Evaluation of acetone as a solvent for the Ames test.

BACKGROUND: Acetone is a common alternative solvent used in the Ames test when test chemicals are unstable or poorly soluble in water or dimethyl sulfoxide (DMSO). Yet, there is a very limited number of studies evaluating acetone as a solvent in the modified Ames test with preincubation (preincubation test). RESULTS: We evaluated the acetone as a solvent for the preincubation test. Fourteen mutagens dissolved in acetone was added each to the reaction mixture at 2 different volumes (25 or 50 µL) to examine mutagenicity using bacterial test strains recommended in the Organization for Economic Cooperation and Development (OECD) test guideline 471, and compared with DMSO (100 µL). Cytotoxicity of acetone was also examined in these bacterial strains. TA1537 was most sensitive to the cytotoxicity of acetone, the degree of which was moderate and similar to DMSO in TA1537 without S9 mix. In other strains, cytotoxicity was limited to a mild degree with or without S9 mix. Cytotoxicity of acetone did not affect detection of mutagenicity of any mutagens; many of them being comparable or less mutagenic than those with DMSO. CONCLUSIONS: These findings indicate that acetone is a viable candidate as a solvent for the preincubation test in the 5 bacterial strains.

Characterization of two regulatory genes of the mercury resistance determinants from TnMERI1 by luciferase-based examination.

The broad-spectrum mercury resistance transposon, TnMERI1, of Bacillus megaterium strain MB1, contains three proposed operator/promoter (O/P) transcriptional start sites and two regulatory genes (merR1 and merR2). A series of luciferase (lux)-based transcriptional fusion plasmids were studied in Escherichia coli to show that both merR1 and merR2 gene products repressed transcription from O/PmerB3, O/PmerR1, and O/PmerR2 under uninduced conditions. Derepression occurred when the merR1 gene was present and Hg(2+) functioned as an inducer. In the presence of organomercurial compounds, basal transcription of merB3 was needed to produce inorganic Hg(2+) as the inducer of expression regulated by MerR1 at O/PmerB3. The presence of merR2 repressed transcription from all three O/Pmer sites under both non-induced conditions and when inorganic Hg(2+) or organomercurials were added. These results show that MerR1 functions as a repressor in the absence of Hg(2+) and as an activator in the presence of Hg(2+), while MerR2 functions as a repressor.