Recent Advances in the Detection of Food Toxins Using Mass Spectrometry.

Edibles are the only source of nutrients and energy for humans. However, ingredients of edibles have undergone many physicochemical changes during preparation and storage. Aging, hydrolysis, oxidation, and rancidity are some of the major changes that not only change the native flavor, texture, and taste of food but also destroy the nutritive value and jeopardize public health. The major reasons for the production of harmful metabolites, chemicals, and toxins are poor processing, inappropriate storage, and microbial spoilage, which are lethal to consumers. In addition, the emergence of new pollutants has intensified the need for advanced and rapid food analysis techniques to detect such toxins. The issue with the detection of toxins in food samples is the nonvolatile nature and absence of detectable chromophores; hence, normal conventional techniques need additional derivatization. Mass spectrometry (MS) offers high sensitivity, selectivity, and capability to handle complex mixtures, making it an ideal analytical technique for the identification and quantification of food toxins. Recent technological advancements, such as high-resolution MS and tandem mass spectrometry (MS/MS), have significantly improved sensitivity, enabling the detection of food toxins at ultralow levels. Moreover, the emergence of ambient ionization techniques has facilitated rapid in situ analysis of samples with lower time and resources. Despite numerous advantages, the widespread adoption of MS in routine food safety monitoring faces certain challenges such as instrument cost, complexity, data analysis, and standardization of methods. Nevertheless, the continuous advancements in MS-technology and its integration with complementary techniques hold promising prospects for revolutionizing food safety monitoring. This review discusses the application of MS in detecting various food toxins including mycotoxins, marine biotoxins, and plant-derived toxins. It also explores the implementation of untargeted approaches, such as metabolomics and proteomics, for the discovery of novel and emerging food toxins, enhancing our understanding of potential hazards in the food supply chain.

Screening of the Medicines for Malaria Venture Pandemic Response Box for Discovery of Antivirulent Drug against Pseudomonas aeruginosa.

Resistance development and exhaustion of the arsenal of existing antibacterial agents urgently require an alternative approach toward drug discovery. Herein, we report the screening of Medicines for Malaria Venture (MMV) Pandemic Response Box (PRB) through a cascade developed to streamline the potential compounds with antivirulent properties to combat an opportunistic pathogen, Pseudomonas aeruginosa. To find an agent suppressing the production of P. aeruginosa virulence factors, we assessed the potential of the compounds in PRB with quorum sensing inhibitory activity. Our approach led us to identify four compounds with significant inhibition of extracellular virulence factor production and biofilm formation. This provides an opportunity to expand and redirect the application of these data sets toward the development of a drug with unexplored target-based activity. IMPORTANCE The rise of drug-resistant pathogens as well as overuse and misuse of antibiotics threatens modern medicine as the number of effective antimicrobial drugs steadily decreases. Given the nature of antimicrobial resistance development under intense selective pressure such as the one posed by pathogen-eliminating antibiotics, new treatment options which could slow down the emergence of resistance are urgently needed. Antivirulence therapy aims at suppressing a pathogen's ability to cause disease rather than eliminating it, generating significantly lower selective pressure. Quorum sensing inhibitors are thought to be able to downregulate the production of virulence factors, allowing for smaller amounts of antimicrobials to be used and thus preventing the emergence of resistance. The PRB constitutes an unprecedented opportunity to repurpose new as well as known compounds with cytotoxicity and in vitro absorption, distribution, metabolism and excretion (ADME) profile available, thus shortening the time between compound discovery and medicinal use.

Silver Nanoparticles and Its Mechanistic Insight for Chronic Wound Healing: Review on Recent Progress.

Wounds are structural and functional disruptions of skin that occur because of trauma, surgery, acute illness, or chronic disease conditions. Chronic wounds are caused by a breakdown in the finely coordinated cascade of events that occurs during healing. Wound healing is a long process that split into at least three continuous and overlapping processes: an inflammatory response, a proliferative phase, and finally the tissue remodeling. Therefore, these processes are extensively studied to develop novel therapeutics in order to achieve maximum recovery with minimum scarring. Several growth hormones and cytokines secreted at the site of lesions tightly regulates the healing processes. The traditional approach for wound management has been represented by topical treatments. Metal nanoparticles (e.g., silver, gold and zinc) are increasingly being employed in dermatology due to their favorable effects on healing, as well as in treating and preventing secondary bacterial infections. In the current review, a brief introduction on traditional would healing approach is provided, followed by focus on the potential of wound dressing therapeutic techniques functionalized with Ag-NPs.

Quorum-Sensing Signals from Epibiont Mediate the Induction of Novel Microviridins in the Mat-Forming Cyanobacterial Genus Nostoc.

The regulation of the production of oligopeptides is essential in understanding their ecological role in complex microbial communities, including harmful cyanobacterial blooms. The role of chemical communication between the cyanobacterium and the microbial community harbored as epibionts within its phycosphere is at an initial stage of research, and little is understood about its specificity. Here, we present insight into the role of a bacterial epibiont in regulating the production of novel microviridins isolated from Nostoc, an ecologically important cyanobacterial genus. Microviridins are well-known elastase inhibitors with presumed antigrazing effects. Heterologous expression and identification of specific signal molecules from the epibiont suggest the role of a quorum-sensing-based interaction. Furthermore, physiological experiments show an increase in microviridin production without affecting cyanobacterial growth and photosynthetic activity. Simultaneously, oligopeptides presenting a selective inhibition pattern provide support for their specific function in response to the presence of cohabitant epibionts. Thus, the chemical interaction revealed in our study provides an example of an interspecies signaling pathway monitoring the bacterial flora around the cyanobacterial filaments and the induction of intrinsic species-specific metabolic responses. IMPORTANCE The regulation of the production of cyanopeptides beyond microcystin is essential to understand their ecological role in complex microbial communities, e.g., harmful cyanobacterial blooms. The role of chemical communication between the cyanobacterium and the epibionts within its phycosphere is at an initial stage of research, and little is understood about its specificity. The frequency of cyanopeptide occurrence also demonstrates the need to understand the contribution of cyanobacterial peptides to the overall biological impact of cyanopeptides on aquatic organisms and vertebrates, including humans. Our results shed light on the epibiont control of microviridin production via quorum-sensing mechanisms, and we posit that such mechanisms may be widespread in natural cyanobacterial bloom community regulation.

Draft Genome Sequence of Terrestrial Streptomyces sp. Strain VITNK9, Isolated from Vellore, Tamil Nadu, India, Exhibiting Antagonistic Activity against Fish Pathogens.

We report the draft genome sequence of Streptomyces sp. strain VITNK9, isolated from a soil sample collected in Vellore District (12.9165°N, 79.1325°E), Tamil Nadu, India, with an assembly size of 7,920,076 bp and 72.7% GC content.

Biological and Pharmacological Potential of Xylitol: A Molecular Insight of Unique Metabolism.

Xylitol is a white crystalline, amorphous sugar alcohol and low-calorie sweetener. Xylitol prevents demineralization of teeth and bones, otitis media infection, respiratory tract infections, inflammation and cancer progression. NADPH generated in xylitol metabolism aid in the treatment of glucose-6-phosphate deficiency-associated hemolytic anemia. Moreover, it has a negligible effect on blood glucose and plasma insulin levels due to its unique metabolism. Its diverse applications in pharmaceuticals, cosmetics, food and polymer industries fueled its market growth and made it one of the top 12 bio-products. Recently, xylitol has also been used as a drug carrier due to its high permeability and non-toxic nature. However, it become a challenge to fulfil the rapidly increasing market demand of xylitol. Xylitol is present in fruit and vegetables, but at very low concentrations, which is not adequate to satisfy the consumer demand. With the passage of time, other methods including chemical catalysis, microbial and enzymatic biotransformation, have also been developed for its large-scale production. Nevertheless, large scale production still suffers from high cost of production. In this review, we summarize some alternative approaches and recent advancements that significantly improve the yield and lower the cost of production.

Discovery of Unusual Cyanobacterial Tryptophan-Containing Anabaenopeptins by MS/MS-Based Molecular Networking.

Heterocytous cyanobacteria are among the most prolific sources of bioactive secondary metabolites, including anabaenopeptins (APTs). A terrestrial filamentous Brasilonema sp. CT11 collected in Costa Rica bamboo forest as a black mat, was studied using a multidisciplinary approach: genome mining and HPLC-HRMS/MS coupled with bioinformatic analyses. Herein, we report the nearly complete genome consisting of 8.79 Mbp with a GC content of 42.4%. Moreover, we report on three novel tryptophan-containing APTs; anabaenopeptin 788 (1), anabaenopeptin 802 (2), and anabaenopeptin 816 (3). Furthermore, the structure of two homologues, i.e., anabaenopeptin 802 (2a) and anabaenopeptin 802 (2b), was determined by spectroscopic analysis (NMR and MS). Both compounds were shown to exert weak to moderate antiproliferative activity against HeLa cell lines. This study also provides the unique and diverse potential of biosynthetic gene clusters and an assessment of the predicted chemical space yet to be discovered from this genus.

Isolation, Genomic and Metabolomic Characterization of Streptomyces tendae VITAKN with Quorum Sensing Inhibitory Activity from Southern India.

Streptomyces are among the most promising genera in terms of production ability to biosynthesize a variety of bioactive secondary metabolites with pharmaceutical interest. Coinciding with the increase in genomic sequencing of these bacteria, mining of their genomes for biosynthetic gene clusters (BGCs) has become a routine component of natural product discovery. Herein, we describe the isolation and characterization of a Streptomyces tendae VITAKN with quorum sensing inhibitory (QSI) activity that was isolated from southern coastal part of India. The nearly complete genome consists of 8,621,231bp with a GC content of 72.2%. Sequence similarity networks of the BGCs detected from this strain against the Minimum Information about a Biosynthetic Gene Cluster (MIBiG) database and 3365 BGCs predicted by antiSMASH analysis of publicly available complete Streptomyces genomes were generated through the BiG-SCAPE-CORASON platform to evaluate its biosynthetic novelty. Crude extract analysis using high-performance liquid chromatography connected to high resolution tandem mass spectrometry (HPLC-HRMS/MS) and dereplication through the Global Natural Product Social Molecular Networking (GNPS) online workflow resulted in the identification of cyclic dipeptides (2, 5-diketopiperazines, DKPs) in the extract, which are known to possess QSI activity. Our results highlight the potential of genome mining coupled with LC-HRMS/MS and in silico tools (GNPS) as a valid approach for the discovery of novel QSI lead compounds. This study also provides the biosynthetic diversity of BGCs and an assessment of the predicted chemical space yet to be discovered.

In vitro bioaccessibility of selenoamino acids from selenium (Se)-enriched Chlorella vulgaris biomass in comparison to selenized yeast; a Se-enriched food supplement; and Se-rich foods.

Selenium (Se) is an indispensable microelement in our diet and health issues resulting from deficiencies are well documented. Se-containing food supplements are available on the market including Se-enriched Chlorella vulgaris (Se-Chlorella) which accumulates Se in the form of Se-amino acids (Se-AAs). Despite its popular uses, data about the bioaccessibility of Se-AAs from Se-Chlorella are completely missing. In the present study, gastrointestinal digestion times were optimized and the in vitro bioaccessibility of Se-AAs in Se-Chlorella, Se-yeast, a commercially available Se-enriched food supplement (Se-supplement) and Se rich foods (Se-foods) were compared. Higher bioaccessibility was found in Se-Chlorella (∼49%) as compared to Se-yeast (∼21%), Se-supplement (∼32%) and Se-foods. The methods used in production of Se-Chlorella biomass were also investigated. We found that disintegration increased bioaccessibility whereas the drying process had no effect. Similarly, temperature treatment by microwave oven also increased bioaccessibility whereas boiling water did not.

The intracellular distribution of inorganic carbon fixing enzymes does not support the presence of a C4 pathway in the diatom Phaeodactylum tricornutum.

Diatoms are unicellular algae and important primary producers. The process of carbon fixation in diatoms is very efficient even though the availability of dissolved CO2 in sea water is very low. The operation of a carbon concentrating mechanism (CCM) also makes the more abundant bicarbonate accessible for photosynthetic carbon fixation. Diatoms possess carbonic anhydrases as well as metabolic enzymes potentially involved in C4 pathways; however, the question as to whether a C4 pathway plays a general role in diatoms is not yet solved. While genome analyses indicate that the diatom Phaeodactylum tricornutum possesses all the enzymes required to operate a C4 pathway, silencing of the pyruvate orthophosphate dikinase (PPDK) in a genetically transformed cell line does not lead to reduced photosynthetic carbon fixation. In this study, we have determined the intracellular location of all enzymes potentially involved in C4-like carbon fixing pathways in P. tricornutum by expression of the respective proteins fused to green fluorescent protein (GFP), followed by fluorescence microscopy. Furthermore, we compared the results to known pathways and locations of enzymes in higher plants performing C3 or C4 photosynthesis. This approach revealed that the intracellular distribution of the investigated enzymes is quite different from the one observed in higher plants. In particular, the apparent lack of a plastidic decarboxylase in P. tricornutum indicates that this diatom does not perform a C4-like CCM.

High light acclimation of Chromera velia points to photoprotective NPQ.

It has previously been shown that the long-term treatment of Arabidopsis thaliana with the chloroplast inhibitor lincomycin leads to photosynthetic membranes enriched in antennas, strongly reduced in photosystem II reaction centers (PSII) and with enhanced nonphotochemical quenching (NPQ) (Belgio et al. Biophys J 102:2761-2771, 2012). Here, a similar physiological response was found in the microalga Chromera velia grown under high light (HL). In comparison to cells acclimated to low light, HL cells displayed a severe re-organization of the photosynthetic membrane characterized by (1) a reduction of PSII but similar antenna content; (2) partial uncoupling of antennas from PSII; (3) enhanced NPQ. The decrease in the number of PSII represents a rather unusual acclimation response compared to other phototrophs, where a smaller PSII antenna size is more commonly found under high light. Despite the diminished PSII content, no net damage could be detected on the basis of the Photosynthesis versus irradiance curve and electron transport rates pointing at the excess capacity of PSII. We therefore concluded that the photoinhibition is minimized under high light by a lower PSII content and that cells are protected by NPQ in the antennas.

Valorization of Unconventional Lipids from Microalgae or Tall Oil via a Selective Dual Catalysis One-Pot Approach.

A dual catalysis approach enables selective functionalization of unconventional feedstocks composed of complex fatty acid mixtures with highly unsaturated portions like eicosapentaenoate (20:5) along with monounsaturated compounds. The degree of unsaturation is unified by selective heterogeneous hydrogenation on Pd/γ-Al2O3, complemented by effective activation to a homogeneous carbonylation catalyst [(dtbpx)PdH(L)]+ by addition of diprotonated diphosphine (dtbpxH2)(OTf)2. By this one-pot approach, neat 20:5 as a model substrate is hydrogenated to up to 80% to the monounsaturated analogue (20:1), this is functionalized to the desired C21 α,ω-diester building block with a linear selectivity of over 90%. This catalytic approach is demonstrated to be suitable for crude microalgae oil from Phaeodactylum tricornutum genetically engineered for this purpose, as well as tall oil, an abundant waste material. Both substrates were fully converted with an overall selectivity to the linear α,ω-diester of up to 75%.

Rapid induction of GFP expression by the nitrate reductase promoter in the diatom Phaeodactylum tricornutum.

An essential prerequisite for a controlled transgene expression is the choice of a suitable promoter. In the model diatom Phaeodactylum tricornutum, the most commonly used promoters for trans-gene expression are the light dependent lhcf1 promoters (derived from two endogenous genes encoding fucoxanthin chlorophyll a/c binding proteins) and the nitrate dependent nr promoter (derived from the endogenous nitrate reductase gene). In this study, we investigated the time dependent expression of the green fluorescent protein (GFP) reporter under control of the nitrate reductase promoter in independently genetically transformed P. tricornutum cell lines following induction of expression by change of the nitrogen source in the medium via flow cytometry, microscopy and western blotting. In all investigated cell lines, GFP fluorescence started to increase 1 h after change of the medium, the fastest increase rates were observed between 2 and 3 h. Fluorescence continued to increase slightly for up to 7 h even after transfer of the cells to ammonium medium. The subsequent decrease of GFP fluorescence was much slower than the increase, probably due to the stability of GFP. The investigation of several cell lines transformed with nr based constructs revealed that, also in the absence of nitrate, the promoter may show residual activity. Furthermore, we observed a strong variation of gene expression between independent cell lines, emphasising the importance of a thorough characterisation of genetically modified cell lines and their individual expression patterns.

The role of C4 metabolism in the marine diatom Phaeodactylum tricornutum.

Diatoms are important players in the global carbon cycle. Their apparent photosynthetic affinity for ambient CO(2) is much higher than that of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), indicating that a CO(2)-concentrating mechanism (CCM) is functioning. However, the nature of the CCM, a biophysical or a biochemical C(4), remains elusive. Although (14)C labeling experiments and presence of complete sets of genes for C(4) metabolism in two diatoms supported the presence of C(4), other data and predicted localization of the decarboxylating enzymes, away from Rubisco, makes this unlikely. We used RNA-interference to silence the single gene encoding pyruvate-orthophosphate dikinase (PPDK) in Phaeodactylum tricornutum, essential for C(4) metabolism, and examined the photosynthetic characteristics. The mutants possess much lower ppdk transcript and PPDK activity but the photosynthetic K(1/2) (CO(2)) was hardly affected, thus clearly indicating that the C(4) route does not serve the purpose of raising the CO(2) concentration in close proximity of Rubisco in P. tricornutum. The photosynthetic V(max) was slightly reduced in the mutant, possibly reflecting a metabolic constraint that also resulted in a larger lipid accumulation. We propose that the C(4) metabolism does not function in net CO(2) fixation but helps the cells to dissipate excess light energy and in pH homeostasis.