Novel Functional metabolites that affect biofilm formation are regulated by bioavailable iron with siderophore-dependent pathway

Biofilms are broadly formed by diverse microorganisms under stressful environments and are basically surrounded by an EPS matrix, enabling bacterial cells to confer more resistance to biocides, antibiotics and other invasions than their planktonic counterparts. However, biofilm formation causes problems in various fields, including clinical infections, environmental pollution, agricultural production and industrial contamination. Unfortunately, the mechanism of biofilm formation has not been completely elucidated, and currently, we lack an efficient strategy to tackle these tough problems and destroy biofilms. In the present study, we sought to decipher the mechanism of biofilm formation through the regulation of functional metabolites regulated by iron. By exposing bacterial cells to various concentrations of iron, we found that iron can regulate biofilm formation, and phenotypic changes were obviously dependent on iron concentration. A functional metabolome assay was further implemented to investigate the regulatory mechanism of iron on biofilm formation; we verified that siderophores (linear enterobactin, yersiniabactin, di-glucosylated-salmochelin and HPTT-COOH) mostly account for the transportation of iron into bacterial cells. Then, bioavailable iron was recruited by bacterial cells to direct the biosynthesis and expression of five functional metabolites (L-tryptophan, 5-MTA, spermidine, CMP and L-leucine), which were identified as new effectors that directly regulate biofilm formation. Taken together, this study is the first to identify five new metabolic effectors to efficiently regulate biofilm formation, the biosynthesis and expression of these functional metabolites can be targeted to tackle the challenging problems associated with biofilm formation in different fields.