Heterologous production of (-)-geosmin in Saccharomyces cerevisiae

(-)-Geosmin has high demand in perfumes and cosmetic products for its earthy congenial aroma. The current production of (-)-geosmin is either by distillation of sun-baked soil or by inefficient chemical synthesis because of the presence of multiple chiral centers. Fermentation processes are not viable as the titers of the Streptomyces sp. based processes are low. This work presents an alternative route by the heterologous synthesis of (-)-geosmin in Saccharomyces cerevisiae. The enzyme involved is the bifunctional geosmin synthase that catalyzes the conversion of farnesyl diphosphate to germacradienol and germacradienol to geosmin. This study evaluated the activity of many orthologs of geosmin synthase when expressed heterologously in S. cerevisiae. When the well-characterized CAB41566 from Streptomyces coelicolor origin was tested, germacradienol and germacrene D were detected but no geosmin. Bioinformatic analysis based on high/low identities to N-terminal and C-terminal domains of CAB41566 was carried out to identify different orthologs of geosmin synthase proteins from different bacterial and fungal origins. ADO68918 of Stigmatella aurantiaca origin showed the best activity among the tested orthologs, not only in terms of geosmin production but also an order of magnitude higher total abundance of the products of geosmin synthase as compared to CAB41566. This study successfully demonstrated the production of (-)-geosmin in S. cerevisiae and offers an alternative, sustainable and environment-friendly approach to producing (-)-geosmin.

Exploring Novel 1-Hydroxynaphthalene-2-Carboxanilides Based Inhibitors Against C-Jun N-Terminal Kinases Through Molecular Dynamic Simulation and WaterSwap Analysis

Cancer is a disease of mutation and lifestyle modifications. A large number of normal genes can transform normal cells to cancer cells due to their deregulations including overexpression and loss of expression. Signal transduction is a complex signaling process that involves multiple interactions and different functions. C-Jun N-terminal kinases (JNKs) is an important protein involved in signaling process. JNK mediated pathways can detect, integrate, and amplify various external signals that may cause alterations in gene expression, enzyme activities, and different cellular functions that affect cellular behavior like metabolism, proliferation, differentiation, and cell survival. In this study, we performed molecular docking protocol (MOE) to predict the binding interactions of some known anticancer 1-hydroxynaphthalene-2-carboxanilides candidates. A set of 10 active compounds was retrieved after initial screening on the basis of docking scores, binding energies, and number of interactions and was re-docked in the active site of JNK protein. The results were further validated through molecular dynamics simulation and MMPB/GBSA calculations. The active compounds 4p and 5 k were ranked on top. After computationally exploring interactions of 1-hydroxynaphthalene-2-carboxanilides with JNK protein, we believe compounds 4p and 5 k can serve as potential inhibitors of JNK protein. It is believed that the results of current research would help to develop novel and structurally diverse anticancer compounds that will be useful not only treat cancer but also for the medication for the other diseases caused by protein deregulation.

Volatile sensation: The chemical ecology of the earthy odorant geosmin

Geosmin may be the most familiar volatile compound, as it lends the earthy smell to soil. The compound is a member of the largest family of natural products, the terpenoids. The broad distribution of geosmin among bacteria in both terrestrial and aquatic environments suggests that this compound has an important ecological function, for example, as a signal (attractant or repellent) or as a protective specialized metabolite against biotic and abiotic stresses. While geosmin is part of our everyday life, scientists still do not understand the exact biological function of this omnipresent natural product. This minireview summarizes the current general observations regarding geosmin in prokaryotes and introduces new insights into its biosynthesis and regulation, as well as its biological roles in terrestrial and aquatic environments.

SAR study of piperidine derivatives as inhibitors of 1,4-dihydroxy-2-naphthoate isoprenyltransferase (MenA) from Mycobacterium tuberculosis

The electron transport chain (ETC) in the cell membrane consists of a series of redox complexes that transfer electrons from electron donors to acceptors and couples this electron transfer with the transfer of protons (H+) across a membrane. This process generates proton motive force which is used to produce ATP and a myriad of other functions and is essential for the long-term survival of Mycobacterium tuberculosis (Mtb), the causative organism of tuberculosis (TB), under the hypoxic conditions present within infected granulomas. Menaquinone (MK), an important carrier molecule within the mycobacterial ETC, is synthesized de novo by a cluster of enzymes known as the classic/canonical MK biosynthetic pathway. MenA (1,4-dihydroxy-2-naphthoate prenyltransferase), the antepenultimate enzyme in this pathway, is a verified target for TB therapy. In this study, we explored structure-activity relationships of a previously discovered MenA inhibitor scaffold, seeking to improve potency and drug disposition properties. Focusing our campaign upon three molecular regions, we identified two novel inhibitors with potent activity against MenA and Mtb (IC50 = 13-22 μM, GIC50 = 8-10 μM). These analogs also displayed substantially improved pharmacokinetic parameters and potent synergy with other ETC-targeting agents, achieving nearly complete sterilization of Mtb in combination therapy within two weeks in vivo. These new inhibitors of MK biosynthesis present a promising new strategy to curb the continued spread of TB.

Expression and kinetic analysis of carboxylesterase LmCesA1 from Locusta migratoria

OBJECTIVE

To investigate the biochemical characterization of the carboxylesterase LmCesA1 from Locusta migratoria.

RESULTS

We expressed recombinant LmCesA1 in Sf9 cells by using the Bac-to-bac baculovirus expression system. Enzyme kinetic assays showed that the K_m values of LmCesA1 for α-naphthyl acetate (α-NA) and β-naphthyl acetate (β-NA) were 0.08 ± 0.01 mM and 0.22 ± 0.03 mM, respectively, suggesting that LmCesA1 has a higher affinity for α-NA. LmCesA1 retained its enzymatic activity during incubations at pH 7-10 and at 10-30 °C. In an inhibition experiment, two organophosphate pesticides (malaoxon and malathion) and one pyrethroid pesticide (deltamethrin) showed different inhibition profiles against purified LmCesA1. Recombinant LmCesA1 activity was significantly inhibited by malaoxon in vitro. UPLC analysis showed that no metabolites were detected.

CONCLUSIONS

These results suggest that overexpression of LmCesA1 enhances malathion sequestration to confer malathion tolerance in L. migratoria.

Hydrolase CehA and a Novel Two-Component 1-Naphthol Hydroxylase CehC1C2 are Responsible for the Two Initial Steps of Carbaryl Degradation in Rhizobium sp. X9

Carbaryl is a widely used carbamate pesticide in agriculture. The strain Rhizobium sp. X9 possesses the typical carbaryl degradation pathway in which carbaryl is mineralized via 1-naphthol, salicylate, and gentisate. In this study, we cloned a carbaryl hydrolase gene cehA and a novel two-component 1-naphthol hydroxylase gene cehC1C2. CehA mediates carbaryl hydrolysis to 1-naphthol and CehC1, an FMNH₂ or FADH₂-dependent monooxygenase belonging to the HpaB superfamily, and hydroxylates 1-naphthol in the presence of reduced nicotinamide-adenine dinucleotide (FMN)/flavin adenine dinucleotide (FAD), and the reductase CehC2. CehC1 has the highest amino acid similarity (58%) with the oxygenase component of a two-component 4-nitrophenol 2-monooxygenase, while CehC2 has the highest amino acid similarity (46%) with its reductase component. CehC1C2 could utilize both FAD and FMN as the cofactor during the hydroxylation, although higher catalytic activity was observed with FAD as the cofactor. The optimal molar ratio of CehC1 to CehC2 was 2:1. The K_m and K_cat/K_m values of CehC1 for 1-naphthol were 74.71 ± 16.07 μM and (8.29 ± 2.44) × 10^-4 s^-1·μM^-1, respectively. Moreover, the enzyme activities and substrate spectrum between CehC1C2 and previously reported 1-naphthol hydroxylase McbC were compared. The results suggested that McbC had a higher 1-naphthol hydroxylation activity, while CehC1C2 had a broader substrate spectrum.

New Microporous Lanthanide Organic Frameworks. Synthesis, Structure, Luminescence, Sorption, and Catalytic Acylation of 2-Naphthol

New metal-organic frameworks (MOF) with lanthanum(III), cerium(III), neodymium(III), europium(III), gadolinium(III), dysprosium(III), and holmium(III)] and the ligand precursor 1,3,5-tris(4-carboxyphenyl)-2,4,6-trimethylbenzene (H3L) were synthesized under solvothermal conditions. Single crystal x-ray analysis confirmed the formation of three-dimensional frameworks of [LnL(H2O)2]n·xDMF·yH2O for Ln = La, Ce, and Nd. From the nitrogen sorption experiments, the compounds showed permanent porosity with Brunauer-Emmett-Teller (BET) surface areas of about 400 m2/g, and thermal stability up to 500 °C. Further investigations showed that these Ln-MOFs exhibit catalytic activity, paving the way for potential applications within the field of catalysis.

The impact of phenanthrene on membrane phospholipids and its biodegradation by Sphingopyxis soli

The direct interactions of bacterial membranes and polycyclic aromatic hydrocarbons (PAHs) strongly influence the biological processes, such as metabolic activity and uptake of substrates due to changes in membrane lipids. However, the elucidation of adaptation mechanisms as well as membrane phospholipid alterations in the presence of phenanthrene (PHE) from α-proteobacteria has not been fully explored. This study was conducted to define the degradation efficiency of PHE by Sphingopyxis soli strain KIT-001 in a newly isolated from Jeonju river sediments and to characterize lipid profiles in the presence of PHE in comparison to cells grown on glucose using quantitative lipidomic analysis. This strain was able to respectively utilize 1-hydroxy-2-naphthoic acid and salicylic acid as sole carbon source and approximately 90% of PHE (50 mg/L) was rapidly degraded via naphthalene route within 1 day incubation. In the cells grown on PHE, strain KIT-001 appeared to dynamically change profiles of metabolite and lipid in comparison to cells grown on glucose. The levels of primary metabolites, phosphatidylethanolamines (PE), and phosphatidic acids (PA) were significantly decreased, whereas the levels of phosphatidylcholines (PC) and phosphatidylglycerols (PG) were significantly increased. The adaptation mechanism of Sphingopyxis sp. regarded mainly the accumulation of bilayer forming lipids and anionic lipids to adapt more quickly under restricted nutrition and toxicity condition. Hence, these findings are conceivable that strain KIT-001 has a good adaptive ability and biodegradation for PHE through the alteration of phospholipids, and will be helpful for applications for effective bioremediation of PAHs-contaminated sites.

Non-bioavailability of extracellular 1-hydroxy-2-naphthoic acid restricts the mineralization of phenanthrene by Rhodococcus sp. WB9

Rhodococcus sp. WB9, a strain isolated from polycyclic aromatic hydrocarbons contaminated soil, degraded phenanthrene (PHE, 100 mg L^-1) completely within 4 days. 18 metabolites were identified during PHE degradation, including 5 different hydroxyphenanthrene compounds resulted from multiple routes of initial monooxygenase attack. Initial dioxygenation dominantly occurred on 3,4-C positions, followed by meta-cleavage to form 1-hydroxy-2-naphthoic acid (1H2N). More than 95.2% of 1H2N was transported to and kept in extracellular solution without further degradation. However, intracellular 1H2N was converted to 1,2-naphthalenediol that was branched to produce salicylate and phthalate. Furthermore, 131 genes in strain WB9 genome were related to aromatic hydrocarbons catabolism, including the gene coding for salicylate 1-monooxygenase that catalyzed the oxidation of 1H2N to 1,2-naphthalenediol, and complete gene sets for the transformation of salicylate and phthalate toward tricarboxylic acid (TCA) cycle. Metabolic and genomic analyses reveal that strain WB9 has the ability to metabolize intracellular 1H2N to TCA cycle intermediates, but the extracellular 1H2N can't enter the cells, restricting 1H2N bioavailability and PHE mineralization.

A comparative study of acetylcholinesterase and general-esterase activity assays using different substrates, in vitro and in vivo exposures and model organisms

Acetylcholinesterase (AChE) and general-esterase (GE) activities are important to understand detoxification processes of xenobiotics. The assays to quantify them have employed different substrates, inhibitors, types of experiments (in vitro and in vivo) and model organisms. The aim of this work was to give a systematic overview of the effect of the above factors on the outcome of AChE and GE activity measurements. We showed that AChE activity could be measured with the substrate acetylthiocholine iodide (AChI) but not with acetylcholine bromide (AChB) and only in in vitro assays. For GE activity, Michaelis-Menten kinetics differed between the substrates 4-methylumbellifery butyrate (4-MUB) and 1-naphtyl acetate (1-NA) in the measurements of in vitro activity, but their inhibition curves and IC₅₀ values for the general inhibitor tetraisopropyl pyrophosphoramide (iso-OMPA) were similar, confirming that both substrates targeted the same group of enzymes. The GE substrate 4-MUB was applicable both in vitro and in vivo, while 1-NA was only applicable in vitro due to its high acute toxicity. When comparing the zooplankton crustacean Daphnia magna and the sediment dwelling Chironomus riparius, the latter had a four-fold higher maximal AChE activity (V_max) and a higher susceptibility to the AChE inhibitor BW284c51 (four-fold lower 50% inhibitory concentration, IC₅₀), but a lower maximal GE activity and lower susceptibility to iso-OMPA (higher IC₅₀), indicating significant species differences between in C. riparius and D. magna. We conclude that both choice of substrate and exposure method matters for the outcome of esterase assays and that esterase compositions between species may vary significantly.

Targeting the menaquinol binding loop of mycobacterial cytochrome bd oxidase

Mycobacteria have shown enormous resilience to survive and persist by remodeling and altering metabolic requirements. Under stringent conditions or exposure to drugs, mycobacteria have adapted to rescue themselves by shutting down their major metabolic activity and elevate certain survival factor levels and efflux pathways to survive and evade the effects of drug treatments. A fundamental feature in this adaptation is the ability of mycobacteria to vary the enzyme composition of the electron transport chain (ETC), which generates the proton motive force for the synthesis of adenosine triphosphate via oxidative phosphorylation. Mycobacteria harbor dehydrogenases to fuel the ETC, and two terminal respiratory oxidases, an aa3-type cytochrome c oxidase (cyt-bcc-aa3) and a bacterial specific cytochrome bd-type menaquinol oxidase (cyt-bd). In this study, we employed homology modeling and structure-based virtual screening studies to target mycobacteria-specific residues anchoring the b558 menaquinol binding region of Mycobacterium tuberculosis cyt-bd oxidase to obtain a focused library. Furthermore, ATP synthesis inhibition assays were carried out. One of the ligands MQL-H₂ inhibited both NADH₂- and succinate-driven ATP synthesis inhibition of Mycobacterium smegmatis inside-out vesicles in micromolar potency. Similarly, MQL-H₂ also inhibited NADH₂-driven ATP synthesis in inside-out vesicles of the cytochrome-bcc oxidase deficient M. smegmatis strain. Since neither varying the electron donor substrates nor deletion of the cyt-bcc oxidase, a major source of protons, hindered the inhibitory effects of the MQL-H₂, reflecting that MQL-H₂ targets the terminal oxidase cytochrome bd oxidase, which was consistent with molecular docking studies. Characterization of novel cytochrome bd oxidase Menaquinol binding domain inhibitor (MQL-H2) using virtual screening and ATP synthesis inhibition assays.

Mutation of the Transcriptional Regulator YtoI Rescues Listeria monocytogenes Mutants Deficient in the Essential Shared Metabolite 1,4-Dihydroxy-2-Naphthoate (DHNA)

Listeria monocytogenes, a Gram-positive, facultative intracellular pathogen, survives and replicates in the cytosol of host cells. Synthesis of 1,4-dihydroxy-2-naphthoate (DHNA), an intermediate of menaquinone biosynthesis, is essential for cytosolic survival of L. monocytogenes independent from its role in respiration. Here, we demonstrate that DHNA is essential for virulence in a murine model of listeriosis due to both respiration-dependent and -independent functions. In addition, DHNA can be both secreted and utilized as an extracellular shared metabolite to promote cytosolic survival inside host macrophages. To understand the role(s) of DHNA in L. monocytogenes intracellular survival and virulence, we isolated DHNA-deficient (ΔmenD strain) suppressor mutants that formed plaques in monolayers of fibroblasts. Five ΔmenD suppressor (mds) mutants additionally rescued at least 50% of the cytosolic survival defect of the parent ΔmenD mutant. Whole-genome sequencing revealed that four of the five suppressor mutants had independent missense mutations in a putative transcriptional regulator, ytoI (lmo1576). Clean deletion and complementation in trans confirmed that loss of ytoI could restore plaquing and cytosolic survival of DHNA-deficient L. monocytogenes RNA-seq transcriptome analysis revealed five genes (lmo0944, lmo1575, lmo1577, lmo2005, and lmo2006) expressed at a higher level in the ΔytoI strain than in the wild-type strain, whereas two genes (lmo1917 and lmo2103) demonstrated lower expression in the ΔytoI mutant. Intriguingly, the majority of these genes are involved in controlling pyruvate flux. Metabolic analysis confirmed that acetoin, acetate, and lactate flux were altered in a ΔytoI mutant, suggesting a critical role for regulating these metabolic programs. In conclusion, we have demonstrated that, similar to findings in select other bacteria, DHNA can act as a shared resource, and it is essential for cytosolic survival and virulence of L. monocytogenes Furthermore, we have identified a novel transcriptional regulator in L. monocytogenes and determined that its metabolic regulation is implicated in cytosolic survival of L. monocytogenes.

The diversity, origin, and evolutionary analysis of geosmin synthase gene in cyanobacteria

The sesquiterpene geosmin, mainly originating from cyanobacteria, is considered one of the problematic odor compounds responsible for unpleasant-tasting and -smelling water episodes in freshwater supplies. The biochemistry and genetics of geosmin synthesis in cyanobacteria is well-elucidated and the geosmin synthase gene (geo) has been cloned and characterized in recent years. However, understanding the diversity, origin, and evolution of geo has been hindered by the limited availability of geo sequences to date. On the basis of the cloned geo sequences from16 filamentous geosmin-producing cyanobacterial species, representing 11 genera in Nostocales and Oscillatoriales, the diversity and evolution of geo in cyanobacteria was systematically analyzed in this study. Homologous alignment revealed that geo is highly conserved among the examined cyanobacterial species, with DNA sequence identities >0.72. Phylogenetic reconstruction and codon bias analysis based on geo suggest that cyanobacterial geo form a monophyletic branch with a common origin and ancestor for cyanobacteria, actinomycetes, and myxobacteria. The global ratio of nonsynonymous/synonymous nucleotide substitutions (dN/dS) was 0.125, which is substantially <1 and indicates strong purifying selection in the evolution of cyanobacterial geo. To add to further interest, horizontal gene transfer of cyanobacterial geo in evolutionary history was confirmed by the discovery of an incongruent coevolutionary relationship between geo and housekeeping genes 16S rDNA and rpoC. The present study enhances the fundamental understanding of cyanobacterial geo in diversity and evolution, and sheds light on the development of molecular assays for detection and molecular ecology research of geosmin-producing cyanobacteria.

Combinatorial Engineering of Mevalonate Pathway and Diterpenoid Synthases in Escherichia coli for cis-Abienol Production

Identification of diterpene synthase-encoding genes together with synthetic biology technology offers an opportunity for the biosynthesis of cis-abienol. The methylerythritol phosphate (MEP) and the mevalonate (MVA) pathways were both engineered for cis-abienol production in Escherichia coli, which improved the cis-abienol yield by approximately 7-fold and 31-fold, respectively, compared to the yield obtained by overexpression of the MEP pathway alone or the original MEP pathway. Furthermore, systematic optimization of cis-abienol biosynthesis was performed, such as diterpene synthase screening and two-phase cultivation. The combination of bifunctional class I/II cis-abienol synthase from Abies balsamea ( AbCAS) and class II abienol synthase from Salvia sclarea ( SsTPS2) was found to be the most effective. By using isopropyl myristate as a solvent in two-phase cultivation, cis-abienol production reached 634.7 mg/L in a fed-batch bioreactor. This work shows the possibility of E. coli utilizing glucose as a carbon source for cis-abienol biosynthesis through a modified pathway.

Metabolic and proteomic mechanism of benzo[a]pyrene degradation by Brevibacillus brevis

Benzo[a]pyrene (BaP) is a model compound of polycyclic aromatic hydrocarbons. The relationship between its toxicity and some target biomolecules has been investigated. To reveal the interactions of BaP biodegradation and metabolic network, BaP intermediates, proteome, carbon metabolism and ion transport were analyzed. The results show that 76% BaP was degraded by Brevibacillus brevis within 7 d through the cleavage of aromatic rings with the production of 1-naphthol and 2-naphthol. During this process, the expression of xylose isomerase was induced for xylose metabolism, whereas, α-cyclodextrin could no longer be metabolized. Lactic acid, acetic acid and oxalic acid at 0.1-1.2 mg dm^-3 were released stemming from their enhanced biosynthesis in the pathways of pyruvate metabolism and citrate cycle, while 5-7 mg dm^-3 of PO₄^3- were transported for energy metabolism. The relative abundance of 43 proteins was significantly increased for pyruvate metabolism, citrate cycle, amino acid metabolism, purine metabolism, ribosome metabolism and protein synthesis.

Characterization of MenA (isoprenyl diphosphate:1,4-dihydroxy-2-naphthoate isoprenyltransferase) from Mycobacterium tuberculosis

The menaquinone biosynthetic pathway presents a promising drug target against Mycobacterium tuberculosis and potentially other Gram-positive pathogens. In the present study, the essentiality, steady state kinetics of MenA from M. tuberculosis and the mechanism of MenA inhibition by Ro 48-8071 were characterized. MenA [isoprenyl diphosphate:1,4-dihydroxy-2-naphthoate (DHNA) isoprenyltransferase] catalyzes a critical reaction in menaquinone biosynthesis that involves the conversion of cytosolic DHNA, to membrane bound demethylmenaquinone by transferring a hydrophobic 45-carbon isoprenoid chain (in the case of mycobacteria) to the ring nucleus of DHNA. Rv0534c previously identified as the gene encoding MenA in M. tuberculosis complemented a menA deletion in E. coli and an E. coli host expressing Rv0534c exhibited an eight-fold increase in MenA specific activity over the control strain harboring empty vector under similar assay conditions. Expression of Rv0534c is essential for mycobacterial survival and the native enzyme from M. tuberculosis H37Rv was characterized using membrane preparations as it was not possible to solubilize and purify the recombinant enzyme. The enzyme is absolutely dependent on the presence of a divalent cation for optimal activity with Mg+2 being the most effective and is active over a wide pH range, with pH 8.5 being optimal. The apparent Km values for DHNA and farnesyl diphosphate were found to be 8.2 and 4.3 μM, respectively. Ro 48-8071, a compound previously reported to inhibit mycobacterial MenA activity, is non-competitive with regard to DHNA and competitive with regard to the isoprenyldiphosphate substrate.

Split-TALE: A TALE-Based Two-Component System for Synthetic Biology Applications in Planta

Transcription activator-like effectors (TALEs) are bacterial Type-III effector proteins from phytopathogenic Xanthomonas species that act as transcription factors in plants. The modular DNA-binding domain of TALEs can be reprogrammed to target nearly any DNA sequence. Here, we designed and optimized a two-component AND-gate system for synthetic circuits in plants based on TALEs. In this system, named split-TALE (sTALE), the TALE DNA binding domain and the transcription activation domain are separated and each fused to protein interacting domains. Physical interaction of interacting domains leads to TALE-reconstitution and can be monitored by reporter gene induction. This setup was used for optimization of the sTALE scaffolds, which result in an AND-gate system with an improved signal-to-noise ratio. We also provide a toolkit of ready-to-use vectors and single modules compatible with Golden Gate cloning and MoClo syntax. In addition to its implementation in synthetic regulatory circuits, the sTALE system allows the analysis of protein-protein interactions in planta.

Synthesis and biological evaluation of pyrazole linked benzothiazole-β-naphthol derivatives as topoisomerase I inhibitors with DNA binding ability

A series of new pyrazole linked benzothiazole-β-naphthol derivatives were designed and synthesized using a simple, efficient and ecofriendly route under catalyst-free conditions in good to excellent yields. These derivatives were evaluated for their cytotoxicity on selected human cancer cell lines. Among those, the derivatives 4j, 4k and 4l exhibited considerable cytotoxicity with IC₅₀ values ranging between 4.63 and 5.54 µM against human cervical cancer cells (HeLa). Structure activity relationship was elucidated by varying different substituents on benzothiazoles and pyrazoles. Further, flow cytometric analysis revealed that these derivatives induced cell cycle arrest in G2/M phase and spectroscopic studies such as UV-visible, fluorescence and circular dichroism studies showed that these derivatives exhibited good DNA binding affinity. Additionally, these derivatives can effectively inhibit the topoisomerase I activity. Viscosity studies and molecular docking studies demonstrated that the derivatives bind with the minor groove of the DNA.

Carbaryl biodegradation by Xylaria sp. BNL1 and its metabolic pathway

Although ascomycetes occupy a vaster niche in soil than the well-studied basidiomycetes, they have received limited attention in studies related to bioremediation. In this study, the degradation of carbaryl by Xylaria sp. was studied in different culture conditions and its possible metabolic pathway was elucidated. In liquid culture, 99% of the added carbaryl was eliminated when cytochrome P450 (CYP450) was active, which was similar to the degradation rate of Pleurotus ostreatus, a fungus with strong bioremediation ability. Mn²⁺ is beneficial to the degradation of carbaryl. Compared to the 72.17% degradation rate in sterile soil, 59.0% carbaryl was eliminated in non-sterile soil, which suggested that Xylaria sp. BNL1 can resist microorganismal infection. Furthermore, the intracellular fractions containing laccase, CYP450, and carbaryl esterase efficiently degraded carbaryl. The presence of carbaryl metabolites suggested that Xylaria sp. BNL1 initiated its attack on carbaryl via carbaryl esterase to release α-naphthol, which was further degraded to 1,4-naphthoquinone and benzoic acid by CYP450 and laccase. Thus, our study highlights the potential of using Xylaria sp. for bioremediation.

The use of carboxylesterases as biomarkers of pesticide exposure in bivalves: A methodological approach

Bivalves are worldwide sentinels of anthropogenic pollution. The inclusion of biomarker responses in chemical monitoring is a recommended practise that has to overcome some difficulties. One of them is the time frame between sample collection and sample processing in order to ensure the preservation of enzymatic activities. In the present study, three bivalve species of commercial interest (mussel, Mytilus galloprovincialis, razor shell, Solen marginatus, and cockle, Cerastoderma edule) were processed within <2 h after being retrieved from their natural habitat, and 24 h after being transported in air under cold conditions (6-8 °C) to laboratory facilities. The enzymatic activities were compared in the three species submitted to both conditions revealing no differences in terms of carboxylesterase dependent activities (CEs) using different substrates: p-nitrophenyl acetate (pNPA), p-nitrophenyl butyrate (pNPB), 1-naphthyl acetate (1-NA), 1-naphthyl butyrate (1-NB) and 2-naphthyl acetate (2-NA). In mussels, three tissues were selected (haemolymph, gills and digestive gland). For comparative purposes, in razor shell and cockle only digestive gland was considered as it is the main metabolic organ. Baseline enzymatic activities for CEs were characterised in the digestive gland of the three bivalves using four out of the five selected CE substrates as well as the kinetic parameters (V_max and K_m) and catalytic efficiency. The in vitro sensitivity to the organophosphorus metabolite chlorpyrifos oxon was also calculated. IC₅₀ values (pM-nM range) were lower than those obtained for vertebrate groups which suggest that bivalves have high protection efficiency against this pesticide as well as species dependent particularities.

Total Synthesis Establishes the Biosynthetic Pathway to the Naphterpin and Marinone Natural Products

The naphterpins and marinones are naphthoquinone meroterpenoids with an unusual aromatic oxidation pattern that is biosynthesized from 1,3,6,8-tetrahydroxynaphthalene (THN). We propose that cryptic halogenation of THN derivatives by vanadium-dependent chloroperoxidase (VCPO) enzymes is key to this biosynthetic pathway, despite the absence of chlorine in these natural products. This speculation inspired a total synthesis to mimic the naphterpin/marinone biosynthetic pathway. In validation of this biogenetic hypothesis, two VCPOs were discovered that interconvert several of the proposed biosynthetic intermediates.

An improved method for PCR-based detection and routine monitoring of geosmin-producing cyanobacterial blooms

Production of taste and odour (T/O) compounds, principally geosmin, by complex cyanobacterial blooms is a major water quality issue globally. Control of these cyanobacteria imposes a significant cost on water producing and dependent industries, and requires routine monitoring and management. Classic monitoring methods, including microscopy and direct chemical analysis, lack sensitivity, are laborious, expensive or cannot reliably identify the source of geosmin production. Polymerase Chain Reaction (PCR) based tools targeting the geosmin synthase gene (geoA) provide a novel tool for routine monitoring. However, geoA is variable at the nucleotide level and potential geosmin producers represent a broad taxonomic distribution, such that multiple PCR primers with distinct amplification protocols are needed to target all potential sources of this important T/O compound. Development of novel primers is hindered by a lack of sequence data and limited field and laboratory data on geosmin producers prevents prioritizing taxa for PCR testing. Here we performed a genetic screen of 253 bloom samples from Victoria, Australia using each existing PCR protocol targeting geoA. We detected Dolichospermum ucrainicum as the major geosmin producer (87% of sequenced samples) along with 3 unknown geoA sequence types. Using these data, we designed a novel, short amplicon, PCR protocol utilising a single standardised primer pair, capable of amplifying all geoA positive samples in our study, as well as a Nostoc punctiforme positive control. This single protocol geoA PCR can further be tested on other geosmin producers and will simplify routine monitoring of T/O producing cyanobacteria.

Characterization of Musty Odor-Producing Actinomycetes from Tropics and Effects of Temperature on the Production of Musty Odor Compounds

Geosmin and 2-methylisoborneol (MIB) outbreaks in tropical water bodies, such as Southeast Asia, by actinomycetes have not yet been elucidated in detail. Six Streptomyces isolates from lowland environments in Malaysia were selected and evaluated for their odor production under different temperatures. The gene responsible for the production of geosmin, geoA, was detected in all isolates, while only two isolates harbored tpc, which is responsible for 2-MIB production. This result suggested that geosmin and 2-MIB synthesis pathway genes already existed in the environment in the Tropics of Southeast Asia. Furthermore, our isolates produced musty odor compounds at 30°C, and differences were observed in musty odor production between various temperatures. This result indicated the potential for odor episodes in water bodies of the tropical countries of Southeast Asia throughout the year due to the mean annual ambient temperature of 27°C in the lowlands.

Functional characterization of carboxylesterase gene mutations involved in Aphis gossypii resistance to organophosphate insecticides

Carboxylesterases (CarEs) play an important role in detoxifying insecticides in insects. Over-expression and structural modification of CarEs have been implicated in the development of organophosphate (OP) insecticide resistance in insects. A previous study identified four nonsynonymous mutations (resulting in four amino acid residue substitutions) in the open reading frame of the carboxylesterase gene of resistant cotton aphids compared to the omethoate susceptible strain, which has possibly influenced the development of resistance to omethoate (a systemic OP insecticide). The current study further characterized the function of these mutations, both alone and in combination, in the hydrolysis of OP insecticides. The metabolism results suggest that the combination of four mutations, mainly existing in the laboratory-selected OP-resistant cotton aphid population, increased the OP hydrolase activity (approximately twofold) at the cost of detectable carboxylesterase activity. The functional studies of single or multiple mutations suggest the positive effect of H104R, A128V and T333P on the acquisition of OP hydrolase activity, especially the combination of H104R with A128V or T333P. K484R substitution decreased both the OP hydrolase activity and the CarE activity, indicating that this mutation primarily drives the negative effect on the acquisition of OP hydrolase activity amongst these four mutations in the resistant strain. The modelling and docking results are basically consistent with the metabolic results, which strongly suggest that the structural gene modification is the molecular basis for the OP resistance in this laboratory-selected cotton aphid strain.

Geosmin production and polyphasic characterization of Oscillatoria limosa Agardh ex Gomont isolated from the open canal of a large drinking water system in Tianjin City, China

Taste and odor (T & O) episodes always cause strong effects on drinking water supply system. Luanhe River diversion into Tianjin City in China is an important drinking water resource. Massive growth of a benthic filamentous cyanobacterium with geosmin production in the open canal caused a strong earthy odor episode in Tianjin. On the basis of the morphological and molecular identification of this cyanobacterium as Oscillatoria limosa Agardh ex Gomont, the genetic basis for geosmin biosynthesis and factors influencing growth and geosmin production of O. limosa CHAB 7000 were studied in this work. A 2268-bp open reading frame, encoding 755 amino acids, was amplified and characterized as the geosmin synthase gene (geo), followed by a cyclic nucleotide-binding protein gene (cnb). Phylogenetic analysis implied that the evolution of the geosmin genes in O. limosa CHAB 7000 might involve a horizontal gene transfer event. Examination on the growth and geosmin production of O. limosa CHAB 7000 at different light intensities showed that the maximum geosmin production was observed at 10μmol photons m^-2s^-1, while the optimum growth was at 60μmol photons m^-2s^-1. Under three temperature conditions (15°C, 25°C, and 35°C), the maximum growth and geosmin production were observed at 25°C. Most amounts of geosmin were retained in cells during the growth phase, but high temperature and low light intensity increased the release of geosmin into the medium, implying that O. limosa CHAB 7000 had a high potential harm for the release of geosmin from its cells at these adverse conditions.

Geosmin as a source of the earthy-musty smell in fruits, vegetables and water: Origins, impact on foods and water, and review of the removing techniques

The earthy-musty smell produced by Streptomyces sp. is assigned to geosmin and is responsible for the major organoleptic defects found in drinking water, fruits and vegetables such as grapes, mushrooms, carrots, and beet. Geosmin is also found in juices and musts before fermentation and its presence has been associated with partial presence of Botrytis cinerea. It has a variable detection threshold depending on the matrix and the detection level ranges from 5 to 50 ng/L. On the sensory level, very few individuals are immune to geosmin and although the intensity of the defect caused by this molecule decreases rapidly in the nose, a bad taste is very persistent in the mouth. As the origin of geosmin is fungal, conventional control techniques used for geosmin prevention are limited to ventilation, improving the integrity of plants and use of storage temperatures around 1 °C in a humidity-controlled environment. However, it has been demonstrated that only the combination of different prophylactic and preventive measures provide a relatively sufficient efficacy. Therefore, prevention of factors favoring the formation of geosmin is still topical. Some chemical treatments showed relatively good results against Botrytis cinerea. However, there is a requirement that must be met, namely that only one chemical per family per year must be used. Moreover, a multi-year alternation of chemical families is a strong agronomic recommendation. Regarding Penicillium, no active material is 100% approved and it negative effects plants such as beet and grapes. Consequently, the importance of finding effective ways to fight against geosmin formation is still relevant. From analytical point of view, measurement of geosmin is mainly based on gas chromatography.

Five Unprecedented Secondary Metabolites from the Spider Parasitic Fungus Akanthomyces novoguineensis

Five new compounds including the glycosylated β-naphthol (1, akanthol), a glycosylated pyrazine (2, akanthozine), and three amide derivatives including a hydroxamic acid derivative (3–5) were isolated from the spider-associated fungus Akanthomyces novoguineensis (Cordycipitaceae, Ascomycota). Their structures were elucidated by using high resolution mass spectrometry (HRMS) and NMR spectroscopy. In this study, the antimicrobial, cytotoxic, anti-biofilm, and nematicidal activities of the new compounds were evaluated. The distribution pattern of secondary metabolites in the species was also revealed in which more isolates of A. novoguineensis were encountered and their secondary metabolite profiles were examined using analytical HPLC with diode array and mass spectrometric detection (HPLC-DAD/MS). Remarkably, all isolated compounds are specifically produced by A. novoguineensis.

Efficient biodegradation of phenanthrene by a novel strain Massilia sp. WF1 isolated from a PAH-contaminated soil

A novel phenanthrene (PHE)-degrading strain Massilia sp. WF1, isolated from PAH-contaminated soil, was capable of degrading PHE by using it as the sole carbon source and energy in a range of pH (5.0-8.0), temperatures (20-35 °C), and PHE concentrations (25-400 mg L(-1)). Massilia sp. WF1 exhibited highly effective PHE-degrading ability that completely degraded 100 mg L(-1) of PHE over 2 days at optimal conditions (pH 6.0, 28 °C). The kinetics of PHE biodegradation by Massilia sp. WF1 was well represented by the Gompertz model. Results indicated that PHE biodegradation was inhibited by the supplied lactic acid but was promoted by the supplied carbon sources of glucose, citric acid, and succinic acid. Salicylic acid (SALA) and phthalic acid (PHTA) were not utilized by Massilia sp. WF1 and had no obvious effect on PHE biodegradation. Only two metabolites, 1-hydroxy-2-naphthoic acid (1H2N) and PHTA, were identified in PHE biodegradation process. Quantitatively, nearly 27.7 % of PHE was converted to 1H2N and 30.3 % of 1H2N was further metabolized to PHTA. However, the PHTA pathway was broken and the SALA pathway was ruled out in PHE biodegradation process by Massilia sp. WF1.

Dihydroxynaphthalene-based mimicry of fungal melanogenesis for multifunctional coatings

Material-independent adhesive action derived from polycatechol structures has been intensively studied due to its high applicability in surface engineering. Here, we for the first time demonstrate that a dihydroxynaphthalene-based fungal melanin mimetic, which exhibit a catechol-free structure, can act as a coating agent for material-independent surface modifications on the nanoscale. This mimetic was made by using laccase to catalyse the oxidative polymerization of specifically 2,7-dihydroxynaphthalene. Analyses of the product of this reaction, using Fourier transform infrared-attenuated total reflectance and X-ray photoelectron spectroscopy, bactericidal action, charge-dependent sorption behaviour, phenol content, Zeta potential measurements and free radical scavenging activity, yielded results consistent with it containing hydroxyphenyl groups. Moreover, nuclear magnetic resonance analyses of the product revealed that C-O coupling and C-C coupling were the main mechanisms for its synthesis, thus clearly excluding a catechol structure in the polymerization. This product, termed poly(2,7-DHN), was successfully deposited onto a wide variety of solid surfaces, including metals, polymeric materials, ceramics, biosurfaces and mineral complexes. The melanin-like polymerization could be used to co-immobilize other organic molecules, forming functional surfaces. In addition, the hydroxyphenyl group contained in the coated poly(2,7-DHN) induced secondary metal chelation/reduction and adhesion with proteins, suggesting the potential of this poly(2,7-DHN) layer to serve as a platform material for a variety of surface engineering applications. Moreover, the novel physicochemical properties of the poly(2,7-DHN) illuminate its potential applications as bactericidal, radical-scavenging and pollutant-sorbing agents.

Dynamics and polyphasic characterization of odor-producing cyanobacterium Tychonema bourrellyi from Lake Erhai, China

The previous studies indicated that Tychonema-like strains from Lake Erhai could release geosmin so that the species was listed as the potential harmful cyanobacteria influencing the drinking water safety around Lake Erhai. But, the dynamics and biological information of this species were too limited. In this study, the polyphasic approach was used to reveal its biological characterization and the dynamics in Lake Erhai. The characters of trichomes, including filaments with solitary or bundle state, reddish-brown or blue-green color, planktonic habitat, and presence of keritomized content, were examined by the microscopic method. The 16S rDNA sequences of these strains were used for phylogenetic analysis and molecular identification. The strains were morphologically classified as Tychonema bourrellyi, and geosmin and β-ionone were identified as the major volatile substances using gas chromatography-mass spectrometry (GC-MS) analysis. No strains of T. bourrellyi were found to produce microcystin by the HPLC and mcy gene approaches. Cell numbers at 12 sampling sites in Lake Erhai were shown as an average of 3 × 10(4) cells L(-1) in 2009 and 2010. The obvious peaks occurred in July and August each year. This was the first report on occurrence of T. bourrellyi from outside of Europe, and T. bourrellyi was also a newly recorded species in China. Such a result demonstrated that T. bourrellyi could distribute extending from cold waters in North Europe to the warm waters in subtropical regions. It was interesting to observe the coincidence of the occurrence of T. bourrellyi with slightly eutrophicated waters since Lake Erhai had been regarded as an early phase of eutrophicated lake.

Effects of Tricyclazole on Cadmium Tolerance and Accumulation Characteristics of a Dark Septate Endophyte (DSE), Exophiala pisciphila

Exophiala pisciphila is a cadmium-tolerant fungus, and produces 1,8-dihydroxynaphthalene melanin which can be inhibited by tricyclazole. Tricyclazole at higher levels (20 and 40 µg mL−1) reduced the growth and sporulation of E. pisciphila, but toxicity was not observed at a low concentration (2.5 µg mL−1). Under cadmium (Cd) stress (50, 100 and 200 mg L−1), 2.5 µg mL−1 of tricyclazole reduced fungal growth and sporulation. These reduces indicated a decrease on Cd tolerance of E. pisciphila. For both the 0 and 2.5 µg mL−1 tricyclazole treatments, Cd was associated mostly with cell walls and was extracted by 2 % acetic acid and 1 M NaCl. The FTIR spectra of the E. pisciphila mycelia were similar for both 0 and 2.5 µg mL−1 tricyclazole treatments, which showed hydroxyl, amine, carboxyl and phosphate groups. Thus inhibition of melanin synthesis by tricyclazole did not change Cd accumulation characteristics in E. pisciphila. Results suggested that melanin played a protective role for E. pisciphila against Cd stress, but inhibition of melanin synthesis did not have a remarkable impact on Cd accumulation in E. pisciphila.

Hepatic biotransformation and antioxidant enzyme activities in Mediterranean fish from different habitat depths

Marine fish are threatened by anthropogenic chemical discharges. However, knowledge on adverse effects on deep-sea fish or their detoxification capabilities is limited. Herein, we compared the basal activities of selected hepatic detoxification enzymes in several species (Solea solea, Dicentrarchus labrax, Trachyrhynchus scabrus, Mora moro, Cataetix laticeps and Alepocehalus rostratus) collected from the coast, middle and lower slopes of the Blanes Canyon region (Catalan continental margin, NW Mediterranean Sea). The xenobiotic-detoxifying enzymes analysed were the phase-I carboxylesterases (CbEs), and the phase-II conjugation activities uridine diphosphate glucuronyltransferase (UDPGT) and glutathione S-transferase (GST). Moreover, some antioxidant enzyme activities, i.e., catalase (CAT), glutathione peroxidase (GPX) and glutathione reductase (GR), were also included in this comparative study. Because CbE activity is represented by multiple isoforms, the substrates α-naphthyl acetate (αNA) and ρ-nitrophenyl acetate (ρNPA) were used in the enzyme assays, and in vitro inhibition kinetics with dichlorvos were performed to compare interspecific CbE sensitivity. Activity of xenobiotic detoxification enzymes varied among the species, following a trend with habitat depth and body size. Thus, UDPGT and some antioxidant enzyme activities decreased in fish inhabiting lower slopes of deep-sea, whereas UDPGT and αNA-CbE activities were negatively related to fish size. A trend between CbE activities and the IC50 values for dichlorvos suggested S. solea and M. moro as potentially more sensitive to anticholinesterasic pesticides, and T. scabrus as the most resistant one. A principal component analysis considering all enzyme activities clearly identified the species but this grouping was not related to habitat depth or phylogeny. Although these results can be taken as baseline levels of the main xenobiotic detoxification enzymes in Mediterranean fish, further research is needed to evaluate their response to environmental contaminant exposure.

Fate of geosmin and 2-methylisoborneol in full-scale water treatment plants

The increasing frequency and intensity of taste and odour (T&O) producing cyanobacteria in water sources is a growing global issue. Geosmin and 2-methylisoborneol (MIB) are the main cyanobacterial T&O compounds and can cause complaints from consumers at levels as low as 10 ng/L. However, literature concerning the performance of full-scale treatment processes for geosmin and MIB removal is rare. Hence, the objectives of this study were to: 1) estimate the accumulation and breakthrough of geosmin and MIB inside full-scale water treatment plants; 2) verify the potential impact of sludge recycling practice on performance of plants; and, 3) assess the effectiveness of aged GAC for the removal of these compounds. Sampling after full-scale treatment processes and GAC pilot assays were conducted to achieve these goals. Geosmin and MIB monitoring in full-scale plants provided the opportunity to rank the performance of studied treatment processes with filtration and granular activated carbon providing the best barriers for removal of total and extracellular compounds, correspondingly. Geosmin was removed to a greater extent than MIB using GAC. Geosmin and MIB residuals in water post GAC contactors after two years of operation was 20% and 40% of initial concentrations, correspondingly. Biological activity on the GAC surface enhanced the removal of T&O compounds. These observations demonstrated that a multi-barrier treatment approach is required to ensure cyanobacteria and their T&O compounds are effectively removed from drinking water.

Isolation and characterization of a new reported cyanobacterium Leptolyngbya bijugata coproducing odorous geosmin and 2-methylisoborneol

The earthy-musty compounds geosmin and 2-methylisoborneol (MIB) produced by cyanobacteria are considered as the main biological causes of off-flavor events, especially in aquatic ecosystems. More than 50 filamentous cyanobacteria species have been documented as geosmin or MIB producers; however, little is known about the species coproducing these two metabolites. In this study, an epiphytic sample was collected from a river in Hubei, China. Three isolated strains (A2, B2, and B4) producing earthy odors were successfully isolated and identified as the cyanobacterium Leptolyngbya bijugata Anagnostidis et Komárek 1988 based on morphology and 16S rDNA sequences. Gas chromatography analysis confirmed that the isolated L. bijugata strains were geosmin and MIB coproducers, with accumulation ranging from 13.6 to 22.4 and 12.3 to 57.5 μg L(-1), respectively. The partial fragments of geosmin and MIB synthesis genes in the L. bijugata strains were cloned and sequenced. Further sequences and phylogenetic analysis indicated the high conservation and a common origin of these genes in cyanobacteria. This study is the first to report and characterize the coproduction of geosmin and MIB by L. bijugata, representing a new source for potential risk of off-flavor events.

Solvent resistance pumps of Pseudomonas putida S12: Applications in 1-naphthol production and biocatalyst engineering

The solvent resistance capacity of Pseudomonas putida S12 was applied by using the organism as a host for biocatalysis and through cloning and expressing solvent resistant pump genes into Escherichia coli. P. putida S12 expressing toluene ortho mononooxygenase (TOM-Green) was used for 1-naphthol production in a water-organic solvent biphasic system. Application of P. putida S12 improved 1-naphthol production per gram cell dry weight by approximately 42% compared to E. coli. Moreover, P. putida S12 enabled the use of a less expensive solvent, decanol, for 1-naphthol production. The solvent resistant pump (srpABC) genes of P. putida S12 were cloned into a solvent sensitive E. coli strain to transfer solvent tolerance. Recombinant strains bearing srpABC genes in either a low-copy number or a high-copy number plasmid grew in the presence of saturated concentration of toluene. Both of the recombinant strains were more tolerant to 1% v/v of toxic solvents, decanol and hexane, reaching similar cell density as the no-solvent control. Reverse-transcriptase analysis revealed that the srpABC genes were transcribed in engineered strains. The results demonstrate successful transfer of the proton-dependent solvent resistance mechanism and suggest that the engineered strain could serve as more robust biocatalysts in media with organic solvents.

Temperature effects on biomass, geosmin, and 2-methylisoborneol production and cellular activity by Nocardia spp. and Streptomyces spp. isolated from rainbow trout recirculating aquaculture systems

Isolates of Nocardia cummidelens, Nocard ia fluminea, Streptomyces albidoflavus, and Streptomyces luridiscabiei attributed as the cause of "earthy-musty" off-flavor in rainbow trout (Oncorhynchus mykiss) raised in recirculating aquaculture systems (RAS) were evaluated for the effect of temperature (10-30 °C) on biomass, geosmin, and 2-methylisoborneol (MIB) production and cellular activity. Cultures of these isolates were monitored over 7 days by measuring culture dry weight, geosmin, and MIB production using solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), and ATP production via a luminometer. Compared to the other isolates, S. luridiscabiei had significantly (P < 0.05) higher biomass (8.17 ± 0.35 mg/mL) at 15 °C (water temperature in the RAS) after 7 days incubation. In addition, S. luridiscabiei produced significantly (P < 0.05) higher geosmin (69,976 ± 15,733 ng/L) at 15 °C. At 25 °C and 30 °C, S. albidoflavus produced significantly (P < 0.05) higher geosmin (182,074 ± 60,272 ng/L and 399,991 ± 102,262 ng/L, respectively). All isolates produced MIB at 15 °C, but S. luridiscabiei produced significantly (P < 0.05) higher MIB (97,143 ± 28,972 ng/L) and ATP after 7 days. Therefore, S. luridiscabiei appears to be a likely contributor of geosmin and MIB in the RAS.

Divinyl sulfone cross-linked cyclodextrin-based polymeric materials: synthesis and applications as sorbents and encapsulating agents

The aim of this study was to evaluate the crosslinking abilities of divinyl sulfone (DVS) for the preparation of novel water-insoluble cyclodextrin-based polymers (CDPs) capable of forming inclusion complexes with different guest molecules. Reaction of DVS with native α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) and/or starch generates a variety of homo- and hetero-CDPs with different degrees of crosslinking as a function of the reactants’ stoichiometric ratio. The novel materials were characterized by powder X-ray diffraction, electron microscopy and for their sorption of phenol and 4-nitrophenol. They were further evaluated as sorbents with phenolic pollutants (bisphenol A and β-naphthol) and bioactive compounds (the hormone progesterone and curcumin). Data obtained from the inclusion experiments show that the degree of cross-linking has a minor influence on the yield of inclusion complex formation and highlight the important role of the CDs, supporting a sorption process based on the formation of inclusion complexes. In general, the inclusion processes are better described by a Freundlich isotherm although an important number of them can also be fitted to the Langmuir isotherm with R² ≥ 0.9, suggesting a sorption onto a monolayer of homogeneous sites.

Influence of geosmin-producing Streptomyces on the growth and volatile metabolites of yeasts during chinese liquor fermentation

Diverse Streptomyces species act as geosmin producers in the Chinese liquor-making process, causing an earthy, off-odor containment. Through microbiological and metabolite analyses, this paper investigates the influence of several geosmin-producing Streptomyces on the microbial community of a brewing system. The antifungal activity against functional liquor-brewing microbes was assayed by an agar diffusion method. Several Streptomyces, most notably Streptomyces sampsonii QC-2, inhibited the growth of the brewing functional yeasts and molds in pure culture. In a simulated coculture, Streptomyces spp. reduced the flavor compounds (alcohols and esters) contributed by yeasts. Nine components in Streptomyces sampsonii QC-2 broth were detected by ultraperformance liquid chromatography coupled with photo diode array (UPLC–PDA), with characteristic ultraviolet absorptions at 360, 380, and 400 nm. The main products of Streptomyces sampsonii QC-2 were identified by ultraperformance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF–MS/MS), and confirmed by standard mass spectrometry. The antifungal active components were revealed as a series of heptaene macrolide antibiotics.

Identification of geosmin and 2-methylisoborneol in cyanobacteria and molecular detection methods for the producers of these compounds

Geosmin and 2-methylisoborneol (MIB) are muddy/earthy off-flavor metabolites produced by a range of bacteria. Cyanobacteria are the major producers of the volatile metabolites geosmin and MIB which produce taste and odor problems in drinking water and fish worldwide. Here we detected geosmin and MIB by studying 100 cyanobacteria strains using solid phase microextraction gas chromatography mass spectrometry (SPME GC-MS). A total of 21 geosmin producers were identified from six cyanobacteria genera. Two of the geosmin producers also produced MIB. A PCR protocol for the detection of geoA and MIB synthase genes involved in the biosynthesis of geosmin and MIB was developed. The geoA and MIB synthase genes were detected in all strains shown to produce geosmin and MIB, respectively. Cyanobacterial geoA and MIB synthase sequences showed homology to terpene synthases genes of actinobacteria and proteobacteria. Additional off-flavor compounds, nor-carotenoids β-ionone and β-cyclocitral, were found from 55 strains among the 100 cyanobacterial strains studied; β-ionone was present in 45 and β-cyclocitral in 10 strains. Six of the cyanobacteria which contain off-flavor compounds also produced toxins, anatoxin-a or microcystins. The molecular method developed is a useful tool in monitoring potential cyanobacterial producers of geosmin and MIB.

Effect of oxidant exposure on the release of intracellular microcystin, MIB, and geosmin from three cyanobacteria species

The release of intracellular microcystin-LR (MC-LR), 2-methylisoborneol (MIB), and geosmin was investigated after the oxidation of three cyanobacteria (Microcystis aeruginosa (MA), Oscillatoria sp. (OSC), and Lyngbya sp. (LYN)). During the oxidation of 200,000 cells/mL of MA, release of intracellular MC-LR exceeded the World Health Organization (WHO) guideline of 1 μg/L during the lowest oxidant exposures (CT) tested: ozone (0 mg-min/L, below the ozone demand), chlorine (<40 mg-min/L), chlorine dioxide (<560 mg-min/L), and chloramine (<640 mg-min/L). As the CT increased, ozone, chlorine, and chlorine dioxide were able to oxidize the released MC-LR. During the oxidation of OSC (2800 cells/mL) and LYN (1600 cells/mL), release of intracellular MIB and geosmin exceeded reported threshold odor values after exposure to chlorine, chlorine dioxide, and chloramine, which have low reactivity with these taste and odor compounds. Ozone oxidation of OSC yielded an increase in MIB concentration at lower exposures (≤2.9 mg-min/L), likely due to insufficient oxidation by hydroxyl radicals. The release of intracellular organic matter (IOM) was also measured to determine the potential of bulk measurements to act as a surrogate for cyanotoxins and metabolite release. In all cases, the dissolved organic carbon (DOC) release was less than 0.25 mgC/L, which lacked the sensitivity to indicate the release of MC-LR, MIB, or geosmin. The fluorescence index proved to be a more sensitive indicator of intracellular organic matter release than DOC for MA. These results illustrate that toxic or odorous compounds may be released from cyanobacteria cells during oxidation processes with minimal changes in the DOC concentration.

Group I PAK inhibitor IPA-3 induces cell death and affects cell adhesivity to fibronectin in human hematopoietic cells

P21-activated kinases (PAKs) are involved in the regulation of multiple processes including cell proliferation, adhesion and migration. However, the current knowledge about their function is mainly based on results obtained in adherent cell types. We investigated the effect of group I PAK inhibition using the compound IPA-3 in a variety of human leukemic cell lines (JURL-MK1, MOLM-7, K562, CML-T1, HL-60, Karpas-299, Jurkat, HEL) as well as in primary blood cells. IPA-3 induced cell death with EC50 ranging from 5 to more than 20 μM. Similar range was found for IPA-3-mediated dephosphorylation of a known PAK downstream effector, cofilin. The cell death was associated with caspase-3 activation, PARP cleavage and apoptotic DNA fragmentation. In parallel, 20 μM IPA-3 treatment induced rapid and marked decrease of the cell adhesivity to fibronectin. Per contra, partial reduction of PAK activity using lower dose IPA-3 or siRNA resulted in a slight increase in the cell adhesivity. The changes in the cell adhesivity were also studied using real-time microimpedance measurement and by interference reflection microscopy. Significant differences in the intracellular IPA-3 level among various cell lines were observed indicating that an active mechanism is involved in IPA-3 transport.

Singlet molecular oxygen generation by light-activated DHN-melanin of the fungal pathogen Mycosphaerella fijiensis in black Sigatoka disease of bananas

In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg). Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN)-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg), a highly reactive oxygen specie (ROS) that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis) were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg). A pigmented-strain generated more O2 (1Δg) than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2) but we cannot distinguish the source. Our results suggest that O2 (1Δg) photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis.

Geosmin (2β,6α-dimethylbicyclo[4.4.0]decan-1β-ol) production associated with Beta vulgaris ssp. vulgaris is cultivar specific

The characteristic earthy flavor and aroma of table beet [Beta vulgaris ssp. vulgaris (garden beet group)] is due to the presence of geosmin, C₁₂H₂₂O, a volatile terpenoid compound commonly produced by many soil microorganisms. This study screened beet and related subspecies cultivars grown in three different environments (field, greenhouse in nonautoclaved soil, greenhouse in autoclaved soil) to evaluate the effect of cultivar and environment on geosmin level in table beet. There was no significant difference between years or between cultivars grown in autoclaved and nonautoclaved soil, indicating geosmin content may not be primarily attributable to microbial associations. A significant interaction between cultivar and environment was found, but generalizations could be made for high- or low-producing cultivars, demonstrating that geosmin levels were cultivar specific. 'Bull's Blood', 'Chioggia', and sugar beet exhibited the highest geosmin levels. Cultivars grown in the field had the smallest range of geosmin production, from 4.84 to 20.82 μg geosmin (kg root tissue)⁻¹. The high degree of consistency in cultivar performance across years and in ranking for geosmin levels across environments as well as the lack of a significant difference between plants grown in autoclaved and nonautoclaved soil suggests characteristic levels of geosmin may be present in and produced endogenously by cultivars of table beet. It may be possible to establish breeding populations with defined geosmin levels and to identify variety-specific aroma and flavor intensities that would be durable across environments.

Monitoring of geosmin producing Anabaena circinalis using quantitative PCR

Geosmin is one of the most commonly detected off-flavor chemicals present in reservoirs and drinking water systems. Quantitative real-time PCR (qPCR) is useful for quantifying geosmin-producers by focusing on the gene encoding geosmin synthase, which is responsible for geosmin synthesis. In this study, several primers and probes were designed and evaluated to detect the geosmin synthase gene in cyanobacteria. The specificity of primer and probe sets was tested using 21 strains of laboratory cultured cyanobacteria isolated from surface waters in Australia (18) and Taiwan (2), including 6 strains with geosmin producing ability. The results showed that the primers designed in this study could successfully detect all geosmin producing strains tested. The selected primers were used in a qPCR assay, and the calibration curves were linear from 5 × 10(1) to 5 × 10(5) copies mL(-1), with a high correlation coefficient (R(2) = 0.999). This method was then applied to analyze samples taken from Myponga Reservoir, South Australia, during a cyanobacterial bloom event. The results showed good correlations between qPCR techniques and traditional methods, including cell counts determined by microscopy and geosmin concentration measured using gas chromatography (GC) coupled with a mass selective detector (MSD). Results demonstrate that qPCR could be used for tracking geosmin-producing cyanobacteria in drinking water reservoirs. The qPCR assay may provide water utilities with the ability to properly characterize a taste and odor episode and choose appropriate management and treatment options.

A promiscuous prenyltransferase from Aspergillus oryzae catalyses C-prenylations of hydroxynaphthalenes in the presence of different prenyl donors

Prenyltransferases of the dimethylallyltryptophan synthase (DMATS) superfamily are involved in the biosynthesis of secondary metabolites and show broad substrate specificity towards their aromatic substrates with a high regioselectivity for the prenylation reactions. Most members of this superfamily accepted as prenyl donor exclusively dimethylallyl diphosphate (DMAPP). One enzyme, AnaPT from Neosartorya fischeri, was reported recently to use both DMAPP and geranyl diphosphate (GPP) as prenyl donors. In this study, we demonstrate the acceptance of DMAPP, GPP and farnesyl diphosphate (FPP) by a new member of this superfamily, BAE61387 from Aspergillus oryzae DSM1147, for C-prenylations of hydroxynaphthalenes.

Non-invasive pH determination adjacent to degradable biomaterials in vivo

An appropriate pH level is an important prerequisite for the physiologal functioning of cells and tissues. Changes in the extracellular pH often lead to specific cellular reactions and an altered metabolism of cells and tissues influences the extracellular pH range. Thus a method to monitor the extracellular pH is a valuable tool to track specific tissue reactions. In this article we describe a method for the determination of the pH range adjacent to degradable biomaterials using wireless in vivo imaging. Using hairless but immunocompetent mice the fluorophor 5-(6)-carboxy SNARF-1 and the in vivo fluorescence and multispectral acquisition and analysis system Maestro it is possible to track shifts in pH in small living animals over a longer period of time. This method is especially suitable for studies which focus on the interaction of degrading biomaterials with their adjacent tissues.

Establishment of quantitative PCR methods for the quantification of geosmin-producing potential and Anabaena sp. in freshwater systems

Geosmin has often been associated with off-flavor problems in drinking water with Anabaena sp. as the major producer. Rapid on-site detection of geosmin-producers as well as geosmin is important for a timely management response to potential off-flavor events. In this study, quantitative polymerase chain reaction (qPCR) methods were developed to detect the levels of Anabaena sp. and geosmin, respectively, by designing two PCR primer sets to quantify the rpoC1 gene (ARG) and geosmin synthase one (GSG) in Anabaena sp. in freshwater systems. The ARG density determined by qPCR assay is highly related to microscopic cell count (r(2) = 0.726, p < 0.001), and the limit of detection (LOD) and limit of quantification (LOQ) of the qPCR method were 0.02 pg and 0.2 pg of DNA, respectively. At the same time, the relationship between geosmin concentrations measured by gas chromatography-mass spectrometry (GC-MS) and GSG copies was also established (r(2) = 0.742, p < 0.001) with similar LOD and LOQ values. Using the two qPCR protocols, we succeeded in measuring different levels of ARG and GSG copies in different freshwater systems with high incidence environmental substrata and diverse ecological conditions, showing that the methods developed could be applied for environmental monitoring. Moreover, comparing to the microscopic count and GC-MS analytical methods, the qPCR methods can reduce the time-to-results from several days to a few hours and require considerably less traditional algal identification and taxonomic expertise.

Identification of a hotdog fold thioesterase involved in the biosynthesis of menaquinone in Escherichia coli

Escherichia coli is used as a model organism for elucidation of menaquinone biosynthesis, for which a hydrolytic step from 1,4-dihydroxy-2-naphthoyl-coenzyme A (DHNA-CoA) to 1,4-dihydroxy-2-naphthoate is still unaccounted for. Recently, a hotdog fold thioesterase has been shown to catalyze this conversion in phylloquinone biosynthesis, suggesting that its closest homolog, YbgC in Escherichia coli, may be the DHNA-CoA thioesterase in menaquinone biosynthesis. However, this possibility is excluded by the involvement of YbgC in the Tol-Pal system and its complete lack of hydrolytic activity toward DHNA-CoA. To identify the hydrolytic enzyme, we have performed an activity-based screen of all nine Escherichia coli hotdog fold thioesterases and found that YdiI possesses a high level of hydrolytic activity toward DHNA-CoA, with high substrate specificity, and that another thioesterase, EntH, from siderophore biosynthesis exhibits a moderate, much lower DHNA-CoA thioesterase activity. Deletion of the ydiI gene from the bacterial genome results in a significant decrease in menaquinone production, which is little affected in ΔybgC and ΔentH mutants. These results support the notion that YdiI is the DHNA-CoA thioesterase involved in the biosynthesis of menaquinone in the model bacterium.

The effect of extracellular pH changes on intracellular pH and nitric oxide concentration in endothelial and smooth muscle cells from rat aorta

Aims

It has been known for more than a century that pH changes can alter vascular tone. However, there is no consensus about the effects of pH changes on vascular response. In this study, we investigated the effects of extracellular pH (pH_o) changes on intracellular pH (pH_i) and intracellular nitric oxide concentration ([NO]_i) in freshly isolated endothelial cells and cross sections from rat aorta.

Main Methods

The HCl was used to reduce the pH_o from 7.4 to 7.0 and from 7.4 to 6.5; the NaOH was used to increase the pH_o from 7.4 to 8.0 and from 7.4 to 8.5. The fluorescent dyes 5-(and-6)-carboxy SNARF-1, acetoxymethyl ester, acetate (SNARF-1) and diaminofluorescein-FM diacetate (DAF-FM DA) were employed to measure the pH_i and [NO]_i, respectively. The fluorescence intensity was measured in freshly isolated endothelial cells by flow cytometry and in freshly obtained aorta cross sections by confocal microscopy.

Key Findings

The endothelial and vascular smooth muscle pH_i was increased at pH_o 8.5. The extracellular acidification did not change the endothelial pH_i, but the smooth muscle pH_i was reduced at pH_o 7.0. At pH_o 8.5 and pH_o 6.5, the endothelial [NO]_i was increased. Both extracellular alkalinization and acidification increased the vascular smooth muscle [NO]_i.

Significance

Not all changes in pH_o did result in pH_i changes, but disruption of acid-base balance in both directions induced NO synthesis in the endothelium and/or vascular smooth muscle.

[Simultaneous removal of algae and its odorous metabolite dimethyl trisulfide in water by potassium ferrate]

Co-removal of oscillatoria algae and its potential odorous metabolite dimethyl trisulfide (DMTS) in simulated algae-laden alkaline source water by potassium ferrate (K2FeO4) was investigated in contrast to potassium permanganate (KMnO4) pre-oxidation followed by polyferric chloride (PFC) under varying conditions, including pH, initial oxidant dosage and turbidity. Based on the pre-comparison with PFC, the optimal dosage of PFC in the combined KMnO4 pre-oxidation-PFC treatment was determined. Potassium ferrate resulted in 92.4% removal of algae, higher than PFC when the dosage was equivalent as measured by Fe and KMnO4 showed obviously positive effect as a coagulation aid. Degradation of dimethyl trisufide (92.5%) by potassium ferrate was better than the pre-oxidation of potassium permanganate (74.6%), and the treatment time was decreased from 10 min to 1 min.