Effect of Local Anesthetics on Dipole Potential of Different Phase Membranes: A Fluorescence Study.

The molecular mechanism behind the action of local anesthetics is not well understood. Phenylethanol (PEtOH) is an ingredient of essential oils with a rose-like odor, and it has previously been used as a local anesthetic. In this work, we explored the effect of PEtOH on dipole potential in membranes representing biologically relevant phases, employing the dual-wavelength ratiometric method utilizing the potential-sensitive probe di-8-ANEPPS. Our results show that PEtOH reduces membrane dipole potential in membranes of all biologically relevant phases (gel, liquid-ordered, and fluid) in a concentration-dependent manner. To the best of our knowledge, these results constitute one of the early reports describing reduction of membrane dipole potential induced by local anesthetics, irrespective of membrane phase.

Bacillus sp. and arbuscular mycorrhizal fungi consortia enhance wheat nutrient and yield in the second-year field trial: Superior performance in comparison with chemical fertilizers.

AIMS: The aim of the study is to analyse the effect of microbial consortia for wheat biofortification, growth, yield and soil fertility as part of a 2-year field study and compare it with the use of chemical fertilizers. METHODS AND RESULTS: A field trial (second year) was conducted with various combinations of plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) treatments, ranging from a single inoculant to multiple combinations. The microbial consortia used were Bacillus sp. and AMF based on first-year field trial results. The consortia based on native (CP4) and non-native (AHP3) PGPB (Bacillus sp.) and AMF performed better in terms of nutrients content in wheat grain tissue and yield-related traits compared with chemical fertilizer treated and untreated control. Dual treatment of PGPB (CP4+AHP3) combined with AMF resulted in a significant increase in antioxidants. The spatial colonization of AMF in roots indicated that both the isolates CP4 and AHP3 were able to enhance the AMF colonization in root tissue. Furthermore, soil enzymes' activities were higher with the PGPB and AMF combination giving the best results. A positive correlation was recorded between plant growth, grain yield and soil physicochemical parameters. CONCLUSIONS: Our findings confirm that the combined treatment of CP4 and AHP3 and AMF functions as an effective microbial consortium with excellent application prospects for wheat biofortification, grain yield and soil fertility compared with chemical fertilizers. SIGNIFICANCE AND IMPACT OF STUDY: The extensive application of chemical fertilizers on low-yielding field sites is a severe concern for cereal crops, especially wheat in the Asian continent. This study serves as a primer for implementing site-specific sustainable agricultural-management practices using a green technology leading to significant gains in agriculture.

Bacteria from native soil in combination with arbuscular mycorrhizal fungi augment wheat yield and biofortification.

Plant growth promoting bacteria (PGPB) have been used to enhance crop productivity. The effect of native PGPB and arbuscular mycorrhizal (AM) fungi in combination on wheat yield, biofortification and soil enzymatic activity is a relatively unexplored area. Twenty seven bacterial isolates from three different soils were characterized for their plant growth promoting traits. A total of three native and five non-native bacteria were used with and without arbuscular mycorrhizal (AM) fungi in an open greenhouse pot experiment with two wheat varieties to evaluate their effect on wheat yield, nutrient uptake, and soil health parameters. Wheat plants subjected to native PGPB (CP4) (Bacillus subtilis) and AM fungi treatment gave the best results with reference to macronutrient (nitrogen and phosphorus), micronutrient (iron and zinc) content in wheat grains and yield-related parameters, including thousand grain weight, number of grains per spike and total tillers per plant in both wheat cultivars. Treatment with CP4 and CP4 plus AM fungi enhanced total chlorophyll in wheat leaves indicating higher photosynthetic activity. Significant improvement in soil health-related parameters, including soil organic matter and dehydrogenase activity, was observed. Significant correlation among grain yield-related parameters, nutrient enhancement, and soil health parameters was observed in PGPB and AM fungi treated plants, especially HD-3086. These results provide a roadmap for utilizing native PGPB and AM fungi for enhancing wheat production in Punjab state of India and exploring their utility in other parts of the country with different soil and environmental conditions.

Attenuation of neuroblastoma cell growth by nisin is mediated by modulation of phase behavior and enhanced cell membrane fluidity.

Antimicrobial peptides have been attracting significant attention as potential anti-cancer therapeutic agents in recent times. Yet most antimicrobial peptides seem to possess cytotoxic effects on non-cancerous cells. Nisin, an antimicrobial peptide and FDA approved food preservative, has recently been found to induce selective apoptotic cell death and reduced cell proliferation in different cancer cell lines. However, the mechanism of nisin interaction with cancer cell membranes remains unexplored. Using potentiometric dye-based fluorescence and monolayer surface pressure-area isotherms we find that nisin interaction enhances the fluidity and reduces the dipole potential of a neuroblastoma cell membrane model. The quantified compressibility modulus suggests that the changes in fluidity are predominantly driven by the nisin interaction with the non-raft like regions. However, the measured positive Gibbs free energy of mixing and enthalpy hints that nisin, owing to its unfavorable mixing with cholesterol, might significantly disrupt the raft-like domains.

Lipid-II Independent Antimicrobial Mechanism of Nisin Depends On Its Crowding And Degree Of Oligomerization.

Nisin inhibits bacterial growth by generating pores in cell membrane and interrupting cell-wall biosynthesis through specific lipid II interaction. However, the role of the hinge region and C-terminus residues of the peptide in antibacterial action of nisin is largely unknown. Here, using molecular dynamics simulations and experimental approach, we report that at high concentration regimes of nisin, interaction with phospholipids may equally deform the bacterial cell membranes even under significantly varying amounts of lipid-II. Membrane thinning, destabilization and decrease in lipid density depend on the degree of oligomerization of nisin. Growth kinetics of Bacillus subtilis and Escherichia coli interestingly show recovery by extended lag phase under low concentrations of nisin treatment while high concentrations of nisin caused decrease in cell viability as recorded by striking reduction in membrane potential and surface area. The significant changes in the dipole potential and fluorescence anisotropy were observed in negatively charged membranes in the absence of lipid-II with increasing concentration of nisin. The identical correlation of cell viability, membrane potential dissipation and morphology with the concentration regime of nisin, in both Bacillus subtilis (lipid II rich) and Escherichia coli (lipid II impoverished), hints at a non-specific physical mechanism where degree of membrane deformation depends on degree of crowding and oligomerization of nisin.