Nanoencapsulated Lippia rotundifolia antimicrobial peptide: synthesis, characterization, antimicrobial activity, and cytotoxicity evaluations.

Antimicrobial peptides (AMP) are promising novel antibiotics but exhibit low stability and can be toxic. The AMP encapsulation can be used to protect the drug and control its release rates. The Lr-AMP1f encapsulated into chitosan nanoparticle (NP) by ionic gelation method reached 90% efficiency. The results indicated that the hydrodynamic particle size of NPs increased from 196.1 ± 3.14 nm (free NP) to 228.1 ± 12.22 nm (nanoencapsulated Lr-AMP1f), while the atomic force microscope showed the spherical shape. The Zeta potential of the nanoencapsulated Lr-AMP1f was high (+ 35 mV). These AMP-loaded NPs exhibited stability for up to 21 days of storage. The minimum inhibitory concentration (MIC) of free Lr-AMP1f was 8 µg/mL for E. coli and S. epidermidis. However, the nanoencapsulated Lr-AMP1f produced a bacteriostatic effect against both bacteria at 8 µg/mL. The MIC of nanoencapsulated Lr-AMP1f was 16 µg/mL for E. coli and 32 for S. epidermidis. Nanoencapsulated Lr-AMP1f was nontoxic to HEK293 cells. Promisingly, chitosan NP can be used as a vehicle for the antibacterial application of new AMP (Lr-AMP1f).

Strategies and molecular tools to fight antimicrobial resistance: resistome, transcriptome, and antimicrobial peptides.

The increasing number of antibiotic resistant bacteria motivates prospective research toward discovery of new antimicrobial active substances. There are, however, controversies concerning the cost-effectiveness of such research with regards to the description of new substances with novel cellular interactions, or description of new uses of existing substances to overcome resistance. Although examination of bacteria isolated from remote locations with limited exposure to humans has revealed an absence of antibiotic resistance genes, it is accepted that these genes were both abundant and diverse in ancient living organisms, as detected in DNA recovered from Pleistocene deposits (30,000 years ago). Indeed, even before the first clinical use of antibiotics more than 60 years ago, resistant organisms had been isolated. Bacteria can exhibit different strategies for resistance against antibiotics. New genetic information may lead to the modification of protein structure affecting the antibiotic carriage into the cell, enzymatic inactivation of drugs, or even modification of cellular structure interfering in the drug-bacteria interaction. There are still plenty of new genes out there in the environment that can be appropriated by putative pathogenic bacteria to resist antimicrobial agents. On the other hand, there are several natural compounds with antibiotic activity that may be used to oppose them. Antimicrobial peptides (AMPs) are molecules which are wide-spread in all forms of life, from multi-cellular organisms to bacterial cells used to interfere with microbial growth. Several AMPs have been shown to be effective against multi-drug resistant bacteria and have low propensity to resistance development, probably due to their unique mode of action, different from well-known antimicrobial drugs. These substances may interact in different ways with bacterial cell membrane, protein synthesis, protein modulation, and protein folding. The analysis of bacterial transcriptome may contribute to the understanding of microbial strategies under different environmental stresses and allows the understanding of their interaction with novel AMPs.

Identification of botryticidal proteins with similarity to NBS-LRR proteins in rosemary pepper (Lippia sidoides Cham.) flowers.

Heavy agricultural losses are closely related to attacks by insect-pests and phytopathogens such as bacteria and fungi. Among them, the fungus Botrytis cinerea can cause gray mold in more than 200 different species of plants, and is considered a challenging problem for agribusiness. Fungicides are commonly used to control this pathogen because they are fast-working and easy to apply. However, the continuous use of fungicides may promote the selection of resistant fungi and can also cause profound contamination in ecosystems. Aiming to find alternative strategies to solve these problems, several studies have focused on searching for plant proteins and peptides with antifungal activities (AFPs). With this in mind, this report shows the isolation and characterization of two novels antifungal proteins from flowers of rosemary pepper (Lippia sidoides Cham.) with 10 and 15 kDa. Isolation was performed by using an Octyl-Sepharose hydrophobic column. In vitro bioassays indicated that isolated proteins were able to inhibit B. cinerea development, but were not effective against all bacteria tested. Moreover, N-termini sequences indicate that both proteins showed sequence homology with NBS-LRR R proteins with a lower molecular mass, suggesting possible protein fragmentation. Data reported here could help in the development of biotechnological products for crop protection against phytopathogenic fungi in the near future.

Biotechnological potential of antimicrobial peptides from flowers.

Flowers represent a relatively unexplored source of antimicrobial peptides of biotechnological potential. This review focuses on flower-derived defense peptide classes with inhibitory activity towards plant pathogens. Small cationic peptides display diverse activities, including inhibition of digestive enzymes and bacterial and/or fungal inhibition. Considerable research is ongoing in this area, with natural crop plant defense potentially improved through the application of transgenic technologies. In this report, comparisons were made of peptide tertiary structures isolated from diverse flower species. A summary is provided of molecular interactions between flower peptides and pathogens, which include the role of membrane proteins and lipids. Research on these peptides is contributing to our understanding of pathogen resistance mechanisms, which will, given the perspectives for plant genetic modification, contribute long term to plant genetic improvement for increased resistance to diverse pathogens.