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; A. GÓMEZ-ZAVAGLIA

Coimbra

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

European Spectroscopy Society on Biological Molecules

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. Our previous results indicate that the main differences among lactobacilli with and without S-layer are located in the region from 1750 to 1370 cm-1, attributed to Amide I and III regions, and in the fingerprint region (< 900 cm-1).   1. U. B. Sleytr and T. J. Beveridge, Trends Microbiol. 7 253 (1999). 2. M. Sára and U.B. Sleytr, J. Bacteriol. 182 859 (2000). 3. S. Avall-Jääskeläinen and A. Palva, FEMS Microbiol. Rev. 29 511 (2005). 4. P G. Garrote, L. Delfederico, R. Bibiloni, A. Abraham, P. Pérez, L. Semorile and G. De Antoni, J. Dair. Res. 71 222 (2004). 5. M. Kahala, K. Savijoki and A. Palva, J. Bacteriol. 179 284 (1997). 6. P. Rosch, M. Schmitt, W. Kiefer and J. Popp, J. Mol. Struc. 661-662 363 (2003). 7. A. Torreggiani and G. Fini, J. Raman Spectrosc. 29(3), 229 (1998).   This work was supported by Agencia Nacional de Promoción Científica y Tecnológica, Argentina (Project PICT/2006/68), PROMEP, Mexico (Project UAZ-PTC-092) and CONACyT, Mexico [Project No. 119491 (2009)], CYTED Program (Ciencia y Tecnología para el Desarrollo) Network P108RT0362 and CONACyT-CONICET (México, Argentina) (bilateral project res. Nº 962/07-05-2009). AGZ and PM are members of the research career CONICET (National Research Council, Argentina). GDA is member of the research career CIC-PBA (Commission for Scientific Research, Buenos Aires).