Short Description

Peptidosomes are great.

Background

Bacteria are omnipresent in biotechnology and applied projects. They can be used as hosts to produce nearly any biological compound of interest such as: drugs, vaccines, enzymes, antibiotics or even fuels and solvents. Their fast life cycle and comparable low requirements of living conditions highlight their industrial relevance. Over the last decades, the main focus to increase yields laid on extensive metabolic engineering and optimizing growth conditions.

Yet, there are more aspect which need to be considered when producing a compound of interest. First, where is the product of interest found: inside of the producing strain or will it be secreted to the surrounding media? Second, what is necessary to separate the valuable end-product from the bacteria? And maybe most important, how to assure a safe use of genetically engineered production strains?
If you would like to know more on encabsulated bacteria in Peptdisomes and boosting the production of a compound of interest check out our: Signal Peptide Toolbox and Peptide Secretion sections.

To address these major biological and technical questions, the TU Dresden iGEM team presents EncaBcillus. Using Bacillus subtilis as model organism we introduce a new fundamental approach for cultivation of bacteria: the Peptidsomes. These Peptidosmes are buildup of self-assembled dipeptide phenylalanines (FF) and are able to form spherical cages. The cages hold back the bacteria from the surrounding but are freely diffusible for smaller molecules. We show, that B. subtilis is able to grow, while encapsulated inside of the Pepdiosomes and demonstrate the applicability of two (fluorescence and luminescence) reports for the use with Pepdiosomes.

While evaluating this new method of bacterial immobilization, we established two applications using Peptidsomes:

• An encapsulated β-lactam Biosensor
• Communication between encapsulated bacteria and their surrounding

Design

The process to generate peptidosomes is simple. First a droplet of Fmoc-FF solution is deposited on an ultra-hydrophobic surface. The droplet will not wet the surface and instead it will keep its rounded shape. Afterwards it is exposed to gaseous CO2, which reacts with the H2O of the solution. The reaction produces protons and the pH drops, triggering the self-assembly of the dipeptide. The CO2 is only in direct contact with the surface of the droplet, so self-organization will occur in this interphase, creating a membrane that surrounds a liquid core.