Label-free analysis of biofilm phenotypes by infrared micro- and correlation spectroscopy.

The methodology development for deeply describing the complex biofilm phenotypes is an urgent demand for understanding their basic biology and the central clinic relevance. Here, we developed an infrared microspectroscopy-based method for the quantitative evaluation and description of biofilm phenotypic characteristics by calculating the spectral similarity of the infrared data. Using this approach, we revealed the phenotypic variation during the biofilm formation process and biofilm heterogeneity between two E. coli strains. Two-dimensional correlation spectroscopy was further combined to deeply investigate the biochemical component evolution sequences during E. coli biofilm formation and revealed the first-order of the polysaccharide molecules change, expanding new opportunities for infrared microspectroscopy in revealing molecule evolution in the biofilm formation. This novel development offers a label-free optical toolkit for the bioanalytical analysis of biofilm phenotypes but also paves the way for screening the drugs to modulate the structure and ecology of biofilm microbiome.