Background Essential oils and antimicrobial peptides are two well-known safe and natural products that have been considered as alternatives to antibiotics. In the present study, the antibacterial activity of four plant essential oils and one lactoferrin-derived peptide was investigated. Results The chemical profile of each essential oil was determined by GC and GC–MS. Antimicrobial activity was shown against seven clinically isolated veterinary pathogens. MIC and MBC assessment of the essential oils and cLFchimera exhibited different antibacterial properties (MIC from a range of 62.5 to 500 µg/mL and 3.5 to 39.0 µg/mL for essential oils and cLFchimera, respectively). Compared to the essential oils, cLFchimera showed more significant antibacterial activity. Among the essential oils, Vitex agnus-castus and Salvia officinalis showed relatively better antibacterial activity. Conclusions The in vitro results reported here suggested that, for animals suffering from these pathogens, cLFchimera and the essential oils particularly Vitex agnus-castus could be considered as potential antimicrobial agents.

Lactoferrin is the most dominant protein in milk after casein. This protein plays a crucial role in many biological processes including the regulation of iron metabolism, induction and modulation of the immune system, the primary defense against microorganisms, inhibiting lipid peroxidation and presenting antimicrobial activity against various pathogens such as parasites, fungi, bacteria, and viruses. The major antimicrobial effect of lactoferrin is related to its N-terminal tail where different peptides for instance lactoferricin and lactoferrampin which are important for their antimicrobial abilities are present. The growth rate of bacterial cells in camel milk is lower than that of the cow milk due to having more antimicrobial compounds. In this study, we have fused a codon-optimized partial camel lactoferrcin and lactoferrampin DNA sequences in order to construct a fused peptide via a lysine. This chimeric 42-mer peptide consists of complete and partial amino acid sequence of camel lactoferrampin and lactoferricin, respectively. Human embryonic kidney 293 (HEK-293) cells were used for synthesizing this recombinant peptide. Finally, the antibacterial activities of this constructed peptide were investigated under in vitro condition. The result showed that, all construction, cloning and expression processes were successfully performed in HEK-293. One His-tag tail was added to the chimera in order to optimize the isolation and purification processes and also reduce the cost of production. Additionally, His-tag retained the antimicrobial activity of the chimera. The antimicrobial tests showed that the growth rate in the majority of bacterial plant pathogens, including gram negative and positive bacteria, was inhibited by recombinant chimera as the level of MIC values were evaluated between 0.39 and 25.07 μg/ml for different bacterial isolates.

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Background: Foodborne pathogens and their biofilms are considered as one of the most serious problems in human health and food industry. Moreover, safety of foods is a main global concern because of the increasing use of chemical food additives. Ensuring food safety enhances interest in discovery of new alternative compounds such as antimicrobial peptides (AMPs), which can be used as bio-preservatives in the food industry. In this study, the most important antimicrobial peptides of camel milk lactoferrin (lactoferrampin and lactoferricin) were recombinantly expressed in the form of chimeric peptide (cLFchimera) in a food-grade L. lactis strain. P170 expression system was used to express secreted cLFchimera using pAMJ1653 expression vector which harbors a safe (non-antibiotic) selectable marker. Results: Peptide purification was carried out using Ni-NTA agarose column from culture medium with concentration of 0.13 mg/mL. The results of disk diffusion test revealed that cLFchimera had considerable antimicrobial activity against a number of major foodborne bacteria. Furthermore, this chimeric peptide showed strong and weak inhibitory effect on biofilm formation against P. aeruginosa, S. aureus E. faecalis, and E. coli, respectively. Antioxidant activity and thermal stability of the chimeric peptide was determined. The results showed that cLFchimera had antioxidant activity (IC 50 : 310 μ/mL) and its activity was not affected after 40 min of boiling. Finally, we evaluated the interaction of the peptide with LPS and DNA in bacteria using molecular dynamic simulation as two main intra and extra cellular targets for AMPs, respectively. Our in silico analysis showed that cLFchimera had strong affinity to both of these targets by positive charged residues after 50 ns molecular dynamic simulation. Conclusions: Overall, the engineered food-grade L. lactis generated in the present study successfully expressed a secreted chimeric peptide with antimicrobial properties and could be considered as a promising bio-preservative in the food industry.

Background: Thanatin is the smallest member of Beta-hairpin class of cationic peptide derived from insects with vast activities against various pathogens. Objective: n this study, the antimicrobial activity of this peptide against some species of human bacterial pathogens as well as its toxicity on NIH cells were evaluated. Method: Thanatin DNA sequence was cloned into pcDNA3.1+ vector and transformed into a DH5α bacterial strain. Then the recombinant plasmids were transfected into HEK-293 cells by calcium phosphate co-precipitation. After applying antibiotic treatment, the supernatant medium containing thanatin was collected. The peptide quantity was estimated by SDS-PAGE and GelQuant software. The antimicrobial activity of this peptide was performed with Minimum Inhibitory Concentration (MIC) method. In addition, its toxicity on NIH cells were evaluated by MTT assay. Results: The peptide quantity was estimated approximately 164.21 µmolL-1. The antibacterial activity of thanatin was estimated between 0.99 and 31.58 µmolL-1 using MIC method. The result of cytotoxicity test on NIH cell line showed that the peptide toxicity up to the concentration of 394.10 µmolL-1 and for 48 hours, was not statistically significant from negative control cells (P>0.05). The antimicrobial assay demonstrated that thanatin had an antibacterial effect on some tested microorganisms. The results obtained in this study also showed that thanatin had no toxicity on mammalian cell lines including HEK293 and NIH. Conclusion: Antimicrobial peptides such as thanatin are considered to be appropriate alternatives to conventional antibiotics in treating various human pathological diseases bacteria.

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Synergistic effects of metallic nanoparticles (NPs) with commonly used antibiotics have encouraged the exploration of novel biological entities, including bacteria and weed plants. The present study for the first time reports the capability of an extracellular fraction of Bacillus sp. isolated from effluents of a glass‐manufacturing unit to biosynthesis silver nanoparticles (AgNPs) without hazardous materials. Besides, the biosynthesis of AgNPs using an aqueous extract of herbaceous weed plant (Amaranthus sp.), as a low‐cost natural source, has been addressed in this study. Our findings confirmed the fabrication of microbial and plant‐sourced AgNPs, being thoroughly characterized by UV–vis, transmission electron microscopy, X‐ray diffraction, dynamic light scattering, energy dispersive X‐ray spectroscopy, and zeta potential measurements. Further, biological activities of the plant‐ and bacterium‐derived AgNPs were investigated against several pathogenic bacteria, in combination with streptomycin. The antibacterial effectiveness of the antibiotic coated with 400 µg/disk of AgNPs increased over 50% toward all the pathogenic bacteria. The data presented here demonstrate that both industrial wastewater‐adapted Bacillus sp. and wild‐growing Amaranthus sp. are efficient natural sources with excellent capabilities for creating biologically active AgNPs, which would be of considerable interest for circumventing bacterial resistance to current antibiotics.