Mickelthwate has guest conducted the Atlanta, Baltimore, Dallas, and Houston symphony orchestras, as well as the Brooklyn Philharmonic, the Chicago Civic Orchestra, the Cleveland Chamber Symphony, and the Eos Orchestra.

During his tenure as assistant conductor with the Atlanta Symphony Orchestra, which concluded in 2004, he co-founded the new music ensemble Bent Frequency and conducted more than 60 Young People's Concerts.

Mickelthwate was born in Germany and studied conducting and piano at the Musikhochschule in Karlsruhe, where as a student he worked as a pianist for the Frankfurt Chamber Opera and the Karlsruhe Opera Studio. After winning a Peabody merit scholarship, he studied in Baltimore with Frederik Prausnitz and Gustav Meier. He later studied with Seiji Ozawa, Robert Spano, and Andr_ Previn at the Tanglewood Institute, and with Leonard Slatkin at the National Conducting Institute in Washington, D.C.

He was previously a finalist for music director posts at the Omaha Symphony and the Asheville Symphony of North Carolina.