"Detection of S-Layer Proteins in Lactobacilli Isolated From Kefir, using Raman Spectroscopy"

C. ARAUJO-ANDRADE, P. MOBILI, E. GERBINO, C. FRAUSTO-REYES, G. L. DE ANTONI, AND A. GÓMEZ ZAVAGLIA.

Coimbra

Congreso; XIVth European Conference on the Spectroscopy of Biological Molecules; 2011

ECSBM

S-layer structures are macromolecular paracrystalline arrays that completely cover the bacterial cell surface (1,2). They are attached to the underlying cell wall by non-covalent bonds and usually may be dissociated and solubilized into protein monomers by chaotropic agents such as guanidine hydrochloride and dissociating agents such as LiCl. S-layers have been described in several species of lactobacilli, such as L. acidophilus, L. helveticus, L. casei, L. brevis, L. buchneri, L. fermentum, L. bulgaricus, L. plantarum, L. kefir and L. parakefir (3,4). On the basis that the S-layers of different species of lactobacilli may be related with certain probiotic properties, the quick determination of bacteria bearing this structure may the useful in the food industry (5). In this regard, Raman spectroscopy provides a huge amount of information with low times of analysis. This fact has broadened the application of this methodology in the last years. For example, it has been used for microorganism characterization and for the analysis of proteins (6,7). The Raman spectra of whole microorganisms depict well defined regions that can be related with specific bacterial structures. On this basis, the aim of this work is to identify the presence or absence of S-layer proteins in different strains of lactobacilli. The use of Raman spectroscopy, together with unsupervised and supervised multivariate methods, such as PCA and PLS-DA, allowed the identification of these superficial structures in a fast way.