Transposon Insertion in the purL Gene Induces Biofilm Depletion in Escherichia coli ATCC 25922

Abstract

Current <i>Escherichia coli</i> antibiofilm treatments comprise a combination of antibiotics commonly used against planktonic cells, leading to treatment failure. A better understanding of the genes involved in biofilm formation could facilitate the development of efficient and specific new antibiofilm treatments. A total of 2578 <i>E. coli</i> mutants were generated by transposon insertion, of which 536 were analysed in this study. After sequencing, Tn263 mutant, classified as low biofilm-former (LF) compared to the wild-type (wt) strain (ATCC 25922), showed an interruption in the <i>purL</i> gene, involved in the de novo purine biosynthesis pathway. To elucidate the role of <i>purL</i> in biofilm formation, a knockout was generated showing reduced production of curli fibres, leading to an impaired biofilm formation. These conditions were restored by complementation of the strain or addition of exogenous inosine. Proteomic and transcriptional analyses were performed to characterise the differences caused by <i>purL</i> alterations. Thirteen proteins were altered compared to wt. The corresponding genes were analysed by qRT-PCR not only in the Tn263 and wt, but also in clinical strains with different biofilm activity. Overall, this study suggests that <i>purL</i> is essential for biofilm formation in <i>E. coli</i> and can be considered as a potential antibiofilm target.