The Regulation of the AdcR Regulon in Streptococcus pneumoniae Depends Both on Zn 2+ – and Ni 2+ -Availability

By using a transcriptomic approach, we have elucidated the effect of Ni 2+ on the global gene expression of S. pneumoniae D39 by identifying several differentially expressed genes/operons in the presence of a high extracellular concentration of Ni 2+ . The genes belonging to the AdcR regulon ( adcRCBA, adcAII – phtD, phtA, phtB , and phtE ) and the PsaR regulon ( pcpA, prtA , and psaBCA ) were highly upregulated in the presence of Ni 2+ . We have further studied the role of Ni 2+ in the regulation of the AdcR regulon by using ICP-MS analysis, electrophoretic mobility shift assays and transcriptional lacZ -reporter studies, and demonstrate that Ni 2+ is directly involved in the derepression of the AdcR regulon via the Zn 2+ -dependent repressor AdcR, and has an opposite effect on the expression of the AdcR regulon compared to Zn 2+ .