Clavibacter michiganensis subsp. michiganensis (Cmm) is an important Gram-positive-bacterial pathogen that infects tomato plants causing wilting and cankers and leading to severe economic losses in commercial tomato production worldwide. In order to visualize the infection process of Cmm in germinating seeds, bioluminescent Cmm strains were constructed by transforming the lux reporter gene into the bacterium. A vector pXX2 was constructed by inserting a modified promoterless lux-operon to a Cmm transposon mutagenesis vector, pKGT452Cβ. After electroporation, pXX2 carrying the Cmxr::luxABCDE::Tn1409 cassette resulted in insertion of lux-operon into the Cmm chromosome. The virulent, stable, constitutively bioluminescent strain BL-Cmm17 was selected for further characterization of growth properties and inoculation on tomato seeds. Using this bioluminescent strain, Cmm colonization dynamics of germinating seeds were monitored in real-time using the in vivo imaging system (IVIS).