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A Thief in the Blight: What Can Erwinia amylovora Bacteria Steal from Their Host?
L. RAMOS (1), J. Sinn (1), B. Lehman (2), E. Pfeufer (1), K. Peter (3), T. McNellis (1). (1) The Pennsylvania State University, State College, PA, U.S.A.; (2) Penn State University - Fruit Research Extension Center, Biglerville, PA, U.S.A.; (3) The Pennsylvania State University / Penn State University - Fruit Research Extension Center, State

 Fire blight is the most destructive bacterial disease of apples, which are the second most consumed fresh fruit in the United States.  The causal agent of fire blight is <i>Erwinia amylovora</i>.  In this study, we tested whether <i>E. amylovora</i> is able to extract sufficient pyrimidine and arginine from the host to allow for bacterial growth and fire blight disease development.  An <i>E. amylovora</i> <i>argD</i> mutant, which had a disrupted arginine biosynthesis pathway, was an arginine auxotroph and did not cause disease or grow in host tissue.  An <i>E. amylovora</i> <i>pyrC</i> mutant, which had a disrupted pyrimidine biosynthesis pathway, was a uracil auxotroph, yet still caused fire blight disease in apple tree shoots and grew in apple and pear immature fruits. Our study suggests that <i>E. amylovora</i> is able to obtain sufficient pyrimidine, but not arginine, from the host tissue to support bacterial growth and fire blight disease development.  This study provides new information about <i>E. amylovora</i> food acquisition potential while growing in the host and could help develop novel possible fire blight controls.  Furthermore, we found that the plasmid used to complement the <i>argD</i> mutant was stably maintained in <i>E. amylovora</i> cells growing <i>in planta</i>. This plasmid could be a useful tool for functional analysis of <i>E. amylovora</i> genes <i>in planta</i>.

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