Marine Bacteria Provide Lasting Anticorrosion Activity for Steel via Biofilm-Induced Mineralization

Marine steel protection based on biomineralization for sustainable development of coastal cities

Corrosion research, spanning over 150 years, remains critically important, particularly for addressing marine microbially induced corrosion on steel, which causes significant economic losses and safety risks. This study proposes a biomineralization method using marine urease-producing bacteria to protect steel. Urease-producing bacteria were enriched to promote biomineralization, and a seawater corrosion experiment was conducted to evaluate its efficacy. Results showed that biomineralization significantly reduced corrosion rates, especially with yeast extract enrichment, and decreased the abundance of sulfate-reducing bacteria and sulfur-oxidizing bacteria in biofilms. Functional gene analysis identified Thioalkalivibrio as a key indicator of sulfate reduction. The findings demonstrated that the formed biomineralized film acted as a protective layer to isolate the steel from the corrosive seawater, which contributed to the advancement of novel techniques for corrosion inhibition of marine steel to achieve long-term sustainability for ships and engineering structures.

A comprehensive review of recent advancements in microbial-induced mineralization: biosynthesis and mechanism, with potential implementation in various environmental, engineering, and medical sectors

Biomineralization has garnered profuse attention in multidisciplinary fields. Using this strategy, living things, including eukaryotes or prokaryotes, mediate the uptake of ions from the surrounding environment, followed by assembling and depositing them as greatly configured structures inside the organic matrix. The generated biominerals, including nanomaterials, possess outstanding hierarchical structures that exceed their chemically synthesized counterparts. Despite the significant progress achieved in microbial-mediated mineralization, several key knowledge gaps remain, including mechanisms controlling biomineralization pathways and the impact of environmental factors on mineral morphology, crystallinity, and stability. This review provides a comprehensive description of this biomineralization, which can be categorized into controlled, influenced, and induced biomineralization. Interestingly, we highlighted biologically-induced mineralization approaches, such as photosynthesis, methane oxidation, and nitrogen-based metabolic pathways, and identified various chemical interactions during mineral production following analytical chemistry. This review also extensively delineates updates on application of biominerals across all fields, commencing with the remediation of deleterious pollutants and biominerals exploited in industrial sectors, moving on to using them to reinforce soil, generate biocement for construction, and delving into their utilization in pharmaceutical applications to deliver drugs, repair teeth and bones, and combat cancer and pathogenic microorganisms. Moreover, the review outlines the drawbacks and adequate solutions for biomineralization, particularly CaCO₃-mediated processes, such as the generation of ammonium and nitrate during the CaCO₃ precipitation process and the relatively slow rate of microbial-mediated mineralization. Biomineralization inspired the fabrication of smart biomaterials, which combine biological advantages. Overall, this comprehensive review discusses updated research and highlights potential approaches to future studies.

Metallic Shipwrecks and Bacteria: A Love-Hate Relationship

For two centuries, metallic shipwrecks have been relics of the history of navigation, trade, and wars. They are also hotspots of marine biodiversity. The degradation of these shipwrecks not only threatens their environment through the release of polluting compounds, but also the reef ecosystems that have developed. Microorganisms are at the root of both degradation and reef-building, and their roles are still more hypothetical than validated. The aim of this review is to focus on the known or suggested relationships between bacteria and metallic shipwrecks and to identify issues that highlight the need for multidisciplinary studies to better understand the mechanisms at play in these ecosystems with the aim of protecting both the environment and these sites of underwater cultural and natural heritage.

Dual role of microorganisms in metal corrosion: a review of mechanisms of corrosion promotion and inhibition

The dual role of microorganisms in metal corrosion and corrosion inhibition reflects their complex biochemical interactions. In terms of corrosion, certain microorganisms accelerate metal oxidation by producing acidic metabolites or facilitating electrochemical processes, thereby causing damage to the material. Conversely, under specific conditions, they can form biofilms and/or biominerals that create protective layers, reducing the oxidation rate and delaying corrosion. This paper provides a comprehensive illustration of microbial corrosion promotion and inhibition, emphasizing the importance of key microorganisms involved in these corrosive processes. Microorganisms, including sulfate-reducing bacteria, nitrate-reducing bacteria, iron-oxidizing and iron-reducing bacteria and certain fungi, contribute to corrosion through their metabolic activities. Microbial corrosion mechanisms can be classified into extracellular electron transfer, microbial metabolism corrosion and the oxygen concentration cell theory. In contrast, microorganisms can effectively mitigate metal corrosion through a range of mechanisms including reduction of dissolved oxygen levels, secretion of antimicrobial substances, biological competition and biomineralization. Microbial corrosion and inhibition generally arise from multiple mechanisms working together, rather than a single cause. A deeper understanding of these mechanisms can provide a theoretical basis and practical guidance for the development of new anti-corrosion strategies.

Collaborative or competitive interactions between bacteria and methanogens on the biocorrosion of Q235A steel

Bio-corrosion of Fe (0) metals in the actual environments results from the combined action of multiple microbes rather than the single action of one type of microbe. Nevertheless, the interspecies interactions between the corrosive microorganism and co-existing microbes, as well as their effects on the bio-corrosion of Fe (0) metals, remain unclear, especially for the interspecies interactions between methanogens and co-existed bacteria in microbiota in the absence of sulfate. Herein, the interspecies interactions between methanogens and co-existed bacteria in three different kinds of methanogenic microbiota (Methanothrix, Methanospirillum, or Methanobacterium dominant) and their effects on methanogens-influenced corrosion of Q235A steel were investigated. The initial results showed that competitive interactions existed between Methanothrix/Methanospirllum and fermentative acetogenic bacteria (Clostridiaceae_1, Family_XI, Peptostreptococcaceae, Pirllulaceae, and Tannerellaceae), while collaborative interactions existed between Methanobacterium and acetate-oxidizing bacteria (Synergistaceae and Spirochaetaceae). Further analysis demonstrated that the competitive interactions obstructed the attachment of Methanothrix/Methanospirllum and promoted the formation of dense corrosion products layer on the steel surface, thereby inhibiting Methanothrix/Methanospirllum-influenced corrosion. Contrarily, the collaborative interactions promoted the attachment of Methanobacterium and the formation of porous and loose corrosion products layer on the steel surface, thereby promoting Methanobacterium-influenced corrosion. Ultimately, the corrosion rate of steel induced by the Methanobacterium dominant microbiota (0.216 ± 0.042 mm/y) was much higher than by the Methanothrix/Methanospirllum dominant microbiota (0.009-0.046 mm/y). This work provided new insights into the understanding of the effects of co-existed bacteria on the corrosion of Fe (0) metals induced by methanogens in microbiota.

Influence of calcium sources on the bio-mineralization behavior of Shewanella putrefaciens and induced microbiologically influenced corrosion inhibition

The influence of different calcium sources on the mineralization behavior of Shewanella putrefaciens and their roles in microbiologically influenced corrosion inhibition (MICI) of Q235 carbon steel were investigated. Calcium lactate, calcium nitrate, and calcium L-aspartate were selected as alternative calcium sources to assess their effects on bacterial growth, carbonate deposition, and corrosion resistance. S. putrefaciens exhibited stable growth in all tested media, with the pH exceeding 8 after 14 days, promoting carbonate precipitation. Under sterile conditions, all calcium sources provided some corrosion inhibition, with calcium L-aspartate demonstrating the most effective protection. In bacterial inoculated systems, calcium lactate and calcium L-aspartate facilitated the formation of a continuous CaCO3 mineralized layer, significantly reducing corrosion, whereas calcium nitrate resulted in discontinuous carbonate deposits, promoting localized corrosion. Electrochemical impedance spectroscopy and potentiodynamic polarization analyses confirmed that the mineralized layers formed with calcium lactate and calcium L-aspartate significantly enhanced corrosion resistance, while calcium nitrate exacerbated corrosion due to nitrate-reducing bacterial activity. These findings emphasize the crucial role of calcium source selection in MICI and provide insights for optimizing microbial mineralization strategies for corrosion mitigation.

A point mutation in a wspF-like gene in Pseudoalteromonas lipolytica enhances the anticorrosion activity

The protection of steel based on microbial biomineralization has emerged as a novel and eco-friendly strategy for corrosion control. However, the molecular basis of the biomineralization process in mineralization bacteria remains largely unexplored. We previously reported that Pseudoalteromonas lipolytica EPS+ strain provides protection against steel corrosion by forming a hybrid biomineralization film. In this study, we identified that a point mutation in the AT00_08765 (wspF-like) gene, responsible for encoding a chemotaxis protein that regulates swimming motility and polysaccharide production, is linked to the observed anticorrosion activity in EPS+ strain. The engineered point mutation mutant strain, designated Δ08765(707A), exhibited similar phenotypes to the EPS+ strain, including colony morphology and cellulose production. Importantly, we demonstrated that moderate swimming motility in Δ08765(707A) plays a pivotal role in the development of a protective mineralization film on the steel surface. Additionally, we found that Δ08765(707A) enhances biofilm formation by rapidly forming small aggregates in the initial stage of biofilm growth. This process facilitated the assembly of more compact and larger mineralization products, effectively inhibiting steel corrosion. In addition, Δ08765(707A) formed a uniform mineralization film that completely covered the steel surface, preventing the formation of sheet-like steel corrosion products. Therefore, this study demonstrates that an engineering strain carrying a point mutation in the AT00_08765 gene can significantly enhance the anticorrosion activity. This enhancement is accomplished through the formation of small bacteria-induced aggregates, followed by the development of larger mineralization products and the creation of a uniform organic-inorganic hybrid film.IMPORTANCEIn this study, we revealed that moderate swimming motility significantly influences the anticorrosion activity of marine Pseudoalteromonas. Furthermore, our study demonstrated that overproduction of cellulose facilitates cell aggregation rapidly during the initial stages of biofilm formation, thereby promoting the development of larger mineralization products and the formation of a uniform organic-inorganic hybrid film on the steel surface. Our findings provide new insights into the biomineralization mechanisms in Pseudoalteromonas lipolytica, potentially catalyzing the advancement of an eco-friendly microbial-driven approach to marine corrosion prevention.

Exploring Marine Biomineralization on the Al-Mg Alloy as a Natural Process for In Situ LDH Growth to Improve Corrosion Resistance

This study provides a detailed characterization of the AA5083 aluminum alloy, surface, and interface over 6 months of immersion in seawater, employing techniques such as SEM/EDX, GIXRD, μ-Raman and XPS. The purpose was to evaluate the evolution of the biomineralization process that occurs on the Al-Mg alloy. By investigating the specific conditions that favor the in situ growth of layered double hydroxide (LDH) during seawater immersion as a result of biomineralization, this research provides insights into marine biomineralization, highlighting its potential as an innovative and sustainable strategy for corrosion protection.

Microbiologically influenced corrosion inhibition of carbon steel by a novel bacterium, Photobacterium sp., in simulated marine environment

Utilizing microorganisms in corrosion inhibition presents a broad application prospect, but the complexity of their biological activities and living environments call for continued investigation and innovation. To uncover the corrosion behaviors and mechanisms effected by microorganisms, the effect of a novel strain named Photobacterium sp. 9-1 on the carbon steel corrosion process was investigated. Photobacterium sp. 9-1 was identified as a corrosion inhibition bacterium that could reduce the weight loss of carbon steel by approximately 97%. The biofilm formed on the metal surface, which was composed of bacteria, proteins, polysaccharides, etc., was a vital biological structure for the corrosion prevention. Further, we found that the corrosion inhibition effect induced by Photobacterium sp. 9-1 was dependent on the physiological activities of live bacteria. Thus, the discovery of efficient corrosion inhibition bacteria and further study of the relationship between the corrosion protection behavior of bacteria and metal materials could provide new insight into the design and application of economic and eco-friendly corrosion protection materials.

Passivation of metal sulfides by a marine bacterium for acid mine drainage control

Acid mine drainage originates from metal sulfides oxidation, which results in acidic metal-rich leachate. In this study, a novel and environmentally friendly approach was demonstrated to passivate pyrite and lead-zinc tailings, respectively. The key to this approach is to develop biofilms of the marine bacterium Qipengyuania flava S1. Biofilms can induce biomineralization, thereby isolating metal sulfides from air and water. The stability and biological toxicity of the bio-passivation layers were evaluated by leaching bio-passivated pyrite or tailings in initially acidic H2O2 solutions with shaking for 180 days and then cultivating Brassica chinensis and Allium cepa with the leachates. Our results showed that after passivation, the amount of iron released by pyrite decreased by at least 99.2 ± 0.2 (in wt%). For lead-zinc tailings after passivation, the released metal ions (Fe+Al+Pb+Zn) decreased by at least 52.0 ± 3.2 (in wt%). The bio-passivation layers also maintained the pH of the leachate in the range of 7.5-8.0. Before bio-passivation, compared with mineral water, the pyrite leachate significantly inhibited the growth of the two plants, and the tailings leachate significantly inhibited the growth of A. cepa, whereas the bio-passivated pyrite or tailings leachate did not show any inhibitory effect.

Insights into the biocorrosion of Q235A steel influenced by the electron transfer process between iron and methanogenic microbiota

Anaerobic microbiologically influenced corrosion (MIC) of Fe (0) metals causes great harm to the environment and economy, which depends on the key electron transfer process between anaerobic microorganisms and Fe (0) metals. However, the key electron transfer process in microbiota dominating MIC remains unclear, especially for methanogenic microbiota wildly distributed in the environment. Herein, three different methanogenic microbiota (Methanothrix, Methanospirillum, and Methanobacterium) were acclimated to systematically investigate electron transfer pathways on corroding Q235A steel coupons. Results indicated that microbiota dominated by Methanothrix, Methanospirillum, or Methanobacterium accelerated the steel corrosion mainly through direct electron transfer (DET) pathway, H2 mediated electron transfer (HMET) pathway, and combined DET and HMET pathways, respectively. Compared with Methanospirillum dominant microbiota, Methanothrix or Methanobacterium dominant microbiota caused more methane production, higher weight loss, corrosion pits with larger areas, higher corrosion depth, and smaller corrosion pits density. Such results reflected that the DET process between microbiota and Fe (0) metals decided the biocorrosion degree and behavior of Fe (0) metals. This study insightfully elucidates the mechanisms of methanogenic microbiota on corroding steels, in turn providing new insights for anti-corrosion motives.

Inhibitory effect of marine Bacillus sp. and its biomineralization on the corrosion of X65 steel in offshore oilfield produced water

The issue of material failure attributed to microbiologically influenced corrosion (MIC) is escalating in seriousness. Microorganisms not only facilitate corrosion but certain beneficial microorganisms also impede its occurrence. This study explored the impact of marine B. velezensis on the corrosion behavior of X65 steel in simulated offshore oilfield produced water. B. velezensis exhibited rapid growth in the initial stages, and the organic acid metabolites were found to promote corrosion. Subsequently, there was an increase in cross-linked "networked" biofilms products, a significant rise in the prismatic shape of corrosion products, and a tendency for continuous development in the middle and late stages. The organic/inorganic mineralized film layer formed on the surface remained consistently complete. Metabolic products of amino acid corrosion inhibitors were also observed to be adsorbed into the film. B. velezensis altered the kinetics of the X65 steel cathodic reaction, resulting in a deceleration of the electrochemical reaction rate. The mineralization induced by B. velezensis effectively slowed down the corrosion rate of X65 steel.

Harnessing active biofilm for microbial corrosion protection of carbon steel against Geobacter sulfurreducens

Microbiologically influenced corrosion (MIC) caused by corrosive microorganisms poses significant economic losses and safety hazards. Conventional corrosion prevention methods have limitations, so it is necessary to develop the eco-friendly and long-term effective strategies to mitigate MIC. This study investigated the inhibition of Vibrio sp. EF187016 biofilm on Geobacter sulfurreducens on carbon steel. Vibrio sp. EF187016 biofilm reduced the corrosion current density and impeded pitting corrosion. A thick and uniform Vibrio sp. EF187016 biofilm formed on the coupon surfaces, acting as a protective layer against corrosive ions and electron acquisition by G. sulfurreducens. The pre-grown mature Vibrio sp. EF187016 biofilms, provided enhanced protection against G. sulfurreducens corrosion. Additionally, the extracellular polymeric substances from Vibrio sp. EF187016 was confirmed to act as a green corrosion inhibitor to mitigate microbial corrosion. This study highlights the potential of active biofilms for eco-friendly corrosion protection, offering a novel perspective on material preservation against microbial corrosion.

Beneficial applications of biofilms

Many microorganisms live in the form of a biofilm. Although they are feared in the medical sector, biofilms that are composed of non-pathogenic organisms can be highly beneficial in many applications, including the production of bulk and fine chemicals. Biofilm systems are natural retentostats in which the biocatalysts can adapt and optimize their metabolism to different conditions over time. The adherent nature of biofilms allows them to be used in continuous systems in which the hydraulic retention time is much shorter than the doubling time of the biocatalysts. Moreover, the resilience of organisms growing in biofilms, together with the potential of uncoupling growth from catalytic activity, offers a wide range of opportunities. The ability to work with continuous systems using a potentially self-advancing whole-cell biocatalyst is attracting interest from a range of disciplines, from applied microbiology to materials science and from bioengineering to process engineering. The field of beneficial biofilms is rapidly evolving, with an increasing number of applications being explored, and the surge in demand for sustainable and biobased solutions and processes is accelerating advances in the field. This Review provides an overview of the research topics, challenges, applications and future directions in beneficial and applied biofilm research.

Biomineralization To Prevent Microbially Induced Corrosion on Concrete for Sustainable Marine Infrastructure

Microbially induced corrosion (MIC) on concrete represents a serious issue impairing the lifespan of coastal/marine infrastructure. However, currently developed concrete corrosion protection strategies have limitations in wide applications. Here, a biomineralization method was proposed to form a biomineralized film on concrete surfaces for corrosion inhibition. Laboratory seawater corrosion experiments were conducted under different conditions [e.g., chemical corrosion (CC), MIC, and biomineralization for corrosion inhibition]. A combination of chemical and mechanical property measurements of concrete (e.g., sulfate concentrations, permeability, mass, and strength) and a genotypic-based investigation of formed concrete biofilms was conducted to evaluate the effectiveness of the biomineralization approach on corrosion inhibition. The results show that MIC resulted in much higher corrosion rates than CC. However, the biomineralization treatment effectively inhibited corrosion because the biomineralized film decreased the total and relative abundance of sulfate-reducing bacteria (SRB) and acted as a protective layer to control the diffusion of sulfate and isolate the concrete from the corrosive SRB communities, which helps extend the lifespan of concrete structures. Moreover, this technique had no negative impact on the native marine microbial communities. Our study contributes to the potential application of biomineralization for corrosion inhibition to achieve long-term sustainability for major marine concrete structures.

Corrosion of Q235 carbon steel induced by sulfate-reducing bacteria in groundwater: corrosion behavior, corrosion product, and microbial community structure

Microbiologically influenced corrosion (MIC) is one of the reasons leading to the service failure of pipelines buried in the soil. In this work, the effect of sulfate-reducing bacteria (SRB) on the corrosion behavior of Q235 carbon steel in groundwater was investigated by electrochemical methods, surface analysis, and biological analysis. The results show that SRB utilizes iron as electron donor to sustain the vital activities of organic carbon-starved groundwater during the 14-day experimental period. The microbial community composition analysis at the genus level demonstrate that the diversity and richness decrease after corrosion, and the dominant SRB species has changed from Desulfovibrio to Desulfosporosinus. Moreover, the impedance of the carbon steel in the presence of biofilm was 1 order of magnitude higher than that of other periods in the electrochemical test, indicating that the biofilm and formed ferrous sulfide layer impeded the occurrence of corrosion. Although the 3D topography indicated that the surface of carbon steel was more uneven and pits were increased in the presence of SRB, the average weight loss (0.0396 ± 0.0050 g) was much higher than that without SRB (0.0139 ± 0.0007 g). These results implied that the growth of SRB makes the corrosion process of Q235 carbon steel more complicated.

Molecular basis of the phenotypic variants arising from a Pseudoalteromonas lipolytica mutator

Bacterial deficiencies in the DNA repair system can produce mutator strains that promote adaptive microevolution. However, the role of mutator strains in marine Pseudoalteromonas, capable of generating various gain-of-function genetic variants within biofilms, remains largely unknown. In this study, inactivation of mutS in Pseudoalteromonas lipolytica conferred an approximately 100-fold increased resistance to various antibiotics, including ciprofloxacin, rifampicin and aminoglycoside. Furthermore, the mutator of P. lipolytica generated variants that displayed enhanced biofilm formation but reduced swimming motility, indicating a high phenotypic diversity within the ΔmutS population. Additionally, we observed a significant production rate of approximately 50 % for the translucent variants, which play important roles in biofilm formation, when the ΔmutS strain was cultured on agar plates or under shaking conditions. Using whole-genome deep-sequencing combined with genetic manipulation, we demonstrated that point mutations in AT00_17115 within the capsular biosynthesis cluster were responsible for the generation of translucent variants in the ΔmutS subpopulation, while mutations in flagellar genes fliI and flgP led to a decrease in swimming motility. Collectively, this study reveals a specific mutator-driven evolution in P. lipolytica, characterized by substantial genetic and phenotypic diversification, thereby offering a reservoir of genetic attributes associated with microbial fitness.

Marinobacter: A case study in bioelectrochemical chassis evaluation

The junction of bioelectrochemical systems and synthetic biology opens the door to many potentially groundbreaking technologies. When developing these possibilities, choosing the correct chassis organism can save a great deal of engineering effort and, indeed, can mean the difference between success and failure. Choosing the correct chassis for a specific application requires a knowledge of the metabolic potential of the candidate organisms, as well as a clear delineation of the traits, required in the application. In this review, we will explore the metabolic and electrochemical potential of a single genus, Marinobacter. We will cover its strengths, (salt tolerance, biofilm formation and electrochemical potential) and weaknesses (insufficient characterization of many strains and a less developed toolbox for genetic manipulation) in potential synthetic electromicrobiology applications. In doing so, we will provide a roadmap for choosing a chassis organism for bioelectrochemical systems.

Manipulating Bacterial Biofilms Using Materiobiology and Synthetic Biology Approaches

Bacteria form biofilms on material surfaces within hours. Biofilms are often considered problematic substances in the fields such as biomedical devices and the food industry; however, they are beneficial in other fields such as fermentation, water remediation, and civil engineering. Biofilm properties depend on their genome and the extracellular environment, including pH, shear stress, and matrices topography, stiffness, wettability, and charges during biofilm formation. These surface properties have feedback effects on biofilm formation at different stages. Due to emerging technology such as synthetic biology and genome editing, many studies have focused on functionalizing biofilm for specific applications. Nevertheless, few studies combine these two approaches to produce or modify biofilms. This review summarizes up-to-date materials science and synthetic biology approaches to controlling biofilms. The review proposed a potential research direction in the future that can gain better control of bacteria and biofilms.

Design of Multi-Functional Superhydrophobic Coating via Bacterium-Induced Hierarchically Structured Minerals on Steel Surface

The fabrication of an eco-friendly, multi-functional, and mechanically robust superhydrophobic coating using a simple method has many practical applications. Here, inspired by shell nacre, the micro- or nano-scale surface roughness that is necessary for superhydrophobic coatings was formed via Bacillus subtilis–induced mineralization. The biomineralized film coated with hexadecyltrimethoxysilane (HDTMS) exhibited superhydrophobicity with water contact angles of 156°. The biomimetic HDTMS/calcite-coating showed excellent self-cleaning, anti-icing, and anti-corrosion performances. Furthermore, mechanically robust superhydrophobicity could be realized by hierarchically structured biomineralized surfaces at two different length scales, with a nano-structure roughness to provide water repellency and a micro-structure roughness to provide durability. Our design strategy may guide the development of “green” superhydrophobic coatings that need to retain effective multi-functional abilities in harsh marine environments.

The effect of riboflavin on the microbiologically influenced corrosion of pure iron by Shewanella oneidensis MR-1

The microbiologically influenced corrosion of pure iron was investigated in the presence of Shewanella oneidensis MR-1 with various levels of exogenous riboflavin (RF) serving as electron shuttles for extracellular electron transfer (EET). With more RF available, a larger and denser phosphate layer was formed on the surface of pure iron by the bacteria. The results of electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization tests showed that the product layer provided good corrosion protection to the pure iron. Using electrochemical noise, we observed that the addition of RF accelerated the corrosion at the initial stage of immersion, thereby accelerating the deposition of products to form a protective layer subsequently.

Preparation and Properties of Environmentally Friendly Marine Antifouling Coatings Based on a Collaborative Strategy

Long-term and green marine antifouling coatings are an important means to prolong the service life of ships and other marine instruments and equipment. To accomplish this, we prepared three new green and high-efficiency antifouling coatings containing phthalimide derivatives inspired by capsaicin (PDIC-AC) by using a collaborative strategy that incorporates self-polishing, fouling repelling, and antifouling properties. Static simulation tests confirmed that the zinc acrylate resin of the PDIC-AC has excellent self-polishing properties due to changes in the roughness, surface free energy, and mass loss. Antifouling tests demonstrated that both PDIC and PDIC-AC possess efficient antibacterial and anti-algal effects. Moreover, marine field tests showed that the PDIC-AC are highly antifouling for at least 9 months, and their antifouling effect is similar to that of an antifouling coating with chlorothalonil (CT-AC). The collaborative strategy in this study can be used to research and develop long-term environmentally friendly antifouling coatings.

Extracellular Polymeric Substances and Biocorrosion/Biofouling: Recent Advances and Future Perspectives

Microbial cells secrete extracellular polymeric substances (EPS) to adhere to material surfaces, if they get in contact with solid materials such as metals. After phase equilibrium, microorganisms can adhere firmly to the metal surfaces causing metal dissolution and corrosion. Attachment and adhesion of microorganisms via EPS increase the possibility and the rate of metal corrosion. Many components of EPS are electrochemical and redox active, making them closely related to metal corrosion. Functional groups in EPS have specific adsorption ability, causing them to play a key role in biocorrosion. This review emphasizes EPS properties related to metal corrosion and protection and the underlying microbially influenced corrosion (MIC) mechanisms. Future perspectives regarding a comprehensive study of MIC mechanisms and green methodologies for corrosion protection are provided.

Bioinspired micro/nano structured aluminum with multifaceted applications

Inspired by many biological systems such as lotus leaves, insect wings and rose petals, great attention has been devoted to the study and fabrication of artificial superhydrophobic surfaces with multiple functionalities. In the present study, a simple and ecological synthesis route has been employed for large scale fabrication of self-assembled, sustainable nanostructures on unprocessed and micro imprinted aluminum surfaces named 'Nano' and 'Hierarchy'. The processed samples show extreme wettability ranging from superhydrophilicity to superhydrophobicity depending on post-processing conditions. The densely packed ellipsoidal nanostructures exhibited superhydrophobicity with excellent water, bacterial and dust repellency when modified by low surface energy material 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTES), characterized by a static contact angle of 163 ± 1° and contact angle hysteresis (CAH) ~3°. These coated surfaces show significant corrosion resistance with current density of 6 nA/cm² which is 40 times lower than unprocessed counterpart and retain chemical stability after prolonged immersion in corrosive media. These surfaces show excellent self-cleaning ability with significantly low water consumption (< 0.1 µl/mm²-mg) and prevent biofouling which ensures its applicability in biological environment and marine components. The nanostructured superhydrophilic aluminum shows maximum antibacterial activity due to disruption of cell membrane. This work can offer a simple strategy to large scale fabrication of multifunctional biomimetic metallic surfaces.

Molecular Basis of Wrinkled Variants Isolated From Pseudoalteromonas lipolytica Biofilms

Many Pseudoalteromonas species are dominant biofilm-forming Gammaproteobacteria in the ocean. The formation of Pseudoalteromonas biofilms is often accompanied by the occurrence of variants with different colony morphologies that may exhibit increased marine antifouling or anticorrosion activities. However, the genetic basis of the occurrence of these variants remains largely unexplored. In this study, we identified that wrinkled variants of P. lipolytica mainly arose due to mutations in the AT00_08765, a wspF-like gene, that are associated with decreased swimming motility and increased cellulose production. Moreover, we found that the spontaneous mutation in flhA, encoding a flagellar biosynthesis protein, also caused a wrinkled colony morphology that is associated with cellulose overproduction, indicating that flhA plays a dual role in controlling flagellar assembly and polysaccharide production in P. lipolytica. Investigation of wrinkled variants harboring spontaneous mutation in dgcB, encoding a GGDEF domain protein, also demonstrated dgcB plays an important role in regulating cellulose production and swimming motility. In addition, by screening the suppressor of the AT00_08765 variant strain, we also identified that the spontaneous mutation in cheR and bcsC directly abolished the wrinkled phenotype of the AT00_08765 variant strain, suggesting that the chemosensory signaling transduction and cellulose production are crucial for the determination of the wrinkled phenotype in P. lipolytica. Taken together, this study provides insights into the genetic variation within biofilms of P. lipolytica.

Limiting nitrate triggered increased EPS film but decreased biocorrosion of copper induced by Pseudomonas aeruginosa

Biocorrosion of Cu remains a significant challenge in marine engineering but the mechanism is still not clear. The nutrients in marine environment affect the microbe's growth and the formation of biofilm, and then affect biocorrosion of metal to a large extent. In this study, the effect of NO3- concentration in Pseudomonas aeruginosa (P. aeruginosa) medium on the formation of extracellular polymer substance (EPS) film and biocorrosion of Cu were studied. The experiments results showed that limiting NO3- in culture medium triggered increased EPS film but decreased biocorrosion of Cu induced by P. aeruginosa. With increase of NO3- content in the culture medium, the Cu surface attached less polysaccharides and proteins, but the Cu corrosion rate was accelerated. The weight loss of Cu and the maximum pit depth were both increased with increase of NO3- content. The XPS and XRD analyses indicated that the major corrosion product is Cu2O. The increased corrosion rate with increase of the NO3- level were attributed to the EET-MIC route, the formation of Cu(NH3)2+, and the more loose EPS film.

New Biocalcifying Marine Bacterial Strains Isolated from Calcareous Deposits and Immediate Surroundings

Marine bacterial biomineralisation by CaCO3 precipitation provides natural limestone structures, like beachrocks and stromatolites. Calcareous deposits can also be abiotically formed in seawater at the surface of steel grids under cathodic polarisation. In this work, we showed that this mineral-rich alkaline environment harbours bacteria belonging to different genera able to induce CaCO3 precipitation. We previously isolated 14 biocalcifying marine bacteria from electrochemically formed calcareous deposits and their immediate environment. By microscopy and µ-Raman spectroscopy, these bacterial strains were shown to produce calcite-type CaCO3. Identification by 16S rDNA sequencing provided between 98.5 and 100% identity with genera Pseudoalteromonas, Pseudidiomarina, Epibacterium, Virgibacillus, Planococcus, and Bhargavaea. All 14 strains produced carbonic anhydrase, and six were urease positive. Both proteins are major enzymes involved in the biocalcification process. However, this does not preclude that one or more other metabolisms could also be involved in the process. In the presence of urea, Virgibacillus halodenitrificans CD6 exhibited the most efficient precipitation of CaCO3. However, the urease pathway has the disadvantage of producing ammonia, a toxic molecule. We showed herein that different marine bacteria could induce CaCO3 precipitation without urea. These bacteria could then be used for eco-friendly applications, e.g., the formation of bio-cements to strengthen dikes and delay coastal erosion.

Marine Biofilms with Significant Corrosion Inhibition Performance by Secreting Extracellular Polymeric Substances

The development of environmentally friendly and sustainable corrosion protection technologies is a longstanding yet difficult problem, especially for the marine environment. The utilization of living biofilms isolated from local environments is an effective strategy for infrastructure protection. In this study, three aerobic marine bacteria, Tenacibaculum mesophilum D-6, Tenacibaculum litoreum W-4, and Bacillus sp. Y-6, with strong biofilm-forming abilities were isolated and evaluated for the corrosion protection of X80 carbon steel. The corrosion inhibitory effect of the bacteria was found to be closely related to their biofilm-forming abilities. This conclusion was corroborated by biofilm characterization, electrochemical tests, weight loss analysis, and corrosion product analysis. Moreover, secreted extracellular polymeric substances were identified to play significant roles in corrosion inhibition. Herein, we proposed a novel, eco-friendly, and cost-effective method for corrosion protection of carbon steels in the marine environment, providing guiding principles for identifying corrosion inhibitory bacteria from the local marine environment.

Microbiologically influenced corrosion inhibition mechanisms in corrosion protection: A review

Microbial activities can change the properties of biofilm/metal interfaces to accelerate or decelerate the corrosion of metals in a given environment. Microbiologically influenced corrosion inhibition (MICI) is the inhibition of corrosion that is directly or indirectly induced by microbial action. Compared with conventional methods for protection from corrosion, MICI is environmentally friendly and an emerging approach for the prevention and treatment of (bio)corrosion. However, due to the diversity of microorganisms and the fact that their metabolic processes are greatly complicated by environmental factors, MICI is still facing challenges for practical application. This review provides a comprehensive overview of the mechanisms of MICI under different conditions and their advantages and disadvantages for potential applications in corrosion protection.

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.

Layer-by-layer zwitterionic modification of diverse substrates with durable anti-corrosion and anti-fouling properties

A versatile coating strategy, which is suitable for the anti-corrosion and anti-fouling modification of chemically distinct substrates, is crucial in many industries. The immobilization of zwitterionic polymers onto the surface has been proven to be an excellent approach for the improvement of antibiofouling potency. However, the anti-corrosion property has not always been considered simultaneously. Herein, a layer-by-layer (LBL) zwitterionic surface modification strategy was proposed: the surface was first coated with a polydopamine (PDA) layer for anti-corrosion; then, by self-assembling a monolayer of 3-aminopropyl triethoxysilane (APTES), the anti-corrosion ability was further enhanced and the efficiency of grafting was improved; thereafter, by immobilizing the zwitterionic polysulfobetaine (PSB) polymer brush layer, the surface could effectively repel biofouling. The surface chemical composition and morphology characterization was performed by using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle measurements, demonstrating that the modification was stepwise introduced onto the surface. The thickness of coating was observed and measured by SEM cross-sectional analysis. In vitro studies revealed that the PSB coated surfaces dramatically reduced the adhesion of bovine serum albumin (BSA), bovine plasma fibrinogen (Fg), bovine γ-globulin (γ-GL), the mixture of these proteins, fibroblasts, E. coli and S. aureus with superior cytocompatibility and hemocompatibility. Moreover, the electrochemical impedance spectroscopy and acidic corrosion studies indicated that an excellent and durable anti-corrosion property was established successfully on the surfaces of stainless steel, cotton textile and wood plates, confirming the feasibility of the LBL surface modification strategy. Significantly, this LBL surface chemistry may be widely applied for the modification of other materials, such as biosensors, biomedical implants and/or devices, and marine equipment.

Preliminary Investigation of Utilization of a Cellulose-Based Polymer in Enhanced Oil Recovery by Oilfield Anaerobic Microbes and its Impact on Carbon Steel Corrosion

Water injection increases reservoir pressure in enhanced oil recovery (EOR). Among other oilfield performance chemicals, an EOR polymer is added to the injection water to provide the viscosity necessary for effective displacement of viscous crude oil from the reservoir formation. However, these organic macromolecules may be degraded by microbes downhole, causing undesirable viscosity loss. The organic carbon utilization by the microbes promotes microbial metabolism, thus potentially exacerbating microbiologically influenced corrosion (MIC). In this preliminary laboratory investigation, 3,000 ppm (w/w) carboxymethyl cellulose sodium (CMCS), a commonly used EOR polymer, was found to be utilized by an oilfield biofilm consortium. This oilfield biofilm consortium consisted of bacteria (including that can degrade large organic molecules), sulfate-reducing bacteria (SRB), and other microorganisms. A 30-day incubation in 125 mL anaerobic vials was conducted with an artificial seawater medium without yeast extract and lactate supplements at 37°C. The polymer biodegradation led to 16% viscosity loss in the broth and a 30× higher SRB sessile cell count. Slightly increased MIC weight loss and pitting corrosion were observed on C1018 carbon steel coupons. Thus, the use of CMCS in EOR should take into the consideration of microbial degradation and its impact on MIC.

Two novel drugs as bio-functional inhibitors for copper performing excellent anticorrosion and antibacterial properties

Two drugs (cefpirome, cefixime) as dual-action inhibitors could self-organize on copper surface forming bio-functional protective film, which effectively prevents copper corrosion in the picking process with an excellent performance on the resistance of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) results showed that studied drugs can self-organize on copper surface successfully forming adsorption film to protect copper. The results also indicated that N/S atoms with the lone pair electrons in the drugs donated electrons to the vacant orbital of Cu occupying the active sites of copper surface. Electrochemistry and surface morphology study revealed that the corrosion inhibition efficiency of cefixime was better than cefpirome. Furthermore, adsorption isotherm study suggested that the adsorption was spontaneous chemical and physical adsorption, obeying Langmuir adsorption.

Microbiologically influenced corrosion of marine steels within the interaction between steel and biofilms: a brief view

Marine is the harshest corrosive environment where almost all marine underwater equipment and facilities undergo corrosion caused by marine microorganisms. With the development of marine resources globally, the marine engineering and relevant infrastructures have increased exponentially. Microbiologically influenced corrosion (MIC) leads to severe safety accidents and great economic losses. The specific aggregation of corrosive microbial communities and their interactions with materials conform to a typical ecological adaptation mechanism. On the one hand, corrosive biofilms in the marine environment selectively colonize on a specific steel substrate by utilizing their complex community composition and various extracellular polymeric substances; on the other hand, the elemental composition and surface microstructure of different engineering steels affect the microbial community and corrosive process. MIC in the marine environment is a dynamic process evolving with the formation of corrosive biofilms and corrosion products. In this mini-review, the interactions between corrosive biofilm and steel substrates are explored and discussed, especially those conducted in situ in the marine environment. Herein, the important role of iron in the dynamic process of marine corrosion is highlighted.

One-Step Removal of Calcium, Magnesium, and Nickel in Desalination by Alcaligenes aquatilis via Biomineralization

In desalination, a high level of calcium (Ca) and magnesium (Mg) ions in seawater can cause scale deposition on the reverse osmosis membranes and water treatment systems. This process can significantly affect the efficiency of desalination. In addition, heavy metals in seawater affect human health. Therefore, Alcaligenes aquatilis from seawater was used to remove Ca, Mg, and nickel (Ni) by microbial-induced carbonate precipitation (MICP). The purification system was then analyzed by ionic analysis and surface characterization. This study shows that the bacteria can utilize amino acids to produce carbonate and form precipitates with a high removal rate. MICP via A. aquatilis removed 91.8%, 68.5%, and 92.2% of the initial soluble Ca, Mg, and Ni, respectively. Furthermore, A. aquatilis can remove ammonium after the MICP process under oxygen-rich conditions. Therefore, we provide interesting insight into the use of Alcaligenes (in the absence of urea) to improve the seawater quality in the process of desalination.

Efficient removal of atrazine by iron-modified biochar loaded Acinetobacter lwoffii DNS32

In order to efficiently remove commonly used herbicide atrazine in farmland, an iron-modified biochar (FeMBC) was fabricated via chemical co-precipitation of Fe³⁺ onto corn stalks biochar. The composites of FeMBC and Acinetobacter lwoffii DNS32 (bFeMBC) effectively accelerated the degradation rate of atrazine (100 mg L^-1) in inorganic salt culture solution. TEM，XRD，XPS and FTIR were used to study the basic properties of the Materials. FeMBC promoted the formation of bacterial biofilm, -NH functional group on the surface of bacterial extracellular polymers (EPS) and FeMBC could interact with the aromatic ring of atrazine through Hbonding, which were conducive for microbial capture of atrazine. Meanwhile, the pores (2-10 μm) of FeMBC facilitated the passage of the DNS32 strain and the atrazine molecule, which contributed to the efficient capture and degradation of atrazine by DNS32 strain. BFeMBC amendment helped to maintain the bacterial diversity in the atrazine contaminated soil. The increase of rare bacteria (relative abundance of 0.01%-0.05%) richness plays a certain role in stabilizing nutrient cycling, thereby promoting microbial nutrient utilization activities and has the function of pollutant degradation. This may contribute to the digestion of atrazine and its intermediate metabolites，reducing the stress of microbial in atrazine contaminated soil. bFeMBC amendment may be a promising in situ remediation technique for soil atrazine contamination.

Biofilm formation in Pseudoalteromonas lipolytica is related to IS5-like insertions in the capsular polysaccharide operon

Bacterial capsular polysaccharides (CPSs) participate in environmental adaptation in diverse bacteria species. However, the role and regulation of CPS production in marine bacteria have remained largely unexplored. We previously reported that both wrinkled and translucent Pseudoalteromonas lipolytica variants with altered polysaccharide production were generated in pellicle biofilm-associated cells. In this study, we observed that translucent variants were generated at a rate of ∼20% in colony biofilms of P. lipolytica cultured on HSLB agar plates for 12 days. The DNA sequencing results revealed that nearly 90% of these variants had an IS5-like element inserted within the coding or promoter regions of nine genes in the cps operon. In contrast, IS5 insertion into the cps operon was not detected in planktonic cells. Furthermore, we demonstrated that the IS5 insertion event inactivated CPS production, which leads to a translucent colony morphology. The CPS-deficient variants showed an increased ability to form attached biofilms but exhibited reduced resistance to sublethal concentrations of antibiotics. Moreover, deleting the DNA repair gene recA significantly decreased the frequency of occurrence of CPS-deficient variants during biofilm formation. Thus, IS insertion into the cps operon is an important mechanism for the production of genetic variants during biofilm formation of marine bacteria.

Bacillus subtilis Inhibits Vibrio natriegens-Induced Corrosion via Biomineralization in Seawater

The marine bacterium, Vibrio natriegens, grows quickly in a marine environment and can significantly accelerate the corrosion of steel materials. Here, we present an approach to inhibit V. natriegens-induced corrosion by biomineralization. The corrosion of steel is mitigated in seawater via the formation of a biomineralized film induced by Bacillus subtilis. The film is composed of extracellular polymeric substances (EPS) and calcite, exhibiting stable anti-corrosion activity. The microbial diversity and medium chemistry tests demonstrated that the inhibition of V. natriegens growth by B. subtilis was essential for the formation of the biomineralized film.

Corrosion of Q235 Carbon Steel in Seawater Containing Mariprofundus ferrooxydans and Thalassospira sp

Iron-oxidizing bacteria (IOB) and iron-reducing bacteria (IRB) can easily adhere onto carbon steel surface to form biofilm and affect corrosion processes. However, the mechanism of mixed consortium induced carbon steel corrosion is relatively underexplored. In this paper, the adsorptions of IOB (Mariprofundus ferrooxydans, M. f.), IRB (Thalassospira sp., T. sp.) and mixed consortium (M. f. and T. sp.) on surface of Q235 carbon steel and their effects on corrosion in seawater were investigated through surface analysis techniques and electrochemical methods. Results showed that local adhesion is a typical characteristic for biofilm on surface of Q235 carbon steel in M. f. and mixed consortium media, which induces localized corrosion of Q235 carbon steel. Corrosion rates of Q235 carbon steel in different culture media decrease in the order: r_M.f. > r_{mixed consortium} > r_T.sp. > r_sterile. The evolution of corrosion rate along with time decreases in M. f. medium, and increases then keeps table in both T. sp. and mixed consortium media. Corrosion mechanism of Q235 carbon steel in mixed consortium medium is discussed through analysis of surface morphology and composition, environmental parameter, and electrochemical behavior.