Journal
WORLD JOURNAL OF MICROBIOLOGY & BIOTECHNOLOGY
Volume 30, Issue 11, Pages 2829-2837Publisher
SPRINGER
DOI: 10.1007/s11274-014-1708-y
Keywords
Plantaricin; Gram-negative bacteria; Cell viability; Outer membrane; Flow cytometry
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Funding
- University Grant Commision (SAP)
- Department of Science and Technology (FIST), Govt. of India in Department of Genetics, UDSC
- Department of Biotechnology
- Council of Scientific and Industrial Research (CSIR), Government of India
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Plantaricins are small bioactive peptides produced by Lactobacillus plantarum strains that exhibit significant antimicrobial activity against closely-related Gram-positive bacteria, including food spoilage organisms. In comparison, bacteriocins including plantaricins, are usually less effective against Gram-negative organisms. In this study, we demonstrate that heterologously expressed and purified plantaricins, Pln E, -F, -J, and -K when tested against Gram negative model organism Escherichia coli K-12 were highly effective under certain conditions. The apparent tolerance of Gram-negative members to these peptides has been explained on the basis of the presence of the outer membrane (OM) that acts as a protective barrier. We have shown that agents and/or conditions that destabilize OM of E. coli K-12, make it susceptible to plantaricin peptides. In order to further strengthen this conclusion, an OM lipoprotein-defective lpp mutant strain of E. coli K-12 was also studied and compared. A significant loss of cell viability both in terms of CFU/ml as well as with live-dead dual staining combined with flow cytometry, could be demonstrated with the lpp mutant in comparison to the wild type strain. The results indicate that plantaricins can inhibit Gram-negative bacteria if the outer-membrane is weakened and it can be used in preservation of food with the help of some food-grade chelating agents.
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