Raman spectroscopy and super resolution microscopy to assess molecular-level changes in Lactobacillus deblrueckii subsp. bulgaricus exposed to freeze-drying

MARRO, MONICA; MARSAL, MARIA; ANDREA GÓMEZ-ZAVAGLIA; NELSON ROMANO; LOZA-ÁLVAREZ, PABLO

Castelldefels

Workshop; vibrational spectroscopy and biomimetic membranes for understanding protective mechanisms of oligosaccharides; 2021

Instituto de Ciencias Fotónicas de Barcelona

When bacteria are submitted to freezing and/or drying, different bacterial structures or components (proteins, lipids, nucleic acids), may suffer damage. Changes in the structure of molecules or in the interaction between them may cause alterations in the way in which those molecules react to infrared radiation, generating then changes in Raman or FTIR spectra. The main goal of this work is to elucidate the mechanisms by which oligosaccharides like FOS protect bacteria during preservation processes, using spectroscopic information. To fulfill this task, is planned to assay and evaluate by Raman spectroscopy and fluorescence microscopy the structural changes in LAB related to the preservation processes, its mean analyse changes of structural features in LAB subjected to freeze drying, and determine if these features could be related with the recovery capacity of the dehydrated bacteria. Bacterial samples will be analysed with super resolution fluorescent imaging and Raman microscopy focusing on different structures like bacterial membrane or DNA after drying processes and during the rehydration / recovery phase. As a whole,the obtained results demonstrate that carbohydrates such as FOS and sucrose act as protective compounds of lactic acid bacteria not only at the level of the organization of their cytoplasmic membrane, but are also associated with the prevention of conformational alterations of intracellular structures such as DNA. The use of super-resolution microscopy shows structural changes at level of the plasma membrane and chromosomal DNA. The co-localization of membrane microdomains and certain regions of the bacterial chromosome would indicate that these structures are involved in the repair of bacterial DNA after rehydration of the microorganisms.