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Metal ions stress will inhibit the oxidation capacity of iron and sulfur of an acidophilic microbial consortium (AMC), which leads to reduced bioleaching efficiency. This work explored the impacts of Li + and Co 2+ on the composition and function of AMC biofilms with a multi-scale approach. At the reactor scale, the results indicated that the oxidative activity, the adsorption capacity, and the biofilm formation ability of AMC on pyrite surfaces decreased under 500 mM Li + and 500 mM Co 2+ . At the biofilm scale, the electrochemical measurements showed that Li + and Co 2+ inhibited the charge transfer between the pyrite working electrode and the biofilm, and decreased the corrosion current density of the pyrite working electrode. At the cell scale, the content of proteins in extracellular polymers substrate (EPS) increased as the concentrations of metal ions increased. Moreover, the adsorption capacity of EPS for Li + and Co 2+ increased. At the microbial consortium scale, a BugBase phenotype analysis showed that under 500 mM Li + and 500 mM Co 2+ , the antioxidant stress capacity and the content of mobile gene elements in AMC increased. The results in this work can provide useful data and theoretical support for the regulation strategy of the bioleaching of spent lithium-ion batteries to recover valuable metals., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Clostridioides difficile infection (CDI) with high morbidity and high mortality is an urgent threat to public health, and C. difficile pathogenesis studies are eagerly required for CDI therapy. The major surface layer protein, SlpA, was supposed to play a key role in C. difficile pathogenesis; however, a lack of isogenic slpA mutants has greatly hampered analysis of SlpA functions. In this study, the whole slpA gene was successfully deleted for the first time via CRISPR-Cas9 system. Deletion of slpA in C. difficile resulted in smaller, smother-edged colonies, shorter bacterial cell size, and aggregation in suspension. For life cycle, the mutant demonstrated lower growth (changes of optical density at 600 nm, OD600) but higher cell density (colony-forming unit, CFU), decreased toxins production, and inhibited sporulation. Moreover, the mutant was more impaired in motility, more sensitive to vancomycin and Triton X-100-induced autolysis, releasing more lactate dehydrogenase. In addition, SlpA deficiency led to robust biofilm formation but weak adhesion to human host cells.IMPORTANCE Clostridioides difficile infection (CDI) has been the most common hospital-acquired infection, with a high rate of antibiotic resistance and recurrence incidences, become a debilitating public health threat. It is urgently needed to study C. difficile pathogenesis for developing efficient strategies as CDI therapy. SlpA was indicated to play a key role in C. difficile pathogenesis. However, analysis of SlpA functions was hampered due to lack of isogenic slpA mutants. Surprisingly, the first slpA deletion C. difficile strain was generated in this study via CRISPR-Cas9, further negating the previous thought about slpA being essential. Results in this study will provide direct proof for roles of SlpA in C. difficile pathogenesis, which will facilitate future investigations for new targets as vaccines, new therapeutic agents, and intervention strategies in combating CDI., Competing Interests: The authors declare no conflict of interest.

Oceanic facilities and equipment corrosion present considerable economic and safety concerns, predominantly due to microbial corrosion. Early detection of corrosive microbes is pivotal for effective monitoring and prevention. Yet, traditional detection methods often lack specificity, require extensive processing time, and yield inaccurate results. Hence, the need for an efficient real-time corrosive microbe monitoring technology is evident. Pseudomonas aeruginosa, a widely distributed microorganism in aquatic environments, utilizes its production of quinone-like compounds, specifically pyocyanin (PYO), to corrode metals. Here, we report a novel fiber optic surface plasmon resonance (SPR) sensor modified by the C-terminal of BrlR protein (BrlR-C), which is a specific receptor of PYO molecule, to detect P. aeruginosa in aquatic environments. The results showed that the sensor had a good ability to recognize PYO in the concentration range of 0-1 μg/mL, and showed excellent sensing performance in real-time monitoring the growth status of P. aeruginosa. With a strong selectivity of PYO, the sensor could clearly detect P. aeruginosa against other bacteria in seawater environment, and exhibited excellent anti-interference ability against variations in pH, temperature and pressure and other interfering substances. This study provides a useful tool for monitoring corrosive P. aeruginosa biofilm in aquatic environments, which is a first of its kind example that serves as a laboratory model for the application of fiber optic technology in real-world scenarios to monitoring biofilms in microbial corrosion and biofouling., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Carbon steel microbiologically influenced corrosion (MIC) by sulfate reducing bacteria (SRB) is known to occur via extracellular electron transfer (EET). A higher biofilm sessile cell count leads to more electrons being harvested for sulfate reduction by SRB in energy production. Metal surface roughness can impact the severity of MIC by SRB because of varied biofilm attachment. C1018 carbon steel coupons (1.2 cm 2 top working surface) polished to 36 grit (4.06 μm roughness which is relatively rough) and 600 grit (0.13 μm) were incubated in enriched artificial seawater inoculated with highly corrosive Desulfovibrio ferrophilus IS5 at 28 ℃ for 7 d and 30 d. It was found that after 7 d of SRB incubation, 36 grit coupons had a 11% higher sessile cell count at (2.0 ± 0.17) × 10 8  cells/cm 2 , 52% higher weight loss at 22.4 ± 5.9 mg/cm 2 (1.48 ± 0.39 mm/a uniform corrosion rate), and 18% higher maximum pit depth at 53 μm compared with 600 grit coupons. However, after 30 d, the differences diminished. Electrochemical tests with transient information supported the weight loss data trends. This work suggests that a rougher surface facilitates initial biofilm establishment but provides no long-term advantage for increased biofilm growth., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Historically, biofilms have been perceived as problematic or detrimental. However, biofilms possess favorable traits such as self-regeneration, sustainability, scalability, and tunability, which make them candidates for diverse applications. Traditional applications of biofilms, such as environmental remediation, bioleaching, microbial fuel cells, and corrosion protection, are often built on the basis of wild-type or metabolically engineered strains. In this review, we further comment on the design strategies for multiple innovative applications of living functional biofilms. With the integration of signaling pathways, engineering of metabolic pathways and modification of extracellular polymeric substances, living functional biofilms have been constructed by researchers through various strategies. Functional biofilms for diverse applications, including catalysis, electric conduction, bioremediation, and medical therapy have been demonstrated in the literature. The mechanical properties of biofilms can be tuned through genetic editing, metal ion curing and synthetic gene circuits, etc. In addition, the improvement of 3D printing to use bioinks has also achieved significant progresses in fabricating living functional biofilms with specific structures. In the future, the combination of synthetic biology and techniques from other disciplines will lead to practical large-scale applications of biofilms., (Copyright © 2022 Elsevier Inc. All rights reserved.)

EET (extracellular electron transfer) is behind MIC (microbiologically influenced corrosion) of carbon steel by SRB (sulfate reducing bacteria). This work evaluated 20 ppm (w/w) riboflavin (an electron mediator) acceleration of C1018 carbon steel MIC by Desulfovibrio ferrophilus IS5 in enriched artificial seawater (EASW) after 7-d incubation in anaerobic vials at 28 °C. Twenty ppm riboflavin did not significantly change cell growth or alter the corrosion product varieties, but it led to 52% increase in weight loss and 105% increase in pit depth, compared to the control without 20 ppm riboflavin. With 20 ppm riboflavin supplement in EASW, D. ferrophilus yielded weight loss-based corrosion rate of 1.57 mm/y (61.8 mpy), and pit depth growth rate of 2.88 mm/y (113 mpy), highest reported for short-term pure-strain SRB MIC of carbon steel. Electrochemical tests in 450 mL glass cells indicated that the biofilm responded rather quickly to the riboflavin injection (20 ppm in broth) to the culture medium. Polarization resistance (R p ) began to decrease within minutes after injection. Within 2 h, the riboflavin injection led to 31% decrease in R p and 35% decrease in R ct  + R f from electrochemical impedance spectroscopy (EIS). The Tafel corrosion current density increased 63% 2 h after the injection., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Microbiologically influenced corrosion (MIC) is one of the major corrosion threats in the oil and gas industry. It is caused by environmental biofilms. Glutaraldehyde is a popular green biocide for mitigating biofilms and MIC. This work investigated the efficacy of glutaraldehyde enhancement by food-grade green chemical D-limonene in the biofilm prevention and MIC mitigation using a mixed-culture oilfield biofilm consortium. After 7 days of incubation at 37 °C in enriched artificial seawater in 125 mL anaerobic vials, the 100 ppm (w/w) glutaraldehyde + 200 ppm D-limonene combination treatment reduced the sessile cell counts on C1018 carbon steel coupons by 2.1-log, 1.7-log, and 2.3-log for sulfate reducing bacteria, acid producing bacteria, and general heterotrophic bacteria, respectively in comparison with the untreated control. The treatment achieved 68% weight loss reduction and 78% pit depth reduction. The 100 ppm glutaraldehyde + 200 ppm D-limonene combination treatment was found more effective in biofilm prevention and MIC mitigation than glutaraldehyde and D-limonene used individually. Electrochemical tests corroborated weight loss and pit depth data trends., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Biocorrosion first surfaced in the scientific literature when Richard H. Gaines associated corrosion with bacterial activities in 1910. It is also known as microbiologically influenced corrosion (MIC). In general, it covers two scenarios. One is that microbes cause corrosion directly, which usually means microbes secrete corrosive metabolites or microbes harvest electrons from a metal for respiration to produce energy. In the second scenario, microbes are behind the initiation or acceleration of corrosion caused by a pre-existing corrosive agent such as water and CO 2 , by compromising the passive film (often a metal oxide film on a metal). MIC is caused by microbial biofilms. It is everywhere around us. This work dissects some notable examples with perspectives., (© 2020 The Authors. Microbial Biotechnology published by Society for Applied Microbiology and John Wiley & Sons Ltd.)

The mitigation of microbiologically influenced corrosion (MIC) of 304L stainless steel (SS) against Pseudomonas aeruginosa by a Salvia officinalis extract was investigated using electrochemical and surface analysis techniques. The extract was characterized by HPLC-Q-TOF-MS and its antibiofilm property was evaluated. The data revealed the presence of well-known antimicrobial and anticorrosion compounds in the extract. The S. officinalis extract was found effective in preventing biofilm formation and inhibiting mature biofilm. Electrochemical results indicated that P. aeruginosa accelerated the MIC of 304L SS, while the extract was found to prevent the MIC with an inhibition efficiency of 97.5 ± 1.5%. This was attributed to the formation of a protective film by the adsorption of some compounds from the extract on the 304L SS surface., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Within the past 5 years, tremendous advances have been made to maximize the performance of microbial fuel cells (MFCs) for both "clean" bioenergy production and bioremediation. Most research efforts have focused on parameters including (i) optimizing reactor configuration, (ii) electrode construction, (iii) addition of redox-active, electron donating mediators, (iv) biofilm acclimation and feed nutrient adjustment, as well as (v) other parameters that contribute to enhanced MFC performance. To date, tremendous advances have been made, but further improvements are needed for MFCs to be economically practical. In this review, the diversity of electrogenic microorganisms and microbial community changes in mixed cultures are discussed. More importantly, different approaches including chemical/genetic modifications and gene regulation of exoelectrogens, synthetic biology approaches and bacterial community cooperation are reviewed. Advances in recent years in metagenomics and microbiomes have allowed researchers to improve bacterial electrogenicity of robust biofilms in MFCs using novel, unconventional approaches. Taken together, this review provides some important and timely information to researchers who are examining additional means to enhance power production of MFCs., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Electron transfer is a rate-limiting step in microbiologically influenced corrosion (MIC) caused by microbes that utilize extracellular electrons. Cross-cell wall electron transfer is necessary to transport the electrons released from extracellular iron oxidation into the cytoplasm of cells. Electron transfer mediators were found to accelerate the MIC caused by sulfate reducing bacteria. However, there is no publication in the literature showing the effect of electron transfer mediators on MIC caused by nitrate reducing bacteria (NRB). This work demonstrated that the corrosion of anaerobic Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was enhanced by two electron transfer mediators, riboflavin and flavin adenine dinucleotide (FAD) separately during a 7-day incubation period. The addition of either 10ppm (w/w) (26.6μM) riboflavin or 10ppm (12.7μM) FAD did not increase planktonic cell counts, but they increased the maximum pit depth on carbon steel coupons considerably from 17.5μm to 24.4μm and 25.0μm, respectively. Riboflavin and FAD also increased the specific weight loss of carbon steel from 2.06mg/cm 2 to 2.34mg/cm 2 and 2.61mg/cm 2 , respectively. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization curves all corroborated the pitting and weight loss data., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Pseudomonas aeruginosa (PA) is a ubiquitous microbe. It can form recalcitrant biofilms in clinical and industrial settings. PA biofilms cause infections in patients. They also cause biocorrosion of medical implants. In this work, D-tyrosine (D-tyr) was investigated as an antimicrobial enhancer for ciprofloxacin (CIP) against a wild-type PA biofilm (strain PAO1) on C1018 carbon steel in a strictly anaerobic condition. Seven-day biofilm prevention test results demonstrated that 2 ppm (w/w) D-tyr enhanced 30 ppm CIP by achieving extra 2-log sessile cell reduction compared with the 30 ppm CIP alone treatment. The cocktail of 30 ppm CIP + 2 ppm D-tyr achieved similar efficacy as the 80 ppm CIP alone treatment in the biofilm prevention test. Results also indicated that the enhanced antimicrobial treatment reduced weight loss and pitting corrosion. In the 3-hour biofilm removal test, the cocktail of 80 ppm CIP + 5 ppm D-tyr achieved extra 1.5-log reduction in sessile cell count compared with the 80 ppm CIP alone treatment. The cocktail of 80 ppm CIP + 5 ppm D-tyr achieved better efficacy than the 150 ppm CIP alone treatment in the biofilm removal test.

The present study investigated the antibacterial performance, corrosion resistance and surface properties of antibacterial austenitic 317L-Cu stainless steel (317L-Cu SS). After 4.5wt% copper was added to 317L stainless steel (317L SS), the new alloy underwent solid solution and aging heat treatment. Fluorescent staining using 4',6-diamidino-2-phenylindole (DAPI) revealed that the 317L-Cu SS showed strong antibacterial efficacy, achieving a 99% inhibition rate of sessile Staphylococcus aureus cells after 5days. The corrosion data obtained by potentiodynamic polarization curves indicated that in comparison with 317L SS, the pitting potential and corrosion current density of 317L-Cu slightly decreased due to the addition of Cu. The 317L-Cu SS exhibited no cytotoxicity against zebrafish (Danio rerio) embryos. The experimental results in this study demonstrated that the new alloy has potential applications in medical and daily uses., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Biocorrosion is also known as microbiologically influenced corrosion (MIC). Most anaerobic MIC cases can be classified into two major types. Type I MIC involves non-oxygen oxidants such as sulfate and nitrate that require biocatalysis for their reduction in the cytoplasm of microbes such as sulfate reducing bacteria (SRB) and nitrate reducing bacteria (NRB). This means that the extracellular electrons from the oxidation of metal such as iron must be transported across cell walls into the cytoplasm. Type II MIC involves oxidants such as protons that are secreted by microbes such as acid producing bacteria (APB). The biofilms in this case supply the locally high concentrations of oxidants that are corrosive without biocatalysis. This work describes a mechanistic model that is based on the biocatalytic cathodic sulfate reduction (BCSR) theory. The model utilizes charge transfer and mass transfer concepts to describe the SRB biocorrosion process. The model also includes a mechanism to describe APB attack based on the local acidic pH at a pit bottom. A pitting prediction software package has been created based on the mechanisms. It predicts long-term pitting rates and worst-case scenarios after calibration using SRB short-term pit depth data. Various parameters can be investigated through computer simulation., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Microbiologically Influenced Corrosion (MIC) is a serious problem in many industries because it causes huge economic losses. Due to its excellent resistance to chemical corrosion, 2707 hyper duplex stainless steel (2707 HDSS) has been used in the marine environment. However, its resistance to MIC was not experimentally proven. In this study, the MIC behavior of 2707 HDSS caused by the marine aerobe Pseudomonas aeruginosa was investigated. Electrochemical analyses demonstrated a positive shift in the corrosion potential and an increase in the corrosion current density in the presence of the P. aeruginosa biofilm in the 2216E medium. X-ray photoelectron spectroscopy (XPS) analysis results showed a decrease in Cr content on the coupon surface beneath the biofilm. The pit imaging analysis showed that the P. aeruginosa biofilm caused a largest pit depth of 0.69 μm in 14 days of incubation. Although this was quite small, it indicated that 2707 HDSS was not completely immune to MIC by the P. aeruginosa biofilm.

Carbon steels are widely used in the oil and gas industry from downhole tubing to transport trunk lines. Microbes form biofilms, some of which cause the so-called microbiologically influenced corrosion (MIC) of carbon steels. MIC by sulfate reducing bacteria (SRB) is often a leading cause in MIC failures. Electrogenic SRB sessile cells harvest extracellular electrons from elemental iron oxidation for energy production in their metabolism. A previous study suggested that electron mediators riboflavin and flavin adenine dinucleotide (FAD) both accelerated the MIC of 304 stainless steel by the Desulfovibrio vulgaris biofilm that is a corrosive SRB biofilm. Compared with stainless steels, carbon steels are usually far more prone to SRB attacks because SRB biofilms form much denser biofilms on carbon steel surfaces with a sessile cell density that is two orders of magnitude higher. In this work, C1018 carbon steel coupons were used in tests of MIC by D. vulgaris with and without an electron mediator. Experimental weight loss and pit depth data conclusively confirmed that both riboflavin and FAD were able to accelerate D. vulgaris attack against the carbon steel considerably. It has important implications in MIC failure analysis and MIC mitigation in the oil and gas industry.

The microbiologically influenced corrosion (MIC) resistance of a novel Cu-bearing 2205 duplex stainless steel (2205 Cu-DSS) against an aerobic marine Pseudomonas aeruginosa biofilm was investigated. The electrochemical test results showed that Rp increased and icorr decreased sharply after long-term immersion in the inoculation medium, suggesting that 2205 Cu-DSS possessed excellent MIC resistance to the P. aeruginosa biofilm. Fluorescence microscope images showed that 2205 Cu-DSS possessed a strong antibacterial ability, and its antibacterial efficiency after one and seven days was 7.75% and 96.92%, respectively. The pit morphology comparison after 14 days between 2205 DSS and 2205 Cu-DSS demonstrated that the latter showed a considerably reduced maximum MIC pit depth compared with the former (1.44 μm vs 9.50 μm). The experimental results suggest that inhibition of the biofilm was caused by the copper ions released from the 2205 Cu-DSS, leading to its effective mitigation of MIC by P. aeruginosa.

Engineering living functional biofilms offers an ecofriendly and efficient technique for the corrosion protection of metallic materials in marine environments. Its firm attachment to the metal surface is a key step to effectively improve the corrosion protection. Herein, engineered Escherichia coli biofilm with strong metal binding ability is constructed by genetically appending a metal binding domain (MBD) to extracellular amyloids. The engineered living biofilm improved the corrosion resistance of X70 carbon steel. Moreover, a biofilm‐induced mineralization layer, mainly composed of calcite, is formed on the X70 surface, which provided a stable corrosion barrier. At the end of 7‐days immersion, the icorr decreased from 5.1 ± 0.4 µA cm−2 without biofilm to 0.5 ± 0.1 µA cm−2 with E. coli MBD biofilm, resulting in a corrosion inhibition efficiency of 90.2%. It also demonstrated the corrosion protection effect for 304 stainless steel, suggesting possible broad applications of the engineered biofilm. The application of synthetic biology offers a novel approach in the development of anti‐corrosion technologies in water environments. [ABSTRACT FROM AUTHOR]

Corrosion of X80 pipeline steel under sulfate-reducing bacterium (SRB) biofilms, which formed in a culture medium at different times, in a simulated CO 2 -saturated oilfield produced water was investigated. Both planktonic and sessile SRB cells survived after 21 days of immersion in the water under carbon source starvation. The biofilms pre-cultured with a longer time increased the corrosion rate of the steel. At 37 °C, it took about 4 days for SRB to grow and then participate in the steel corrosion. The SRB also facilitated localized corrosion. The SRB biofilm, once deactivated, would no longer affect the steel corrosion. [ABSTRACT FROM AUTHOR]

Abstract: The study of microbiologically influenced corrosion (MIC) has long been plagued by a lack of clear understanding of MIC mechanisms. In this work, bioenergetics was used to explain why and when sulfate-reducing bacteria (SRB) became aggressive toward carbon steel. Fe2+/Fe0 and acetate + (lactate) have similar reduction potentials at pH 7 (−447 mV vs. −430 mV). Bioenergetically, Fe0 oxidation releases more energy than lactate oxidation, but Fe0 cannot provide organic carbons needed for growth. If there is insufficient carbon source that can diffuse from the bulk fluid to an iron surface, sessile cells at the bottom of an SRB biofilm on the surface may suffer from local carbon source starvation. In this work, mature Desulfovibrio vulgaris (ATCC 7757) biofilms initially grown in ATCC 1249 culture medium on C1018 carbon steel coupons were subjected to starvation by switching to fresh culture media with 0% (control), 90%, 99% and 100% less organic carbon, respectively. It was found that 90% and 99% carbon reductions increased weight loss significantly. Experimental data also showed that 90% carbon reduction caused a 10 μm maximum pit depth, largest among all other cases, while 99% carbon reduction yielded the highest specific weight loss of 0.0019 g/cm2. [Copyright &y& Elsevier]

Stress corrosion cracking (SCC) is a serious problem threatening structural integrity and safety. Metal corrosion pits can develop into more harmful cracks under mechanical stress. It is known in abiotic corrosion that fast corrosion does not necessarily cause more severe SCC. This is because fast corrosion can prevent or dissolve crack tips and convert them into less harmful pits if the uniform corrosion rate is fast enough. This work experimentally proved the hypothesis that the same phenomenon occurs in biotic corrosion. It was found that a highly corrosive SRB (sulfate reducing bacterium) strain, namely Desulfovibrio ferrophilus (strain IS5), caused fast uniform corrosion and dull pits, but no SCC cracks against X80 carbon steel U-bend coupons (stressed). In comparison, Desulfovibrio vulgaris , a far less corrosive SRB strain caused less corrosion, but generated sharp pits and SCC cracks in a 3-month lab test. This work also revealed that the X80 U-bend had a 44% higher sessile cell count and 34% higher weight loss after a 14-d D. ferrophilus incubation in deoxygenated enriched artificial seawater culture medium at 28 °C when compared with the (flat) square coupons (no stress). This weight loss trend was corroborated by transient electrochemical measurements. [Display omitted] [ABSTRACT FROM AUTHOR]

Desulfovibrio ferrophilus (IS5) corrosion of X65 carbon steel was impacted by gravity. Six o'clock position (6P) had the highest sessile count due to gravity assisting planktonic cell settling in early biofilm formation, leading to most severe static corrosion followed by 9P and 12P. The 7-d weight loss at 6P was 49.6 ± 4.4 mg/cm2 (3.3 mm/a in uniform corrosion rate) followed by 9P with 35.7 ± 2.6 mg/cm2 (2.4 mm/a) and 12P with 20.5 ± 5.5 mg/cm2 (1.4 mm/a). The trend was supported by electrochemical measurements. The weight loss differences reduced considerably when there was agitation, supporting the gravity hypothesis. • Early SRB biofilm growth is impacted by gravity, favoring 6 o'clock position (6P). • The biofilm sessile cell count sequence is 6P > 9P (side way) >12P (face down). • Weight loss and pit depth sequences after 7-day SRB incubation are 6P > 9P > 12P. • 6P has a uniform corrosion rate of 3.3 mm/a vs. 1.4 mm/a for 12P for 7-d incubation. • Agitation lowered weight loss differences, supporting gravity impact hypothesis. [ABSTRACT FROM AUTHOR]

Abstract: Generally speaking, a much higher concentration of biocide is needed to treat biofilms compared to the dosage used to for planktonic bacteria. With increasing restrictions of environmental regulations and safety concerns on large-scale biocide uses such as oil field applications, it is highly desirable to make more effective use of biocides. In this paper a green biocide enhancer ethylenediaminedisuccinate (EDDS) that is a biodegradable chelator, was found to enhance the efficacy of glutaraldehyde in its treatment of sulfate-reducing bacteria (SRB) biofilms. Experiments were carried out in 100 ml anaerobic vials with carbon steel coupons. The ATCC 14563 strain of Desulfovibrio desulfuricans was used. Biofilms on coupon surfaces were visualized using scanning electron microscopy (SEM). Experimental results showed that EDDS reduced the glutaraldehyde dosages considerably in the inhibition of SRB biofilm establishment and the treatment of established biofilms on carbon steel coupon surfaces. [Copyright &y& Elsevier]

Abstract In nature, microbes tend to form synergistic biofilms on a wide range of materials using extracellular polymeric substances to embed sessile cells. Problematic biofilms provide environments conducive to the occurrence of microbiologically influenced corrosion (MIC) in many industries. MIC includes corrosion caused by microbes as well as corrosion by another pre-existing corrosion agent that is accelerated by microbes. There are several distinct types of MIC mechanisms associated with different microbial species and metabolism types. Biofilms employ different defense mechanisms to protect themselves from environmental hazards. This makes sessile cells in biofilms much more resistant to treatment than planktonic cells. Biofilms are often treated with biocides together with physical scrubbing. Various approaches have been developed to boost biocide efficacy. New emerging technologies such as bacterial phages, quorum sensing inhibitors, and special chemicals to enhance biocides have been proposed in recent years. This review evaluates these different treatment methods and various techniques used to assess biocide treatment outcome including microbiology, molecular biology, corrosion testing and electrochemical methods. Highlights • Biofilms cause microbiologically influenced corrosion (MIC) and biofouling. • Some microorganisms cause MIC via extracellular electron transfer to get energy. • Some microorganisms secrete corrosive metabolites that lead to MIC. • Biocide enhancers and other new technologies help mitigate biofilms. • Electrochemical methods can be used to study MIC and to assess biocide efficacy. [ABSTRACT FROM AUTHOR]

In this work, microbial corrosion behavior of Ti-6Al-4V (TC4) alloy caused by electroactive Desulfovibrio ferrophilu s biofilm in enriched artificial seawater containing soluble electron shuttle was investigated. The addition of riboflavin-shuttle did not significantly change the planktonic and sessile cell counts but accelerated the microbiologically influenced corrosion of TC4 alloy. The Hilbert-Huang transform revealed the evolution of corrosion pits and the maximum pit depth enhanced with the increase of electron shuttle concentration. Electrochemical measurements proved that riboflavin-shuttle decreased the shuttled electron barrier and increased the anodic dissolution rate. Phase, organization and grain size of alloy were influenced by the MIC. • Ti-6Al-4 V (TC4) is not immune to Desulfovibrio ferrophilus. • Electron shuttle advances the transition of TC4 corrosion pits from metastable to stable state. • Rapid response of D. ferrophilus biofilms to riboflavin shuttle injection. • SRB-MIC decreases the α phase of the alloy. [ABSTRACT FROM AUTHOR]

In industrial and clinical settings, microbiologically influenced corrosion (MIC), also known as biocorrosion, is a major problem associated with materials degradation and infection. To mitigate biofilms, a Cu-bearing 2205 duplex stainless steel (2205-Cu DSS) was created by researchers to utilize the antimicrobial ability of copper. In this study, nitrate reducing Pseudomonas aeruginosa biofilm was grown as a nitrate reducing bacterium to investigate the antimicrobial efficacy and the MIC inhibition efficacy of 2205-Cu DSS under anaerobic condition. The results showed that both biofilm sessile cell count and electrochemically-measured corrosion rate were reduced compared with the 2205 duplex stainless steel (2205 DSS) control. [ABSTRACT FROM AUTHOR]

Microbiologically influenced corrosion (MIC) in the marine environment is a serious threat to the service life of marine materials. MIC pitting corrosion rate is usually much faster than the general corrosion process. The 2304 duplex stainless steel (DSS) is an excellent alternative to 316L SS in marine applications, while its MIC behavior is barely known. In this work, surface analysis and electrochemical techniques were used to study the corrosion behavior of 2304 DSS caused by the ubiquitous marine aerobe Pseudomonas aeruginosa . Compared with the abiotic control, the largest pit depth showed that the P. aeruginosa biofilm greatly accelerated the pitting corrosion (11.0 μm vs. 4.8 μm for the abiotic control). The presence of P. aeruginosa biofilm oxidized the passive film of 2304 DSS from Cr 2 O 3 to CrO 3 , which was a water-soluble compound, resulting in the decrease of the relative Cr content and destruction of the passive film. The linear polarization resistance (LPR), electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and polarization curve analyses all demonstrated that 2304 DSS was susceptible to MIC. [ABSTRACT FROM AUTHOR]

The role of biogenic H 2 S in the microbiologically influenced corrosion (MIC) of carbon steel was investigated. Desulfovibrio vulgaris (ATCC 7757), a sulfate reducing bacterium, was tested against C1018 carbon steel in anaerobic vials with three different sizes, each filled with 40 mL of ATCC 1249 culture medium, providing headspace volumes of 10 mL, 85 mL and 160 mL, respectively for H 2 S to escape. Results showed that a larger headspace led to a lower H 2 S concentration in the culture medium, and this increased the sessile cell count and made the iron sulfide film thinner, resulting in increased MIC. [ABSTRACT FROM AUTHOR]

Microbiologically influenced corrosion (MIC) is prevalent in the oil and gas industry. Problematic biofilms cause MIC and reservoir souring. A high biocide concentration is usually required to mitigate biofilms compared with planktonic cells. This causes economic and environmental concerns. A biocide enhancer can make a biocide more effective using the same or lower biocide dosage. In this work, an equimolar mixture of 100 ppm (w/w) of four D-amino acids (D-methionine, D-tyrosine, D-tryptophan, and D-leucine) labeled as D-mix enhanced 100 ppm tetrakis (hydroxymethyl) phosphonium sulfate (THPS) against a field biofilm consortium on C1018 carbon steel coupons. In order to test chemical compatibilities, D-amino acids were added together with THPS and enhanced oil recovery chemicals (a polymer, a surfactant, a corrosion inhibitor, and a scale inhibitor) to treat the mature biofilm consortium. After a 7-day biofilm removal test in 125 ml anaerobic vials, the cocktail of 100 ppm THPS +100 ppm D-mix achieved extra logs of reduction in sessile cell counts compared with the 100 ppm THPS alone treatment. The combination also achieved lower weight loss and smaller maximum pit depths. Electrochemical tests corroborated the weight loss and pitting data. [ABSTRACT FROM AUTHOR]

This work showed that a wild-type Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was more corrosive under organic carbon source starvation. P. aeruginosa biofilms were pre-grown for 2 days to achieve maturity before the culture media were changed to fresh culture media with 100% (as in the standard medium), 10%, and 0% organic carbons for subsequent 7-day incubation. Biofilms with 100%, 10%, and 0% organic carbons caused maximum pit depths of 5.4 μm, 10.6 μm, and 17.0 μm, respectively. Weight loss, linear polarization resistance and electrochemical impedance spectroscopy data corroborated the pitting data. [ABSTRACT FROM AUTHOR]

Different electrochemical techniques and surface analysis methods were used to continuously monitor the corrosion of 2205 duplex stainless steel (DSS) in P. aeruginosa inoculated medium. It was found that linear polarization resistance and electrochemical impedance spectroscopy, significantly inhibited the attachment and growth of the biofilm, due to an internal electric field, leading to lower corrosion rates. In comparison, electrochemical noise as a passive electrochemical measurement technique did not adversely impact the biofilm, and the corrosion rate and the largest pit depth distribution from electrochemical noise were the closest to those from weight-loss data, making it a more suitable technique to monitor MIC by fragile biofilms. [ABSTRACT FROM AUTHOR]

d -tyrosine and d -methionine that are naturally occurring chemicals were investigated as enhancers for alkyldimethylbenzylammonium chloride (ADBAC) against the Desulfovibrio vulgaris biofilm on C1018 coupons surfaces in ATCC 1249 culture medium. The 7-day biofilm prevention results showed that the d -amino acids alone had only limited effects on SRB sessile cell counts. Ten ppm (w/w) ADBAC alone achieved a 1-log reduction in SRB sessile cell count compared with the untreated control. The combination of 1 ppm d -tyrosine + 10 ppm ADBAC achieved 3 extra log reduction and 50 ppm d -methionine + 10 ppm ADBAC achieved 2 extra log reduction compared with the 10 ppm ADBAC alone treatment. In the biofilm removal test, both combinations exhibited 2 extra log reduction compared with the 10 ppm ADBAC alone treatment. These results were supported by scanning electron microscope images and confocal laser scanning microscope images of the biofilms. [ABSTRACT FROM AUTHOR]

Marine microbiologically influenced corrosion (MMIC), initiated or promoted by biofilms of marine microorganisms, is becoming a leading cause of marine materials destruction, resulting in economic losses of billions of dollars each year. Copper ions released from the surface of an alloy can efficiently inhibit the attachment and the growth of some biofilm bacteria. The current study showed that the a novel copper-bearing 2205 duplex stainless steel (2205-Cu DSS) was effective against Pseudomonas aeruginosa in artificial seawater, achieving reductions of colony-forming units of 33.1%, 56.0% and 70.3% after incubation for 1, 3, and 5 days, respectively. More importantly, 2205-Cu DSS significantly decreased the thickness of the biofilm and induced cell death as compared to the 2205 DSS control. These results collectively suggest that 2205-Cu DSS may effectively mitigate the corrosive P. aeruginosa biofilm in applications as a potential anti-MMIC material in the marine environment. [ABSTRACT FROM AUTHOR]

In the microbiologically influenced corrosion (MIC) caused by sulfate reducing bacteria (SRB), iron oxidation happens outside sessile cells while the utilization of the electrons released by the oxidation process for sulfate reduction occurs in the SRB cytoplasm. Thus, cross-cell wall electron transfer is needed. It can only be achieved by electrogenic biofilms. This work hypothesized that the electron transfer is a bottleneck in MIC by SRB. To prove this, MIC tests were carried out using 304 stainless steel coupons covered with the Desulfovibrio vulgaris (ATCC 7757) biofilm in the ATCC 1249 medium. It was found that both riboflavin and flavin adenine dinucleotide (FAD), two common electron mediators that enhance electron transfer, accelerated pitting corrosion and weight loss on the coupons when 10 ppm (w/w) of either of them was added to the culture medium in 7-day anaerobic lab tests. This finding has important implications in MIC forensics and biofilm synergy in MIC that causes billions of dollars of damages to the US industry each year. [ABSTRACT FROM AUTHOR]

The effects of magnetic fields (MFs)on the corrosion of 304 stainlesssteel (SS304) caused by oil-field sulfate-reducing bacteria (SRB)were investigated. Experimental data showed that the MF lowered thepopulation of planktonic SRB by almost 4 orders of magnitude and delayedthe formation of SRB biofilms on the SS304 coupons. The mass lossesand surface images of the coupons indicated that the application ofan MF considerably reduced the pitting corrosion of SS304. EDX andXPS analyses of the coupon surfaces demonstrated that the main corrosionproducts without an MF and with 2 and 4 mT MFs were FeS, FeO, andFe2O3, respectively. The application of MFscould be an environmentally friendly method for mitigating microbiologicallyinfluenced corrosion (MIC) on SS304. [ABSTRACT FROM AUTHOR]

Abstract: Nitrate injection is used to suppress reservoir souring in oil and gas fields caused by Sulfate Reducing Bacteria (SRB) through promotion of nitrate respiration by Nitrate Reducing Bacteria (NRB). However, it is not well publicized that nitrate reduction by NRB can cause Microbiologically Influenced Corrosion (MIC) because nitrate reduction coupled with iron oxidation is thermodynamically favorable. NRB benefits bioenergetically from this redox reaction under biocatalysis. This work showed that the Bacillus licheniformis biofilm, when grown as an NRB biofilm, caused a 14.5μm maximum pit depth and 0.89mg/cm2 normalized weight loss against C1018 carbon steel in one-week lab tests. [Copyright &y& Elsevier]

• A mixed-culture oilfield biofilm is grown in enriched artificial seawater. • It attaches to 304 SS (stainless steel) slightly better than on 316 SS. • R p of 316 SS from LPR is two times of that of 304 SS during 14-day incubation. • i corr of 316 SS is ten times lower than that of 304 SS at the end 14-day incubation. • 316 SS is considerably more resistant to MIC by the oilfield biofilm than 304 SS. Stainless steel (SS) has wide applications in oilfields because of their outstanding corrosion resistance. However, SS is susceptible to localized MIC (microbiologically influenced corrosion). In this study, the MIC caused by an oilfield mixed-culture consortium (labelled as Consortium II) in enriched artificial seawater against commonly utilized 304 SS and 316 SS was evaluated. Sessile cell count results showed that Consortium II had better growth on 304 SS surface than on 316 SS with 79% more sulfate reducing bacteria (SRB) and 37% more acid producing bacteria (APB). Pitting corrosion was observed. The corrosion resistance (R p) from linear polarization resistance (LPR) of 316 SS was two times as much as that for 304 SS during the 14-day incubation, while the corrosion current density (i corr) of 304 SS was 101 higher than that for 316 SS (2.19 µA/cm2 vs. 0.19 µA/cm2) at the end of the incubation. These results suggested that 316 SS was considerably more resistant to MIC by the oilfield biofilm than 304 SS. [ABSTRACT FROM AUTHOR]