The presence of CoCl2 increases expression of the Furregulated gene entB .
Growth in the presence of cobalt resulted in derepression of the Fur-regulated gene entB , a phenotype that could be reversed by the addition of iron , cysteine , or glutathione to the growth medium or by anoxic growth .
Mutant strains are sensitive to hydrogen-peroxide and superoxide , deregulate the expression of the Fur-regulated gene entB , and fail to grow on succinate medium .
The status of labile iron can be monitored via expression of the Fur-regulated gene entB .
Regardless of the explanation , these results appear at odds with previous studies , which established that cells exposed to Co contain less iron and reported up-regulation of Fur-controlled entB and fhuF also directly destabilize particularly labile Fe -- S clusters such as those present on Fe -- S scaffolds .