The research paper titled "Creating Polyploid Escherichia coli and its Application in Efficient L-threonine Production" by the team led by Professors Liang Quanfeng and Qi Qingsheng from the State Key Laboratory of Microbial Technology was recently published in Advanced Science. Professor Liang and Professor Qi are the corresponding authors, with doctoral student Wang Sumeng as the first author.

The issue of genomic copy numbers is a fundamental aspect of the field of life sciences. The ultimate goal of synthetic biology is to create new life forms, with the current focus on designing efficient microbial cell factories for high-value production. Increasing the chromosome number in cells significantly enhances genetic diversity, thereby improving the cell's resistance to environmental stress. While polyploidy is common in eukaryotes in nature, its practical application in artificial cells is yet to be fully understood. This study aims to design and construct new prokaryotic artificial polyploid cells to produce biochemicals.

The researchers achieved this by finely regulating cell division, designing and creating a new polyploid Escherichia coli with 2-4 chromosomes. The main gene controlling cell division,ftsZ, was targeted. Inhibiting ftsZ expression prevents cell division while allowing ongoing genome replication to complete. Prolonged inhibition, however, leads to cell cycle termination and death. Conversely, high ftsZ expression results in rapid cell division, forming smaller cells. By constructing a "CmR-terminator-promoter-RBS" element box with varying expression strengths and finely regulating ftsZ expression levels in front of the chromosome, they successfully created Escherichia coli with 2-4 chromosomes.

The polyploid Escherichia coli demonstrated highly stable chromosomes, altered phenotypes, and exhibited significant advantages in cell growth in rich culture media. Moreover, polyploid cells displayed strong acid and acetate salt tolerance. Genes related to amino acid metabolism, energy metabolism, central carbon metabolism, and other pathways were markedly upregulated. The application of this polyploid strain in the efficient production of threonine resulted in the highest reported yield of 160.3g/L.

The created polyploid Escherichia coli serves as a robust and efficient cell factory chassis, providing new strategies and materials for exploring prokaryotic evolution and chromosome functions.

This research received support from the National Natural Science Foundation, the National Key Research and Development Program, and other research projects. The Public Technology Platform for Life and Environmental Research at Shandong University provided crucial support for this work.

Link to the paper: 

https://onlinelibrary.wiley.com/doi/10.1002/advs.202302417