Knockout of tusA facilitates flagella formation and cationic antimicrobial resistance by disrupting Fur transcriptional regulation in Escherichia coli

tRNA 2-thiouridine synthesizing protein A (TusA), a sulfur-carrier protein, plays a crucial role in tRNA sulfur modification. Recent studies have reported that tusA deficiency affects iron-sulfur (Fe-S) homeostasis and cluster formation in Escherichia coli ; however, its association with this phenotype remains unclear. In this study, we analyzed the phenotype of tusA -deficient E. coli (Δ tusA ) and its underlying mechanisms using RNA sequencing. We observed that tusA deletion disrupted the expression of genes regulated by the ferric uptake regulator Fur or Fur-regulated transcription factors (flagellar transcriptional regulators D and C [FlhDC] and fumarate and nitrate reduction regulator [Fnr]). Increased expression of flhDC , which is the master regulator of flagellar genes facilitated flagella formation even under conditions in which the wild-type formed few flagella. Additionally, Δ tusA was resistant to cationic antibacterial agents, such as cetyltrimethylammonium bromide, cetylpyridinium chloride, and protamine sulfate. This resistance is associated with the increased expression of ompX or ompF , regulated by Fur and Fnr, respectively. Notably, both enhanced flagella formation and resistance to cationic antibacterial agents caused by tusA deletion were abolished in the fur -deficient background. These findings indicate that impaired expression of the fur regulon, possibly because of impaired Fe-S cluster formation, induces multiple phenotypic alterations in Δ tusA .