Anti-hair loss effect of a shampoo containing caffeine and adenosine.

BACKGROUND: Hair loss is a widespread health problem that affects numerous individuals and is associated with age, lack of sleep, stress, endocrine problems, and other problems. Caffeine exerts various pharmacological effects, particularly after ingestion. The caffeine-induced inhibition of phosphodiesterases can increase intracellular cAMP concentrations, ultimately resulting in stimulatory effects on cell metabolism and proliferation. Hence, caffeine has been confirmed to inhibit hair loss caused by premature termination of the hair growth phase. Adenosine also improves hair loss by stimulating hair growth and thickening hair shafts. However, further empirical evidence is required to comprehensively assess the efficacy of hair loss treatment and prevention using a formulation of caffeine and adenosine in specific proportions in shampoos. OBJECTIVES: This study aimed to evaluate a shampoo with caffeine and adenosine as a daily scalp care product for hair loss in 77 subjects aged 18-60 years. METHODS: The overall and local hair densities were assessed using professional cameras and dermoscopes at different magnifications and distances. Five hairs that came off the participant's head were randomly selected to measure hair diameter. The self-assessment questionnaires were filled on third month of product use. RESULTS: The combination of caffeine and adenosine in the shampoo significantly enhanced hair density compared to that of the baseline. The results revealed a significant reduction in hair loss. The hair diameters of the subjects did not change significantly. Most of the participants (71.05%) were satisfied with their hair after using the product. CONCLUSIONS: Shampoos containing caffeine and adenosine have been demonstrated to exert therapeutic benefits for reducing hair loss.

Tuning Selectivity to f-Elements through Bonding and Solvation Effects of a Sulfur Donor Ligand.

Bis(2,4,4-trimethylpentyl)dithiophosphinic acid, commonly referred to as HBTMPDTP or Cyanex301, is a sulfur-donating ligand that shows considerable promise in the challenging task of separating trivalent actinides (An3+) from lanthanides (Ln3+). Although its effectiveness has been established, the specific molecular details about the preference of HBTMPDTP for americium over europium have remained a mystery, puzzling researchers for over two decades. This study presents a comprehensive, dual-driven separation mechanism for this complex system combining experimental and theoretical approaches. A critical finding is the increased covalency in An-S bonds compared to Ln-S bonds, which plays a significant role in HBTMPDTP's intrinsic selectivity for An3+ over Ln3+. This leads to the formation of distinct An3+ and Ln3+ species, enhancing the ligand's actinide selectivity. Additionally, it provides crucial insights into the coordination chemistry of f-elements with sulfur-donating ligands, thereby deepening our understanding of this intricate field.

Fabrication and release property of self-assembled garlic essential oil-amylose inclusion complex by pre-gelatinization coupling with high-speed shear.

Our aim was to investigate the preparation of self-assembled garlic essential oil-amylose inclusion complexes (SGAs) using garlic essential oil (GEO) and corn starch (CS), and evaluated their release properties. SGAs were fabricated by pre-gelatinization coupling with high-speed shear at different GEO-CS mass ratios. When the mass ratio of GEO to pre-gelatinized corn starch was set at 15 % (SGA-15 %), with a fixed shear rate of 9000 rpm and a shear time of 30 min, the allicin content was 0.573 ± 0.023 mg/g. X-ray diffraction (XRD) results revealed a starch V-type crystalline structure in SGAs with peaks at 13.0°, 18.0°, and 20.0° (2θ). Fourier Transform Infrared (FTIR) spectra of SGAs displayed a shift in the characteristic peak of diallyl trisulfide from 987.51 cm-1 to 991.45 cm-1. Scanning electron microscope (SEM) images revealed that SGAs exhibited lamellar structures covered with small granules. SGAs exhibited higher residual mass (approximately 12 %) than other samples. The resistant starch content of SGAs increased from 10.1 % to 18.4 % as GEO contents varied from 5 % to 15 %. In vitro digestion tests showed that about 53.21 % of allicin remained in SGA-15 % after 8 h. Therefore, this dual treatment can be a new method for fabricating controlled-release inclusion complexes of guest molecules.

The impacts of sodium lauroyl sarcosinate in facial cleanser on facial skin microbiome and lipidome.

BACKGROUND: The human skin microbiome and lipidome are essential for skin homeostasis and barrier function, and have become a focus in both dermatological and cosmetic fields. However, the influence of surfactants commonly used in cosmetic products on the skin resident microbiome and lipidome remains poorly characterized. METHODS: We conducted self-control experiments to systematically study the effects of surfactant (sodium lauroyl sarcosinate [SLS]) on facial skin. Wrinkles, pores, porphyrins, and superficial lipids were examined to evaluate the biophysical state of skin. Quantitative real-time PCR was used to detect the numbers of bacteria and fungi. The diversity and structure of prokaryotic and eukaryotic microbiomes were assessed using 16S rDNA and ITS amplicon sequencing, respectively. Moreover, 22 lipids were identified to evaluate lipidome variations. SPSS software was used for statistical analysis. RESULTS: SLS in facial cleanser did not extensively influence skin biophysical parameters, but caused a decrease in porphyrin. After using the SLS-added facial cleanser for 3 weeks, the alpha diversity of the prokaryotic microbial community decreased significantly, while the eukaryotic microbial community showed a continuous downward trend but no statistically significant. A shift in the structure of prokaryotic microbiome was observed as a result of SLS exposure, mainly reflected by the increase in Acinetobacter, Escherichia-Shigella, Streptococcus, and Ralstonia, while the SLS had little effect on the structure of the eukaryotic microbiome. Furthermore, SLS exposure had a great impact on skin lipidome, mainly manifested by the increase of phosphatidylglycerol (PG) and phosphatidylcholine (PC), and the decrease of ceramides. Spearman's correlations analysis showed that Escherichia-Shigella, Pseudomonas, and Acinetobacter are positively correlated with PG and PC; however, the correlation is not statistically significant. CONCLUSION: In this study, we found the SLS in facial cleanser primarily affected lipidome and the prokaryotic microbiome of facial skin. These findings are useful for reminding us to be vigilant about the ingredients in personal care products, even the common ingredients, and designing effective formulations for repairing ecological balance of skin.

Clinical evidence of the efficacy and safety of a new multi-peptide anti-aging topical eye serum.

BACKGROUND: Skin aging is a complex multifactorial progressive process. With age, intrinsic and extrinsic factors cause the loss of skin elasticity, with the formation of wrinkles, resulting in skin sagging through various pathways. A combination of multiple bioactive peptides could be used as a treatment for skin wrinkles and sagging. OBJECTIVES: This study aimed to evaluate the cosmetic efficacy of a multi-peptide eye serum as a daily skin-care product for improving the periocular skin of women within the ages of 20-45 years. METHODS: The stratum corneum skin hydration and skin elasticity were assessed using a Corneometer CM825 and Skin Elastometer MPA580, respectively. The PRIMOS CR technique based on digital strip projection technology was used for skin image and wrinkle analysis around the "crow's feet" area. Self-assessment questionnaires were filled on Day 14 and 28 of product use. RESULTS: This study included 32 subjects with an average age of 28.5 years. On Day 28, there was a significant decrease in the number, depth, and volume of wrinkles. Skin hydration, elasticity, and firmness increased continuously during the study period, consistent with typical anti-aging claims. A majority of the participants (75.00%) expressed overall satisfaction with their skin appearance after using the product. Most participants noted a visible skin improvement, with an increase in skin elasticity and smoothness, and confirmed the extensibility, applicability, and temperance of the product. No adverse reactions related to product use were observed. CONCLUSIONS: The multi-peptide eye serum uses a multi-targeted mechanism against skin aging to improve the skin appearance, making it an ideal choice for daily skincare.

Leaching NCM cathode materials of spent lithium-ion batteries with phosphate acid-based deep eutectic solvent.

Deep eutectic solvents (DESs) play an important role in efficient recovery of spent lithium-ion batteries (LIBs). In this study, we proposed an efficient and safe method by using a choline chloride-phenylphosphinic acid DES as a lixiviant for the leaching of LiNixCoyMnzO2 (NCM) cathode active materials of spent LIBs. The leaching conditions were optimized based on the leaching time, liquid-solid ratio, and leaching temperature. Under optimal experimental conditions, the leaching efficiencies of Li, Co, Ni, and Mn reached 97.7 %, 97.0 %, 96.4 %, and 93.0 %, respectively. The kinetics of the leaching process were well-fitted using the logarithmic law equation. The apparent activation energies for Li, Co, Ni, and Mn have been reported to be 60.3 kJ/mol, 78.9 kJ/mol, 99.3 kJ/mol, and 82.1 kJ/mol, respectively. UV-visible spectroscopy and Fourier transform infrared analysis revealed that the coordination configurations of Ni and Co in the leaching solution were octahedral and tetrahedral, respectively. In addition, the PO bond in phenylphosphinic acid was involved in coordination during leaching. This finding may provide an effective and safe approach for leaching valuable metals from spent LIBs.

Treatment of cyanide-bearing wastewater by the N263-TBP synergistic extraction system.

In this study, a trioctylmethylammonium chloride (N263)- tributyl phosphate (TBP)-n-octanol-sulfonated kerosene (N263-T) synergistic extraction system and an N263-n-octanol-sulfonated kerosene (N263-O) system were used to treat cyanide (CN)-bearing wastewater. The extraction saturation capacity of the two systems was measured. The influences of the initial pH and phase ratio (O/A) of the two systems on extraction were compared and analyzed. Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and slope methods were used to analyze the characteristic functional groups in the loaded organic phase, the compositions of the extracted compounds in the extraction reactions and the reaction mechanism. The results indicated that the saturated extraction capacity of the N263-T system, which was much larger than that of the N263-O system, for metal CN complex ions was 4354.31 mg/L. In addition, the N263-T system operated over a wider pH range. The extraction rates of copper (Cu), zinc (Zn), and iron (Fe) ions at pH 14 were 97.4%, 99.1%, and 87.2%, respectively. There was a strong compatibilization effect of TBP on the extraction system. The extraction efficiency of the N263-T system for metal CN complex ions was higher than that of the N263-O system when O/A = 0.4. The saturated loaded N263-T and N263-O systems were stripped by 1 mol/L NaOH +2 mol/L NaSCN solution at O/A = 3. The metal ion concentration in the stripping solution could be enriched to 11996.6 and 8913.3 mg/L for the N263-T and N263-O systems, respectively. During the extraction process, the binding ratios of N263 cations to Cu(CN)32-, Zn(CN)42-, and Fe(CN)63- were 2:1, 2:1, and 3:1, respectively. The binding ratios of TBP to Cu(CN)32-, Zn(CN)42-, and Fe(CN)63- in wastewater were 3:1, 4:1, and 6:1, respectively. The PO group in TBP was linked to the CN group of the metal CN complex ion by hydrogen bonds using the water molecule as a bridge to form a supramolecular anion group, which entered into the organic phase and combined with the N263 cation under the action of ion association.

Mesoporous adsorbent for competitive adsorption of fluoride ions in zinc sulfate solution.

Al-La hybrid gel was constructed using an innovative acid-catalyzed and calcination free sol-gel formation process which only included a sol-gel process lasting for 30 min and a drying procedure at 150 °C. This novel material was used as an adsorbent for competitive adsorption of fluoride ions in zinc sulfate solution. The properties, optimal adsorption conditions, synthetic principle and adsorption mechanism of the material were systemically investigated. The results showed that γ-AlO(OH) composed the skeleton of the Al-La hybrid gel and La(CH3COO)3 was embedded in the framework, which formed large amounts of ink-bottle type mesopores. A high fluoride ion adsorption rate with the removal rate reaching 50.88% within 1 min at 50 °C, 3 g L-1 was obtained. Analysis of the adsorption data has demonstrated that the adsorption of fluoride ions by the Al-La hybrid gel followed pseudo-second-order kinetics. Moreover, both Langmuir and Freundlich models can describe the adsorption process well. The maximum adsorption capacity of the Al-La hybrid adsorbent was 28.383 mg g-1. Furthermore, the mechanism analysis results indicated that the fluoride ions were mainly removed by the electrostatic adsorption on the AlO(OH), and a small amount of fluoride ions was also adsorbed by the complexation of lanthanum and fluoride ions. Since both AlO(OH) and La(CH3COO)3 had a large number of fluoride ion adsorption sites, the Al-La hybrid gel obtained an ideal adsorption capacity. In addition, the adsorption rate was greatly enhanced by the capillary action existing from the initial to the final stage of adsorption.

Iodine Capture Using Zr-Based Metal-Organic Frameworks (Zr-MOFs): Adsorption Performance and Mechanism.

The effective capture of radioiodine, produced or released from nuclear-related activities, is of paramount importance for the sustainable development of nuclear energy. Here, a series of zirconium-based metal-organic frameworks (Zr-MOFs), with a Zr6(µ3-O)4(µ3-OH)4 cluster and various carboxylate linkers, were investigated for the capture of volatile iodine. Their adsorption kinetics and recyclability were investigated in dry and humid environments. The structural change of Zr-MOFs during iodine trapping was studied using powder X-ray diffraction and pore structure measurements. Experimental spectra (Raman and X-ray photoelectron spectroscopy) and density functional theory (DFT) calculations for the linkers and Zr clusters were performed to understand the trapping mechanism of the framework. When interacting with iodine molecules, MOF-808, NU-1000, and UiO-66, with highly connected and/or rigid linkers, have better structural stability than UiO-67 and MOF-867, which have flexible linkers with less connectivity. Particularly, MOF-808, with a rigid and tritopic benzenetricarboxylate linker, has the highest iodine adsorption capacity (2.18 g/g, 80 °C), as well as the largest pore volume after iodine elution. In contrast, UiO-67, with long linear ditopic linkers, exhibits the weakest stability and lowest adsorption capacity (0.53 g/g, 80 °C) because of its most serious collapse of pore structures. After incorporating with strong electron-donating imidazole/pyridine ligands, both the stability and adsorption capacity of MOF-808/NU-1000 decrease. DFT calculations verify that the N-heterocycle groups could enhance the affinity toward iodine by strong charge transfer. DFT calculations also suggest that the terminal -OH in MOF-808 has a strong affinity toward iodine (-54 kJ/mol I2) and water (-63 kJ/mol H2O) and a weak affinity toward NO2 (-27 kJ/mol NO2). With high adsorption capacity and excellent stability, MOF-808 shows great potential for the sustainable removal of radioiodine.

Physicochemical properties and digestibility of potato starch treated by ball milling with tea polyphenols.

Native potato starch (NPS) with tea polyphenols (TPs) was treated in a planetary ball mill, and the effects of co-grinding on properties and digestibility of starch were studied. The X-ray diffraction (XRD) results showed that the crystal structure of starch granules was destroyed after 7 h of ball grinding, and their crystallinity degree reduced from 38.1% to 8.3%. The scanning electron microscopy (SEM) analyses indicated that the damaged starch granules and TPs displayed agglomerates after 7 h of milling. The Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) results demonstrated the existence of an interaction between starch chains and TPs, which improved the thermal stability and gelatinization temperatures of starch. The ball-milled starches with different amount of TPs showed significant variability to in vitro digestion (the contents of slowly digestible starch and resistant starch). Therefore, the produced ball-milled mixtures may be a desired dietary product for postprandial glycemic control.

SCO3129, a TetR family regulator, is responsible for osmotic stress in Streptomyces coelicolor.

Streptomyces are the soil-dwelling bacteria with a complex lifecycle and a considerable ability to produce a variety of secondary metabolites. Osmoregulation is important for their lifecycle in nature. In the genome of Streptomyces coelicolor M145, SCO3128 (encodes a putative fatty acid desaturase), SCO3129 (encodes a putative TetR family regulator) and SCO3130 (encodes a putative l-carnitine dehydratase) constitute a transcriptional unit, and its transcript was found to be in response to osmotic stress. Disruption of SCO3130 led to a bald phenotype on MMG medium and the mycelia lysis on the edge of the colony when KCl/NaCl was added to the medium. These results indicated that SCO3130 is important for the osmotic stress resistance in S. coelicolor. Transcriptional analysis and electrophoretic mobility shift assays (EMSA) demonstrated that SCO3129 repressed the transcription of SCO3128-3130 operon through directly binding to the promoter region of SCO3128, indicating that SCO3129 regulates the transcription of SCO3128-3130 in response to osmotic stress.

Modeling of the bacterial inactivation kinetics of dialdehyde cellulose in aqueous suspension.

The purpose of this study was to estimate the antibacterial properties of aqueous suspensions of dialdehyde microcrystalline cellulose (DAMC), and a model of the observed antibacterial kinetics was proposed and validated. The DAMC was prepared from microcrystalline cellulose by periodate oxidation. The bacterial inactivation kinetics of aqueous suspensions of DAMC was investigated by measuring the bactericidal effect after different contact times. The results indicated that with a DAMC aldehyde content of 6.34 mmol/g, the MICs for S. aureus, E. coli, B. subtilis and S. typhimurium were 15, 15, 15 and 30 mg/mL, respectively. This research thus establishes an antibacterial kinetics model of DAMC with 6.34 mmol/g of aldehyde content. At 37 °C and atmospheric pressure, the bacterial inactivation kinetic conformed to the equation: Log reduction of bacteria = - k [DAMC] t.

Ficellomycin: an aziridine alkaloid antibiotic with potential therapeutic capacity.

Ficellomycin is an aziridine antibiotic produced by Streptomyces ficellus, which displays high in vitro activity against Gram-positive bacteria including multidrug resistant strains of Staphylococcus aureus. Compared to currently available antibiotics, ficellomycin exhibits a unique mechanism of action-it impairs the semiconservative DNA replication by inducing the formation of deficient 34S DNA fragments, which lack the ability to integrate into larger DNA pieces and eventually the complete bacterial chromosome. Until recently, some important progress has been made in research on ficellomycin synthesis and biosynthesis, opening the perspective to develop a new generation of antibiotics with better clinical performance than the currently used ones. In this review, we will cover the discovery and biological activity of ficellomycin, its biosynthesis, mode of action, and related synthetic analogs. The role of ficellomycin and its analogs as an important source of drug prototypes will be discussed together with future research prospects.

Identification and characterization of the ficellomycin biosynthesis gene cluster from Streptomyces ficellus.

Ficellomycin is a peptide-like antibiotic which exhibits potent in vitro activity against Penicillium oxalicum and Staphylococcus aureus, even against strains resistant to most clinically used antibiotics. The gene cluster responsible for ficellomycin biosynthesis was cloned from Streptomyces ficellus and sequenced. It was found to contain 26 ORFs and is located within 30 kb of contiguous DNA. Targeted disruption of the encoding genes revealed that most were involved in the functional section of ficellomycin biosynthesis, such as peptide assembly, regulation, resistance, and biosynthesis of the precursor of ficellomycin 2-[4-guanidyl-1-azabicyclo[3.1.0]hexan-2-yl] glycine (2-GAHG). Within the 2-GAHG synthesis pathway, a sulfate adenylyltransferase appears to be involved in the synthesis of the pharmaceutically important 1-azabicyclo[3.1.0]hexane ring moiety, which has been reported to cause DNA cross-linking or impairment of semiconservative DNA replication.

Yeast cell surface display of linoleic acid isomerase from Propionibacterium acnes and its application for the production of trans-10, cis-12 conjugated linoleic acid.

Conjugated linoleic acid (CLA), a family of geometric and positional isomers of linoleic acid, has many health-promoting properties. Different isomers of CLA may have very different physiological effects. In the current work, we explore the possibility to produce single isomer of CLA by using biocatalysis based on displayed biocatalysts on the yeast cell surfaces. A reporter system used to assess gene expression and protein distribution was established by combining the egfp gene to the N-terminus of Propionibacterium acnes pai gene encoding the linoleic isomerase onto vector pYD1. After induction of the yeast strains containing pYD1::egfp::pai with galactose, strong green fluorescence was observed on the surface of cells, demonstrating that the fusion protein was successfully displayed. Using the engineered strains as whole-cell biocatalyst, trans-10, cis-12 CLA was detected in the reaction mixture. To improve the biocatalytic potential of this system, the first 20 amino codons of pai were modified, and the catalytic reaction conditions were optimized. Optimization of the codon usage resulted in 35% increase of CLA production, and the maximum yield of CLA was observed within 20 H in the optimal conditions: pH 7.0, 4 mg/mL linoleic acid, 37 °C. The system established in the present work can guide the development of biocatalytic strategies to produce trans-10, cis-12 CLA single isomer.

Characterization of the extracted complexes of trivalent lanthanides with purified cyanex 301 in comparison with trivalent actinide complexes.

The extracted complexes of trivalent lanthanides (Ln(III)) with purified Cyanex 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid, denoted as HA) were investigated by extended X-ray absorption fine structure spectroscopy (EXAFS), UV-Vis and fluorescence spectroscopy. In the complexes prepared under the same conditions of solvent extraction, the light Ln(III) ions are mainly coordinated by the sulfur atoms of the ligands, and the middle Ln(III) ions are coordinated by mixed donors, the sulfur atoms of the ligands and the oxygen atoms of the extracted water, while the heavy Ln(III) ions are completely hydrated in the organic phase without any sulfur atoms of the ligands in the coordination shell. As the atomic number increases, the extracted water molecules gradually replace the sulfur atoms of the ligands in the first coordination shell of Ln(III), and simultaneously the ligand anions become counterions just for balancing the positive charge of the fully hydrated heavy Ln(III) ions. The effect of the change in the complex structures on the extraction of Ln(III) ions with HA was evaluated by the co-extraction of other thirteen individual Ln(III) together with Nd(III). In contrast to most ligands bonding more strongly to heavier Ln(III), HA preferentially extracts lighter Ln(III), suggesting that the unusual extraction capability of HA for Ln(III) might originate from the difference in the complex structures with Ln(III) ions.

Americium(III) capture using phosphonic acid-functionalized silicas with different mesoporous morphologies: adsorption behavior study and mechanism investigation by EXAFS/XPS.

Efficient capture of highly toxic radionuclides with long half-lives such as Americium-241 is crucial to prevent radionuclides from diffusing into the biosphere. To reach this purpose, three different types of mesoporous silicas functionalized with phosphonic acid ligands (SBA-POH, MCM-POH, and BPMO-POH) were synthesized via a facile procedure. The structure, surface chemistry, and micromorphology of the materials were fully characterized by (31)P/(13)C/(29)Si MAS NMR, XPS, and XRD analysis. Efficient adsorption of Am(III) was realized with a fast rate to reach equilibrium (within 10 min). Influences including structural parameters and functionalization degree on the adsorption behavior were investigated. Slope analysis of the equilibrium data suggested that the coordination with Am(III) involved the exchange of three protons. Moreover, extended X-ray absorption fine structure (EXAFS) analysis, in combination with XPS survey, was employed for an in-depth probe into the binding mechanism by using Eu(III) as a simulant due to its similar coordination behavior and benign property. The results showed three phosphonic acid ligands were coordinated to Eu(III) in bidentate fashion, and Eu(P(O)O)3(H2O) species were formed with the Eu-O coordination number of 7. These phosphonic acid-functionalized mesoporous silicas should be promising for the treatment of Am-containing radioactive liquid waste.

Physiological characterization of ATP-citrate lyase in Aspergillus niger.

Acetyl-CoA, an important molecule in cellular metabolism, is generated in multiple subcellular compartments and mainly used for energy production, biosynthesis of a diverse set of molecules, and protein acetylation. In eukaryotes, cytosolic acetyl-CoA is derived mainly from the conversion of citrate and CoA by ATP-citrate lyase. Here, we describe the targeted deletions of acl1 and acl2, two tandem divergently transcribed genes encoding subunits of ATP-citrate lyase in Aspergillus niger. We show that loss of acl1 or/and acl2 results in a significant decrease of acetyl-CoA and citric acid levels in these mutants, concomitant with diminished vegetative growth, decreased pigmentation, reduced asexual conidiogenesis, and delayed conidial germination. Exogenous addition of acetate repaired the defects of acl-deficient strains in growth and conidial germination but not pigmentation and conidiogenesis. We demonstrate that both Acl1 and Acl2 subunits are required to form a functional ATP-citrate lyase in A. niger. First, deletion of acl1 or/and acl2 resulted in similar defects in growth and development. Second, enzyme activity assays revealed that loss of either acl1 or acl2 gene resulted in loss of ATP-citrate lyase activity. Third, in vitro enzyme assays using bacterially expressed 6His-tagged Acl protein revealed that only the complex of Acl1 and Acl2 showed ATP-citrate lyase activity, no enzyme activities were detected with the individual protein. Fourth, EGFP-Acl1 and mCherry-Acl2 proteins were co-localized in the cytosol. Thus, acl1 and acl2 coordinately modulate the cytoplasmic acetyl-CoA levels to regulate growth, development, and citric acid synthesis in A. niger.

Development of a markerless gene deletion system for Streptococcus zooepidemicus: functional characterization of hyaluronan synthase gene.

Streptococcus zooepidemicus is a bacterial pathogen used for production of hyaluronan in industry. Intensive research has significantly contributed to our understanding of S. zooepidemicus biology and pathogenesis. However, the lack of an effective targeted gene inactivation system in S. zooepidemicus has notably prevented the functional genomics analysis of this gram-positive bacterium. Here, we report the development of a markerless gene deletion system in S. zooepidemicus. We constructed a sacB expression cassette on the thermosensitive suicide vector pSET4s and demonstrated its use as a counterselection marker in S. zooepidemicus. We validated the efficiency of this system by deletion of hasA, which synthesizes the important virulence factor hyaluronic acid (HA) capsule. The genotype of the resultant hasA mutant was confirmed by polymerase chain reaction and sequencing. Deletion of hasA resulted in non-mucoid morphology, loss of HA capsule formation, and HA production. These defects can be rescued by introduction of a plasmid containing wild-type hasA expression cassette. Moreover, compared with wild type, hasA mutant showed no significant difference in expressions of other members of the hasABCDE operon, further suggesting that the loss of hasA contributed to the defects observed with ΔhasA mutant. Our results describe the first establishment of a sacB-based counterselection system in S. zooepidemicus, along with the first demonstration of hasA that is the only gene encoding a functional hyaluronan synthase in this bacterium.

SabR enhances nikkomycin production via regulating the transcriptional level of sanG, a pathway-specific regulatory gene in Streptomyces ansochromogenes.

BACKGROUND: sabR is a pleiotropic regulatory gene which has been shown to positively regulate the nikkomycin biosynthesis and negatively affect the sporulation of Streptomyces ansochromogenes. In this study, we investigate the mechanism of SabR on modulating nikkomycin production in Streptomyces ansochromogenes. RESULTS: The transcription start point of sabR was determined by high-resolution S1 nuclease mapping and localized at the nucleotide T at position 37 bp upstream of the potential sabR translation start codon (GTG). Disruption of sabR enhanced its own transcription, but retarded the nikkomycin production. Over-expression of sabR enhanced nikkomycin biosynthesis in Streptomyces ansochromogenes. EMSA analysis showed that SabR bound to the upstream region of sanG, but it did not bind to the upstream region of its encoding gene (sabR), sanF and the intergenic region between sanN and sanO. DNase 1 footprinting assays showed that the SabR-binding site upstream of sanG was 5'-CTTTAAGTCACCTGGCTCATTCGCGTTCGCCCAGCT-3' which was designated as SARE. Deletion of SARE resulted in the delay of nikkomycin production that was similar to that of sabR disruption mutant. CONCLUSIONS: These results indicated that SabR modulated nikkomycin biosynthesis as an enhancer via interaction with the promoter region of sanG, and expanded our understanding about regulatory cascade in nikkomycin biosynthesis.