Genome engineering of microorganisms has become a standard in microbial biotechnologies. Several efficient tools are available for the genetic manipulation of model bacteria such as Escherichia coli and Bacillus subtilis, or the yeast Saccharomyces cerevisiae. Difficulties arise when transferring these tools to nonmodel organisms. Synthetic biology strategies relying on genome transplantation (GT) aim at using yeast cells for engineering bacterial genomes cloned as artificial chromosomes. However, these strategies remain unsuccessful for many bacteria, including Mycoplasma pneumoniae (MPN), a human pathogen infecting the respiratory tract that has been extensively studied as a model for systems biology of simple unicellular organisms. Here, we have designed a novel strategy for genome engineering based on the recombinase-assisted genomic engineering (RAGE) technology for editing the MPN genome. Using this strategy, we have introduced a 15 kbp fragment at a specific locus of the MPN genome and replaced 38 kbp from its genome by engineered versions modified either in yeast or in E. coli. A strain harboring a synthetic version of this fragment cleared of 13 nonessential genes could also be built and propagated in vitro. These strains were depleted of known virulence factors aiming at creating an avirulent chassis for SynBio applications. Such a chassis and technology are a step forward to build vaccines or deliver therapeutic compounds in the lungs to prevent or cure respiratory diseases in humans.
Keywords: Mycoplasma pneumoniae (MPN); Saccharomyces cerevisiae; genome editing; phage recombinases; recombinase-assisted genomic engineering (RAGE); transformation-associated recombination-cloning (TAR-cloning).