Characterization and Diversity of Microcystins Produced by Cyanobacteria from the Curonian Lagoon (SE Baltic Sea)

Microcystins (MCs) are the most widely distributed and structurally diverse cyanotoxins that can have significant health impacts on living organisms, including humans. The identification of MC variants and their quantification is very important for toxicological assessment. Within this study, we explored the diversity of MCs and their potential producers from the Curonian Lagoon. MC profiles were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, while the potential producers were detected based on the presence of genus-specific mcyE gene sequences. Among the numerous MCs detected, one new potential MC variant with m/z 1057 was partially characterized. Moreover, two other MCs with m/z 1075 and m/z 1068 might belong to new variants with serine (Ser), rarely detected in position one of the peptides. They might also represent MC-Y(OMe)R and MC-WR, respectively. However, the application of a low-resolution MS/MS system made the unambiguous identification of the MCs impossible. Based on this example, the problems of peptide structure identification are discussed in the work. Genetic analysis revealed that potential MCs producers include Dolichospermum/Anabaena, Microcystis spp., and Planktothrix agardhii. The diversity and temporal variations in MC profiles may indicate the presence of several chemotypes of cyanobacteria in the Curonian Lagoon.

Influence of non-protein amino-acid mimosine in peptide conformational propensities from novel Amber force field parameters

Mimosine is a non-protein amino acid derived from plants known for its ability to bind to divalent or trivalent metal cations such as Zn$^{2+}$, Ni$^{2+}$, Fe$^{2+}$ or Al$^{3+}$. This results in interesting antimicrobial and anti-cancer properties, which make mimosine a promising candidate for therapeutic applications. One possibility is to incorporate mimosine into synthetic short peptide drugs. However, our understanding of how this amino acid affects peptide structure is still limited, reducing our ability to design effective therapeutic compounds. In this work, we used computer simulations to understand this question. We first build parameters for the mimosine residue to be used in combination with two classical force fields of the Amber family. Then, we used atomistic molecular dynamics simulations with the resulting parameter sets to evaluate the influence of mimosine in the structural propensities for this amino acid. We compared the results of these simulations with identical peptides where mimosine is replaced by either phenylalanine or tyrosine. We found that the strong dipole in mimosine induces a preference for conformations where the amino acid rings are stacked over more traditional conformations. We validated our results using quantum mechanical calculations, which provide a robust foundation to the outcome of our classical simulations.

Iron-Stimulated Production and Antimicrobial Potential of a Novel Biosurfactant Produced by a Drilling Waste-Degrading Pseudomonas citronellolis Strain

A Pseudomonas citronellolis strain was isolated from drilling waste (DW). This strain utilizes DW as the sole energy and carbon source to produce biosurfactants (BSs). The BS produced was thermally stable, amorphous and includes a peptide structure. FeSO4, FeCl3 and Fe(NO3)3 were supplemented at various concentration levels to assess possible enhancement of BS production and DW biodegradation. The limit concentration of Fe compounds between the increase in BS formation and microbial toxicity was 0.1 mM. FeCl3 enhanced DW biodegradation and more than doubled the BS formation yield, determining an optimization strategy for BS production. The BS was then partially purified and used against several Gram-negative and positive multi-drug resistant bacteria (such as Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli spp, Acinetobacter baumaniii, Enterococcus faecalis spp, Streptococcus pneumoniae, Staphylococcus aureus, Salmonella enterica). The minimum inhibitory concentration was defined at a range of 0.25 to 10 mg/mL. The antimicrobial properties of the partially purified BS established its effectiveness and suggested a down-stream processing cost reduction, as no additional purification steps were necessary. The study could lead to a sustainable low-cost bioprocess towards a circular bioeconomy because waste, a non-expensive substrate, is used; while the BS holds great potential as a novel compound with antibiotic and disinfectant-like action, following toxicity testing with human cells.

A self-assembled protein nanoparticle serving as a one-shot vaccine carrier

In this paper, we are exploring the role of an amphipathic helical peptide in mediating the self-assembly of a fusion protein into a protein nanoparticle and the application of the nanoparticle as a one-shot vaccine carrier. Out of several candidates, an amphipathic helical peptide derived from M2 protein of type A influenza virus is found to stimulate high antigenicity when fused to a fluorescent protein genetically. This fusion protein was found to form protein nanoparticle spontaneously when expressed and purified protein stimulates long-lasting antibody responses in single immunization. Through modeling peptide structure and nanoparticle assembly, we have improved this vaccine carrier in complex stability. The revised vaccine carrier is able to stimulate constant antibody titer to a heterologous antigen for at least six months in single immunization. The immune response against a heterologous antigen can be boosted further by additional immunization in spite of high immune responses to carrier protein.