S-LAYER PROTEIN PROTECTION TO OSMOTIC STRESS IN Lactobacillus acidophilus

OJEDA PAULA; PRADO ACOSTA MARIANO; PALOMINO MARÍA MERCEDES; RUZAL SANDRA M.

San Miguel de Tucuman

Congreso; VII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE DEL BICENTENARIO; 2011

Sociedad Argentina de Microbiología General

The Surface layer (S-layer) proteins are arrays of a single protein that constitute the outermost cell envelope in several Bacteria and Archaea. They have been considered to function as protective coats, maintenance of cell shape, be involved in adhesion and recently showed an antibacterial endopeptidase activity. Although many studies focus on the structure of the Slayer, their biological functions remains poorly understood. Lactobacillus acidophilus is one of the major species found in human intestines and some strains are believed to have probiotic characteristics. Probiotics are live microorganisms, usually contained in food, traditionally regarded as safe for human consume that, when ingested in sufficient number, play an important role in control of the host intestinal microbiota and in the modulation of the host immune response. Lactobacillus acidophilus possess an S-layer protein of approximately 45 KDa and a pI of 10.4 showing them as highly basic. This microorganism is extremely used in food industry, during which they suffer different stresses. This is why these bacteria have adopted mechanisms that enable them to cope with the challenges of changing environmental conditions, such as osmotic, acidic and other kinds of stress. In this study we proved the S-layer protein is essential in the adaptation of the Lactobacillus during several kinds of stresses. In particular we analyzed the role of the S-layer by exposing cells to high salt conditions. We found an over expression of both the protein and the mRNA, in hiperosmotic condition that were demonstrate by Western blot and quantitative real time PCR. We also tested the growth aptitude of Lactobacillus acidophilus in high osmotic conditions. Cells with S-layer protein and cells treated with LiCl 6M, that remove completely the S-layer from the cell wall, were grown in different NaCl concentrations, their growth were follow by optical density and viable cell count. The differences in the both growth curves show the importance of the Slayer protein in the adaptation to this kind of stress. We are currently studying the importance of this protein for other stress adaptations.