Pigment Formation Research Articles

New colours for old in the blue-cheese fungus Penicillium roqueforti

Penicillium roqueforti is used worldwide in the production of blue-veined cheese. The blue-green colour derives from pigmented spores formed by fungal growth. Using a combination of bioinformatics, targeted gene deletions, and heterologous gene expression we discovered that pigment formation was due to a DHN-melanin biosynthesis pathway. Systematic deletion of pathway genes altered the arising spore colour, yielding white to yellow-green to red-pink-brown phenotypes, demonstrating the potential to generate new coloured strains. There was no consistent impact on mycophenolic acid production as a result of pathway interruption although levels of roquefortine C were altered in some deletants. Importantly, levels of methyl-ketones associated with blue-cheese flavour were not impacted. UV-induced colour mutants, allowed in food production, were then generated. A range of colours were obtained and certain phenotypes were successfully mapped to pathway gene mutations. Selected colour mutants were subsequently used in cheese production and generated expected new colourations with no elevated mycotoxins, offering the exciting prospect of use in future cheese manufacture.

Embelia ribes Burm.f. fruit extract inhibit quorum sensing-dependent production of virulence factors and biofilm formation: An integrated in vitro and in silico approach

Quorum sensing (QS) is a cell-to-cell signaling method that allows bacteria to control gene expression and regulate a variety of physiological processes, particularly the synthesis of virulence factors and biofilm formation. Inhibition of QS has been proposed as a promising strategy in attenuating the pathogenicity and enhancing the efficacy of antimicrobial drugs targeting bacterial infections. This study investigated the potential utilization of Embelia ribes fruit extract (ERFE) as an inhibitor of QS-dependent virulence factors and biofilm development in Gram negative pathogens. Further, the results were correlated with the inhibition of biofilms. High performance thin-layer chromatography (HPTLC), followed by analysis of phytochemicals using gas chromatography-mass spectrometry (GC–MS) was conducted. Analyzing ADMET (absorption, distribution, metabolism, excretion and toxicity) profiles, PAINS (Pan-assay interference compounds), and molecular docking analyses of selected potential phytochemicals were performed against proteins participating in QS and formation of biofilm. In-vitro analysis of anti-QS activity of ERFE against Chromobacterium violaceum (violacein production), Pseudomonas aeruginosa (pyocyanin production) and Serratia marcescens (prodigiosin production) demonstrated significant dose-dependent interference in pigment formation at sub-MIC concentrations. The development of biofilm was significantly reduced by 84.10, 85.52 and 70.64% over control at the highest sub-MIC levels for C. violaceum, P. aeruginosa and S. marcescens, respectively. Furthermore, in the presence of ERFE, swarming motility and exopolysaccharide production (EPS) were also reduced. As a result, further insights have been gained into the mechanism underlying the anti-QS activity. Further investigations with in-vivo studies are warranted to fully explore the therapeutic applications of this natural compound in managing the bacterial pathogenicity and biofilm-related infections.

Bilirubin and its crystal forms

Bilirubin crystals in the gall bladder and urine are typical indicators of liver dysfunction. Examining the crystal structure of lipophilic bilirubin is thus of interest. We present crystal structures for three crystal forms of the bile pigment.

The Characteristic Of Biocomposite Film Of Spirulina Residue As Natural Dyes

Spirulina plantesis microalgae contain active ingredients in the form of antioxidants and pigments. Currently, the microalgae Spirulina plantesis is used as an antioxidant in the food, pharmaceutical and cosmetic industries. This manuscript discusses the utilization of Spirulina plantesis microalgae pigment as a natural dye plastic. The need for color plastics for various uses continues to increase. The use of natural dyes for plastics is expected to produce biocomposite films that are safe for the environment or biodegradable and safe to be used. The aim of the study was to determine the effect of adding Spirulina residue as a natural dye on the characteristics of biocomposite films. The variable concentration of Spirulina residue added to the biocomposite film formula was 0.5%,1%, and 1.5%. The film production method used was the solution casting method. In this study, 200ml of distilled water was added with Spirulina residue (SR), then stirred for 30 minutes, and after that successively added 1% Glycerol and stirred for 15 minutes; Carrageenan 1% and stirred for 15 minutes. The solution was heated at 70oC then Polyvinyl Alcohol (PVA) with concentrations of 3%, 4%, and 5%, and Tapioca (3%) were added until complete gelatinization occurred. The solution was poured into a 30 cm x 20 cm mold and dried at 30oC for 48 hours to form a film. Biocomposite films were analyzed for tensile strength and elongation at break based on ASTM D 638, color, and morphology. The results showed that the highest tensile strength and elongation at break of biocomposites were found in biocomposite films with the addition of 0.5% Spirulina residue, namely 96.40±6.04 kgf/m2 and 47.64±7.48%, respectively. Analysis of the color of the biocomposite films showed the highest greenish and yellowish colors in the biocomposite films with the addition of 1.5% Spirulina residue and 5% PVA. Spirulina residue can be utilized as the plastic dyes.

Botryodiplodin (A Mycotoxin) detection in pathogenic Botryodiplodia theobromae isolated from diseased coconut fruits

Botryodiplodia theobromae is a threat to crops because it produces botryodiplodin, that plays a role in the initial stages of plant infection, creating necrotic areas through which it can easily penetrate. In addition, the botryodiplodin produced is not easily detected during quarantine, and other techniques developed to detect botryodiplodin are not easily practicable for screening numerous samples. Hence, the need to develop an in-culture pigment formation method to identify and differentiate toxigenic and non-toxigenic pathogenic isolates of B. theobromae. In this study, to detect botryodiplodin produced by isolates of B. theobromae, PDA, CDA and modified CDA media were used. Only the modified CDA medium enhanced the detection of botryodiplodin produced by B. theobromae isolates due to the addition of glycine into the medium. The effect of modified CDA composition or formulation, sucrose, and glycine concentrations on botryodiplodin detection were also evaluated. Study on the effect of the modified CDA composition on the detection of botryodiplodin produced by isolates of B. theobromae revealed that only sucrose stimulated the detection of botryodiplodin in comparison with other ingredients in the modified medium. In addition, the results from the study also reveals that increasing sucrose and glycine concentrations directly enhanced botryodiplodin detection, with optimum concentration of sucrose and glycine for detecting botryodiplodin by isolates of B. theobromae established at 15 and 10 g/l respectively. Hence, there is no need to increase the concentration of both sucrose and glycine above these established concentrations when preparing an in-culture medium for screening B. theobromae isolates capable of producing botryodiplodin.

Botryodiplodin (A Mycotoxin) detection in pathogenic Botryodiplodia theobromae isolated from diseased coconut fruits

Botryodiplodia theobromae is a threat to crops because it produces botryodiplodin, that plays a role in the initial stages of plant infection, creating necrotic areas through which it can easily penetrate. In addition, the botryodiplodin produced is not easily detected during quarantine, and other techniques developed to detect botryodiplodin are not easily practicable for screening numerous samples. Hence, the need to develop an in-culture pigment formation method to identify and differentiate toxigenic and non-toxigenic pathogenic isolates of B. theobromae. In this study, to detect botryodiplodin produced by isolates of B. theobromae, PDA, CDA and modified CDA media were used. Only the modified CDA medium enhanced the detection of botryodiplodin produced by B. theobromae isolates due to the addition of glycine into the medium. The effect of modified CDA composition or formulation, sucrose, and glycine concentrations on botryodiplodin detection were also evaluated. Study on the effect of the modified CDA composition on the detection of botryodiplodin produced by isolates of B. theobromae revealed that only sucrose stimulated the detection of botryodiplodin in comparison with other ingredients in the modified medium. In addition, the results from the study also reveals that increasing sucrose and glycine concentrations directly enhanced botryodiplodin detection, with optimum concentration of sucrose and glycine for detecting botryodiplodin by isolates of B. theobromae established at 15 and 10 g/l respectively. Hence, there is no need to increase the concentration of both sucrose and glycine above these established concentrations when preparing an in-culture medium for screening B. theobromae isolates capable of producing botryodiplodin.

The application of microwave and ultrasound treatment on breadfruit flour for noodle fortification

Breadfruit flour was subjected to treatment using either microwave radiation (1000 W, 16 min) or ultrasonic waves (20 kHz, 750 W, 16 min) before being combined with rice flour to produce dried rice–breadfruit noodles. Scanning electron microscopy and FT-IR spectroscopy were used to study alterations in the macrostructures and amylose/amylopectin arrangement of the treated flours, leading to changes in water adsorption and swelling power compared to originated flour. Noodles fortified with either microwave (M)- or ultrasound (U)-treated flour exhibited improved firmness and reduced cooking loss compared to those made with intact flour (Nf noodle), while noodles made from Nf combined with xanthan gum (Nf+X) demonstrated sufficient hardness and the lowest cooking loss. The addition of xanthan gum enhanced sensory scores, whereas scores for M, U, and Nf noodles were comparatively lower. Although M treatment potentially enhanced the noodle texture and cooking properties, it also resulted in darkening due to pigment formation at high temperatures.

Evaluation of Periodontal Status and Serum C-Reactive Protein Levels in Adult Cigarette Smokers

Background: This study aimed to evaluate the periodontal status of adult smokers and assess their serum C-reactive protein (CRP) levels, hypothesizing an association between periodontal inflammation, smoking, and elevated serum CRP, a marker for cardiovascular diseases. The primary objective is to contribute to the assessment and prevention of potential cardiovascular diseases in adult smokers. Methods: This cross-sectional study was conducted at HIT Hospital and Dental Hospital HITEC-IMS Taxila Cantt over five months from October 20, 2021, to March 31, 2022, the study included 60 healthy male adult smokers and 20 healthy male non-smokers as a control. Basic periodontal examination involved the use of a periodontal probe, assessing parameters such as gingival index, bleeding on probing, oral pigmentation, presence of periodontal pockets, and gingival recession. Blood samples were collected to evaluate serum CRP levels. Results: Smokers exhibited higher rates of gingival recession (38.3%), gingival pigmentation (43.3%), and periodontal pocket formation (33.3%) compared to the nonsmokers control group, with significant p-values of 0.040 in gingival recession and 0.035 in the presence of periodontal pockets. Serum CRP levels were significantly elevated in adult smokers, with a significant p-value of 0.024. Conclusion: The study concluded that adult smokers show signs of periodontitis, and their serum CRP levels are elevated. Assessing periodontal status and serum CRP in adult smokers may aid in risk assessment and reducing the likelihood of developing future cardiovascular diseases.

Antimicrobial and anti-virulence activities of 4-shogaol from grains of paradise against gram-negative bacteria: Integration of experimental and computational methods

Ethnopharmacological relevanceBacterial resistance to antibiotics is a growing global concern, highlighting the urgent need for new antimicrobial candidates. Aframomum melegueta was traditionally used for combating urinary tract and soft tissue infections, which implies its potential as an antimicrobial agent. Aim of studyThis study was designed to explore the antibacterial and anti-virulence capabilities of 4-shogaol isolated from A. melegueta seeds versus gram-negative bacteria: Serratia marcescens, Klebsiella pneumoniae, Acinetobacter baumannii, and the clinically important pathogen Pseudomonas aeruginosa. Materials and methods4-Shogeol was isolated from A. melegueta seeds and its MICs were determined for Acinetobacter baumannii (ATCC-17978), Pseudomonas aeruginosa (ATCC-27853), Klebsiella pneumoniae (ATCC-700603), and Serratia marcescens clinical isolate. The anti-efflux activity and effect on the bacterial cell membrane for the compound were evaluated. Furthermore, the anti-virulence activities of the compound were evaluated. The effects of 4-shogeol at sub-MIC on bacterial motility, biofilm formation, and production of virulent enzymes and pigments were assessed. The anti-quorum sensing activities of 4-shogeol were evaluated virtually and by quantification its effect on the expression of quorum sensing encoding genes. The in vivo protection assay was conducted to evaluate the effect of 4-shogaol on the P. aeruginosa capacity to induce pathogenesis in mice. Finally, the effect of shogaol-antibiotics combination was assessed. ResultsThe research revealed that 4-shogaol's antibacterial action primarily involves disrupting the bacterial cell membrane and efflux pumps. It also exhibited significant anti-virulence effects by reducing biofilm development and repressing virulence factors production, effectively protecting mice against P. aeruginosa infection. Furthermore, when combined with antibiotics, 4-shogaol demonstrated synergistic effects, leading to reduced minimum inhibitory concentrations (MICs) against P. aeruginosa. Its anti-virulence properties were linked to its ability to disrupt bacterial quorum sensing (QS) mechanisms, as evidenced by its interaction with QS receptors and downregulation of QS-related genes. Notably, in silico analysis indicated that 4-shogaol exhibited strong binding affinity to different P. aeruginosa QS targets. ConclusionThese findings suggest that 4-shogaol holds promise as an effective anti-virulence agent that can be utilized in combination with antibiotics for treating severe infections caused by gram-positive bacteria.

Soluble meso and deuteroporphyrin analogs of the malaria pigment hematin anhydride

Two soluble heme analogs of the insoluble malaria pigment hematin anhydride (HA, or β-hematin), [Fe(III)(protoporphyrin)]2, with either mesoporphyrin (MHA) or deuteroporphyrin (DHA) are characterized by elemental analysis, SEM, IR spectroscopy, electronic spectroscopy, paramagnetic 1H NMR spectroscopy and solution magnetic susceptibility. While prior single crystal and X-ray powder diffraction results indicate all three have a common propionate linked dimer motif, there is considerable solid state variation in the conformation. This is associated with enhanced solubility of MHA and DHA. As with HA, DHA undergoes thermally promoted reversible hydration/dehydration in the solid state. Solution 1H NMR studies of DHA suggest a high spin dimeric structure with the porphyrin methyls distributed between two isomers which are also present in the solid state. These soluble iron(III)porphyrin dimers allow for the first direct solution studies by NMR and UV–Vis spectroscopies of these key species. Taken together the results illustrate the importance and utility of varying the substituents on the periphery of the porphyrin for studying heme aggregation and malaria pigment formation.

Mitf involved in shell pigmentation by activating tyrosinase-mediated melanin synthesis in Pacific oyster (Crassostrea gigas)

Pigmentation is frequently observed in the molluscan shells, whereas the molecular regulation about these shell pigments formation is not clear. The microphthalmia-associated transcription factor (Mitf) is an important transactivator in melanin synthesis in vertebrates. Here, the Mitf containing a highly conserved basic helix-loop-helixleucine zipper (bHLH-LZ) domain was identified in an economically important marine bivalve Pacific oyster Crassostrea gigas. The Mitf was found to widespread tissue distribution and the expression was higher in the marginal mantle than in the central mantle. Particularly, the expression level of Mitf was high in black shell color oysters compared with white shell oysters. After injecting siRNA, the expression of Mitf decreased significantly, and the efficiency of RNA interference reached 53%. Besides, knockdown Mitf obviously decreased expression of tyrosinase family genes and tyrosinase activity of mantles, indicating a potential regulatory relationship between Mitf and Tyr or Typs. Simultaneously, there was a sharply reduce in the number of the melanosomes in the outer fold of mantle by silencing of Mitf. Luciferase assays in cell culture further verified that Mitf was involved in transcriptional regulation of Typ-2 and Typ-3 genes through binding to their specific promoter regions. These data argue that Mitf is involved in shell pigmentation through activating tyrosinase-mediated melanin synthesis in C. gigas.

Green technologies applied to low-NaCl fresh sausages production: Impact on oxidative stability, color formation, microbiological properties, volatile compounds, and sensory profile

The influence of different concentrations of NaCl (2.5% and 1.75%), basic electrolyzed water (BEW), and ultrasound (US, 25 kHz, 159 W) on the quality of fresh sausages was studied. During storage at 5 °C, TBARS, pH, Eh, aw, nitrous pigments, and bacterial evolution were evaluated at three specific time intervals: 1d, 15d, and 30d. At the same time, the volatile compounds and sensory profile were specifically assessed on both the 1d and 30d. Notably, sausages with 1.75% NaCl and BEW displayed higher pH values (up to 6.30) and nitrous pigment formation, alongside reduced Eh (as low as 40.55 mV) and TBARS values (ranging from 0.016 to 0.134 mg MDA/kg sample), compared to the 2.5% NaCl variants. Protein content ranged between 13.01% and 13.75%, while lipid content was between 18.23% and 18.86%, consistent across all treatments. Psychrotrophic lactic bacteria showed a significant increase in low-NaCl sausages, ranging from 5.77 to 7.59 log CFU/g, indicative of potential preservative benefits. The sensory analysis favored the TUSBEW70 treatment for its salty flavor on the 30th day, reflecting a positive sensory acceptance. The study highlights that employing US and BEW in sausage preparation with reduced NaCl content (1.75%) maintains quality comparable to higher salt (2.5%) counterparts. These findings are crucial for meat processing, presenting a viable approach to producing healthier sausages with reduced sodium content without compromising quality, aligning with consumer health preferences and industry standards.

The secrets of environmental Pseudomonas aeruginosa in slaughterhouses: Antibiogram profile, virulence, and antibiotic resistance genes.

Environmental pollution is a serious problem that can cause sicknesses, fatality, and biological contaminants such as bacteria, which can trigger allergic reactions and infectious illnesses. There is also evidence that environmental pollutants can have an impact on the gut microbiome and contribute to the development of various mental health and metabolic disorders. This study aimed to study the antibiotic resistance and virulence potential of environmental Pseudomonas aeruginosa (P. aeruginosa) isolates in slaughterhouses. A total of 100 samples were collected from different slaughterhouse tools. The samples were identified by cultural and biochemical tests and confirmed by the VITEK 2 system. P. aeruginosa isolates were further confirmed by CHROMagar™ Pseudomonas and genetically by rpsL gene analysis. Molecular screening of virulence genes (fimH, papC, lasB, rhlI, lasI, csgA, toxA, and hly) and antibiotic resistance genes (blaCTX-M, blaAmpC, blaSHV, blaNDM, IMP-1, aac(6')-Ib-, ant(4')IIb, mexY, TEM, tetA, and qnrB) by PCR and testing the antibiotic sensitivity, biofilm formation, and production of pigments, and hemolysin were carried out in all isolated strains. A total of 62 isolates were identified as P. aeruginosa. All P. aeruginosa isolates were multidrug-resistant and most of them have multiple resistant genes. blaCTX-M gene was detected in all strains; 23 (37.1%) strains have the ability for biofilm formation, 33 strains had virulence genes, and 26 isolates from them have more than one virulence genes. There should be probably 60 (96.8%) P. aeruginosa strains that produce pyocyanin pigment. Slaughterhouse tools are sources for multidrug-resistant and virulent pathogenic microorganisms which are a serious health problem. Low-hygienic slaughterhouses could be a reservoir for resistance and virulence genes which could then be transferred to other pathogens.

Anti-Quorum Sensing and Anti-Biofilm Activity of Ginger (Zingiber officinale) Rhizomes against Multidrug-Resistant Clinical Isolates of Pseudomonas aeruginosa.

The aim of this study was to determination of Anti-Quorum Sensing (AQS) and anti-biofilm potential of the methanol extract of ginger (Zingiber officinale) rhizomes against multidrug-resistant clinical isolates of Pseudomonas aeruginosa (P. aeruginosa). The AQS activity of ginger was determined against Chromobacterium violaceum (C. violaceum) ATCC 12472 (CV12472), a biosensor strain, in qualitative manner using the agar well diffusion method. The violacein pigment inhibition was assessed to confirm AQS activity of ginger. The AQS potential of sub-minimum Inhibitory Concentrations (sub-MICs) of the ginger extract was determined by targeting different QS regulated virulence factors, including swarming motility (using swarm diameter measurement method), pyocyanin pigment (using chloroform extraction method), Exopolysaccharide (EPS) (using phenol-sulphuric acid method), and biofilm formation (using microtiter plate assay), against clinical isolates (CIs 2, 3, and 4) and standard reference strain of P. aeruginosa (PA01). The AQS activity of methanol extract of ginger was confirmed against C. violaceum (CV12472) as inhibition of violacein pigment formation without effecting the growth of CIs and PA01 of P. aeruginosa. The ginger extract exhibited concentration-dependent inhibition of virulence factors and biofilm formation. The maximum reduction was found in swarming motility, pyocyanin, EPS and biofilm formation against PA01 (51.38%), CI3 (57.91%), PA01 (63.29%) and CI2 (64.37%), respectively at 1/2 MIC of ginger extract. The results of present study revealed the effective AQS and anti-biofilm potential of Zingiber officinale rhizome methanol extract at a reduced dose (sub-MICs). The extract may be explored as an agent of antimicrobial compounds having AQS and anti-biofilm activity for controlling microbial infection and also for reducing the chances of emergence of resistance in P. aeruginosa.

Observations on the embryonic development of the mud crab, Scylla paramamosain

To investigate the embryonic development of the mud crab Scylla paramamosain, we analyzed three critical parameters: egg color of, embryo morphology (through conventional and laser scanning confocal microscopy), and the distribution of cell divisions. During embryonic development, the egg color exhibited a progressive transition, shifting from orange to reddish-orange, then to brown, before ultimately darkening to black. Each embryo displayed a spherical shape, measuring approximately 280 μm in diameter, characterized by a smooth surface devoid of any depressions. The embryonic cell division was in the form of mixed oogenesis, comprised of complete division in the early stage, spiral oogenesis in the middle stage and surface division in the late stage. It is noteworthy that the blastopore appeared at the position where the transparent area and cell aggregation just appeared under the microscope, and the blastomere was a characteristic of the embryo entering the gastrulation stage. After entering the gastrulation stage, the cells aggregated towards the blastopore and formed two symmetrical cell clusters, which formed a V-shape with the void of the classic blastopore. When the transparent region occupied approximately 1/5 of the embryo’s volume, the embryo entered the nauplius stage, and the thoracic and abdominal armor, as well as the optic lobe and abdominal limb primordia, could be clearly distinguished. The appearance of the compound eye pigment band indicated the stage of compound eye pigment formation. At this time, the transparent area accounted for 1/4 of the embryo and a large number of ganglia appeared. The change of the compound eye pigment band from red to black was also one of the reasons for the blackening of the egg color of the crabs. The data obtained through this study have potential applications in the determination of embryonic development status and obtaining of high-quality seeds for S. paramamosain culture.

Analyzing Morphology, Metabolomics, and Transcriptomics Offers Invaluable Insights into the Mechanisms of Pigment Accumulation in the Diverse-Colored Labellum Tissues of Alpinia.

Alpinia plants are widely cherished for their vibrant and captivating flowers. The unique feature of this genus lies in their labellum, a specialized floral structure resulting from the fusion of two non-fertile staminodes. However, the intricate process of pigment formation, leading to distinct color patterns in the various labellum segments of Alpinia, remains a subject of limited understanding. In this study, labellum tissues of two Alpinia species, A. zerumbet (yellow-orange flowers) and A. oxyphylla (white-purple flowers), were sampled and analyzed through morphological structure observation, metabolite analysis, and transcriptome analyses. We found that hemispherical/spherical epidermal cells and undulate cell population morphology usually display darker flower colors, while flat epidermal cells and cell populations usually exhibit lighter flower colors. Metabolomic analysis identified a high concentration of anthocyanins, particularly peonidin derivatives, in segments with orange and purple pigments. Additionally, segments with yellow pigments showed significant accumulations of flavones, flavanols, flavanones, and xanthophylls. Furthermore, our investigation into gene expression levels through qRT-PCR revealed notable differences in several genes that participated in anthocyanin and carotenoid biosynthesis among the four pigmented segments. Collectively, these findings offer a comprehensive understanding of pigmentation in Alpinia flowers and serve as a valuable resource for guiding future breeding efforts aimed at developing Alpinia varieties with novel flower colors.

Connectivity of Photosynthesis and Respiration with Content of Chlorophyll Pigments in Plants of Reed Fescue <i>Festuca arundinacea</i> Schreb. Under the Impact of Alkanes and Aromatic Hydrocarbons

The association of degradation of membrane-bound chlorophyll with changes in dark respiration rates and photosynthesis in Festuca arundinacea Schreb. leaves under the influence of various concentrations of limit and aromatic hydrocarbons present in technogenic emissions was studied. 1 day after intoxication a negative correlation between the content of non-phytol forms of pigments and the rate of photosynthesis was found. Positive correlation was found between the content of: 1) phytol forms and the rate of photosynthesis; 2) non-phytol forms and respiration rate. The relationships between the processes changed after 3 days characterizing the detoxifying and adaptability of plants.

Yellow pigments produced by oxidative oligomerization of dihydrochalcone glucoside and the reaction mechanism.

From the dried leaves of Lithocarpus polystachyus, yellow pigments, lithocarputins B (11) and C (12), were isolated with a colorless dihydrochalcone dimer, lithocarputin A (10). The pigments 11 and 12 are dimeric dihydrochalcone glycosides with bicyclo[3.2.1]octane structures. Each pigment is a diastereomeric mixture with enantiomeric aglycones that could not be separated. The production mechanisms of the pigments were proposed based on the in vitro enzymatic preparation from trilobatin (1), the major dihydrochalcone glucoside of L. polystachyus. The majority of the pigments in the dried leaves were the oligomers of the dihydrochalcone glycosides generated by a mechanism similar to dimerization. The pigments are probably artifacts produced in the drying process. This is the first report disclosing a detailed chemical mechanism for pigment formation from dihydrochalcone.

Sub-lethal concentration of a colloidal nanosilver formulation (Silversol®) triggers dysregulation of iron homeostasis and nitrogen metabolism in multidrug resistant Pseudomonas aeruginosa

BackgroundPseudomonas aeruginosa is a notorious pathogen. Its multidrug resistant strains are listed among priority pathogens against whom discovery of novel antibacterial agents and, elucidation of new anti-pathogenicity mechanisms are urgently warranted. This study describes multiple antibacterial effects of a colloidal nano-silver formulation- Silversol® against a multi-drug resistant strain of P. aeruginosa.ResultsMinimum inhibitory concentration (MIC) of Silversol® against P. aeruginosa was found to be 1.5 ppm; and at sub-MIC of 1 ppm, it was able to alter quorum-sensing regulated pigmentation (pyocanin 82%↓; pyoverdine 48%↑), exopolysaccharide synthesis (76%↑) and biofilm formation, susceptibility to antibiotics (streptomycin and augmentin), protein synthesis and export (65%↑), nitrogen metabolism (37%↑ nitrite accumulation), and siderophore production in this pathogen. Network analysis of the differentially expressed genes in the transcriptome of the silversol-treated bacterium identified ten genes as the potential molecular targets: norB, norD, nirS, nirF, nirM, nirQ, nosZ, nosY, narK1, and norE (all associated with nitrogen metabolism or denitrification). Three of them (norB, narK1, and norE) were also validated through RT-PCR.ConclusionsGeneration of nitrosative stress and disturbance of iron homeostasis were found to be the major mechanisms associated with anti-Pseudomonas activity of Silversol®.

Comprehensive metabolome and transcriptome analyses demonstrate divergent anthocyanin and carotenoid accumulation in fruits of wild and cultivated loquats.

Eriobotrya is an evergreen fruit tree native to South-West China and adjacent countries. There are more than 26 loquat species known in this genus, while E. japonica is the only species yet domesticated to produce fresh fruits from late spring to early summer. Fruits of cultivated loquat are usually orange colored, in contrast to the red color of fruits of wild E. henryi (EH). However, the mechanisms of fruit pigment formation during loquat evolution are yet to be elucidated. To understand these, targeted carotenoid and anthocyanin metabolomics as well as transcriptomics analyses were carried out in this study. The results showed that β-carotene, violaxanthin palmitate and rubixanthin laurate, totally accounted for over 60% of the colored carotenoids, were the major carotenoids in peel of the orange colored 'Jiefangzhong' (JFZ) fruits. Total carotenoids content in JFZ is about 10 times to that of EH, and the expression levels of PSY, ZDS and ZEP in JFZ were 10.69 to 23.26 folds to that in EH at ripen stage. Cyanidin-3-O-galactoside and pelargonidin-3-O-galactoside were the predominant anthocyanins enriched in EH peel. On the contrary, both of them were almost undetectable in JFZ, and the transcript levels of F3H, F3'H, ANS, CHS and CHI in EH were 4.39 to 73.12 folds higher than that in JFZ during fruit pigmentation. In summary, abundant carotenoid deposition in JFZ peel is well correlated with the strong expression of PSY, ZDS and ZEP, while the accumulation of anthocyanin metabolites in EH peel is tightly associated with the notably upregulated expressions of F3H, F3'H, ANS, CHS and CHI. This study was the first to demonstrate the metabolic background of how fruit pigmentations evolved from wild to cultivated loquat species, and provided gene targets for further breeding of more colorful loquat fruits via manipulation of carotenoids and anthocyanin biosynthesis.