Tryptone soft-agar plates with chloramphenicol 12.5 μg/ml, ampicillin 50 μg/ml, sodium salicylate 0.45 μM and IPTG 25 μM, were inoculated with strains carrying different versions of CheW or CheA in the chromosome, and expressing compatible plasmids pRZ33 (CheY and CheZ) and pCS12 (wild-type Tsr) or pCS12 V398C (Tsr-V398C). Plates were incubated at 32.5 °C for 9 hours. Used strains were UU2700 (wild-type CheA, wild-type CheW), MDP21 (wild-type CheA, no CheW), MDP23 (wild-type CheA, CheW-R62C), MDP22 (wild-type CheA, CheW-R62H), MDP26 (no CheA, wild-type CheW) and MDP28 (CheA-R555Q, wild-type CheW).