INVESTIGADORES
TYMCZYSZYN Emma Elizabeth
congresos y reuniones científicas
Título:
Biosorption of Metal ions to Lactobacillus kefir and Lactobacillus kefir S layers. A Vibrational Spectroscopy study
Autor/es:
GERBINO, E.; MOBILI, P; TYMCZYSZYN E,; ARAUJO-ANDRADE C.; FRAUSTO-REYES C.; FAUSTO RUI; GOMEZ ZAVAGLIA, A.
Lugar:
Mar del Plata
Reunión:
Congreso; VIII Congreso de la Sociedad Argentina de Microbiología General; 2012
Institución organizadora:
SAMIGE
Resumen:
Cadmium,
nickel and lead are relevant metals from a toxicological point of view. People
are exposed to them primarily through food and water. Biosorption, the passive
and energy-independent sorption of molecules onto the surface of an adsorbent
such as inactivated microbial biomass, has shown to be an efficient tool to
remove metals. In this sense, lactic acid bacteria have been already used as
biosorbents (Halttunen et al., 2007, 2008).
The S-layer
is a macromolecular paracrystalline bidimensional array of proteins that
represents the most outer structure covering the cell envelope of several
species of microorganisms, including Lactobacillus kefir. S-layer subunits are generally
assembled in lattices with oblique, square or hexagonal symmetry and it has
been suggested that these cavities may act as appropriate surfaces for
biosorption. For this reason, the aim of this work was to get an insight on the
molecular mechanisms involved in the interaction L. kefir-metal ions and
S-layers-metal ions.
L. kefir
CIDCA 8348 and L. kefir JCM 5818 were cultured in de MRS broth [De Man, J.O. et
al, 1960] for 48 h at 30 oC (stationary phase). One millilitre of cultures was
harvested, washed and resuspended into 1 ml milli Q water containing Pb+2 [from
Pb(NO3)2], Cd+2 [from Cd(NO3)2] or Ni+2 [from Ni(NO3)2.6H2O] ranging from 0 to
0.9 mM. The suspensions were further incubated for 1 h at 30oC (pH 5.5) and then
centrifuged. The pellets were kept to register the Raman spectra and the
supernatants were used for the analytical determinations of Pb+2, Cd+2 and
Ni+2. The S-layers from both L.kefir were extracted and purified as described
Mobili, P. et al, 2009. The pure S-layers were suspended in 1 ml milli Q water
containing 0.3 mM Pb(NO3)2, Cd(NO3)2 or Ni(NO3)2.6H2O and used for the FTIR
determinations.
The
efficiency in the removal following the pattern: Pb+2 > Cd+2 > Ni+2 in
both strains. The Raman spectra differences observed show modifications of both
symmetric and asymmetric carboxylate frequency bands indicate that
bacteria⁄metal interaction occurs through carboxylate groups. The metal/S-layer
protein interaction, analyzed using FTIR spectroscopy, occurs mainly through
the carboxylate groups of the side chains of Asp and Glut residues, with some
contribution of the NH groups of the peptide backbone. The frequency separation
between the symmetric and asymmetric carboxylates vibrations in the spectra of
the S-layers in presence of the metal ions was found to be ca. 190 cm-1 for
S-layer CIDCA 8348 and ca. 170 cm-1 for JCM 5818, denoting an unidentate
coordination in both cases (Gerbino, E. et al, 2011, 2012).
L. kefir CIDCA 8348 and JCM 5818 bind heavy
metals in an efficient way. This analysis allowed obtaining a deeper insight on
the molecular interactions involved when heavy metals are attached to the
bacterial surface.