Heavy metal-inducible gene expression in Hyphomonas neptunium

Hyphomonas neptunium proliferates by a unique budding mechanism in which daughter cells emerge from the end of a stalk‐like extension emanating from the mother cell body. Studies of this species have so far been hampered by the lack of a genetic system and of molecular tools allowing the regulated expression of target genes. Based on microarray analyses, this work identifies two H. neptunium promoters that are specifically activated by copper and zinc, respectively. Functional analyses show that they have low basal activity and a high dynamic range, thus meeting the requirements for use as a multi‐purpose expression system. Hyphomonas neptunium was exposed to 0.5 mM CuSO4 or 0.5 mM ZnCl2. Samples were taken before as well as 20 min and 60 min after addition of the heavy metal solution.