Time-resolved fluorescence of tryptophan characterizes membrane perturbation by cyclic lipopeptides

Viscosin is a membrane-permeabilizing, cyclic lipopeptide (CLiP) produced by Pseudomonas species. Here, we have studied four synthetic analogs (L1W, V4W, L5W, and L7W), each with one leucine (Leu; L) or valine residue exchanged for tryptophan (Trp; W) by means of time-resolved fluorescence spectroscopy of Trp. To this end, we recorded the average fluorescence lifetime, rotational correlation time and limiting anisotropy, dipolar relaxation time and limiting extent of relaxation, rate constant of acrylamide quenching, effect of H2O-D2O exchange, and time-resolved half-width of the spectrum in the absence and presence of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) liposomes. Structure, localization, and hydration of the peptides were described by molecular dynamics simulations. The combination of the parameters provides a good description of the molecular environments of the Trp positions and the behavior of viscosin as a whole. Of particular value for characterizing the impact of viscosin on the membrane is the dipolar relaxation of Trp4 in V4W, which is deeply embedded in the hydrophobic core. The limiting relaxation level represents the membrane perturbation-unlike typical membrane probes-at the site of the perturbant. Fractions of Trp4 relax at different rates; the one not in contact with water upon excitation relaxes via recruitment of a water molecule on the 10-ns timescale. This rate is sensitive to the concerted membrane perturbation by more than one lipopeptide, which appears at high lipopeptide concentration and is assumed a prerequisite for the final formation of a membrane-permeabilizing defect. Trp7 relaxes primarily with respect to neighboring Ser residues. Trp5 flips between a membrane-inserted and surface-exposed orientation.

Lipopeptides development in cosmetics and pharmaceutical applications: A comprehensive review

Lipopeptides are surface active, natural products of bacteria, fungi and green-blue algae origin, having diverse structures and functionalities. In analogy, a number of chemical synthesis techniques generated new designer lipopeptides with desirable features and functions. Lipopetides are self-assembly guided, supramolecular compounds which have the capacity of high-density presentation of the functional epitopes at the surface of the nanostructures. This feature contributes to their successful application in several industry sectors, including food, feed, personal care, and pharmaceutics. In this comprehensive review, the novel class of ribosomally synthesized lipopeptides is introduced alongside the more commonly occuring non-ribosomal lipopeptides. We highlight key representatives of the most researched as well as recently described lipopeptide families, with emphasis on structural features, self-assembly and associated functions. The common biological, chemical and hybrid production routes of lipopeptides, including prominent analogues and derivatives are also discussed. Furthermore, genetic engineering strategies aimed at increasing lipopeptide yields, diversity and biological activity are summarized and exemplified. With respect to application, this work mainly details the potential of lipopeptides in personal care and cosmetics industry as cleansing agents, moisturizer, anti-aging/anti-wrinkling, skin whitening and preservative agents as well as the pharmaceutical industry as anitimicrobial agents, vaccines, immunotherapy, and cancer drugs. Given that this review addresses human applications, we conclude on the topic of safety of lipopeptide formulations and their sustainable production.

In vitro nematicidal and acaricidal effect of biosurfactants produced by Bacillus against the root-knot nematode Nacobbus aberrans and the dust mite Tyrophagus putrescentiae

In the present study, the nematicidal and acaricidal activity of three biosurfactants (BS) produced by strains of the Bacillus genus was evaluated. The BS produced by the Bacillus ROSS2 strain presented a mortality of 39.29% in juveniles (J2) of Nacobbus aberrans at a concentration of 30 mg/mL, this same strain is the one that presented the highest mortality in Tyrophagus putrescentiae, which was 57.97% at a concentration of 39 mg/mL. The BS were qualitatively identified by thin layer chromatography and are lipid in nature based on the retention factor (Rf). While the GC-MS analysis identified two main compounds that are 4,7-Methano-1H-indene-2,6-dicarboxylic acid, 3a,4,7,7a-tetrahydro-1, and Methyl 4-(pyrrol-1-yl)-1,2,5-oxadiazole-3-carboxylate1, which is the polar part indicated by the presence of dicarboxylic acid and carboxylate groups; while the non-polar portion can be interpreted as a hydrocarbon chain of variable length. Based on the present results, BS can be an alternative for the biocontrol of the root-knot nematode N. aberrans and the mite T. putrescentiae.

Potential for Biological Control of Pythium schmitthenneri Root Rot Disease of Olive Trees (Olea europaea L.) by Antagonistic Bacteria

Several diseases affect the productivity of olive trees, including root rot disease caused by Pythium genera. Chemical fungicides, which are often used to manage this disease, have harmful side effects on humans as well as environmental components. Biological management is a promising control approach that has shown its great potential as an efficient eco-friendly alternative to treating root rot diseases. In the present study, the antagonistic activity of ten bacterial isolates was tested both in vitro and in planta against Pythium schmitthenneri, the causal agent of olive root rot disease. These bacterial isolates belonging to the genera Alcaligenes, Pantoea, Bacillus, Sphingobacterium, and Stenotrophomonas were chosen for their potential antimicrobial effects against many pathogens. Results of the in vitro confrontation bioassay revealed a high reduction of mycelial growth exceeding 80%. The antifungal effect of the volatile organic compounds (VOCs) was observed for all the isolates, with mycelial inhibition rates ranging from 28.37 to 70.32%. Likewise, the bacterial cell-free filtrates showed important inhibition of the mycelial growth of the pathogen. Overall, their efficacy was substantially affected by the nature of the bacterial strains and their modes of action. A greenhouse test was then carried out to validate the in vitro results. Interestingly, two bacterial isolates, Alcaligenes faecalis ACBC1 and Bacillus amyloliquefaciens SF14, were the most successful in managing the disease. Our findings suggested that these two antagonistic bacterial isolates have promising potential as biocontrol agents of olive root rot disease.