Protective role of trehalose during severe oxidative stress caused by hydrogen peroxide and the adaptive oxidative stress response in Candida albicans

Trehalose Biosynthetic Genes Are Involved in the Development and Pathogenesis in the Poplar Canker Fungus Cytospora chrysosperma

Poplar Cytospora canker, caused by Cytospora chrysosperma, is one of the most destructive and widespread poplar diseases worldwide, especially in northern China. However, our current understanding of its pathogenic mechanisms remains limited. Here, we show that trehalose biosynthetic genes, such as trehalose-6-phosphate synthase 1 (CcTps1), trehalose-6-phosphate phosphatase (CcTps2), and the regulatory subunit (CcTps3), play important roles in the development and virulence of C. chrysosperma. The targeted deletion mutants showed reduced trehalose synthesis and were defective in hyphal growth and conidiation. Deletion of any of the three genes attenuated virulence in poplar twigs, and stronger poplar defense responses were triggered after inoculated by the mutants. Additionally, the mutants exhibited increased sensitivity to H2O2 and cell wall stressors. Taken together, the findings suggest that trehalose biosynthetic genes contribute to fungal development, stress responses, and full virulence in C. chrysosperma.

Synthetic biology approaches to improve tolerance of inhibitors in lignocellulosic hydrolysates

Increasing attention is being focused on using lignocellulose for valuable products. Microbial decomposition can convert lignocellulose into renewable biofuels and other high-value bioproducts, contributing to sustainable development. However, the presence of inhibitors in lignocellulosic hydrolysates can negatively affect microorganisms during fermentation. Improving microbial tolerance to these hydrolysates is a major focus in metabolic engineering. Traditional detoxification methods increase costs, so there is a need for cheap and efficient cell-based detoxification strategies. Synthetic biology approaches offer several strategies for improving microbial tolerance, including redox balancing, membrane engineering, omics-guided technologies, expression of protectants and transcription factors, irrational engineering, cell flocculation, and other novel technologies. Advances in molecular biology, high-throughput sequencing, and artificial intelligence (AI) allow for precise strain modification and efficient industrial production. Developing AI-based computational models to guide synthetic biology efforts and creating large-scale heterologous libraries with automation and high-throughput technologies will be important for future research.

Antifungal and anti-biofilm effects of hydrazone derivatives on Candida spp

Worldwide, invasive candidiasis are a burden for the health system due to difficulties to manage patients, to the increasing of the resistance of the current therapeutics and the emergence of naturally resistant species of Candida. In this context, the development of innovative antifungal drugs is urgently needed. During invasive candidiasis, yeast is submitted to many stresses (oxidative, thermic, osmotic) in the human host. In order to resist in this context, yeast develops different strategy, especially the biosynthesis of trehalose. Starting from the 3D structural data of TPS2, an enzyme implicated in trehalose biosynthesis, we identified hydrazone as an interesting scaffold to design new antifungal drugs. Interestingly, our hydrazone derivatives which demonstrate antifungal and anti-biofilm effects on Candida spp., are non-toxic in in vitro and in vivo models (Galleria mellonella).

Transcriptomic meta-analysis to identify potential antifungal targets in Candida albicans

BACKGROUND

Candida albicans is a fungal pathogen causing human infections. Here we investigated differential gene expression patterns and functional enrichment in C. albicans strains grown under different conditions.

METHODS

A systematic GEO database search identified 239 "Candida albicans" datasets, of which 14 were selected after rigorous criteria application. Retrieval of raw sequencing data from the ENA database was accompanied by essential metadata extraction from dataset descriptions and original articles. Pre-processing via the tailored nf-core pipeline for C. albicans involved alignment, gene/transcript quantification, and diverse quality control measures. Quality assessment via PCA and DESeq2 identified significant genes (FDR < = 0.05, log2-fold change > = 1 or <= -1), while topGO conducted GO term enrichment analysis. Exclusions were made based on data quality and strain relevance, resulting in the selection of seven datasets from the SC5314 strain background for in-depth investigation.

RESULTS

The meta-analysis of seven selected studies unveiled a substantial number of genes exhibiting significant up-regulation (24,689) and down-regulation (18,074). These differentially expressed genes were further categorized into 2,497 significantly up-regulated and 2,573 significantly down-regulated Gene Ontology (GO) IDs. GO term enrichment analysis clustered these terms into distinct groups, providing insights into the functional implications. Three target gene lists were compiled based on previous studies, focusing on central metabolism, ion homeostasis, and pathogenicity. Frequency analysis revealed genes with higher occurrence within the identified GO clusters, suggesting their potential as antifungal targets. Notably, the genes TPS2, TPS1, RIM21, PRA1, SAP4, and SAP6 exhibited higher frequencies within the clusters. Through frequency analysis within the GO clusters, several key genes emerged as potential targets for antifungal therapies. These include RSP5, GLC7, SOD2, SOD5, SOD1, SOD6, SOD4, SOD3, and RIM101 which exhibited higher occurrence within the identified clusters.

CONCLUSION

This comprehensive study significantly advances our understanding of the dynamic nature of gene expression in C. albicans. The identification of genes with enhanced potential as antifungal drug targets underpins their value for future interventions. The highlighted genes, including TPS2, TPS1, RIM21, PRA1, SAP4, SAP6, RSP5, GLC7, SOD2, SOD5, SOD1, SOD6, SOD4, SOD3, and RIM101, hold promise for the development of targeted antifungal therapies.

Investigation of ternary Zn-Co-Fe layered double hydroxide as a multifunctional 2D layered adsorbent for moxifloxacin and antifungal disinfection

Layered double hydroxides have recently gained wide interest as promising multifunctional nanomaterials. In this work, a multifunctional ternary Zn-Co-Fe LDH was prepared and characterized using XRD, FTIR, BET, TEM, SEM, and EDX. This LDH showed a typical XRD pattern with a crystallite size of 3.52 nm and a BET surface area of 155.9 m2/g. This LDH was investigated, for the first time, as an adsorbent for moxifloxacin, a common fluoroquinolones antibiotic, showing a maximum removal efficiency and equilibrium time of 217.81 mg/g and 60 min, respectively. Its antifungal activity, for the first time, was investigated against Penicillium notatum, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, and Mucor fungi at various concentrations (1000-1.95 µg/mL). This LDH was found to be effective against a variety of fungal strains, particularly Penicillium and Mucor species and showed zones of inhibition of 19.3 and 21.6 mm for Penicillium and Mucor, respectively, with an inhibition of 85% for Penicillium species and 68.3% for Mucormycosis. The highest antifungal efficacy results were obtained at very low MIC concentrations (33.3 and 62 µg/ml) against Penicillium and Mucor, respectively. The results of this study suggest a promising multifunctional potential of this LDH for water and wastewater treatment and disinfection applications.

Novel Zinc/Silver Ions-Loaded Alginate/Chitosan Microparticles Antifungal Activity against Botrytis cinerea

Addressing the growing need for environmentally friendly fungicides in agriculture, this study explored the potential of biopolymer microparticles loaded with metal ions as a novel approach to combat fungal pathogens. Novel alginate microspheres and chitosan/alginate microcapsules loaded with zinc or with zinc and silver ions were prepared and characterized (microparticle size, morphology, topography, encapsulation efficiency, loading capacity, and swelling behavior). Investigation of molecular interactions in microparticles using FTIR-ATR spectroscopy exhibited complex interactions between all constituents. Fitting to the simple Korsmeyer-Peppas empirical model revealed the rate-controlling mechanism of metal ions release from microparticles is Fickian diffusion. Lower values of the release constant k imply a slower release rate of Zn2+ or Ag+ ions from microcapsules compared to that of microspheres. The antimicrobial potential of the new formulations against the fungus Botrytis cinerea was evaluated. When subjected to tests against the fungus, microspheres exhibited superior antifungal activity especially those loaded with both zinc and silver ions, reducing fungal growth up to 98.9% and altering the hyphal structures. Due to the slower release of metal ions, the microcapsule formulations seem suitable for plant protection throughout the growing season. The results showed the potential of these novel microparticles as powerful fungicides in agriculture.

Trehalose metabolism targeting as a novel strategy to modulate acid tolerance of yeasts and its application in food industry

Some spoilage yeasts are able to develop resistance to commonly used weak-acid preservatives. We studied the trehalose metabolism and its regulation in Saccharomyces cerevisiae in response to propionic acid stress. We show interruption of trehalose synthetic pathway caused the mutant hypersensitive to the acid stress, while its overexpression conferred acid-tolerance to yeast. Interestingly, this acid-tolerance phenotype was largely independent of trehalose but relied on the trehalose synthetic pathway. We demonstrate trehalose metabolism played a vital role in regulation of glycolysis flux and Pi/ATP homeostasis in yeast during acid-adaptation, and the PKA and TOR signaling pathways were involved in regulating trehalose synthesis at transcriptional level. This work confirmed the regulatory function of trehalose metabolism and improved our understanding of molecular mechanism of acid-adaptation of yeast. By exemplifying trehalose metabolism interruption limited the growth of S. cerevisiae exposed to weak acids, and trehalose pathway overexpression conferring acid-resistance to Yarrowia lipolytica enhanced citric acid production, this work provides new insights into the development of efficient preservation strategies and robust organic acid producers.

Ovarian tissue cryopreservation and transplantation: a review on reactive oxygen species generation and antioxidant therapy

Cancer is the leading cause of death worldwide. Fortunately, the survival rate of cancer continues to rise, owing to advances in cancer treatments. However, these treatments are gonadotoxic and cause infertility. Ovarian tissue cryopreservation and transplantation (OTCT) is the most flexible option to preserve fertility in women and children with cancer. However, OTCT is associated with significant follicle loss and an accompanying short lifespan of the grafts. There has been a decade of research in cryopreservation-induced oxidative stress in single cells with significant successes in mitigating this major source of loss of viability. However, despite its success elsewhere and beyond a few promising experiments, little attention has been paid to this key aspect of OTCT-induced damage. As more and more clinical practices adopt OTCT for fertility preservation, it is a critical time to review oxidative stress as a cause of damage and to outline potential ameliorative interventions. Here we give an overview of the application of OTCT for female fertility preservation and existing challenges; clarify the potential contribution of oxidative stress in ovarian follicle loss; and highlight potential ability of antioxidant treatments to mitigate the OTCT-induced injuries that might be of interest to cryobiologists and reproductive clinicians.

G. M, Pandit S, Alghamdi S, Almehmadi M, Allahyani M, Awwad NS, Sharma R. Eco-friendly synthesized nanoparticles as antimicrobial agents: an updated review

Green synthesis of NPs has gained extensive acceptance as they are reliable, eco-friendly, sustainable, and stable. Chemically synthesized NPs cause lung inflammation, heart problems, liver dysfunction, immune suppression, organ accumulation, and altered metabolism, leading to organ-specific toxicity. NPs synthesized from plants and microbes are biologically safe and cost-effective. These microbes and plant sources can consume and accumulate inorganic metal ions from their adjacent niches, thus synthesizing extracellular and intracellular NPs. These inherent characteristics of biological cells to process and modify inorganic metal ions into NPs have helped explore an area of biochemical analysis. Biological entities or their extracts used in NPs include algae, bacteria, fungi, actinomycetes, viruses, yeasts, and plants, with varying capabilities through the bioreduction of metallic NPs. These biosynthesized NPs have a wide range of pharmaceutical applications, such as tissue engineering, detection of pathogens or proteins, antimicrobial agents, anticancer mediators, vehicles for drug delivery, formulations for functional foods, and identification of pathogens, which can contribute to translational research in medical applications. NPs have various applications in the food and drug packaging industry, agriculture, and environmental remediation.

Glucose-enhanced oxidative stress resistance-A protective anticipatory response that enhances the fitness of Candida albicans during systemic infection

Most microbes have developed responses that protect them against stresses relevant to their niches. Some that inhabit reasonably predictable environments have evolved anticipatory responses that protect against impending stresses that are likely to be encountered in their niches-termed "adaptive prediction". Unlike yeasts such as Saccharomyces cerevisiae, Kluyveromyces lactis and Yarrowia lipolytica and other pathogenic Candida species we examined, the major fungal pathogen of humans, Candida albicans, activates an oxidative stress response following exposure to physiological glucose levels before an oxidative stress is even encountered. Why? Using competition assays with isogenic barcoded strains, we show that "glucose-enhanced oxidative stress resistance" phenotype enhances the fitness of C. albicans during neutrophil attack and during systemic infection in mice. This anticipatory response is dependent on glucose signalling rather than glucose metabolism. Our analysis of C. albicans signalling mutants reveals that the phenotype is not dependent on the sugar receptor repressor pathway, but is modulated by the glucose repression pathway and down-regulated by the cyclic AMP-protein kinase A pathway. Changes in catalase or glutathione levels do not correlate with the phenotype, but resistance to hydrogen peroxide is dependent on glucose-enhanced trehalose accumulation. The data suggest that the evolution of this anticipatory response has involved the recruitment of conserved signalling pathways and downstream cellular responses, and that this phenotype protects C. albicans from innate immune killing, thereby promoting the fitness of C. albicans in host niches.

The potential therapeutic impacts of trehalose on cardiovascular diseases as the environmental-influenced disorders: An overview of contemporary findings

Cardiovascular diseases (CVDs) as environmental-influenced disorders, are a major concern and the leading cause of death worldwide. A range of therapeutic approaches has been proposed, including conventional and novel methods. Natural compounds offer a promising alternative for CVD treatment due to their ability to regulate molecular pathways with minimal adverse effects. Trehalose is natural compound and disaccharide with unique biological functions and cardio-protective properties. The cardio-protective effects of trehalose are generated through its ability to induce autophagy, which is mediated by the transcription factors TFEB and FOXO1. The stimulation of TFEB plays a significant role in regulating autophagy genes and autophagosome formation. Activation of FOXO1 through dephosphorylation of Foxo1 and blocking of p38 mitogen-activated protein kinase (p38 MAPK) also triggers autophagy dramatically. Trehalose has been shown to reduce CVD risk factors, including atherosclerosis, cardiac remodeling after a heart attack, cardiac dysfunction, high blood pressure, and stroke. It also reduces structural abnormalities of mitochondria, cytokine production, vascular inflammation, cardiomyocyte apoptosis, and pyroptosis. This review provides a molecular overview of trehalose's cardioprotective functions, including its mechanisms of autophagy and its potential to improve CVD symptoms based on clinical evidence.

Insight into the Antifungal Effects of Propolis and Carnosic Acid—Extension to the Pathogenic Yeast Candida glabrata: New Propolis Fractionation and Potential Synergistic Applications

Fungi have traditionally been considered opportunistic pathogens in primary infections caused by virulent bacteria, protozoan, or viruses. Consequently, antimycotic chemotherapy is clearly less developed in comparison to its bacterial counterpart. Currently, the three main families of antifungals (polyenes, echinocandins, and azoles) are not sufficient to control the enormous increase in life-threatening fungal infections recorded in recent decades. Natural substances harvested from plants have traditionally been utilized as a successful alternative. After a wide screening of natural agents, we have recently obtained promising results with distinct formulations of carnosic acid and propolis on the prevalent fungal pathogens Candida albicans and Cryptococcus neoformans. Here, we extended their use to the treatment against the emerging pathogenic yeast Candida glabrata, which displayed lower susceptibility in comparison to the fungi mentioned above. Taking into account the moderate antifungal activity of both natural agents, the antifungal value of these combinations has been improved through the obtention of the hydroethanolic fractions of propolis. In addition, we have demonstrated the potential clinical application of new therapeutical designs based on sequential pre-treatments with carnosic/propolis mixtures, followed by exposure to amphotericin B. This approach increased the toxic effect induced by this polyene.

A secondary function of trehalose-6-phosphate synthase is required for resistance to oxidative and desiccation stress in Fusarium verticillioides

The disaccharide trehalose has long been recognized for its role as a stress solute, but in recent years some of the protective effects previously ascribed to trehalose have been suggested to arise from a function of the trehalose biosynthesis enzyme trehalose-6-phosphate (T6P) synthase that is distinct from its catalytic activity. In this study, we use the maize pathogenic fungus Fusarium verticillioides as a model to explore the relative contributions of trehalose itself and a putative secondary function of T6P synthase in protection against stress as well as to understand why, as shown in a previous study, deletion of the TPS1 gene coding for T6P synthase reduces pathogenicity against maize. We report that a TPS1-deletion mutant of F. verticillioides is compromised in its ability to withstand exposure to oxidative stress meant to simulate the oxidative burst phase of maize defense and experiences more ROS-induced lipid damage than the wild-type strain. Eliminating T6P synthase expression also reduces resistance to desiccation, but not resistance to phenolic acids. Expression of catalytically-inactive T6P synthase in the TPS1-deletion mutant leads to a partial rescue of the oxidative and desiccation stress-sensitive phenotypes, suggesting the importance of a T6P synthase function that is independent of its role in trehalose synthesis.

Mechanisms of Antifungal Properties of Metal Nanoparticles

The appearance of resistant species of fungi to the existent antimycotics is challenging for the scientific community. One emergent technology is the application of nanotechnology to develop novel antifungal agents. Metal nanoparticles (NPs) have shown promising results as an alternative to classical antimycotics. This review summarizes and discusses the antifungal mechanisms of metal NPs, including combinations with other antimycotics, covering the period from 2005 to 2022. These mechanisms include but are not limited to the generation of toxic oxygen species and their cellular target, the effect of the cell wall damage and the hyphae and spores, and the mechanisms of defense implied by the fungal cell. Lastly, a description of the impact of NPs on the transcriptomic and proteomic profiles is discussed.

Cells Adapt to Resist Fluoride through Metabolic Deactivation and Intracellular Acidification

Fluoride is highly abundant in the environment. Many organisms have adapted specific defense mechanisms against high concentrations of fluoride, including the expression of proteins capable of removing fluoride from cells. However, these fluoride transporters have not been identified in all organisms, and even organisms that express fluoride transporters vary in tolerance capabilities across species, individuals, and even tissue types. This suggests that alternative factors influence fluoride tolerance. We screened for adaptation against fluoride toxicity through an unbiased mutagenesis assay conducted on Saccharomyces cerevisiae lacking the fluoride exporter FEX, the primary mechanism of fluoride resistance. Over 80 independent fluoride-hardened strains were generated, with anywhere from 100- to 1200-fold increased fluoride tolerance compared to the original strain. The whole genome of each mutant strain was sequenced and compared to the wild type. The fluoride-hardened strains utilized a combination of phenotypes that individually conferred fluoride tolerance. These included intracellular acidification, cellular dormancy, nutrient storage, and a communal behavior reminiscent of flocculation. Of particular importance to fluoride resistance was intracellular acidification, which served to reverse the accumulation of fluoride and lead to its excretion from the cell as HF without the activity of a fluoride-specific protein transporter. This transport mechanism was also observed in wild-type yeast through a manual mutation to lower their cytoplasmic pH. The results demonstrate that the yeast developed a protein-free adaptation for removing an intracellular toxicant.

Morphological, Molecular and Metabolic Characterization of the Pigmented Fungus Subramaniula asteroids

Chaetomiaceae fungi are ascosporulating fungi whose importance as human pathogens has been frequently ignored. In the current study, a new isolate of the genus Subramaniula was described. The fungus was isolated from the soil of Wadi Om Nefa'a, Hurghada in the Red Sea Governorate, Egypt. Previously, Subramaniula were misidentified as Papulaspora spp. According to molecular analysis, the fungus was identified as Subramaniula asteroids OP484336. Remarkably, this species has been found among other fungi responsible for keratitis in humans and has been recorded for the first time in Egypt. Analysing the Subramaniula asteroids' metabolic profile was one of the objectives of the current study because little is known about this family's metabolome. The fungal extract's untargeted metabolic profiling was carried out by gas chromatography-mass spectroscopy (GC/MS), 1H and 1H-HSQC nuclear magnetic resonance (NMR) data, and their corresponding databases. In total, fifty-nine metabolites have been reported in the polar and non-polar extracts. The majority of polar metabolites are amino acids and carbohydrates. The non-polar extract's main components were 1-dodecanamine, N,N-dimethyl-, 1-tetradecanamine, N,N-dimethyl-, and 9-octadecenoic acid ethyl ester. The current study is the first to provide a metabolic profile of Subramaniula asteroids, which can be used in chemotaxonomical classification, antifungal drug development, and biological activity investigation of the studied species.

Insight on Photocatalytic and Photoinduced Antimicrobial Properties of ZnO Thin Films Deposited by HiPIMS through Thermal Oxidation

Zinc oxide thin films have been developed through thermal oxidation of Zinc thin films grown by high impulse power magnetron sputtering (HiPIMS). The influence of various sputtering power on thin film structural, morphological, photocatalytic, and antimicrobial properties was investigated. X-ray diffraction (XRD) analysis confirmed that the crystalline phase of ZnO thin films consists of a hexagonal wurtzite structure. Increasing the sputtering power will lead to intrinsic stress on thin films that promote whisker formation. In this study, whiskers were successfully developed on the thin films without precursors/catalysts and not thermally treated over the Zn melting point. This finding showed that the film phase structure and morphology are significantly affected by sputtering power. It was found that ZnO thin films exhibit high photocatalytic performance under UV irradiation (89.91%) of methylene blue after 300 min of irradiation. The antimicrobial activity on ZnO thin films showed significant inhibition activity (p < 0.05) against E. coli, S. aureus, and C. albicans. However, the whisker formation on ZnO thin films is not accessible to enhance photocatalytic and antimicrobial activity. This study demonstrates that the HiPIMS method through the thermal oxidation process can promote a good performance of ZnO thin films as photocatalyst and antimicrobial agents.

Identification of fungal trehalose for the diagnosis of invasive candidiasis by mass spectrometry

The rapidity of the diagnosis of invasive candidiasis (IC) is crucial to allow the early introduction of antifungal therapy that dramatically increases the survival rate of patients. Early diagnosis is unfortunately often delayed because Candida blood culture, the gold standard diagnostic test, is positive in only 50% of cases of IC and takes several days to obtain this result. Complementary non-culture-based methods relying on the detection of Candida cell wall polysaccharides in the serum, β-glucans and mannans, by enzymatic and immunological reagents have been successfully developed to allow a more efficient patients care. We have previously demonstrated that detection of circulating glycans by mass spectrometry could provide a reliable and cost-effective early diagnosis method called MS-DS for Mass Spectrometry of Di-Saccharide. Here, by comparing patient's sera and Candida albicans strains deficient in carbohydrates synthesis, we demonstrate that trehalose derived from fungal metabolism can be specifically targeted by MS-DS to allow early diagnosis. In particular, the use of C. albicans strains deficient in the synthesis of trehalose synthesizing enzymes Tps1 and Tps2 show that MS-DS results were correlated to the metabolism of trehalose. Finally, we demonstrate that the performance of the IC diagnosis can be significantly improved by using high resolution mass spectrometry, which opens new perspectives in the management of the disease.

The involvement of the Candida glabrata trehalase enzymes in stress resistance and gut colonization

Candida glabrata is an opportunistic human fungal pathogen and is frequently present in the human microbiome. It has a high relative resistance to environmental stresses and several antifungal drugs. An important component involved in microbial stress tolerance is trehalose. In this work, we characterized the three C. glabrata trehalase enzymes Ath1, Nth1 and Nth2. Single, double and triple deletion strains were constructed and characterized both in vitro and in vivo to determine the role of these enzymes in virulence. Ath1 was found to be located in the periplasm and was essential for growth on trehalose as sole carbon source, while Nth1 on the other hand was important for oxidative stress resistance, an observation which was consistent by the lower survival rate of the NTH1 deletion strain in human macrophages. No significant phenotype was observed for Nth2. The triple deletion strain was unable to establish a stable colonization of the gastrointestinal (GI) tract in mice indicating the importance of having trehalase activity for colonization in the gut.

Human albumin enhances the pathogenic potential of Candida glabrata on vaginal epithelial cells

The opportunistic pathogen Candida glabrata is the second most frequent causative agent of vulvovaginal candidiasis (VVC), a disease that affects 70–75% of women at least once during their life. However, C. glabrata is almost avirulent in mice and normally incapable of inflicting damage to vaginal epithelial cells in vitro. We thus proposed that host factors present in vivo may influence C. glabrata pathogenicity. We, therefore, analyzed the impact of albumin, one of the most abundant proteins of the vaginal fluid. The presence of human, but not murine, albumin dramatically increased the potential of C. glabrata to damage vaginal epithelial cells. This effect depended on macropinocytosis-mediated epithelial uptake of albumin and subsequent proteolytic processing. The enhanced pathogenicity of C. glabrata can be explained by a combination of beneficial effects for the fungus, which includes an increased access to iron, accelerated growth, and increased adhesion. Screening of C. glabrata deletion mutants revealed that Hap5, a key regulator of iron homeostasis, is essential for the albumin-augmented damage potential. The albumin-augmented pathogenicity was reversed by the addition of iron chelators and a similar increase in pathogenicity was shown by increasing the iron availability, confirming a key role of iron. Accelerated growth not only led to higher cell numbers, but also to increased fungal metabolic activity and oxidative stress resistance. Finally, the albumin-driven enhanced damage potential was associated with the expression of distinct C. glabrata virulence genes. Transcriptional responses of the epithelial cells suggested an unfolded protein response (UPR) and ER-stress responses combined with glucose starvation induced by fast growing C. glabrata cells as potential mechanisms by which cytotoxicity is mediated.Collectively, we demonstrate that albumin augments the pathogenic potential of C. glabrata during interaction with vaginal epithelial cells. This suggests a role for albumin as a key player in the pathogenesis of VVC.

Candida glabrata is the overall second causative species of candidiasis in humans, but little is known about the pathogenicity mechanisms of this yeast. C. glabrata is capable of causing lethal systemic candidiasis mostly in elderly immunocompromised patients, but is also a frequent cause of vulvovaginal candidiasis. These clinical insights suggest that C. glabrata has a high virulence potential, yet little pathogenicity is observed in both in vitro and in vivo infection models. The finding that human albumin, the most abundant protein in the human body, is boosting C. glabrata pathogenicity in vitro provides novel insights into C. glabrata pathogenicity mechanisms and shows that the presence of distinct human factors can have a significant influence on the virulence potential of a pathogenic microbe.

Interesting antifungal drug targets in the central metabolism of Candida albicans

To treat infections caused by Candida albicans, azoles, polyenes, and echinocandins are used. However, resistance occurs against all three, so there is an urgent need for new antifungal drugs with a novel mode of action. Recently, it became clear that central metabolism plays an important role in the virulence of C. albicans. Glycolysis is, for example, upregulated during virulence conditions, whereas the glyoxylate cycle is important upon phagocytosis by host immune cells. These findings indicate that C. albicans adapts its metabolism to the environment for maximal virulence. In this review, we provide an overview of the potency of different central metabolic pathways and their key enzymes as potential antifungal drug targets.

Influence of arginine on the biocontrol efficiency of Metschnikowia citriensis against Geotrichum citri-aurantii causing sour rot of postharvest citrus fruit

This study investigated the effect of arginine (Arg) on the antagonistic activity of Metschnikowia citriensis against sour rot caused by Geotrichum citri-aurantii in postharvest citrus, and evaluated the possible mechanism therein. Arg treatment up-regulated the PUL genes expression, and significantly induced the pulcherriminic acid (PA) production of M. citriensis, which related to the capability of iron depletion of M. citriensis. By comparing the biocontrol effects of Arg-treated and untreated yeast cells, it was found that Arg treatment significantly enhanced the biocontrol efficacy of M. citriensis, and 5 mmol L^-1 Arg exerted the best effect. Additionally, the biofilm formation ability of M. citriensis was greatly enhanced by Arg, and the higher population density of yeast cells in citrus wounds was also observed in Arg treatment groups stored both at 25 °C and 4 °C. Moreover, Arg was shown to function as a cell protectant to elevate antioxidant enzyme activity [including catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX)] and intracellular trehalose content to resist oxidative stress damage, that directly helped to enhance colonization ability of yeasts in fruit wounds. These results suggest the application of Arg is a useful approach to improve the biocontrol performance of M. citriensis.

Trehalose alleviates high-temperature stress in Pleurotus ostreatus by affecting central carbon metabolism

Background

Trehalose, an intracellular protective agent reported to mediate defense against many stresses, can alleviate high-temperature-induced damage in Pleurotus ostreatus. In this study, the mechanism by which trehalose relieves heat stress was explored by the addition of exogenous trehalose and the use of trehalose-6-phosphate synthase 1 (tps1) overexpression transformants.

Results

The results suggested that treatment with exogenous trehalose or overexpression of tps1 alleviated the accumulation of lactic acid under heat stress and downregulated the expression of the phosphofructokinase (pfk) and pyruvate kinase (pk) genes, suggesting an ameliorative effect of trehalose on the enhanced glycolysis in P. ostreatus under heat stress. However, the upregulation of hexokinase (hk) gene expression by trehalose indicated the involvement of the pentose phosphate pathway (PPP) in heat stress resistance. Moreover, treatment with exogenous trehalose or overexpression of tps1 increased the gene expression level and enzymatic activity of glucose-6-phosphate dehydrogenase (g6pdh) and increased the production of both the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH), confirming the effect of trehalose on alleviating oxidative damage by enhancing PPP in P. ostreatus under heat stress. Furthermore, treatment with exogenous trehalose or overexpression of tps1 ameliorated the decrease in the oxygen consumption rate (OCR) caused by heat stress, suggesting a relationship between trehalose and mitochondrial function under heat stress.

Conclusions

Trehalose alleviates high-temperature stress in P. ostreatus by inhibiting glycolysis and stimulating PPP activity. This study may provide further insights into the heat stress defense mechanism of trehalose in edible fungi from the perspective of intracellular metabolism.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01572-9.

Green Synthesis of Silver Nanoparticles Using the Lotus lalambensis Aqueous Leaf Extract and Their Anti-Candidal Activity against Oral Candidiasis

Oral candidiasis is widely spread in both humans and animals, which is caused mainly by Candida albicans. In this study, we aimed to biosynthesize silver nanoparticles (AgNPs) for the first time using the Lotus lalambensis Schweinf leaf extract (L-AgNPs) and investigated their anti-candidal potency alone or in combination with the leaf extract of L. lalambensis (L-AgNPs/LL) against C. albicans. The biosynthesized L-AgNPs were characterized by imaging (transmission electron microscopy, TEM), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results of the disk diffusion method showed the potent synergistic anti-candidal activity of L-AgNPs/LL (24 mm inhibition zone). L-AgNPs/LL completely inhibited the morphogenesis of C. albicans and suppressed the adhesion and the formation of the biofilm of C. albicans by 82.5 and 78.7%, respectively. Further, L-AgNPs/LL inhibited the production of antioxidant enzymes of C. albicans by 80%. SEM and TEM revealed deteriorations in the cell wall ultrastructure in L-AgNPs/LL-treated C. albicans. Interestingly, L-AgNPs/LL showed less than 5% cytotoxicity when examined with either the primary bone marrow derived mesenchymal stem cell (BMSCs) or MCF-7 cell line at MIC values of L-AgNPs/LL. In conclusion, we identified L-AgNPs/LL as a potential biosynthesized-based drug for oral candidiasis in humans and animals.

GC-MS-Based Metabolomics Study of Single- and Dual-Species Biofilms of Candida albicans and Klebsiella pneumoniae

Candida albicans and Klebsiella pneumoniae frequently co-exist within the human host as a complex biofilm community. These pathogens are of interest because their association is also related to significantly increased morbidity and mortality in hospitalized patients. With the aim of highlighting metabolic shifts occurring in the dual-species biofilm, an untargeted GC-MS-based metabolomics approach was applied to single and mixed biofilms of C. albicans and K. pneumoniae. Metabolomic results showed that among the extracellular metabolites identified, approximately 40 compounds had significantly changed relative abundance, mainly involving central carbon, amino acid, vitamin, and secondary metabolisms, such as serine, leucine, arabitol, phosphate, vitamin B6, cyclo-(Phe-Pro), trehalose, and nicotinic acid. The results were related to the strict interactions between the two species and the different microbial composition in the early and mature biofilms.

Impact of the Peptide WMR-K on Dual-Species Biofilm Candida albicans/Klebsiella pneumoniae and on the Untargeted Metabolomic Profile

In recent years, the scientific community has focused on the development of new antibiotics to address the difficulties linked to biofilm-forming microorganisms and drug-resistant infections. In this respect, synthetic antimicrobial peptides (AMPs) are particularly regarded for their therapeutic potential against a broad spectrum of pathogens. In this work, the antimicrobial and antibiofilm activities of the peptide WMR-K towards single and dual species cultures of Candida albicans and Klebsiella pneumoniae were investigated. We found minimum inhibitory concentration (MIC) values for WMR-K of 10 µM for K. pneumoniae and of 200 µM for C. albicans. Furthermore, sub-MIC concentrations of peptide showed an in vitro inhibition of biofilm formation of mono and polymicrobial systems and also a good biofilm eradication even if higher concentrations of it are needed. In order to provide additional evidence for the effect of the examined peptide, a study of changes in extracellular metabolites excreted and/or uptaken from the culture medium (metabolomic footprinting) in the poly-microbial association of C. albicans and K. pneumoniae in presence and absence of WMR-K was performed. Comparing to the untreated dual species biofilm culture, the metabolomic profile of the WMR-K treated culture appears significantly altered. The differentially expressed compounds are mainly related to the primary metabolic pathways, including amino acids, trehalose, pyruvic acid, glycerol and vitamin B6.

Stress priming affects fungal competition - evidence from a combined experimental and modelling study

Priming, an inducible stress defence strategy that prepares an organism for an impending stress event, is common in microbes and has been studied mostly in isolated organisms or populations. How the benefits of priming change in the microbial community context and, vice versa, whether priming influences competition between organisms, remain largely unknown. In this study, we grew different isolates of soil fungi that experienced heat stress in isolation and pairwise competition experiments and assessed colony extension rate as a measure of fitness under priming and non-priming conditions. Based on this data, we developed a cellular automaton model simulating the growth of the ascomycete Chaetomium angustispirale competing against other fungi and systematically varied fungal response traits to explain similarities and differences observed in the experimental data. We showed that competition changes the priming benefit compared with isolated growth and that it can even be reversed depending on the competitor's traits such as growth rate, primeability and stress susceptibility. With this study, we transfer insights on priming from studies in isolation to competition between species. This is an important step towards understanding the role of inducible defences in microbial community assembly and composition.

Antioxidant Effects of Trehalose in an Experimental Model of Type 2 Diabetes

BACKGROUND

Oxidative stress that occurs as a consequence of the imbalance between antioxidant activity and free radicals can contribute in the pathogenesis of metabolic disorders, such as type 2 diabetes mellitus (T2DM). Antioxidant therapies have been proposed as possible approaches to treat and attenuate diabetic complications. The purpose of this study was to evaluate potential antioxidant effects of trehalose on oxidative indices in a streptozotocin (STZ)-induced diabetic rat model.

METHODS

Diabetic rats were divided randomly into five treatment groups (six rats per group). One test group received 45 mg/kg/day trehalose via intraperitoneal injection, and another received 1.5 mg/kg/day trehalose via oral gavage for 4 weeks. Three control groups were also tested including nondiabetic rats as a normal control (NC), a nontreated diabetic control (DC), and a positive control given 200 mg/kg/day metformin. Levels of thiol groups (-SH), and serum total antioxidant capacity were measured between control and test groups. In addition, superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzyme activities were assessed.

RESULTS

In both oral and injection trehalose-treated groups, a marked increase was observed in serum total antioxidant capacity (TAC) (p > 0.05) and thiol groups (-SH) (p < 0.05). Also, SOD and GPx activities were increased after 4 weeks of treatment with trehalose.

CONCLUSION

In conclusion, the present results indicate ameliorative effects of trehalose on oxidative stress, with increase antioxidant enzyme activities in STZ-induced diabetic rats.

HrrSA orchestrates a systemic response to heme and determines prioritization of terminal cytochrome oxidase expression

Heme is a multifaceted molecule. While serving as a prosthetic group for many important proteins, elevated levels are toxic to cells. The complexity of this stimulus has shaped bacterial network evolution. However, only a small number of targets controlled by heme-responsive regulators have been described to date. Here, we performed chromatin affinity purification and sequencing to provide genome-wide insights into in vivo promoter occupancy of HrrA, the response regulator of the heme-regulated two-component system HrrSA of Corynebacterium glutamicum. Time-resolved profiling revealed dynamic binding of HrrA to more than 200 different genomic targets encoding proteins associated with heme biosynthesis, the respiratory chain, oxidative stress response and cell envelope remodeling. By repression of the extracytoplasmic function sigma factor sigC, which activates the cydABCD operon, HrrA prioritizes the expression of genes encoding the cytochrome bc1-aa3 supercomplex. This is also reflected by a significantly decreased activity of the cytochrome aa3 oxidase in the ΔhrrA mutant. Furthermore, our data reveal that HrrA also integrates the response to heme-induced oxidative stress by activating katA encoding the catalase. These data provide detailed insights in the systemic strategy that bacteria have evolved to respond to the versatile signaling molecule heme.

Structure-guided approaches to targeting stress responses in human fungal pathogens

Fungi inhabit extraordinarily diverse ecological niches, including the human body. Invasive fungal infections have a devastating impact on human health worldwide, killing ∼1.5 million individuals annually. The majority of these deaths are attributable to species of Candida, Cryptococcus, and Aspergillus Treating fungal infections is challenging, in part due to the emergence of resistance to our limited arsenal of antifungal agents, necessitating the development of novel therapeutic options. Whereas conventional antifungal strategies target proteins or cellular components essential for fungal growth, an attractive alternative strategy involves targeting proteins that regulate fungal virulence or antifungal drug resistance, such as regulators of fungal stress responses. Stress response networks enable fungi to adapt, grow, and cause disease in humans and include regulators that are highly conserved across eukaryotes as well as those that are fungal-specific. This review highlights recent developments in elucidating crystal structures of fungal stress response regulators and emphasizes how this knowledge can guide the design of fungal-selective inhibitors. We focus on the progress that has been made with highly conserved regulators, including the molecular chaperone Hsp90, the protein phosphatase calcineurin, and the small GTPase Ras1, as well as with divergent stress response regulators, including the cell wall kinase Yck2 and trehalose synthases. Exploring structures of these important fungal stress regulators will accelerate the design of selective antifungals that can be deployed to combat life-threatening fungal diseases.

Antivirulence and avirulence genes in human pathogenic fungi

Opportunistic commensal and environmental fungi can cause superficial to systemic diseases in humans. But how did these pathogens adapt to infect us and how does host-pathogen co-evolution shape their virulence potential? During evolution toward pathogenicity, not only do microorganisms gain virulence genes, but they also tend to lose non-adaptive genes in the host niche. Additionally, virulence factors can become detrimental during infection when they trigger host recognition. The loss of non-adaptive genes as well as the loss of the virulence potential of genes by adaptations to the host has been investigated in pathogenic bacteria and phytopathogenic fungi, where they are known as antivirulence and avirulence genes, respectively. However, these concepts are nearly unknown in the field of pathogenic fungi of humans. We think that this unnecessarily limits our view of human-fungal interplay, and that much could be learned if we applied a similar framework to aspects of these interactions. In this review, we, therefore, define and adapt the concepts of antivirulence and avirulence genes for human pathogenic fungi. We provide examples for analogies to antivirulence genes of bacterial pathogens and to avirulence genes of phytopathogenic fungi. Introducing these terms to the field of pathogenic fungi of humans can help to better comprehend the emergence and evolution of fungal virulence and disease.

Primed to be strong, primed to be fast: modeling benefits of microbial stress responses

Organisms are prone to different stressors and have evolved various defense mechanisms. One such defense mechanism is priming, where a mild preceding stress prepares the organism toward an improved stress response. This improved response can strongly vary, and primed organisms have been found to respond with one of three response strategies: a shorter delay to stress, a faster buildup of their response or a more intense response. However, a universal comparative assessment, which response is superior under a given environmental setting, is missing. We investigate the benefits of the three improved responses for microorganisms with an ordinary differential equation model, simulating the impact of an external stress on a microbial population that is either naïve or primed. We systematically assess the resulting population performance for different costs associated with priming and stress conditions. Our results show that independent of stress type and priming costs, the stronger primed response is most beneficial for longer stress phases, while the faster and earlier responses increase population performance and survival probability under short stresses. Competition increases priming benefits and promotes the early stress response. This dependence on the ecological context highlights the importance of including primed response strategies into microbial stress ecology.

Potential Antifungal Targets Based on Glucose Metabolism Pathways of Candida albicans

In recent years, fungal infections have become a serious health problem. Candida albicans are considered as the fourth most common isolates associated with approximately 40% mortality in bloodstream infections among hospitalized patients. Due to various limitations of classical antifungals used currently, such as limited kinds of drugs, inevitable toxicities, and high price, there is an urgent need to explore new antifungal agents based on novel targets. Generally, nutrient metabolism is involved with fungal virulence, and glucose is one of the important nutrients in C. albicans. C. albicans can obtain and metabolize glucose through a variety of pathways; in theory, many enzymes in these pathways can be potential targets for developing new antifungal agents, and several studies have confirmed that compounds which interfere with alpha-glucosidase, acid trehalase, trehalose-6-phosphate synthase, class II fructose bisphosphate aldolases, and glucosamine-6-phosphate synthase in these pathways do have antifungal activities. In this review, the glucose metabolism pathways in C. albicans, the potential antifungal targets based on these pathways, and some compounds which have antifungal activities by inhibiting several enzymes in these pathways are summarized. We believe that our review will be helpful to the exploration of new antifungal drugs with novel antifungal targets.

Compatible solutes adaptive alterations in Arthrobacter simplex during exposure to ethanol, and the effect of trehalose on the stress resistance and biotransformation performance

Ethanol-tolerant Arthrobacter simplex is desirable since ethanol facilitates hydrophobic substrates dissolution on an industrial scale. Herein, alterations in compatible solutes were investigated under ethanol stress. The results showed that the amount of trehalose and glycerol increased while that of glutamate and proline decreased. The trehalose protectant role was verified and its concentration was positively related to the degree of cell tolerance. otsA, otsB and treS, three trehalose biosynthesis genes in A. simplex, also enhanced Escherichia coli stress tolerance, but the increased tolerance was dependent on the type and level of the stress. A. simplex strains accumulating trehalose showed a higher productivity in systems containing more ethanol and substrate because of better viability. The underlying mechanisms of trehalose were involved in better cell integrity, higher membrane stability, stronger reactive oxygen species scavenging capacity and higher energy level. Therefore, trehalose was a general protectant and the upregulation of its biosynthesis by genetic modification enhanced cell stress tolerance, consequently promoted productivity.

Proteomic analysis of Sporothrix schenckii cell wall reveals proteins involved in oxidative stress response induced by menadione

Sporotrichosis is an emergent subcutaneous mycosis that is a threat to both humans and other animals. Sporotrichosis is acquired by the traumatic implantation of species of the Sporothrix genus. Added to the detoxification systems, pathogenic fungi possess different mechanisms that allow them to survive within the phagocytic cells of their human host during the oxidative burst. These mechanisms greatly depend from the cell wall (CW) since phagocytic cells recognize pathogens through specific receptors associated to the structure. To date, there are no studies addressing the modulation of the expression of S. schenckii CW proteins (CWP) in response to reactive oxygen species (ROS). Therefore, in this work, a proteomic analysis of the CW of S. schenckii in response to the oxidative agent menadione (O₂•^-) was performed. Proteins that modulate their expression were identified which can be related to the fungal survival mechanisms within the phagocyte. Among the up-regulated CWP in response to the oxidative agent, 13 proteins that could be involved in the mechanisms of oxidative stress response in S. schenckii were identified. The proteins identified were thioredoxin1 (Trx1), superoxide dismutase (Sod), GPI-anchored cell wall protein, β-1,3-endoglucanase EglC, glycoside hydrolase (Gh), chitinase, CFEM domain protein, glycosidase crf1, covalently-linked cell wall protein (Ccw), 30 kDa heat shock protein (Hsp30), lipase, trehalase (Treh), fructose-bisphosphate aldolase (Fba1) and citrate synthase (Cs). The identification of CWP that modulates their expression in response to superoxide ion (O₂•^-) in S. schenckii is a useful approach to understand how the fungus defends itself against ROS, in order to evade the phagocytic cells from the host and cause the infection.

LmCBP1, a secreted chitin-binding protein, is required for the pathogenicity of Leptosphaeria maculans on Brassica napus

Leptosphaeria maculans is the causal agent of blackleg disease on Brassica napus. Determining the underlying functions of genes required for pathogenesis is essential for understanding the infection process. A chitin-binding protein (LmCBP1) was discovered as a pathogenicity factor for the infection of B. napus by L. maculans through gene knockout using the CRISPR-Cas9 system. Chitin-binding activity was demonstrated through a chitin-protein binding assay. A secreted signal peptide was detected using a yeast secreted-signal peptide trap assay. An increased expression level during the infection stage was also observed, suggesting that LmCBP1 is a secreted protein. The knockout mutants showed decreased infection on B. napus, with reduced pathogenicity on ten cultivars with/without diverse R genes. The mutants were more sensitive to H₂O₂ compared to wild type L. maculans isolate JN3. This study provides evidence of the virulence of a novel chitin-binding protein LmCBP1 on B. napus through mutants created via the CRISPR-Cas9 system.

Duplication and diversification of trehalase confers evolutionary advantages on lepidopteran insects

Gene duplication provides a major source of new genes for evolutionary novelty and ecological adaptation. However, the maintenance of duplicated genes and their relevance to adaptive evolution has long been debated. Insect trehalase (Treh) plays key roles in energy metabolism, growth, and stress recovery. Here, we show that the duplication of Treh in Lepidoptera (butterflies and moths) is linked with their adaptation to various environmental stresses. Generally, two Treh genes are present in insects: Treh1 and Treh2. We report three distinct forms of Treh in lepidopteran insects, where Treh1 was duplicated into two gene clusters (Treh1a and Treh1b). These gene clusters differ in gene expression patterns, enzymatic properties, and subcellular localizations, suggesting that the enzymes probably underwent sub- and/or neofunctionalization in the lepidopteran insects. Interestingly, selective pressure analysis provided significant evidence of positive selection on duplicate Treh1b gene in lepidopteran insect lineages. Most positively selected sites were located in the alpha-helical region, and several sites were close to the trehalose binding and catalytic sites. Subcellular adaptation of duplicate Treh1b driven by positive selection appears to have occurred as a result of selected changes in specific sequences, allowing for rapid reprogramming of duplicated Treh during evolution. Our results suggest that gene duplication of Treh and subsequent functional diversification could increase the survival rate of lepidopteran insects through various regulations of intracellular trehalose levels, facilitating their adaptation to diverse habitats. This study provides evidence regarding the mechanism by which gene family expansion can contribute to species adaptation through gene duplication and subsequent functional diversification.

The MAPK Hog1 mediates the response to amphotericin B in Candida albicans

The HOG MAP kinase pathway plays a crucial role in the response to different stresses in the opportunistic pathogen Candida albicans. The polyene amphotericin B (AMB) has been reported to trigger oxidative stress in several pathogenic fungi, including C. albicans. In the present work, we have analyzed the role of the MAPK Hog1 in sensing and survival to AMB treatment. Mutants lacking Hog1 are more susceptible to AMB than their parental strains and Hog1 became phosphorylated in the presence of this polyene. A set of mutated versions of Hog1 revealed that both the kinase activity and phosphorylation of Hog1 are required to cope with AMB treatment. Flow cytometry analysis showed that AMB induced intracellular ROS accumulation in both parental and hog1 null mutant strains. In addition, AMB triggered a Hog1-independent synthesis of trehalose. The addition of rotenone to AMB-treated cells improved cell viability, decreased intracellular ROS and prevented intracellular trehalose accumulation, suggesting that AMB-induced ROS is associated to a functional electron transport chain but the presence of rotenone did not impair Hog1 phosphorylation in AMB-treated cells. Our results indicate that Hog1 is necessary during AMB treatment to increase its survival.

Natural cryoprotectants combinations of l-proline and trehalose for red blood cells cryopreservation

Cryopreservation of red blood cells (RBCs) holds great potential benefits for supplying transfusion timely in emergencies. Currently, glycerol is the main cryoprotectant permitted in clinical therapy for RBCs cryopreservation, but its broad application is limited by the toxicity and complex deglycerolization process. Successful cryopreservation of RBCs using more effective materials should be studied to reduce freezing damage, increase biocompatibility, and save processing time. Herein, a simple protocol using natural cryoprotectants combinations of l-proline and trehalose attains a low degree of hemolysis (11.2 ± 2.73%) after thawing compared to glycerol. Furthermore, the morphology of RBCs and the activities of Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase maintain well. Further mechanism study shows that l-proline plays an important role in decreasing the freezing points and inhibiting the growth of ice crystal by permeating into cells during the freezing process. While trehalose works as an inhibitor of ice growth in the freezing process and ice recrystallization in the thawing process. This simple l-proline & trehalose combinations protocol is a promising method to replace current time-consuming and labor-intensive cryopreservation methods of RBCs.

Molecular mechanisms of trehalose in modulating glucose homeostasis in diabetes

Diabetes mellitus is the most prevalent metabolic disorder contributing to significant morbidity and mortality in humans. Many preventative and therapeutic agents have been developed for normalizing glycemic profile in patients with diabetes. In addition to various pharmacologic strategies, many non-pharmacological agents have also been suggested to improve glycemic control in patients with diabetes. Trehalose is a naturally occurring disaccharide which is not synthesized in human but is widely used in food industries. Some studies have provided evidence indicating that it can potentially modulate glucose metabolism and help to stabilize glucose homeostasis in patients with diabetes. Studies have shown that trehalose can significantly modulate insulin sensitivity via at least 7 molecular pathways leading to better control of hyperglycemia. In the current study, we concluded about possible anti-hyperglycemic effects of trehalose suggesting trehalose as a potentially potent non-pharmacological agent for the management of diabetes.

Molecular and physiological basis of Saccharomyces cerevisiae tolerance to adverse lignocellulose-based process conditions

Lignocellulose-based biorefineries have been gaining increasing attention to substitute current petroleum-based refineries. Biomass processing requires a pretreatment step to break lignocellulosic biomass recalcitrant structure, which results in the release of a broad range of microbial inhibitors, mainly weak acids, furans, and phenolic compounds. Saccharomyces cerevisiae is the most commonly used organism for ethanol production; however, it can be severely distressed by these lignocellulose-derived inhibitors, in addition to other challenging conditions, such as pentose sugar utilization and the high temperatures required for an efficient simultaneous saccharification and fermentation step. Therefore, a better understanding of the yeast response and adaptation towards the presence of these multiple stresses is of crucial importance to design strategies to improve yeast robustness and bioconversion capacity from lignocellulosic biomass. This review includes an overview of the main inhibitors derived from diverse raw material resultants from different biomass pretreatments, and describes the main mechanisms of yeast response to their presence, as well as to the presence of stresses imposed by xylose utilization and high-temperature conditions, with a special emphasis on the synergistic effect of multiple inhibitors/stressors. Furthermore, successful cases of tolerance improvement of S. cerevisiae are highlighted, in particular those associated with other process-related physiologically relevant conditions. Decoding the overall yeast response mechanisms will pave the way for the integrated development of sustainable yeast cell-based biorefineries.