Molecular mechanisms of plasmid-determined mercury and cadmium resistances in bacteria

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:5600426

Nucifora, G

The structural basis for induction of the broad spectrum mercurial resistance operon of pDU1358 with inorganic mercury and with phenylmercury acetate was addressed by DNA sequencing analysis (that showed that a major difference occurred in the 3{prime} 29 base pairs of the ital merR gene compared to the merR genes of Tn501 and R100) and by lac-fusion transcription experiments regulated by merR in trans. The lac-fusion results were compared with those from a narrow spectrum operon, and the pDU1358 merR deleted at the 3{prime} end. A hybrid mer operon containing the merR gene from pDU1358 and lacking the merB gene was inducible by both phenylmercury and inorganic Hg{sup 2+}, showing that organomercurial lyase is not needed for induction by organomercurials. A mutant form of pDU1358 merR missing the C-terminal 17 amino acids responded to inorganic Hg{sup 2+} but not to phenylmercury, indicating that the C-terminal region of the MerR protein of the pDU1358 mer operon is required for the recognition of phenylmercury acetate. The down regulation of the mer operon by the merD gene was also measured in trans with complementing mer operons of pDU1358 or R100 or merD{sup {minus}} mutants. In the presence of the merD gene, beta-galactosidase activity was lowered by 2 to 4 fold. The merD gene gene product was visualized by autoradiography. The Cd{sup 2+} resistance determinant cadA of S. aureus was investigated. The nucleotide sequence of the DNA fragment containing the cadA determinant revealed two open reading frames the larger one of which is essential for expression of cadmium resistance.

• Research Organization: Illinois Univ., Chicago, IL (United States)
• OSTI ID: 5600426
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

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