Figure 2: Overexpression of zitB hinders differentiation and causes a decrease in the content of Zn as well as Fe, Co and Ni.

(a) The ermEp::zitB construct on pSET162 plasmid (pZitB) was introduced into the chromosome of the wild-type S. coelicolor. The pZitB containing strain showed defect in sporulation (white phenotype) and antibiotic production, whereas the wild-type strain with or without the empty vector (pSET) demonstrated grey spore formation and blue antibiotic production. (b) Expression of the zitB and znuA genes in pZitB containing strain. The zitB and znuA transcripts were analysed by S1 mapping. The band intensity was quantified and presented as relative values obtained from three independent experiments and measured with P values of <0.001 by Student’s t-test. (c) Intracellular amounts of divalent cations (Cu, Zn, Fe, Co and Ni) in the wild-type cells with empty pSET162 vector or pZitB, as assayed by ICP-MS analysis. Mn and Cd were not detected. Average values from three biologically independent samples were presented in ppb (μg per litre wet mycelium) with error bars representing s.d.’s. * and ** indicate measurements with P values of <0.05 and 0.001, respectively, by Student’s t-test.