Color me bad: microbial pigments as virulence factors

Effect of dichloromethanolic fraction obtained from the medicinal plant Scutellaria luteocaerulea on growth, reactive oxygen species, and some virulence factors of Fusarium spp. associated with bread wheat diseases

Dichlomethane (DCM) extract from the roots of Scutellaria luteocaerulea (skullcap) showed in vitro antifungal activity against Fusarium pseudograminearum and Fusarium culmorum, with IC50 values of 550 and 450 μg mL-1, respectively. Additionally, the effects of S. luteocaerulea on hyphal structures of the pathogens, spore germination, and mycelial growth were studied. According to the data obtained, the extract of S. luteocaerulea inhibited spore germination and mycelial growth of both pathogens tested. Additionally, the pathogens hyphae and spores were deformed when treated with the extract of S. luteocaerulea. Induced apoptotic characteristics were detected in both pathogens via the addition of the DCM fraction of S. luteocaerulea into the culture. The DCM fraction of S. luteocaerulea induced the production of reactive oxygen species (ROS) in both pathogens, as a characteristic of apoptosis. Activities of cell wall degrading enzymes (CWDEs) and production of deoxynivalenol (DON) were reduced. Also, the effect of the DCM fraction of S. luteocaerulea was investigated on the severity of Fusarium crown rot (FCR) and Fusarium head blight (FHB) diseases caused by both fungi on bread wheat. Plants treated with the DCM fraction of S. luteocaerulea showed an increased 1000-grain weight and decreased disease progress in greenhouse conditions. High performance liquid chromatography (HPLC) analysis revealed that the fraction had high concentration of wogonin. Therefore, the DCM fraction obtained from S. luteocaerulea could potentially be used in the future to protect wheat plants against F. pseudograminearum and F. culmorum.

Unraveling Antibacterial Mechanisms of Surfactants against Staphylococcus aureus via Single-Cell Raman Spectroscopy

Antibacterial agents, particularly surfactants, play crucial roles in the personal and home care industries. However, current methods for assessing their efficacy and mechanism are commonly time-consuming and expensive. Here, we established a ramanome-based approach to investigate the antibacterial mechanisms of cationic and anionic surfactants with varying alkyl chain lengths against Staphylococcus aureus as a model. Our findings further elucidate the synergy between anionic surfactants and acidic pH. Cell membrane integrity was disrupted by all of the surfactants, as revealed by the decrease in Raman bands assigned to major cellular components (nucleic acids, proteins, and cytochrome), leading to the leakage of cellular components. Moreover, the composition of the cell membrane was altered due to insertion of cationic surfactant, evidenced by the emergence of surfactant-characteristic bands in the spectrum of S. aureus; yet this was observed only under acidic conditions for anionic surfactants. Remarkably, changes in Raman bands of staphyloxanthin and S═O which are biomarkers of cellular oxidative states revealed that acidic conditions accelerated cell death induced by the anionic surfactant. These findings illustrate distinct mechanisms of action for cationic and anionic surfactants and suggest that ramanomics offers a rapid, low-cost, comprehensive, and mechanism-revealing approach for the assessment and screening of surfactants.

Control of Fungal Spores on Surfaces with UV-C Exposure Necessitates Complete Inactivation to Prevent Mycorrhizal Network Establishment

Mold infestations on surfaces present significant challenges to public health. Germicidal UV-C irradiation effectively inactivates spores suspended in water, yet information on surface spore mitigation is surprisingly absent. We show the effectiveness of 265-275 nm UV-C light to mitigateAspergillus nigeron nutrient-rich surfaces. UV-C mitigation of surface molds differs from inactivating spores suspended in water due to the unique characteristics of mycelial structures. Complete preinactivation of all viable cells during UV-C exposure is crucial to prevent mycelia formation; otherwise, even a single spore can gradually spread, covering surfaces by producing a progressive mycelial structure. A UV-C dose of 144 mJ/cm2 from 265 nm LEDs achieved complete preinactivation at lower concentrations (100-1000 CFU/plate), while higher concentrations required increased UV-C doses. Intermittent duty cycling of light delivery (10 min ON then 50 min OFF) at 275 nm delivered from side-emitting optical fibers achieved comparable mitigation to continuous irradiation. Insufficient UV-C exposure induced more resistant mycelial structures that shielded live spores beneath. This study highlights complete preinactivation of viable molds, or sustained inhibition by UV-C light, is more effective than UV-C posttreatment. Mycelial alteration triggered by sublethal stress helps spores to persist in unfavorable environments, where microbial control is the goal.

Imipenem/cilastatin encapsulation in UIO-66-NH2 carrier as a new strategy for combating imipenem-resistant Pseudomonas aeruginosa isolates

BACKGROUND

This study aims to investigate the effectiveness of UIO-66-NH2, a metal-organic framework, as a carrier for imipenem/cilastatin (Imp/Cil) in overcoming resistance in clinical isolates of imipenem-resistant Pseudomonas aeruginosa.

METHODS

The UIO-66-NH2-Imp/Cil formulations were synthesized and characterized using dynamic light scattering, scanning electron microscopy, and transmission electron microscopy. Drug entrapment efficiency of UIO-66-NH2-Imp/Cil, and Imp/Cil release rates were determined. The stability of formulations was assessed at room temperature and refrigeration for two months. The antibacterial, anti-biofilm, and anti-virulence activities of formulations were investigated against imipenem-resistant P. aeruginosa isolates.

RESULTS

The UIO-66-NH2-Imp/Cil formulation showed an average particle size of 212.3 ± 7.3 nm, a polydispersity index of 0.142 ± 0.010, and an entrapment efficiency (EE%) of 74.19% ± 1.12%. Drug release from the formulation followed a Korsmeyer-Peppas kinetic model, with 52% of the drug released over 72 h. Antibacterial testing indicated a significant decrease in minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for the UIO-66-NH2-Imp/Cil formulation compared to free Imp/Cil, demonstrating enhanced antibacterial activity. Furthermore, the anti-biofilm and anti-virulence activity of UIO-66-NH2-Imp/Cil was confirmed by the reduction of bacterial haemolysis activity, minimal pyocyanin, EPS (extracellular polymeric substance) production, and lower metabolic activity of pathogens. Also, UIO-66-NH2-Imp/Cil causes significant reduction in the expression of lasA, lasB and, rhlA genes, which resulted in the inhibition of quorum-sensing system activity.

CONCLUSIONS

These findings indicate that UIO-66-NH2-Imp/Cil nanocarriers offer a promising new approach against multidrug-resistant Gram-negative pathogens, providing insights into potential mechanisms of antimicrobial action.

Quercetin Exhibits Broad-Spectrum Antibiofilm and Antiquorum Sensing Activities Against Gram-Negative Bacteria: In Vitro and In Silico Investigation Targeting Antimicrobial Therapy

Quercetin (QC), a flavonoid abundant in fruits and vegetables, has garnered attention for its potential therapeutic properties. In this study, we investigated the antibiofilm and antiquorum sensing (QS) activities of QC against Gram-negative bacteria both in vitro and in silico. The findings of this study demonstrate MIC values of 125 μg/mL for Chromobacterium violaceum, 250 μg/mL for Pseudomonas aeruginosa, and 500 μg/mL for Serratia marcescens, indicating its antibacterial potential abilities. QS-mediated production of violacein and prodigiosin was significantly inhibited in a dose-dependent manner at sub-MIC concentrations. Additionally, a dose-dependent reduction in the virulence factors of P. aeruginosa, including production of pyocyanin, pyoverdine, and rhamnolipid, was noted with QC. Biofilm formation decreased by 66.40%, 59.28%, and 63.70% at the highest sub-MIC for C. violaceum, P. aeruginosa, and S. marcescens, respectively. Furthermore, swimming motility and exopolysaccharide (EPS) production were also reduced in the presence of QC. Additionally, molecular docking and molecular dynamics simulations elucidate the binding interactions between QC and key molecular targets (LasI, LasR, PilY1, LasA, PilT, CviR, CviR', PqsR, RhlR, and PigG) involved in biofilm formation and QS pathways. Our results indicated that the antibiofilm and anti-QS sensing activities of QC may be attributed to its ability to interfere with critical signaling molecules and regulatory proteins. Overall, this study highlights QC as a promising natural compound for combating biofilm-associated infections caused by Gram-negative bacteria. The multifaceted antimicrobial mechanisms of QC underscore its potential as a therapeutic agent for the treatment of biofilm-related infections, providing the way for further exploration, and development of QC-based strategies in antimicrobial therapy.

Use of analytical strategies to understand spatial chemical variation in bacterial surface communities

Not only do surface-growing microbes such as biofilms display specific traits compared to planktonic cells, but also they display many heterogeneous behaviors over many spatial and temporal contexts. While the application of molecular genetics tools to extract or visualize gene expression or regulatory function data is now common in studying surface growth, the use of analytical chemistry tools to visualize the spatiotemporal distribution of chemical products synthesized by these surface microbes is less common. Here, we review chemical imaging tools that have been used to inform our understanding of surface-growing microbes. We highlight the use of confocal Raman Microscopy, surface-enhanced Raman spectroscopy, matrix-assisted laser desorption/ionization, secondary ion mass spectrometry, desorption electrospray ionization, and electrochemical imaging that have been applied to assess two-dimensional chemical profiles of bacteria. We specifically discuss the use of these tools to study rhamnolipids, alkylquinolones, and phenazines of the bacterium Pseudomonas aeruginosa.

A case of disseminated autochthonous Cladophialophora bantiana infection in a renal transplant recipient in the UK

Disease associated with Cladophialophora bantiana infection is uncommon but can be characterised by severe and life-threatening CNS involvement. Diagnosis is challenging due to both the infection's rarity and non-specific clinical presentation, which can mimic malignancy and infection caused by more common organisms. Transmission can occur via inhalation or inoculation through compromised skin, followed by haematogenous dissemination to the brain and other organs. We report a case of a 42-year-old renal transplant recipient with no travel history presenting with neurological symptoms and skin and lung lesions due to C bantiana infection. An aggressive treatment approach comprising combination antifungal therapy, surgical debridement, and withdrawal of immunosuppression resulted in disease control, although this treatment was complicated by voriconazole-induced skeletal fluorosis. This organism, more commonly encountered in tropical regions, has traditionally been considered imported into the UK by returning travellers, therefore this case of autochthonous infection could reflect an expanding range alongside global climactic shifts.

The sensor protein VdSLN1 is involved in regulating melanin biosynthesis and pathogenicity via MAPK pathway in Verticillium dahliae

The vascular wilt fungus Verticillium dahliae is a destructive soil-borne pathogen that causes yield loss on various economically important crops. Membrane-spanning sensor protein SLN1 have been demonstrated to contribute to virulence in varying degrees among numerous devastating fungal pathogens. However, the biological function of SLN1 in V. dahliae remains unclear. In this study, we identified the membrane-spanning sensor protein encoding gene VdSLN1 and it interacts physically with Vst50 and regulates the expression of MAPK module Vst50-Vst11-Vst7. The expression of VdSLN1 was also positively regulated by the MAPK signaling pathways transmembrane-associated members VdSho1 and VdMsb2, suggesting that the expression of VdSLN1 is associated with VdSho1 and VdMsb2. In addition, we found that VdSLN1, similar to VdSho1 and VdMsb2, is not required for V. dahliae vegetative growth and response to various abiotic stresses. While, ΔVdSLN1 mutant exhibited slightly reduced ability to penetrate a cellophane membrane and melanin synthesis compared with the wild type strain. Further experiments indicate that VdSLN1, VdSho1 and VdMsb2 has an additive effect on the virulence, cellophane penetration and melanin biosynthesis and of V. dahliae. In short, VdSLN1, though not essential, plays a role in cellophane penetration, melanin biosynthesis, also contributes to the virulence, as the downstream factor of VdSho1 and VdMsb2.

Control of Staphylococcus aureus infection by biosurfactant derived from Bacillus rugosus HH2: Strain isolation, structural characterization, and mechanistic insights

Novel antimicrobials are urgently needed to combat methicillin-resistant Staphylococcus aureus (MRSA) infections. This study explores the potential of biosurfactants derived from Bacillus rugosus HH2 as a novel antibacterial agent against MRSA. The biosurfactant, identified as surfactin, demonstrated surface-active properties, reducing surface tension to 37.63 mN/m and lowering contact angles in a concentration-dependent manner. It remained stable across a wide range of pH (4-10), temperatures (30-80 °C), and salinity levels (3-18 %). The biosurfactant inhibited the growth of both methicillin-sensitive S. aureus and MRSA, with minimum inhibitory concentrations ranging from 128 to 256 μg/mL. Additionally, it showed anti-biofilm activity, preventing biofilm formation and dispersing established biofilms. Field-emission scanning electron microscopy revealed that the biosurfactant disrupted bacterial cell membranes, leading to leakage. Furthermore, it reduced the production of virulence factors in S. aureus, including hemolysin and lipase. Transcriptomic analysis indicated downregulation of genes associated with quorum sensing and cell adhesion in MRSA. Molecular docking studies showed strong interactions between surfactin and key MRSA proteins, underscoring its potential to overcome antibiotic resistance. Biocompatibility was confirmed through in vitro cytotoxicity and in vivo phytotoxicity tests. In summary, this study presents surfactin as a promising novel antibacterial agent against MRSA, providing insights into its mechanisms of action.

Antimicrobial Activity of Melanin Isolated from Wine Waste

Melanins have immense application potential in the fields of agriculture, cosmetics and pharmaceutical industries. To determine the antimicrobial properties of melanin, conditionally pathogenic bacteria, belonging to different taxonomic groups were used. The results have shown that melanin solution exhibited bacteriostatic or bactericide activity depending on test culture and melanin concentration. Melanin at concentration of 20 mg/ml reduced the total number of cells of the Bacillus subtilis G 17-89, Salmonella typhimurium G 38 and Escherichia coli K 12 to about 20 percent. Melanin at the concentration of 40 mg/ml suppressed the growth of B. subtilis G17-89 and Candida gropengiesseri 10228 almost 100 percent. In the case of E. coli K 12 30 mg/ml concentration has the same effect as the 40 mg/ml and cell count decrease occurs about 50 percent. Lowest efficiency melanin showed against S. typhimurium G 38 and after 72 h of incubation the cell count decreases by log 1 degree. 30 mg/ml concentration of melanin on the growth of Candida bovina 10118 decreases about 80 percent. On the growth of the Fungi of Aspergillus fumigatus 8444, Aspergillus flavus 10559, Cladosporium herbarium 8270, Cladosporium elatum 8192, Fusarium oxysporum 12017, Fusarium solani 12018, Mucor hiemalis 12020, Mucor plumbeus 12021, Penicillium chrysogenum 8203, Penicillium expansum 8281 genus low concentration of melanin possessed bacteriostatic activity. The investigation of the efficiency of melanin to inhibit the growth of food-spoilage microorganisms shown, that it can be used as natural preservative agent for prevention contamination of food products and for extending of their shelf-life.

Synthesis, characterization and application of microbial pigments in foods as natural colors

Colorants have played a crucial role in various applications, particularly in food processing, with natural sources such as mineral ores, plants, insects, and animals being commonly used. However, the nineteenth century saw the development of synthetic dyes, which replaced these natural colorants. In recent years, there has been a growing demand for natural products, driving an increased interest in natural colorants. Microbial pigments have emerged as promising sources of natural pigments due to their numerous health benefits. They can be produced in large quantities rapidly and from more affordable substrates, making them economically attractive. This review focuses on the current advancements in the low-cost synthesis of microbial pigments, exploring their biological activities and commercial applications. Microbial pigments offer a sustainable and economically viable alternative to natural and synthetic colorants, meeting the growing demand for natural products. These pigments are relatively nontoxic and exhibit significant health benefits, making them suitable for a wide range of applications. As interest in natural products continues to rise, microbial pigments hold great potential in shaping the future of colorant production across various sectors.

Low concentrations of tetrabromobisphenol A promote the biofilm formation of methicillin-resistant Staphylococcus aureus

The effect and underlying mechanism of tetrabromobisphenol A (TBBPA), a plastic additive, on biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA USA300) remain unknown. This study first investigated the impact of different concentrations of TBBPA on the growth and biofilm formation of USA300. The results indicated that a low concentration (0.5 mg/L) of TBBPA promoted the growth and biofilm formation of USA300, whereas high concentrations (5 mg/L and 10 mg/L) of TBBPA had inhibitory effects. Further exploration revealed that the low concentration of TBBPA enhance biofilm formation by promoting the synthesis of extracellular proteins, release of extracellular DNA (eDNA), and production of staphyloxanthin. RTqPCR analysis demonstrated that the low concentration of TBBPA upregulated genes associated with extracellular protein synthesis (sarA, fnbA, fnbB, aur) and eDNA formation (atlA) and increased the expression of genes involved in staphyloxanthin biosynthesis (crtM), suggesting a potential mechanism for enhanced resistance of USA300 to adverse conditions. These findings shed light on how low concentrations of TBBPA facilitate biofilm formation in USA300 and highlight the indirect impact of plastic additives on pathogenic bacteria in terms of human health. In the future, in-depth studies about effects of plastic additives on pathogenicity of pathogenic bacteria should be conducted. CAPSULE: The protein and eDNA contents in biofilms of methicillin-resistant Staphylococcus aureus are increased by low concentrations of TBBPA.

Structural characterization of tyrosinases and an update on human enzymes

Tyrosinase, a pivotal enzyme in melanin biosynthesis, orchestrates the pigmentation process in humans, affecting skin, hair, and eye color. This chapter examines the three-dimensional structure and functional aspects of tyrosinases from various sources, highlighting their di-metal ion coordination crucial for catalytic activity. I explore the biochemical pathwayscheme catalyzed by tyrosinase, specifically the oxidation of L-tyrosine to L-dopaquinone, a precursor in melanin synthesis. Detailed structural analyses, including 3D structures obtained from X-ray crystallography and computational modeling, reveal key insights into the enzyme's active site, variations among tyrosinases, and substrate binding mechanisms. Furthermore, the chapter investigates the role of human tyrosinase variants, their inhibitors, essential for developing therapeutic and cosmetic applications targeting hyperpigmentation disorders. Structural characterizations of tyrosinase-inhibitor complexes provide a foundation for designing effective inhibitors, with compounds like kojic acid, L-mimosine, and (S)-3-amino-tyrosine demonstrating significant inhibitory potential. This comprehensive examination of the structure, function, and inhibition mechanisms of tyrosinase offers avenues for innovative treatments in biotechnology, health, and beyond.

Design, Synthesis, and Biological Evaluation of 2-Phenoxyalkylhydrazide Benzoxazole Derivatives as Quorum Sensing Inhibitors with Strong Antibiofilm Effect

With the increasing problem of bacterial resistance to traditional antibiotics, there is an urgent need for new antibacterial agents with novel mechanisms to treat infections caused by drug-resistant bacteria. In this paper, we designed and synthesized 2-phenoxyalkylhydrazide benzoxazole derivatives and evaluated their quorum sensing inhibition activity. Among them, 26c at a concentration of 102.4 μg/mL not only inhibited the production of pyocyanin and rhamnolipid by 45.6% and 38.3%, respectively, but also suppressed 76.6% of biofilm production at 32 μg/mL. In addition, 26c did not affect bacterial growth, but in a mouse model infected with P. aeruginosa PAO1, it could help ciprofloxacin effectively eliminate the living bacteria. In the targeting experiment, 26c could inhibit the fluorescence intensity of PAO1-lasB-gfp and PAO1-pqsA-gfp in a concentration-dependent manner, indicating that the compound acts on the quorum sensing system. Overall, 26c is worthy of further investigation as a quorum sensing inhibitor with strong antibiofilm effect.

The role of staphyloxanthin in the regulation of membrane biophysical properties in Staphylococcus aureus

Staphylococcus aureus is an opportunistic pathogen that is considered a global health threat. This microorganism can adapt to hostile conditions by regulating membrane lipid composition in response to external stress factors such as changes in pH and ionic strength. S. aureus synthesizes and incorporates in its membrane staphyloxanthin, a carotenoid providing protection against oxidative damage and antimicrobial agents. Staphyloxanthin is known to modulate the physical properties of the bacterial membranes due to the rigid diaponeurosporenoic group it contains. In this work, preparative thin layer chromatography and liquid chromatography mass spectrometry were used to purify staphyloxanthin from S. aureus and characterize its structure, identifying C15, C17 and C19 as the main fatty acids in this carotenoid. Changes in the biophysical properties of models of S. aureus membranes containing phosphatidylglycerol, cardiolipin, and staphyloxanthin were evaluated. Infrared spectroscopy shows that staphyloxanthin reduces the liquid-crystalline to gel phase transition temperature in the evaluated model systems. Interestingly, these shifts are not accompanied by strong changes in trans/gauche isomerization, indicating that chain conformation in the liquid-crystalline phase is not altered by staphyloxanthin. In contrast, headgroup spacing, measured by Laurdan GP fluorescence spectroscopy, and lipid core dynamics, measured by DPH fluorescence anisotropy, show significant shifts in the presence of staphyloxanthin. The combined results show that staphyloxanthin reduces lipid core dynamics and headgroup spacing without altering acyl chain conformations, therefore decoupling these normally correlated effects. We propose that the rigid diaponeurosporenoic group in staphyloxanthin and its positioning in the membrane is likely responsible for the results observed.

Population Analysis of Daptomycin-non-Susceptible Methicillin-Resistant Staphylococcus aureus Reveals the Presence of Variants That Contribute to Daptomycin Resistance

In this study, population analysis (PA) of methicillin-resistant Staphylococcus aureus (MRSA), before and after long-duration daptomycin (DAP) treatment, was used to detect subpopulations with different susceptibilities to DAP and to verify the changes in the number of resistant cells. Furthermore, we aimed to characterize the bacteriology of the variants present in the non-susceptible cell subpopulation. A DAP non-susceptible (NS) MRSA phenotype (D2) that emerged from a DAP- susceptible MRSA phenotype (D1) during treatment of an open wound, was used for testing. We performed bacteriological and genetic analyses of cryptic DAP-NS MRSA variants detected by PA to study the variants present in the resistant cell subpopulation. PA results suggest that MRSA adapted to survival in the presence of DAP are selected leading to reduced susceptibility. Within the cell population growing in media containing 2.0 mg/L of DAP, three variants with different pigment production and colony size were detected. Variant 3 was an orange colony due to enhanced production of staphyloxanthin. Our results revealed that the DAP minimum inhibitory concentration (MIC) value increased two-fold (4 mg/L) in variant 3, in which pigment production was most enhanced, compared to the parental strain D2. In conclusion, our results indicate that long-duration DAP treatment can lead to the emergence and increased proportion of DAP-NS subpopulations. Furthermore, slow-growing variants that can be detected only under antimicrobial selective pressure are present among DAP-NS cells, suggesting that these variants may also contribute to the development of DAP resistance.

A bacterial pigment provides cross-species protection from H2O2- and neutrophil-mediated killing

Bacterial infections are often polymicrobial. Pseudomonas aeruginosa and Staphylococcus aureus cause chronic co-infections, which are more problematic than mono-species infections. Understanding the mechanisms of their interactions is crucial for treating co-infections. Staphyloxanthin (STX), a yellow pigment synthesized by the S. aureus crt operon, promotes S. aureus resistance to oxidative stress and neutrophil-mediated killing. We found that STX production by S. aureus, either as surface-grown macrocolonies or planktonic cultures, was elevated when exposed to the P. aeruginosa exoproduct, 2-heptyl-4-hydroxyquinoline N-oxide (HQNO). This was observed with both mucoid and non-mucoid P. aeruginosa strains. The induction phenotype was found in a majority of P. aeruginosa and S. aureus clinical isolates examined. When subjected to hydrogen peroxide or human neutrophils, P. aeruginosa survival was significantly higher when mixed with wild-type (WT) S. aureus, compared to P. aeruginosa alone or with an S. aureus crt mutant deficient in STX production. In a murine wound model, co-infection with WT S. aureus, but not the STX-deficient mutant, enhanced P. aeruginosa burden and disease compared to mono-infection. In conclusion, we identified a role for P. aeruginosa HQNO mediating polymicrobial interactions with S. aureus by inducing STX production, which consequently promotes resistance to the innate immune effectors H2O2 and neutrophils. These results further our understanding of how different bacterial species cooperatively cause co-infections.

Phloretin Inhibits Quorum Sensing and Biofilm Formation in Serratia marcescens

This study investigated the antivirulence capacity and mechanism of apple-skin-derived phloretin against Serratia marcescens NJ01, a vegetable spoilage bacterium. At 0.5 to 2 mg/mL doses, phloretin considerably inhibited the secretion of acyl homoserine lactones (AHLs), indicating that phloretin disrupted quorum sensing (QS) in S. marcescens NJ01. The dysfunction of QS resulted in reduced biofilms and the decreased production of protease, prodigiosin, extracellular polysaccharides (EPSs), and swimming and swarming motilities. Dysfunctional QS also weakened the activity of antioxidant enzymes and improved oxidative injury. The improved oxidative injury changed the composition of the membrane, improved membrane permeability, and eventually increased the susceptibility of biofilm cells to amikacin, netilmicin, and imipenem. The disrupted QS and enhanced oxidative stress also caused disorders of amino acid metabolism, energy metabolism, and nucleic acid metabolism, and ultimately attenuated the ability of S. marcescens NJ01 to induce spoilage. Our results indicated that phloretin can act as a potent drug to defend against spoilage by S. marcescens.

Developing 3-(2-Isocyano-6-methylbenzyl)-1H-indole Derivatives to Enhance the Susceptibility of Serratia marcescens by Occluding Quorum Sensing

Quorum sensing (QS) inhibition is recognized as a novel antimicrobial target for infections caused by drug-resistant pathogens and is an attractive strategy for antipathogenic agent development. We designed and synthesized three parts of 3-(2-isocyanobenzyl)-1H-indole derivatives and tested their activity as novel quorum sensing inhibitors (QSIs). 3-(2-Isocyanobenzyl)-1H-indole derivatives demonstrated promising QS, biofilms, and prodigiosin inhibitory activities against Serratia marcescens at subminimum inhibitory concentrations (sub-MICs). In particular, 3-(2-isocyano-6-methylbenzyl)-1H-indole (IMBI, 32) was identified as the best candidate based on several screening assays, including biofilm and prodigiosin inhibition. Further studies demonstrated that exposure to IMBI at 1.56 μg/mL to S. marcescens NJ01 significantly inhibited the formation of biofilms by 42%. The IMBI treatment on S. marcescens NJ01 notably enhanced the susceptibility of the formed biofilms, destroying the architecture of the biofilms by up to 40%, as evidenced by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). For interference of virulence factors in S. marcescens NJ01, IMBI at 3.12 μg/mL inhibited the activity of protease and extracellular polysaccharides (EPS) by 17% and 51%, respectively, which were higher than that of the positive control vanillic acid (VAN). Furthermore, IMBI downregulated the expression of QS- and biofilm-related genes fimA, bsmA, pigP, flhC, rssB, fimC, and rsmA by 1.02- to 2.74-fold. To confirm these findings, molecular docking was performed, which indicated that the binding of IMBI to SmaR, RhlI, RhlR, LasR, and CviR could antagonize the expression of QS-linked traits. In addition, molecular dynamic simulations (MD) and energy calculations indicated that the binding of receptors with IMBI was extremely stable. The biofilms of S. marcescens NJ01 were markedly reduced by 50% when IMBI (0.39 μg/mL) was combined with kanamycin (0.15 μg/mL). In conclusion, this study highlights the potency of IMBI in inhibiting the virulence factors of S. marcescens. IMBI has all the potential to be developed as an effective and efficient QS inhibitor and antibiofilm agent in order to restore or improve antimicrobial drug sensitivity.

Extracellular vesicles in bacterial and fungal diseases - Pathogenesis to diagnostic biomarkers

Intercellular communication among microbes plays an important role in disease exacerbation. Recent advances have described small vesicles, termed as "extracellular vesicles" (EVs), previously disregarded as "cellular dust" to be vital in the intracellular and intercellular communication in host-microbe interactions. These signals have been known to initiate host damage and transfer of a variety of cargo including proteins, lipid particles, DNA, mRNA, and miRNAs. Microbial EVs, referred to generally as "membrane vesicles" (MVs), play a key role in disease exacerbation suggesting their importance in pathogenicity. Host EVs help coordinate antimicrobial responses and prime the immune cells for pathogen attack. Hence EVs with their central role in microbe-host communication, may serve as important diagnostic biomarkers of microbial pathogenesis. In this review, we summarize current research regarding the roles of EVs as markers of microbial pathogenesis with specific focus on their interaction with host immune defence and their potential as diagnostic biomarkers in disease conditions.

Development and first-in-human testing of FLUME urinary catheter with protected tip and relocated drainage holes

Purpose

Evaluation of a catheter design which protects its tip with the retaining balloon when inflated, and has eyeholes at the base of the balloon to improve drainage.

Materials and methods

Preclinical tests included assessment of retaining balloon performance, and microbiological blockage. Clinical testing evaluated short-term use and safety in hospital (stage 1) or the patient's usual residence (stage 2).

Results

The retaining balloon supported static loads of 0.7kg, with reduced trauma when modelling forced evulsion. In vitro time to blockage with P. Mirabilis was significantly slower for FLUME compared with latex Foley catheters, but not the silicone Foley. Stage 1 testing (10 patients) confirmed balloon inflation, drainage, retention and removal, with no serious adverse events caused by catheterisation; one balloon failed to inflate, one patient could not be catheterised. Of five patients at stage 2, one had the catheter for 28 days without complication, one experienced spontaneous balloon deflation (14th day) and three needed early removal (blood clot, bypassing, difficulty connecting the drainage bag). Bacterial profiles of two FLUME catheters retained at least 2 weeks matched the Foley catheters. Acquired catheter colouration (two FLUME, one Foley) was not associated with biochemical change in the material.

Conclusion

FLUME catheter performed well in preclinical blockage and balloon tests. Tests in 15 patients confirmed basic function and additional training was not needed for staff familiar with Foley catheterisation. Clinical issues commonly seen with catheters included failed catheterisation, clot blockage and bypassing. In addition, an unintended balloon deflation and a failure of bag connection occurred.

Plain language summary

This article describes a new catheter design which aims to improve patient comfort and safety, and maximise bladder drainage, by protecting the bladder from the exposed catheter tip and by locating the drainage holes better. Various tests were done to check the catheter retaining balloon was safe and how well the catheter did when exposed to bacteria that could block it. The catheter was also used in people for the first time, to check it could be put in safely and functioned as intended. The results showed the FLUME catheter did well in the balloon and blockage tests. Tests in 15 patients confirmed basic function and showed placement was easy for staff familiar with conventional catheters. There were some clinical issues typical of urinary catheters and some possible improvements were identified.

Chromophore-Targeting Precision Antimicrobial Phototherapy

Phototherapy, encompassing the utilization of both natural and artificial light, has emerged as a dependable and non-invasive strategy for addressing a diverse range of illnesses, diseases, and infections. This therapeutic approach, primarily known for its efficacy in treating skin infections, such as herpes and acne lesions, involves the synergistic use of specific light wavelengths and photosensitizers, like methylene blue. Photodynamic therapy, as it is termed, relies on the generation of antimicrobial reactive oxygen species (ROS) through the interaction between light and externally applied photosensitizers. Recent research, however, has highlighted the intrinsic antimicrobial properties of light itself, marking a paradigm shift in focus from exogenous agents to the inherent photosensitivity of molecules found naturally within pathogens. Chemical analyses have identified specific organic molecular structures and systems, including protoporphyrins and conjugated C=C bonds, as pivotal components in molecular photosensitivity. Given the prevalence of these systems in organic life forms, there is an urgent need to investigate the potential impact of phototherapy on individual molecules expressed within pathogens and discern their contributions to the antimicrobial effects of light. This review delves into the recently unveiled key molecular targets of phototherapy, offering insights into their potential downstream implications and therapeutic applications. By shedding light on these fundamental molecular mechanisms, we aim to advance our understanding of phototherapy's broader therapeutic potential and contribute to the development of innovative treatments for a wide array of microbial infections and diseases.

Multicopy expression of sigma factor RpoH reduces prodigiosin biosynthesis in Serratia marcescens FS14

Regulation of prodigiosin biosynthesis is received wide attention due to the antimicrobial, immunosuppressive and anticancer activities of prodigiosin. Here, we constructed a transposon mutant library in S. marcescens FS14 to identify genes involved in the regulation of prodigiosin biosynthesis. 62 strains with apparently different colors were obtained. Identification of the transposon insertion sites revealed that they are classified into three groups: the coding region of cyaA and two component system eepS/R and the promoter region of rpoH. Since the effect of cyaA and eepS/R genes on prodigiosin was extensively investigated in Serratia marcescens, we chose the mutant of rpoH for further investigation. Further deletion mutation of rpoH gene showed no effect on prodigiosin production suggesting that the effect on prodigiosin production caused by transposon insertion is not due to the deletion of RpoH. We further demonstrated that multicopy expression of RpoH reduced prodigiosin biosynthesis indicating that transposon insertion caused RpoH enhanced expression. Previous results indicate that RpoS is the sigma factor for transcription of pig gene cluster in FS14, to test whether the enhanced expression of RpoH prevents prodigiosin by competing with RpoS, we found that multicopy expression of RpoS could alleviate the prodigiosin production inhibition by enhanced RpoH. We proposed that multicopy expressed RpoH competes with RpoS for core RNA polymerase (RNAP) resulting in decreased transcription of pig gene cluster and prodigiosin production reduction. We also demonstrated that RpoH is not directly involved in prodigiosin biosynthesis. Our results suggest that manipulating the transcription level of sigma factors may be applied to regulate the production of secondary metabolites.

Regulatory and pathogenic mechanisms in response to iron deficiency and excess in fungi

Iron is an essential element for all eukaryote organisms because of its redox properties, which are important for many biological processes such as DNA synthesis, mitochondrial respiration, oxygen transport, lipid, and carbon metabolism. For this reason, living organisms have developed different strategies and mechanisms to optimally regulate iron acquisition, transport, storage, and uptake in different environmental responses. Moreover, iron plays an essential role during microbial infections. Saccharomyces cerevisiae has been of key importance for decrypting iron homeostasis and regulation mechanisms in eukaryotes. Specifically, the transcription factors Aft1/Aft2 and Yap5 regulate the expression of genes to control iron metabolism in response to its deficiency or excess, adapting to the cell's iron requirements and its availability in the environment. We also review which iron-related virulence factors have the most common fungal human pathogens (Aspergillus fumigatus, Cryptococcus neoformans, and Candida albicans). These factors are essential for adaptation in different host niches during pathogenesis, including different fungal-specific iron-uptake mechanisms. While being necessary for virulence, they provide hope for developing novel antifungal treatments, which are currently scarce and usually toxic for patients. In this review, we provide a compilation of the current knowledge about the metabolic response to iron deficiency and excess in fungi.

The determination of the biological function of bacterial pink pigment and Fusarium chlamydosporum on alfalfa (Medicago sativa L.)

Bacterial pigment is one of the secondary metabolites produced by bacteria and has functions that are yet to be understood in relation to soil-borne pathogenic fungi and plants in mutualistic processes. The study evaluates the growth, photosynthetic, and physiological characteristics of alfalfa after interacting with different concentrations of Cp2 pink pigment and Fusarium chlamydosporum. The findings showed that Cp2 pink pigment has the ability to inhibit the growth of alfalfa, with the inhibition ratio gradually increasing with rising concentration. F. chlamydosporum inhibited the growth of alfalfa, which reduced the photosynthetic physiological response and elevated antioxidant enzymes, which are typically manifested by yellowing leaves and shortened roots. Under the combined effect of Cp2 pink pigment and F. chlamydosporum, increasing concentrations of Cp2 pink pigment intensified the symptoms in alfalfa and led to more pronounced growth and physiological response. This indicates that the Cp2 pink pigment is one of the potential virulence factors secreted by the Erwinia persicina strain Cp2, which plays an inhibitory role in the interactions between F. chlamydosporum and alfalfa, and also has the potential to be developed into a plant immunomodulator agent.

Melanin: a unifying theory of disease as exemplified by Parkinson's, Alzheimer's, and Lewy body dementia

Melanin, a ubiquitous dark pigment, plays important roles in the immune system, including scavenging reactive oxygen species formed in response to ultraviolet radiation absorption, absorbing metals, thermal regulation, drug uptake, innate immune system functions, redox, and energy transduction. Many tissue types, including brain, heart, arteries, ovaries, and others, contain melanin. Almost all cells contain precursors to melanin. A growing number of diseases in which there is a loss of melanin and/or neuromelanin are increasingly thought to have infectious etiologies, for example, Alzheimer's disease (AD), Parkinson's disease (PD), Lewy Body Dementia (LBD), and vitiligo. AD, PD, LBD, and vitiligo have been linked with herpesvirus, which enters melanosomes and causes apoptosis, and with gut dysbiosis and inflammation. Herpesvirus is also linked with gut dysbiosis and inflammation. We theorize that under normal healthy states, melanin retains some of the energy it absorbs from electromagnetic radiation, which is then used to fuel cells, and energy from ATP is used to compliment that energy supply. We further theorize that loss of melanin reduces the energy supply of cells, which in the case of AD, PD, and LBD results in an inability to sustain immune system defenses and remove the plaques associated with the disease, which appear to be part of the immune system's attempt to eradicate the pathogens seen in these neurodegenerative diseases. In addition, in an attempt to explain why removing these plaques does not result in improvements in cognition and mood and why cognitions and moods in these individuals have ebbs and flows, we postulate that it is not the plaques that cause the cognitive symptoms but, rather, inflammation in the brain resulting from the immune system's response to pathogens. Our theory that energy retained in melanin fuels cells in an inverse relationship with ATP is supported by studies showing alterations in ATP production in relationship to melanin levels in melanomas, vitiligo, and healthy cells. Therefore, alteration of melanin levels may be at the core of many diseases. We propose regulating melanin levels may offer new avenues for treatment development.

Review: The Chemistry, Toxicity and Antibacterial Activity of Curcumin and Its Analogues

Antimicrobial resistance is a global challenge that is already exacting a heavy price both in terms of human health and financial cost. Novel ways of approaching this crisis include the investigation of natural products. Curcumin is the major constituent in turmeric, and it is commonly used in the preparation of Asian cuisine. In addition, it possesses a wide range of pharmacological properties. This review provides a detailed account of curcumin and its analogues' antibacterial activity against both gram-positive and gram-negative isolates, including its potential mechanism(s) of action and the safety and toxicity in human and animal models. We also highlight the key challenges in terms of solubility/bioavailability associated with the use of curcumin and include research on how these challenges have been overcome.

Alleviating the virulence of Pseudomonas aeruginosa and Staphylococcus aureus by ascorbic acid nanoemulsion

The high incidence of persistent multidrug resistant bacterial infections is a worldwide public health burden. Alternative strategies are required to deal with such issue including the use of drugs with anti-virulence activity. The application of nanotechnology to develop advanced Nano-materials that target quorum sensing regulated virulence factors is an attractive approach. Synthesis of ascorbic acid Nano-emulsion (ASC-NEs) and assessment of its activity in vitro against the virulence factors and its protective ability against pathogenesis as well as the effect against expression of quorum sensing genes of Pseudomonas aeruginosa and Staphylococcus aureus isolates. Ascorbic acid Nano-emulsion was characterized by DLS Zetasizer Technique, Zeta potential; Transmission Electron Microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). The antibacterial activity of ASC-NEs was tested by the broth microdilution method and the activity of their sub-MIC against the expression of quorum sensing controlled virulence was investigated using phenotypic experiments and RT-PCR. The protective activity of ASC-NEs against P. aeruginosa as well as S. aureus pathogenesis was tested in vivo. Phenotypically, ASC-NEs had strong virulence inhibitory activity against the tested bacteria. The RT-PCR experiment showed that it exhibited significant QS inhibitory activity. The in vivo results showed that ASC-NEs protected against staphylococcal infection, however, it failed to protect mice against Pseudomonal infection. These results suggest the promising use of nanoformulations against virulence factors in multidrug resistant P. aeruginosa and S. aureus. However, further studies are required concerning the potential toxicity, clearance and phamacokinetics of the nanoformulations.

A Review of the Chemistry and Biological Activities of Natural Colorants, Dyes, and Pigments: Challenges, and Opportunities for Food, Cosmetics, and Pharmaceutical Application

Natural pigments are important sources for the screening of bioactive lead compounds. This article reviewed the chemistry and therapeutic potentials of over 570 colored molecules from plants, fungi, bacteria, insects, algae, and marine sources. Moreover, related biological activities, advanced extraction, and identification approaches were reviewed. A variety of biological activities, including cytotoxicity against cancer cells, antioxidant, anti-inflammatory, wound healing, anti-microbial, antiviral, and anti-protozoal activities, have been reported for different pigments. Considering their structural backbone, they were classified as naphthoquinones, carotenoids, flavonoids, xanthones, anthocyanins, benzotropolones, alkaloids, terpenoids, isoprenoids, and non-isoprenoids. Alkaloid pigments were mostly isolated from bacteria and marine sources, while flavonoids were mostly found in plants and mushrooms. Colored quinones and xanthones were mostly extracted from plants and fungi, while colored polyketides and terpenoids are often found in marine sources and fungi. Carotenoids are mostly distributed among bacteria, followed by fungi and plants. The pigments isolated from insects have different structures, but among them, carotenoids and quinone/xanthone are the most important. Considering good manufacturing practices, the current permitted natural colorants are: Carotenoids (canthaxanthin, β-carotene, β-apo-8'-carotenal, annatto, astaxanthin) and their sources, lycopene, anthocyanins, betanin, chlorophyllins, spirulina extract, carmine and cochineal extract, henna, riboflavin, pyrogallol, logwood extract, guaiazulene, turmeric, and soy leghemoglobin.

Antifungal therapy: Novel drug delivery strategies driven by new targets

In patients with compromised immunity, invasive fungal infections represent a significant cause of mortality. Given the limited availability and drawbacks of existing first-line antifungal drugs, there is a growing interest in exploring novel targets that could facilitate the development of new antifungal agents or enhance the effectiveness of conventional ones. While previous studies have extensively summarized new antifungal targets inherent in fungi for drug development purposes, the exploration of potential targets for novel antifungal drug delivery strategies has received less attention. In this review, we provide an overview of recent advancements in new antifungal drug delivery strategies that leverage novel targets, including those located in the physio-pathological barrier at the site of infection, the infection microenvironment, fungal-host interactions, and the fungal pathogen itself. The objective is to enhance therapeutic efficacy and mitigate toxic effects in fungal infections, particularly in challenging cases such as refractory, recurrent, and drug-resistant invasive fungal infections. We also discuss the current challenges and future prospects associated with target-driven antifungal drug delivery strategies, offering important insights into the clinical implementation of these innovative approaches.

Pseudomonas aeruginosa's greenish-blue pigment pyocyanin: its production and biological activities

A subject of great interest is the bioprospecting of microorganisms and their bioactive byproducts, such as pigments. Microbial pigments have various benefits, including being safe to use due to their natural makeup, having therapeutic effects, and being produced all year round, regardless of the weather or location. Pseudomonas aeruginosa produces phenazine pigments that are crucial for interactions between Pseudomonas species and other living things. Pyocyanin pigment, which is synthesized by 90-95% of P. aeruginosa, has potent antibacterial, antioxidant, and anticancer properties. Herein, we will concentrate on the production and extraction of pyocyanin pigment and its biological use in different areas of biotechnology, engineering, and biology.

Establishment of a CRISPR/Cas9-Mediated Efficient Knockout System of Trichoderma hamatum T21 and Pigment Synthesis PKS Gene Knockout

Trichoderma hamatum is a filamentous fungus that serves as a biological control agent for multiple phytopathogens and as an important resource promising for fungicides. However, the lack of adequate knockout technologies has hindered gene function and biocontrol mechanism research of this species. This study obtained a genome assembly of T. hamatum T21, with a 41.4 Mb genome sequence comprising 8170 genes. Based on genomic information, we established a CRISPR/Cas9 system with dual sgRNAs targets and dual screening markers. CRISPR/Cas9 plasmid and donor DNA recombinant plasmid were constructed for disruption of the Thpyr4 and Thpks1 genes. The result indicates the consistency between phenotypic characterization and molecular identification of the knockout strains. The knockout efficiencies of Thpyr4 and Thpks1 were 100% and 89.1%, respectively. Moreover, sequencing revealed fragment deletions between dual sgRNA target sites or GFP gene insertions presented in knockout strains. The situations were caused by different DNA repair mechanisms, nonhomologous end joining (NHEJ), and homologous recombination (HR). Overall, we have successfully constructed an efficient and convenient CRISPR/Cas9 system in T. hamatum for the first time, which has important scientific significance and application value for studies on functional genomics of Trichoderma and other filamentous fungi.

Metal manipulators and regulators in human pathogens: A comprehensive review on microbial redox copper metalloenzymes "multicopper oxidases and superoxide dismutases"

The chemistry of metal ions with human pathogens is essential for their survival, energy generation, redox signaling, and niche dominance. To regulate and manipulate the metal ions, various enzymes and metal chelators are present in pathogenic bacteria. Metalloenzymes incorporate transition metal such as iron, zinc, cobalt, and copper in their reaction centers to perform essential metabolic functions; however, iron and copper have gained more importance. Multicopper oxidases have the ability to perform redox reaction on phenolic substrates with the help of copper ions. They have been reported from Enterobacteriaceae, namely Salmonella enterica, Escherichia coli, and Yersinia enterocolitica, but their role in virulence is still poorly understood. Similarly, superoxide dismutases participate in reducing oxidative stress and allow the survival of pathogens. Their role in virulence and survival is well established in Salmonella typhimurium and Mycobacterium tuberculosis. Further, to ensure survival against stress, like metal starvation or metal toxicity, redox metalloenzymes and metal transportation systems of pathogens actively participate in metal homeostasis. Recently, the omics and protein structure biology studies have helped to predict new targets for regulation the colonization potential of the pathogenic strains. The current review is focused on the major roles of redox metalloenzymes, especially MCOs and SODs of human pathogenic bacteria.

Comparison of Atmospheric and Lithospheric Culturable Bacterial Communities from Two Dissimilar Active Volcanic Sites, Surtsey Island and Fimmvörðuháls Mountain in Iceland

Surface microbes are aerosolized into the atmosphere by wind and events such as dust storms and volcanic eruptions. Before they reach their deposition site, they experience stressful atmospheric conditions which preclude the successful dispersal of a large fraction of cells. In this study, our objectives were to assess and compare the atmospheric and lithospheric bacterial cultivable diversity of two geographically different Icelandic volcanic sites: the island Surtsey and the Fimmvörðuháls mountain, to predict the origin of the culturable microbes from these sites, and to select airborne candidates for further investigation. Using a combination of MALDI Biotyper analysis and partial 16S rRNA gene sequencing, a total of 1162 strains were identified, belonging to 72 species affiliated to 40 genera with potentially 26 new species. The most prevalent phyla identified were Proteobacteria and Actinobacteria. Statistical analysis showed significant differences between atmospheric and lithospheric microbial communities, with distinct communities in Surtsey’s air. By combining the air mass back trajectories and the analysis of the closest representative species of our isolates, we concluded that 85% of our isolates came from the surrounding environments and only 15% from long distances. The taxonomic proportions of the isolates were reflected by the site’s nature and location.

The two faces of pyocyanin - why and how to steer its production?

The ambiguous nature of pyocyanin was noted quite early after its discovery. This substance is a recognized Pseudomonas aeruginosa virulence factor that causes problems in cystic fibrosis, wound healing, and microbiologically induced corrosion. However, it can also be a potent chemical with potential use in a wide variety of technologies and applications, e.g. green energy production in microbial fuel cells, biocontrol in agriculture, therapy in medicine, or environmental protection. In this mini-review, we shortly describe the properties of pyocyanin, its role in the physiology of Pseudomonas and show the ever-growing interest in it. We also summarize the possible ways of modulating pyocyanin production. We underline different approaches of the researchers that aim either at lowering or increasing pyocyanin production by using different culturing methods, chemical additives, physical factors (e.g. electromagnetic field), or genetic engineering techniques. The review aims to present the ambiguous character of pyocyanin, underline its potential, and signalize the possible further research directions.

Dichotomous Role of Humic Substances in Modulating Transformation of Antibiotic Resistance Genes in Mineral Systems

Widespread antibiotic resistance genes (ARGs) have emerged as a focus of attention for public health. Transformation is essential for ARGs dissemination in soils and associated environments; however, the mechanisms of how soil components contribute to the transformation of ARGs remain elusive. Here we demonstrate that three representative mineral-humic acid (HA) composites exert contrasting influence on the transformation of plasmid-borne ARGs in Bacillus subtilis. Mineral surface-bound HA facilitated transformation in kaolinite and montmorillonite systems, while an inhibitory effect of HA was observed for goethite. The elevated transformation by HA-coated kaolinite was mainly attributed to the enhanced activity of competence-stimulating factor (CSF), while increased transformation by montmorillonite-HA composites was assigned to the weakened adsorption affinity of DNA and enhanced gene expression induced by flagella-driven cell motility. In goethite system, HA played an overriding role in suppressing transformation via alleviation of cell membrane damage. The results obtained offer insights into the divergent mechanisms of humic substances in modulating bacterial transformation by soil minerals. Our findings would help for a better understanding on the fate of ARGs in soil systems and provide potentials for the utilization of soil components, particularly organic matter, to mitigate the spread of ARGs in a range of settings.

Prevalence and Characterization of Serratia marcescens Isolated from Clinical Bovine Mastitis Cases in Ningxia Hui Autonomous Region of China

Purpose

This study aimed to investigate the prevalence and genetic characterization of Serratia marcescens isolates from clinical bovine mastitis in Ningxia Hui Autonomous Region of China.

Methods

S. marcescens was identified by the polymerase-chain reaction of 16S rRNA gene and sequencing. Antimicrobial susceptibility was tested by the disk diffusion method. Genes of resistance and virulence were determined by the PCR.

Results

Overall, S. marcescens were confirmed from 32 of 2897 (1.1%) mastitis milk samples. These isolates showed high resistance to cefazolin (30/32, 93.8%) and chloramphenicol (28/32, 87.5%). A 12.5% (4/32) of the isolates displayed multidrug resistance (MDR). The most prevalent resistant genes found in S. marcescens were TEM (32/32, 100%) and CTX-M (24/32, 75.0%; CTX-M-15, 14/32, 43.8%; CTX-M-14, 8/32, 25.0%; CTX-M-65, 2/32, 6.3%) for extended-spectrum beta-lactamase, cmlA (28/32, 87.5%) and floR (16/32, 50.0%) for chloramphenicol resistance, SIM-1 (2/32, 6.3%) for carbapenemases, and sdeB (28/32, 87.5%), sdeY (26/32, 81.3%), sdeR (26/32, 81.3%) and sdeD (20/32, 62.5%) for efflux pumps. Moreover, all isolates carried virulence genes flhD, entB, and kpn, and most of them contained mrkD (30/32, 93.8%), ycfM (26/32, 81.3%), bsmB (26/32, 81.3%), pigP (26/32, 81.3%), kfu (24/32, 75.0%) and shlB (24/32, 75.0%).

Conclusion

To our knowledge, this is the first report of genetic determinants for antimicrobial resistance and virulence in S. marcescens isolated from bovine mastitis cases in China. These findings are useful for developing strategies for prevention and treatment of bovine mastitis caused by S. marcescens in China.

Sensitivity of Janthinobacterium Lividum to Low Concentrations of Hydrogen Peroxide and the Effect of Mild Oxidative Stress on Pigment Yield

In the course of assessing the sensitivity of the Janthinobacterium lividum VKM B-3515 strain to low concentrations of hydrogen peroxide, it was found that at a content of 0.003% H2O2, the growth properties of the bacterium during submerged cultivation without pigmentation differed statistically insignificantly relative to the control variant at 16 hours of incubation and beyond. Whereas in the presence of peroxide at 12 hours the optical density was lower than in the control by 97%. When cultivating by the surface method, the respiration intensity did not significantly differ between the control and experimental variants. However, during the extraction of the pigment, it was found that in the presence of hydrogen peroxide, the optical density of the acetone extract significantly exceeds the control variant by 28%. It can be assumed that, at the same growth parameters of the culture, the biosynthesis of violacein is stimulated and the population can adapt to the peroxide content, and the peroxide concentration itself decreases due to the cost of catalytic reactions. Further studies of the sensitivity of J. lividum VKM B-3515 to various oxidizing agents will allow us to consider the effect of weak oxidative stress on the biosynthesis of violacein.

Production of Fungal Pigments: Molecular Processes and Their Applications

Due to the negative environmental and health effects of synthetic colorants, pigments of natural origins of plants and microbes constitute an abundant source for the food, cosmetic, textile, and pharmaceutical industries. The demands for natural alternatives, which involve natural colorants and natural biological processes for their production, have been growing rapidly in recent decades. Fungi contain some of the most prolific pigment producers, and they excel in bioavailability, yield, cost-effectiveness, and ease of large-scale cell culture as well as downstream processing. In contrast, pigments from plants are often limited by seasonal and geographic factors. Here, we delineate the taxonomy of pigmented fungi and fungal pigments, with a focus on the biosynthesis of four major categories of pigments: carotenoids, melanins, polyketides, and azaphilones. The molecular mechanisms and metabolic bases governing fungal pigment biosynthesis are discussed. Furthermore, we summarize the environmental factors that are known to impact the synthesis of different fungal pigments. Most of the environmental factors that enhance fungal pigment production are related to stresses. Finally, we highlight the challenges facing fungal pigment utilization and future trends of fungal pigment development. This integrated review will facilitate further exploitations of pigmented fungi and fungal pigments for broad applications.

Pyocyanin and 1-Hydroxyphenazine Promote Anaerobic Killing of Pseudomonas aeruginosa via Single-Electron Transfer with Ferrous Iron

Previously, it was reported that natural phenazines are able to support the anaerobic survival of Pseudomonas aeruginosa PA14 cells via electron shuttling, with electrodes poised as the terminal oxidants (Y. Wang, S. E. Kern, and D. K. Newman, J Bacteriol 192:365-369, 2010, https://doi.org/10.1128/JB.01188-09). The present study shows that both pyocyanin (PYO) and 1-hydroxyphenazine (1-OHPHZ) promoted the anaerobic killing of PA14 Δphz cells presumably via a single-electron transfer reaction with ferrous iron. However, phenazine-1-carboxylic acid (PCA) did not affect anaerobic survival in the presence of ferrous iron. Anaerobic cell death was alleviated by the addition of antioxidant compounds, which inhibit electron transfer via DNA damage. Neither superoxide dismutase (SOD) nor catalase was able to alleviate P. aeruginosa cell death, ruling out the possibility of reactive oxygen species (ROS)-induced killing. Further, the phenazine degradation profile and the redox state-associated color changes suggested that phenazine radical intermediates are likely generated by single-electron transfer. In this study, we showed that the phenazines 1-OHPHZ and PYO anaerobically killed the cell via single-electron transfer with ferrous iron and that the killing might have resulted from phenazine radicals. IMPORTANCE Pseudomonas aeruginosa is an opportunistic human pathogen which infects patients with burns, immunocompromised individuals, and in particular, the mucus that accumulates on the surface of the lung in cystic fibrosis (CF) patients. Phenazines as redox-active small molecules have been reported as important compounds for the control of cellular functions and virulence as well as anaerobic survival via electron shuttles. We show that both pyocyanin (PYO) and 1-hydroxyphenazine (1-OHPHZ) generate phenazine radical intermediates via presumably single-electron transfer reaction with ferrous iron, leading to the anaerobic killing of Pseudomonas cells. The recA mutant defect in the DNA repair system was more sensitive to anaerobic conditions. Our results collectively suggest that both phenazines anaerobically kill cells via DNA damage during electron transfer with iron.

Heterologous production and characterization of a pyomelanin of Antarctic Pseudomonas sp. ANT_H4: a metabolite protecting against UV and free radicals, interacting with iron from minerals and exhibiting priming properties toward plant hairy roots

BACKGROUND

Antarctica has one of the most extreme environments in the world. This region is inhabited by specifically adapted microorganisms that produce various unique secondary metabolites (e.g. pigments) enabling their survival under the harsh environmental conditions. It was already shown that these natural, biologically active molecules may find application in various fields of biotechnology.

RESULTS

In this study, a cold-active brown-pigment-producing Pseudomonas sp. ANT_H4 strain was characterized. In-depth genomic analysis combined with the application of a fosmid expression system revealed two different pathways of melanin-like compounds biosynthesis by the ANT_H4 strain. The chromatographic behavior and Fourier-transform infrared spectroscopic analyses allowed for the identification of the extracted melanin-like compound as a pyomelanin. Furthermore, optimization of the production and thorough functional analyses of the pyomelanin were performed to test its usability in biotechnology. It was confirmed that ANT_H4-derived pyomelanin increases the sun protection factor, enables scavenging of free radicals, and interacts with the iron from minerals. Moreover, it was shown for the first time that pyomelanin exhibits priming properties toward Calendula officinalis hairy roots in in vitro cultures.

CONCLUSIONS

Results of the study indicate the significant biotechnological potential of ANT_H4-derived pyomelanin and open opportunities for future applications. Taking into account protective features of analyzed pyomelanin it may be potentially used in medical biotechnology and cosmetology. Especially interesting was showing that pyomelanin exhibits priming properties toward hairy roots, which creates a perspective for its usage for the development of novel and sustainable agrotechnical solutions.

Nature's palette: An emerging frontier for coloring dairy products

Consumers all across the world are looking for the most delectable and appealing foods, while also demanding products that are safer, more nutritious, and healthier. Substitution of synthetic colorants with natural colorants has piqued consumer and market interest in recent years. Due to increasing demand, extensive research has been conducted to find natural and safe food additives, such as natural pigments, that may have health benefits. Natural colorants are made up of a variety of pigments, many of which have significant biological potential. Because of the promising health advantages, natural colorants are gaining immense interest in the dairy industry. This review goes over the use of various natural colorants in dairy products which can provide desirable color as well as positive health impacts. The purpose of this review is to provide an in-depth look into the field of food (natural or synthetic) colorants applied in dairy products as well as their potential health benefits, safety, general trends, and future prospects  in food science and technology. In this paper, we listed a plethora of applications of natural colorants in various milk-based products.

Geraniol inhibits biofilm formation of methicillin-resistant Staphylococcus aureus and increase the therapeutic effect of vancomycin in vivo

Methicillin-resistant Staphylococcus aureus (MRSA) is among the common drug resistant bacteria, which has gained worldwide attention due to its high drug resistance and infection rates. Biofilms produced by S. aureus are known to increase antibiotic resistance, making the treatment of S. aureus infections even more challenging. Hence, inhibition of biofilm formation has become an alternative strategy for controlling persistent infections. In this study, we evaluated the efficacy of geraniol as a treatment for MRSA biofilm infection. The results of crystal violet staining indicated that 256 μg/mL concentration of geraniol inhibited USA300 biofilm formation by 86.13% and removed mature biofilms by 49.87%. Geraniol exerted its anti-biofilm effect by influencing the major components of the MRSA biofilm structure. We found that geraniol inhibited the synthesis of major virulence factors, including staphyloxanthin and autolysins. The colony count revealed that geraniol inhibited staphyloxanthin and sensitized USA300 cells to hydrogen peroxide. Interestingly, geraniol not only reduced the release of extracellular nucleic acids (eDNA) but also inhibited cell autolysis. Real-time polymerase chain reaction data revealed the downregulation of genes involved in biofilm formation, which verified the results of the phenotypic analysis. Geraniol increased the effect of vancomycin in eliminating USA300 biofilms in a mouse infection model. Our findings revealed that geraniol effectively inhibits biofilm formation in vitro. Furthermore, in combination with vancomycin, geraniol can reduce the biofilm adhesion to the implant in mice. This suggests the potential of geraniol as an anti-MRSA biofilm drug and can provide a solution for the clinical treatment of biofilm infection.

Increased Innate Immune Susceptibility in Hyperpigmented Bacteriophage-Resistant Mutants of Pseudomonas aeruginosa

Bacteriophage (phage) therapy is an alternative to traditional antibiotic treatments that is particularly important for multidrug-resistant pathogens, such as Pseudomonas aeruginosa. Unfortunately, phage resistance commonly arises during treatment as bacteria evolve to survive phage predation. During in vitro phage treatment of a P. aeruginosa-type strain, we observed the emergence of phage-resistant mutants with brown pigmentation that was indicative of pyomelanin. As increased pyomelanin (due to hmgA gene mutation) was recently associated with enhanced resistance to hydrogen peroxide and persistence in experimental lung infection, we questioned if therapeutic phage applications could inadvertently select for hypervirulent populations. Pyomelanogenic phage-resistant mutants of P. aeruginosa PAO1 were selected for upon treatment with three distinct phages. Phage-resistant pyomelanogenic mutants did not possess increased survival of pyomelanogenic ΔhmgA in hydrogen peroxide. At the genomic level, large (~300 kb) deletions in the phage-resistant mutants resulted in the loss of ≥227 genes, many of which had roles in survival, virulence, and antibiotic resistance. Phage-resistant pyomelanogenic mutants were hypersusceptible to cationic peptides LL-37 and colistin and were more easily cleared in human whole blood, serum, and a murine infection model. Our findings suggest that hyperpigmented phage-resistant mutants that may arise during phage therapy are markedly less virulent than their predecessors due to large genomic deletions. Thus, their existence does not present a contraindication to using anti-pseudomonal phage therapy, especially considering that these mutants develop drug susceptibility to the familiar FDA-approved antibiotic, colistin.

Feed Insects as a Reservoir of Granadaene-Producing Lactococci

Insects are a component of the diet of different animal species and have been suggested as the major source of human dietary protein for the future. However, insects are also carriers of potentially pathogenic microbes that constitute a risk to food and feed safety. In this study, we reported the occurrence of a hemolytic orange pigmented producing phenotype of Lactococcus garvieae/petauri/formosensis in the fecal microbiota of golden lion tamarins (Leontopithecus rosalia) and feed larvae (Zophobas atratus). Feed insects were identified as a regular source of L. garvieae/petauri/formosensis based on a reanalysis of available 16S rRNA gene libraries. Pan-genome analysis suggested the existence of four clusters within the L. garvieae/petauri/formosensis group. The presence of cyl cluster indicated that some strains of the L. garvieae/petauri/formosensis group produced a pigment similar to granadaene, an orange cytotoxic lipid produced by group B streptococci, including Streptococcus agalactiae. Pigment production by L. garvieae/petauri/formosensis strains was dependent on the presence of the fermentable sugars, with no pigment being observed at pH <4.7. The addition of buffering compounds or arginine, which can be metabolized to ammonium, restored pigment formation. In addition, pigment formation might be related to the source of peptone. These data suggest that edible insects are a possible source of granadaene-producing lactococci, which can be considered a pathogenic risk with zoonotic potential.

Phenazines and toxoflavin act as interspecies modulators of resilience to diverse antibiotics

Bacterial opportunistic pathogens make diverse secondary metabolites both in the natural environment and when causing infections, yet how these molecules mediate microbial interactions and their consequences for antibiotic treatment are still poorly understood. Here, we explore the role of three redox-active secondary metabolites, pyocyanin, phenazine-1-carboxylic acid and toxoflavin, as interspecies modulators of antibiotic resilience. We find that these molecules dramatically change susceptibility levels of diverse bacteria to clinical antibiotics. Pyocyanin and phenazine-1-carboxylic acid are made by Pseudomonas aeruginosa, while toxoflavin is made by Burkholderia gladioli, organisms that infect cystic fibrosis and other immunocompromised patients. All molecules alter the susceptibility profile of pathogenic species within the "Burkholderia cepacia complex" to different antibiotics, either antagonizing or potentiating their effects, depending on the drug's class. Defense responses regulated by the redox-sensitive transcription factor SoxR potentiate the antagonistic effects these metabolites have against fluoroquinolones, and the presence of genes encoding SoxR and the efflux systems it regulates can be used to predict how these metabolites will affect antibiotic susceptibility of different bacteria. Finally, we demonstrate that inclusion of secondary metabolites in standard protocols used to assess antibiotic resistance can dramatically alter the results, motivating the development of new tests for more accurate clinical assessment.

Effect of (+) usnic Acid on Pigment Production in Bacteria

Antibiotic resistance is a universal problem in bacterial infections. Hence it gives high priority for new therapeutic methods to alternate conventional antibiotic treatment. Pigment production is one of the virulence characteristics of bacteria regulated by a quorum-sensing mechanism. Antiquorum sensing activities will not directly affect the viability of bacteria; however, they will reduce the pathogenicity of bacteria. Thereby it gives an adverse probability of the development of drug resistance. Aim of our study is to evaluate the activity of (+) usnic acid on pigment production in Pseudomonas aeruginosa MTCC 2453, Chromobacterium violaceum MTCC 2656 and Serratia marcescens MTCC 8708. (+) usnic acid eluted by column chromatography. Dimethyl sulphoxide (DMSO) was used as the solvent for (+) usnic acid. Antibacterial activity determined by Agar well diffusion and broth microdilution methods. Effect on pigment production was assessed by spectroscopy. (+) usnic acid showed accumulative inhibition as its concentration increases on pigment production by Pseudomonas aeruginosa MTCC 2453, Chromobacterium violaceum MTCC 2656 and Serratia marcescens MTCC 8708. The lowest concentrations of (+) usnic acid manifested 50% inhibition of pigment production was 122.67, 87.73 and 205.26 µg/ml respectively on above mentioned order in bacteria. The concentration of (+) usnic acid that showed pigment production inhibition did not hinder the growth of the bacteria, but it can reduce the virulence of the bacteria. This property can be used to resolve the drug resistance in bacteria. Further studies are required to check the action of (+) usnic acid on other virulence factors of the bacteria to prove the quorum quenching activity.

Therapeutic Potential of Green Synthesized Gold Nanoparticles Using Extract of Leptadenia hastata against Invasive Pulmonary Aspergillosis

Gold nanoparticles are widely used in the biomedical field for the treatment of several diseases, including cancer, inflammatory diseases, and immune system disorders, due to their distinctive physicochemical characteristics. In this study, we investigated the therapeutic potential of green synthesized gold nanoparticles using ethanolic leaf extract of Leptadenia hastata (LH-AuNPs) against invasive pulmonary aspergillosis (IPA) in mice. UV/visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and zeta potential were used to characterize the biofabricated LH-AuNPs. Antifungal activity of LH-AuNPs was determined by MTT assay, (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide), time-kill assay, and radial growth inhibition. TEM and SEM were used to examine the mode of the antifungal action of LH-AuNPs. The in vivo activity of LH-AuNPs against IPA was studied using a well-established IPA mouse model. LH-AuNPs excreted antifungal activity against Aspergillus fumigatus with MIC 64 µg/mL and inhibited the radial growth of A. fumigatus by 30% compared to the control. LH-AuNPs caused distortion and collapse of fungal hyphae and deterioration of cell walls. Interestingly, LH-AuNPs did not display any cytotoxicity on cultured primary bone marrow stem cells (BMSCs) or A549 human lung cell line in vitro at MIC concentration. IPA mice treated with LH-AuNPs displayed significant lung tissue repair without any in vivo cytotoxicity. LH-AuNPs administration showed significant suppression of fungal burden and gliotoxin production in the lung. In addition, LH-AuNPs inhibited IPA-induced pro-inflammatory cytokines production, including interleukin-1 (IL-1), interleukin-17 (IL-17), and tumor necrosis factor-alpha (TNF-α), and reduced oxidative stress in lung. In conclusion, our data provide LH-AuNPs as a novel nanoparticle therapy for IPA.

Photoinactivation of catalase sensitizes wide-ranging bacteria to ROS-producing agents and immune cells

Bacteria have evolved to cope with the detrimental effects of ROS using their essential molecular components. Catalase, a heme-containing tetramer protein expressed universally in most aerobic bacteria, plays an indispensable role in scavenging excess hydrogen peroxide (H₂O₂). Here, through use of wild-type and catalase-deficient mutants, we identified catalase as an endogenous therapeutic target of 400–420 nm blue light. Catalase residing inside bacteria could be effectively inactivated by blue light, subsequently rendering the pathogens extremely vulnerable to H₂O₂ and H₂O₂-producing agents. As a result, photoinactivation of catalase and H₂O₂ synergistically eliminated a wide range of catalase-positive planktonic bacteria and P. aeruginosa inside biofilms. In addition, photoinactivation of catalase was shown to facilitate macrophage defense against intracellular pathogens. The antimicrobial efficacy of catalase photoinactivation was validated using a Pseudomonas aeruginosa–induced mouse abrasion model. Taken together, our findings offer a catalase-targeting phototherapy approach against multidrug-resistant bacterial infections.

The bZip Transcription Factor VdMRTF1 is a Negative Regulator of Melanin Biosynthesis and Virulence in Verticillium dahliae

The ascomycete fungus Verticillium dahliae infects over 400 plant species and causes serious losses of economically important crops, such as cotton and tomato, and also of woody plants, such as smoke tree, maple, and olive. Melanized long-term survival structures known as microsclerotia play crucial roles in the disease cycle of V. dahliae, enabling this soilborne fungus to survive for years in the soil in the absence of a host. Previously, we identified VdMRTF1 (microsclerotia-related transcription factor) encoding a bZip transcription factor which is downregulated during microsclerotial development in V. dahliae. In the present study, we showed that VdMRTF1 negatively controls melanin production and virulence by genetic, biological, and transcriptomic analyses. The mutant strain lacking VdMRTF1 (ΔVdMRTF1) exhibited increased melanin biosynthesis and the defect also promoted microsclerotial development and sensitivity to Ca²⁺. In comparison with the wild-type strain, the ΔVdMRTF1 strain showed a significant enhancement in virulence and displayed an increased capacity to eliminate reactive oxygen species in planta. Furthermore, analyses of transcriptomic profiles between the ΔVdMRTF1 and wild-type strains indicated that VdMRTF1 regulates the differential expression of genes associated with melanin biosynthesis, tyrosine metabolism, hydrogen peroxide catabolic processes, and oxidoreductase activity in V. dahliae. Taken together, these data show that VdMRTF1 is a negative transcriptional regulator of melanin biosynthesis, microsclerotia formation, and virulence in V. dahliae.

IMPORTANCE Verticillium wilt is difficult to manage because the pathogen colonizes the plant xylem tissue and produces melanized microsclerotia which survive for more than 10 years in soil without a host. The molecular mechanisms underlying microsclerotia formation are of great importance to control the disease. Here, we provide evidence that a bZip transcription factor, VdMRTF1, plays important roles in melanin biosynthesis, microsclerotial development, resistance to elevated Ca²⁺ levels, and fungal virulence of V. dahliae. The findings extend and deepen our understanding of the complexities of melanin biosynthesis, microsclerotia formation, and virulence that are regulated by bZip transcription factors in V. dahliae.