacking OprI. Thus, the article highlights a possible new role for OprI and its effect on the number and size of PHA granules in A. vinelandii. Further work should clarify how OprI is recruited to the granules and define its exact role in PHA metabolism.

Outer membrane protein I is associated with poly-β-hydroxybutyrate granules and is necessary for optimal polymer accumulation in Azotobacter vinelandii on solid medium

The soil bacterium Azotobacter vinelandii synthesises poly-β-hydroxybutyrate (PHB), a biopolymer of industrial interest to produce bioplastic. The PHB accumulates inside the cells as granules coated by proteins with different functions, such as polymet synthesis and determination of number and size of granules. The presence of membrane proteins on PHB granules had been considered as contamination during their extraction process. In this work, we demonstrated that the outer membrane protein I (OprI) is present on PHB granules and is necessary for biopolymer production in A. vinelandii, suggesting that the presence of some membrane proteins on granules may not be contamination.

We spoke with corresponding author Luis Felipe Muriel about his research:

What is your institution and how long have you been there?

I am currently a Postdoctoral Researcher in the Gulf of Mexico Research Consortium (CIGoM), at the Institute of Biotechnology (IBt) of the National Autonomous University of Mexico. I have been at the IBt since 2009, when I joined Dr Guadalupe Espin’s group to do a master´s and PhD. I obtained my PhD in 2015, and I joined CIGoM as a Postdoctoral Researcher in the same year.

What is your research area?

My research area is molecular bacteriology. I was in the lab of Dr Espin for seven years, studying the molecular genetics of poly-β-hydroxybutyrate and alkylresorcinols synthesis in A. vinelandii. As a postdoc, I have been working on the molecular and functional characterisation of marine bacteria able to degrade hydrocarbons, and studying some bacterial transcriptional factors and their application for the design of biosensors. 

What inspired you to research this topic?

In Dr Espin’s lab, I was studying the genetics of PHB synthesis in A. vinelandii. During that time, I identified that a mutation on the OprI gene, which encodes an outer membrane protein, affected the PHB synthesis. As membrane proteins were previously considered as contaminants of PHB granules, we were interested to understand how these proteins could be related to PHB metabolism.

What is the most rewarding part of your research?

In general, I consider that the most rewarding part of my research (former and present) is to understand the power that bacteria have to help us combat environmental contamination through the design of biotechnological tools, and share this knowledge with other people.

What would you be doing if you weren't a scientist?

It’s hard for me to imagine doing anything other than science, but I would probably be an architect.

To access the full paper, click here. Editor's Choice articles published in Microbiology are free to read.