Deletion analysis of the che operon in the archaeon Halobacterium salinarium

Halobacterium salinarium is a chemo- and phototactic archaeon whose signal transduction pathway includes the classical two-component system made up of CheA and CheY. Deletion analysis of the che operon in H. salinarium has been undertaken. Following the removal of the entire operon, the importance of each of the four individual members, cheY, cheB, cheA, and the novel member cheJ, was evaluated by their replacement in combinations of three. The mutant strains were investigated for their motility, their chemo- and phototactic signalling, and the rotational bias of their flagella. Loss of cheA, cheY or cheB led to the complete loss of chemo- and phototaxis, whereas the absence of cheJ caused a reduction in chemo- and phototactic ability. Reverse swimming and counterclockwise rotation of the flagella required the presence of cheA and CheY. The wild-type 50:50 distribution of forward and reverse swimming was observed in the strain lacking cheB, whereas this distribution was perturbed to 88:12 in the strain lacking cheJ. These results are compared with the corresponding deletion strains in Escherichia coli and provide new insights into the eu- and archeabacterial flagellar switch.