tRNA-derived small RNAs are embedded in the gene regulatory program instructing Drosophila metamorphosis.

A class of noncoding RNAs, referred to as tsRNAs, is emerging with a potential to exert a new layer in gene regulation. These RNAs are breakdown products of tRNAs, either through active processing or passive cleavage or both. Since tRNAs are part of the general machinery for translation, their expression levels and activities are tightly controlled, raising the possibility that their breakdown products, tsRNAs, may provide a link between the overall translational status of a cell to specific changes in gene regulatory network. We hypothesize that Drosophila pupation, being a special developmental stage during which there is a global limitation of nutrients, represents a system in which such a link may readily reveal itself. We show that specific tsRNAs indeed exhibit a dynamic accumulation upon entering the pupal stage. We describe experiments to characterize the mode of tsRNA action and, through the use of such gained knowledge, conduct a genome-wide analysis to assess the functions of dynamically expressed tsRNAs. Our results show that the predicted target genes are highly enriched in biological processes specific to this stage of development including metamorphosis. We further show that tsRNA action is required for successful pupation, providing direct support to the hypothesis that tsRNAs accumulated during this stage are critical to the gene expression program at this stage of development.

Therapeutic effect of iturin A on Candida albicans oral infection and its pathogenic factors.

Candida albicans is responsible for conditions ranging from superficial infections such as oral or vaginal candidiasis to potentially fatal systemic infections. It produces pathogenic factors contributing to its virulence. Iturin A, a lipopeptide derived from Bacillus sp., exhibits a significant inhibitory effect against C. albicans. However, its exact mechanism in mitigating the pathogenic factors of C. albicans remains to be elucidated. This study aimed to explore the influence of iturin A on several pathogenic attributes of C. albicans, including hypha formation, cell membrane permeability, cell adhesion, biofilm formation, and therapeutic efficacy in an oral C. albicans infection model in mice. The minimal inhibitory concentration of iturin A against C. albicans was determined to be 25 µg/mL in both YEPD and RPMI-1640 media. Iturin A effectively inhibited C. albicans hyphal formation, decreased cell viability within biofilms, enhanced cell membrane permeability, and disrupted cell adhesion in vitro. Nonetheless, iturin A did not significantly affect the phospholipase activity or hydrophobicity of C. albicans. A comparative study with nystatin demonstrated the superior therapeutic efficacy of iturin A in a mouse model of oral C. albicans infection, significantly decreasing C. albicans count and inhibiting both fungal hypha formation and tongue surface adhesion. High-dose iturin A treatment (25 µg/mL) in mice had no significant effects on blood indices, tongue condition, or body weight, indicating the potential for iturin A in managing oral infections. This study confirmed the therapeutic potential of iturin A and provided valuable insights for developing effective antifungal therapies targeting C. albicans pathogenic factors.

Multifunctional Gold Nanozyme-Engineered Amphotericin B for Enhanced Antifungal Infection Therapy.

Chronic wounds of significant severity and acute injuries are highly vulnerable to fungal infections, drastically impeding the expected wound healing trajectory. The clinical use of antifungal therapeutic drug is hampered by poor solubility, high toxicity and adverse reactions, thereby necessitating the urgent development of novel antifungal therapy strategy. Herein, this study proposes a new strategy to enhance the bioactivity of small-molecule antifungal drugs based on multifunctional metal nanozyme engineering, using amphotericin B (AmB) as an example. AmB-decorated gold nanoparticles (AmB@AuNPs) are synthesized by a facile one-pot reaction strategy, and the AmB@AuNPs exhibit superior peroxidase (POD)-like enzyme activity, with maximal reaction rates (Vmax) 3.4 times higher than that of AuNPs for the catalytic reaction of H2O2. Importantly, the enzyme-like activity of AuNPs significantly enhanced the antifungal properties of AmB, and the minimum inhibitory concentrations of AmB@AuNPs against Candida albicans (C. albicans) and Saccharomyces cerevisiae (S. cerevisiae) W303 are reduced by 1.6-fold and 50-fold, respectively, as compared with AmB alone. Concurrent in vivo studies conducted on fungal-infected wounds in mice underscored the fundamentally superior antifungal ability and biosafety of AmB@AuNPs. The proposed strategy of engineering antifungal drugs with nanozymes has great potential for enhanced therapy of fungal infections and related diseases.

Diversity and regioselectivity of O-methyltransferases catalyzing the formation of O-methylated flavonoids.

Flavonoids and their methylated derivatives have immense market potential in the food and biomedical industries due to their multiple beneficial effects, such as antimicrobial, anti-inflammatory, and anticancer activities. The biological synthesis of flavonoids and their derivatives is often accomplished via the use of genetically modified microorganisms to ensure large-scale production. Therefore, it is pivotal to understand the properties of O-methyltransferases (OMTs) that mediate the methylation of flavonoids. However, the properties of these OMTs are governed by their: sources, substrate specificity, amino acid residues in the active sites, and the intricate mechanism. In order to obtain a clue for the selection of suitable OMTs for the biosynthesis of a target methylated flavonoid, we made a comprehensive review of the currently reported results, with a particular focus on their comparative regioselectivity for different flavonoid substrates. Additionally, the possible mechanisms for the diversity of this class of enzymes were explored using molecular simulation technology. Finally, major gaps in our understanding and areas for future studies were discussed. The findings of this study may be useful in selecting genes that encode OMTs and designing enzyme-based processes for synthesizing O-methylated flavonoids.

Diversity of fungus-mediated synthesis of gold nanoparticles: properties, mechanisms, challenges, and solving methods.

Fungi-mediated synthesis of Gold nanoparticles (AuNPs) has advantages in: high efficiency, low energy consumption, no need for extra capping and stabilizing agents, simple operation, and easy isolation and purification. Many fungi have been found to synthesize AuNPs inside cells or outside cells, providing different composition and properties of particles when different fungi species or reaction conditions are used. This is good to produce AuNPs with different properties, but may cause challenges to precisely control the particle shape, size, and activities. Besides, low concentrations of substrate and fungal biomass are needed to synthesize small-size particles, limiting the yield of AuNPs in a large scale. To find clues for the development methods to solve these challenges, the reported mechanisms of the fungi-mediated synthesis of AuNPs were summarized. The mechanisms of intracellular AuNPs synthesis are dependent on gold ions absorption by the fungal cell wall via proteins, polysaccharides, or electric absorption, and the reduction of gold ions via enzymes, proteins, and other cytoplasmic redox mediators in the cytoplasm or cell wall. The extracellular synthesis of AuNPs is mainly due to the metabolites outside fungal cells, including proteins, peptides, enzymes, and phenolic metabolites. These mechanisms cause the great diversity of the produced AuNPs in functional groups, element composition, shapes, sizes, and properties. Many methods have been developed to improve the synthesis efficiency by changing: chloroauric acid concentrations, reaction temperature, pH, fungal mass, and reaction time. However, future studies are still required to precisely control the: shape, size, composition, and properties of fungal AuNPs.

Gut microbiota as a potential target for developing anti-fatigue foods.

Fatigue has many negative effects on human health. As such, it is desirable to develop anti-fatigue foods and understand the mechanisms of their action. Based on a comprehensive review of the literature, this article discusses the important roles of gut microbiota in fatigue and anti-fatigue. Studies have shown that an increase in pathogenic bacteria and a decrease in beneficial bacteria co-exist when fatigue is present in both rodents and humans, whereas changes in gut microbiota were reported after intervention with anti-fatigue foods. The roles of gut microbiota in the activities of anti-fatigue foods can also be explained in the causes and the effects of fatigue. Among the causes of fatigue, the accumulation of lactic acid, decrease of energy, and reduction of central nervous system function were related to gut microbiota metabolism. Among the harmful effects of fatigue, oxidative stress, inflammation, and intestinal barrier dysfunction were related to gut microbiota dysbiosis. Furthermore, gut microbiota, together with anti-fatigue foods, can inhibit pathogen growth, convert foods into highly anti-oxidative or anti-inflammatory products, produce short-chain fatty acids, maintain intestinal barrier integrity, inhibit intestinal inflammation, and stimulate the production of neurotransmitters that regulate the central nervous system. Therefore, it is believed that gut microbiota play important roles in the activities of anti-fatigue foods and may provide new insights on the development of anti-fatigue foods.

Potential role of selenium in alleviating obesity-related iron dyshomeostasis.

Obesity is a serious health problem in modern life and increases the risk of many comorbidities including iron dyshomeostasis. In contrast to malnourished anemia, obesity-related iron dyshomeostasis is mainly caused by excessive fat accumulation, inflammation, and disordered gut microbiota. In obesity, iron dyshomeostasis also induces disorders associated with gut microbiota, neurodegenerative injury, oxidative damage, and fat accumulation in the liver. Selenium deficiency is often accompanied by obesity or iron deficiency, and selenium supplementation has been shown to alleviate obesity and overcome iron deficiency. Selenium inhibits fat accumulation and exhibits anti-inflammatory activity. It regulates gut microbiota, prevents neurodegenerative injury, alleviates oxidative damage to the body, and ameliorates hepatic fat accumulation. These effects theoretically meet the requirements for the inhibition of factors underlying obesity-related iron dyshomeostasis. Selenium supplementation may have a potential role in the alleviation of obesity-related iron dyshomeostasis. This review verifies this hypothesis in theory. All the currently reported causes and results of obesity-related iron dyshomeostasis are reviewed comprehensively, together with the effects of selenium. The challenges and strategies of selenium supplementation are also discussed. The findings demonstrate the possibility of selenium-containing drugs or functional foods in alleviating obesity-related iron dyshomeostasis.

Simulated Microgravity Accelerates Alloy Corrosion by Aspergillus sp. via the Enhanced Production of Organic Acids.

Metal corrosion caused by Aspergillus sp. was shown to be significantly enhanced on a space station, but its mechanism is still unknown. To simulate this on earth, the corrosion capability of A. carbonarius on five metal sheets was investigated under simulated microgravity. Also, the effect of metal ions on growth and organic acid production was determined. Results showed that A. carbonarius could corrode all five types of metal, including Ti alloy, aluminum alloy, iron, and aluminum and copper sheet, and the corrosion was intensified under simulated microgravity. Energy dispersive X-ray spectrometry (EDS) analysis showed that metal ions enriched on A. carbonarius spores, especially iron, aluminum ions, and copper ions, indicating that A. carbonarius can use these metal ions. In particular, the content of oxalic acid was significantly increased after A. carbonarius cocultured with five metal materials under simulated microgravity. Al3+, Fe3+, and Cu2+ at the concentration of 0.3 mg/mL and Mg2+ at 0.8 mg/mL significantly promoted the growth and oxalic acid and citric acid production of A. carbonarius and A. niger under normal gravity and simulated microgravity. Comparing the impact of metal ions and metal sheets on the production of organic acids, it can be inferred that oxalic acid may dominate in the corrosion process of A. carbonarius. In summary, molds promoted metal corrosion by producing organic acids, and the released metal ions will further promote the growth of mold and the accumulation of organic acids. This may be an important reason for the intensification of mold corrosion under microgravity. IMPORTANCE The space station and other long-term manned spacecrafts will experience the risk of microbial corrosion, especially mold, which will be harmful to the platform system and astronauts. Aspergillus sp. has been widely reported to produce organic acids that corrode and destroy materials, and the ability of these crafts to fly through space can be significantly affected. Research on the mechanism that causes enhanced corrosion ability of fungi in space stations is important to control their growth. Our research focuses on the interaction between mold and metals. In particular, it is found that metal ions promote mold growth and produce organic acids, thus accelerating mold corrosion of metals. Our results provide a new perspective for the control of fungal corrosion under simulated microgravity.

The capability of Bacillus pseudomycoides from soil to remove Cu(II) in water and prevent it from entering plants.

AIMS: Copper ion is widespread in wastewater and threatens the condition and human health. Micro-organisms have unique advantages to remove heavy-metal ions from water, but are rarely reported in the removal of copper ion. This aims to develop micro-organisms that can remove copper ion in water, characterize their properties and analyse their potential application in practice. METHODS AND RESULTS: Sewage sludge was used as the source to isolate wild bacteria that can remove copper ion in water. The most efficient strain was screened out from 23 obtained isolates, identified as Bacillus pseudomycoides and coded as C6. The properties of C6 in the removal of copper ion in water were investigated in the aspects of reaction conditions, reaction groups, reaction dynamic and the application in oat planting. The reaction at pH 7 within 10 min yielded the highest removal rate of copper ion, 83%. The presence of lead ion in the reaction system could promote the removal rate of copper ion. Carboxyl groups and amidogen of C6 biomass were mainly involved in the removal of copper ion. The removal of copper ion was in accord with single-layer adsorption and Langmuir adsorption isotherm model. In application, C6 biomass reduced the copper content in the oat seedlings grown in copper ion containing water by more than seven times. CONCLUSIONS: B. pseudomycoides C6 can efficiently remove copper ion in water and inhibit it from entering plants. SIGNIFICANCE AND IMPACT OF STUDY: This is the first time to report the capability of B. pseudomycoides to remove copper ion in water, which is also more efficient than the currently reported chemical and biological methods.

Impact of serine and serine synthesis genes on H2S release in Saccharomyces cerevisiae during wine fermentation.

Excessive hydrogen sulfide (H2S) during fermentation causes undesirable sensory properties in wine. In yeast, serine functions as a precursor in the biosynthesis of S-containing compounds, which facilitates H2S consumption. To investigate the effect of serine on H2S release and the underlying mechanism, extracellular and intracellular serine levels were separately increased under fermentation conditions. The results show that, although the abundance of extracellular serine was ineffective in decreasing H2S levels, increased levels of intracellular serine levels from SER1 and SER2 overexpression reduced H2S release through increased consumption of sulfur metabolites. In contrast, SER33 overexpression significantly increased H2S release, and the metabolites and gene expression profile of the sulfur assimilation pathway indicates that SER33 regulated MET17, which mediated H2S release. Our study revealed valuable insights on the relationship between serine levels and H2S release, and may be helpful in understanding the H2S regulation mechanism in yeast during fermentation.

Development of a microecologic product from Lactobacillus rhamnosus based on silica.

BACKGROUND: Probiotics are primarily made into microecologic products for use in the food and feed industries. The freeze-drying technique is widely used in their preparation to maintain their high level of bioactivity. This causes high costs in terms of the energy and time needed. In this study, we developed a method to produce a highly active microecologic product from Lactobacillus rhamnosus using heating and silica. RESULTS: A microecologic product was made successfully from L. rhamnosus using the whole bacterial culture broth, without waste, and using food-grade silica (4.5 mL g-1 ) to absorb water before drying at 37 °C for 8 h. The activity of L. rhamnosus cells was increased significantly by adding water extracts of green tea to the culture medium. The viable amount of L. rhamnosus in the obtained microecologic product was 9.80 × 1010 cfu g-1 with a survival rate of 224.67% in simulated gastric juice for 3 h and 68.2% in simulated intestinal juice for 3 h. The microecologic product treated an intestinal infection by multi-drug-resistant Staphylococcus aureus in mice very efficiently. CONCLUSION: The study developed an economic, eco-friendly, and efficient method for preparing highly active microecologic agents using heating and without waste. © 2022 Society of Chemical Industry.

Antifungal activity of silver nanoparticles synthesized by iturin against Candida albicans in vitro and in vivo.

Candida albicans (C. albicans) is a fungal pathogen that is difficult to cure clinically due to lack of effective antifungal agents with low toxicity. In this study, iturin, a cyclic peptide having wide antifungal spectrum, was used to synthesize nanosilver particles (AgNPs), and a complex of iturin-AgNPs was formed. The antifungal activity of iturin-AgNPs against C. albicans and its mechanisms were tested in vitro. Iturin-AgNPs were also loaded in chitosan (CS) composite dressing and applied to skin wound healing in mice. As results, iturin-AgNPs showed excellent antifungal activity with the minimum inhibitory concentrations (MIC) of 1.25, 2.5, and 5 µg/mL at C. albicans concentrations of 1×105, 1×106, and 1×107 CFU/mL, respectively. The MIC value still kept at 2.5 µg/mL against C. albicans (105 CFU/mL) after 15 regeneration, showing less induction of drug resistance to the pathogenic fungus. The antifungal mechanisms of iturin-AgNPs against C. albicans were identified as the increase of membrane permeability, damage of cell membrane integrity, and leakage of cellular protein and nucleic acids. No toxicity was found for iturin-AgNPs to HaCaT cells at concentrations of lower than 10 µg/mL. In wound healing application, iturin-AgNP CS composite dressing significantly accelerated the healing of C. albicans infected skin wounds at the early 10 days. In conclusion, iturin-AgNPs were developed as an efficient antifungal agent against C. albicans in vitro and in vivo and showed potential application in wound healing promotion.

Key elements and regulation strategies of NRPSs for biosynthesis of lipopeptides by Bacillus.

Lipopeptides are a group of second metabolites of Bacillus and have multiple activities such as inhibiting fungi, bacteria, viruses, and tumors, showing a great potential application in agricultural and biomedical fields. However, low production severely restrained their application in practice. Deeply understanding the key elements of lipopeptide synthesis and the regulatory strategies is essential to target the improvement of lipopeptide production. The synthetic pathways of different lipopeptides are different, but closely and mutually interfered. The loading of fatty acid chains and the extension of peptide chains are two key steps for the synthesis of different lipopeptides by Bacillus. The selection of fatty acid chains, the loading order of amino acids, and the recognition of the final cyclization site are the critical steps to determine the end products of different lipopeptides. In order to find the key elements for precisely directing the formation of different lipopeptides by Bacillus, the key structural elements and possible regulatory strategies that have been reported in the production of different lipopeptides, mainly surfactin, iturin, and fengycin by Bacillus, were summarized and compared. The possible ways to improve the production of different targeted lipopeptides were proposed. KEY POINTS: • The selectivity of fatty acids is determined by specific domains. • The COM domain and the PKS docking domain determine the order of amino acids. • The regulation patterns of different domains for lipopeptide synthesis are different. • The regulation of different lipopeptide products overlaps each other.

Iturin A-like lipopeptides from Bacillus subtilis trigger apoptosis, paraptosis, and autophagy in Caco-2 cells.

This study revealed that iturin A-like lipopeptides produced by Bacillus subtillis induced both paraptosis and apoptosis in heterogeneous human epithelial colorectal adenocarcinoma (Caco-2) cells. Autophagy was simultaneously induced in Caco-2 cells treated with iturin A-like lipopeptides at the early stage and inhibited at the later stage. A western blot analysis showed that the lipopeptides induced apoptosis in Caco-2 cells via a mitochondrial-dependent pathway, as indicated by upregulated expression of the apoptotic genes bax and bad and downregulated expression of the antiapoptotic gene bcl-2. The induction of paraptosis in Caco-2 cells was indicated by the occurrence of many cytoplasmic vacuoles accompanied by endoplasmic reticulum (ER) dilatation and mitochondrial swelling and dysfunction. ER stress also occurred with significant increases in reactive oxygen species and Ca2+ levels in cells. Autophagy was detected by a transmission electron microscopy analysis and by upregulated expression of LC3-II and downregulated expression of LC3-I. The inhibition of autophagy at the later stage was shown by upregulated expression of p62. This study revealed the capability of iturin A-like B. subtilis lipopeptides to simultaneously execute antitumor potential via multiple pathways.

Clinostat Rotation Affects Metabolite Transportation and Increases Organic Acid Production by Aspergillus carbonarius, as Revealed by Differential Metabolomic Analysis.

Contamination by fungi may pose a threat to the long-term operation of the International Space Station because fungi produce organic acids that corrode equipment and mycotoxins that harm human health. Microgravity is an unavoidable and special condition in the space station. However, the influence of microgravity on fungal metabolism has not been well studied. Clinostat rotation is widely used to simulate the microgravity condition in studies carried out on Earth. Here, we used metabolomics differential analysis to study the influence of clinostat rotation on the accumulation of organic acids and related biosynthetic pathways in ochratoxin A (OTA)-producing Aspergillus carbonarius As a result, clinostat rotation did not affect fungal cell growth or colony appearance but significantly increased the accumulation of organic acids, particularly isocitric acid, citric acid, and oxalic acid, and OTA both inside cells and in the medium, as well as resulted in a much higher level of accumulation of some products inside than outside cells, indicating that the transport of these metabolites from the cell to the medium was inhibited. This finding corresponded to the change in the fatty acid composition of cell membranes and the reduced thickness of the cell walls and cell membranes. Amino acid and energy metabolic pathways, particularly the tricarboxylic acid cycle, were influenced the most during clinostat rotation compared to the effects of normal gravity on these pathways.IMPORTANCE Fungi are ubiquitous in nature and have the ability to corrode various materials by producing metabolites. Research on how the space station environment, especially microgravity, affects fungal metabolism is helpful to understand the role of fungi in the space station. This work provides insights into the mechanisms involved in the metabolism of the corrosive fungus Aspergillus carbonarius under simulated microgravity conditions. Our findings have significance not only for preventing material corrosion but also for ensuring food safety, especially in the space environment.

Genomic sequencing, genome-scale metabolic network reconstruction, and in silico flux analysis of the grape endophytic fungus Alternaria sp. MG1.

BACKGROUND: Alternaria sp. MG1, an endophytic fungus isolated from grape, is a native producer of resveratrol, which has important application potential. However, the metabolic characteristics and physiological behavior of MG1 still remains mostly unraveled. In addition, the resveratrol production of the strain is low. Thus, the whole-genome sequencing is highly required for elucidating the resveratrol biosynthesis pathway. Furthermore, the metabolic network model of MG1 was constructed to provide a computational guided approach for improving the yield of resveratrol. RESULTS: Firstly, a draft genomic sequence of MG1 was generated with a size of 34.7 Mbp and a GC content of 50.96%. Genome annotation indicated that MG1 possessed complete biosynthesis pathways for stilbenoids, flavonoids, and lignins. Eight secondary metabolites involved in these pathways were detected by GC-MS analysis, confirming the metabolic diversity of MG1. Furthermore, the first genome-scale metabolic network of Alternaria sp. MG1 (named iYL1539) was reconstructed, accounting for 1539 genes, 2231 metabolites, and 2255 reactions. The model was validated qualitatively and quantitatively by comparing the in silico simulation with experimental data, and the results showed a high consistency. In iYL1539, 56 genes were identified as growth essential in rich medium. According to constraint-based analysis, the importance of cofactors for the resveratrol biosynthesis was successfully demonstrated. Ethanol addition was predicted in silico to be an effective method to improve resveratrol production by strengthening acetyl-CoA synthesis and pentose phosphate pathway, and was verified experimentally with a 26.31% increase of resveratrol. Finally, 6 genes were identified as potential targets for resveratrol over-production by the recently developed methodology. The target-genes were validated using salicylic acid as elicitor, leading to an increase of resveratrol yield by 33.32% and the expression of gene 4CL and CHS by 1.8- and 1.6-fold, respectively. CONCLUSIONS: This study details the diverse capability and key genes of Alternaria sp. MG1 to produce multiple secondary metabolites. The first model of the species Alternaria was constructed, providing an overall understanding of the physiological behavior and metabolic characteristics of MG1. The model is a highly useful tool for enhancing productivity by rational design of the metabolic pathway for resveratrol and other secondary metabolites.

Bifacial effects of engineering tumour cell-derived exosomes on human natural killer cells.

Extracellular vesicles (EVs) are nano vesicular structures that are secreted by almost all kinds of cells. Exosomes are small EVs derived from endosomes, with a diameter between 30-100nm. Tumour-derived exosomes carry many molecules and factors from tumour cells. These exosomes are recognized and taken up by immunocytes. However, tumour-derived exosomes can not only suppress immune cell functions but also help tumours escape immune surveillance in the tumour microenvironment. The present work investigated the effect of exosomes derived from genetical modified K562 cells (GMK cells), which express IL-15, IL-18 and 4-1BBL (TNFSF9) on their surface. The results showed that these GME exosomes, carrying IL-15, IL-18 and 4-1BBL proteins similar to their host cells, could activate NK cells, increase the cytotoxicity of NK cells on some tumour cells in a short treatment (4h) and promote NK cells proliferation. However, with an extended treatment time (48h), these exosomes could inhibite the cytotoxicity of NK cells by inhibiting activated receptor expression on NK cells. These results indicated the bifacial effects of GMK exosomes on NK cells, which will be helpful to explore the possibility of using transformed exosomes as an anti-tumour immune vaccine or a therapeutic tool in future.

Beneficial effects of endophytic fungi colonization on plants.

Due to increasingly limited water resources, diminishing farmland acreage, and potentially negative effects of climate change, an urgent need exists to improve agricultural productivity to feed the ever-growing population. Plants interact with microorganisms at all trophic levels, adapting growth, developmental, and defense responses within a complicated network of community members. Endophytic fungi have been widely reported for their ability to aid in the defense of their host plants. Currently, many reports focus on the application of endophytic fungi with the capability to produce valuable bioactive molecules, while others focus on endophytic fungi as biocontrol agents. Plant responses upon endophytic fungi colonization are also good for the immune system of the plant. In this paper, the possible mechanisms between endophytic fungi and their hosts were reviewed. During long-term evolution, plants have acquired numerous beneficial strategies in response to endophytic fungi colonization. The interaction of endophytic fungi with plants modulates the relationship between plants and both biotic and abiotic stresses. It has previously been reported that this endophytic relationship confers additional defensive mechanisms on the modulation of the plant immune system, as the result of the manipulation of direct antimicrobial metabolites such as alkaloids to indirect phytohormones, jasmonic acid, or salicylic acid. Furthermore, plants have evolved to cope with combinations of stresses and experiments are required to address specific questions related to these multiple stresses. This review summarizes our current understanding of the intrinsic mechanism to better utilize these benefits for plant growth and disease resistance. It contributes new ideas to increase plant fitness and crop productivity.

Synthesis of silver nanoparticles and its contribution to the capability of Bacillus subtilis to deal with polluted waters.

Bacillus subtilis widely exists in environment and shows a capability to deal with heavy metals and dyes in polluted waters by adsorption or biological oxidation and reduction. Little is known about the roles of lipopeptides in this capability of B. subtilis. In this study, we found that the lipopeptides produced by B. subtilis could reduce silver ions to silver nanoparticles (AgNPs) and iturin was identified as the major effective fraction. Furthermore, the synthesized AgNPs was successfully used to catalyze the reduction of organic dyes and reduce Pb2+ contamination in water. The formation of AgNPs was confirmed by the features analyzed by UV-vis spectroscopy, dynamic light scattering, high-resolution transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED). The formed AgNPs showed crystalline, with small size (~ 20 nm) and spherical shape. The biosynthesis of AgNPs was significantly accelerated by UV irradiation. A pH of 10 resulted in the highest formation rate, while pH 9.2 provided the most stability of AgNPs. In mechanisms, tyrosine and the polypeptide were identified as the major groups in iturin-A to form AgNPs via Ar-OH groups. The study revealed that iturin played important roles for the capability of B. subtilis to treat polluted water via a possible way by synthesizing AgNPs and then catalyzing the reduction of organic dyes and reducing the contamination of Pb2+.

Development of a paper-based method to detect Hg2+ in waste water using iturin from Bacillus subtilis.

Colorimetric, fluorescence, and paper-based method were developed to measure the Hg2+ level in water using iturin A, a lipopeptide produced by Bacillus subtilis. Firstly, iturin was used to synthesize highly stable and uniformly sized silver nanoparticles (AgNPs). Secondly, the iturin-AgNPs were found to be highly selective and sensitive to Hg2+. The absorbance of the reaction system showed a good linear correlation with the Hg2+ concentration from 0.5 to 5 mg/L at 450 nm in the UV-Vis spectroscopy detection with the limit of detection (LOD) of 0.5 mg/L. When the reaction system was detected by fluorescence measurement, a good linear relationship was found between the fluorescence intensity and Hg2+ concentration from 0.05 to 0.5 mg/ at 415 nm with the LOD of 0.05 mg/L. Lastly, a paper-based detection method was developed. The developed method was successfully used to detect Hg2+ in contaminated polluted waters and showed acceptable results in terms of sensitivity, selectivity and stability. The paper-based method could distinguish Hg2+ at levels higher than 0.05 mg/L, thereby meeting the guidelines of the effluent quality standard for industries (0.05 mg/L). In summary, this method can be used daily by various industries to monitor the Hg2+ level in effluent water.