pMGA phenotypic variation in Mycoplasma gallisepticum occurs in vivo and is mediated by trinucleotide repeat length variation

Abstract

Chickens were infected with a pathogenic strain of MycopLasma gallisepticum, and the expression of pMGA, the major surface protein, was inferred by examination of colonies from ex vivo cells. Within 2 days postinfection, 40% of cells had ceased the expression of the original pMGA surface protein (pMGA1.1), and by day 6, the majority of recovered cells were in this category. The switch in pMGA phenotype which had occurred in vivo was reversible, since most colonies produced from ex vivo progenitors exhibited frequent pMGA1.1+ sectors. After prolonged in vivo habitation, increasing proportions of recovered cells gave rise to variant pMGA colonies which had switched from the expression of pMGA1..