A protein fragment complementation assay for thermophiles is provided wherein a thermophilic bacteria having a temperature-sensitive adenylate kinase is transformed with one or more vectors having sequences encoding a first test peptide operatively fused to a first portion of a thermostable adenylate and a second test peptide operatively fused to a second portion of the thermostable adenylate kinase. Association of the first and second test peptides allows association of the first and second portions of the thermostable adenylate kinase and growth of the thermophilic bacteria at a temperature greater than 70° C.