Ni exposure impacts the pool of free Fe and modifies DNA supercoiling via metal-induced oxidative stress in Escherichia coli K-12

Nickel exposure reduces enterobactin production in Escherichia coli

“…Similar to that observed for fepA and sufA , iscR expression gradually decreased throughout lag phase in control cells but remained high throughout lag phase in nickel‐treated cells (Figure c). These results are consistent with other studies and clearly support the hypothesis that nickel disrupts iron metabolism in multiple growth phases in E. coli (Gault et al., ).…”

“…Nickel exposure in lag phase results in lower iron accumulation (Figure a) and a cellular iron starvation response where genes required for adaptation to iron starvation are constitutively expressed at high levels during lag phase nickel exposure (Figure b). Therefore, the disruption of iron homeostasis by lag phase nickel exposure is in good agreement with other recent studies on iron homeostasis and nickel toxicity (Gault et al., ; Rolfe et al., ). Interestingly, once nickel‐exposed cells exit lag phase, the exponential phase duration (doubling time) shows a much milder twofold increase even at the highest nickel concentration tested.…”

“…Taken together, these findings support the notion that high nickel exposure can disrupt siderophore production in E. coli as was previously reported in Pseudomonas aeruginosa under ironlimiting conditions (Visca et al, 1992). These results may provide an additional mechanism to help explain the observed drop in iron accumulation under nickel stress seen in E. coli grown under aerobic conditions in minimal media (Gault et al, 2016). Under those growth conditions where ferric iron predominates, the enterobactin uptake pathway would be the main route for iron entry into the cell.…”

“…Nickel is toxic at low micromolar levels (8 μM) to bacterial cells in exponential phase and nickel was shown to disrupt the zinc-dependent metalloenzyme Class 2 Fructose-bisphosphate aldolase, FbaA (Macomber, Elsey, & Hausinger, 2011). Nickel exposure in exponential phase E. coli was also shown to induce DNA relaxation and damage, possibly by inhibiting DNA replication and RecBCD-mediated DNA repair rather than by generating reactive oxygen species (Gault et al, 2016 andKumar, Mishra, Kaur, &Dutta, 2017). However, Rolfe et al, (2012) have shown that bacterial cells accumulate essential trace metals during lag phase in preparation for the transition into exponential phase.…”

“…Recently, nickel has been shown to lower intracellular iron concentrations possibly by transcriptional repression of iron acquisition genes in E. coli (Gault, Effantin, & Rodrigue, 2016). Furthermore, strains lacking the stress-responsive iron cofactor biogenesis system Suf are more sensitive to nickel stress than wild-type E. coli (Wang, Wu, & Outten, 2011).…”