Using degenerate primers of highly conserved regions of two-component response regulators for PCR amplification, a two-component response regulator was cloned from Candida albicans that is homologous to nik-1+ of Neurospora crassa. This two-component hybrid kinase, CaNIK1, also shows features of bacterial two-component response regulators, including a putative unorthodox second histidine kinase motif at the carboxy-terminal end. CaNIK1 was expressed at low levels in both the white and opaque switch phenotypes and in the bud and hyphal growth forms of C. albicans strain WO-1, but in both developmental programmes, the level of transcript was modulated (levels were higher in opaque cells and in hyphae). Partial deletion of both CaNIK1 alleles, by which the histidine autokinase- and ATP-binding domains were removed, did not inhibit either high-frequency phenotypic switching or the bud-hypha transition in high salt concentrations, but in both cases the efficiency of the developmental process was reduced.