Exploring antiadherent chemical signals in Lactobacillus paracasei strain

ORPHEE, CECILIA; VERNI, MARÍA CECILIA; GONZALEZ, SILVIA NELINA; CARTAGENA, ELENA

San Miguel de Tucumán

Simposio; V SIBAL; 2016

CERELA CCT CONICET NOA Sur

Lactobacilli, as bacterial symbionts that constitute human microbiome, are considered as potential interfering bacteria due to their ability to produce various antimicrobial agents such as organic acids, hydrogen peroxide, carbon peroxide, diacetyl, low molecular weight antimicrobial substances, bacteriocins, and adhesion inhibitors. They have antimicrobial activity and can interfere with pathogen adhesion on epithelial cells of urogenital and intestinal tracts, as well as on catheter devices, prostheses, and different solid surfaces. Microbial bioemulsifiers are environmentally friendly, biodegradable, less toxic and non-hazardous than synthetic counterparts displaying an important role in regulating the attachment-detachment of microorganisms to and from surfaces. Bioemulsifiers are involved in cell-to-cell interactions such as quorum sensing and biofilm formation, maintenance and maturation. Lactobacillus paracasei sp. paracasei produce glycoproteinaceus substances named surlactin as bioemulsifiers. Herein, a rapid chemical and UV spectroscopy method (pre and post hydrolysis) for the determination of glycoproteins of L. paracasei ssp. paracasei IBF1 supernatants were carried out. In addition, a small concentration of L-ascorbic acid (12.5 µg/mL) incorporated into culture medium and incubated for 1 and 5 days at 37°C was also evaluated in relation to the interfacial activity. L-ascorbic acid (AA), metabolite widely distributed in plants, fungi, bacteria and algae, notably increased the interfacial activity of the Lactobacillus culture. Oil spreading technique allowed us to measure an increment of 82% with respect to the L. paracasei supernatant employed as control then of 24 h-exposure. In concordance, the emulsification activity was higher than control for the supernatants obtained from a five-day-culture of L. paracasei supplemented with AA (50% emulsification activity, identical to that of Tween 80). It is important to note that AA was fully metabolized by whole bacterial cells, because it was missing in the chromatographic profiling of the L. paracasei supernatant. Hence, this increase would be due to stimulation of the surface active substance biosynthesis. Extracts from both stimulated and control supernatants revealed red spots with ninhydrin 2% reagent. In addition, the presence of protein substances was corroborated by a specific protein detecting kit, while carbohydrates were characterized by the Molisch reaction and by UV absorption at 323 nm that demonstrated the presence of carbohydrates (post hydrolysis). These extracts from supernatants were also processed and the UV absorptions (pre-hydrolysis) due to possible interferences. Stimulated supernatants exerted antiadherent-antibiofilm activity at 1 h of exposure against Gram (+) and (-) biofilm used as targets. The obtained results constitute important findings with biopharmaceutical interest that lead us to propose to L. paracasei sp. paracasei IBF1 as an anti-pathogenic strain.