Escherichia coli K-12 OST3410 was isolated previously as a stable cyclohexane-tolerant mutant derived from cyclohexane-sensitive strain JA300. A plasmid which provides cyclohexane tolerance to strain JA300 was isolated from the OST3410 genomic library. Subcloning and sequence analysis showed that the plasmid contained the robA gene, whose gene product was reported to bind specifically to the right border of oriC. We observed that the robA gene on the multicopy plasmid generally increased the organic solvent tolerance of several E. coli strains. We also observed an increase in the organic solvent tolerance of JA300 carrying the lac-robA fusion gene on a low-copy plasmid by isopropyl-␤-D-thiogalactopyranoside induction. Strain JA300 carrying the multicopy robA plasmid also showed an increase in resistance to a number of unrelated antibiotics and heavy metal ions, and the spectrum of resistance was significantly similar to that of the soxS-overexpressing strain.

The nucleotide sequence of lambda phage clone 4121, which contains the 18.8 kb fragment of Saccharomyces cerevisiae chromosome VI left arm, was determined. This sequence had seven open reading frames (ORFs), four of which were identical to known genes (ACT1, YPT1, TUB2 and RPO41). Another three ORFs (4121orfR003, 4121orfR004 and 4121orfRN001) were highly homologous to FET3 multi-copper oxidase, glucose transport protein, and hypothetical protein of YIL106w on chromosome IX, respectively. 4121orfRN01 is suggested to contain an intron.

No abstract