Comparing one-step and two-step bait fishing using the bait CheA as an example. The association score of the identified proteins is plotted against the sequence coverage with which the prey protein was identified. The dashed line indicates the threshold used in this study for assuming an interaction. For the underlying data see Additional file 3 and Additional file 4. A One-Step bait fishing. Several Htrs along with their associated proteins as well as the novel interactors PurNH and OE4643R were identified with high association scores. However, the association score for the expected interactor CheW1 is almost 0, which means the SILAC ratio was close to 1, even though this prey was identified with an unusually high sequence coverage. This indicates an enrichment by CheA. B Two-Step bait fishing. Here the interaction with CheW1 is clearly identified, whereas the interactions with the Htrs and with PurNH and OE4643R, which were later confirmed with these proteins as bait, are not detected. PurNH, OE4643R and several Htrs were not even identified, which indicates no or at least much weaker enrichment of these proteins in two-step bait fishing compared to one-step bait fishing.