Monitoring of bacterial growth and structural analysis as probed by FT-IR spectroscopy.

Fourier-transform infrared spectroscopy was used to explore structural changes in bacteria under different incubation conditions. In particular, differences between Bradyrhizobium japonicum (BRJ) grown in liquid and on solid media were investigated, as well as the rearrangement of BRJ after transfer from one medium to the other. The FT-IR absorption bands located between 1200 and 900 cm-1 region, vary in spectral shape and intensity when BRJ were suspended in solution medium or plated on solid medium. In agreement with the electronic micrograph data, these spectroscopic changes are due to the changes involving the bacterial wall (peptidoglycan) when BRJ are plated in agar medium. By means of this FT-IR ultrastructural study of Bradyrhizobium japonicum bacteria, it has been possible to follow and to evaluate the rate of the molecular change in bacteria without any destructive interference. This indicates that FT-IR spectroscopy can prove to be a valuable technique in the monitoring of metabolic events in bacterial cells relevant to agriculture as well as environmental and health sciences.