In-situ study of early stages of biofilm formation under different environmental stresses by ATR-FTIR spectroscopy

The Attenuated Total Reflectance Fourier Transform InfraRed (ATR-FTIR) spectroscopy has been very early applied for studying biofilms, in situ, nondestructively, in real time, and under fully hydrated conditions. Because its analysis depth is very thin, typically of the order of 1-2 μm, the ATR-FTIR technique is an interesting tool for monitoring in situ, via the ATR-FTIR fingerprints of biomolecules, not only initial stages of biofilm formation but also subsequently response of the base sessile bacteria monolayer to environmental condition changes and for studying the influence of environmental conditions on bacterial adhesion, biofilm growth or detachment processes. For example, the time evolution of the bands assigned mainly to proteins, nucleic acids, and polysaccharides allows for conveniently monitoring biomass accumulation on the ATR crystal, whereas the detailed analysis of the whole spectral profile may provide information about biochemical and structural changes accompanying bacterial adhesion, biofilm development, detachment processes and environmental condition changes (temperature, hydration rate, nutrient quality and quantity, biocide addition, ...). Consequently, ATRFTIR technique is a valuable tool for gaining more insight, at the molecular level, into bioadhesion mechanisms and biochemical and physiological changes during the early stages of biofilm development. This chapter presents an overview of the uses of ATR-FTIR spectroscopy in this research field and illustrates this approach with some of our recent findings. The basis, the potential, the artefacts, and the current limitations of this approach as well as future directions are discussed.