Abstract
E, coli strain K-12, mutants, 58-161, Y-70, Y-40, W-1177 fail to grow in the broth having a higher concentration than M/170-M/200 of cobalt (Co(NO3)2, CoCl2) and nickel (NiSO4, Ni(NO3)2). However, they fail to grow in the broth containing the mixture of M/200_??_M/400 of cobalt and M/200_??_M/400 of nickel. In other words, the mixture of cobalt and nickel seems to have an additional power of inhibition.
The cobalt and the nickel resistant strains were selected from sensitve cells. Their behaviors were as follows. They showed a noticeable cross resistance and parallel increase in resistance with each other, and they formed sepia colonies on a highly concentrated cobalt agar medium.
This leads to the conclusion that the growth inhibition of cobalt and nickel, and the mechanism of their resistance may be identical with each other. Their biochemical behaviors, e. g., indole formation, sugar fermentation, nutritional requirement, gram staining and antibiotic resistance, are similar to those of parent strains.
