Mycoplasma Laboratorium - Bacterial Genome Transplantation

Bacterial Genome Transplantation

In order to propagate a synthetic genome the technique to transplant an intact whole bacterial genome into another had to be developed. Oswald Avery's pioneering experiments in the 1940s showed that some bacteria could take up naked DNA and with the advent of molecular cloning techniques DNA elements could be transformed into competent cells, typically cloning vectors, around 5-20 kbp long, and even bacterial artificial chromosomes can be maintained. In 2007, Venter's team reported that they had managed to transfer the chromosome of one species, Mycoplasma mycoides to Mycoplasma capricolum by means of:

• isolating the genome of M. mycoides: gentle lysis of cells trapped in agar — molten agar mixed with cells and let to gelled—, followed by pulse field gel electroporation and the band of the correct size (circular 1.25Mbp) being isolated.
• making the recipient cells of M. capricolum competent: growth in rich media followed starvation in poor media where the nucleotide starvation results in inhibition of DNA replication and change of morphology.
• polyethylene glycol-mediated transformation of the circular chromosome to the DNA-free cells followed by selection.

The term transformation is used to refer to insertion of a vector into a bacterial cell (by electroporation or heatshock), here transplantation is used akin to nuclear transplantation.

The switch from M.genitalium to M.mycoides was spurred due to the faster growth of the latter