Date of Completion


Embargo Period



Mycoplasma gallisepticum, RNA-seq, Phase variation

Major Advisor

Steven J. Geary, PhD

Associate Advisor

Joerg Graf, PhD

Associate Advisor

Lawrence K. Silbart, PhD

Associate Advisor

J. Peter Gogarten, PhD

Field of Study



Doctor of Philosophy

Open Access

Open Access


Mycoplasma gallisepticum is the primary etiologic agent of chronic respiratory disease (CRD) in poultry, a disease largely affecting the respiratory tract of poultry, and causing significant economic losses world-wide. Proteins of the variable lipoprotein and hemagglutinin (vlhA) gene family are thought to be important for host interaction, pathogenesis and immune evasion, but the exact role and mechanisms are not well understood. To better understand the phase variation of vlhA genes, we have conducted large scale, next generation sequencing analysis of M. gallisepticum sampled directly from the tracheal mucosa of experimentally infected chickens and those recovered and passaged in-vitro.

In the first study, M. gallisepticum was recovered from the tracheal mucosa over a seven day infection. Of note, the data indicated that, at given time points, specific vlhAs were similarly dominant in multiple independent hosts, suggesting a non-stochastic temporal progression of dominant vlhA expression. Additionally we found that vlhA expression was not dependent on the presence of 12 GAA repeats, suggesting a previously unrecognized mechanism may be responsible, at least in part, for vlhA expression.

In the second study, we report the vlhA profile of M. gallisepticum recovered from the trachea of experimentally infected chickens when the input culture expressed an alternate dominant vlhA. Here we report that even when the culture is dominantly expressing vlhA 2.02, there is an immediate shift at one day post infection to the dominant expression of vlhA 3.03, suggesting the expression of this gene many be essential in the earliest stages of the infection process.