title: 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.
authors.affiliation: Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA), 47 y 116 (1900), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina.
authors.forename: Graciela Liliana
authors.initials: GL
authors.lastname: Garrote
authors.forename: Lucrecia
authors.initials: L
authors.lastname: Delfederico
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Bibiloni
authors.forename: Analia Graciela
authors.initials: AG
authors.lastname: Abraham
authors.forename: Pablo Fernando
authors.initials: PF
authors.lastname: Pérez
authors.forename: Liliana
authors.initials: L
authors.lastname: Semorile
authors.forename: Graciela Liliana
authors.initials: GL
authors.lastname: De Antoni
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis*; D002473:Cell Wall / Q000737:chemistry / Q000187:drug effects; D043302:Cultured Milk Products / Q000382:microbiology*; D005285:Fermentation; D007778:Lactobacillus / Q000737:chemistry* / Q000302:isolation & purification*; D018021:Lithium Chloride / Q000494:pharmacology; D008854:Microscopy, Electron; D008970:Molecular Weight; D009113:Muramidase / Q000494:pharmacology; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D012967:Sodium Dodecyl Sulfate; D009113:Muramidase; D018021:Lithium Chloride