Demonstration of the genetic stability of a Mycoplasma gallisepticum strain following in vivo passage.

A Mycoplasma gallisepticum strain designated 6/85 (MGI) exhibiting reduced virulence for both chickens and turkeys was sequentially passaged 10 times in each species. DNA extracted from organisms before passage and those isolated after the third, sixth, and 10th passages was studied by restriction endonuclease DNA analysis using BamHI, BglII, EcoRI, HindIII, and PstI endonucleases. The virulent-type strain designated S6 was used as a comparison. Comparison of DNA fragment patterns of MGI and S6 strains showed distinct differences, although some similarities were evident. Passage of the strain in vivo did not affect DNA fragment patterns of the MGI strain. Electrophoretic protein patterns produced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed very similar band patterns in both the MGI and S6 strains. The most notable differences were seen in bands located in the molecular-mass regions of approximately 46.5, 50-54, 58-64, and 105-140 kilodaltons. Alteration of band pattern profiles following in vivo passage of the MGI strain was apparent in a single band at approximately 86 kilodaltons that appeared to stain more intensely following passage.