Inhibitory Substances Produced by NativeLactobacillus plantarumUTNCys5-4 Control Microbial Population Growth in Meat

Abstract

Microbial contamination is the cause of extensive economic loss in the food sector. Previously, the wide-range antimicrobial capacity of inhibitory substances secreted by the Lactobacillus plantarum UTNCys5-4 strain was demonstrated in vitro; however, its mechanism of action in the food matrix remains unclear. This study was aimed to evaluate the effect of antimicrobials produced by the Cys5-4 strain in raw meat applied as pure cell cultures, cell-free supernatant (CFS), and partially purified peptides. The bacteriological results indicated the presence of commensal microbes exhibiting resistance to several antibiotics in meat samples purchased from the local market. Dipping solutions containing antimicrobial substances produced by Cys5-4 resulted in a decrease by 1.91, 1.69, and 1.55 log10 in cell counts upon addition of CFS, peptides and respectively pure cell culture in raw meat at day 9 of storage with refrigeration. The microbial population was maintained in the untreated meat samples during storage. An increase in pH and a concentration of released ammonia was detected in nontreated meat, indicating protein degradation. The Cys5-4 peptides exerted their bacteriolytic mode of action inducing damage in the cell membrane of the target bacteria, allowing the leaching of DNA/RNA content. The results indicate that coating meat with CFS containing Cys5-4 is a promising approach to protect against further contamination by microorganism spoilage, as well as an alternative for increasing the shelf life of raw meat.

Next-Generation Sequencing for Whole-Genome Characterization of Weissella cibaria UTNGt21O Strain Originated From Wild Solanum quitoense Lam. Fruits: An Atlas of Metabolites With Biotechnological Significance

“…No DNA/RNA was detected in untreated control samples. This result was in agreement with our previous findings that some peptides disrupt the cell membrane of the target Gram-negative bacteria and their effectiveness was target specific ( Tenea and Guana, 2019 ). Recent work on the synthetic peptide melamine mode of action against S. aureus indicates that the peptide interacted with the target cell membrane inducing membrane depolarization and leakage of ATP and DNA/RNA molecules followed by cell death, whereas another protein Mel4 does not induce cell membrane disruption inducing cell killing by autolysis mechanism ( Yasir et al, 2019 ).…”

Peptide Extracts from Native Lactic Acid Bacteria Generate Ghost Cells and Spheroplasts upon Interaction with Salmonella enterica, as Promising Food Antimicrobials

“…No ghost cells were detected, indicating that the morphological and ultrastructural changes may rely not only on the concentration and exposure time but also on the identity (origin) of the antimicrobial agent. This mechanism might be explained by the differences in the peptide mixture produced by the Gt2 and Cys5-4 strains; Gt2 has four products of approximately 22, 32, 35, and 55 kDa, while Cys5-4 produces peptides of 10, 15, 20, and 30 kDa [ 15 , 16 ]. However, more than one peptide or protein-like agent is responsible for the overall antimicrobial activity.…”

“…Early research indicated that the treatment of Salmonella enterica ATCC51741 at both the vegetative and exponential phases of growth with the cell-free supernatant of Gt28 resulted in complete inactivation upon 3 h, suggesting its bactericidal mode of action [ 14 ]. Contrary to Gt2 and Cys5-4 peptide extracts containing a mixture of low- and larger weight peptides [ 15 , 16 ], peptide extract from Gt28 contained one peptide of 15 kDa and some extra larger peptides or protein-like products as deducted in SDS-PAGE, but further analysis is required to detect the extract composition (Figure S2 ). The cell membrane showed interrupted stretches, and electron-dense material accumulated in the periplasmic space ( Figure 6 ).…”

Bioprospecting Antimicrobials from Lactiplantibacillus plantarum: Key Factors Underlying Its Probiotic Action

“…Tenea and co-workers investigated the mechanism by which Gt2 peptides and Cys5-4 peptides, from L. plantarum UTNGt2 and UTNCys5-4, respectively, target Gram-negative bacteria ( Table 1 ). Gt2 and Cys5-4 peptides comprise, in turn, two or more post-translationally modified peptides forming one aggregate forming one functional inhibitory unit, which altered the cellular membrane permeability of E. coli and Salmonella , causing the leakage of cytoplasmic contents, followed by cellular death [ 50 , 51 ]. In a later study, the same authors investigated deeply the changes in Salmonella cells treated with Gt2 and Cys5-4 extracts, highlighting the occurrence of direct interaction between Salmonella genomic DNA and the peptides [ 46 ].…”

“…Plantaricins (especially Q7 [ 121 ], NC8 [ 122 ], Gt2 peptides and Cys5-4 peptide [ 46 , 51 ], IIA-1A5 [ 123 ], KL-1Y [ 58 ], ZJ316 [ 124 ], plantaricin 3, 5 [ 48 ]) are very active against Salmonella spp., a Gram-negative bacterium including pathotypes such as Salmonella enterica subspecies ( S. enteritidis ) and Salmonella enterica serotypes ( S. typhimurium ) ( Table 1 ). Both can cause severe illnesses, ranging from gastroenteritis to typhoid (Typhi) and paratyphoid fever (Paratyphi), a global problem with more than 27 million cases worldwide each year [ 125 , 126 ].…”