Synergistic Effects of the Lactobacillus acidophilus Surface Layer and Nisin on Bacterial Growth

Abstract

We have previously described a murein hydrolase activity for the surface layer (S-layer) of Lactobacillus acidophilus ATCC 4356. Here we show that, in combination with nisin, this S-layer acts synergistically to inhibit the growth of pathogenic Gram-negative Salmonella enterica and potential pathogenic Gram-positive bacteria, Staphylococcus aureus and Bacillus cereus. In addition, bacteriolytic effects were observed for the Gram-positive species tested. 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 murein hydrolase activity.

Membrane-active bacteriocins to control Salmonella in foods

“…Thus, in combination with nisin, S-layer acts synergistically to inhibit the growth of S. Newport (Prado-Acosta, Ruzal, Allievi, Palomino, & Sanchez Rivas, 2010). A similar effect was observed when cooked ham and bologna were coated with gelatin gel containing 25.5 g/l of lysozyme-nisin (1:3) plus 25.5 g/l of EDTA (Gill & Holley, 2000).…”

Murein hydrolase activity of surface layer proteins from Lactobacillus acidophilus against Escherichia coli

“…The SLPs of L. acidophilus ATCC 4356 were reported to have the ability to inhibit the growth of S. enterica serovar Newport, but not that of Staphylococcus aureus or Bacillus cereus when applied alone; however, they acted synergistically with nisin to inhibit the growth of the two latter. It was therefore postulated that SLPs enhance the access of nisin into the cell membrane by enabling its transport through the cell wall, while nisin provides ion-nonspecific dissipation of the proton motive force that contributes to the murein hydrolase activity of SLPs [13].…”

“…The SLPs of L. acidophilus ATCC 4356 that were extracted by lithium chloride were able to hydrolyse the cell wall peptidoglycan of Escherichia coli, Micrococcus luteus and Salmonella enterica serovar Newport [12], thereby inhibiting the growth of pathogens and acting synergistically with nisin to reduce the levels of gramnegative and gram-positive bacteria [13]. Previous studies had reported that a pulsed electric field (PEF) could change the peptidoglycan layer of E. coli and expose the plasma membrane, but the intracellular enzyme and cellular metabolic activities remained active, indicating sublethal injury [14].…”

Bacteriocins and their position in the next wave of conventional antibiotics

“…At high quantities, this process can be divided into two stages, with the first being bacteriostatic and the second bactericidal [3,33,38]. Nisin has also been found to act as a lytic agent [39].…”