New l-Rhamnose-Binding Lectin from the Bivalve Glycymeris yessoensis: Purification, Partial Structural Characterization and Antibacterial Activity

In this study, a new l-rhamnose-binding lectin (GYL-R) from the hemolymph of bivalve Glycymeris yessoensis was purified using affinity and ion-exchange chromatography and functionally characterized. Lectin antimicrobial activity was examined in different ways. The lectin was inhibited by saccharides possessing the same configuration of hydroxyl groups at C-2 and C-4, such as l-rhamnose, d-galactose, lactose, l-arabinose and raffinose. Using the glycan microarray approach, natural carbohydrate ligands were established for GYL-R as l-Rha and glycans containing the α-Gal residue in the terminal position. The GYL-R molecular mass determined by MALDI-TOF mass spectrometry was 30,415 Da. The hemagglutination activity of the lectin was not affected by metal ions. The lectin was stable up to 75 °C and between pH 4.0 and 12.0. The amino acid sequence of the five GYL-R segments was obtained with nano-ESI MS/MS and contained both YGR and DPC-peptide motifs which are conserved in most of the l-rhamnose-binding lectin carbohydrate recognition domains. Circular dichroism confirmed that GYL is a α/β-protein with a predominance of the random coil. Furthermore, GYL-R was able to bind and suppress the growth of the Gram-negative bacteria E. coli by recognizing lipopolysaccharides. Together, these results suggest that GYL-R is a new member of the RBL family which participates in the self-defense mechanism against bacteria and pathogens with a distinct carbohydrate-binding specificity.

Recombinant Fusion Protein Containing Plant Nigellothionin Regulates the Growth of Food-Spoiling Fungus (Aspergillus niger)

This study aimed to obtain a recombinant chimeric protein named trx-NsW2 via theheterologous expression of the multifunctional antimicrobial peptide nigellothionin from black cumin (Nigella sativa L.) seeds in the Escherichia coli system. The protein was purified using a combination of Ni-NTA affinity chromatography and reversed-phase HPLC. Based on the HPLC calibration, the total yield of the protein was calculated to be 650 mg/L of bacterial culture. The fungistatic activity of trx-NsW2 against the food-spoiling fungus Aspergillus niger was demonstrated as itinhibited the maturation of conidiawithout affecting conidial germination or fungal growth. In contrast to mature nigellothionin NsW2, the fusion protein showeda low level of cytotoxicity towards both normal and tumor cell lines at concentrationsof up to 100-200 µM. Interestingly, at lower concentrations, it even stimulated cytokinesis. These findings are of critical importance for applying chimeric antimicrobial proteins obtained via microbiological synthesis in applied science.

Diversity of Cationic Antimicrobial Peptides in Black Cumin (Nigella sativa L.) Seeds

Black cumin (Nigella sativa L.) is known to possess a wide variety of antimicrobial peptides belonging to different structural families. Three novel antimicrobial peptides have been isolated from black cumin seeds. Two of them were attributed as members of the non-specific lipid transfer proteins family, and one as a defensin. We have made an attempt of using the proteomic approach for novel antimicrobial peptides search in N. sativa seeds as well. The use of a well-established approach that includes extraction and fractionation stages remains relevant even in the case of novel peptides search because of the lacking N. sativa genome data. Novel peptides demonstrate a spectrum of antimicrobial activity against plant pathogenic organisms that may cause economically important crop diseases. These results obtained allow considering these molecules as candidates to be applied in "next-generation" biopesticides development for agricultural use.

Staphylococcus aureus is able to generate resistance to novel lipoglycopeptide antibiotic gausemycin A

Gausemycin A is the first member of the novel lipoglycopeptides family produced by Streptomyces roseoflavus INA-Ac-5812. Gausemycin A has a pronounced bactericidal activity against methicillin-resistant Staphylococcus aureus. However, the ability of S. aureus to be resistant to gausemycin A has not been investigated yet. Using serial passaging, we have obtained the resistant variant S. aureus 5812R, which is 80 times more resistant compared to the parent strain. Susceptibility testing of S. aureus 5812R revealed the acquisition of cross-resistance to daptomycin, cefazolin, tetracycline, and gentamicin, while the resistance to vancomycin, nisin, and ramoplanin was absent. Whole genome sequencing revealed single nucleotide polymorphism (SNP) and deletions in S. aureus 5812R, among which are genes encoding efflux pump (sepA), the two-component Kdp system (kdpE), and the component of isoprenoid biosynthesis pathway (hepT). Phenotypically, S. aureus 5812R resembles a small-colony variant, as it is slow-growing, forms small colonies, and is deficient in pigments. Profiling of fatty acids (FA) composition constituting the cytoplasmic membrane of S. aureus 5812R revealed the prevalence of anteiso-branched FA, while straight FA was slightly less present. The evidence also showed that the gausemycin A-resistant strain has increased expression of the cls2 gene of the cardiolipin synthase. The performed checkerboard assay pointed out that the combination of gausemycin A and ciprofloxacin showed a synergistic effect against S. aureus 5812R.

C60 Fullerene Clusters Stabilize the Biologically Inactive Form of Topotecan

There is a range of experimental proofs that biologically relevant compounds change their activity in the presence of C₆₀ fullerene clusters in aqueous solution, which most frequently act as a nanoplatform for drug delivery. Inspired by this evidence, we made an effort to investigate the interaction of fullerene clusters with the antibiotic topotecan (TPT). This study proceeded in three steps, namely, UV/vis titration to confirm complexation and in vitro assays on proliferating and nonproliferating cells to elucidate the role of C₆₀ fullerene in the putative change in TPT activity. Surprisingly, although the nonproliferating cell assay is consistent with the titration data and confirms complex formation, it contradicted the results of the proliferating cell assay. The latter showed that the mixture of TPT and fullerene affects the cells in the same way as pure TPT, as if there were no fullerenes in solution at all, whereas the action of TPT was expected to be enhanced. We explained this contradiction by the specific stabilization of the biologically inactive carboxylate form of the antibiotic adsorbed in the alkaline shell of large fullerene clusters, which leads to neutralization of the drug delivery function and almost zero net biological effect of the antibiotic in vitro. The practical outcome of the work is that fullerene clusters can be used for the selective delivery of pH-sensitive drug forms.

Oak bark (Quercus sp. cortex) protects plants through the inhibition of quorum sensing mediated virulence of Pectobacterium carotovorum

Bacterial intercellular communication mediated by small diffusible molecules, known as quorum sensing (QS), is a common mechanism for regulating bacterial colonisation strategies and survival. Influence on QS by plant-derived molecules is proposed as a strategy for combating phytopathogens by modulating their virulence. This work builds upon other studies that have revealed plant-derived QS inhibitors extracted from oak bark (Quercus sp.). It was found that co-incubation of Pectobacterium carotovorum VKM-B-1247 with oak bark extract (OBE) reduced the production of acyl-HSL. This was accompanied by a dose-dependent decrease in the bacterial cellulolytic and protease activity. At the transcriptomic level, the OBE treatment suppressed the main QS-related genes expR/expI. Potato tubers pre-treated with OBE showed resistance to a manifestation of soft-rot symptoms. Analysis of the component composition of the OBE identified several biologically active molecules, such as n-hexadecanoic acid, 2,6-di-tert-butyl-4-methylphenol, butylated hydroxytoluene (BHT), gamma-sitosterol, lupeol, and others. Molecular docking of the binding energy between identified molecules and homology models of LuxR-LuxI type proteins allow to identify potential inhibitors. Collectively, obtained results figure out great potential of widely distributed oak-derived plant material for bacterial control during storage of potato.

Rational Design of Plant Hairpin-like Peptide EcAMP1: Structural-Functional Correlations to Reveal Antibacterial and Antifungal Activity

Plant antimicrobial peptides from the α-hairpinins family (hairpin-like peptides) are known to possess a wide range of biological activities. However, less is known about the structural determinants of their antimicrobial activity. Here, we suggest that spatial structure as well as surface charge and hydrophobicity level contribute to the antimicrobial properties of α-hairpinin EcAMP1 from barnyard grass (Echinochloa cruss-galli) seeds. To examine the role of the peptide spatial structure, two truncated forms of EcAMP1 restricted by inner and outer cysteine pairs were synthesized. It was shown that both truncated forms of EcAMP1 lost their antibacterial activity. In addition, their antifungal activity became weaker. To review the contribution of surface charge and hydrophobicity, another two peptides were designed. One of them carried single amino acid substitution from tryptophan to alanine residue at the 20th position. The second one represented a truncated form of the native EcAMP1 lacking six C-terminal residues. But the α-helix was kept intact. It was shown that the antifungal activity of both modified peptides weakened. Thereby we can conclude that the secondary structural integrity, hydrophobic properties, and surface charge all play roles in the antimicrobial properties of α-hairpinins. In addition, the antibacterial activity of cereal α-hairpinins against Gram-positive bacteria was described for the first time. This study expands on the knowledge of structure–function interactions in antimicrobial α-hairpinins.

High Resistance of Potato to Early Blight Is Achieved by Expression of the Pro-SmAMP1 Gene for Hevein-Like Antimicrobial Peptides from Common Chickweed (Stellaria media)

In the common chickweed Stellaria media, two antimicrobial peptides (AMPs), SmAMP1.1a and SmAMP1.2a, have been shown to be proteolytically released as products of the expression of a single gene, proSmAMP1. In this study, the gene proSmAMP1 was introduced into two potato varieties, Zhukovsky ranny and Udacha. These early-maturing varieties were shown to be susceptible to early blight caused by Alternaria spp. Most transgenic lines of either variety having strong expression of the target gene demonstrated high levels of resistance to Alternaria spp. during three years of cultivation, but did not otherwise differ from the initial varieties. Disease severity index (DSI) was introduced as a complex measure of plant susceptibility to early blight, taking into account the diameter of lesions caused by the Alternaria spp., the fungus sporulation intensity and its incubation period duration. Across all transgenic lines, the DSI inversely correlated both with the target gene expression and the copy number in the plant genome. Our results are promising for improving the resistance of potato and other crops to early blight by expression of AMPs from wild plants.

Gausemycins A,B: Cyclic Lipoglycopeptides from Streptomyces sp.*

We report a novel family of natural lipoglycopeptides produced by Streptomyces sp. INA-Ac-5812. Two major components of the mixture, named gausemycins A and B, were isolated, and their structures were elucidated. The compounds are cyclic peptides with a unique peptide core and several remarkable structural features, including unusual positions of d-amino acids, lack of the Ca²⁺ -binding Asp-X-Asp-Gly (DXDG) motif, tyrosine glycosylation with arabinose, presence of 2-amino-4-hydroxy-4-phenylbutyric acid (Ahpb) and chlorinated kynurenine (ClKyn), and N-acylation of the ornithine side chain. Gausemycins have pronounced activity against Gram-positive bacteria. Mechanistic studies highlight significant differences compared to known glyco- and lipopeptides. Gausemycins exhibit only slight Ca²⁺ -dependence of activity and induce no pore formation at low concentrations. Moreover, there is no detectable accumulation of cell wall biosynthesis precursors under treatment with gausemycins.

Seasonal changes in kinetic parameters of trypsin in gastric and agastric fish

The objective of the present study was to assess if trypsin, a key enzyme involved in protein digestion, presents some kind of functional adaptations to seasonal changes in water temperature in freshwater fish. In order to test this hypothesis, individuals of two fish species Carassius gibelio (agastric) and Perca fluviatilis (gastric) were sampled in the basin of Chany Lake (Siberia, Russia) at two different seasons (spring and summer). Apparent kinetic parameters (K_m and V_max) were determined for both species and seasons at the actual pH values in fish guts, and at actual temperatures. Results showed a significant effect of both the species and sampling season on the apparent kinetic parameters of trypsin. In the case of Prussian carp, K_m and V_max were lower for each assayed temperature (for 5 and 15 °C the differences were significant) for fish sampled in summer when compared to those sampled in spring. In contrast, values of K_m in perch tended to be lower in spring at 5 and 25 °C but these differences were not significant, while V_max showed a significant decrease in summer samples. This suggests a sort of functional adaptation of the same trypsin enzymes to seasonal changes, oriented to maximize protein digestion under variable conditions.

Nigellothionins from Black Cumin (Nigella sativa L.) Seeds Demonstrate Strong Antifungal and Cytotoxic Activity

High-cationic biologically active peptides of the thionins family were isolated from black cumin (Nigella sativa L.) seeds. According to their physicochemical characteristics, they were classified as representatives of the class I thionin subfamily. Novel peptides were called “Nigellothionins”, so-called because of their source plant. Thionins are described as components of plant innate immunity to environmental stress factors. Nine nigellothionins were identified in the plant in different amounts. Complete amino acid sequences were determined for three of them, and a high degree of similarity was detected. Three nigellothionins were examined for antifungal properties against collection strains. The dominant peptide, NsW2, was also examined for activity against clinical isolates of fungi. Cytotoxic activity was determined for NsW2. Nigellothionins activity against all collection strains and clinical isolates varied from absence to a value comparable to amphotericin B, which can be explained by the presence of amino acid substitutions in their sequences. Cytotoxic activity in vitro for NsW2 was detected at sub-micromolar concentrations. This has allowed us to propose an alteration of the molecular mechanism of action at different concentrations. The results obtained suggest that nigellothionins are natural compounds that can be used as antimycotic and anti-proliferative agents.

Peptide Extracts from Seven Medicinal Plants Discovered to Inhibit Oomycete Phytophthora infestans, a Causative Agent of Potato Late Blight Disease

We report the inhibitory effect of peptide extracts obtained from seven medicinal plants against a causative agent of late blight disease Phytophthora infestans. We find that all the extracts possess inhibitory activity toward the zoospores output, zoosporangium germination, and the development of P. infestans on potato disc tubers at different quantitative levels. Based on the biological effects detected, an extract of common horsetail (Equisetum arvense) biomass is recognized as the most effective and is selected for further structural analysis. We perform a combination of amino acid analysis and MALDI-TOF mass spectrometry, which reveal the presence of Asn/Asp- and Gln/Glu-rich short peptides with molecular masses in the range of 500-900 Da and not exceeding 1500 Da as the maximum. Analytical anion-exchange HPLC is successfully applied for separation of the peptide extract from common horsetail (E. arvense). We collect nine dominant components that are combined in two groups with differences in retention times. The N-terminal amino acid sequence of the prevalent compounds after analytical ion-exchange HPLC allows us to identify them as peptide fragments of functionally active proteins associated with photosynthesis, aquatic transport, and chitin binding. The anti-oomycete effects may be associated with the conversion of ribulose-1,5-bisphosphate carboxylase/oxygenase to produce a number of biologically active anionic peptides with possible regulatory functions. These data inform our knowledge regarding biologically active peptide fragments; they are the components of programmed or induced proteolysis of plant proteins and can realize secondary antimicrobial functions.

A Novel Peptide Antibiotic Produced by Streptomyces roseoflavus Strain INA-Ac-5812 With Directed Activity Against Gram-Positive Bacteria

In this work, we report the isolation and detailed functional characterization for the new non-ribosomally synthesized antibiotic 5812-A/C, which was derived from metabolites of Streptomyces roseoflavus INA-Ac-5812. According to its chemical structure, the studied 5812-A/C preliminary is composed of a cyclic peptide part covalently bounded with an arabinose residue. N-terminal amino acid sequencing of the native peptide has identified its partial structure of Leu-Asp-Gly-Ser-Gly and consisting of a Tyr residue that is supposed to have a two-component peptide nature for the molecule studied. However, the structural analysis of the antibiotic complex derived from S. roseoflavus INA-Ac-5812 is still ongoing. The mechanism of action of 5812-A/C was assessed in comparison with its most related analog, the lipopeptide antibiotic daptomycin, given the presence in both antimicrobials of an L-kynurenine amino acid residue. The inhibitory activity of 5812-A/C against Gram-positive bacteria including methicillin-resistant strain of Staphylococcus aureus was similar to daptomycin. The mechanism of action of 5812-A/C was associated with the disruption of membrane integrity, which differs in comparison with daptomycin and is most similar to the antimicrobial membrane-disturbing peptides. However, 5812-A/C demonstrated a calcium-dependent mode of action. In addition, unlike daptomycin, 5812-A/C was able to penetrate mature biofilms and inhibit the metabolic activity of embedded S. aureus cells. At the same time, 5812-A/C has no hemolytic activity toward erythrocyte, but possessed weak cytotoxic activity represented by heterochromatin condensation in human buccal epithelium cells. The biological properties of the peptide 5812-A/C suggest its classification as a calcium-dependent antibiotic effective against a wide spectrum of Gram-positive pathogenic bacteria.

Antimicrobial Activity of Microorganisms Isolated from Ant Nests of Lasius niger

In this study, the microbial communities of two nests of black garden ants (Lasius niger) in the hollows of stem branches of old apple trees were found to have similar species compositions: each community contained representatives of three species from the Bacillaceae family and one species of actinomycetes from the genus Streptomyces. In total, four types of bacilli and two actinomycetes were isolated. Actinomycetes were identified as Streptomyces antibioticus-like and Streptomyces sp. None of the bacilli had antibiotic activity, whereas both streptomycetes produced antibiotics that inhibited the growth of Gram-positive bacteria in vitro, including isolates from their community. Antibiotic compounds of S. antibioticus-like strain INA 01148 (Institute of New Antibiotics) were identified as actinomycin D and its closest homologue, actinomycin A. Actinomycins presumably change the microbial community of the ant nest substrate as they act against Gram-positive bacteria and against fungi and Gram-negative bacteria. The antibiotic activity of the isolated Streptomyces sp. INA 01156 is of interest, since the substances produced by this strain inhibit the growth of drug-resistant bacteria, including methicillin-resistant Staphylococcus aureus INA 00761 (MRSA) and vancomycin-resistant strain Leuconostoc mesenteroides VKPM B-4177 (VR) (VKPM-National Collection of Industrial Microorganisms (Russian acronym)).

Defense Peptides From the α-Hairpinin Family Are Components of Plant Innate Immunity

Plant immunity represents a sophisticated system, including both basal and inducible mechanisms, to prevent pathogen infection. Antimicrobial peptides (AMPs) are among the innate immunity components playing a key role in effective and rapid response against various pathogens. This review is devoted to a small family of defense peptides called α-hairpinins. The general characters of the family, as well as the individual features of each member, including biological activities, structures of precursor proteins, and spatial structures, are described. Possible applications of α-hairpinin peptides in drug design are discussed.

Isolation of antimicrobial peptides from different plant sources: Does a general extraction method exist?

Plants are good sources of biologically active compounds with antimicrobial activity, including polypeptides. Antimicrobial peptides (AMPs) represent one of the main barriers of plant innate immunity to environmental stress factors and are attracting much research interest. There are some extraction methods for isolation of AMPs from plant organs based on the type of extractant and initial fractionation stages. But most methods are directed to obtain some specific structural types of AMPs and do not allow to understand the molecular diversity of AMP inside a whole plant. In this mini-review, we suggest an optimized scheme of AMP isolation from plants followed by obtaining a set of peptides belonging to various structural families. This approach can be performed for large-scale screening of plants to identify some novel or homologous AMPs for fundamental and applied studies.

Sub-inhibitory Effects of Antimicrobial Peptides

Antimicrobials, and particularly antimicrobial peptides (AMPs), have been thoroughly studied due to their therapeutic potential. The research on their exact mode of action on bacterial cells, especially at under sublethal concentrations, has resulted in a better understanding of the unpredictable nature of bacterial behavior under stress conditions. In this review, we were aiming to gather the wide yet still under-investigated knowledge about various AMPs and their subinhibition effects on cellular and molecular levels. We describe how AMP action is non-linear and unpredictable, also showing that exposure to AMP can lead to antimicrobial resistance via triggering various regulatory systems. Being one of the most known types of antimicrobials, bacteriocins have dual action and can also be utilized by microorganisms as signaling molecules at naturally achievable sub-inhibitory concentrations. The unpredictable nature of AMP action and the pathogenic response triggered by them remains an area of knowledge that requires further investigation.

Diversity of Harpin-Like Defense Peptides from Barnyard Grass (Echinochloa crusgalli L.) Seeds

The results of the study of the structure and function of harpin-like peptides (alpha-harpinins) of the EcAMP group from the barnyard grass (E. crusgalli) seeds and the possibility of their involvement in the innate immunity to biotic stresses are presented.

A Novel Lipopeptaibol Emericellipsin A with Antimicrobial and Antitumor Activity Produced by the Extremophilic Fungus Emericellopsis alkalina

Soil fungi are known to contain a rich variety of defense metabolites that allow them to compete with other organisms (fungi, bacteria, nematodes, and insects) and help them occupy more preferential areas at the expense of effective antagonism. These compounds possess antibiotic activity towards a wide range of other microbes, particularly fungi that belong to different taxonomical units. These compounds include peptaibols, which are non-ribosomal synthesized polypeptides containing non-standard amino acid residues (alpha-aminoisobutyric acid mandatory) and some posttranslational modifications. We isolated a novel antibiotic peptide from the culture medium of Emericellopsis alkalina, an alkalophilic strain. This peptide, called emericellipsin A, exhibited a strong antifungal effect against the yeast Candida albicans, the mold fungus Aspergillus niger, and human pathogen clinical isolates. It also exhibited antimicrobial activity against some Gram-positive and Gram-negative bacteria. Additionally, emericellipsin A showed a significant cytotoxic effect and was highly active against Hep G2 and HeLa tumor cell lines. We used NMR spectroscopy to reveal that this peptaibol is nine amino acid residues long and contains non-standard amino acids. The mode of molecular action of emericellipsin A is most likely associated with its effects on the membranes of cells. Emericellipsin A is rather short peptaibol and could be useful for the development of antifungal, antibacterial, or anti-tumor remedies.

A Low-Molecular-Weight Compound Derived from Human Leukocytes Determines a Bactericidal Activity of the Interferon Preparation

The aim of this study was to characterize the structure and mode of action of antimicrobials derived from a commercial preparation of alfa-interferon. By combination of semi-preparative/analytical reversed-phase high-performance liquid chromatography, we isolated and purified a novel active substance based on carbohydrate with a complex of amino acids, which determines antimicrobial property of commercial preparation of interferon. A size-exclusion chromatography was performed and LC/ESI-MS revealed molecular masses of active substance were in the range of 180-249 Da. Edman sequencing identified phenylthiohydantoin (PTH) derivatives which consisted a set of preliminary (Asp, Glu, Gly, and Ala) and minor amino acids (Leu and Thr) at equimolar ratio. Thus, the purified active substance is a compound containing the complex of amino acids connected with carbohydrate background and called leucidin. Leucidin demonstrated antimicrobial activity against the model Escherichia coli (E. coli) K12 strain at a minimal inhibitory concentration of 20 μg mL^-1. The revealed antimicrobial mechanism of action is associated with violation of the bacterial cell wall leading to a SOS response and bacterial autolysis. Despite the preliminary nature of the results, obtained data allowed us to discover the previously unknown leukocyte-derived antimicrobial molecules.

Antimicrobial activity of the indolicidin-derived novel synthetic peptide In-58

Natural peptides with antimicrobial activity are extremely diverse, and peptide synthesis technologies make it possible to significantly improve their properties for specific tasks. Here, we investigate the biological properties of the natural peptide indolicidin and the indolicidin-derived novel synthetic peptide In-58. In-58 was generated by replacing all tryptophan residues on phenylalanine in D-configuration; the α-amino group in the main chain also was modified by unsaturated fatty acid. Compared with indolicidin, In-58 is more bactericidal, more resistant to proteinase K, and less toxic to mammalian cells. Using molecular physics approaches, we characterized the action of In-58 on bacterial cells at the cellular level. Also, we have found that studied peptides damage bacterial membranes. Using the Escherichia coli luminescent biosensor strain MG1655 (pcolD'::lux), we investigated the action of indolicidin and In-58 at the subcellular level. At subinhibitory concentrations, indolicidin and In-58 induced an SOS response. Our data suggest that indolicidin damages the DNA, but bacterial membrane perturbation is its principal mode of action. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Defense peptide repertoire of Stellaria media predicted by high throughput next generation sequencing

Being perfectly adapted to diverse environments, chickweed (Stellaria media (L.) Vill), a ubiquitous garden weed, grows widely in Europe and North America. As opposed to the model plants, many weeds, and S. media in particular, have been poorly studied, although they are likely to contain promising components of immunity and novel resistance genes. In this study, for the first time RNA-seq analysis of healthy and infected with Fusarium oxysporum chickweed seedlings, as well as de novo transcriptome assembly and annotation, are presented. Note, this research is focused on antimicrobial peptides (AMPs), the major components of plant immune system. Using custom software developed earlier, 145 unique putative AMPs (pAMPs) including defensins, thionins, hevein-like peptides, snakins, alpha-hairpinins, LTPs, and cysteine-rich peptides with novel cysteine motifs were predicted. Furthermore, changes in AMP expression profile in response to fungal infection were traced. In addition, the comparison of chickweed AMP repertoire with those of other Caryophyllaceae plants whose transcriptomes are presently available is made. As a result, alpha-hairpinins and hevein-like peptides which display characteristic modular structure appear to be specific AMPs distinguishing S. media from Dianthus caryophyllus, Silene vulgaris, and Silene latifolia. Finally, revealing several AMPs with proven antimicrobial activity gives opportunity to conclude that the presented method of AMP repertoire analysis reveals highly active AMPs playing vital role in plant immunity.

Novel haemoglobin-derived antimicrobial peptides from chicken (Gallus gallus) blood: purification, structural aspects and biological activity

AIM

To purify and characterize antimicrobial peptides derived from the acid extract of Gallus gallus blood cells.

METHODS AND RESULTS

Two polypeptides (i.e. CHb-1 and CHb-2) with antibacterial activity were detected in the acidic extract of blood cells from chicken (G. gallus). The isolated peptides that possessed a potent antibacterial activity were purified using a two-step chromatography procedure that involved solid-phase extraction of a total protein/peptide extract followed by thin fractionation by reversed-phase high performance liquid chromatography (RP-HPLC). The molecular masses of the purified peptides were similar and were 4824·4 and 4825·2 Da, which have been measured by matrix-assisted laser desorption/ionization mass spectrometry (MALDI TOF MS). Their amino acid sequences were determined by Edman degradation and showed that the peptides were fully identical to the two fragments of G. gallus α-haemoglobin localized into different subunits (A and D respectively). The peptides were active in micromolar concentrations against Gram-negative Escherichia coli K12 TG1. Using the 1-N-phenylnaphthylamine, the FITC-dextran labelled probes and the live/dead staining allowed to show the hemocidin mode of action and estimate the pore size.

CONCLUSION

In this study, for the first time, α-haemoglobin from chicken (G. gallus) has been investigated as a donor of the two high homologous native peptide fragments that possess potent antibacterial activity in vitro. These are membrane-active peptides and their mechanism of action against E. coli involves a toroidal pore formation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The obtained results expand the perception of the role of haemoglobin in a living system, describing it as a source of multifunction substances. Additionally, the data presented in this paper may contribute to the development of new, cost-effective, antimicrobial agents.

[Genes encoding hevein-like antimicrobial peptides WAMPs: Expression in response to phytohormones and environmental factors]

We investigated the role of genes of hevein-like antimicrobial peptides of the WAMP family in the protection of wheat plants against biotic and abiotic stress. The semiquantitative RT-PCR method was used to examine the expression of wamp genes in wheat seedlings in response to infection by pathogens and exposure to phytohormones and ions of a heavy metal ion—cadmium. We discovered that wheat germ contamination by harmful fungi significantly increases expression of genes of the wamp family, and the primary transcript is wamp-2. We determined that salicylic acid, rather than methyl jasmonate, induces expression of genes of the wamp family. We showed that abiotic stress induced by cadmium ions inhibits expression of wamp genes in the roots with no effect on their expression in shoots. The results support the protective role of wamp genes in the response of wheat plants to infections by pathogens. In turn, the resistance to abiotic stress induced by cadmium ions does not appear to be associated with expression of genes of the wamp family.

Studying of cellular interaction of hairpin-like peptide EcAMP1 from barnyard grass (Echinochloa crusgalli L.) seeds with plant pathogenic fungus Fusarium solani using microscopy techniques

An interaction of recombinant hairpin-like cationic peptide EcAMP1 with conidia of plant pathogenic fungus Fusarium solani at the cellular level was studied by a combination of microscopic methods. EcAMP1 is from barnyard grass (Echinochloa crusgalli L.), and obtained by heterologous expression in Escherichia coli system. As a result, a direct relationship between hyphal growth inhibition and increasing active peptide concentration, time of incubation and fungal physiological condition has been determined. Dynamics of accumulation and redistribution of the peptide studied on fungal cellular cover and inside the conidia cells has been shown. The dynamics are dependent on time of coupling, as well as, a dissimilarity of EcAMP1 binding with cover of fungal conidia and its stepwise accumulation and diffuse localization in the cytoplasm. Correlation between structural disruption of fungal conidia and the presence of morphological changes has also been found. The correlation was found under the influence of peptide high concentrations at concentrations above 32 μM. The results indicate the presence of a binding of EcAMP1 with the surface of fungal conidia, thus, demonstrating a main specificity for its antifungal action at the cellular level. These results, however, cannot exclude the existence of attendant EcAMP1 action based on its intracellular localization on some specific targets. SCANNING 38:591-598, 2016. © 2016 Wiley Periodicals, Inc.

Characterization of Extracellular Yeast Peptide Factors and Their Stress-Protective Effect on Probiotic Lactic Acid Bacteria

Protective effect of the extracellular peptide fraction (reactivating factors, RF) produced by yeasts of various taxonomic groups (Saccharomyces cerevisiae, Kluyveromyces lactis, Candida utilis, and Yarrowia li- polytica) on probiotic lactic acid bacteria (LAB) Lactobacillus casei, L. acidophilus,'and L. reuteri under bile salt (BS)-induced stress was shown. RF of all yeasts were shown to be of peptide nature; the active component of the S. cerevisiae RF was identified as a combination of low-molecular polypeptides with molecular masses of 0.6 to 1.5 kDa. The protective and reactivating effects of the yeast factors were not species-specific and were similar to those of the Luteococcusjaponicus subsp. casei R. In BS-treated cells of the tester bacteria, a pro- tective effect was observed after 10-min preincubation of the LAB cell suspension with yeast RE: the number of surviving cells (CFU) was 2 to 4.5 times higher than in the control. The reactivating effect was observed when RF was added to LAB cell suspensions not later than 15 min after stress treatment. It was less pro- nounced than the protector effect, with the CFU number I to 3 times that of the control. Both the protector and the reactivating effects were most pronounced in the S. cerevisiae and decreased in the row: C. utilis > K. lactis > Y lipolytica. The efficiency of protective action of yeast RF was found to depend on the properties of recepient LAB cells, with the L. casei strain being most sensitive to BS treatment. In both variants, the highest protective effect of RF (increase in the CFU number) was observed for L. acidophilus, while the least pronounced one, for L. casei. The reasons for application of the LAB strains combining high stress resistance and high response to stress-protecting metabolites, including RF factors, as probiotics, is discussed.

[BIOLOGICAL ACTIVITY OF ANTIMICROBIAL PEPTIDES FROM CHICKENS THROMBOCYTES]

AIM

Isolation and study of biological activity of antimicrobial peptides from chickens thrombocytes.

MATERIALS AND METHODS

Peptides from chickens thrombocytes, obtained by reverse-phase high-performance liquid chromatography method with stepped and linear gradients of concentration increase of the organic solvent were used in the study. Their antimicrobial activity was determined by microtitration method in broth; mechanism of biological effect--by using fluorescent spectroscopy method with DNA-tropic dyes.

RESULTS

Individual fractions of peptides were isolated from chickens thrombocytes, that possess antimicrobial activity against Staphylococcus aureus P209 and Escherichia coli K12. A disruption of integrity of barrier structures of microorganisms under the effect of thrombocyte antimicrobial peptides and predominance of cells with damaged membrane in the population of E. coli was established.

CONCLUSION

The data obtained on antimicrobial activity and mechanism of bactericidal effect of the peptide fractions from chickens thrombocytes isolated for the first time expand the understanding of functional properties of chickens thrombocytes and open a perspective for their further study with the aim of use as antimicrobial means.

Novel proline-hydroxyproline glycopeptides from the dandelion (Taraxacum officinale Wigg.) flowers: de novo sequencing and biological activity

Two novel homologous peptides named ToHyp1 and ToHyp2 that show no similarity to any known proteins were isolated from Taraxacum officinale Wigg. flowers by multidimensional liquid chromatography. Amino acid and mass spectrometry analyses demonstrated that the peptides have unusual structure: they are cysteine-free, proline-hydroxyproline-rich and post-translationally glycosylated by pentoses, with 5 carbohydrates in ToHyp2 and 10 in ToHyp1. The ToHyp2 peptide with a monoisotopic molecular mass of 4350.3Da was completely sequenced by a combination of Edman degradation and de novo sequencing via top down multistage collision induced dissociation (CID) and higher energy dissociation (HCD) tandem mass spectrometry (MS(n)). ToHyp2 consists of 35 amino acids, contains eighteen proline residues, of which 8 prolines are hydroxylated. The peptide displays antifungal activity and inhibits growth of Gram-positive and Gram-negative bacteria. We further showed that carbohydrate moieties have no significant impact on the peptide structure, but are important for antifungal activity although not absolutely necessary. The deglycosylated ToHyp2 peptide was less active against the susceptible fungus Bipolaris sorokiniana than the native peptide. Unique structural features of the ToHyp2 peptide place it into a new family of plant defense peptides. The discovery of ToHyp peptides in T. officinale flowers expands the repertoire of molecules of plant origin with practical applications.

[Antimicrobial Activity of Fungi Strains of Trichoderma from Middle Siberia]

The antibiotic activity in 42 strains of 8 species of the Trichoderma genus (T. asperellum, T. viride, T. hamatum, T. koningii, T. atroviride, T. harzianum, T. Citrinoviride, and T. longibrachiatum) isolated from different Siberian ecotops was studied. It was shown that these species differ in the degree of their antibacterial and antifungal activity. The chosen strain, T. citrinoviride TV4-1, exhibited high activity and a wide range of actions against the opportunistic and pathogenic fungi of the Aspergillus and Candida albicans genus; bacteria, including methicillin-resistant Staphylococcus aureus; and cancer cells. According to mass and I R spectrometry data and the spectrum of biological action, peptaibols are probably the most active compounds in the strain culture extracts.

[BIOLOGICAL ACTIVITY OF ANTIMICROBIAL PEPTIDES OF ENTEROCOCCUS FAECIUM]

AIM

Isolate bacteriocins from Enterococcus faecium metabolites and characterize their effect on cells of Gram positive (Listeria monocytogenes) and Gram negative (Escherichia coli) bacteria.

MATERIALS AND METHODS

Methods of solid-phase extraction, ion-exchange and reversed phase chromatography were applied for isolation of bacteriocins from cultural medium of bacteria MALDI time-of-flight mass-spectrometry was used for characterization of the obtained preparations. The mechanism of biological effect of peptides was evaluated using DNA-tropic dyes (SYTO 9 and PI) with subsequent registration of fluorescence spectra: Atomic-force microscopy (AFM) was used for characterization of morpho-functional reaction of target cells.

RESULTS

Peptide fractions with mass of 1.0 - 3.0 kDa were isolated from enterococci metabolites, that inhibit the growth of indicator microorganisms. E. faecium strain exoproducts were shown to increase membrane permeability during interaction with L. monocytogenes, that results in subsequent detectable disturbance of normal cell morphology of listeria. Alterations of E. coli surface during the effect of purified peptide fraction was detected using AFM.

CONCLUSION

The studies carried out have revealed the effect of bacteriocins of enterococci on microorganisms with various types of cell wall composition and have confirmed the importance of bacterial barrier structure permeability disturbance in the mechanism of antimicrobial effect of enterocins.

[Reactivating factor of Luteococcus japonicus subsp. casei: isolation and characterization]

It has been shown that a producer strain of reactivating factor (RF) is identical to a typical strain of Luteococcus japonicus DSM 10546 from the Propionibacteriaceae family according to the physiological and biochemical properties and the sequencing of 16S rRNA fragments. A number of phenotypical differences from the model strain allowed the producer strain to be considered a subspecies of Luteococcus japonicus, and it was named Luteococcus japonicus subsp. casei. At cultivation of the producer, RF is secreted into the medium and plays the role of a signaling molecule. RF antioxidant activities towards various organic radicals may be a possible mechanism of its protective and reactivating effects. Metabolites secreted by the L. casei producer strain into the culture medium were separated by a combination of liquid chromatographies. Four components possessing biological activities were found. The most active one was studied by MALDI-TOF mass spectrometry, which revealed that it is a polypeptide. Primary identification of some amino acid residues was performed. Sugar residues were found in the structure.

[Comparative analysis of natural and synthetic antimutagens as regulators of gene expression in human cells under exposure to ionizing radiation]

This paper studies the effect of plant peptides of thionine Ns-W2 extracted from seeds of fennel flower (Nigella sativa) and β-purothionine from wheat germs (Triticum kiharae), as well as a synthetic antimutagen (crown-compound), on the expression of several genes involved in the.control of cellular homeostasis, processes of carcinogenesis, and radiation response in human rhabdomyosarcoma cells (RD cells), T-lymphoblastoid cell line Jurkat, and blood cells. All of these agents acted as antimutagens-anticarcinogens, reducing the expression of genes involved in carcinogenesis (genes of families MMP, TIMP, and IAP and G-protein genes) in a tumor cell. A pronounced reduction in the mRNA level of these genes was caused by thionine Ns-W2, and the least effect was demonstrated by β-purothionine. Antimutagens had very little effect on the mRNA levels of the several studied genes in normal blood cells.

[Antimicrobial Activity of Substances Produced by Trichoderma citrinoviride Strain VKPM F-1228: Optimization of Cultivation and Assessment of Spectrum of Individual Peptaibols]

The Trichoderma citrinoviride VKPM F-1228 strain produces a complex of peptide-based antibiotics with antibacterial and antimycotic action. Synthesis of peptaibols is closely related to the conidiogenesis in the culture. The optimal procedure of the strain cultivation for production of peptaibols is stationary growing for 14 days at a temperature of 28 degrees C and pH 7.5 followed by formation of a dense mycelium film on the modified Saburo medium containing 30 gr/l of glucose and 12.5 gr/l of peptone. Eight individual peptaibols were extracted. The spectrum of their activity was estimated with the use of opportunistic bacteria and micromycetes as well as pathogenic clinical aspergilli. Compounds 9, 13, 14, 15 and 16 were shown active against opportunistic fungi and bacteria including methicillin resistant S. aureus, whereas compounds 9, 13 and 14 in addition showed antimycotic activity against clinical aspergilli.

Novel mode of action of plant defense peptides - hevein-like antimicrobial peptides from wheat inhibit fungal metalloproteases

The multilayered plant immune system relies on rapid recognition of pathogen-associated molecular patterns followed by activation of defense-related genes, resulting in the reinforcement of plant cell walls and the production of antimicrobial compounds. To suppress plant defense, fungi secrete effectors, including a recently discovered Zn-metalloproteinase from Fusarium verticillioides, named fungalysin Fv-cmp. This proteinase cleaves class IV chitinases, which are plant defense proteins that bind and degrade chitin of fungal cell walls. In this study, we investigated plant responses to such pathogen invasion, and discovered novel inhibitors of fungalysin. We produced several recombinant hevein-like antimicrobial peptides named wheat antimicrobial peptides (WAMPs) containing different amino acids (Ala, Lys, Glu, and Asn) at the nonconserved position 34. An additional Ser at the site of fungalysin proteolysis makes the peptides resistant to the protease. Moreover, an equal molar concentration of WAMP-1b or WAMP-2 to chitinase was sufficient to block the fungalysin activity, keeping the chitinase intact. Thus, WAMPs represent novel protease inhibitors that are active against fungal metalloproteases. According to in vitro antifungal assays WAMPs directly inhibited hyphal elongation, suggesting that fungalysin plays an important role in fungal development. A novel molecular mechanism of dynamic interplay between host defense molecules and fungal virulence factors is suggested.

Novel antifungal α-hairpinin peptide from Stellaria media seeds: structure, biosynthesis, gene structure and evolution

Plant defense against disease is a complex multistage system involving initial recognition of the invading pathogen, signal transduction and activation of specialized genes. An important role in pathogen deterrence belongs to so-called plant defense peptides, small polypeptide molecules that present antimicrobial properties. Using multidimensional liquid chromatography, we isolated a novel antifungal peptide named Sm-AMP-X (33 residues) from the common chickweed (Stellaria media) seeds. The peptide sequence shows no homology to any previously described proteins. The peculiar cysteine arrangement (C(1)X3C(2)XnC(3)X3C(4)), however, allocates Sm-AMP-X to the recently acknowledged α-hairpinin family of plant defense peptides that share the helix-loop-helix fold stabilized by two disulfide bridges C(1)-C(4) and C(2)-C(3). Sm-AMP-X exhibits high broad-spectrum activity against fungal phytopathogens. We further showed that the N- and C-terminal "tail" regions of the peptide are important for both its structure and activity. The truncated variants Sm-AMP-X1 with both disulfide bonds preserved and Sm-AMP-X2 with only the internal S-S-bond left were progressively less active against fungi and presented largely disordered structure as opposed to the predominantly helical conformation of the full-length antifungal peptide. cDNA and gene cloning revealed that Sm-AMP-X is processed from a unique multimodular precursor protein that contains as many as 12 tandem repeats of α-hairpinin-like peptides. Structure of the sm-amp-x gene and two related pseudogenes sm-amp-x-ψ1 and sm-amp-x-ψ2 allows tracing the evolutionary scenario that led to generation of such a sophisticated precursor protein. Sm-AMP-X is a new promising candidate for engineering disease resistance in plants.

A novel hairpin-like antimicrobial peptide from barnyard grass (Echinochloa crusgalli L.) seeds: Structure-functional and molecular-genetics characterization

A novel plant hairpin-like defense polypeptide named EcAMP3 was isolated from latent barnyard grass (Echinochloa crusgalli L.) seeds. The native peptide and its recombinant analogue were characterized. EcAMP3 displays antifungal and antibacterial activity in vitro. The gene family encoding EcAMPs precursor protein was also characterized; the genes and pseudogenes of this family show 97-100% homology. Every member of EcAMPs precursor family contains seven identical cysteine motifs: C1XXXC2(11-13)C3XXXC4. One of those motifs corresponds to the isolated peptide. EcAMP3 is the first member of the plant hairpin-like peptide family that inhibits the growth of phytopathogenic bacteria. Obtained results can explain the nature of the complex resistance of barnyard grass to a variety of pathogenic microorganisms.

A novel cysteine-rich antifungal peptide ToAMP4 from Taraxacum officinale Wigg. flowers

A novel peptide named ToAMP4 was isolated from Taraxacum officinale Wigg. flowers by a combination of acetic acid extraction and different types of chromatography: affinity, size-exclusion, and RP-HPLC. The amino acid sequence of ToAMP4 was determined by automated Edman degradation. The peptide is basic, consists of 41 amino acids, and incorporates three disulphide bonds. Due to the unusual cysteine spacing pattern, ToAMP4 does not belong to any known plant AMP family, but classifies together with two other antimicrobial peptides ToAMP1 and ToAMP2 previously isolated from the dandelion flowers. To study the biological activity of ToAMP4, it was successfully produced in a prokaryotic expression system as a fusion protein with thioredoxin. The recombinant peptide was shown to be identical to the native ToAMP4 by chromatographic behavior, molecular mass, and N-terminal amino acid sequence. The peptide displays broad-spectrum antifungal activity against important phytopathogens. Two ToAMP4-mediated inhibition strategies depending on the fungus were demonstrated. The results obtained add to our knowledge on the structural and functional diversity of AMPs in plants.

Genes encoding 4-Cys antimicrobial peptides in wheat Triticum kiharae Dorof. et Migush.: multimodular structural organization, instraspecific variability, distribution and role in defence

A novel family of antifungal peptides was discovered in the wheat Triticum kiharae Dorof. et Migusch. Two members of the family, designated Tk-AMP-X1 and Tk-AMP-X2, were completely sequenced and shown to belong to the α-hairpinin structural family of plant peptides with a characteristic C1XXXC2-X(n)-C3XXXC4 motif. The peptides inhibit the spore germination of several fungal pathogens in vitro. cDNA and gene cloning disclosed unique structure of genes encoding Tk-AMP-X peptides. They code for precursor proteins of unusual multimodular structure, consisting of a signal peptide, several α-hairpinin (4-Cys) peptide domains with a characteristic cysteine pattern separated by linkers and a C-terminal prodomain. Three types of precursor proteins, with five, six or seven 4-Cys peptide modules, were found in wheat. Among the predicted family members, several peptides previously isolated from T. kiharae seeds were identified. Genes encoding Tk-AMP-X precursors have no introns in the protein-coding regions and are upregulated by fungal pathogens and abiotic stress, providing conclusive evidence for their role in stress response. A combined PCR-based and bioinformatics approach was used to search for related genes in the plant kingdom. Homologous genes differing in the number of peptide modules were discovered in phylogenetically-related Triticum and Aegilops species, including polyploid wheat genome donors. Association of the Tk-AMP-X genes with A, B/G or D genomes of hexaploid wheat was demonstrated. Furthermore, Tk-AMP-X-related sequences were shown to be widespread in the Poaceae family among economically important crops, such as barley, rice and maize.

Defense peptides from barnyard grass (Echinochloa crusgalli L.) seeds

A number of defense polypeptides from latent seeds of weed cereal barnyard grass (Echinochloa crusgalli L.) has been isolated and characterized using an acidic extraction and high performance liquid chromatography methods in combination with MALDI-TOF mass spectrometry and Edman sequencing. Members of three antimicrobial peptide families and two protease inhibitor families were found to be localized in barnyard grass seeds. Their biological activity concerning to Gram-Positive and Gram-Negative phytopathogenic bacteria, as well as oomycete Phytophthora infestans, has been investigated. Diversity of barnyard grass defense peptides is a significant factor that provides a resistance of E. crusgalli seeds to germination and latent phases.

Discovery of novel antimicrobial peptides with unusual cysteine motifs in dandelion Taraxacum officinale Wigg. flowers

Three novel antimicrobial peptides designated ToAMP1, ToAMP2 and ToAMP3 were purified from Taraxacum officinale flowers. Their amino acid sequences were determined. The peptides are cationic and cysteine-rich and consist of 38, 44 and 42 amino acid residues for ToAMP1, ToAMP2 and ToAMP3, respectively. Importantly, according to cysteine motifs, the peptides are representatives of two novel previously unknown families of plant antimicrobial peptides. ToAMP1 and ToAMP2 share high sequence identity and belong to 6-Cys-containing antimicrobial peptides, while ToAMP3 is a member of a distinct 8-Cys family. The peptides were shown to display high antimicrobial activity both against fungal and bacterial pathogens, and therefore represent new promising molecules for biotechnological and medicinal applications.

[Antimutagenic activity of wheat beta-purothionin Tk-AMP-BP]

Antimutagenic activity on human RD cells was studied for beta-purothionin Tk-AMP-BP isolated from seeds of wheat Triticum kiharae, which has a higher stress resistance. Cadmium chloride at 5 x 10(-6) M was used as a mutagen. The numbers of DNA breaks in mutagen-treated and intact cells were inferred from the single-stranded to double-stranded DNA ratio and expressed as protection coefficients. The protective effect was simultaneously assayed for aqueous plant extracts known to possess antioxidant properties. Wheat thionin was the most active among all of the antimutagens examined; its protection coefficient reached 85-88% at micromolar peptide concentrations (8-32 microg/ml). Thus, wheat beta-purothionin was for the first time demonstrated to be highly efficient in protecting human cell DNA from the damaging effect of cadmium chloride.

Disulfide-stabilized helical hairpin structure and activity of a novel antifungal peptide EcAMP1 from seeds of barnyard grass (Echinochloa crus-galli)

This study presents purification, activity characterization, and (1)H NMR study of the novel antifungal peptide EcAMP1 from kernels of barnyard grass Echinochloa crus-galli. The peptide adopts a disulfide-stabilized α-helical hairpin structure in aqueous solution and thus represents a novel fold among naturally occurring antimicrobial peptides. Micromolar concentrations of EcAMP1 were shown to inhibit growth of several fungal phytopathogens. Confocal microscopy revealed intensive EcAMP1 binding to the surface of fungal conidia followed by internalization and accumulation in the cytoplasm without disturbance of membrane integrity. Close spatial structure similarity between EcAMP1, the trypsin inhibitor VhTI from seeds of Veronica hederifolia, and some scorpion and cone snail toxins suggests natural elaboration of different functions on a common fold.