Lactobacilli isolated from kefir grains: evidence of the presence of S-layer proteins

Abstract

In the present study we report for the first time the presence of S-layer proteins in Lactobacillus kefir and Lactobacillus parakefir isolated from kefir grains. Soluble whole-cell protein profile obtained either by mechanical disruption (X-press) or by a combined treatment with lysozyme and SDS on whole cells, showed a significant band of apparent molecular mass of 66–71 kDa as measured by SDS–PAGE. The intensity of this band was considerably reduced when cells were treated with 5 M-LiCl. The above mentioned proteins were recovered in the LiCl extracts. After dialysis and concentration, the proteins extracted were able to reassemble in a regular array. Negative staining of these protein preparations were analysed by transmission electron microscopy and a paracrystalline arrangement was seen. Thin sections of bacteria analysed by transmission electron micrographs showed an outermost layer over the bacterial cell wall, that was lost after the LiCl treatment. The production of this surface structure under different culture conditions was also evaluated. Finally, the relationship between the presence of S-layer proteins and surface properties (e.g. adhesion to Caco-2 cells, autoaggregation, and hemagglutination) was investigated.

Effect of Environmental Stresses on S-Layer Production in Lactobacillus acidophilus ATCC 4356

“…Several reports have appeared in which functions of S-layer are described or assumed (Boot et al, 1993;Jakava-Viljanen et al, 2002;Sara & Sleytr, 2000). However, no general function has been identified for S-layer proteins, but several lactobacillar S-layers have been identified as putative adhesions with affinity for intestinal epithelial cells, extracellular matrices and/ or to lipoteichoic acid (LTA) of other bacterial species (Avall-Jaaskelainen & Palva, 2005;Buck et al, 2005;Frece et al, 2005;Garrote et al, 2004;Hynonen et al, 2002;Kos et al, 2003;Velez et al, 2007;Vidgren et al, 1992). Of the various roles proposed for the bacterial S-layer, it is a protective sheath against hostile environment (Avall-Jaaskelainen & Palva, 2005;Frece et al, 2005;Khaleghi et al, 2010Khaleghi et al, , 2011Kos et al, 2003;Schar-Zammaretti et al, 2005).…”

Characterization of S-layer proteins of Lactobacillus by FTIR spectroscopy and differential scanning calorimetry

“…aggregation and co-aggregation ability), in the S-layer protein molecular mass [8], glycosylation and pattern of recognition by antibodies [28] (Table 1).…”

“…FTIR spectra of the solid proteins in KBr pellets (ratio 1 mg protein/100 mg KBr), in the 4000-500 cm À1 range, were recorded in transmission mode in a system continuously purged under dry [1,8]. b Reactivity with rabbit antisera anti-S-layer protein from L. kefir CIDCA 8321 (a21) or L. brevis ATCC 8287 (a87) [28].…”

“…The presence of S-layer proteins in Lactobacillus kefir and Lactobacillus parakefir isolated from kefir grains has been reported for the first time in the last years [8].…”

Mechanism of Algal Aggregation by Bacillus sp. Strain RP1137

“…While proteinase K can cleave surface proteins (21), it may not cleave proteins that do not have an exposed cleavage site. S-layer proteins are often involved in adhesion of Gram-positive bacteria to either biotic or abiotic surfaces and can be involved in aggregation (22). S-layer proteins are also typically attached to peptidoglycan via electrostatic interactions and can be removed by LiCl treatment (20).…”