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Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microorganisms produce siderophores, which are low-molecular-weight iron chelators when iron availability is limited. The present analyzed the role of LNPF1 as multifarious PGPR for improving growth parameters and nutrient content in peanut and soil nutrients. Such multifarious PGPR strains can be used as effective bioinoculants for peanut farming. In this work, rhizosphere bacteria from Zea mays and Arachis hypogaea plants in the Salem area of Tamil Nadu, India, were isolated and tested for biochemical attributes and characteristics that stimulate plant growth, such as the production of hydrogen cyanide, ammonia (6 µg/mL), indole acetic acid (76.35 µg/mL), and solubilizing phosphate (520 µg/mL). The 16S rRNA gene sequences identified the isolate LNPF1 as Pseudomonas fluorescens with a similarity percentage of 99% with Pseudomonas sp. Isolate LNPF1 was evaluated for the production of siderophore. Siderophore-rich supernatant using a Sep Pack C18 column and Amberlite-400 Resin Column (λmax 264) produced 298 mg/L and 50 mg/L of siderophore, respectively. The characterization of purified siderophore by TLC, HPLC, FTIR, and 2D-NMR analysis identified the compound as desferrioxamine, a hydroxamate siderophore. A pot culture experiment determined the potential of LNPF1 to improve iron and oil content and photosynthetic pigments in Arachis hypogaea L. and improve soil nutrient content. Inoculation of A. hypogea seeds with LNPF1 improved plant growth parameters such as leaf length (60%), shoot length (22%), root length (54.68%), fresh weight (47.28%), dry weight (37%), and number of nuts (66.66) compared to the control (untreated seeds). This inoculation also improved leaf iron content (43.42), short iron content (38.38%), seed iron (46.72%), seed oil (31.68%), carotenoid (64.40%), and total chlorophyll content (98.%) compared to control (untreated seeds). Bacterized seeds showed a substantial increase in nodulation (61.65%) and weight of individual nodules (95.97) vis-à-vis control. The results of the present study indicated that P. fluorescens might be utilized as a potential bioinoculant to improve growth, iron content, oil content, number of nuts and nodules of Arachishypogaea L., and enrich soil nutrients. [ABSTRACT FROM AUTHOR]

In the growing landscape of interest in natural surfactants, selecting the appropriate one for specific applications remains challenging. The extensive, yet often unsystematized, knowledge of microbial surfactants, predominantly represented by rhamnolipids (RLs), typically does not translate beyond the conditions presented in scientific publications. This limitation stems from the numerous variables and their interdependencies that characterize microbial surfactant production. We hypothesized that a computational recipe for biosynthesizing RLs with targeted applicational properties could be developed from existing literature and experimental data. We amassed literature data on RL biosynthesis and micellar solubilization and augmented it with our experimental results on the solubilization of triglycerides (TGs), a topic underrepresented in current literature. Utilizing this data, we constructed mathematical models that can predict RL characteristics and solubilization efficiency, represented as logPRL = f(carbon and nitrogen source, parameters of biosynthesis) and logMSR = f(solubilizate, rhamnolipid (e.g. logPRL), parameters of solubilization), respectively. The models, characterized by robust R2 values of respectively 0.581–0.997 and 0.804, enabled the ranking of descriptors based on their significance and impact—positive or negative—on the predicted values. These models have been translated into ready-to-use calculators, tools designed to streamline the selection process for identifying a biosurfactant optimally suited for intended applications. [ABSTRACT FROM AUTHOR]

Home and personal care industry is currently witnessing a growing demand for sustainable and eco-friendly alternatives to synthetic surfactants. This increase is fueled by concerns over the delayed degradation and environmental impact of the latter. To this, biosurfactants possess important properties such as biodegradability, low toxicity, and renewable sourcing. These qualities position them as compelling replacements of traditional synthetic surfactants. Their diverse attributes including emulsification, antimicrobial efficacy, surface tension reduction, and foaming capability, make them well-suited choices for home and personal care products. Biosurfactants can be produced through several inexpensive and renewable sources which contributes to their commercialization potential. This article discusses various microbial derived biosurfactants including rhamnolipids, sophorolipids, mannosyl-erythritol lipids, trehalolipids and lipopeptides, unraveling and comparing their distinctive roles and advantages in the home and personal care industry. It also focuses on the recent patent innovations in the production of biosurfactants which have aimed at improving their economic viability and performance attributes. Finally, the article sheds light on the challenges and future trajectories for better integration of these sustainable biosurfactants into mainstream consumer products. [ABSTRACT FROM AUTHOR]

Background: Anti-virulence therapy is a promising strategy to treat multi-drug resistant (MDR) pathogens. Pseudomonas aeruginosa is a potent opportunistic pathogen because of an array of virulence factors that are regulated by quorum sensing systems. Methods: The virulence features of four multi-drug resistant P. aeruginosa strains were investigated upon exposure to the sub-lethal dose of gamma rays (1 kGy), and sub-inhibitory concentrations of bioactive metabolites recovered from local halophilic strains in comparison to control. Then, the gene expression of AHL-mediated quorum sensing systems (las/rhl) was quantitatively determined in treated and untreated groups by real-time PCR. Results: The bioactive metabolites recovered from halophilic strains previously isolated from saline ecosystems were identified as Halomonas cupida (Halo-Rt1), H. elongate (Halo-Rt2), Vigibacillus natechei (Halo-Rt3), Sediminibacillus terrae (Halo-Rt4) and H. almeriensis (Halo-Rt5). Results revealed that both gamma irradiation and bioactive metabolites significantly reduced the virulence factors of the tested MDR strains. The bioactive metabolites showed a maximum efficiency for inhibiting biofilm formation and rhamnolipids production whereas the gamma irradiation succeeded in decreasing other virulence factors to lower levels in comparison to control. Quantitative-PCR results showed that AHL-mediated quorum sensing systems (las/rhl) in P. aeruginosa strains were downregulated either by halo-bacterial metabolites or gamma irradiation in all treatments except the upregulation of both lasI internal gene and rhlR intact gene in P. aeruginosa NCR-RT3 and both rhlI internal gene and rhlR intact gene in P. aeruginosa U3 by nearly two folds or more upon exposure to gamma irradiation. The most potent result was observed in the expression of lasI internal gene that was downregulated by more than ninety folds in P. aeruginosa NCR-RT2 after treatment with metabolites of S. terrae (Halo-Rt4). Analyzing metabolites recovered from H. cupida (Halo-Rt1) and H. elongate (Halo-Rt2) using LC–ESI–MS/MS revealed many chemical compounds that have quorum quenching properties including glabrol, 5,8-dimethoxyquinoline-2-carbaldehyde, linoleoyl ethanolamide, agelasine, penigequinolones derivatives, berberine, tetracosanoic acid, and liquidambaric lactone in the former halophile and phloretin, lycoctonine, fucoxanthin, and crassicauline A in the latter one. Conclusion: QS inhibitors can significantly reduce the pathogenicity of MDR P. aeruginosa strains; and thus can be an effective and successful strategy for treating antibiotic resistant traits. [ABSTRACT FROM AUTHOR]

Polymer materials are typical insulators that are easily charged by contact electrification. Static charge generated by contact electrification on their surfaces can lead to lots of undesirable consequences, including a reduction in efficiency of manufacturing processes, damage to equipment, and even explosions. Thus, it is important to develop effective strategies to prevent the generation of static charge when surfaces of polymer materials come into contact. Here, we coated polymer materials with rhamnolipids (RLs) to create non‐charging surfaces. This innovative technique, based on glycosylated coatings using RLs, offers a universal solution that can be easily applied to a wide range of polymeric materials conferring resistance to surface charging via contact electrification. The amount of static charges generated was found to reduce dramatically in both low (~15%) and high (~60%) humidity situations. The reduction of charge is due to either or both of the following two mechanisms: by increasing surface conductivity driven by the hydrophilic groups of the RLs molecules, and or by their radical‐scavenging properties. Predictably, this new effective strategy is ideal for producing antistatic dipping and spray solution for various practical applications. [ABSTRACT FROM AUTHOR]

The present work investigates how rhamnolipid biosurfactants perform when removing the pesticides atrazine and 2,4 D from an artificially contaminated tropical soil. The rhamnolipid was produced by Pseudomonas aeruginosa, using molasses 7% m/v as a carbon source. The red‒yellow latosol, a tropical soil, went through a physical-chemical characterization and then was artificially contaminated with the herbicides. The value of 19.82 mL/g indicated high affinity to 2,4 D by the latosol, contrary to atrazine, having only a = 0.83 mL/g. The desorption tests in contaminated soil indicated that the presence of biosurfactants enhances pesticide removal, and was influenced by the pH and biosurfactant concentrations. Both pesticides attained greater values of desorption at a higher biosurfactant concentration of 5 CMC (900 mg/L), but at different pHs. From atrazine, a higher value of desorption, 25.66 mg/kg, was attained at a pH of 7.0. From 2,4 D, however, a desorption of 13.17 mg/kg was attained at a pH of 9.0. The Gunary model was shown to be the best-fitting model for both pesticides when analyzing experimental data, indicating a multilayer desorption process. The results indicate that rhamnolipids are a promising alternative in Surfactant-enhanced remediation (SER), contributing to the recovery of pesticide-contaminated soils. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is an important human opportunistic pathogen responsible for a wide range of infections. The complement system is the main early host defense mechanism to control these infections. P. aeruginosa counteracts complement attack by binding Factor H (FH), a complement regulator that inactivates C3b, preventing the formation of the C3-convertase and complement amplification on the bacterial surface. Factor H-related proteins (FHRs) are a group of plasma proteins evolutionarily related to FH that have been postulated to interfere in this bacterial mechanism of resisting complement. Here, we show that FHR-1 binds to P. aeruginosa via the outer membrane protein OprG in a lipopolysaccharide (LPS) O antigen-dependent manner. Binding assays with purified components or with FHR-1-deficient serum supplemented with FHR-1 show that FHR-1 competes with FH for binding to P. aeruginosa. Blockage of FH binding to C3b deposited on the bacteria reduces FH-mediated cofactor activity of C3b degradation, increasing the opsonization of the bacteria and the formation of the potent chemoattractant C5a. Overall, our findings indicate that FHR-1 is a host factor that promotes complement activation, facilitating clearance of P. aeruginosa by opsonophagocytosis. [ABSTRACT FROM AUTHOR]

Previously, we pointed out in P. aeruginosa PAO1 biofilm cells the accumulation of a hypothetical protein named PA3731 and showed that the deletion of the corresponding gene impacted its biofilm formation capacity. PA3731 belongs to a cluster of 4 genes (pa3732 to pa3729) that we named bac for "Biofilm Associated Cluster." The present study focuses on the PA14_16140 protein, i.e., the PA3732 (BacA) homolog in the PA14 strain. The role of BacA in rhamnolipid secretion, biofilm formation and virulence, was confirmed by phenotypic experiments with a bacA mutant. Additional investigations allow to advance that the bac system involves in fact 6 genes organized in operon, i.e., bacA to bacF. At a molecular level, quantitative proteomic studies revealed an accumulation of the BAC cognate partners by the bacA sessile mutant, suggesting a negative control of BacA toward the bac operon. Finally, a first crystallographic structure of BacA was obtained revealing a structure homologous to chaperones or/and regulatory proteins. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The chemical compositions, in vitro and in silico anti-dengue activity of the essential oils of the rhizomes of Curcuma longa Linn., C. aeruginosa Roxb., and C. xanthorrhiza Roxb. had been investigated. The C. longa oil was mainly composed of ar-turmerone (54.0%) and curlone (17.7%), while the C. aeruginosa oil was rich in curzerenone (23.4%), 1,8-cineole (21.2%), and camphor (7.1%). Xanthorrhizol (21.6%), β-curcumene (19.5%), ar-curcumene (14.2%), and camphor (9.2%) were the major compounds in the C. xanthorrhiza oil. Among the oils, the C. longa oil was found to be the most active NSB-NS3 protease inhibitor (IC50 1.98 μg/mL). PLS biplot disclosed that the essential oils were classified into three separated clusters based on their characteristic chemical compositions, with C. longa positioned closest to the in vitro anti-dengue activity. Four compounds from the C. longa oil have both hydrogen and hydrophobic bonds that could be responsible for the DENV-2 NS2B-NS3 inhibitory effect. [ABSTRACT FROM AUTHOR]

Summary: High internal phase emulsions (HIPEs) are potential carriers of fat‐soluble nutrients due to their high loading capacity. In this study, egg white protein particles (EWPP) and rhamnolipid (Rha) were used to co‐emulsify oil/water HIPEs to carry curcumin (Cur). The results showed that the Cur loading efficiency, microstructure, protein composition, molecular distribution of protein hydrolysates, protein interfacial adsorption rate and Cur bioavailability were measured. The results showed that, incorporation with Rha was unhelpful for improving loading efficiency of Cur, which decreased from 80.8% to 73.7% at pH 3.8 after incorporation with Rha, due to the decreased viscosity and destroyed continuous interface membrane, while beneficial for restricting coalescence of oil droplets. As studied, Rha could effectively reduce the droplet size to slow down the speed of coalescence and form EWPP–Rha complex to inhibit proteolysis. Finally, Cur bioavailability in EWPP–Rha co‐emulsified HIPE was the highest (40.3%), indicating the synergistic effect of EWPP and Rha promoting the effective adsorption of Cur, related to the increased coalescence stability during digestion and participation of Rha in the micellisation reaction. In comparison, fibrous (pH 3.8) and granular (pH 7.0) EWPP stabilised HIPEs, showed no obvious difference in Cur bioavailability, due to the balance between the interfacial adsorption ability and the digestion resistance of EWPP with various morphologies. This study has important significance for the construction of lipid soluble nutrient 'carriers' with high load and high bioavailability. [ABSTRACT FROM AUTHOR]

The emergence of drug-resistant microorganisms presents a substantial global public health threat. The increase in pathogens resistant to commonly prescribed antibiotics underscores the urgent requirement to explore alternative treatment strategies. This study adopts a novel approach by harnessing natural resources, specifically essential oils (EO), to combat bacterial pathogenicity. The primary aim of this research was to analyze the chemical composition of the aerial part of the Matricaria aurea (M. aureas) EO and evaluate its potential for inhibiting quorum sensing (QS) and disrupting biofilm formation in Pseudomonas aeruginosa (P. aeruginosa). The gas chromatography-mass spectrometry (GCMS) analysis unveiled that α-bisabolol oxide A constituted the predominant portion, comprising 64.8% of the total, with β-bisabolene at 6.3% and α-farnesene at 4.8% following closely behind. The antibiofilm efficacy was observed at concentrations of 0.3, 0.15, and 0.08 mg/mL, demonstrating negligible effects on cell viability. Furthermore, the EO from M. aurea effectively inhibited the formation of P. aeruginosa biofilms by diminishing aggregation, hydrophobicity, and swarming motility. Significantly, the EO treatment resulted in a conspicuous decrease in the production of pyocyanin, rhamnolipid, and extracellular polymeric substances (EPS), along with a reduction in the enzymatic activity of protease and chitinase. The EO effectively hindered QS by disrupting QS mechanisms, resulting in a marked decline in the secretion of N-Acyl homoserine lactone (AHL) molecules and the expression of phazA1 and aprA genes. This investigation offers compelling evidence supporting the potential of M. aurea EO as a promising therapeutic candidate for addressing infectious diseases induced by biofilm formation. [ABSTRACT FROM AUTHOR]

The establishment of sustainable processes for the production of commodity chemicals is one of today's central challenges for biotechnological industries. The chemo-autotrophic fixation of CO2 and the subsequent production of acetate by acetogenic bacteria via anaerobic gas fermentation represents a promising platform for the ecologically sustainable production of high-value biocommodities via sequential fermentation processes. In this study, the applicability of acetate-containing cell-free spent medium of the gas-fermenting acetogenic bacterium A. woodii WP1 as the feeder strain for growth and the recombinant production of P. aeruginosa PAO1 mono-rhamnolipids in the well-established nonpathogenic producer strain P. putida KT2440 were investigated. Additionally, the potential possibility of a simplified production process without the necessary separation of feeder strain cells was elucidated via the cultivation of P. putida in cell-containing A. woodii culture broth. For these cultures, the content of both strains was investigated by examining the relative quantification of strain-exclusive genes via qPCR. The recombinant production of mono-rhamnolipids was successfully achieved with maximum titers of approximately 360–400 mg/L for both cell-free and cell-containing A. woodii spent medium. The reported processes therefore represent a successful proof of principle for gas fermentation-derived acetate as a potential sustainable carbon source for future recombinant rhamnolipid production processes by P. putida KT2440. [ABSTRACT FROM AUTHOR]

Ergocalciferol, despite its high beneficial potential in foods and pharmaceuticals, faces challenges in utilization due to its hydrophobic and sensitive properties. In this study, we developed ergocalciferol-loaded zein nanoparticles coated with modified lecithin (ML) or rhamnolipids (RL) using the anti-solvent precipitation method. Both ML- and RL-stabilized zein nanoparticles exhibited narrow particle size distribution and high encapsulation efficiency of ergocalciferol, achieving 94.54 ± 2.28% and 94.24 ± 2.35%, respectively. The ML-stabilized nanoparticles demonstrated good stability under thermal treatments (30–90 °C) and pH variations (pH 3–8). In comparison, the nanoparticles stabilized by rhamnolipid (RL) remained stable under thermal conditions but became unstable when the pH dropped below 6. Additionally, both ML- and RL-stabilized nanoparticles demonstrated an increase in particle size after the addition of salt. Furthermore, all samples displayed high bioaccessibility of ergocalciferol after in vitro digestion and excellent physicochemical stability during 30 days of storage. Therefore, the ML- and RL-stabilized zein nanoparticles present promising prospects for effectively transporting functional ingredients such as ergocalciferol. [ABSTRACT FROM AUTHOR]

Biopurification systems designed for pesticide treatment are a source of diverse bacteria with environmental and biotechnological applications, including Pseudomonas marginalis C9, which has been reported as a biosurfactant-producing bacterium. The optimization of biosurfactant produced from P. marginalis C9 to enhance the solubility of a hydrophobic pesticide of environmental interest was investigated. The response surface methodology (RSM) was used to optimize the combined effect of the initial pH (5–9), agitation (100–300 rpm), and temperature (24–32 °C) on biosurfactant production. A DASbox® automated mini-bioreactor system was used to evaluate the critical factors in biosurfactant production using a full factorial design (FFD). The results showed that the optimal culture conditions using RSM were a pH of 8.5, a temperature of 25 °C, and agitation at 200 rpm. The extraction yield of the biosurfactant was 7.40 g L−1, the surface tension was reduced to 27.45 mN m−1, and the critical micelle concentration (CMC) was 48.9 mg L−1. The FFD analysis indicated that a high agitation rate (300 rpm) strongly influenced the biosurfactant activity, regardless of the inlet oxygen supply (0.5–1.5 vvm). The rhamnolipid increased the water solubility of chlorpyrifos by 11.2- and 21.7-fold at the CMC and twice the CMC, respectively.

Bacterial infections represent a key public health issue due to the occurrence of multidrug-resistant bacteria. Recently, the amount of data supporting the dynamic control of epigenetic pathways by environmental cues has triggered research efforts toward the clarification of their role in microbial infections. Among protein post-translational modifications, reversible acetylation is the most implicated in the feedback to environmental stimuli and in cellular homeostasis. Accordingly, the latest studies identified the histone deacetylase 6 (HDAC6) enzyme as a crucial player in the complex molecular machinery underlying bacterial clearance or killing. A very important milestone for the elucidation of the consequence of HDAC6 activity in bacterial infections is herein described, unveiling for the first time the role of a potent HDAC6 inhibitor in interfering with biofilm formation and modulating virulence factors of P. aeruginosa. We demonstrated that compound F2F-2020202 affected the production of some important virulence factors in P. aeruginosa, namely pyocyanin and rhamnolipids, clearly impairing its ability to form biofilm. Furthermore, evidence of possible QS involvement is supported by differential regulation of specific genes, namely RhlI, phAz1, and qsrO. The data herein obtained also complement and in part explain our previous results with selective HDAC6 inhibitors able to reduce inflammation and bacterial load in chronic infection models recapitulating the cystic fibrosis (CF) phenotype. This study fosters future in-depth investigation to allow the complete elucidation of the molecular mechanisms underlying HDAC6's role in bacterial infections. [ABSTRACT FROM AUTHOR]

Currently, there is limited understanding of the structures and variabilities of bacterial communities in oil-contaminated soil within shale gas development. The Changning shale gas well site in Sichuan province was focused, and high-throughput sequencing was used to investigate the structures of bacterial communities and functions of bacteria in soil with different degrees of oil pollution. Furthermore, the influences of the environmental factors including pH, moisture content, organic matter, total nitrogen, total phosphorus, oil, and the biological toxicity of the soil on the structures of bacterial communities were analyzed. The results revealed that Proteobacteria and Firmicutes predominated in the oil-contaminated soil. α-Proteobacteria and γ‐Proteobacteria were the main classes under the Proteobacteria phylum. Bacilli was the main class in the Firmicutes phylum. Notably, more bacteria were only found in CN-5 which was the soil near the storage pond for abandoned drilling mud, including Marinobacter, Balneola, Novispirillum, Castellaniella, and Alishewanella. These bacteria exhibited resilience to higher toxicity and demonstrated proficiency in oil degradation. The functions including carbohydrate transport and metabolism, energy metabolism, replication, recombination and repair replication, signal transduction mechanisms, and amino acid transport and metabolism responded differently to varying concentrations of oil. The disparities in bacterial genus composition across samples stemmed from a complex play of pH, moisture content, organic matter, total nitrogen, total phosphorus, oil concentration, and biological toxicity. Notably, bacterial richness correlated positively with moisture content, while bacterial diversity showed a significant positive correlation with pH. Acidobacteria exhibited a significant positive correlation with moisture content. Litorivivens and Luteimonas displayed a significant negative correlation with pH, while Rhizobium exhibited a significant negative correlation with moisture content. Pseudomonas, Proteiniphilum, and Halomonas exhibited positive correlations not only with organic matter but also with oil concentration. Total nitrogen exhibited a significant positive correlation with Taonella and Sideroxydans. On the other hand, total phosphorus showed a significant negative correlation with Sphingomonas. Furthermore, Sphingomonas, Gp6, and Ramlibacter displayed significant negative correlations with biological toxicity. The differential functions exhibited no significant correlation with environmental factors but displayed a significant positive correlation with the Proteobacteria phylum. Aridibacter demonstrated a significant positive correlation with cell motility and cellular processes and signaling. Conversely, Pseudomonas, Proteiniphilum, and Halomonas were negatively correlated with differential functions, particularly in amino acid metabolism, carbohydrate metabolism, and membrane transport. Compared with previous research, more factors were considered in this research when studying structural changes in bacterial communities, such as physicochemical properties and biological toxicity of soil. In addition, the correlations of differential functions of communities with environmental factors, bacterial phyla, and genera were investigated. [ABSTRACT FROM AUTHOR]

This study aims to isolate microbial strains for producing mono-rhamnolipids with high proportion. Oily sludge is rich in petroleum and contains diverse biosurfactant-producing strains. A biosurfactant-producing strain LP20 was isolated from oily sludge, identified as Pseudomonas aeruginosa based on phylogenetic analysis of 16S rRNA. High-performance liquid chromatography-mass spectrometry results indicated that biosurfactants produced from LP20 were rhamnolipids, mainly containing Rha-C8-C10, Rha-C10-C10, Rha-Rha-C8-C10, Rha-Rha-C10-C10, Rha-C10-C12:1, and Rha-C10-C12. Interestingly, more mono-rhamnolipids were produced by strain LP20 with a relative abundance of 64.5%. Pseudomonas aeruginosa LP20 optimally produced rhamnolipids at a pH of 7.0 and a salinity of 0.1% using glycerol and nitrate. The culture medium for rhamnolipids by strain LP20 was optimized by response surface methodology. LP20 produced rhamnolipids up to 6.9 g L−1, increased by 116%. Rhamnolipids produced from LP20 decreased the water surface tension to 28.1 mN m−1 with a critical micelle concentration of 60 mg L−1. The produced rhamnolipids emulsified many hydrocarbons with EI24 values higher than 56% and showed antimicrobial activity against Staphylococcus aureus and Cladosporium sp. with inhibition rates 48.5% and 17.9%, respectively. Pseudomonas aeruginosa LP20 produced more proportion of mono-rhamnolipids, and the LP20 rhamnolipids exhibited favorable activities and promising potential in microbial-enhanced oil recovery, bioremediation, and agricultural biocontrol. [ABSTRACT FROM AUTHOR]

Cotton tree (Bombax ceiba L.) flower stamen has been used widely as a northern Thai food ingredient. In this work, microwave extraction was applied to obtain the Bombax ceiba L. (BOMBAX) flower stamen extract for use as a reducing agent in the green synthesis of silver nanoparticles (AgNPs). The concentration of BOMBAX used was in the range of 0.05 to 0.25 wt%. Quasi-spherical and semi-rectangular shapes of AgNPs were obtained. The synthesized AgNPs showed a high mean zeta potential value of more than -30 mV, indicating the long-term stability and superior dispersity of AgNPs due to the repulsion of negative charges. Furthermore, the antibacterial potency of the synthesized AgNPs affords a good inhibition zone for both gram-negative and gram-positive bacteria, especially the gram-negative and antibiotic-resistant bacteria Pseudomonas aeruginosa, showing an inhibition zone diameter of 19.4±0.4 mm compared with that of chlophenicol (13.0±0.0 mm). This result suggests that the synthesized AgNPs present good colloidal stability and show good potential as an antibacterial agent for antibiotic-resistant bacteria, especially P. aeruginosa. [ABSTRACT FROM AUTHOR]

In present investigation, a potential L-asparaginase-producing bacterial isolate, Pseudomonas aeruginosa CSPS4, has been explored to enhance the production and purification of the asparaginase enzyme. Production of L-asparaginase is enhanced using the 'one variable at a time approach (OVAT)'. In Placket Burman (PB) analysis, pH, sucrose, and temperature significantly influence L-asparaginase production. Thereafter, L-asparaginase enzyme was recovered from culture broth using fractional precipitation with chilled acetone. The partially purified L-asparaginase showed a molecular weight of ~35 KDa on SDS-PAGE. L-asparaginase was characterized as a thermo-acidophilic enzyme exhibiting optimum pH and temperature of 6.0 and 60 °C, respectively. These characteristics render this enzyme novel from other available asparaginases of Pseudomonas spp. L-asparaginase activity remained unaffected by different modulators. L-asparaginase of this investigation was successfully employed for acrylamide degradation in commercial fried potato chips, establishing its applicability in food industries. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is a Gram‐negative bacterium and an opportunistic pathogen ubiquitously present throughout nature. LecB, a fucose‐, and mannose‐binding lectin, is a prominent virulence factor of P. aeruginosa, which can be expressed on the bacterial surface but also be secreted. However, the LecB interaction with human immune cells remains to be characterized. Neutrophils comprise the first line of defense against infections and their production of reactive oxygen species (ROS) and release of extracellular traps (NETs) are critical antimicrobial mechanisms. When profiling the neutrophil glycome we found several glycoconjugates on granule and plasma membranes that could potentially act as LecB receptors. In line with this, we here show that soluble LecB can activate primed neutrophils to produce high levels of intracellular ROS (icROS), an effect that was inhibited by methyl fucoside. On the other hand, soluble LecB inhibits P. aeruginosa‐induced icROS production. In support of that, during phagocytosis of wild‐type and LecB‐deficient P. aeruginosa, bacteria with LecB induced less icROS production as compared with bacteria lacking the lectin. Hence, LecB can either induce or inhibit icROS production in neutrophils depending on the circumstances, demonstrating a novel and potential role for LecB as an immunomodulator of neutrophil functional responses. [ABSTRACT FROM AUTHOR]

Sound has been shown to impact microbial behaviors. However, our understanding of the chemical and molecular mechanisms underlying these microbial responses to acoustic vibration is limited. In this study, we used untargeted metabolomics analysis to investigate the effects of 100-Hz acoustic vibration on the intra- and extracellular hydrophobic metabolites of P. aeruginosa PAO1. Our findings revealed increased levels of fatty acids and their derivatives, quinolones, and N-acylethanolamines upon sound exposure, while rhamnolipids (RLs) showed decreased levels. Further quantitative real-time polymerase chain reaction experiments showed slight downregulation of the rhlA gene (1.3-fold) and upregulation of fabY (1.5-fold), fadE (1.7-fold), and pqsA (1.4-fold) genes, which are associated with RL, fatty acid, and quinolone biosynthesis. However, no alterations in the genes related to the rpoS regulators or quorum-sensing networks were observed. Supplementing sodium oleate to P. aeruginosa cultures to simulate the effects of sound resulted in increased tolerance of P. aeruginosa in the presence of sound at 48 h, suggesting a potential novel response-tolerance correlation. In contrast, adding RL, which went against the response direction, did not affect its growth. Overall, these findings provide potential implications for the control and manipulation of virulence and bacterial characteristics for medical and industrial applications. [ABSTRACT FROM AUTHOR]

Introduction: Pseudomonas aeruginosa (P. aeruginosa) is a common pathogen associated with biofilm infections, which can lead to persistent infections. Therefore, there is an urgent need to develop new anti-biofilm drugs. DZ2002 is a reversible inhibitor that targets S-adenosylhomocysteine hydrolase and possesses anti-inflammatory and immune-regulatory activities. However, its anti-biofilm activity has not been reported yet. Methods and results: Therefore, we investigated the effect of DZ2002 on P. aeruginosa PAO1 biofilm formation by crystal violet staining (CV), real-time quantitative polymerase chain reaction (RT-qPCR) and confocal laser scanning microscopy (CLSM). The results indicated that although DZ2002 didn’t affect the growth of planktonic PAO1, it could significantly inhibit the formation of mature biofilms. During the inhibition of biofilm formation by DZ2002, there was a parallel decrease in the synthesis of alginate and the expression level of alginate genes, along with a weakening of swarming motility. However, these results were unrelated to the expression of lasI, lasR, rhII, rhIR. Additionally, we also found that after treatment with DZ2002, the biofilms and extracellular DNA content of PAO1 were significantly reduced. Molecular docking results further confirmed that DZ2002 had a strong binding affinity with the active site of Sadenosylhomocysteine hydrolase (SahH) of PAO1. Discussion: In summary, our results indicated that DZ2002 may interact with SahH in PAO1, inhibiting the formation of mature biofilms by downregulating alginate synthesis, extracellular DNA production and swarming motility. These findings demonstrate the potential value of DZ2002 in treating biofilm infections associated with P. aeruginosa. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is a highly pathogenic bacterium known for its ability to sense and coordinate the production of virulence factors in response to host immune responses. However, the regulatory mechanisms underlying this process have remained largely elusive. In this study, we investigate the two-component system CprRS in P. aeruginosa and unveil the crucial role of the sensor protein CprS in sensing the human host defense peptide LL-37, thereby modulating bacterial virulence. We demonstrate that CprS acts as a phosphatase in the presence of LL-37, leading to the phosphorylation and activation of the response regulator CprR. The results prove that CprR directly recognizes a specific sequence within the promoter region of the HigBA toxin-antitoxin system, resulting in enhanced expression of the toxin HigB. Importantly, LL-37-induced HigB expression promotes the production of type III secretion system effectors, leading to reduced expression of proinflammatory cytokines and increased cytotoxicity towards macrophages. Moreover, mutations in cprS or cprR significantly impair bacterial survival in both macrophage and insect infection models. This study uncovers the regulatory mechanism of the CprRS system, enabling P. aeruginosa to detect and respond to human innate immune responses while maintaining a balanced virulence gene expression profile. Additionally, this study provides new evidence and insights into the complex regulatory system of T3SS in P. aeruginosa within the host environment, contributing to a better understanding of host-microbe communication and the development of novel strategies to combat bacterial infections. Author summary: Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium that commonly causes fatal infections in immunosuppressed individuals. However, the underlying mechanisms that enable P. aeruginosa to adapt to capricious environments of the human body are still poorly understood. Recent studies unveil that two-component systems (TCSs) play a vital role in pathogenesis by sensing environmental cues and modulating gene expression in P. aeruginosa. In this study, we identified the CprRS, one of TCSs in P. aeruginosa, as an essential virulence factor. The sensor protein CprS directly interacts with human host defense peptide LL-37 and activates the response regulator CprR, which then coordinates the activities of type III secretion system for higher cytotoxicity. Loss of cprS or cprR significantly impairs bacterial survival in macrophage and host colonization. Collectively, this work contributes to explain the potent role of CprRS in the molecular-level of host-microbe communication to efficiently survival within the human host. [ABSTRACT FROM AUTHOR]

Indigenous micro-organisms often possess the ability to degrade petroleum hydrocarbon (PHC) in polluted soil. However, this process can be improved by supplementing with nutrients or the addition of more potent microbes. In this study, the ability of kenaf-core to stimulate the PHC degradation capability of microbial isolates from PHC polluted soil samples was evaluated. The standard experimental methods used in this study include: the digestion and analysis of the physico-chemical properties of petroleum hydrocarbon contaminated and non-contaminated soil samples; evaluation of petroleum hydrocarbon biodegradation using bio-augmentation and bio-stimulation (with kenaf-core) treatments; and, determination of soil microbial enzyme activities. Results from this study show that K, Na, total nitrogen, organic carbon, exchangeable cations, and heavy metals were found to be significantly (P < 0.05) higher in the polluted soil than in the non-polluted soil. Also, the polluted samples had pH values ranging from 5.5 to 6.0 while the non-polluted samples had a pH of 7.6. The microbial enzyme activities were comparatively lower in the polluted soils as compared to the non-polluted soil. The percentage degradation in the kenaf-core treated samples (AZ1T2—78.38; BN3T2—70.69; OL1T2—71.06; OT1T2—70.10) were significantly (P < 0.05) higher than those of the untreated (AZ1T1—13.50; BN3T1—12.50; OL1T1—10.55; OT1T1—9.50). The degradation of petroleum hydrocarbon in the bio-augmented and bio-stimulated treatments increased with increasing time of incubation, and were higher than that of the untreated sample. Comparatively, the treatment with a combination of kenaf-core and rhamnolipid exhibited a significantly (P < 0.05) higher degradation rate than that of the treatment with only kenaf core or rhamnolipid. While, the bio-stimulated and bio-augmented treatments had appreciable microbial counts that are higher than that of the untreated. In conclusion, the nutrient-supplement with kenaf-core significantly enhanced microbial growth and activities in the soil, thus improving their ability to biodegrade petroleum hydrocarbons in the polluted soils. Thus, supplementing with Kenaf core to encourage microbiological degradation of petroleum hydrocarbon is recommended. [ABSTRACT FROM AUTHOR]

Foam formation is a massive challenge in submerged aerated bioprocesses, e.g., in beer fermentation. While the use of antifoam may easily overcome foaming at laboratory scale, it is often an unattractive solution since the challenge remains in future upscaling, as reduced mass transfer and extra steps in product purification and analytics result in increased costs. Interestingly, the number of studies tackling this challenge is relatively low, although literature suggests a range of alternatives, from avoiding foaming to means of controlling or even using foaming as an in situ product removal. Here we give an overview of the topic in five subsections. (1) We argue that a sound understanding of the molecular origin of foaming can facilitate solutions for overcoming the challenge while introducing some long-known challenges (i.e., in beer fermentation). We then review in (2) the apparent avoidance of foam formation before we in (3) summarize possibilities to reduce and control foam after its formation. Subsequently, in (4), we discuss possible solutions that take advantage of foam formation, for example, via foam fractionation for in situ product removal. Finally, in (5), we provide an overview of microbial strain engineering approaches to cope with some aspects of foaming in fermentations. With this review, we would like to sensitize and inform the interested reader while offering an overview of the current literature for the expert, particularly with regard to the foam special issue in Discover Chemical Engineering. [ABSTRACT FROM AUTHOR]

The performance of chemical and biological additives in the methane hydrates formation and dissociation processes is of relevance for the development of gas-transport and gas-storage systems. The effect of sodium surfactin, rhamnolipids, and sodium dodecyl sulfate (SDS) on the methane hydrate formation process was assessed in this work at different temperatures and a fixed pressure of 50 bar. The studied parameters were induction time, methane uptake, period to reach 90 percent of the consumed gas, water-to-hydrate conversion, and formation rate. Concentrations for sodium surfactin were 3, 150, 750, 1500, 2000, and 2500 ppm, while rhamnolipids and SDS solutions were analyzed at 1500, 2000, and 2500 ppm. Performance testing of these additives was carried out by means of the isochoric–isothermal method. The experimental setup consisted of an isochoric three-cell array with 300 mL of capacity and magnetic stirring. According to the results, the sodium surfactin promoted the methane hydrate formation since the kinetics were higher and the water-to-hydrate conversion averaged 24.3%; meanwhile, the gas uptake increased as concentration was rising, and the induction time was reduced even at a temperature of 276.15 K. [ABSTRACT FROM AUTHOR]

In the context of the development of enhanced oil recovery technology, biotechnology can be used to develop new methods that are more environmentally friendly and sustainable, one of which is the use of biosurfactants. Rhamnolipids and sophorolipids are non-toxic biosurfactants, biodegradable, and environmentally favorable substances. This study compares the results of laboratory studies on fluid-to-fluid interactions, including the interfacial tension and rock wetness tests at various concentrations and salinities, which represent high salinity, medium salinity, and low salinity. The mechanism of these two biosurfactants is based on reducing the interfacial tension (IFT) between the fluids and changing the wettability of the rock to a more water-wet state. In the interfacial tension test, the reduction in the interfacial tension of rhamnolipids reached 10-2 mN/m, while that of sophorolipids only reached 10-1 mN/m. Then, the sandstone wettability test showed that the two biosurfactants were classified as water-wet (<75°). This happens because of its chemical structure, which has two parts: the hydrophobic part and the hydrophilic part. Within the salinity range of 8,000-32,000 ppm, the rhamnolipids work better in the higher salinity to reduce interfacial tension, and the salinity has a subtle effect on the contact angle. On the other hand, sophorolipids were not affected by salinity for both interfacial tension and contact angle. These two biosurfactants have the potential to increase oil recovery in sandstone so that they can contribute to environmentally friendly biotechnology. [ABSTRACT FROM AUTHOR]

Rhamnolipids (RL) are biosurfactants naturally produced by the opportunistic pathogen Pseudomonas aeruginosa. Currently, RL are commercialized for various applications and produced by Pseudomonas putida due to the health risks associated with their large‐scale production by P. aeruginosa. In this work, we show that RL containing one or two rhamnose moieties (mono‐RL or di‐RL, respectively) can be produced by the innocuous soil‐bacterium Pseudomonas chlororaphis subsp chlororaphis ATCC 9446 at titres up to 66 mg/L (about 86% of the production of P. aeruginosa PAO1 in the same culture conditions). The production of RL depends on the expression of P. aeruginosa PAO1 genes encoding the enzymes RhlA, RhlB and RhlC. These genes were introduced in a plasmid, together with a transcriptional regulator (rhlR) forming part of the same operon, with and without RhlC. We show that the activation of rhlAB by RhlR depends on its interaction with P. chlororaphis endogenous acyl‐homoserine lactones, which are synthetized by either PhzI or CsaI autoinducer synthases (producing 3‐hydroxy‐hexanoyl homoserine lactone, 3OH‐C6‐HSL, or 3‐oxo‐hexanoyl homoserine lactone, 3O‐C6‐HSL, respectively). P. chlororaphis transcriptional regulator couple with 3OH‐C6‐HSL is the primary activator of gene expression for phenazine‐1‐carboxylic acid (PCA) and phenazine‐1‐carboxamide (PCN) production in this soil bacterium. We show that RhlR coupled with 3OH‐C6‐HSL or 3O‐C6‐HSL promotes RL production and increases the production of PCA in P. chlororaphis. However, PhzR/3OH‐C6‐HSL or CsaR/3O‐C6‐HSL cannot activate the expression of the rhlAB operon to produce mono‐RL. These results reveal a complex regulatory interaction between RhlR and P. chlororaphis quorum‐sensing signals and highlight the biotechnology potential of P. chlororaphis ATCC 9446 expressing P. aeruginosa rhlAB‐R or rhlAB‐R‐C for the industrial production of RL. [ABSTRACT FROM AUTHOR]

Several foods are used in both the nutraceutical and health sectors; vegetable oils, for example, can prevent the onset of numerous diseases. The properties of these oils are related to their chemical composition and primarily to the presence of fatty acids. The present work aimed to determine the chemical profiles of Argania spinosa, Pinus halepensis, and Pistacia altantica oils, used in traditional Tunisian foods, and to evaluate some biological properties. We evaluated their antioxidant, anti-enzymatic, antimicrobial, and anti-inflammatory properties. Linoleic acid was the main component of the three oils. P. atlantica oil showed more significant inhibitory activity against the enzymes studied than A. spinosa and P. halepensis. All three oils showed similar antioxidant and anti-inflammatory activity. Furthermore, A. spinosa and P. halepensis oils showed antibiofilm activity against P. aeruginosa, with 30–40% inhibition. These results focus on the possible use of these oils in the nutraceutical and healthcare sectors. [ABSTRACT FROM AUTHOR]

Biosurfactants are surface-active compounds synthesized by microorganisms as secondary metabolites with important applications in medicine, cosmetics, food, oil, agriculture, and the pharmaceutical industries. In the present study, the Pseudomonas fluorescens ICCF 392 strain was screened to determine its ability to produce extracellular biosurfactants. The strain was cultivated on M44 liquid medium (5% (v/v) glycerol as a carbon source) and also, on M44 modified medium (by replacing the glycerol as a carbon source with 5% (v/v) waste cooking oil). The supernatants obtained at the end of the bioprocesses were evaluated, to confirm the ability of the strain in biosurfactant production, using the drop collaps method, oil spreading technique, and emulsification activity determination (E24). The best results were obtained in the case of the M44 liquid medium. The partially purified bioactive compounds were analyzed by the TLC method, which indicated the nature of the biosurfactants produced as rhamnolipids. Therefore, our results showed that the Pseudomonas fluorescens ICCF 392 strain was efficient in biosurfactant production, using glycerol or waste cooking oil as carbon sources in the biosynthesis process. [ABSTRACT FROM AUTHOR]

A well-developed industrial sector based on biotechnology will significantly reduce dependence on chemical resources, contributing to climate change objectives and leading to a greener and more environmentally friendly growth. The key lies in developing new technologies for the sustainable transformation of renewable natural resources into bio-based products and biofuels. Bioeconomy involves the production of renewable biological resources and their conversion into food, feed, and bio-based products through innovative and efficient technologies provided by industrial biotechnology. This paper presents a general classification of biosurfactants used in industrial applications. The term "surfactant" is derived from "surface-active agent." Biosurfactants have become increasingly significant across various fields owing to their diverse properties, including enhanced biodegradability and reduced toxicity. They are categorized into high and low molecular weight molecules. Biosurfactants find applications in industries such as cosmetics, food processing, pharmaceuticals, and environmental bioremediation. While numerous surfactants are already in use in various industries, it's essential to develop indigenous technologies for the production of biosurfactants from local micro-organism. This would ensure their suitability for application in specific environments. [ABSTRACT FROM AUTHOR]

Objective: The Lauraceae plants comprised high amounts of essential oils, some of which established pharmacological potentials such as anticancer and antimicrobial activities. The Lauraceae essential oils are also used in cuisines and perfumes. The present study provides the chemical analysis of the leaf oils of Beilschmiedia tonkinensis and Lindera gracilipes, collected from Vietnam. Method: Chemical components in the obtained oils were identified by the GC-FID/MS. The MTT and broth microdilution assays were used to evaluate cytotoxic and antimicrobial effects, respectively. The protein interactions were viewed by a docking study. Result: Beilschmiedia tonkinensis leaf oil was characterized by sesquiterpene hydrocarbons (66.0%), in which bicyclogermacrene (23.3%), (E)-caryophyllene (21.9%), caryophyllene oxide (9.9%), and spathulenol (6.0%) were the main components. The major chemical class in L gracilipes leaf oil was still sesquiterpene hydrocarbons (64.2%) with bicyclogermacrene (32.2%) being the principal component. Both 2 oil samples (IC50 41.2-44.12 µg/mL) were actively cytotoxic against the proliferation of A-549 cancer cells. In particular, B tonkinensis leaf oil strongly controlled Hep-G2 and MCF-7 cancerous cells with the IC50 values of 20.6 and 9.36 µg/mL, respectively. Beilschmiedia tonkinensis leaf oil also strongly inhibited the Gram (-) bacterium Pseudomonas aeruginosa and the fungus Aspergillus niger with the MIC values of 16 and 32 µg/mL, respectively. By molecular docking approach, bicyclogermacrene interacted with the p38α MAPK cancer protein (PDB ID: 4FA2) with a potential binding affinity of -8.019 kcal/mol, whereas (E)-caryophyllene tends to bind 2 bacterial proteins P aeruginosa QS regulator (PDB ID: 6B8A) and glucosamine-6-phosphate synthase (GlmS) (PDB ID: 2VF5) with the better binding affinities of -6.740 and -6.521 kcal/mol, respectively. The most preferable binding mode was due to hydrophobic π-alkyl and alkyl interactions. Conclusion: The current result can be seen as a basic foundation in the applications of essential oils of B tonkinensis and L gracilipes for anticancer and antimicrobial treatments. Further phytochemical studies and mechanisms of action are needed. [ABSTRACT FROM AUTHOR]

Biosurfactants (surfactants synthesized by microorganisms) are produced by microorganisms and are suitable for use in different areas. Among biosurfactants, rhamnolipids are the most studied and popular, attracting scientists, and industries' interest. Due to their unique characteristics, the rhamnolipids have been used as synthetic surfactants' alternatives and explored in food applications. Besides the production challenges that need to be tackled to guarantee efficient production and low cost, their properties need to be adjusted to the final application, where the pH instability needs to be considered. Moreover, regulatory approval is needed to start being used in commercial applications. One characteristic of interest is their capacity to form oil-in-water nanosystems. Some of the most explored have been nanoemulsions, solid-lipid nanoparticles and nanostructured lipid carriers. This review presents an overview of the main properties of rhamnolipids, asserts the potential and efficiency of rhamnolipids to replace the synthetic surfactants in the development of nanosystems, and describes the rhamnolipids-based nanosystems used in food applications. It also discusses the main characteristics and methodologies used for their characterization and in the end, some of the main challenges are highlighted. [ABSTRACT FROM AUTHOR]

Quorum sensing is a mechanism of bacterial cell-cell communication that relies on the production and detection of small molecule autoinducers, which facilitate the synchronous expression of genes involved in group behaviors, such as virulence factor production and biofilm formation. The Pseudomonas aeruginosa quorum sensing network consists of multiple interconnected transcriptional regulators, with the transcription factor, RhlR, acting as one of the main drivers of quorum sensing behaviors. RhlR is a LuxR-type transcription factor that regulates its target genes when bound to its cognate autoinducer, C4-homoserine lactone, which is synthesized by RhlI. RhlR function is also regulated by the metallo-β-hydrolase enzyme, PqsE. We recently showed that PqsE binds RhlR to alter its affinity for promoter DNA, a new mechanism of quorum-sensing receptor activation. Here, we perform ChIP-seq analyses of RhlR to map the binding of RhlR across the P. aeruginosa genome, and to determine the impact of C4-homoserine lactone and PqsE on RhlR binding to different sites across the P. aeruginosa genome. We identify 40 RhlR binding sites, all but three of which are associated with genes known to be regulated by RhlR. C4-homoserine lactone is required for maximal binding of RhlR to many of its DNA sites. Moreover, C4-homoserine lactone is required for maximal RhlR-dependent transcription activation from all sites, regardless of whether it impacts RhlR binding to DNA. PqsE is required for maximal binding of RhlR to many DNA sites, with similar effects on RhlR-dependent transcription activation from those sites. However, the effects of PqsE on RhlR specificity are distinct from those of C4-homoserine lactone, and PqsE is sufficient for RhlR binding to some DNA sites in the absence of C4-homoserine lactone. Together, C4-homoserine lactone and PqsE are required for RhlR binding at the large majority of its DNA sites. Thus, our work reveals three distinct modes of activation by RhlR: i) when RhlR is unbound by autoinducer but bound by PqsE, ii) when RhlR is bound by autoinducer but not bound by PqsE, and iii) when RhlR is bound by both autoinducer and PqsE, establishing a stepwise mechanism for the progression of the RhlR-RhlI-PqsE quorum sensing pathway in P. aeruginosa. Author summary: Pseudomonas aeruginosa represents a serious threat to public health in the United States because of its intrinsic mechanisms of antimicrobial resistance. One of the primary drivers of its antimicrobial resistance profile is biofilm formation. Biofilms are multicellular communities that are formed in an ordered mechanism by the collective. In the case of P. aeruginosa, biofilm formation is controlled by a cell-cell communication process called quorum sensing. Quorum sensing underpins transcriptional changes in a bacterium, allowing for the transition from individual, planktonic behaviors to group, sessile behaviors. Group behaviors are behaviors that are only beneficial to engage in once a critical threshold of kin population is reached. The transition to group behaviors is mediated by quorum sensing through an interconnected regulatory system, with the transcription factor receptor RhlR regulating the expression of hundreds of genes. RhlR-dependent transcription relies on the detection of a ligand produced by its partner synthase, RhlI, and an accessory binding protein that alters its affinity for promoter DNA, PqsE, resulting in a dual regulatory mechanism that was not previously observed in quorum sensing. The main goal of this study was to determine the molecular basis for promoter selection by RhlR using bacterial genetics and DNA-based sequencing methods for measuring site-specific protein binding. Our approach established the entirety of the RhlR direct regulon and the contributions of each of the known regulators to RhlR-dependent promoter binding and gene regulation. [ABSTRACT FROM AUTHOR]

Candida tropicalis is a nonconventional yeast with medical and industrial significance, belonging to the CTG clade. Recent advancements in whole‐genome sequencing and genetic analysis revealed its close relation to other unconventional yeasts of biotechnological importance. C. tropicalis is known for its immense potential in synthesizing various valuable biomolecules such as ethanol, xylitol, biosurfactants, lipids, enzymes, α,ω‐dicarboxylic acids, single‐cell proteins, and more, making it an attractive target for biotechnological applications. This review provides an update on C. tropicalis biological characteristics and its efficiency in producing a diverse range of biomolecules with industrial significance from various feedstocks. The information presented in this review contributes to a better understanding of C. tropicalis and highlights its potential for biotechnological applications and market viability. [ABSTRACT FROM AUTHOR]

Rhamnolipid, as a low‐toxic, biodegradable and environmentally friendly biosurfactant, has broad application prospects in many industries. However, the quantitative determination of rhamnolipid is still a challenging task. Here, a new sensitive method for the quantitative analysis of rhamnolipid based on a simple derivatization reaction was developed. In this study, 3‐[3′‐(l‐rhamnopyranosyloxy) decanoyloxy] decanoic acid (Rha‐C10‐C10) and 3‐[3′‐(2′‐O‐α‐l‐rhamnopyranosyloxy) decanoyloxy] decanoic acid (Rha‐Rha‐C10‐C10) were utilized as the representative rhamnolipids. Liquid chromatography–mass spectrometry and high‐performance liquid chromatography‐ultra violet results showed that these two compounds were successfully labeled with 1 N1‐(4‐nitrophenyl)‐1,2‐ethylenediamine. There was an excellent linear relationship between rhamnolipid concentration and peak area of labeled rhamnolipid. The detection limits of the Rha‐C10‐C10 and Rha‐Rha‐C10‐C10 were 0.018 mg/L (36 nmol/L) and 0.014 mg/L (22 nmol/L), respectively. The established amidation method was suitable for the accurate analysis of rhamnolipids in the biotechnological process. The method had good reproducibility with the relative standard deviation of 0.96% and 0.79%, respectively, and sufficient accuracy with a recovery of 96%–100%. This method was applied to quantitative analysis of 10 rhamnolipid homologs metabolized by Pseudomonas aeruginosa LJ‐8. The single labeling method was used for the quantitative analysis of multiple components, which provided an effective method for the quality evaluation of other glycolipids with carboxyl groups. [ABSTRACT FROM AUTHOR]

The development of new approaches for the treatment of the increasingly antibiotic-resistant pathogen Pseudomonas aeruginosa was targeted by enhancing the effect of local antimicrobial photodynamic therapy (aPDT) using poly(ethylene glycol)-block-poly(lactic acid) (PEG114-block-PLAx) nanocarriers that were loaded with a ruthenium-based photosensitizer (PS). The action of tris(1,10-phenanthroline) ruthenium (II) bis(hexafluorophosphate) (RuPhen3) encapsulated in PEG114-block-PLAx micelles and vesicles was shown to result in an appreciable aPDT inactivation efficiency against planktonic Pseudomonas aeruginosa. In particular, the encapsulation of the PS, its release, and the efficiency of singlet oxygen (1O2) generation upon irradiation with blue light were studied spectroscopically. The antimicrobial effect was analyzed with two strains of Pseudomonas aeruginosa. Compared with PS-loaded micelles, formulations of the PS-loaded vesicles showed 10 times enhanced activity with a strong photodynamic inactivation effect of at least a 4.7 log reduction against both a Pseudomonas aeruginosa lab strain and a clinical isolate collected from the lung of a cystic fibrosis (CF) patient. This work lays the foundation for the targeted eradication of Pseudomonas aeruginosa using aPDT in various medical application areas. [ABSTRACT FROM AUTHOR]

The study was aimed at inhibiting the protease produced by Pseudomonas aeruginosa using an 80% alcoholic extract of Conocarpus lancifolius leaves. A total of 146 isolates of P. aeruginosa that were isolated and identified by microscopic and biochemical tests were 51 isolates submitted to primary and secondary screening techniques in order to choose the qualified P. aeruginosa isolate for protease synthesis. Among these isolates, forty-seven isolates showed hydrolysis zones on skim milk media (primary screening); six isolates were chosen for secondary screening. The result revealed that P. aeruginosa P51 had the highest ability to produce the enzyme, with a specific activity of 15.9 U/mg protein. In addition, the study included extracting the leaves of C. lancifolius using 80% ethanolic alcohol and conducting the GC-MC assay and the HPLC assay of the plant extract. The results revealed a significantly decreased specific activity of protease from 15.9 to 1.2 U/mg after treatment with 0.8 µg/ml of alcoholic extract of C. lancifolius leaves. [ABSTRACT FROM AUTHOR]

Previously, we pointed out in P. aeruginosa PAO1 biofilm cells the accumulation of a hypothetical protein named PA3731 and showed that the deletion of the corresponding gene impacted its biofilm formation capacity. PA3731 belongs to a cluster of 4 genes (pa3732 to pa3729) that we named bac for “Biofilm Associated Cluster.” The present study focuses on the PA14_16140 protein, i.e., the PA3732 (BacA) homolog in the PA14 strain. The role of BacA in rhamnolipid secretion, biofilm formation and virulence, was confirmed by phenotypic experiments with a bacA mutant. Additional investigations allow to advance that the bac system involves in fact 6 genes organized in operon, i.e., bacA to bacF. At a molecular level, quantitative proteomic studies revealed an accumulation of the BAC cognate partners by the bacA sessile mutant, suggesting a negative control of BacA toward the bac operon. Finally, a first crystallographic structure of BacA was obtained revealing a structure homologous to chaperones or/and regulatory proteins.

Rhamnolipids (RLs) are well-studied biosurfactants naturally produced by pathogenic strains of Pseudomonas aeruginosa. Current methods to produce RLs in native and heterologous hosts have focused on carbohydrates as production substrate; however, methane (CH4) provides an intriguing alternative as a substrate for RL production because it is low cost and may mitigate greenhouse gas emissions. Here, we demonstrate RL production from CH4 by Methylotuvimicrobium alcaliphilum DSM19304. RLs are inhibitory to M. alcaliphilum growth (

We performed this study in order to evaluate the control effect and mechanism of the biosurfactant rhamnolipids (RLS) on black spot disease caused by Alternaria alternata in pear fruit. The results showed that RLS treatment at a mass concentration of 20 mg/mL effectively enhanced resistance to A. alternata, and the lesion diameter was only 64.29% of that of the control group at 12 days following the treatment. Furthermore, it was shown that compared to the control group, RLS treatment significantly increased the activities of phenylalanine ammonia lyase (PAL), cinnamate acid 4-hydroxylase (C4H), 4-coumarate coenzyme A ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD), as well as the contents of total phenols and flavonoids in pear fruit tissue. The activities of chitinase and β-1,3-glucanase were significantly induced. The activities of NADPH oxidase (NOX), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), and the contents of H2O2 and superoxide anion radical in the early and middle stages of storage were also increased by RLS treatment. Meanwhile, the ascorbate-glutathione (ASA-GSH) cycle was activated to maintain the dynamic balance of reactive oxygen species (ROS) production and scavenging in pear fruit tissue, and the membrane permeability and the content of malondialdehyde (MDA) were reduced. Collectively, this study suggested that post-harvest rhamnolipid treatment can enhance black spot disease resistance in pear fruit by regulating phenylpropane metabolism, ROS metabolism and pathogenesis-related proteins.