NEW APPLICATION OF A MUREIN HYDROLASE ACTIVITY OF THE S-LAYER OF LACTOBACILLUS ACIDOPHILUS

MARIANO PRADO ACOSTA; MARÍA MERCEDES PALOMINO; MARIANA CLAUDIA ALLIEVI; CARMEN SÁNCHEZ RIVAS; SANDRA M RUZAL

San Miguel de Tucumán

Simposio; III Simposio Internacional de Bacterias Lácticas. II Encuentro Red BAL. 2009; 2009

CERELA-CONICET

We have described a new enzymatic functionality for the S-layer of Lactobacillus acidophilus ATCC 4356, namely murein hydrolase activity, assayed via zymograms against the cell wall  of Salmonella enterica and identified by Western Blot. Based on amino-acid sequence comparisons, the hydrolase activity was predicted to be located at the C-terminus. Subsequent cloning and expression in Bacillus subtilis of the C-terminal domain resulted in the functional verification of the enzymatic activity. We have also found that, in combination with Nisin, this S-layer acts synergistically to inhibit the growth of potential pathogenic Gram negative and Gram positive bacteria such as Salmonella enterica, Staphylococcus aureus and Bacillus cereus. Bacteriolytic effects of the synergetic duo were observed for Gram positive species. We postulate that the S-layer enhances the access of Nisin into the cell membrane by enabling it to cross the cell wall; while Nisin provides the sudden ion-nonspecific dissipation of the proton motive force required to enhance the S-layer endopeptidase activity. The S-layer-Nisin synergetic duo seems to be a promising new antibacterial agent, for its application in food industry.