Separation of ochratoxins by centrifugal partition chromatography

The present research work was dedicated to developing an efficient method based on liquid-liquid chromatography (centrifugal partition chromatography, CPC) applicable to routine purifications of ochratoxins (OT) from the liquid culture of the strain A. albertensis SZMC 2107. The crude extract contained numerous components in addition to OTA (90.1 %,) and OTB (1.1 %,) according to HPLC examinations. For the separation of OTs by CPC, several tertiary systems based on acetonitrile, acetone, and short-chain alcohols were examined to find the most applicable biphasic system. The hexane/i-propanol/water 35:15:50 system supplemented with 0.1 % acetic acid was found to be the most efficient for use in CPC separation. Using liquid-liquid instrumental separation, the two OTs, namely OTA (2.23 mg) and OTB (0.031 mg), were successfully isolated with 96.3 % and-72.8 % purity, respectively, from 1 L ferment broth. The identities and purities of the purified components were confirmed and the performance parameters of each separation step and the whole procedure were determined. The developed method could be used effectively to purify OTs for analytical or toxicological applications.

Corrigendum: The mycoremediation potential of the armillarioids: a comparative genomics analysis

[This corrects the article DOI: 10.3389/fbioe.2023.1189640.].

Modeling the Effect on a Novel Fungal Peptaibol Placed in an All-Atom Bacterial Membrane Mimicking System via Accelerated Molecular Dynamics Simulations

We previously reported on a novel peptaibol, named Tripleurin XIIc (TPN), an 18-residue long sequence produced by the fungus Trichoderma pleuroti. We elucidated its 3D structure via classical and accelerated molecular dynamics simulation (aMD) methods and reported the folding dynamics of TPN in water and chloroform solvents. Peptaibols, in general, are insoluble in water, as they are amphipathic and may prefer hydrophobic environments like transmembrane regions. In this study, we attempted to use aMD simulations to model an all-atom bacterial membrane system while placing a TPN molecule in its vicinity. The results highlighted that TPN was able to introduce some disorder into the membrane and caused lipid clustering. It could also enter the transmembrane region from the water-bilayer interface. The structural dynamics of TPN in the transmembrane region revealed a single energetically stable conformation similar to the one obtained from water and chloroform solvent simulations reported by us previously. However, this linear structure was found to be at the local energy minimum (stable) in water but at a metastable intermediate state (higher energy) in chloroform. Therefore, it could be said that the water solvent can be successfully used for folding simulations of peptaibols.

Acquired Triazole Resistance Alters Pathogenicity-Associated Features in Candida auris in an Isolate-Dependent Manner

Fluconazole resistance is commonly encountered in Candida auris, and the yeast frequently displays resistance to other standard drugs, which severely limits the number of effective therapeutic agents against this emerging pathogen. In this study, we aimed to investigate the effect of acquired azole resistance on the viability, stress response, and virulence of this species. Fluconazole-, posaconazole-, and voriconazole- resistant strains were generated from two susceptible C. auris clinical isolates (0381, 0387) and compared under various conditions. Several evolved strains became pan-azole-resistant, as well as echinocandin-cross-resistant. While being pan-azole-resistant, the 0381-derived posaconazole-evolved strain colonized brain tissue more efficiently than any other strain, suggesting that fitness cost is not necessarily a consequence of resistance development in C. auris. All 0387-derived evolved strains carried a loss of function mutation (R160S) in BCY1, an inhibitor of the PKA pathway. Sequencing data also revealed that posaconazole treatment can result in ERG3 mutation in C. auris. Despite using the same mechanisms to generate the evolved strains, both genotype and phenotype analysis highlighted that the development of resistance was unique for each strain. Our data suggest that C. auris triazole resistance development is a highly complex process, initiated by several pleiotropic factors.

The mycoremediation potential of the armillarioids: a comparative genomics analysis

Genes involved in mycoremediation were identified by comparative genomics analysis in 10 armillarioid species and selected groups of white-rot Basidiomycota (14) and soft-rot Ascomycota (12) species to confine the distinctive bioremediation capabilities of the armillarioids. The genomes were explored using phylogenetic principal component analysis (pPCA), searching for genes already documented in a biocatalysis/biodegradation database. The results underlined a distinct, increased potential of aromatics-degrading genes/enzymes in armillarioids, with particular emphasis on a high copy number and diverse spectrum of benzoate 4-monooxygenase [EC:1.14.14.92] homologs. In addition, other enzymes involved in the degradation of various monocyclic aromatics were more abundant in the armillarioids than in the other white-rot basidiomycetes, and enzymes involved in the degradation of polycyclic aromatic hydrocarbons (PAHs) were more prevailing in armillarioids and other white-rot species than in soft-rot Ascomycetes. Transcriptome profiling of A. ostoyae and A. borealis isolates confirmed that several genes involved in the degradation of benzoates and other monocyclic aromatics were distinctively expressed in the wood-invading fungal mycelia. Data were consistent with armillarioid species offering a more powerful potential in degrading aromatics. Our results provide a reliable, practical solution for screening the likely fungal candidates for their full biodegradation potential, applicability, and possible specialization based on their genomics data.

Characterization of the Sterol 24-C-Methyltransferase Genes Reveals a Network of Alternative Sterol Biosynthetic Pathways in Mucor lusitanicus

Certain members of the order Mucorales can cause a life-threatening, often-fatal systemic infection called mucormycosis. Mucormycosis has a high mortality rate, which can reach 96 to 100% depending on the underlying condition of the patient. Mucorales species are intrinsically resistant to most antifungal agents, such as most of the azoles, which makes mucormycosis treatment challenging. The main target of azoles is the lanosterol 14α-demethylase (Erg11), which is responsible for an essential step in the biosynthesis of ergosterol, the main sterol component of the fungal membrane. Mutations in the erg11 gene can be associated with azole resistance; however, resistance can also be mediated by loss of function or mutation of other ergosterol biosynthetic enzymes, such as the sterol 24-C-methyltransferase (Erg6). The genome of Mucor lusitanicus encodes three putative erg6 genes (i.e., erg6a, erg6b, and erg6c). In this study, the role of erg6 genes in azole resistance of Mucor was analyzed by generating and analyzing knockout mutants constructed using the CRISPR-Cas9 technique. Susceptibility testing of the mutants suggested that one of the three genes, erg6b, plays a crucial role in the azole resistance of Mucor. The sterol composition of erg6b knockout mutants was significantly altered compared to that of the original strain, and it revealed the presence of at least four alternative sterol biosynthesis pathways leading to formation of ergosterol and other alternative, nontoxic sterol products. Dynamic operation of these pathways and the switching of biosynthesis from one to the other in response to azole treatment could significantly contribute to avoiding the effects of azoles by these fungi. IMPORTANCE The fungal membrane contains ergosterol instead of cholesterol, which offers a specific point of attack for the defense against pathogenic fungi. Indeed, most antifungal agents target ergosterol or its biosynthesis. Mucormycoses-causing fungi are resistant to most antifungal agents, including most of the azoles. For this reason, the drugs of choice to treat such infections are limited. The exploration of ergosterol biosynthesis is therefore of fundamental importance to understand the azole resistance of mucormycosis-causing fungi and to develop possible new control strategies. Characterization of sterol 24-C-methyltransferase demonstrated its role in the azole resistance and virulence of M. lusitanicus. Moreover, our experiments suggest that there are at least four alternative pathways for the biosynthesis of sterols in Mucor. Switching between pathways may contribute to the maintenance of azole resistance.

Identifications of Surfactin-Type Biosurfactants Produced by Bacillus Species Isolated from Rhizosphere of Vegetables

Surfactins are cyclic lipopeptides consisting of a β-hydroxy fatty acid of variable chain length and a peptide ring of seven amino acids linked together by a lactone bridge, forming the cyclic structure of the peptide chain. These compounds are produced mainly by Bacillus species and are well regarded for their antibacterial, antifungal, and antiviral activities. For their surfactin production profiling, several Bacillus strains isolated from vegetable rhizospheres were identified by their fatty acid methyl ester profiles and were tested against phytopathogen bacteria and fungi. The isolates showed significant inhibition against of E. amylovora, X. campestris, B. cinerea, and F. culmorum and caused moderate effects on P. syringae, E. carotovora, A. tumefaciens, F. graminearum, F. solani, and C. gloeosporioides. Then, an HPLC-HESI-MS/MS method was applied to simultaneously carry out the quantitative and in-depth qualitative characterisations on the extracted ferment broths. More than half of the examined Bacillus strains produced surfactin, and the MS/MS spectra analyses of their sodiated precursor ions revealed a total of 29 surfactin variants and homologues, some of them with an extremely large number of peaks with different retention times, suggesting a large number of variations in the branching of their fatty acid chains.

Structure-activity correlations for peptaibols obtained from clade Longibrachiatum of Trichoderma: A combined experimental and computational approach

Integrated disease management and plant protection have been discussed with much fervor in the past decade due to the rising environmental concerns of using industrially produced pesticides. Members of the genus Trichoderma are a subject of considerable research today due to their several properties as biocontrol agents. In our study, the peptaibol production of Trichoderma longibrachiatum SZMC 1775, T. longibrachiatum f. bissettii SZMC 12546, T. reesei SZMC 22616, T. reesei SZMC 22614, T. saturnisporum SZMC 22606 and T. effusum SZMC 22611 were investigated to elucidate structure-activity relationships (SARs) between the properties of peptaibols and their 3D structures. The effects of peptaibol mixtures obtained from every Trichoderma strain were examined against nine commonly known bacteria. The lowest minimum inhibitory concentrations (MIC, mg ml^-1) were exerted by T. longibrachiatum f. bissettii SZMC 12546 against Gram-positive bacteria, which was also able to inhibit the plant pathogenic Gram-negative Rhizobium radiobacter. Accelerated molecular dynamics (aMD) simulations were performed in aqueous solvent to explore the folding dynamics of 12 selected peptaibol sequences. The most characteristic difference between the peptaibols from group A and B relies in the 'Gly-Leu-Aib-Pro' and 'Gly-Aib-Aib-Pro' motifs ('Aib' stands for α-aminoisobutyric acid), which imparted a significant effect on the folding dynamics in water and might be correlated with their expressed bioactivity. In our aMD simulation experiments, Group A peptaibols showed more restricted folding dynamics with well-folded helical conformations as the most stable representative structures. This structural stability and dynamics may contribute to their bioactivity against the selected bacterial species.

Characterization of the antagonistic potential of the glyphosate-tolerant Pseudomonas resinovorans SZMC 25872 strain against the plant pathogenic bacterium Agrobacterium tumefaciens

The utilization of microorganisms with biocontrol activity against fungal and bacterial pathogens of plants is recognized as a promising, effective, and environment-friendly strategy to protect agricultural crops. We report the glyphosate-tolerant Pseudomonas resinovorans SZMC 25872 isolate as a novel strain with antagonistic potential towards the plant pathogenic bacterium Agrobacterium tumefaciens. In our studies, the growth of the P. resinovorans SZMC 25872 and A. tumefaciens SZMC 14557 isolates in the presence of 74 different carbon sources, and the effect of 11 carbon sources utilized by both strains on the biocontrol efficacy was examined. Seven variations of media with different carbon sources were selected for the assays to observe the biocontrol potential of the P. resinovorans strain. Also, 50% concentrations of the cell-free culture filtrates (CCF) obtained from medium amended with L-alanine or succinic acid as sole carbon source were found to be effective for the growth suppression of A. tumefaciens by 83.03 and 56.80%, respectively. The effect of 7 media on siderophore amount and the activity of extracellular trypsin- and chymotrypsin-like proteases, as well as esterases were also evaluated. Significant positive correlation was found between the siderophore amount and the percentage of inhibition, and the inhibitory effect of the CCFs obtained from medium amended with succinic acid was eliminated in the presence of an additional iron source, suggesting that siderophores produced by P. resinovorans play an important role in its antagonistic potential. The metabolic profile analysis of the P. resinovorans SZMC 25872 strain, performed by high performance liquid chromatography - high resolution mass spectrometry (HPLC-HRMS), has identified several previously not reported metabolites that might play role in the antagonistic effect against A. tumefaciens. Based on our findings we suggest that the possible inhibition modes of A. tumefaciens SZMC 14557 by P. resinovorans SZMC 25872 include siderophore-mediated suppression, extracellular enzyme activities and novel bioactive metabolites.

Preparation of 3-O-, 5-O- and N-palmitoyl derivatives of fumonisin B1 toxin and their characterisation with NMR and LC-HRMS methods

We have previously published six esterified O-acyl (EFB1) and three N-acyl fumonisin B₁ derivatives extracted from rice cultures inoculated with Fusarium verticillioides, amongst these the identification of N-palmitoyl-FB1 has been clearly established in a spiking experiment. At that time, it was assumed that as in the case of O-acyl-FB1 derivatives, linoleic-, oleic- or palmitic acid esterify through the OH group on the 3C or 5C atom of the carbon chain of the fumonisins. In our most recent experiments, we have synthetically acylated the FB1 toxin and subsequently purified 3-O-palmitoyl- and 5-O-palmitoyl-FB1 toxins in addition to the N-palmitoyl-FB1 toxin. They were identified and characterised using ¹H and ¹³C NMR as well as LC-HRMS. Our aim was the identification of the previously detected O-acyl-FB1 derivatives over the course of a spiking experiment, which were obtained through the solid-phase fermentation of Fusarium verticillioides. By spiking the three synthesized and identified components one-by-one into the fungal culture extract and analysing these cultures using LC-MS, it was clearly demonstrated that the F. verticillioides strain produced both the 5-O-palmitoyl-FB1 and N-palmitoyl-FB1 toxins, but did not produce 3-O-palmitoyl-FB1. Thus, it is highly probable that the components thought to be 3-O-acyl-(linoleoyl-, oleoyl-, palmitoyl-) FB1 derivatives in our previous communication are presumably 10-O-acyl-FB1 derivatives. Since these acylated FB1 derivatives can occur naturally in e.g. maize, the use of these synthesized components as reference materials is of great importance in order to obtain accurate qualitative and quantitative data on the occurrence of acylated fumonisins in different matrices including maize based feed samples. The production of these substances has also made it possible to test their toxicity in cell culture and small animal experiments.

A rare case of calvarial tuberculosis from the Avar Age (8th century CE) cemetery of Kaba-Bitózug (Hajdú-Bihar county, Hungary) - Pathogenesis and differential diagnostic aspects

The aim of our paper is to present and discuss in detail the bony changes indicative of tuberculosis (TB) that were identified in a skeleton (KB67), unearthed from grave 67 of the 8th-century-CE cemetery of Kaba-Bitózug (Hungary). Furthermore, to provide the differential diagnoses of the observed alterations, with special attention to the cranial osteolytic lesions. During the macro- and micromorphological examinations of KB67, the skull revealed three small, well-circumscribed, punched-out osteolytic lesions accompanied by endocranial granular impressions, abnormal blood vessel impressions, periosteal appositions, and cortical erosion. The postcranial skeleton exhibited osteolytic lesions, cortical remodelling and erosion, and signs of hypervascularisation in the spine. Based on the differential diagnosis of the cranial osteolytic lesions and their co-occurrence with endocranial and vertebral bony changes indicative of TB, they most likely resulted from tuberculous involvement of the frontal and left parietal bones. The morphologically established diagnosis was confirmed by a PCR analysis that provided evidence for the presence of Mycobacterium tuberculosis DNA in KB67. KB67, the first reported archaeological case with calvarial TB from the present-day territory of Hungary, gives us a unique insight into the occurrence of a rare manifestation of TB in the Avar Age of the Great Plain.

The effect of harvest time and vintage year on the phenolic composition of Nero and Bianca wines

Fungal disease resistant (PIWI) interspecific grape varieties are playing an important role as an alternative for organic wine production. Organic (bio) wines are demanded by numerous conscious consumers around the globe. They choose this kind of wines predominantly because of the absence of synthetic pesticides, fertilisers and sustainable agriculture. Resistant grape growing moreover results in additional environmental and health benefits. Nero and Bianca are among Hungary's most promising interspecific grape cultivars gaining international interest recently, there are, however, limited vitivinicultural knowledge on them. Our aim was to examine the flavonoid and anthocyanin composition for both interspecific varieties during different harvest times in two consecutive vintages. The date of harvest and vintage played a significant effect on grape and wine quality.

Divergent Synthesis, Antiproliferative and Antimicrobial Studies of 1,3-Aminoalcohol and 3-Amino-1,2-Diol Based Diaminopyrimidines

A series of novel diaminopyrimidines containing pinane moieties were synthesized via an efficient methodology starting from pinane-based aminoalcohols, aminodiols and 2,4-dichloropyrimidines. Bioassay tests demonstrated that compound 18a displayed much stronger antiproliferative activities against four human cancer cell lines (HeLa, Siha, MDA-MB-231, MCF-7 and A2780) than positive control cisplatin. In particular, compound 22a was found to be selective in inhibiting HeLa cell proliferation with cancer cell growth inhibition values higher than 95 %. Moreover, the in vitro screening of prepared compounds against different bacterial and fungal strains is reported. The results revealed that 12b and 17a, the most promising compounds, displayed selective inhibition for the Gram-positive bacteria (B. subtilis and S. aureus) with percent inhibition values ranging from 75 to 95 % at 10 μg/mL concentration. Both selective inhibition and the in vitro activity values demonstrated that these compounds have the potential to be developed into clinically important therapeutic choices for the treatment of infections caused by B. subtilis and S. aureus.

Comparison Evaluation of the Biological Effects of Sterigmatocystin and Aflatoxin B1 Utilizing SOS-Chromotest and a Novel Zebrafish (Danio rerio) Embryo Microinjection Method

Aflatoxin B1 (AFB1) is a potent mycotoxin and natural carcinogen. The primary producers of AFB1 are Aspergillus flavus and A. parasiticus. Sterigmatocystin (STC), another mycotoxin, shares its biosynthetic pathway with aflatoxins. While there are abundant data on the biological effects of AFB1, STC is not well characterised. According to published data, AFB1 is more harmful to biological systems than STC. It has been suggested that STC is about one-tenth as potent a mutagen as AFB1 as measured by the Ames test. In this research, the biological effects of S9 rat liver homogenate-activated and non-activated STC and AFB1 were compared using two different biomonitoring systems, SOS-Chromotest and a recently developed microinjection zebrafish embryo method. When comparing the treatments, activated STC caused the highest mortality and number of DNA strand breaks across all injected volumes. Based on the E. coli SOS-Chromotest, the two toxins exerted the same genotoxicities. Moreover, according to the newly developed zebrafish microinjection method, STC appeared more toxic than AFB1. The scarce information correlating AFB1 and STC toxicity suggests that AFB1 is a more potent genotoxin than STC. Our findings contradict this assumption and illustrate the need for more complex biomonitoring systems for mycotoxin risk assessment.

Discrimination between the Two Closely Related Species of the Operational Group B. amyloliquefaciens Based on Whole-Cell Fatty Acid Profiling

(1) Background: Bacillus velezensis and Bacillus amyloliquefaciens are closely related members of the “operational group B. amyloliquefaciens”, a taxonomical unit above species level within the ”Bacillus subtilis species complex”. They have similar morphological, physiological, biochemical, phenotypic, and phylogenetic characteristics. Thus, separating these two taxa from each another has proven to be difficult to implement and could not be pushed easily into the line of routine analyses. (2) Methods: The aim of this study was to determine whether whole FAME profiling could be used to distinguish between these two species, using both type strains and environmental isolates. Initially, the classification was determined by partial sequences of the gyrA and rpoB genes and the classified isolates and type strains were considered as samples to develop the identification method, based on FAME profiles. (3) Results: The dissimilarities in 16:0, 17:0 iso, and 17:0 FA components have drawn a distinction between the two species and minor differences in FA 14:0, 15:0 iso, and 16:0 iso were also visible. The statistical analysis of the FA profiles confirmed that the two taxa can be distinguished into two separate groups, where the isolates are identified without misreading. (4) Conclusions: Our study proposes that the developed easy and fast-automated identification tool based on cellular FA profiles can be routinely applied to distinguish B. velezensis and B. amyloliquefaciens.

The effect of acquired triazole resistance on abiotic stress tolerance and virulence in Candida auris micro evolved strains

Recently, C. auris become one of the most prominent members of the genus Candida. Since its occurrence, several C. auris outbreaks have been reported worldwide. These outbreaks were associated with isolates displaying decreased susceptibility towards fluconazole, the first-line agent for prophylaxis. Fluconazole is the most frequently used antifungal drug to treat bloodstream Candida infections.

The physiological effects of acquired antifungal resistance was investigated in this species using fluconazole, posaconazole and voriconazole resistant mutant strains generated by the in vitro microevolution method. Alterations in antifungal susceptibility and cross resistance were determined by the microdilution method, utilizing azoles (fluconazole, voriconazole, posaconazole), echinocandins (caspofungin, micafungin, anidulafungin) and a polyene (amphotericin B). Changes in the abiotic stress tolerance was examined by spotting assay, using osmotic stressors, cell wall perturbants and a membrane detergent. To evaluate the impact of the acquired resistance on sterol biosynthesis, ergosterol composition of all generated mutant strains were examined. A potential relationship between virulence and acquired antifungal resistance was also studied both in vitro and in vivo. Phagocytosis of the generated strains by J774.2 mouse macrophage-like cells was measured and analyzed by flow cytometry. In the murine infection model fungal burden of the triazole evolved strains was determined in spleen, kidney, liver and brain and compared to the fungal burden associated with the initial azole susceptible strain. Significant differences in virulence of the initial and the generated strains was observed suggesting a potential connection between the virulence and antifungal susceptibility of the emerging fungal pathogen, C. auris.

Biological evaluation of antiproliferative and anti-invasive properties of an androstadiene derivative on human cervical cancer cell lines

Gynaecological cancers are leading cause of death: breast cancer is the most frequently diagnosed type of malignancies, and cervical neoplasms rank fourth for both incidence and mortality among women worldwide. In one of our previous studies, favourable antiproliferative and antimetastatic properties of a newly synthesized androstane derivative, 17APAD have been demonstrated on breast cancer cell lines with different expression patterns of hormone receptors. The aim of the current study was to investigate the antitumoral potential of this molecule in cervical cancer cell lines, including SiHa cells positive for human papilloma virus (HPV) type 16 and HPV-negative C33A cells. 17APAD exerted pronounced growth-inhibition (with IC₅₀ values ranging from 0.76 to 1.72 μM with considerable cancer selectivity), while cisplatin used as a reference agent yielded higher IC₅₀ values (ranging from 3.69 to 12.43) and less selectivity, as evidenced by MTT assay. The proapoptotic effect and morphological changes induced by 17APAD were detected by Hoechst 33258-propidium iodide or Annexin V-Alexa488-propidium iodide fluorescent double staining methods, supplemented with a caspase-3 activity assay to identify the mechanism behind the programmed cell death induced by 17APAD. Additionally, significant and concentration-dependent elevation of the ratio of cells in the G2/M phase, on the expense of G0/G1 phase, was observed after 48 h of exposure to 17APAD. Besides its potent antiproliferative properties against both cervical cancer cell lines, 17APAD elicited a remarkable inhibition of cell migration and invasion as detected in wound-healing and Boyden chamber assays, respectively. The mechanisms of action underlying the effects of 17APAD on cell proliferation and motility were independent of androgenic activity, as demonstrated by the Yeast Androgen Screen method. Our results provide new evidence for the proapoptotic and anti-invasive properties of 17APAD, suggesting that it is worth of further research, as a promising prototype for designing novel anticancer agents.

Novel (+)-Neoisopulegol-Based O-Benzyl Derivatives as Antimicrobial Agents

Discovery of novel antibacterial agents with new structures, which combat pathogens is an urgent task. In this study, a new library of (+)-neoisopulegol-based O-benzyl derivatives of aminodiols and aminotriols was designed and synthesized, and their antimicrobial activity against different bacterial and fungal strains were evaluated. The results showed that this new series of synthetic O-benzyl compounds exhibit potent antimicrobial activity. Di-O-benzyl derivatives showed high activity against Gram-positive bacteria and fungi, but moderate activity against Gram-negative bacteria. Therefore, these compounds may serve a good basis for antibacterial and antifungal drug discovery. Structure-activity relationships were also studied from the aspects of stereochemistry of the O-benzyl group on cyclohexane ring and the substituent effects on the ring system.

Comprehensive characterization of stress tolerant bacteria with plant growth-promoting potential isolated from glyphosate-treated environment

The application of plant growth-promoting bacteria in agricultural systems is an efficient and environment-friendly strategy to improve crop yields and maintain soil quality. However, as different soils have diverse and specific ecological characteristics and may represent adverse abiotic conditions, in vivo application requires the careful selection of the desired beneficial microorganisms. In this study we report Ensifer adhaerens SZMC 25856 and Pseudomonas resinovorans SZMC 25875 isolates recovered from glyphosate-treated soil to possess yet undiscovered plant growth-enhancing potential. The strains were found to promote the growth of tomato seedlings significantly, to have the ability of synthesizing indole-3-acetic acid and siderophores, to tolerate pH in the range of 6.59-7.96, salinity up to 12.5 g L-1 NaCl and drought up to 125 g L-1 polyethylene glycol 6000, as well as to survive in the presence of various pesticides including glyphosate, diuron, chlorotoluron, carbendazim and thiabendazole, and heavy metals such as Al, Fe, Mn, Zn, Pb and Cu. The plant growth-promoting traits of the examined E. adhaerens and P. resinovorans isolates and their tolerance to numerous abiotic stress factors make them promising candidates for application in different agricultural environments, including soils polluted with glyphosate.

Revealing of biodiversity and antimicrobial effects of Artemisia asiatica endophytes

Endophytic fungi produce a plethora of secondary metabolites, which may open new avenues to study their applicability in pharmaceuticals. Therefore, the present study focuses on the fungal endophytic community of Artemisia asiatica. During our work, fungal endophytes were isolated from a medicinal plant, A. asiatica. The culturable endophytic fungi were identified using molecular techniques and biodiversity, richness and tissue specificity were examined. As these microorganisms have been generally identified as an abundant reservoir of novel antimicrobial compounds, the antimicrobial (i.e. antibacterial and antifungal) activities of the metabolites produced by the isolated fungi were studied. Numerous extracts containing the endophytic metabolites proved to be active against the applied test microorganisms including Gram-positive and Gram-negative bacteria, as well as yeasts and filamentous fungi, which can be examined in detail in the future and, based on the the chemical nature of these active metabolites, allow to discover novel bioactive metabolites.

Isolation and detailed characterisation of the first sterigmatocystin hyperproducer mould strain in Hungary

Aspergillus strains were isolated from Hungarian mills in order to get information on the appearance of sterigmatocystin (ST) producing moulds, whose presence has never been demonstrated in Hungary. Fungal isolates were classified into nine morphotypes, sections Nigri, Nidulantes, Versicolores (two morphotypes), Circumdati, Flavi (two morphotypes), Clavati and Terrei by classical mycological assays. ST producing strains could be classified into section Versicolores. ST production of the isolates was assessed by liquid and solid phase growth experiments and compared to ST producing reference strains: Aspergillus pepii SzMC 22332, Aspergillus versicolor SzMC 22333, Aspergillus griseoaurantiacus SzMC 22334 and Aspergillus nidulans RDIT9.32. Four of our isolates marked as Km11, Km14, Km26 and Km31 showed ST production in liquid medium. ST production on solid phase corn grit substrate was measured after three weeks of incubation, and Km26 isolate proved to be the most prominent with a toxin concentration of 277.1 μg g−1, surpassing all reference strains. The toxin-producing ability of Km26 isolate was also tested in a field experiment, where corn was infected. By the end of the experiment, ST level of 19.56 μg kg−1 was measured in infected corn.

Molecular taxonomic identification of the Km26 strain was performed using internal transcribed spacer (ITS), calmodulin and tubulin sequence analyses. Based on these studies, strain Km26 was identified as Aspergillus creber.

Here we report that an ST-producing A. creber strain has appeared in Hungary, and the Km26 strain is the first known extreme ST-producing mould in this country. As a result of climate change, aflatoxin B1 producing Aspergillus flavus strains have appeared in Hungary in the last decade. As strain Km26 is the only A. creber isolate in Hungary so far, there is no sign of mass prevalence, and due to the lower temperature optimum of the species compared to A. flavus, its appearance is probably not related to climate change.

Verification of tuberculosis infection among Vác mummies (18th century CE, Hungary) based on lipid biomarker profiling with a new HPLC-HESI-MS approach

Tuberculosis (TB) was a large burden of infections that peaked during the 19th century in Europe. Mummies from the 18th century CE, discovered in the crypt of a church at Vác, Hungary, had high TB prevalence, as revealed by amplification of key fragments of TB DNA and genome-wide TB analysis. Complementary methods are needed to confirm these diagnoses and one approach uses the identification of specific lipid biomarkers, such as TB mycocerosic acids (MCs). Previously, MC derivatives were profiled by specialised gas chromatography-mass spectrometry (GC-MS), so an alternative more direct approach has been developed. Underivatized MCs are extracted and analysed by high-performance liquid chromatography linked to a mass spectrometer, in heated electrospray ionisation mode (HPLC-HESI-MS). The method was validated using representatives of the Mycobacterium tuberculosis complex and other mycobacteria and tested on six Vác mummy cases, previously considered positive for TB infection. Analysing both rib and soft tissue samples, four out of six cases gave profiles of main C32 and major C29 and C39 mycocerosates correlating well with those of M. tuberculosis. Multidisciplinary methods are needed in the diagnosis of ancient tuberculosis; this new protocol accesses important confirmatory evidence, as demonstrated by the confirmation of TB in the Vác mummies.

Bile accelerates carcinogenic processes in pancreatic ductal adenocarcinoma cells through the overexpression of MUC4

Pancreatic cancer (PC) is one of the leading causes of mortality rate globally and is usually associated with obstructive jaundice (OJ). Up to date, there is no clear consensus on whether biliary decompression should be performed prior to surgery and how high levels of serum bile affects the outcome of PC. Therefore, our study aims were to characterise the effect of bile acids (BAs) on carcinogenic processes using pancreatic ductal adenocarcinoma (PDAC) cell lines and to investigate the underlying mechanisms. Liquid chromatography-mass spectrometry was used to determine the serum concentrations of BAs. The effects of BAs on tumour progression were investigated using different assays. Mucin expressions were studied in normal and PDAC cell lines and in human samples at gene and protein levels and results were validated with gene silencing. The levels of BAs were significantly higher in the PDAC + OJ group compared to the healthy control. Treating PDAC cells with different BAs or with human serum obtained from PDAC + OJ patients enhanced the rate of proliferation, migration, adhesion, colony forming, and the expression of MUC4. In PDAC + OJ patients, MUC4 expression was higher and the 4-year survival rate was lower compare to PDAC patients. Silencing of MUC4 decreased BAs-induced carcinogenic processes in PDAC cells. Our results show that BAs promote carcinogenic process in PDAC cells, in which the increased expression of MUC4 plays an important role. Based on these results, we assume that in PC patients, where the disease is associated with OJ, the early treatment of biliary obstruction improves life expectancy.

Corrigendum: Structural Diversity and Bioactivities of Peptaibol Compounds From the Longibrachiatum Clade of the Filamentous Fungal Genus Trichoderma

[This corrects the article DOI: 10.3389/fmicb.2019.01434.].

Wild Strawberry, Blackberry, and Blueberry Leaf Extracts Alleviate Starch-Induced Hyperglycemia in Prediabetic and Diabetic Mice

Intestinal α-glucosidase and α-amylase break down nutritional poly- and oligosaccharides to monosaccharides and their activity significantly contributes to postprandial hyperglycemia. Competitive inhibitors of these enzymes, such as acarbose, are effective antidiabetic drugs, but have unpleasant side effects. In our ethnopharmacology inspired investigations, we found that wild strawberry (Fragaria vesca), blackberry (Rubus fruticosus), and European blueberry (Vaccinium myrtillus) leaf extracts inhibit α-glucosidase and α-amylase enzyme activity in vitro and are effective in preventing postprandial hyperglycemia in vivo. Toxicology tests on H9c2 rat embryonic cardiac muscle cells demonstrated that berry leaf extracts have no cytotoxic effects. Oral administration of these leaf extracts alone or as a mixture to normal (control), obese, prediabetic, and streptozotocin-induced diabetic mice attenuated the starch-induced rise of blood glucose levels. The efficiency was similar to that of acarbose on blood glucose. These results highlight berry leaf extracts as candidates for testing in clinical trials in order to assess the clinical significance of their effects on glycemic control.

Characterization of the Plant Growth-Promoting Activities of Endophytic Fungi Isolated from Sophora flavescens

Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of both biotic and abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains that could be applied to enhance crop yield and quality. In our study, the plant growth-promoting activities of endophytic fungi isolated from various parts of Sophora flavescens (a medicinally important plant in Mongolia and China) have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth-promoting abilities were evaluated in plate assays. Altogether, 15 strains were isolated, representing the genera Alternaria, Didymella, Fusarium and Xylogone. Five of the isolates possessed phosphate solubilization activities and twelve secreted siderophores, while all of them were able to produce indoleacetic acid (IAA) in the presence or absence of tryptophan. The endogenous and exogenous accumulation of IAA were also monitored in liquid cultures using the HPLC-MS/MS technique to refine the plate assay results. Furthermore, for the highest IAA producer fungi, the effects of their extracts were also examined in plant bioassays. In these tests, the primary root lengths of the model Arabidopsis thaliana were increased in several cases, while the biomasses were significantly lower than the control IAA treatment. Significant alterations have also been detected in the photosynthetic pigment (chlorophyll-a, -b and carotenoids) content due to the fungal extract treatments, but these changes did not show any specific trends.

Stereoselective synthesis and application of isopulegol-based bi- and trifunctional chiral compounds

A new family of isopulegol-based bi- and trifunctional chiral ligands such as triols, tetrols, aminodiols and aminotriols was developed from commercially available (−)-isopulegol with antibacterial, antifungal and antioxidant activities.

Characterization of Aspergillus tamarii Strains From Human Keratomycoses: Molecular Identification, Antifungal Susceptibility Patterns and Cyclopiazonic Acid Producing Abilities

Aspergillus tamarii appears to be an emerging aetiological agent of human keratomycoses in South India. The investigated strains were isolated from six suspected fungal keratitis patients attending a tertiary care eye hospital in Coimbatore (Tamil Nadu, India), and were initially identified by the microscopic examinations of the scrapings and the cultures. Our data suggest that A. tamarii could be easily overlooked when identification is carried out based on morphological characteristics alone, while the sequence analysis of the calmodulin gene can be used successfully to recognize this species accurately. According to the collected clinical data, ocular trauma is a common risk factor for the infection that gradually developed from mild to severe ulcers and could be healed with an appropriate combined antifungal therapy. Antifungal susceptibility testing revealed that A. tamarii strains are susceptible to the most commonly used topical or systemic antifungal agents (i.e., econazole, itraconazole and ketoconazole) except for natamycin. Moreover, natamycin proved to be similarly less effective than the azoles against A. tamarii in our drug interaction tests, as the predominance of indifferent interactions was revealed between natamycin and econazole and between natamycin and itraconazole as well. Four and five isolates of A. tamarii were confirmed to produce cyclopiazonic acid (CPA) in RPMI-1640 – which is designed to mimic the composition of human extracellular fluids – and in yeast extract sucrose (YES) medium, respectively, which is a widely used culture medium for testing mycotoxin production. Although a ten times lower mycelial biomass was recorded in RPMI-1640 than in YES medium, the toxin contents of the samples were of the same order of magnitude in both types of media. There might be a relationship between the outcome of infections and the toxigenic properties of the infecting fungal strains. However, this remains to be investigated in the future.

Stereoselective Synthesis and Investigation of Isopulegol-Based Chiral Ligands

A library of isopulegol-based bi-, tri- and tetrafunctional chiral ligands has been developed from commercially available (−)-isopulegol and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. Michael addition of primary amines towards α-methylene-γ-butyrolactone, followed by reduction, was accomplished to provide aminodiols in highly stereoselective transformations. Stereoselective epoxidation of (+)-neoisopulegol, derived from natural (−)-isopulegol, and subsequent oxirane ring opening with primary amines afforded aminodiols. The regioselective ring closure of N-substituted aminodiols with formaldehyde was also investigated. Hydroxylation of (+)-neoisopulegol resulted in diol, which was then transformed into aminotriols by aminolysis of its epoxides. Dihydroxylation of (+)-neoisopulegol or derivatives with OsO₄/NMO gave neoisopulegol-based di-, tri- and tetraols in highly stereoselective reactions. The antimicrobial activity of aminodiol and aminotriol derivatives as well as di-, tri- and tetraols was also explored. In addition, structure–activity relationships were examined by assessing substituent effects on the aminodiol and aminotriol systems.

Effect of Sterigmatocystin or Aflatoxin Contaminated Feed on Lipid Peroxidation and Glutathione Redox System and Expression of Glutathione Redox System Regulatory Genes in Broiler Chicken

Authors studied the effect of sterigmatocystin from infected corn (STC), purified sterigmatocystin (PSTC), and aflatoxin B1 from infected corn (AFB1) on lipid peroxidation and glutathione redox parameters, including the expression of their encoding genes in a sub-chronic (14 days) trial. A total of 144 three-week-old cockerels was divided into four experimental groups (n = 36 in each). Control feed was contaminated with STC or PSTC (1590 µg STC/kg or 1570.5 µg STC/kg feed), or with AFB1 (149.1 µg AFB1/kg feed). Six birds from each group were sampled at day 1, 2, 3, 7 and 14 of mycotoxin exposure. As parameters of lipid peroxidation, conjugated dienes (CD) and trienes (CT) were measured in the liver, while malondialdehyde (MDA) concentration was determined in blood plasma, red blood cell hemolysate and liver. Reduced glutathione (GSH) concentration and glutathione peroxidase (GPx) activity were determined in the same samples, and expression of glutathione peroxidase 4 (GPX4), glutathione synthetase (GSS) and glutathione reductase (GSR) genes was measured by RT-PCR in the liver. STC, PSTC or AFB1 caused a slight, but not significant, increase in CD and CT levels; however, in the case of MDA, no increase was found in the liver. Glutathione redox system was activated in the liver by AFB1, but less markedly by STC/PSTC. PSTC and AFB1 resulted in a higher expression of GPX4, while GSS expression was down-regulated by AFB1 on day 1, but up-regulated by STC on day 2 and by both mycotoxins on day 7. However, on day 14, GSS expression was down-regulated by PSTC. Expression of GSR was low on day 1 in AFB1 and PSTC groups, but later it was up-regulated by AFB1. The observed changes regarding gene expression strengthen the hypothesis that the mild oxidative stress, caused by the applied STC doses, activates the glutathione redox system of broiler chickens.

Structural Diversity and Bioactivities of Peptaibol Compounds From the Longibrachiatum Clade of the Filamentous Fungal Genus Trichoderma

This study examined the structural diversity and bioactivity of peptaibol compounds produced by species from the phylogenetically separated Longibrachiatum Clade of the filamentous fungal genus Trichoderma, which contains several biotechnologically, agriculturally and clinically important species. HPLC-ESI-MS investigations of crude extracts from 17 species of the Longibrachiatum Clade (T. aethiopicum, T. andinense, T. capillare, T. citrinoviride, T. effusum, T. flagellatum, T. ghanense, T. konilangbra, T. longibrachiatum, T. novae-zelandiae, T. pinnatum, T. parareesei, T. pseudokoningii, T. reesei, T. saturnisporum, T. sinensis, and T. orientale) revealed several new and recurrent 20-residue peptaibols related to trichobrachins, paracelsins, suzukacillins, saturnisporins, trichoaureocins, trichocellins, longibrachins, hyporientalins, trichokonins, trilongins, metanicins, trichosporins, gliodeliquescins, alamethicins and hypophellins, as well as eight 19-residue sequences from a new subfamily of peptaibols named brevicelsins. Non-ribosomal peptide synthetase genes were mined from the available genome sequences of the Longibrachiatum Clade. Their annotation and product prediction were performed in silico and revealed full agreement in 11 out of 20 positions regarding the amino acids predicted based on the signature sequences and the detected amino acids incorporated. Molecular dynamics simulations were performed for structural characterization of four selected peptaibol sequences: paracelsins B, H and their 19-residue counterparts brevicelsins I and IV. Loss of position R6 in brevicelsins resulted in smaller helical structures with higher atomic fluctuation for every residue than the structures formed by paracelsins. We observed the formation of highly bent, almost hairpin-like, helical structures throughout the trajectory, along with linear conformation. Bioactivity tests were performed on the purified peptaibol extract of T. reesei on clinically and phytopathologically important filamentous fungi, mammalian cells, and Arabidopsis thaliana seedlings. Porcine kidney cells and boar spermatozoa proved to be sensitive to the purified peptaibol extract. Peptaibol concentrations ≥0.3 mg ml⁻¹ deterred the growth of A. thaliana. However, negative effects to plants were not detected at concentrations below 0.1 mg ml⁻¹, which could still inhibit plant pathogenic filamentous fungi, suggesting that those peptaibols reported here may have applications for plant protection.

Separation and Purification of Aflatoxins by Centrifugal Partition Chromatography

Aflatoxins are mycotoxins that are produced by several species of filamentous fungi. In the European Union, the concentration limits for this group of mycotoxins in food and feed products are very low (on the order of parts per billion). Thus, relatively high amounts of these substances in their pure forms are required as reference standards. Chromatographic techniques based on solid stationary phases are generally used to purify these molecules; however, liquid–liquid chromatographic separations may be a promising alternative. Therefore, this study proposes a liquid–liquid chromatographic method for the separation of four aflatoxins and impurities. To optimise the method, numerous biphasic solvent systems (chloroform-, acetone- and acetic acid-based systems) were tested and evaluated in terms of their effectiveness at partitioning aflatoxins; the toluene/acetic acid/water (30:24:50, v/v/v/%) system was found to be the most efficient for application in centrifugal partition chromatographic instrument. Using liquid–liquid instrumental separation, the four aflatoxins, namely B₁ (400 mg), B₂ (34 mg), G₁ (817 mg) and G₂ (100 mg), were successfully isolated with 96.3%–98.2% purity from 4.5 L of Aspergillus parasiticus fermented material in a 250 mL centrifugal partition chromatography column. The identities and purities of the purified components were confirmed, and the performance parameters of each separation step and the whole procedure was determined. The developed method could be effectively used to purify aflatoxins for analytical applications.

Host metabolite producing endophytic fungi isolated from Hypericum perforatum

In the present study, endophytic fungi have been isolated from various parts of the medicinal herb Hypericum perforatum (St. John’s Wort), which is known as a source of medically important metabolites. The isolated strains were cultured in liquid media and their ability to synthesize hypericin, the secondary metabolite of the host and its suspected precursor, emodin was tested analyzing the extracts of the fermentation broth and the mycelia. The HPLC-UV analysis of the chloroform/methanol extracts of the mycelia revealed that three isolates were able to produce emodin (SZMC 23771, 19.9 ng/mg; SZMC 23772, 20.8 ng/mg; SZMC 23769, 427.9 ng/mg) and one of them also could synthesize hypericin (SZMC 23769, 320.4 ng/mg). These results were also confirmed via UHPLC-HRMS technique both in full scan and MS/MS mode. The strains producing only emodin belong to the section Alternata of the genus Alternaria, while the isolate producing both metabolites was identified as Epicoccum nigrum. The mycelial extracts of E. nigrum and the Alternaria sp. SZMC 23772 showed higher inhibitory activities in the antimicrobial tests against the six selected bacteria compared to the hypericin and emodin standards in the applied concentration (100 μg/mL), while in case of the Alternaria sp. SZMC 23771 lower inhibition activities were observed on Staphylococcus aureus and Streptomyces albus than the pure compounds.

Aflatoxin production and in vitro toxicity of Aspergilli section Flavi isolated from air samples collected from different environments

Aspergilli section Flavi, originally isolated from air samples collected from inhabited apartments (AP), unoccupied basements (BS), and processing facilities of a grain mill (GM), were analyzed for their potential to produce aflatoxin B₁ (AFB₁) on solid media. The isolates were further characterized with regard to their cytotoxic, genotoxic, and pro-inflammatory properties in vitro. Aspergilli were identified based on partial calmodulin (CaM) gene sequencing; the producing capacities of isolates were analyzed by HPLC/FLD and confirmed by genes in biosynthesis (aflR, norA, omtA). In the grain mill, the Aspergilli section Flavi (up to 1.3 × 10⁶ cfu/m³) dominated by AFB₁-producing Aspergillus flavus (71%, 4.5-5254 ng/ml) which showed a serious health risk for workers. Living environments were not relevant sources of exposure. After 24 h, AFB₁ (1-100 μmol/l) reduced cell viability (MTT test) in both A549 cells and THP-1 macrophage-like cells without reaching IC₅₀. In A549 cells, the extract of the AFB₁-producing A. flavus significantly decreased cell viability but not below 50%. THP-1 macrophage-like cells were more sensitive to both extracts, but IC₅₀ was obtained only for the AFB₁-producing strain (0.37 mg/ml; AFB₁ 2.78 μmol/l). AFB₁ (1 and 10 μmol/l) induced significant DNA damage (tail intensity, alkaline comet assay) in A549 cells in contrast to Aspergilli extracts. AFB₁ elevated IL-6 and IL-8, while Aspergilli extracts increased IL-1β, TNF-α, and IL-17 release in THP-1 macrophages (ELISA). Chronic exposure to AFB₁ and/or other metabolites in airborne A. flavus from occupational environments may stimulate epithelial damage of airways accompanied by lowered macrophage viability.

Salicylic acid-induced ROS production by mitochondrial electron transport chain depends on the activity of mitochondrial hexokinases in tomato (Solanum lycopersicum L.)

The growth regulator, salicylic acid (SA) plays an important role in the induction of cell death in plants. Production of reactive oxygen species (ROS) by mitochondrial electron transport chain (mtETC), cytochrome c (cyt c) release from mitochondria and loss of mitochondrial integrity can be observed during cell death execution in plant tissues. The aim of this work was to study the putative role of hexokinases (HXKs) in the initiation of cell death using tomato (Solanum lycopersicum L.) leaves and mitochondria isolated from plants exposed to a sublethal, 0.1 mM and a cell death-inducing, 1 mM concentrations of SA. Both treatments enhanced ROS and nitric oxide (NO) production in the leaves, which contributed to a concentration-dependent loss of membrane integrity. Images prepared by transmission electron microscopy showed swelling and disorganisation of mitochondrial cristae and vacuolization of mitochondria after SA exposure. Using post-embedding immunohistochemistry, cyt c release from mitochondria was also detected after 1 mM SA treatment. Both SA treatments decreased the activity and transcript levels of HXKs in the leaves and the total mtHXK activity in the mitochondrial fraction. The role of mitochondrial hexokinases (mtHXKs) in ROS and NO production of isolated mitochondria was investigated by the addition of HXK substrate, glucose (Glc) and a specific HXK inhibitor, N-acetylglucosamine (NAG) to the mitochondrial suspension. Both SA treatments enhanced ROS production by mtETC in the presence of succinate and ADP, which was slightly inhibited by Glc and increased significantly by NAG in control and in 0.1 mM SA-treated mitochondria. These changes were not significant at 1 mM SA, which caused disorganisation of mitochondrial membranes. Thus the inhibition of mtHXK activity can contribute to the mitochondrial ROS production, but it is not involved in NO generation in SA-treated leaf mitochondria suggesting that SA can promote cell death by suppressing mtHXK transcription and activity.

Tripleurin XIIc: Peptide Folding Dynamics in Aqueous and Hydrophobic Environment Mimic Using Accelerated Molecular Dynamics

Peptaibols are a special class of fungal peptides with an acetylated N-terminus and a C-terminal 1,2-amino alcohol along with non-standard amino acid residues. New peptaibols named tripleurins were recently identified from a strain of the filamentous fungal species Trichoderma pleuroti, which is known to cause green mould disease on cultivated oyster mushrooms. To understand the mode of action of these peptaibols, the three-dimensional structure of tripleurin (TPN) XIIc, an 18-mer peptide, was elucidated using an enhanced sampling method, accelerated MD, in water and chloroform solvents. Non-standard residues were parameterized by the Restrained Electrostatic Potential (RESP) charge fitting method. The dihedral distribution indicated towards a right-handed helical formation for TPN XIIc in both solvents. Dihedral angle based principal component analysis revealed a propensity for a slightly bent, helical folded conformation in water solvent, while two distinct conformations were revealed in chloroform: One that folds into highly bent helical structure that resembles a beta-hairpin and another with an almost straight peptide backbone appearing as a rare energy barrier crossing event. The hinge-like movement of the terminals was also observed and is speculated to be functionally relevant. The convergence and efficient sampling is addressed using Cartesian PCA and Kullback-Leibler divergence methods.

High-Frequency Occurrence of Surfactin Monomethyl Isoforms in the Ferment Broth of a Bacillus subtilis Strain Revealed by Ion Trap Mass Spectrometry

Surfactins are cyclic lipopeptides consisting of a β-hydroxy fatty acid of various chain length and a peptide ring of seven amino acids linked together by a lactone bridge, forming the cyclic structure of the peptide chain. These compounds are produced mainly by Bacillus species and possess numerous biological effects such as antimicrobial (antiviral, antibacterial, and antifungal) activities. A mixture of surfactins extracted from Bacillus subtilis strain SZMC 6179J was examined by HPLC-ESI-IT-MS technique, enhancing their separation to reveal novel lipopeptide varieties with higher masses and to characterize their structures. During the MS² spectra analyses of their sodiated molecular ions [M + Na]⁺, a previously rarely encountered group of surfactins was detected and two novel types of the group were discovered containing methyl esterified aspartic acid residue in their fifth amino acid position. The relative amounts of these monomethyl isoforms exceeded 35% of the produced surfactin in total. In the m/z value of 1114, all the detected isoforms possessed aspartic acid 4-methyl ester residue in their fifth amino acid position (C17-[Lxx4, AME5], C18-[AME5]), offering an opportunity to separate a pure fraction of the compound and to study its biological activities in the future.

New 19-Residue Peptaibols from Trichoderma Clade Viride

Trichoderma koningiopsis and T. gamsii belong to clade Viride of Trichoderma, the largest and most diverse group of this genus. They produce a wide range of bioactive secondary metabolites, including peptaibols with antibacterial, antifungal, and antiviral properties. The unusual amino acid residues of peptaibols, i.e., α-aminoisobutyric acid (Aib), isovaline (Iva), and the C-terminal 1,2-amino alcohol make them unique among peptides. In this study, the peptaibiomes of T. koningiopsis and T. gamsii were investigated by HPLC-ESI-MS. The examined strains appeared to produce 19-residue peptaibols, most of which are unknown from literature, but their amino acid sequences are similar to those of trikoningins, tricholongins, trichostrigocins, trichorzianins, and trichorzins. A new group of peptaibols detected in T. koningiopsis are described here under the name “Koningiopsin”. Trikoningin KA V, the closest peptaibol compound to the peptaibols produced by these two strains, was selected for structural investigation by short MD simulation, which revealed that many residues show high preference for left handed helix formation. The bioactivity of the peptaibol mixtures produced by T. koningiopsis and T. gamsii was tested on agar plates against bacteria, yeasts, and filamentous fungi. The results revealed characteristic differences in bioactivities towards the different groups of target microorganisms, which can be explained with the differences in their cell wall structures.

Antiproliferative Properties of Newly Synthesized 19-Nortestosterone Analogs Without Substantial Androgenic Activity

19-Nortestosterone C-17 epimers with prominent antiproliferative properties have been previously described. In our present study, five novel 17α-19-nortestosterones (3-7) were synthesized to increase their beneficial biological activities with no associated undesired hormonal effects. The compounds were screened by a viability assay against a panel of human adherent gynecological cancer cell lines. Three of the tested derivatives (3-5) exhibited a remarkable inhibitory effect on the proliferation of HeLa cells with IC₅₀ values lower than that of our reference agent cisplatin (CIS). These three active agents also displayed considerable cancer selectivity as evidenced by their weaker growth inhibitory effect on non-cancerous fibroblast cells compared to CIS. The most potent newly synthesized 17α-chloro derivative (3) was selected for additional experiments in order to characterize its mechanism of action. Since nandrolone (19-nortestosterone, 1) is a structural analog with selective antiproliferative action on cervical carcinoma cells, it was utilized as a positive control in these studies. A lactate dehydrogenase (LDH) assay demonstrated a moderate cytotoxic effect of the test compounds. Cell cycle disturbance and the elevation of the hypodiploid population elicited by the test agents were detected by flow cytometry following propidium staining. The proapoptotic effects of the tested steroids were confirmed by fluorescent microscopy and a caspase-3 activity assay. Treatment-related caspase-9 activation without a substantial change in caspase-8 activity indicates the induction of the intrinsic apoptotic pathway. The selected agents directly influence the rate of tubulin assembly as evidenced by a polymerization assay. Yeast-based reporter gene assay revealed that the androgenic activity of the novel 19-nortestosterone derivative 3 is by multiple orders of magnitude weaker than that of the reference agent 1. Based on the behavior of the examined compounds it can be concluded that a halogen substitution of the 19-nortestosterone scaffold at the 17α position may produce compounds with unique biological activities. The results of the present study support that structurally modified steroids with negligible hormonal activity are a promising basis for the research and development of novel anticancer agents.

Influence of agro-environmental pollutants on a biocontrol strain of Bacillus velezensis

Metal- and pesticide-tolerant biocontrol agents are preferred in integrated pest management, as such strains can be applied in combination with different pesticides. The Bacillus velezensis strain SZMC 6161J proved to be sensitive to copper, nickel, zinc, and cadmium, while manganese elevated its growth. At concentrations higher than 1 mmol L^-1 , zinc and iron inhibited the chymotrypsin-like activity of this strain. In addition, trypsin-like protease and palmitoyl esterase activities were insensitive to all tested heavy metals in the applied concentration range. We studied the effects of some widely used herbicides and fungicides on the growth of this strain. The presence of sulfonylurea herbicides, like bensulfuron-methyl, cinosulfuron, chlorsulfuron, ethoxysulfuron, triasulfuron, and primisulfuron-methyl strongly inhibited the biomass production of the strain even at the concentration of 6.25 mg L^-1 . Glyphosate also inhibited the growth above 30 mg L^-1 . Similarly, contact fungicides like captan, maneb, mancozeb, and thiram resulted in total inhibition at the concentration as low as 6.25 mg L^-1 . Interestingly, the sterol-biosynthesis-inhibiting fungicides imazalil, fenarimol, penconazole, and tebuconazole also proved to be potent inhibitors. Heavy metal- and fungicide-tolerant strains were isolated from the parental strain and their antagonistic abilities were evaluated. There was no substantial difference between the antagonism capability of wild-type strain and the resistant mutants.

Bioactivity-Guided Isolation of Antimicrobial and Antioxidant Metabolites from the Mushroom Tapinella atrotomentosa

Bioassay-guided fractionation of the chloroform extract of Tapinella atrotomentosa led to the isolation of four secondary metabolites 1⁻4. Two of the compounds are lactones—osmundalactone (1) and 5-hydroxy-hex-2-en-4-olide (2)—while 3 and 4 were identified as terphenyl quinones, spiromentins C and B, respectively. The structures of the compounds were established on the basis of NMR and MS spectroscopic analysis. The isolated fungal metabolites were evaluated for their antibacterial activities against several Gram-positive and negative bacteria. In addition, their synergistic effect with cefuroxime against methicillin-resistant Staphylococcus aureus (MRSA) was also evaluated. Compounds 1⁻3 proved to possess significant antibacterial activity against multiresistant Acinetobacter baumannii and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. The investigation of the antioxidant effect of the isolated compounds in DPPH and ORAC assays revealed that spiromentins C (3) and B (4) have remarkable antioxidant activity.

An Organic Solvent-Tolerant Lipase with Both Hydrolytic and Synthetic Activities from the Oleaginous Fungus Mortierella echinosphaera

Lipase enzymes of the oleaginous fungal group Mortierella are rarely studied. However, considering that most commercial lipases are derived from filamentous fungal sources, their investigation can contribute to the cost-effective development of new biotechnological processes. Here, an extracellular lipase with a molecular mass of 30 kDa was isolated from Mortierella echinosphaera CBS 575.75 and characterized. The purified lipase exhibited an optimal p-nitrophenyl palmitate (pNPP)-hydrolyzing activity at 25 °C and pH 6.6-7.0 and proved to be highly stable at temperatures up to 40 °C and under broad pH conditions. The enzyme was active under low temperatures, retaining 32.5% of its activity at 10 °C, and was significantly stable in polar and non-polar organic solvents. The Km, Vmax, and kcat for pNPP were 0.336 mM, 30.4 μM/min, and 45.7 1/min for pNPP and 0.333 mM, 36.9 μM/min, and 55.6 1/min for pNP-decanoate, respectively. The pNPP hydrolysis was inhibited by Hg2+, N-bromosuccinimide, and sodium dodecyl sulfate, while ethylenediaminetetraacetic acid and metal ions, such as Ca2+, Mg2+, Na⁺, and K⁺ enhanced the activity. The purified lipase had non-regioselective activity and wide substrate specificity, showing a clear preference for medium-chained p-nitrophenyl esters. Besides its good transesterification activity, the enzyme appeared as a suitable biocatalyst to operate selective esterification reactions to long-chained alkyl esters. Adsorption to Accurel MP1000 improved the storage stability of the enzyme at 5 °C. The immobilized lipase displayed tolerance to a non-aqueous environment and was reusable for up to five cycles without significant loss in its synthetic and hydrolytic activities. These findings confirm the applicability of both the free and the immobilized enzyme preparations in future research.

Combined genotyping strategy reveals structural differences between Aspergillus flavus lineages from different habitats impacting human health

Aspergillus flavus is a filamentous fungus which is widespread on agricultural products and also able to cause various human diseases. This species is frequently isolated from indoor air as well, furthermore, it is known as a common causal agent of keratomycosis, particularly in subtropical and tropical areas. It is also able to produce aflatoxins, one of the most carcinogenic mycotoxins which are harmful to animals and humans. In this study, 59 A. flavus isolates from four different habitats and 1 A. minisclerotigenes isolate were investigated. The isolates were identified and confirmed at the species level by the sequence analysis of a part of their calmodulin gene. Applying a combined analysis of UP-PCR, microsatellite, and calmodulin sequence data, the four group of isolates formed separate clusters on the phylogenetic tree. Examining the distribution of mating type genes MAT1-1 and MAT1-2, a ratio of approximately 3:1 was determined, and no correlation was found between the carried mating type gene and the aflatoxin production capability. HPLC analysis revealed that none of the examined isolates collected from indoor air or maize in Central Europe were able to produce aflatoxins, while about half of the isolates from India produced these mycotoxins under the test conditions.

Diversity Profile and Dynamics of Peptaibols Produced by Green Mould Trichoderma Species in Interactions with Their Hosts Agaricus bisporus and Pleurotus ostreatus

Certain Trichoderma species are causing serious losses in mushroom production worldwide. Trichoderma aggressivum and Trichoderma pleuroti are among the major causal agents of the green mould diseases affecting Agaricus bisporus and Pleurotus ostreatus, respectively. The genus Trichoderma is well-known for the production of bioactive secondary metabolites, including peptaibols, which are short, linear peptides containing unusual amino acid residues and being synthesised via non-ribosomal peptide synthetases (NRPSs). The aim of this study was to get more insight into the peptaibol production of T. aggressivum and T. pleuroti. HPLC/MS-based methods revealed the production of peptaibols closely related to hypomurocins B by T. aggressivum, while tripleurins representing a new group of 18-residue peptaibols were identified in T. pleuroti. Putative NRPS genes enabling the biosynthesis of the detected peptaibols could be found in the genomes of both Trichoderma species. In vitro experiments revealed that peptaibols are potential growth inhibitors of mushroom mycelia, and that the host mushrooms may have an influence on the peptaibol profiles of green mould agents.

Peptaibol profiles of Iranian Trichoderma isolates

Five Iranian Trichoderma isolates from species T. viride, T. viridescens, T. asperellum, T. longibrachiatum and T. citrinoviride - selected from the Fungal Collection of the Bu Ali Sina University, Hamedan, Iran - were investigated for their peptaibol production. All examined isolates showed remarkable antibacterial activities during the screening of their extracts for peptaibol content with a Micrococcus luteus test culture. HPLC-ESI-IT MS was used for identification and elucidation of the amino acid sequences of peptaibols. The detected peptaibol compounds contain 20 or 18 amino acid residues and belong to the trichobrachin and trichotoxin groups of peptaibols, respectively. T. longibrachiatum and T. citrinoviride produced trichobrachins, while trichotoxins could be detected in T. viride, T. viridescens and T. asperellum. Out of 37 sequences detetermined, 26 proved to be new, yet undescribed compounds, while others were identified as previously reported trichotoxins (trichotoxin A-50s and T5D2) and trichobrachins (longibrachins AI, AII, AIII, BII and BIII). Compounds within the two groups of detected peptaibols differed from each other only by a single or just a few amino acid changes.

Species diversity and cytotoxic potency of airborne sterigmatocystin-producing Aspergilli from the section Versicolores

This study presents the distribution and species diversity of sterigmatocystin-producing Aspergilli from the section Versicolores in the indoor air of apartment-AP, basements-BS and grain mill-GM in Croatia, as well as the cytotoxic potency of isolates. The species comprised 0.7-20% of total airborne fungi detected in the AP, 11-55% in the BS, and 0-2% in the GM. Based on CaM sequences, seven species were identified; dominant were Aspergillus jensenii and Aspergillus creber, followed by Aspergillus protuberus, Aspergillus venenatus, Aspergillus tennesseensis, Aspergillus amoenus, Aspergillus griseoaurantiacus and three undescribed species. All of the identified species produced sterigmatocystin-STC (HPLC/UV-VIS); A. griseoaurantiacus (208.29μg/mL) and A. jensenii (1.192-133.63μg/mL) produced the highest levels, the lowest were detected in A. protuberus and A. tennesseensis (0.117-2.749μg/mL). Lower species diversity was obtained in the GM due to overgrowth with more propulsive fungi. Relatively high STC levels (0.06-2.35μg/g) detected in 52% of GM dust samples confirmed the presence of STC-producers, although this STC cannot be exclusively attributed to Aspergilli (Versicolores). STC and the majority of STC-producing Aspergilli were cytotoxic to human lung A549 cells (IC50 0.9-2.3μg/mL) and THP-1 macrophage-like cells (IC50 0.3-0.6μg/mL) in relatively low concentrations suggesting that humans can be at high risk during chronic exposure.

Ion trap mass spectrometry of surfactins produced by Bacillus subtilis SZMC 6179J reveals novel fragmentation features of cyclic lipopeptides

RATIONALE

Surfactins are mixtures of cyclic lipopeptides consisting of variants of a heptapeptide and a linked β-hydroxy fatty acid with various chain lengths of 13-15 carbon atoms. A lactone bridge between the β-hydroxy functional group of the fatty acid and the carboxy terminal functional component of the peptide chain form their cyclic structures. Such lipopeptides, produced mainly by Bacillus species, possess several remarkable biological effects such as antitumor and antimicrobial activities, some of which are highly promising for utilization in plant disease biocontrol. The strain Bacillus subtilis SZMC 6179J was previously shown to exert significant antifungal properties against various phytopathogenic filamentous fungi; therefore, we characterized the structural features of the surfactins produced by this strain in order to explore the origin of the observed antagonistic effects of this potential biocontrol organism.

METHODS

Bacillus subtilis SZMC 6179J was used to produce surfactins, which were characterized by high-performance liquid chromatography/electrospray ionisation ion trap mass spectrometry (HPLC/ESI-ITMS) techniques after precipitation and extraction steps.

RESULTS

The 26 isoforms separated and identified represent three types of known surfactin variants and a fourth, previously unknown group characterised by the replacement of the leucine residue by valine in position 2. The relative amounts of this newly identified surfactin group were below 1%, and their cyclic structures were closed by C13-C15 hydroxy fatty acids. The structural assessment of the isoforms by MS(2) measurements led to the characterisation and description of a new fragmentation mechanism of surfactins.

CONCLUSIONS

The detected new natural lipoheptapeptide compounds with modified structures have significant potential for biotechnological and biocontrol applications. The complementary ITMS(2) data as well as the described internal fragmentation mechanism obtained from the sodiated surfactin molecules may further facilitate the structural elucidation of cyclic lipopeptides in the future. Copyright © 2016 John Wiley & Sons, Ltd.

The effect of acute ophiobolin A treatment on HO-mediated inflammatory processes

Many microbial and plant-derived metabolites contribute to the production of inflammatory mediators and the expression of pro-inflammatory molecules. Ophiobolin A (OPA) is a fungal secondary metabolite produced by Bipolaris species. The aim of our study was to examine the acute effects of this compound on inflammatory processes. Male Wistar rats were treated with 5% ethanol, 0.01 mg/kg OPA, 0.1 mg/kg OPA and 1.0 mg/kg OPA per os. After 24 h of the administrations, inflammatory mediators such as interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α) and myeloperoxidase (MPO) enzyme as well as heme oxygenase (HO) activity were measured in both plasma and cardiac tissue, along with serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST). We found that OPA caused a significant elevation in the concentrations of IL-6 and TNF-α, increased MPO activity and decreased HO enzyme activity in the plasma. While OPA induces inflammation in the plasma, it did not change the level of inflammatory mediators in the cardiac tissue and the concentrations of serum ALT and AST. Our findings indicate that rapid release of inflammatory mediators by OPA promotes systemic inflammation. However, this acute OPA treatment does not show toxic effects on the cardiac tissue and the concentrations of liver enzymes.