I will present a joint work with Jean-Baptiste Saulnier (Marseille), Michèle Romanos (Lyon) and Tâm Mignot (Marseille). We revisited the modeling of the so-called rippling phase of the soil bacteria Myxococcus xanthus lifecycle. The emergence of counter-propagating waves has attracted great attention from the mathematical and biophysical communities in the past two decades. Combining recent biological insights, high-resolution microscopy, trajectory analysis, kinetic modeling and numerical simulations, we proposed an integrated scenario for the collective behavior of this fascinating micro-organism, in which traffic congestion seems to play a key role.