Modifications of the Lactobacillus acidophilus S-Layer protein in osmetic stress

OJEDA PAULA; ALLIEVI MARIANA C; PALOMINO MARÍA MERCEDES; SANCHEZ RIVAS CARMEN; RUZAL SANDRA M.

Mar del Plata

Congreso; VIII Congreso de Microbiología General "SAMIGE"; 2012

Sociedad Argentina de Microbiología General SAMIGE

Modifications of the Lactobacillus acidophilus S-layer protein in osmotic stress Ojeda Paula V., Allievi Mariana C. Palomino M. Mercedes, Sánchez Rivas Carmen and Ruzal Sandra M. Dto.Química Biológica, Fac. Cs. Exactas y Naturales UBA Lactobacillus acidophilus is one of the major species found in human intestines recognized as safe (GRAS) with some strains having probiotic characteristics. Probiotics are live microorganisms, usually contained in food, that play an important role in control of the host intestinal microbiota and in the modulation of the host immune response. The strain L. acidophilus ATCC4356 has been described as probiotic and posses a 45kDa Surface layer (S-layer) protein.This is a highly basic protein with a pI of 9.59 and we have previously established its antibacterial and antiviral activities.These bacteria suffers different stresses, such as osmotic, acidic and surfactant when ingested since it is challenged to the environmental changing conditions. In a previous study we proved the S-layer protein to be essential in the adaptation of the L. acidophilus to several kinds of stresses. In this study we deal in depth with the changes in the cell envelope due to external high salt conditions. Cells were grown in different NaCl concentrations and their S-layer protein were extracted and analyzed by Western blot. We found two types of S-layers in hiperosmotic condition that differed in their molecular weight while in control condition there is only one type protein. The hydrophobicity characteristics of the envelope of L. acidophilus varied with the osmolarity of the growth medium as shown by measuring their partition coeffcient in n-octane/water The modifications in size, concentration, location (fixed to cell wall or free in the supernatant) are related to the growing stages and stress conditions (high NaCl concentrations) indicating posttranslational or transcriptional modifications. The lack of aggregation capacity of cultures and absence of staining of their S-layers with glycosilation detection techniques suggested the absence of posttranslational glycosylation. Northern blot analysis was evaluated to determine the use of different promoters. The differences obtained in the S-layer between cells grown with and without NaCl show the importance of the S-layer protein in the adaptation to this stress.