A key advantage of DNA-mediated colloidal assembly is the ability to tune the strength of adhesion between particles based on sequence characteristics. In the current study, we have investigated DNA-mediated assembly of polystyrene colloidal particles as a function of sequence length, sequence fidelity, and probe density for DNA sequences patterned from the Salmonella genome. The results of our work indicate that the density of DNA probe strands heavily influences the ability of immobilized sequences to hybridize between surfaces of bidisperse colloidal particles. Incubating suspensions at higher temperatures (to minimize secondary structures that might otherwise compromise duplex formation) was also found to have less effect than duplex density on DNA-mediated particle assembly. We believe these results may add to the understanding and design considerations of directed particle assembly using DNA hybridization, especially in the submicrometer and micrometer size regime.