The paper by Kelsey and Kotthoff proposes the Constraint Satisfaction paradigmas a computational frameworkfor solving the closest string problem. A Constraint Satisfaction Problem specifies a set of constraints on discrete values variables and a solution to such a problem is an assignment of values to variables such that no constraint is violated. Given a set of strings of equal length over a fixed alphabet,the closest string problem consists on finding the string with the smallest possible maximum Hamming distance from any input string. When the input strings consist of nucleotide sequences over the letters A, C, G and T, the closest string has important applications in computational biology. The authors propose search heuristics based on Constraint Satisfaction that provide several orders of magnitude speed-up at and above the optimal distance