Effects of Pseudomonas aeruginosa on EH40 steel corrosion in the simulated tidal zone

Targeted Delivery of 2D Composite Minerals for Biofilm Removal

Microbiologically influenced corrosion (MIC) poses considerable challenges in various industries, prompting the exploration of advanced materials to mitigate microbial threats. This study successfully synthesized nanoscale vermiculite (VMT) from natural seawater and utilized it as a foundation to integrate magnetic nanoparticles (Fe3O4) and chlorhexidine acetate (CA) for inhibiting MIC. A comprehensive investigation encompassing the synthesis, characterization, and application of these VMT/Fe3O4/CA composites was conducted to evaluate their antimicrobial effectiveness against Escherichia coli, Staphylococcus aureus, and sulfate-reducing bacteria (SRB), demonstrating an efficacy exceeding 99.5%. Moreover, the composite material demonstrated the capability to align with a magnetic field, enabling precise drug targeting and release, thereby facilitating biofilm removal. This research makes a significant contribution to the advancement of intelligent, efficient, and eco-friendly corrosion protection solutions.

Effect of Halomonas titanicae on fluctuating water-line corrosion of EH40 steel

The fluctuating water-line corrosion of EH40 steel in sterile and biotic media was investigated with a wire beam electrode. When the coupons were partially immersed in the sterile medium, the position of the low water-line acted as the cathodic zone and the area below the low water-line constantly served as the main anodic zone. The thin electrolyte layers with uneven thickness promoted the galvanic current of the region below the low water-line. Different from the sterile environment, the metabolism of Halomonas titanica with oxygen as the final electron acceptor reduced the dissolved oxygen concentration, which resulted in the position of the low water-line acting as the anodic zone.

Low efficiency of cathodic protection in marine tidal corrosion of X80 steel in the presence of Pseudomonas sp

Owing to the effects of seawater erosion, dry/wet cycles, dissolved oxygen and microorganisms, the corrosion of steel in marine tidal environments is a serious threat to the safe and stable operation of marine equipment and facilities. Among them, microbiologically influenced corrosion (MIC) of steel has received increasing attention. Cathodic protection (CP) is frequently used to control the corrosion of offshore steel structures. However, in the presence of microorganisms, implementation of CP and its specific effects remain controversial. In this study, the influence of Pseudomonas sp. on the CP efficiency of Zn sacrificial anodes (ZnSAs) during the tidal corrosion of X80 steel was studied. The results showed that CP efficiency exceeded 92% in an abiotic tidal environment. However, in the biotic tidal environment, Pseudomonas sp. significantly reduced the CP efficiency. Pseudomonas sp. and its biofilm promoted the corrosion of steel under CP, inhibited the formation of a complete calcareous deposit layer, which weakened the CP efficiency of ZnSA in the marine tidal environment.

Deciphering the potential role of quorum quenching in efficient aerobic denitrification driven by a synthetic microbial community

Low efficiency is one of the main challenges for the application of aerobic denitrification technology in wastewater treatment. To improve denitrification efficiency, a synthetic microbial community (SMC) composed of denitrifiers Acinetobacter baumannii N1 (AC), Pseudomonas aeruginosa N2 (PA) and Aeromonas hydrophila (AH) were constructed. The nitrate (NO3--N) reduction efficiency of the SMC reached 97 % with little nitrite (NO2--N) accumulation, compared to the single-culture systems and co-culture systems. In the SMC, AH proved to mainly contribute to NO3--N reduction with the assistance of AC, while PA exerted NO2--N reduction. AC and AH secreted N-hexanoyl-DL-homoserine lactone (C6-HSL) to promote the electron transfer from the quinone pool to nitrate reductase. The declined N-(3-oxododecanoyl)-L-homoserine lactone (3OC12-HSL), resulting from quorum quenching (QQ) by AH, stimulated the excretion of pyocyanin, which could improve the electron transfer from complex III to downstream denitrifying enzymes for NO2--N reduction. In addition, C6-HSL mainly secreted by PA led to the up-regulation of TCA cycle-related genes and provided sufficient energy (such as NADH and ATP) for aerobic denitrification. In conclusion, members of the SMC achieved efficient denitrification through the interactions between QQ, electron transfer, and energy metabolism induced by N-acyl-homoserine lactones (AHLs). This study provided a theoretical basis for the engineering application of synthetic microbiome to remove nitrate wastewater.

Long-term impact of nano zero-valent iron on methanogenic activity, microbial community structure, and transcription activity in anaerobic wastewater treatment system

Nano zero-valent iron (NZVI) is commonly used in industrial wastewater treatment. However, its long-term impact mechanisms of metabolization in anaerobic systems are not well understood. This study investigated the effects of long-term and continuous addition of NZVI on methanogenic activity, microbial community, and transcription activity. The results demonstrated that low levels of NZVI (1000 mg/L) induced inhibition of methanogenesis after 80 days, while high levels of NZVI (5000 mg/L) immediately led to a sharp decrease of cumulative methane production and chemical oxygen demand removal, which arrived at a steady state (14.4 % of control and 17 %) after 30 days. NZVI adversely affected cell viability, adenosine triphosphate production, and fatty acid evolution of cell membranes played a crucial role in resisting chronic NZVI toxicity. Moreover, high NZVI levels hindered the transcription of key enzymes CoM and mcrA, while low NZVI levels maintained its high CoM and mcrA activity, but down-regulated the transcription of cdh and hdr. Besides, amino-utilizing bacteria was reduced under the high NZVI concentration, while low NZVI changed dominant genus with potential protein hydrolysis function from Candidatus Cloacamonas to Sedimentibacter. These results provide a guideline for proper NZVI utilization in wastewater treatment.

Corrosion of Pseudomonas aeruginosa toward a Cu-Zn-Ni alloy inhibited by the simulative tidal region

The corrosion of marine engineering equipment not only threatens human security and ecological environment but also increases energy consumption, restricting the sustainable development of marine economies and industries. The tidal region is a complex and challenging environment that can cause severe corrosion of facilities and affect microbial activities. However, the current understanding of the mechanisms underlying microbiologically influenced corrosion (MIC) of tidal region is insufficient. To address this issue, the effect of Pseudomonas aeruginosa on a Cu-Zn-Ni alloy in the simulative tidal region was investigated by chemical and molecular biological analysis in this study. The results demonstrated that P. aeruginosa formed thicker biofilms on the Cu-Zn-Ni alloy samples under the full exposure, accelerating corrosion compared to sterile controls. Interestingly, the corrosion of P. aeruginosa toward the Cu-Zn-Ni alloy was inhibited in the simulative tidal region. This inhibition behavior was relevant to the reduction in the quantity of sessile cells and cell activities. The expression down-regulation of genes encoding phenazines induced the decrease in electron transfer mediators and weakened the MIC of P. aeruginosa on alloy samples in the simulative tidal region. The research sheds light on the characteristics of P. aeruginosa and corrosion products on the Cu-Zn-Ni alloy, as well as their interaction mechanisms underlying corrosion in the simulative tidal region. The study will facilitate the evaluation and control of MIC in the tidal region, contributing to the development of sustainable strategies for preserving the integrity and safety of marine facilities.