This guide will focus on microbially induced calcium carbonate precipitation (MICP), one of the most promising and widely explored cases of biomineralisation in research and industry. The applications of MICP will be reviewed alongside some relevant literature before the enzymatic mechanisms behind MICP are described. Urease and carbonic anhydrase, the two enzymes which can be (separately) utilised in MICP, will both be explored. After this, some key resources for iGEM teams wishing to pursue MICP based projects are presented, including compilations of the previous iGEM projects which have been done in the space!
UCL’s 2022 iGEM team has been investigating MICP in an effort to produce a biomaterial for use in construction.
Guidebook highlights
In this section, we will present key aspects of our Biomineralisation guidebook that best represent this body of work. Feel free to download our guide for personal use and click on the sidebar dropdown button to more easily navigate this page.
Highlight 1: Applications of Biomineralisation
Below is a mindmap, of the applications of biomineralisation discussed in the guidebook.
Highlight 2: Previous projects
This section looks to compile and summarise some of the previous biomineralisation iGEM projects involving urease. For each project identified, the organism from which the project has taken genes, the chassis organism which it looks to clone those genes into, the repository parts which have been designed for it, any key data generated by it, and any assays which have been designed/used within it have been described.
All images in this section are taken from the wiki of the relevant team/project, and links to the relevant wikis are provided.
AUC, Turkey 2015 Team
Summary:Looks to express urease (which acts endothermically) as a cooling mechanism. Wiki is half finished and a lot of information is missing, part page doesn’t quantify enzyme activity, though there is some qualitative data.
| Genes from what organism ? | Sporosarcina pasteurii (Urease) |
| Chassis organism ? | Unclear |
| Relevant Parts |
BBa_K1806006 (urease)
|
| Protein expression levels | Unclear, though partial data exists on a colorimetric assay wherein ‘amount of protein’ is given. |
| Assays | N/a |
AHUT, China 2018
Summary:Looks to engineer E. coli to express carbonic anhydrase for carbon capture.
| Genes from what organism ? | Human |
| Chassis organism ? | E. coli DH5alpha– CA was unstable Later designed mutant human CA 2.0 which was simulated to be more thermally stable |
| Relevant Parts |
|
| Protein expression levels | Successfully expressed both carbonic anhydrases in E. coli. |
| Assays | Measures carbonic anhydrase activity via a colorimetric assay which utilises the ability of carbonic anhydrase to act as an esterase in some scenarios. |
Highlight 3: Chassis organisms
The following briefly explores some potential chassis organisms which could be used for microbially induced calcite precipitation (MICP) projects:
E. coli
The obvious benefit to utilising E. coli in all synthetic biology projects is that it is one of the best characterised, most well understood organisms known to science. Protocols for genetic manipulation are well established and reliable, and there is myriad information easily available on how it can form part of a successful engineering solution. Previous iGEM projects, including those mentioned in this document, have found success in expressing urease / carbonic anhydrase in E. coli.
Despite this, however, E. coli is not viewed as an ideal organism for many biomineralisation projects. It is not a naturally biomineralising organism and is not well suited to survive and metabolise in many of the contexts (in the environment, outside of a bioreactor) which bioengineers may wish to utilise their engineered organisms.
Even if a project ultimately looks to use another chassis organism, protein expression in E. coli is worth considering. E. coli will likely be used whilst mutating/cloning DNA, and if cloning / expression with the intended organism proves problematic, then E. coli is a likely fallback which can be used to gather data on your part.