title: Influence of osmotic stress on the profile and gene expression of surface layer proteins in Lactobacillus acidophilus ATCC 4356.
abstract: In this work, we studied the role of surface layer (S-layer) proteins in the adaptation of Lactobacillus acidophilus ATCC 4356 to the osmotic stress generated by high salt. The amounts of the predominant and the auxiliary S-layer proteins SlpA and SlpX were strongly influenced by the growth phase and high-salt conditions (0.6 M NaCl). Changes in gene expression were also observed as the mRNAs of the slpA and slpX genes increased related to the growth phase and presence of high salt. A growth stage-dependent modification on the S-layer protein profile in response to NaCl was observed: while in control conditions, the auxiliary SlpX protein represented less than 10 % of the total S-layer protein, in high-salt conditions, it increased to almost 40 % in the stationary phase. The increase in S-layer protein synthesis in the stress condition could be a consequence of or a way to counteract the fragility of the cell wall, since a decrease in the cell wall thickness and envelope components (peptidoglycan layer and lipoteichoic acid content) was observed in L. acidophilus when compared to a non-S-layer-producing species such as Lactobacillus casei. Also, the stationary phase and growth in high-salt medium resulted in increased release of S-layer proteins to the supernatant medium. Overall, these findings suggest that pre-growth in high-salt conditions would result in an advantage for the probiotic nature of L. acidophilus ATCC 4356 as the increased amount and release of the S-layer might be appropriate for its antimicrobial capacity.
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: María Mercedes
authors.initials: MM
authors.lastname: Palomino
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: Pablo M
authors.initials: PM
authors.lastname: Waehner
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: Joaquina
authors.initials: J
authors.lastname: Fina Martin
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: Paula
authors.initials: P
authors.lastname: Ojeda
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: Lucía
authors.initials: L
authors.lastname: Malone
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: Carmen
authors.initials: C
authors.lastname: Sánchez Rivas
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: Mariano
authors.initials: M
authors.lastname: Prado Acosta
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina.
authors.forename: Mariana C
authors.initials: MC
authors.lastname: Allievi
authors.affiliation: Laboratorio Bacterias Gram Positivas, sus Fagos y Estrés, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-UBA, IQUIBICEN-CONICET, Ciudad Universitaria, Pabellon II, piso 4, Buenos Aires, 1428, Ciudad de Buenos Aires, Argentina. sandra@qb.fcen.uba.ar.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Ruzal
mesh_terms: D015870:Gene Expression; D007779:Lactobacillus acidophilus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009997:Osmotic Pressure; D012965:Sodium Chloride / Q000378:metabolism
chemical_list: D008562:Membrane Glycoproteins; C055764:S-layer proteins; D012965:Sodium Chloride
keywords: Lactobacillus; Osmotic stress; S-layer proteins