Quorum sensing signal production by sponge-associated bacteria isolated from the Red Sea, Egypt

Detectable quorum signaling molecule via PANI-metal oxides nanocomposites sensors

The detection of N-hexanoyl-l-homoserine lactone (C6-HSL), a crucial signal in Gram-negative bacterial communication, is essential for addressing microbiologically influenced corrosion (MIC) induced by sulfate-reducing bacteria (SRB) in oil and gas industries. Metal oxides (MOx) intercalated into conducting polymers (CPs) offer a promising sensing approach due to their effective detection of biological molecules such as C6-HSL. In this study, we synthesized and characterized two MOx/polyaniline-dodecyl benzene sulfonic acid (PANI-DBSA) nanocomposites, namely ZnO/PANI-DBSA and Fe2O3/PANI-DBSA. These nanocomposites were applied with 1% by-weight carbon paste over a carbon working electrode (WE) for qualitative and quantitative detection of C6-HSL through electrochemical analysis. The electrochemical impedance spectroscopy (EIS) confirmed the composites' capability to monitor C6-HSL produced by SRB-biofilm, with detection limits of 624 ppm for ZnO/PANI-DBSA and 441 ppm for Fe2O3/PANI-DBSA. Furthermore, calorimetric measurements validated the presence of SRB-biofilm, supporting the EIS analysis. The utilization of these MOx/CP nanocomposites offers a practical approach for detecting C6-HSL and monitoring SRB-biofilm formation, aiding in MIC management in oil and gas wells. The ZnO/PANI-DBSA-based sensor exhibited higher sensitivity towards C6-HSL compared to Fe2O3/PANI-DBSA, indicating its potential for enhanced detection capabilities in this context. Stability tests revealed ZnO/PANI-DBSA's superior stability over Fe2O3/PANI-DBSA, with both sensors retaining approximately 85-90% of their initial current after 1 month, demonstrating remarkable reproducibility and durability.

Chitosan-Aspirin Combination Inhibits Quorum-Sensing Synthases (lasI and rhlI) in Pseudomonas aeruginosa

BACKGROUND

Quorum sensing (QS) controls the virulence of P. aeruginosa. This study aims to determine the anti-QS activity of aspirin alone and in combination with chitosan to reach maximum inhibition. We tested ten virulent Pseudomonas aeruginosa (P. aeruginosa) isolates and screened for N-acyl homoserine lactone (AHL) production using Agrobacterium tumefaciens as a biosensor. P. aeruginosa isolates were treated with sub-minimum inhibitory concentrations (MICs) of aspirin and chitosan-aspirin. We used broth microdilution and checkerboard titration methods to determine the MICs and the synergistic effect of these two compounds, respectively. Real-time polymerase chain reaction (PCR) was used to estimate the anti-QS activity of the aspirin-chitosan combination on the expression of lasI and rhlI genes.

RESULTS

Aspirin decreased the motility and production of AHLs, pyocyanin, and biofilm. Chitosan potentiated the inhibitory effect of aspirin. The chitosan-aspirin combination inhibited lasI and rhlI gene expression in PAO1 (ATCC 15692) by 7.12- and 0.92-fold, respectively. In clinical isolates, the expression of lasI and rhlI was decreased by 1.76 × 102- and 1.63 × 104-fold, respectively. Molecular docking analysis revealed that aspirin could fit into the active sites of the QS synthases lasI and rhlI with a high binding affinity, causing conformational changes that resulted in their inhibition.

CONCLUSIONS

The chitosan-aspirin combination provides new insights into treating virulent and resistant P. aeruginosa.

In Vitro Antimicrobial Activity of Medicinal Plant Extracts against Some Bacterial Pathogens Isolated from Raw and Processed Meat

Background and aim: The poultry meat and its products are considered ideal media for bacterial growth and spoilage, as they are highly nutritive with a favorable pH. The food industry has focused its attention on a great diversity of plant species as food preservatives. The aim of this study was to investigate the presence of Staphylococcus aureus, Escherichia coli O157: H7, and Klebsiella pneumonia in food samples and to evaluate of the antibacterial activity of some medicinal plant extracts against these bacteria. Methods: Raw and processed meat samples (n = 60) were collected from abattoirs and local markets. S. aureus, E. coli O157: H7, and K. pneumonia were isolated, identified by phenotypic methods, and then confirmed by 16S rRNA gene sequencing. The antibacterial activity and spectrum of essential oils and spices powder of cumin, black seeds, cloves, cinnamon, and marjoram was determined against the isolated strains in this study by microbial count and well-diffusion techniques. Results: A total of 33 isolates have been identified as S. aureus, 30 isolates were identified as E. coli O157: H7, and 15 isolates were identified as K. pneumonia. S. aureus, E. coli O157: H7, and K. pneumonia could be detected in both fresh and processed food with higher prevalence in the processed meat. There was a significant decrease in microbial count in treated samples either with the spices powder or essential oils of the tested medicinal plants compared to control samples during storage time period. Furthermore, while the microbial count increased in the control samples, the microbial count decreased to reach zero in almost all treated samples with essential oils after 15 days of storage. Conclusion: S. aureus, E. coli O157: H7, and K. pneumonia are associated with food from animal sources, in either fresh or processed meat samples. The prevalence of them was higher in the processed meat than in fresh meat. The essential oils and spices powder of cumin, black seeds, cloves, cinnamon, and marjoram have an in vitro wide spectrum antibacterial activity with the highest antibacterial activity for the black seeds.

In-vitro Antimicrobial Activity of Essential Oils and Spices Powder of some Medicinal Plants Against Bacillus Species Isolated from Raw and Processed Meat

Background and Aim

Bacillus species are widely distributed microorganisms in nature that are responsible for outbreaks of food poisoning and a common cause of food spoilage. This study aimed to isolate and identify foodborne Bacillus species from meat and to determine the antimicrobial activities of commercial essential oils and spices powder extracted from certain medicinal plants.

Methods

Sixty meat samples were collected in Assiut city and subdivided into raw meat and processed meat. Bacillus spp were isolated and identified according to their cultural characters, biochemical reactions, serological typing, and 16S rRNA gene sequencing. The antibacterial activity of essential oils and spices powder was measured by using well-diffusion and microbial count techniques.

Results

The prevalence of Bacillus spp. in the examined raw meat samples and processed meat samples was 13.34%, and 26.67%, respectively. There was a marked decrease in the total Bacillus species count after treatment of minced beef with essential oils and spices powder compared to the untreated one. Black seed oil was the most potent antibacterial essential oil among the tested oils present in this study.

Conclusion

Essential oils and spices powder of certain medicinal plants (cumin: Cuminum cyminum, black seeds: Nigella sativa, cloves: Syzygium aromaicum, cinnamon: Cinnamomum zeylanicum, and Marjoram: Origanum majorana) have a potential in vitro antimicrobial activity against Bacillus spp. Furthermore, Nigella sativa oil exhibited the most potent antibacterial activity against Bacillus spp.

Anti-quorum sensing activity of some marine bacteria isolated from different marine resources in Egypt

OBJECTIVES

To screen for a variety of marine bacteria with anti-quorum sensing and anti-biofilm activities.

RESULTS

Among 188 bacterial isolates from water, sediment, and corals in the Red Sea region, approximately 35% (65 isolates) of the isolates displayed a significant degradation in the purple pigment of the bioreporter strain without affecting cell growth. The quorum quenching bacteria obtained from coral-associated bacteria were 66.2% out of the total isolates. The PCR amplification results revealed that the recorded Acyl Homoserine lactone (AHL) inhibition by 91% of the anti-QS marine bacteria was not due to lactonase activity. On the other hand, lactonase genes were recorded only in the remaining 9% (6 isolates) and those were belonging to genus Bacillus, Nocardiopsis, and Enterobacter based on 16S rRNA gene sequences. The results also showed that marine bacteria with anti-QS activity inhibited 67% of the biofilm formed by Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio alginolyticus. The computational profiling analysis confirmed the presence of the functional region in the detected genes.

CONCLUSION

Coral microbial communities are rich sources for pharmacologically important natural products with anti-quorum sensing and anti-biofilm activities.

Chitosan and chitosan-zinc oxide nanocomposite inhibit expression of LasI and RhlI genes and quorum sensing dependent virulence factors of Pseudomonas aeruginosa

The great ability of Pseudomonas aeruginosa to cause chronic infection is attributed to several virulence factors, biofilm formation, intrinsic and acquired resistance to many antibiotics. Anti-quorum sensing (QS) and anti-virulence therapy are promising alternatives to the existing antibiotic therapy. In this study, the effect of chitosan and the prepared chitosan-zinc oxide (CH/ZnO) nanocomposite on QS-dependent virulence factors and acyl homoserine lactone "AHL" production was studied. The chemical structure of the prepared CH/ZnO nanocomposite was characterized by FT-IR spectrum and XRD. The thermal stability and particle size were determined. Chitosan causes a significant decrease in AHL, biofilm, pyocyanin production and motility of P. aeruginosa. CH/ZnO nanocomposite augments the inhibitory activity of chitosan in both phenotypic and genotypic levels. Both chitosan and CH/ZnO nanocomposite downregulate the expression of LasI and RhlI genes using quantitative real-time PCR. The expression of RhlI gene in PAO1 is reduced by 1240 folds after treatment with CH/ZnO nanocomposite. The expression of LasI and RhlI genes in clinical isolates is reduced by 1778.07 and 627.29 folds upon treatment with CH/ZnO. These promising results may find a rescue in the battle of fighting P. aeruginosa by repressing its QS-dependent virulence factors.