Crystallographic plane-induced selective mineralization of nanohydroxyapatite on fibrous-grained titanium promotes osteointegration and biocorrosion resistance.

The (002) crystallographic plane-oriented hydroxyapatite (HA) and anatase TiO2 enable favorable hydrophilicity, osteogenesis, and biocorrosion resistance. Thus, the crystallographic plane control in HA coating and crystalline phase control in TiO2 is vital to affect the surface and interface bioactivity and biocorrosion resistance of titanium (Ti) implants. However, a corresponding facile and efficient fabrication method is absent to realize the HA(002) mineralization and anatase TiO2 formation on Ti. Herein, we utilized the predominant Ti(0002) plane of the fibrous-grained titanium (FG Ti) to naturally form anatase TiO2 and further achieve a (002) basal plane oriented nanoHA (nHA) film through an in situ mild hydrothermal growth strategy. The formed FG Ti-nHA(002) remarkably improved hydrophilicity, mineralization, and biocorrosion resistance. Moreover, the nHA(002) film reserved the microgroove-like topological structure on FG Ti. It could enhance osteogenic differentiation through promoted contact guidance, showing one order of magnitude higher expression of osteogenic-related genes. On the other hand, the nHA(002) film restrained the osteoclast activity by blocking actin ring formation. Based on these capacities, FG Ti-nHA(002) improved new bone growth and binding strength in rabbit femur implantation, achieving satisfactory osseointegration within 2 weeks.

A New Convenient Method to Assess Antibiotic Resistance and Antimicrobial Efficacy against Pathogenic Clostridioides difficile Biofilms.

Clostridioides difficile is a widely distributed anaerobic pathogen. C. difficile infection is a serious problem in healthcare. Its biofilms have been found to exhibit biocorrosivity, albeit very little, but sufficient for it to correlate with biofilm growth/health. This work demonstrated the use of a disposable electrochemical biofilm test kit using two solid-state electrodes (a 304 stainless steel working electrode, and a graphite counter electrode, which also served as the reference electrode) in a 10 mL serum vial. It was found that the C. difficile 630∆erm Adp-4 mutant had a minimum inhibitory concentration (MIC) for vancomycin twice that of the 630∆erm wild type strain in biofilm prevention (2 ppm vs. 1 ppm by mass) on 304 stainless steel. Glutaraldehyde, a commonly used hospital disinfectant, was found ineffective at 2% (w/w) for the prevention of C. difficile 630∆erm wild type biofilm formation, while tetrakis(hydroxymethyl)phosphonium sulfate (THPS) disinfectant was very effective at 100 ppm for both biofilm prevention and biofilm killing. These antimicrobial efficacy data were consistent with sessile cell count and biofilm imaging results. Furthermore, the test kit provided additional transient biocide treatment information. It showed that vancomycin killed C. difficile 630∆erm wild type biofilms in 2 d, while THPS only required minutes.

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.

3D Spongin Scaffolds as Templates for Electro-Assisted Deposition of Selected Iron Oxides.

The skeletons of marine sponges are ancient biocomposite structures in which mineral phases are formed on 3D organic matrices. In addition to calcium- and silicate-containing biominerals, iron ions play an active role in skeleton formation in some species of bath sponges in the marine environment, which is a result of the biocorrosion of the metal structures on which these sponges settle. The interaction between iron ions and biopolymer spongin has motivated the development of selected extreme biomimetics approaches with the aim of creating new functional composites to use in environmental remediation and as adsorbents for heavy metals. In this study, for the first time, microporous 3D spongin scaffolds isolated from the cultivated marine bath sponge Hippospongia communis were used for electro-assisted deposition of iron oxides such as goethite [α-FeO(OH)] and lepidocrocite [γ-FeO(OH)]. The obtained iron oxide phases were characterized with the use of scanning electron microscopy, FTIR, and X-ray diffraction. In addition, mechanisms of electro-assisted deposition of iron oxides on the surface of spongin, as a sustainable biomaterial, are proposed and discussed.

How Often Should Microbial Contamination Be Detected in Aircraft Fuel Systems? An Experimental Test of Aluminum Alloy Corrosion Induced by Sulfate-Reducing Bacteria.

Microbial contamination in aircraft fuel-containing systems poses significant threats to flight safety and operational integrity as a result of microbiologically influenced corrosion (MIC). Regular monitoring for microbial contamination in these fuel systems is essential for mitigating MIC risks. However, the frequency of monitoring remains a challenge due to the complex environmental conditions encountered in fuel systems. To investigate the impact of environmental variables such as water content, oxygen levels, and temperature on the MIC of aluminum alloy in aircraft fuel systems, orthogonal experiments with various combinations of these variables were conducted in the presence of sulfate-reducing bacteria. Among these variables, water content in the fuel oil demonstrated the most substantial influence on the corrosion rate of aluminum alloys, surpassing the effects of oxygen and temperature. Notably, the corrosion rate of aluminum alloys was the highest in an environment characterized by a 1:1 water/oil ratio, 0% oxygen, and a temperature of 35 °C. Within this challenging environment, conducive to accelerated corrosion, changes in the corrosion behavior of aluminum alloys over time were analyzed to identify the time point at which MIC intensified. Observations revealed a marked increase in the depth and width of corrosion pits, as well as in the corrosion weight-loss rate, starting from the 7th day. These findings offer valuable insights for determining the optimal frequency of microbial contamination detection in aircraft fuel systems.

Biocorrosion and Cytotoxicity Studies on Biodegradable Mg-Based Multicomponent Alloys.

Magnesium-based multicomponent alloys with different compositions, namely Mg60Al20Zn5Cu10Mn5 (Mg60 alloy), Mg70Al15Zn5Cu5Mn5 (Mg70 alloy), and Mg80Al5Cu5Mn5Zn5 (Mg 80) alloys, were prepared using the disintegrated melt deposition technique. The DMD technique is a distinctive method that merges the benefits from gravity die casting and spray forming. This approach facilitates high solidification rates, process yields, and reduced metal wastage, resulting in materials with a fine microstructure and minimal porosity. Their potential as biodegradable materials was assessed through corrosion in different simulated body fluids (SBFs), microstructure, and cytotoxicity tests. It was observed that the Mg60 alloy exhibited low corrosion rates (~× 10-5 mm/year) in all SBF solutions, with a minor amount of corrosive products, and cracks were observed. This can be attributed to the formation of the Mg32(AlZn)49 phase and to its stability due to Mg(OH)2 film, leading to excellent corrosion resistance when compared to the Mg70 and M80 alloys. Conversely, the Mg80 alloy exhibited high corrosion rates, along with more surface degradation and cracks, due to active intermetallic phases, such as Al6Mn, Al2CuMg, and Al2Cu phases. The order of corrosion resistance for the Mg alloy was found to be ASS > HBSS > ABP > PBS. Further, in vitro cytotoxicity studies were carried out using MDA-MB-231 tumor cells. By comparing all three alloys, in terms of proliferation and vitality, the Mg80 alloy emerged as a promising material for implants, with potential antitumor activity.

Interfaces between Cranial Bone and AISI 304 Steel after Long-Term Implantation: A Case Study of Cranial Screws.

Interfaces between AISI 304 stainless steel screws and cranial bone were investigated after long-term implantation lasting for 42 years. Samples containing the interface regions were analyzed using state-of-the-art analytical techniques including secondary ion mass, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies. Local samples for scanning transmission electron microscopy were cut from the interface regions using the focused ion beam technique. A chemical composition across the interface was recorded in length scales covering micrometric and nanometric resolutions and relevant differences were found between peri-implant and the distant cranial bone, indicating generally younger bone tissue in the peri-implant area. Furthermore, the energy dispersive spectroscopy revealed an 80 nm thick steel surface layer enriched by oxygen suggesting that the AISI 304 material undergoes a corrosion attack. The attack is associated with transport of metallic ions, namely, ferrous and ferric iron, into the bone layer adjacent to the implant. The results comply with an anticipated interplay between released iron ions and osteoclast proliferation. The interplay gives rise to an autocatalytic process in which the iron ions stimulate the osteoclast activity while a formation of fresh bone resorption sites boosts the corrosion process through interactions between acidic osteoclast extracellular compartments and the implant surface. The autocatalytic process thus may account for an accelerated turnover of the peri-implant bone.

Bio-corrosion in concrete sewer systems: Mechanisms and mitigation strategies.

The deterioration of concrete sewer structures due to bio-corrosion presents critical and escalating challenges from structural, economic and environmental perspectives. Despite decades of research, this issue remains inadequately addressed, resulting in billions of dollars in maintenance costs and a shortened service life for sewer infrastructure worldwide. This challenge is exacerbated by the absence of standardized test methods and universally accepted mitigation strategies, leaving industries and stakeholders confronting an increasingly pressing problem. This paper aims to bridge this knowledge gap by providing a comprehensive review of the complex mechanisms of bio-corrosion, focusing on the formation and accumulation of hydrogen sulfide, its conversion into sulfuric acid and the subsequent deterioration of concrete materials. The paper also explores various factors affecting bio-corrosion rates, including environmental conditions, concrete properties and wastewater characteristics. The paper further highlights existing corrosion test strategies, such as chemical tests, in-situ tests and microbial simulations tests along with their general analytical parameters. The conversion of hydrogen sulfide into sulfuric acid is a primary cause of concrete decay and its progression is influenced by environmental conditions, inherent concrete characteristics, and the composition of wastewater. Through illustrative case studies, the paper assesses the practical implications and efficacy of prevailing mitigation techniques. Coating materials provide a protective barrier against corrosive agents among the discussed techniques, while optimised concrete mix designs enhance the inherent resistance and durability of the concrete matrix. Finally, this review also outlines the future prospects and challenges in bio-corrosion research with an aim to promote the creation of more resilient and cost-efficient materials for sewer systems.

Development of PDMS/TiO2/Ag3PO4 antibacterial coating on 316L/PDMS implants: Evaluation of superhydrophobicity, bio-corrosion, mechanical behaviour, surface nanostructure and chemistry.

Nanocomposite coatings based on polydimethylsiloxane were developed by adding silver phosphate and titania nanoparticles with a PDMS pre-layer for 316L stainless steel. FTIR spectra and XRD patterns confirmed the synthesis of TiO2 and Ag3PO4 nanoparticles and nanocomposite coating. FESM and AFM images show that with the increase of Ag3PO4 nanoparticles, the roughness of coatings increased (Ra and Rq for adding 7 wt% of Ag3PO4 coating was 29 and 293 nm). The wettability results demonstrated that the presence of 7 wt% Ag3PO4 nanoparticles in the coating has the highest water contact angle (152 °). Nano-scratch results proved that creating a pre-layer of PDMS can increase the scratch resistance of PDMS + TiO2+Ag3PO4 nanocomposite coating (displacement and scratch coefficient were 408 nm and 0.07µΝ-1/2 with the pre-layer). Corrosion current density of 316lSS with PDMS + TiO2+Ag3PO4 coating was 0.00045 µA/cm2, while for 316LSS with pure PDMS coating was 0.00114 µA/cm2 at 37 °C in PBS solution. The Nyquist curves showed the diameter of the semicircle for the nanocomposite coating was larger than pure PDMS coating, which indicates the higher corrosion resistance of the nanocomposite coating (5.98 × 107 Ω). By increasing Ag3PO4 nanoparticles from 1 to 7 wt%, the number of E. coli bacteria in contact with the nanocomposite decreased significantly from 580000 to 31000 CFU/cm2. In the disk diffusion test, the largest inhibition zone was related to the nanocomposite coating with the addition of 7 wt% Ag3PO4 (23 mm). Therefore, the PDMS + TiO2+Ag3PO4 nanocomposite coating has improved properties such as superhydrophobicity, advanced mechanical behavior, bio-corrosion resistance, and antibacterial activity.

The microbial biodiversity at the archeological site of Tel Megiddo (Israel).

Introduction: The ancient city of Tel Megiddo in the Jezreel Valley (Israel), which lasted from the Neolithic to the Iron Age, has been continuously excavated since 1903 and is now recognized as a World Heritage Site. The site features multiple ruins in various areas, including temples and stables, alongside modern constructions, and public access is allowed in designated areas. The site has been studied extensively since the last century; however, its microbiome has never been studied. We carried out the first survey of the microbiomes in Tel Megiddo. Our objectives were to study (i) the unique microbial community structure of the site, (ii) the variation in the microbial communities across areas, (iii) the similarity of the microbiomes to urban and archeological microbes, (iv) the presence and abundance of potential bio-corroding microbes, and (v) the presence and abundance of potentially pathogenic microbes. Methods: We collected 40 swab samples from ten major areas and identified microbial taxa using next-generation sequencing of microbial genomes. These genomes were annotated and classified taxonomically and pathogenetically. Results: We found that eight phyla, six of which exist in all ten areas, dominated the site (>99%). The relative sequence abundance of taxa varied between the ruins and the sampled materials and was assessed using all metagenomic reads mapping to a respective taxon. The site hosted unique taxa characteristic of the built environment and exhibited high similarity to the microbiome of other monuments. We identified acid-producing bacteria that may pose a risk to the site through biocorrosion and staining and thus pose a danger to the site's preservation. Differences in the microbiomes of the publicly accessible or inaccessible areas were insignificant; however, pathogens were more abundant in the former. Discussion: We found that Tel Megiddo combines microbiomes of arid regions and monuments with human pathogens. The findings shed light on the microbial community structures and have relevance for bio-conservation efforts and visitor health.

Do biosurfactants as anti-biofilm agents have a future in industrial water systems?

Biofilms are bacterial communities embedded in exopolymeric substances that form on the surfaces of both man-made and natural structures. Biofilm formation in industrial water systems such as cooling towers results in biofouling and biocorrosion and poses a major health concern as well as an economic burden. Traditionally, biofilms in industrial water systems are treated with alternating doses of oxidizing and non-oxidizing biocides, but as resistance increases, higher biocide concentrations are needed. Using chemically synthesized surfactants in combination with biocides is also not a new idea; however, these surfactants are often not biodegradable and lead to accumulation in natural water reservoirs. Biosurfactants have become an essential bioeconomy product for diverse applications; however, reports of their use in combating biofilm-related problems in water management systems is limited to only a few studies. Biosurfactants are powerful anti-biofilm agents and can act as biocides as well as biodispersants. In laboratory settings, the efficacy of biosurfactants as anti-biofilm agents can range between 26% and 99.8%. For example, long-chain rhamnolipids isolated from Burkholderia thailandensis inhibit biofilm formation between 50% and 90%, while a lipopeptide biosurfactant from Bacillus amyloliquefaciens was able to inhibit biofilms up to 96% and 99%. Additionally, biosurfactants can disperse preformed biofilms up to 95.9%. The efficacy of antibiotics can also be increased by between 25% and 50% when combined with biosurfactants, as seen for the V9T14 biosurfactant co-formulated with ampicillin, cefazolin, and tobramycin. In this review, we discuss how biofilms are formed and if biosurfactants, as anti-biofilm agents, have a future in industrial water systems. We then summarize the reported mode of action for biosurfactant molecules and their functionality as biofilm dispersal agents. Finally, we highlight the application of biosurfactants in industrial water systems as anti-fouling and anti-corrosion agents.

Field testing of an enzymatic quorum quencher coating additive to reduce biocorrosion of steel.

Microbial colonization can be detrimental to the integrity of metal surfaces and lead to microbiologically influenced corrosion. Biocorrosion is a serious problem for aquatic and marine industries in the world and severely affects the maritime transportation industry by destroying port infrastructure and increasing fuel usage and the time and cost required for maintenance of transport vessels. Here, we evaluate the potential of a stable quorum quenching lactonase enzyme to reduce biocorrosion in the field. Over the course of 21 months, steel samples coated with lactonase-containing acrylic paint were submerged at two different sites and depths in the Duluth-Superior Harbor (Lake Superior, MN, USA) and benchmarked against controls, including the biological biocide surfactin. In this experiment, the lactonase treatment outperformed the surfactin biocide treatment and significantly reduced the number of corrosion tubercles (37%; P < 0.01) and the corroded surface area (39%; P < 0.01) as compared to the acrylic-coated control coupons. In an attempt to evaluate the effects of signal disruption of surface microbial communities and the reasons for lower corrosion levels, 16S rRNA sequencing was performed and community populations were analyzed. Interestingly, surface communities were similar between all treatments, and only minor changes could be observed. Among these changes, several groups, including sulfate-reducing bacteria (SRB), appeared to correlate with corrosion levels, and more specifically, SRB abundance levels were lower on lactonase-treated steel coupons. We surmise that these minute community changes may have large impacts on corrosion rates. Overall, these results highlight the potential use of stable quorum quenching lactonases as an eco-friendly antifouling coating additive. IMPORTANCE Biocorrosion severely affects the maritime transportation industry by destroying port infrastructure and increasing fuel usage and the time and cost required to maintain transport vessels. Current solutions are partly satisfactory, and the antifouling coating still largely depends on biocide-containing products that are harmful to the environment. The importance of microbial signaling in biofouling and biocorrosion is not elucidated. We here take advantage of a highly stable lactonase that can interfere with N-acyl homoserine lactone-based quorum sensing and remain active in a coating base. The observed results show that an enzyme-containing coating can reduce biocorrosion over 21 months in the field. It also reveals subtle changes in the abundance of surface microbes, including sulfate-reducing bacteria. This work may contribute to pave the way for strategies pertaining to surface microbiome changes to reduce biocorrosion.

Spongin as a Unique 3D Template for the Development of Functional Iron-Based Composites Using Biomimetic Approach In Vitro.

Marine sponges of the subclass Keratosa originated on our planet about 900 million years ago and represent evolutionarily ancient and hierarchically structured biological materials. One of them, proteinaceous spongin, is responsible for the formation of 3D structured fibrous skeletons and remains enigmatic with complex chemistry. The objective of this study was to investigate the interaction of spongin with iron ions in a marine environment due to biocorrosion, leading to the occurrence of lepidocrocite. For this purpose, a biomimetic approach for the development of a new lepidocrocite-containing 3D spongin scaffold under laboratory conditions at 24 °C using artificial seawater and iron is described for the first time. This method helps to obtain a new composite as "Iron-Spongin", which was characterized by infrared spectroscopy and thermogravimetry. Furthermore, sophisticated techniques such as X-ray fluorescence, microscope technique, and X-Ray diffraction were used to determine the structure. This research proposed a corresponding mechanism of lepidocrocite formation, which may be connected with the spongin amino acids functional groups. Moreover, the potential application of the biocomposite as an electrochemical dopamine sensor is proposed. The conducted research not only shows the mechanism or sensor properties of "Iron-spongin" but also opens the door to other applications of these multifunctional materials.

Tackling fat, oil, and grease (FOG) build-up in sewers: Insights into deposit formation and sustainable in-sewer management techniques.

The increasing global demand for fatty products, population growth, and the expansion of food service establishments (FSEs) present significant challenges for the wastewater industry. This is often due to the build-up of fat, oil and grease (FOG) in sewers, which reduces capacity and leads to sanitary sewer overflows. It is crucial to develop economic and sustainable in-sewer FOG management techniques to minimise maintenance costs and service disruptions caused by the removal of FOG deposits from sewers. This study aims to understand the process of FOG deposit formation in both concrete and non-concrete sewers. Compared to fresh cooking oil, disposal of used cooking oil in households and FSE sinks results in the formation of highly adhesive and viscous FOG deposits. This occurs due to hydrolysis during frying, which increases the concentration of fatty acids, particularly palmitic acid, in the used cooking oil. Furthermore, metal ions from food waste, wastewater, and dishwashing detergents contribute to the saponification and aggregation reactions which cause FOG deposition in both concrete and non-concrete sewers. However, the leaching of Ca2+ ions exacerbates FOG deposition in cement-concrete sewers. The article concludes by suggesting future research perspectives and proposes implementation strategies for microbially induced concrete corrosion (MICC) control to manage FOG deposition in sewers. One such strategy involves applying superhydrophobic coating materials with low surface free energy and high surface roughness to the interior surfaces of the sewer. This approach would help repel wastewater carrying FOG deposit components, potentially disrupting the interaction between FOG components, and reducing the adhesion of FOG deposits to sewer surfaces.

Microstructural, Mechanical, and Electrochemical Characterization of CrMoNbTiZr High-Entropy Alloy for Biomedical Application.

High-entropy alloys (HEA) with superior biocompatibility, high pitting resistance, minimal debris accumulation, and reduced release of metallic ions into surrounding tissues are potential replacements for traditional metallic bio-implants. A novel equiatomic HEA based on biocompatible metals, CrMoNbTiZr, was consolidated by spark plasma sintering (SPS). The relative sintered density of the alloy was about 97% of the theoretical density, indicating the suitability of the SPS technique to produce relatively dense material. The microstructure of the sintered HEA consisted of a BCC matrix and Laves phase, corresponding to the prediction of the thermodynamic CALPHAD simulation. The HEA exhibited a global Vickers microhardness of 531.5 ± 99.7 HV, while the individual BCC and Laves phases had hardness values of 364.6 ± 99.4 and 641.8 ± 63.0 HV, respectively. Its ultimate compressive and compressive yield strengths were 1235.7 ± 42.8 MPa and 1110.8 ± 78.6 MPa, respectively. The elasticity modulus of 34.9 ± 2.9 GPa of the HEA alloy was well within the range of cortical bone and significantly lower than the values reported for commonly used biomaterials made from Ti-based and Cr-Co-based alloys. In addition, the alloy exhibited good resistance to bio-corrosion in PBS and Hanks solutions. The CrMoNbTiZr HEA exhibited an average COF of 0.43 ± 0.06, characterized mainly by abrasive and adhesive wear mechanisms. The CrMoNbTiZr alloy's mechanical, bio-corrosion, and wear resistance properties developed in this study showed a good propensity for application as a biomaterial.

Antibiofilm assay for antimicrobial peptides combating the sulfate-reducing bacteria Desulfovibrio vulgaris.

In medical, environmental, and industrial processes, the accumulation of bacteria in biofilms can disrupt many processes. Antimicrobial peptides (AMPs) are receiving increasing attention in the development of new substances to avoid or reduce biofilm formation. There is a lack of parallel testing of the effect against biofilms in this area, as well as in the testing of other antibiofilm agents. In this paper, a high-throughput screening was developed for the analysis of the antibiofilm activity of AMPs, differentiated into inhibition and removal of a biofilm. The sulfate-reducing bacterium Desulfovibrio vulgaris was used as a model organism. D. vulgaris represents an undesirable bacterium, which is considered one of the major triggers of microbiologically influenced corrosion. The application of a 96-well plate and steel rivets as a growth surface realizes real-life conditions and at the same time establishes a flexible, simple, fast, and cost-effective assay. All peptides tested in this study demonstrated antibiofilm activity, although these peptides should be individually selected depending on the addressed aim. For biofilm inhibition, the peptide DASamP1 is the most suitable, with a sustained effect for up to 21 days. The preferred peptides for biofilm removal are S6L3-33, in regard to bacteria reduction, and Bactenecin, regarding total biomass reduction.

Microbiologically influenced corrosion-more than just microorganisms.

Microbiologically influenced corrosion (MIC) is a phenomenon of increasing concern that affects various materials and sectors of society. MIC describes the effects, often negative, that a material can experience due to the presence of microorganisms. Unfortunately, although several research groups and industrial actors worldwide have already addressed MIC, discussions are fragmented, while information sharing and willingness to reach out to other disciplines are limited. A truly interdisciplinary approach, which would be logical for this material/biology/chemistry-related challenge, is rarely taken. In this review, we highlight critical non-biological aspects of MIC that can sometimes be overlooked by microbiologists working on MIC but are highly relevant for an overall understanding of this phenomenon. Here, we identify gaps, methods, and approaches to help solve MIC-related challenges, with an emphasis on the MIC of metals. We also discuss the application of existing tools and approaches for managing MIC and propose ideas to promote an improved understanding of MIC. Furthermore, we highlight areas where the insights and expertise of microbiologists are needed to help progress this field.

Mitigation of EH36 ship steel biocorrosion using an antimicrobial peptide as a green biocide enhancer.

In this study, a 13-mer antimicrobial peptide (RRWRIVVIRVRRC) named by E6 was used as an enhancer of a green biocide to mitigate the biocorrosion of EH36 ship steel. Results show that a low concentration of E6 (100 nM) alone was no-biocidal and could not resist the Desulfovibrio vulgaris adhesion on the EH36 steel surface. However, E6 enhanced the bactericidal effect of tetrakis hydroxymethyl phosphonium sulfate (THPS). When E6 and THPS were both added to the bacteria and steel system, both the sessile D. vulgaris cells and biocorrosion rate of EH36 steel decreased significantly. Compared with the 80 ppm THPS alone treatment, the combination of 100 nM E6 + 80 ppm THPS led to an extra 1.6-log reduction in the sessile cell count. Fewer sessile D. vulgaris cells led to a lower extracellular electron transfer (EET) rate, directly resulting in 78% and 83% decreases in weight loss and pit depth of EH36 steel, respectively. E6 saved more than 50% of THPS dosage in this work to achieve a similar biocorrosion mitigation effect on EH36 steel.

Multilevel Assessment of Stent-Induced Inflammation in the Adjacent Vascular Tissue.

A recent U.S. Food and Drug Administration report presented the currently available scientific information related to biological response to metal implants. In this work, a multilevel approach was employed to assess the implant-induced and biocorrosion-related inflammation in the adjacent vascular tissue using a mouse stent implantation model. The implications of biocorrosion on peri-implant tissue were assessed at the macroscopic level via in vivo imaging and histomorphology. Elevated matrix metalloproteinase activity, colocalized with the site of implantation, and histological staining indicated that stent surface condition and implantation time affect the inflammatory response and subsequent formation and extent of neointima. Hematological measurements also demonstrated that accumulated metal particle contamination in blood samples from corroded-stetted mice causes a stronger immune response. At the cellular level, the stent-induced alterations in the nanostructure, cytoskeleton, and mechanical properties of circulating lymphocytes were investigated. It was found that cells from corroded-stented samples exhibited higher stiffness, in terms of Young's modulus values, compared to noncorroded and sham-stented samples. Nanomechanical modifications were also accompanied by cellular remodeling, through alterations in cell morphology and stress (F-actin) fiber characteristics. Our analysis indicates that surface wear and elevated metal particle contamination, prompted by corroded stents, may contribute to the inflammatory response and the multifactorial process of in-stent restenosis. The results also suggest that circulating lymphocytes could be a novel nanomechanical biomarker for peri-implant tissue inflammation and possibly the early stage of in-stent restenosis. Large-scale studies are warranted to further investigate these findings.

The effect of Artemisia annua L. extract on microbiologically influenced corrosion of A36 steel caused by Pseudomonas aeruginosa.

The protective effect of A. annua against microbiologically influenced corrosion (MIC) of A36 steel caused by P. aeruginosa (PA) in a simulated marine environment was investigated using electrochemical, spectroscopic, and surface techniques. PA was found to accelerate the local dissolution of A36 which led to the formation of a porous α-FeOOH and γ-FeOOH surface layer. 2D and 3D profiles of treated coupons, obtained by optical profilometer, revealed the formation of crevices in the presence of PA. On the contrary, adding A. annua to the biotic medium led to the formation of a thinner, more uniform surface without significant damage. Electrochemical data showed that the addition of A. annua prevented the MIC of A36 steel with an inhibition efficiency of 60%. The protective effect was attributed to the formation of a more compact Fe3O4 surface layer, as well as the adsorption of phenolics, such as caffeic acid and its derivatives on the A36 steel surfaces, as detected by FTIR and SEM-EDS analysis. ICP-OES confirmed that Fe and Cr species more readily diffuse from A36 steel surfaces incubated in biotic media (Fe; 1516.35 ± 7.94 µg L-1 cm-2, Cr; 11.77 ± 0.40 µg L-1 cm-2) compared to the inhibited media (Fe; 35.01 ± 0.28 µg L-1 cm-2, Cr; 1.58 ± 0.01 µg L-1 cm-2).