Mycoplasma species
share a set of features, such as lack of a cell
wall, streamlined genomes, simplified metabolism, and the use of a
deviant genetic code, that make them attractive approximations of
what a chassis strain should ideally be. Among them,
Mycoplasma
pneumoniae
arises as a candidate for synthetic biology projects,
as it is one of the most deeply characterized bacteria. However, the
historical paucity of tools for editing Mycoplasma genomes has precluded
the establishment of
M. pneumoniae
as a suitable
chassis strain. Here, we developed an oligonucleotide recombineering
method for this strain based on GP35, a ssDNA recombinase originally
encoded by a
Bacillus subtilis
-associated phage.
GP35-mediated oligo recombineering is able to carry out point mutations
in the
M. pneumoniae
genome with an efficiency as
high as 2.7 × 10
–2
, outperforming oligo recombineering
protocols developed for other bacteria. Gene deletions of different
sizes showed a decreasing power trend between efficiency and the scale
of the attempted edition. However, the editing rates for all modifications
increased when CRISPR/Cas9 was used to counterselect nonedited cells.
This allowed edited clones carrying chromosomal deletions of up to
1.8 kb to be recovered with little to no screening of survivor cells.
We envision this technology as a major step toward the use of
M. pneumoniae
, and possibly other Mycoplasmas, as synthetic
biology chassis strains.