Knockout of tusA facilitates flagella formation and cationic antimicrobial resistance by disrupting Fur transcriptional regulation in Escherichia coli
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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 .
IMPORTANCE
TusA is a sulfur carrier protein involved in tRNA sulfur modification, and its effect on translation has been studied. Recent studies have reported that tusA deficiency affects Fe-S homeostasis and cluster formation in Escherichia coli ; however, its association with the phenotype remains unclear. Based on RNA sequencing, we indicated that the altered gene expression in Δ tusA resulted from the disruption of fur regulation that is controlled by Fe-S clusters. We further demonstrated that enhanced flagella formation and resistance to cationic drugs were mediated by Fur-dependent gene expression alterations. Our data indicate that the regulation of sulfur allocation for tRNA modification by TusA affects the global gene expression in bacteria.
