Complementation of the MS-H vaccine strain with wild-type influences its growth characteristics.

The (MS) vaccine strain MS-H harbours a frameshift mutation in (oligopeptide permease transporter) which results in expression of a truncated OppF. The effect of this mutation on growth and attenuation of the MS-H is unknown. In this study, the impact of the mutation on the vaccine phenotype was investigated by introducing a wild-type copy of gene in the MS-H genome. Wild-type was cloned under the promoter into an vector carrying a tetracycline resistance gene. MS-H was successfully transformed with the final construct pMS-oppF-tetM or with a similar vector lacking coding sequence (pMS-tetM). The MS-H transformed with pMS-oppF-tetM exhibited smaller colony size than MS-H transformed with pMS-tetM. Monospecific rabbit sera against C-terminus of OppF detected bands of expected size for full-length OppF in the 86079/7NS parental strain of MS-H and the MS-H transformed with pMS-oppF-tetM, but not in MS-H and MS-H transformed with pMS-tetM. Comparison of the growth curve of MS-H transformants harvested from media with/without tetracycline was conducted using Q-PCR which revealed that MS-H transformed with pMS-tetM had a higher growth rate than MS-H transformed with pMS-oppF-tetM in the media with/without tetracycline. Lastly, the whole genome sequencing of MS-H transformed with pMS-oppF-tetM (passage 27) showed that the chromosomal copy of the mutated had been replaced with a wild-type version of the gene. This study reveals that the truncation of impacts on growth characteristics of the MS-H and provides insight into the molecular pathogenesis of MS and perhaps broader mycoplasma species. The full-length OppF was expressed in MS-H vaccine.Truncation of impacts on growth characteristics of the MS-H.Chromosomal copy of the mutated in MS-H was replaced with wild-type .