Acclimation of the Escherichia coli transcriptome after 10 hours of incubation in the presence of gallium nitrate at sublethal levels.

Gallium nitrate has been explored as an FDA-approved alternative to treat antibiotic-resistant bacterial strains. Questions remain as it relates to the full-systems response elicited to counteract its toxic effects. We explored the transcriptomic response profile of Escherichia coli K12 BW25113 when challenged to grow planktonically for 10 hours in the presence of a sublethal concentration of gallium nitrate (1.25 mM, 319.6 µg/mL). Our results yielded significant changes in gene expresson levels: 581 genes were up-regulated, while 791 were down-regulated in our gallium nitrate treatment. Several biological processes became dysregulated to cope with the presence of this metal stressor, including iron homeostasis, sulfate metabolism, oxidative and nitrosative stress response, cysteine biosynthesis, anaerobic respiration, toxin-antitoxin interactions, and DNA repair. Altogether, this work provides a valuable snapshot of how our indicator strain adapts to this metal-induced stress. This is a significant step in understanding how bacteria can adjust their physiology to coexist with sublethal concentrations of metal-based antimicrobials. Two treatment groups were set up: a non-metal control with M9-glucose minimal media, and a metal challenge using the same culture media but spiked with a sublethal concentration of gallium nitrate (1.25 mM, 319.6 µg/mL). Both treatments were inoculated with Escherichia coli K12 BW25113, with three biological trials each. RNA extraction took place after an incubation time of 10 hours at 37 ºC 150 rpm. Differential gene expression was identified by contrasting both treatments, using p-adj value < 0.05 and absolute fold-change (FC) of at least 2 (|log2 FC| > 1) as significance thresholds.