An anticorrosive study on potential bioactive compound produced by Pseudomonas aeruginosa TBH2 against the biocorrosive bacterial biofilm on copper metal

Transforming microbial pigment into therapeutic revelation: extraction and characterization of pyocyanin from Pseudomonas aeruginosa and its therapeutic potential as an antibacterial and anticancer agent

BACKGROUND

The objectives of the current study were to extract pyocyanin from Pseudomonas aeruginosa clinical isolates, characterize its chemical nature, and assess its biological activity against different bacteria and cancer cells. Due to its diverse bioactive properties, pyocyanin, being one of the virulence factors of P. aeruginosa, holds a promising, safe, and available therapeutic potential.

METHODS

30 clinical P. aeruginosa isolates were collected from different sources of infections and identified by routine methods, the VITEK 2 compact system, and 16 S rRNA. The phenazine-modifying genes (phzM, phzS) were identified using polymerase chain reaction (PCR). Pyocyanin chemical characterization included UV-Vis spectrophotometry, Fourier Transform Infra-Red spectroscopy (FTIR), Gas Chromatography-Mass Spectrometry (GC-MS), and Liquid Chromatography-Mass Spectrometry (LC-MS). The biological activity of pyocyanin was explored by determining the MIC values against different clinical bacterial strains and assessing its anticancer activity against A549, MDA-MB-231, and Caco-2 cancer cell lines using cytotoxicity, wound healing and colony forming assays.

RESULTS

All identified isolates harboured at least one of the phzM or phzS genes. The co-presence of both genes was demonstrated in 13 isolates. The UV-VIS absorbance peaks were maxima at 215, 265, 385, and 520 nm. FTIR could identify the characteristic pyocyanin functional groups, whereas both GC-MS and LC-MS elucidated the chemical formula C11H18N2O2, with a molecular weight 210. The quadri-technical analytical approaches confirmed the chemical nature of the extracted pyocyanin. The extract showed broad-spectrum antibacterial activity, with the greatest activity against Bacillus, Staphylococcus, and Streptococcus species (MICs 31.25-125 µg/mL), followed by E. coli isolates (MICs 250-1000 µg/mL). Regarding the anticancer activity, the pyocyanin extract showed IC50 values against A549, MDA-MB-231, and Caco-2 cancer cell lines of 130, 105, and 187.9 µg/mL, respectively. Furthermore, pyocyanin has markedly suppressed colony formation and migratory abilities in these cells.

CONCLUSIONS

The extracted pyocyanin has demonstrated to be a potentially effective candidate against various bacterial infections and cancers. Hence, the current findings could contribute to producing this natural compound easily through an affordable method. Nonetheless, future studies are required to investigate pyocyanin's effects in vivo and analyse the results of combining it with other traditional antibiotics or anticancer drugs.

Synthesis of silver nanoparticles from Indian red yeast rice and its inhibition of biofilm in copper metal in cooling water environment

The development of environmentally acceptable benign techniques using purely natural methods is a cost-effective procedure with long-term benefits in all areas. With this consideration, myco synthesized silver nano particles (AgNPs) were studied and it acted as an impending corrosion inhibitor in the environment. Initially, AgNPs were evaluated by physical and surface characterizations and this evidence demonstrated that RYRE's water-soluble molecules played an essential role in the synthesis of AgNPs in nano spherical size. The myco synthesized of AgNPs has showed an antibacterial activity against corrosive bacteria in cooling water system (CWS). Hence, the AgNPs were used in biocorrosion studies as an anticorrosive agent along with AgNO₃ and RYRE was also checked. For this experiment, the copper (Cu) metal (CW024) which is commonly used was selected, the result of corrosion rate was decreased, and inhibition efficiency (82%) was higher in the presence of AgNPs in system IV. Even though, AgNO₃ and RYRE had contributed significant inhibition efficiency on Cu at 47% and 61%, respectively. According to XRD, the reaction of AgNPs on Cu metal resulted in the formation of a protective coating of Fe₂O₃ against corrosion. EIS data also indicated that it could reduce the corrosion on the Cu metal surface. All of these findings point out the possibility that the myco-synthesized AgNPs were an effective copper metal corrosion inhibitor. As a result, we encourage the development of myco-synthesized AgNPs, which could be useful in the industrial settings.

Extracellular Electron Transfer by Pseudomonas aeruginosa in Biocorrosion: A Review

Microorganisms with extracellular electron transfer (EET) capability have gained significant attention for their different biotechnological applications, like biosensors, bioremediation, and microbial fuel cells. Current research affirmed that microbial EET potentially promotes corrosion of iron structures, termed microbiologically influenced corrosion (MIC). The sulfate-reducing (SRB) and nitrate-reducing (NRB) bacteria are the most investigated among the different MIC-promoting bacteria. Unlike extensively studied SRB corrosion, NRB corrosion has received less attention from researchers. Hence, this review focuses on EET by Pseudomonas aeruginosa, a pervasive bacterium competent for developing biofilms in marine habitats and oil pipelines. A comprehensive discussion on the fundamentals of EET mechanisms in MIC is provided first. After that, the review offers state-of-the-art insights into the latest research on the EET-assisted MIC by Pseudomonas aeruginosa. The role of electron transfer mediators has also been discussed to understand the mechanisms involved in a better way. This review will be beneficial to open up new opportunities for developing strategies for combating biocorrosion.

Biofilm formation on copper and its control by inhibitor/biocide in cooling water environment

The present study has successfully identified the nitrate reducing bacteria present in the cooling water system and also investigated the performance of industrially applied biocide and inhibitor on the bacterial inhibition. In order to carry out the objective of this study, facilities and methods such as 16S rRNA gene sequencing, Lowry assay, SEM, EIS, ICP-MS and weight loss analysis were being utilized. In this study, two out of the five morphologically dis- similar colonies identified through 16S rRNA gene sequencing, namely the Massilia timonae and the Pseudomonas, were being utilized in the biocorrosion study on copper metal. From the surface analysis using SEM demonstrated the phenomenon of biofilm formation on the copper surface. 2-methylbenzimidazole has the addition of methyl group in the diazole ring position of benzimidazole it has create basicity environment and inhibit the metal deterioration. Meanwhile, it is also deducible from the EIS and protein analysis that com- bination of biocide with either of the inhibitors gives rise to better biocorrosion suppression (0.00178 mpy and 0.00171mpy) as compared to the sole effect of either biocide or inhibitor (0.00219 mpy, 0.00162 and 0.00143). Biocorrosion system biocide with MBM was found to exhibit 65% corrosion inhibition efficiency. Moreover, adoption of 2-Methylbenzimidazole seems to display better performance as compared to Multionic 8151, which is adopted in cooling water system.

Microbial corrosion of metals: The corrosion microbiome

Microbially catalyzed corrosion of metals is a substantial economic concern. Aerobic microbes primarily enhance Fe⁰ oxidation through indirect mechanisms and their impact appears to be limited compared to anaerobic microbes. Several anaerobic mechanisms are known to accelerate Fe⁰ oxidation. Microbes can consume H₂ abiotically generated from the oxidation of Fe⁰. Microbial H₂ removal makes continued Fe⁰ oxidation more thermodynamically favorable. Extracellular hydrogenases further accelerate Fe⁰ oxidation. Organic electron shuttles such as flavins, phenazines, and possibly humic substances may replace H₂ as the electron carrier between Fe⁰ and cells. Direct Fe⁰-to-microbe electron transfer is also possible. Which of these anaerobic mechanisms predominates in model pure culture isolates is typically poorly documented because of a lack of functional genetic studies. Microbial mechanisms for Fe⁰ oxidation may also apply to some other metals. An ultimate goal of microbial metal corrosion research is to develop molecular tools to diagnose the occurrence, mechanisms, and rates of metal corrosion to guide the implementation of the most effective mitigation strategies. A systems biology approach that includes innovative isolation and characterization methods, as well as functional genomic investigations, will be required in order to identify the diagnostic features to be gleaned from meta-omic analysis of corroding materials. A better understanding of microbial metal corrosion mechanisms is expected to lead to new corrosion mitigation strategies. The understanding of the corrosion microbiome is clearly in its infancy, but interdisciplinary electrochemical, microbiological, and molecular tools are available to make rapid progress in this field.

Optimized Production of a Redox Metabolite (pyocyanin) by Pseudomonas aeruginosa NEJ01R Using a Maize By-Product

Pseudomonas aeruginosa metabolizes pyocyanin, a redox molecule related to diverse biological activities. Culture conditions for the production of pyocyanin in a defined medium were optimized using a statistical design and response surface methodology. The obtained conditions were replicated using as substrate an alkaline residual liquid of cooked maize and its by-products. The untreated effluent (raw nejayote, RN) was processed to obtain a fraction without insoluble solids (clarified fraction, CL), then separated by a 30 kDa membrane where two fractions, namely, retentate (RE) and filtered (FI), were obtained. Optimal conditions in the defined medium were 29.6 °C, 223.7 rpm and pH = 6.92, which produced 2.21 μg mL^-1 of pyocyanin, and by using the wastewater, it was possible to obtain 3.25 μg mL^-1 of pyocyanin in the retentate fraction at 40 h. The retentate fraction presented the highest concentration of total solids related to the maximum concentration of pyocyanin (PYO) obtained. The pyocyanin redox behavior was analyzed using electrochemical techniques. In this way, valorization of lime-cooked maize wastewater (nejayote) used as a substrate was demonstrated in the production of a value-added compound, such as pyocyanin, a redox metabolite of Pseudomonas aeruginosa NEJ01R.

Bacillus megaterium-induced biocorrosion on mild steel and the effect of Artemisia pallens methanolic extract as a natural corrosion inhibitor

Methanolic extract of Artemisia pallens (MEAP) (Asteraceae) was explored as greenbiocorrosion inhibitor for mild steel 1010 in 1.5% sodium chloride environment. Bacillus megaterium SKR7 induces the development of biofilm on the metal surface and forms the pitting corrosion. MEAP was showed (25 ppm) optimum inhibition effect of biocorrosion and further corrosion rate was highly reduced (0.3335 mm/year) than the control system (0.009 mm/year). The electrochemical study has supported the results with a higher value of total resistance (34 Ω cm²) when compared to control systems. It reveals the formation of a protective layer on the metal surface and reduces the adsorption of biofilm. This was due to the antimicrobial effect of MEAP. Overall, the results recognized that MEAP used as a green corrosion inhibitor for MS 1010 with 83% inhibition efficiency.

Impact and Role of Bacterial Communities on Biocorrosion of Metals Used in the Processing Industry

In the present study, the effects of the corrosive bacterial community and the biofilm on cooling water systems made from mild steel (MS) and brass (BR) were studied under field exposure conditions using electrochemical impedance spectroscopy measurements, scanning electron microscope, and X-ray diffraction methods. Results from16S rRNA gene sequences showed that the predominant bacteria species detected in the biofilm of MS and BR metals during 360 days of exposure were Bacillus cereus EN14, Achromobacter xylosoxidans EN15, A. xylosoxidans EN16, and B. cereus EN17. The weight loss results revealed that a higher corrosion rate was observed in MS (0.7 ± 0.1 mm/y) compared with that in BR (0.17 ± 0.05 mm/y) at the end of the exposure period. This can be explained by the bacterial communities enhancing the corrosion rates by creating a local corrosive environment. Scanning electron microscope images revealed the adsorption of biofilm on the MS and BR surfaces following180 days of exposure. From the electrochemical impedance study, a higher charge transfer resistance (R _ct) was obtained for BR (119.6 Ω cm²) when compared with that of MS (43.4 Ω cm²). This study explains the role of bacterial communities and their mechanisms in the corrosion of MS and BR in cooling water systems.