Biofilm Formation Activity Research Articles

Cyclic di-GMP incorporates the transcriptional factor FleQ03 in Pseudomonas syringae MB03 to elicit biofilm-dependent resistance in response to Caenorhabditis elegans predation

Bacteria usually form biofilms as a defense mechanism against predation by bacterivorous nematodes. In this context, the second messenger c-di-GMP from the wild-type Pseudomonas syringae MB03 actuates the transcriptional factor FleQ03 to elicit biofilm-dependent nematicidal activity against Caenorhabditis elegans N2. P. syringae MB03 cells exhibited nematicidal activity and c-di-GMP content in P. syringae MB03 cells was increased after feeding to nematodes. Expression of a diguanylate cyclase (DGC) gene in P. syringae MB03 resulted in an increased c-di-GMP content, biofilm yield and nematicidal activity, whereas converse effects were obtained when expressing a phosphodiesterase (PDE) gene. Molecular docking and isothermal titration calorimetry assays verified the affinity activity between c-di-GMP and the FleQ03 protein. The disruption of the fleQ03 gene in P. syringae MB03, while increasing c-di-GMP content, significantly diminished both biofilm formation and nematicidal activity. Interestingly, P. syringae MB03 formed a full-body biofilm around the worms against predation, probably extending from the tail to the head, whereas it was not observed in the fleQ03 gene disrupted cells. Thus, we hypothesized that c-di-GMP incorporated FleQ03 to reinforce bacterial biofilm and biofilm-dependent pathogenicity in response to C. elegans predation, providing insights into a possible means of resisting bacterivorous nematodes by bacteria in natural ecosystems.

The roles of cell wall inhibition responsive protein CwrA in the pathogenicity of staphylococcus aureus

ABSTRACT The ability to form robust biofilms and secrete a diverse array of virulence factors are key pathogenic determinants of Staphylococcus aureus, causing a wide range of infectious diseases. Here, we characterized cwrA as a VraR-regulated gene encoding a cell wall inhibition-responsive protein (CwrA) using electrophoretic mobility shift assays. We constructed cwrA deletion mutants in the genetic background of methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) strains. Phenotypic analyses indicated that deletion of cwrA led to impaired biofilm formation, which was correlated with polysaccharide intercellular adhesin (PIA). Besides, the results of real-time quantitative PCR (RT-qPCR) and β-galactosidase activity assay revealed that CwrA promoted biofilm formation by influence the ica operon activity in S. aureus. Furthermore, cwrA deletion mutants released less extracellular DNA (eDNA) in the biofilm because of their reduced autolytic activity compared to the wild-type (WT) strains. We also found that cwrA deletion mutant more virulence than the parental strain because of its enhanced haemolytic activity. Mechanistically, this phenotypic alteration is related to activation of the SaeRS two-component system, which positively regulates the transcriptional levels of genes encoding membrane-damaging toxins. Overall, our results suggest that CwrA plays an important role in modulating biofilm formation and haemolytic activity in S. aureus.

Antibiofilm and antivirulence potentials of iodinated fmoc-phenylalanine against Staphylococcus aureus

Staphylococcus aureus poses significant risks to public health due to its ability to form biofilm and produce virulence factors, contributing to the increase in antibiotic resistance and treatment complications. This emphasizes the urgent need for novel antimicrobial controls. Based on the premise that halogenation improves antimicrobial efficacy, this study investigated the ability of halogenated phenylalanine to effectively inhibit S. aureus biofilm formation and virulence activities. Among 29 halogenated compounds, Fmoc-4-iodo-phenylalanine (Fmoc-Iodo-Phe) displayed the highest antibiofilm effect against S. aureus, achieving 94.3 % reduction at 50 μg/mL. Microscopic studies confirmed its ability to prevent and disrupt mature biofilms. At 10 μg/mL, Fmoc-Iodo-Phe markedly inhibited virulence factors, such as cell surface hydrophobicity, hemolysin and slime production. It showed low propensity for resistance development and effectively inhibited biofilms formed by methicillin-resistant S. aureus (MRSA) and S. epidermidis, but was inactive against Gram-negative bacteria. Gene expression analysis complemented by molecular docking suggest that Fmoc-Iodo-Phe could target the AgrA quorum sensing cascade due to strong interactions with key residues at its DNA binding sites. Notably, it was non-cytotoxic in Caenorhabditis elegans model and satisfied drug-likeliness criteria based on ADMET prediction. Therefore, our findings position Fmoc-Iodo-Phe as a promising antimicrobial candidate against S. aureus infections, underscoring its potential as an alternative to traditional antibiotics.

Biofilm Formation by Lactobacillus Strains of Modern Probiotics and Their Antagonistic Activity against Opportunistic Bacteria.

The species identity of the studied lactobacillus strains was confirmed by matrix-activated laser desorption/ionization with time-of-flight ion separation (MALDI-TOF mass spectrometry). Lactobacillus strains differed in the dynamics of lactic acid accumulation and changes in the pH of the culture medium. The culture medium affected adhesion ability of lactobacilli. The ability to adhere does not affect the formation of biofilms by lactobacillus strains except for the L. acidophilus La5 strain, which has low adhesion ability and fewer microbial cells detected after mechanical destruction of the biofilm. The metabiotics of the lactobacillus culture medium have an antagonistic effect on conditionally pathogenic microorganisms. Adhesion, biofilm formation, and antagonistic activity of probiotic lactobacillus strains are strain-specific properties.

Assessment of the antimicrobial and antibiofilm activity of the combination of N-acetyl cysteine and carvacrol against Staphylococcus aureus, the most common orthopedic infectious agent

BackgroundThe increasing prevalence of antibiotic-resistant bacterial infections has led to the search for new approaches. ObjectiveThis study aimed to evaluate the effects of carvacrol and N-acetyl cysteine, both individually and in combination, on the planktonic cells and biofilm formations of Staphylococcus aureus, including methicillin-resistant and methicillin-sensitive strains. Additionally, the study sought to perform cytotoxicity tests and chemical characterization to further understand the properties and potential applications of these substances. MethodsA total of 19 S. aureus strains were included in the study. Minimum inhibitory concentration and minimum bactericidal concentration were determined by assays. Synergy analysis tests were carried out. Cytotoxicity tests were conducted on the fibroblast cell line. Characterization test was performed. ResultsWhile Minimum inhibitory concentration and minimum bactericidal concentration values for carvacrol varied between 250 and 500 μg/ml, these values were in the range of 32–64 mg/ml for N-acetyl cysteine. Biofilm formation activities were identified. A total of eight strains, including six clinical and two standard strains with the highest biofilm-forming ability, were selected for combination studies. The combination of Carvacrol and N-acetyl cysteine exhibited synergistic and partially synergistic effects on the tested planktonic and biofilm strains, and these effects were dose-dependent. Carvacrol was found to be the most active drug at the end of 24, 48, and 72 h. Regarding the synergistic effect of N-acetyl cysteine + carvacrol, it was revealed to exhibit higher activity than N-acetyl cysteine and lower activity than carvacrol. ConclusionThe combination of carvacrol and N-acetyl cysteine demonstrated synergistic and partially synergistic effects against both planktonic and biofilm forms of Staphylococcus aureus. These results suggest potential for novel approaches in managing orthopedic infections, warranting further research to explore their therapeutic applications.

Antivirulence activities of Rutin-loaded chitosan nanoparticles against pathogenic Staphylococcus aureus

BackgroundStaphylococcus aureus is an infectious bacterium that is frequently found in healthcare settings and the community. This study aimed to prepare rutin-loaded chitosan nanoparticles (Rut-CS NPs) and assess their antibacterial activity against pathogenic strains of S. aureus.ResultsThe synthesized Rut-CS NPs exhibited an amorphous morphology with a size ranging from 160 to 240 nm and a zeta potential of 37.3 mV. Rut-CS NPs demonstrated significant antibacterial activity against S. aureus strains. Following exposure to Rut-CS NPs, the production of staphyloxanthin pigment decreased by 43.31–89.63%, leading to increased susceptibility of S. aureus to hydrogen peroxide. Additionally, visual inspection of cell morphology indicated changes in membrane integrity and permeability upon Rut-CS NPs exposure, leading to a substantial increase (107.07–191.08%) in cytoplasmic DNA leakage in the strains. Furthermore, ½ MIC of Rut-CS NPs effectively inhibited the biofilm formation (22.5–37.5%) and hemolytic activity (69–82.59%) in the S. aureus strains.ConclusionsOur study showcases that Rut-CS NPs can serve as a novel treatment agent to combat S. aureus infections by altering cell morphology and inhibiting virulence factors of S. aureus.

Detection of virulent Klebsiella pneumoniae strains causing intestinal and extraintestinal infections during the 80s and 90s in Brazil.

Klebsiella pneumoniae is an important pathogen that causes several human infections, which is currently among the main bacterial species of clinical importance. Given the importance of understanding the characteristics of this pathogen and its evolutionary aspects, in this study, we sought to characterize strains of K. pneumoniae recovered in the 1980s and 1990s in São Paulo, Brazil. Our analyses included 48 strains recovered from diarrheagenic stools and extraintestinal infections. These strains were submitted to screening for virulence and ESβL-encoding genes, antimicrobial susceptibility tests, biofilm formation, and hypermucosity and hemolytic activity tests. Our results revealed that among the studied virulence genes, the most frequent were entB (100%), followed by iutA (100%), mrkD (98%), and ycfM (72%). Phenotypic tests revealed that the strains were non- hemolytic, and two strains were positive for the hypermucoviscosity phenotype but did not have the genetic markers associated with this phenotype. Furthermore, 17% of the isolates proved to be strong biofilm producers. Antimicrobial susceptibility testing demonstrated that most strains were susceptible to the tested antimicrobials, with the exception of five isolates that produced CTX-M-2. Our findings indicate that the collection of strains studied showed variability in virulence factors, as well as biofilm production. Still, a minority of the strains showed clinically significant resistance mechanisms. As far as we know, this is the oldest collection of K. pneumoniae studied in the country.Keywords: Bacterial virulence; Ancient bacterial strains; Enterobacterales; Bacterial infection; Diarrhea.

Hurdle Concept and the Role of Lactic Acid Bacteria

The hurdle idea is a food preservation technique that includes building up a number of barriers to prevent microbes from growing and prolong the shelf life of perishable goods. The idea of using lactic acid bacteria (LAB), which are essential for food preservation, is one that is significant. Through a variety of processes, including fermentation, competitive exclusion, metabolite generation, biofilm formation, nutritional competition, and metabolic activity, LAB support the hurdle concept. Lactic acid bacteria (LAB) ferment glucose to produce lactic acid, which results in an acidic environment that prevents infections and spoiling germs from growing.

Hurdle Concept and The Role of Lactic Acid Bacteria

The hurdle idea is a food preservation technique that includes building up a number of barriers to prevent microbes from growing and prolong the shelf life of perishable goods. The idea of using lactic acid bacteria (LAB), which are essential for food preservation, is one that is significant. Through a variety of processes, including fermentation, competitive exclusion, metabolite generation, biofilm formation, nutritional competition, and metabolic activity, LAB support the hurdle concept. Lactic acid bacteria (LAB) ferment glucose to produce lactic acid, which results in an acidic environment that prevents infections and spoiling germs from growing. Additionally, LAB generates antimicrobial substances such as hydrogen peroxide, organic acids, and bacteriocins, which work by competitively excluding harmful germs from growing. Furthermore, metabolites of lactic acid bacteria (LAB) such acetic acid, diacetyl, and carbon dioxide enhance the flavor of fermented foods and serve as organic preservatives. Moreover, LAB have the ability to create biofilms that shield them from antimicrobial agents and environmental stressors, increasing their survival and persistence in food matrices. By means of nutritional competition, LAB outcompetes pathogenic or spoilage bacteria in the consumption of available resources, hence restricting their growth. In addition, LAB produces enzymes and antibacterial substances, among other metabolic activities that further impede the growth of infections.

Phylogenetic Diversity, Antibiotic Resistance, and Virulence of Escherichia coli Strains from Urinary Tract Infections in Algeria.

Urinary tract infections (UTIs) caused by Escherichia coli represent a significant public health concern due to the high virulence and antimicrobial resistance exhibited by these pathogens. This study aimed to analyze the phylogenetic diversity and antibiotic resistance profiles of Uropathogenic E. coli (UPEC) strains isolated from UTI patients in Algeria, focusing on virulence factors such as extended β-lactamase (ESBL) production, biofilm formation, and hemolytic activity. Phylogenetic grouping of 86 clinical imipenem resistant E. coli isolates showed the prevalence of group B2 (48.9%), followed by groups E (22.1%), unknown (12.8%), A (8.1%), and B1 (4.7%), and Clade I, D, Clade I, or Clade II (1.2%). The highest resistance rates were observed towards amoxicillin (86.04%), ticarcillin (82.55%), piperacillin (73.25%), nitrofurantoin (84.88%), and trimethoprim-sulfamethoxazole (51.16%). Notably, 69.8% of UPEC strains were multidrug-resistant (MDR) and 23.2% were extensively drug-resistant (XDR). Additionally, 48.9%, 42%, and 71% of strains demonstrated ESBL production, hemolytic activity, and weak biofilm production, respectively. Continuous monitoring and characterization of UPEC strains are essential to track the spread of the most resistant and virulent phylogenetic groups over time, facilitating rapid therapeutic decisions to treat infections and prevent the emergence of new resistant organisms, helping choose the most effective antibiotics and reducing treatment failure.

Low-dose zinc oxide nanoparticles trigger the growth and biofilm formation of Pseudomonas aeruginosa: a hormetic response

IntroductionHormesis describes an inverse dose-response relationship, whereby a high dose of a toxic compound is inhibitory, and a low dose is stimulatory. This study explores the hormetic response of low concentrations of zinc oxide nanoparticles (ZnO NPs) toward Pseudomonas aeruginosa.MethodSamples of P. aeruginosa, i.e. the reference strain, ATCC 27,853, together with six strains recovered from patients with cystic fibrosis, were exposed to ten decreasing ZnO NPs doses (0.78–400 µg/mL). The ZnO NPs were manufactured from Peganum harmala using a chemical green synthesis approach, and their properties were verified utilizing X-ray diffraction and scanning electron microscopy. A microtiter plate technique was employed to investigate the impact of ZnO NPs on the growth, biofilm formation and metabolic activity of P. aeruginosa. Real-time polymerase chain reactions were performed to determine the effect of ZnO NPs on the expression of seven biofilm-encoding genes.ResultThe ZnO NPs demonstrated concentration-dependent bactericidal and antibiofilm efficiency at concentrations of 100–400 µg/mL. However, growth was significantly stimulated at ZnO NPs concentration of 25 µg/mL (ATCC 27853, Pa 3 and Pa 4) and at 12.5 µg/mL and 6.25 µg/mL (ATCC 27853, Pa 2, Pa 4 and Pa 5). No significant positive growth was detected at dilutions < 6.25 µg/mL. similarly, biofilm formation was stimulated at concentration of 12.5 µg/mL (ATCC 27853 and Pa 1) and at 6.25 µg/mL (Pa 4). At concentration of 12.5 µg/mL, ZnO NPs upregulated the expression of LasB ( ATCC 27853, Pa 1 and Pa 4) and LasR and LasI (ATCC 27853 and Pa 1) as well as RhII expression (ATCC 27853, Pa 2 and Pa 4).ConclusionWhen exposed to low ZnO NPs concentrations, P. aeruginosa behaves in a hormetic manner, undergoing positive growth and biofilm formation. These results highlight the importance of understanding the response of P. aeruginosa following exposure to low ZnO NPs concentrations.

Determination of in vitro synergy and antibiofilm activities of antimicrobials and essential oil components

Using existing adrentimicrobials with essential oil components to prevent antimicrobial resistance is an alternative strategy. This study aimed to evaluate the resistance status, synergistic combinations, and in vitro biofilm formation activities of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), Stenotrophomonas maltophilia and Candida albicans against antimicrobial agents and cinnamaldehyde, carvacrol, eugenol, limonene and eucalyptol. Antimicrobial activities were evaluated by microdilution, cytotoxicity by XTT, synergy by checkerboard and time-kill, and biofilm inhibition by microplate methods. Cinnamaldehyde and carvacrol showed strong antimicrobial activity. Synergistic effects were observed when using all essential oils with antimicrobials. Only two C. albicans isolates showed antagonism with cinnamaldehyde and fluconazole. The constituents showed cytotoxic effects in the L929 cell line (except limonene). A time-kill analysis revealed a bacteriostatic effect on S. maltophilia and MRSA isolates and a fungicidal effect on C. albicans isolates. These results are important for further research to improve antimicrobial efficacy or to develop new agents.

Repurposing promethazine hydrochloride to inhibit biofilm formation against Burkholderia thailandensis.

Melioidosis is a severe infectious disease caused by Burkholderia pseudomallei, an intracellular pathogen with a high mortality rate and significant antibiotic resistance. The high mortality rate and resistance to antibiotics have drawn considerable attention from researchers studying melioidosis. This study evaluated the effects of various concentrations (75, 50, and 25µg/mL) of promethazine hydrochloride (PTZ), a potent antihistamine, on biofilm formation and lipase activity after 24h of exposure to B. thailandensis E264. A concentration-dependent decrease in both biofilm biomass and lipase activity was observed. RT-PCR analysis revealed that PTZ treatment not only made the biofilm structure loose but also reduced the expression of btaR1, btaR2, btaR3, and scmR. Single gene knockouts of quorum sensing (QS) receptor proteins (∆btaR1, ∆btaR2, and ∆btaR3) were successfully constructed. Deletion of btaR1 affected biofilm formation in B. thailandensis, while deletion of btaR2 and btaR3 led to reduced lipase activity. Molecular docking and biological performance results demonstrated that PTZ inhibits biofilm formation and lipase activity by suppressing the expression of QS-regulated genes. This study found that repositioning PTZ reduced biofilm formation in B. thailandensis E264, suggesting a potential new approach for combating melioidosis.

Mangosteen extracts: Effects on intestinal bacteria, and application to functional fermented milk products

Mangosteen (Garcinia mangostana L.) is a tasty, polyphenol-rich tropical fruit. The edible part is highly appreciated by its aroma, taste and texture. The non-edible part, rich in polyphenols, has been traditionally used in Thai medicine. In this work, flavonoids and phenolic acid/derivatives were identified in mangosteen extracts (ME) from edible and non-edible portions. We first studied the effects of MEs on the growth, metabolism, antioxidant capacity, biofilm formation and antimicrobial capacity of eight bifidobacteria and lactobacilli strains from intestinal origin and two commercial probiotic strains (BB536 and GG). ME concentrations higher than 10–20 % were inhibitory for all strains. However, ME concentrations of 5 % significantly (P < 0.01) increased all strains antioxidant capacity, reduced biofilm-formation, and enhanced inhibition against Gram-positive pathogens. To apply these knowledge, bifunctional fermented milk products were elaborated with 5 % ME and individual strains, which were selected taking into account their growth with ME, and the widest range of values on antioxidant capacity, biofilm formation and antimicrobial activity (bifidobacteria INIA P2 and INIA P467, lactobacilli INIA P459 and INIA P708, and reference strain GG). Most strains survived well manufacture, refrigerated storage and an in vitro simulation of major conditions encountered in the gastrointestinal tract. As expected, products supplemented with ME showed higher polyphenol content and antioxidant capacity levels than control. After sensory evaluation, products containing strains INIA P2, INIA P708 and GG outstood as best.

The role of N-acetylcysteine on adhesion and biofilm formation of Candida parapsilosis isolated from catheter-related candidemia.

Objectives. Anti-fungal agents are increasingly becoming less effective due to the development of resistance. In addition, it is difficult to treat Candida organisms that form biofilms due to a lack of ability of drugs to penetrate the biofilms. We are attempting to assess the effect of a new therapeutic agent, N-acetylcysteine (NAC), on adhesion and biofilm formation in Candida parapsilosis clinical strains. Meanwhile, to detect the transcription level changes of adhesion and biofilm formation-associated genes (CpALS6, CpALS7, CpEFG1 and CpBCR1) when administrated with NAC in C. parapsilosis strains, furthermore, to explore the mechanism of drug interference on biofilms.Hypothesis/Gap statement. N-acetylcysteine (NAC) exhibits certain inhibitory effects on adhesion and biofilm formation in C. parapsilosis clinical strains from CRBSIs through: (1) down-regulating the expression of the CpEFG1 gene, making it a highly potential candidate for the treatment of C. parapsilosis catheter-related bloodstream infections (CRBSIs), (2) regulating the metabolism and biofilm -forming factors of cell structure.Methods. To determine whether non-antifungal agents can exhibit inhibitory effects on adhesion, amounts of total biofilm formation and metabolic activities of C. parapsilosis isolates from candidemia patients, NAC was added to the yeast suspensions at different concentrations, respectively. Reverse transcription was used to detect the transcriptional levels of adhesion-related genes (CpALS6 and CpALS7) and biofilm formation-related factors (CpEFG1 and CpBCR1) in the BCR1 knockout strain, CP7 and CP5 clinical strains in the presence of NAC. To further explore the mechanism of NAC on the biofilms of C. parapsilosis, RNA sequencing was used to calculate gene expression, comparing the differences among samples. Gene Ontology (GO) enrichment analysis helps to illustrate the difference between two particular samples on functional levels.Results. A high concentration of NAC reduces the total amount of biofilm formation in C. parapsilosis. Following co-incubation with NAC, the expression of CpEFG1 in both CP7 and CP5 clinical strains decreased, while there were no significant changes in the transcriptional levels of CpBCR1 compared with the untreated strain. GO enrichment analysis showed that the metabolism and biofilm-forming factors of cell structure were all regulated after NAC intervention.Conclusions. The non-antifungal agent NAC exhibits certain inhibitory effects on clinical isolate biofilm formation by down-regulating the expression of the CpEFG1 gene, making it a highly potential candidate for the treatment of C. parapsilosis catheter-related bloodstream infections.

Mitochondrial Protease Oct1p Regulates Mitochondrial Homeostasis and Influences Pathogenicity through Affecting Hyphal Growth and Biofilm Formation Activities in Candida albicans.

Mitochondria, as the core metabolic organelles, play a crucial role in aerobic respiration/biosynthesis in fungi. Numerous studies have demonstrated a close relationship between mitochondria and Candida albicans virulence and drug resistance. Here, we report an octapeptide-aminopeptidase located in the mitochondrial matrix named Oct1p. Its homolog in the model fungus Saccharomyces cerevisiae is one of the key proteins in maintaining mitochondrial respiration and protein stability. In this study, we utilized evolutionary tree analysis, gene knockout experiments, mitochondrial function detection, and other methods to demonstrate the impact of Oct1p on the mitochondrial function of C. albicans. Furthermore, through transcriptome analysis, real-time quantitative PCR, and morphological observation, we discovered that the absence of Oct1p results in functional abnormalities in C. albicans, affecting hyphal growth, cell adhesion, and biofilm formation. Finally, the in vivo results of the infection of Galleria mellonella larvae and vulvovaginal candidiasis in mice indicate that the loss of Oct1p led to the decreased virulence of C. albicans. In conclusion, this study provides a solid theoretical foundation for treating Candida diseases, developing new targeted drugs, and serves as a valuable reference for investigating the connection between mitochondria and virulence in other pathogenic fungi.

Phenotypic characterization for bioremediation suitability of isolates from Southern Tunisian tannery effluent

Effluents from the leather tanning industry contain diverse pollutants, including hazardous heavy metals, posing threats to public health and the surrounding environment. Indigenous bacterial isolates can represent an eco-friendly approach for tannery wastewater treatment; however, phenotypic characterization is necessary to determine whether these strains are suitable for bioremediation. In the present study, we analyzed seven new Enterococcus faecium strains and two new Bacillus subtillis strains isolated from effluents from the Southern Tunisian Tannery (ESTT). We evaluated phenotypic features beneficial for bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities. Additionally, we examined characteristics naturally occurring in environmental bacteria but less desirable in strains selected for bioremediation, such as antibiotic resistances and pathogenicity indicators. The observed phenotypes were then compared with whole-genome analysis. We observed biofilm production in two slime-producing bacteria, B. licheniformis RLT6, and E. faecium RLT8. Hydrophobicity of E. faecium strains RLT1, RLT5, RLT8, and RLT9, as well as B. licheniformis RLT6 correlated positively with increasing ESTT concentration. Exoenzyme activities were detected in E. faecium strains RLT2, RLT4, and RLT7, as well as B. licheniformis RLT6. As anticipated, all strains exhibited common resistances to antibiotics and hemolysis, which are widespread in nature and do not hinder their application for bioremediation. Importantly, none of the strains exhibited the pathogenic hypermucoviscosity phenotype. To the best of our knowledge, this is the first report consolidating all these phenotypic characteristics concurrently, providing a complete overview of strains suitability for bioremediation. ImportanceThe study evaluates the bioremediation potential of seven Enterococcus faecium strains and two Bacillus subtillis strains isolated from the effluents from the Southern Tunisian tannery (ESTT), which pose threats to public health and environmental integrity. The analysis primarily examines the phenotypic traits crucial to bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities, as well as characteristics naturally occurring in environmental bacteria related to heavy metal resistance, such as antibiotic resistances. Several strains were found to have high bioremediation potential and exhibit only antibiotic resistances commonly found in nature, ensuring their application for bioremediation remains uncompromised. The results of the exhaustive phenotypic analysis are contrasted with the whole genome sequences of the nine strains, underscoring the appropriateness of these bacterial strains for eco-friendly interventions in tannery wastewater treatment.

Synthesis and biological evaluation of new 2-Amino-7-hydroxy-8-methyl-4-aryl-4H-chromene-3-carbonitrile derivatives

A series of new 2-amino-7-hydroxy-8-methyl-4-aryl-4H-chromene-3-carbonitrile derivatives (4a-4g) have been synthesized by a one-pot multicomponent reaction of 2-methylresorcinol (1) and malononitrile (2) with various aldehydes (3). All the synthesised compounds (4a-4g) have been characterised using FT-IR, 1H NMR, 13C NMR, HR-MS and evaluated for swarming behaviour, biofilm formation, biofilm disruption and urease activity against P. mirabilis (MTCC-425). Among all the synthesized compounds, compounds 4a, 4b and 4g showed slightly inhibited swarming behaviour and compounds 4f and 4g inhibited biofilm formation with increasing concentration. SEM (Scanning Electron Microscope) imaging shows that compound 4e effectively disrupts the preformed biofilm. Also, compounds 4d and 4e showed 40% reduction in urease activity. The SAR studies of synthesized compounds are elaborated in detail to provide key structural features. Furthermore, molecular docking studies against urease could provide a mechanistic basis for the inhibition. The per-residue interaction analysis suggested the involvement of non-bonded and bonded interactions with the active site of urease. Hence, the aim of the below study was to synthesize new chromene derivatives and study their biological activities.

Screening of a potential probiotic Lactiplantibacillus plantarum NUC08 and its synergistic effects with yogurt starter

This study aims to identify lactic acid bacteria (LAB) isolates possessing physiological characteristics suitable for use as probiotics in yogurt fermentation. Following acid and bile salt tolerance tests, Lactiplantibacillus plantarum (NUC08 and NUC101), Lacticaseibacillus rhamnosus (NUC55 and NUC201), and Lacticaseibacillus paracasei (NUC159, NUC216 and NUC351) were shortlisted based on intraspecies distribution for further evaluation. Their physiological probiotic properties, including transit tolerance, adhesion, auto-aggregation, surface hydrophobicity, biofilm formation, and antibacterial activity, were assessed. Principal Component Analysis (PCA) indicated that L. plantarum NUC08 was the preferred choice among the evaluated strains. Subsequent investigations revealed that co-culturing L. plantarum NUC08 with 2 yogurt starter strains resulted in a cooperative and synergistic effect, enhancing the growth of mixed strains and increasing their tolerance to simulated gastric and intestinal conditions. Additionally, when Vibrio harveyi bioluminescent reporter strain was used, the 3 cocultured strains cooperated to induce the activity of a quorum sensing (QS) molecule AI-2, hinting a potential connection between phenotypic traits and QS in the cocultured strains. Importantly, LAB viable counts were significantly higher in yogurt co-fermented with L. plantarum NUC08, consistently throughout the storage period. In conclusion, the study demonstrates that the probiotic strain L. plantarum NUC08 can be employed in synergy with yogurt starter strains, affirming its potential for use in the development of functional fermented dairy products.

Isolation and Purification Glycyrrhizic acid and Determination of the Biological Activate Against Microbial Pathogens

Background: The World Health Organization estimates that 80% of the world's population uses plant extracts or their active components in traditional therapies. Recently, there has been a lot of interest in the quest for new antioxidant and antibacterial plant-based medications. Additionally, Glycyrrhiza glabra is a popular food flavoring and sweetening ingredient.Methods: This work was to isolate and purify licorice root's glycyrrhizin acid (GA) and investigate its antimicrobial properties against S. aureus and K. pneumoniae were isolated from urine , blood, wounds, ear water, sewage, soil, and water, totaling 12 isolates of each kind, Analytical method for the measurement of Glycyrrhizic acid from the root extract that has been suitably supported by a mass spectroscopic analysis.Results: The result showed the effects of GA with different concentrations on S. aureus and. K. pneumoniae. Obviously, the MIC range value was in concentration between 18.75 to 37.5 % for S. aureus isolates, and 4.68 to 75 for K. pneumoniae isolates. The result indicated that GA reduced the metabolic activity of cells in biofilm on S. aureus and K. pneumoniae with an inhibition percentageConclusion: GA may have an effect on cell membrane permeability, biofilm formation, and efflux activity, which inhibits bacterial growth.Keywords: Glycyrrhizin acid; Staphylococcus aureus; Klebsiella pneumoniae; Antibiotic; Biofilm