Inhibiting mild steel corrosion from sulfate-reducing bacteria using antimicrobial-producing biofilms in Three-Mile-Island process water

Microbiome analysis of the restricted bacteria in radioactive element-containing water at the Fukushima Daiichi Nuclear Power Station

A major incident occurred at the Fukushima Daiichi Nuclear Power Station following the tsunami triggered by the Tohoku-Pacific Ocean Earthquake in March 2011, whereby seawater entered the torus room in the basement of the reactor building. Here, we identify and analyze the bacterial communities in the torus room water and several environmental samples. Samples of the torus room water (1 × 109 Bq137Cs/L) were collected by the Tokyo Electric Power Company Holdings from two sampling points between 30 cm and 1 m from the bottom of the room (TW1) and the bottom layer (TW2). A structural analysis of the bacterial communities based on 16S rRNA amplicon sequencing revealed that the predominant bacterial genera in TW1 and TW2 were similar. TW1 primarily contained the genus Limnobacter, a thiosulfate-oxidizing bacterium. γ-Irradiation tests on Limnobacter thiooxidans, the most closely related phylogenetically found in TW1, indicated that its radiation resistance was similar to ordinary bacteria. TW2 predominantly contained the genus Brevirhabdus, a manganese-oxidizing bacterium. Although bacterial diversity in the torus room water was lower than seawater near Fukushima, ~70% of identified genera were associated with metal corrosion. Latent environment allocation-an analytical technique that estimates habitat distributions and co-detection analyses-revealed that the microbial communities in the torus room water originated from a distinct blend of natural marine microbial and artificial bacterial communities typical of biofilms, sludge, and wastewater. Understanding the specific bacteria linked to metal corrosion in damaged plants is important for advancing decommissioning efforts.

IMPORTANCE

In the context of nuclear power station decommissioning, the proliferation of microorganisms within the reactor and piping systems constitutes a formidable challenge. Therefore, the identification of microbial communities in such environments is of paramount importance. In the aftermath of the Fukushima Daiichi Nuclear Power Station accident, microbial community analysis was conducted on environmental samples collected mainly outside the site. However, analyses using samples from on-site areas, including adjacent soil and seawater, were not performed. This study represents the first comprehensive analysis of microbial communities, utilizing meta 16S amplicon sequencing, with a focus on environmental samples collected from the radioactive element-containing water in the torus room, including the surrounding environments. Some of the identified microbial genera are shared with those previously identified in spent nuclear fuel pools in countries such as France and Brazil. Moreover, our discussion in this paper elucidates the correlation of many of these bacteria with metal corrosion.

Special Issue: Biofilm Composition and Applications

Biofilms can be formed on both biotic and abiotic surfaces, including on living tissues, indwelling medical devices, industrial or portable water system piping, and natural aquatic systems [...]

Preserving Microbial Community Integrity in Oilfield Produced Water

Determining a representative microbial signature from any given location is dependent on robust sample collection and handling. Different sampling locations and hence sample properties can vary widely; for example, soil would be collected and handled differently compared to liquid samples. In the event that sample material has a low concentration of biomass, large quantities need to be collected for microbial community analysis. This is certainly the case when investigating the microbiology of oilfield systems, wherein produced water (PW) is one of the most common sources for microbial sampling. As the detrimental effects of microbial metabolism within these industrial milieus are becoming increasingly well-established, the characterization of microbial community composition using molecular biological analyses is becoming more commonplace for accurate monitoring. As this field continues to develop, the importance for standardized operating protocols cannot be understated, so that industry can make the most informed operational decisions possible. Accurately identifying oilfield microbial communities is paramount, as improper preservation and storage following sample collection is known to lead to erroneous microbial identifications. Preserving oilfield PW can be challenging, as many locations are remote, requiring lengthy periods of time before samples can be processed and analyzed. While previous studies have characterized the effects of various preservatives on concentrated, filtered, or purified microbial samples, to the best of our knowledge, no such study has been undertaken on low biomass liquid samples. To this end, we investigated the effectiveness of nine different preservation conditions on PW collected from the same sampling location within a heavy-oil producing field, and monitored how the microbial community changed over the period of a month. Our results reveal that the choice of preservative drastically affects microbial community, and should be selected with careful consideration before sampling occurs.

Beyond Risk: Bacterial Biofilms and Their Regulating Approaches

Bacterial biofilms are complex surface attached communities of bacteria held together by self-produced polymer matrixs mainly composed of polysaccharides, secreted proteins, and extracellular DNAs. Bacterial biofilm formation is a complex process and can be described in five main phases: (i) reversible attachment phase, where bacteria non-specifically attach to surfaces; (ii) irreversible attachment phase, which involves interaction between bacterial cells and a surface using bacterial adhesins such as fimbriae and lipopolysaccharide (LPS); (iii) production of extracellular polymeric substances (EPS) by the resident bacterial cells; (iv) biofilm maturation phase, in which bacterial cells synthesize and release signaling molecules to sense the presence of each other, conducing to the formation of microcolony and maturation of biofilms; and (v) dispersal/detachment phase, where the bacterial cells depart biofilms and comeback to independent planktonic lifestyle. Biofilm formation is detrimental in healthcare, drinking water distribution systems, food, and marine industries, etc. As a result, current studies have been focused toward control and prevention of biofilms. In an effort to get rid of harmful biofilms, various techniques and approaches have been employed that interfere with bacterial attachment, bacterial communication systems (quorum sensing, QS), and biofilm matrixs. Biofilms, however, also offer beneficial roles in a variety of fields including applications in plant protection, bioremediation, wastewater treatment, and corrosion inhibition amongst others. Development of beneficial biofilms can be promoted through manipulation of adhesion surfaces, QS and environmental conditions. This review describes the events involved in bacterial biofilm formation, lists the negative and positive aspects associated with bacterial biofilms, elaborates the main strategies currently used to regulate establishment of harmful bacterial biofilms as well as certain strategies employed to encourage formation of beneficial bacterial biofilms, and highlights the future perspectives of bacterial biofilms.

Biosurfactants: Eco-Friendly and Innovative Biocides against Biocorrosion

Corrosion influenced by microbes, commonly known as microbiologically induced corrosion (MIC), is associated with biofilm, which has been one of the problems in the industry. The damages of industrial equipment or infrastructures due to corrosion lead to large economic and environmental problems. Synthetic chemical biocides are now commonly used to prevent corrosion, but most of them are not effective against the biofilms, and they are toxic and not degradable. Biocides easily kill corrosive bacteria, which are as the planktonic and sessile population, but they are not effective against biofilm. New antimicrobial and eco-friendly substances are now being developed. Biosurfactants are proved to be one of the best eco-friendly anticorrosion substances to inhibit the biocorrosion process and protect materials against corrosion. Biosurfactants have recently became one of the important products of bioeconomy with multiplying applications, while there is scare knowledge on their using in biocorrosion treatment. In this review, the recent findings on the application of biosurfactants as eco-friendly and innovative biocides against biocorrosion are highlighted.

Investigation of Biogenic Passivating Layers on Corroded Iron

This study evaluates mechanisms of biogenic mineral formation induced by bacterial iron reduction for the stabilization of corroded iron. As an example, the Desulfitobacterium hafniense strain TCE1 was employed to treat corroded coupons presenting urban natural atmospheric corrosion, and spectroscopic investigations were performed on the samples’ cross-sections to evaluate the corrosion stratigraphy. The treated samples presented a protective continuous layer of iron phosphates (vivianite Fe²⁺₃(PO₄)₂·8H₂O and barbosalite Fe²⁺Fe³⁺₂(PO₄)₂(OH)₂), which covered 92% of the surface and was associated with a decrease in the thickness of the original corrosion layer. The results allow us to better understand the conversion of reactive corrosion products into stable biogenic minerals, as well as to identify important criteria for the design of a green alternative treatment for the stabilization of corroded iron.

Hexagonal Boron Nitride: The Thinnest Insulating Barrier to Microbial Corrosion

We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V ( vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as polyaniline. In addition to impermeability, the insulating nature of SL-hBN suppresses galvanic effects and improves its ability to combat microbial corrosion.

Souring control in fluid samples of oil industry using a multiple ligand simultaneous docking (MLSD) strategy

We have used docking techniques in order to propose potential inhibitors to the enzymes adenosine phosphosulfate reductase and adenosine triphosphate sulfurylase that are responsible, among other deleterious effects, for causing souring of oil and gas reservoirs. Three candidates selected through molecular docking revealed new and improved polar and hydrophobic interactions with the above-mentioned enzymes. Microbiological laboratory assays performed subsequently corroborated the results of computer modelling that the three compounds can efficiently control the biogenic sulfide production.

Characterization of Corrosive Bacterial Consortia Isolated from Water in a Cooling Tower

An analysis of a culturable corrosive bacterial community in water samples from a cooling tower was performed using traditional cultivation techniques and its identification based on 16S rRNA gene sequence. Seven aerobic bacterial species were identified: Pseudomonas putida ARTYP1, Pseudomonas aeruginosa ARTYP2, Massilia timonae ARTYP3, Massilia albidiflava ARTYP4, Pseudomonas mosselii ARTYP5, Massilia sp. ARTYP6, and Pseudomonas sp. ARTYP7. Although some of these species have commonly been observed and reported in biocorrosion studies, the genus Massilia is identified for the first time in water from a cooling tower. The biocorrosion behaviour of copper metal by the new species Massilia timonae ARTYP3 was selected for further investigation using a weight loss method, as well as electrochemical and surface analysis techniques (SEM, AFM, and FTIR). In contrast with an uninoculated system, thin bacterial biofilms and pitting corrosion were observed on the copper metal surface in the presence of M. timonae. The use of a biocide, bronopol, inhibited the formation of biofilm and pitting corrosion on the copper metal surface.

Microbial Corrosion of API 5L X-70 Carbon Steel by ATCC 7757 and Consortium of Sulfate-Reducing Bacteria

Various cases of accidents involving microbiology influenced corrosion (MIC) were reported by the oil and gas industry. Sulfate reducing bacteria (SRB) have always been linked to MIC mechanisms as one of the major causes of localized corrosion problems. In this study, SRB colonies were isolated from the soil in suspected areas near the natural gas transmission pipeline in Malaysia. The effects of ATCC 7757 and consortium of isolated SRB upon corrosion on API 5L X-70 carbon steel coupon were investigated using a weight loss method, an open circuit potential method (OCP), and a potentiodynamic polarization curves method in anaerobic conditions. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were then used to determine the corrosion morphology in verifying the SRB activity and corrosion products formation. Results from the study show that the corrosion rate (CR) of weight loss method for the isolated SRB is recorded as 0.2017 mm/yr compared to 0.2530 mm/yr for ATCC 7757. The Tafel plot recorded the corrosion rate of 0.3290 mm/yr for Sg. Ular SRB and 0.2500 mm/yr forDesulfovibrio vulgaris. The results showed that the consortia of isolated SRB were of comparable effects and features with the single ATCC 7757 strain.

Current and emerging environmentally-friendly systems for fouling control in the marine environment

Following the ban in 2003 on the use of tributyl-tin compounds in antifouling coatings, the search for an environmentally-friendly alternative has accelerated. Biocidal TBT alternatives, such as diuron and Irgarol 1051®, have proved to be environmentally damaging to marine organisms. The issue regarding the use of biocides is that concerning the half-life of the compounds which allow a perpetuation of the toxic effects into the marine food chain, and initiate changes in the early stages of the organisms' life-cycle. In addition, the break-down of biocides can result in metabolites with greater toxicity and longevity than the parent compound. Functionalized coatings have been designed to repel the settlement and permanent attachment of fouling organisms via modification of either or both surface topography and surface chemistry, or by interfering with the natural mechanisms via which fouling organisms settle upon and adhere to surfaces. A large number of technologies are being developed towards producing new coatings that will be able to resist biofouling over a period of years and thus truly replace biocides as antifouling systems. In addition urgent research is directed towards the exploitation of mechanisms used by living organisms designed to repel the settlement of fouling organisms. These biomimetic strategies include the production of antifouling enzymes and novel surface topography that are incompatible with permanent attachment, for example, by mimicking the microstructure of shark skin. Other research seeks to exploit chemical signals and antimicrobial agents produced by diverse living organisms in the environment to prevent settlement and growth of fouling organisms on vulnerable surfaces. Novel polymer-based technologies may prevent fouling by means of unfavourable surface chemical and physical properties or by concentrating antifouling compounds around surfaces.

Novel potential inhibitors for adenylylsulfate reductase to control souring of water in oil industries

The biogenic production of hydrogen sulfide gas by sulfate-reducing bacteria (SRB) causes serious economic problems for natural gas and oil industry. One of the key enzymes important in this biologic process is adenosine phosphosulfate reductase (APSr). Using virtual screening technique we have discovered 15 compounds that are novel potential APSr inhibitors. Three of them have been selected for molecular docking and microbiological studies which have shown good inhibition of SRB in the produced water from the oil industry.

Streptomyces lunalinharesii strain 235 shows the potential to inhibit bacteria involved in biocorrosion processes

Four actinomycete strains previously isolated from Brazilian soils were tested for their antimicrobial activity against Bacillus pumilus LF-4 and Desulfovibrio alaskensis NCIMB 13491, bacteria that are well known to be involved in biofilm formation and biocorrosion. Strain 235, belonging to the species Streptomyces lunalinharesii, inhibited the growth of both bacteria. The antimicrobial activity was seen over a wide range of pH, and after treatment with several chemicals and heat but not with proteinase K and trypsin. The antimicrobial substances present in the concentrated supernatant from growth media were partially characterized by SDS-PAGE and extracellular polypeptides were seen. Bands in the size range of 12 to 14.4 kDa caused antimicrobial activity. Transmission electron microscopy of D. alaskensis cells treated with the concentrated supernatant containing the antimicrobial substances revealed the formation of prominent bubbles, the spherical double-layered structures on the cell membrane, and the periplasmic space completely filled with electron-dense material. This is the first report on the production of antimicrobial substances by actinomycetes against bacteria involved in biocorrosion processes, and these findings may be of great relevance as an alternative source of biocides to those currently employed in the petroleum industry.

Growth and characterization of Escherichia coli DH5α biofilm on concrete surfaces as a protective layer against microbiologically influenced concrete deterioration (MICD)

Biofilms of selected bacteria strains were previously used on metal coupons as a protective layer against microbiologically influenced corrosion of metals. Unlike metal surfaces, concrete surfaces present a hostile environment for growing a protective biofilm. The main objective of this research was to investigate whether a beneficial biofilm can be successfully grown on mortar surfaces. Escherichia coli DH5α biofilm was grown on mortar surfaces for 8 days, and the structure and characteristics of the biofilm were studied using advanced microscopy techniques such as scanning electron microscopy and confocal laser scanning microscopy in combination with fluorescence in situ hybridization, live/dead, extracellular polymer staining, ATP analysis, and membrane filtration. A biofilm layer with a varying thickness of 20-40 μm was observed on the mortar surface. The distribution of live and dead bacteria and extracellular polymers varied with depth. The density of the live population near the mortar surface was the lowest. The bacteria reached their highest density at three fourths of the biofilm depth and then decreased again near the biofilm-liquid interface. Overall, the results indicated a healthy biofilm growth in the chosen growth period of 8 days, and it is expected that longer growth periods would lead to formation of a more resistant biofilm with more coverage of mortar surfaces.

Biofilms: strategies for metal corrosion inhibition employing microorganisms

Corrosion causes dramatic economic loss. Currently widely used corrosion control strategies have disadvantages of being expensive, subject to environmental restrictions, and sometimes inefficient. Studies show that microbial corrosion inhibition is actually a common phenomenon. The present review summarizes recent progress in this novel strategy: corrosion control using beneficial bacteria biofilms. The possible mechanisms may involve: (1) removal of corrosive agents (such as oxygen) by bacterial physiological activities (e.g., aerobic respiration), (2) growth inhibition of corrosion-causing bacteria by antimicrobials generated within biofilms [e.g., sulfate-reducing bacteria (SRB) corrosion inhibition by gramicidin S-producing Bacillus brevis biofilm], (3) generation of protective layer by biofilms (e.g., Bacillus licheniformis biofilm produces on aluminum surface a sticky protective layer of gamma-polyglutamate). Successful utilization of this novel strategy relies on advances in study at the interface of corrosion engineering and biofilm biology.

Corrosion risk associated with microbial souring control using nitrate or nitrite

Souring, the production of hydrogen sulfide by sulfate-reducing bacteria (SRB) in oil reservoirs, can be controlled through nitrate or nitrite addition. To assess the effects of this containment approach on corrosion, metal coupons were installed in up-flow packed-bed bioreactors fed with medium containing 8 mM sulfate and 25 mM lactate. Following inoculation with produced water to establish biogenic H(2)S production, some bioreactors were treated with 17.5 mM nitrate or up to 20 mM nitrite, eliminating souring. Corrosion rates were highest near the outlet of untreated bioreactors (up to 0.4 mm year(-1)). Nitrate (17.5 mM) eliminated sulfide but gave pitting corrosion near the inlet of the bioreactor, whereas a high nitrite dose (20 mM) completely eliminated microbial activity and associated corrosion. More gradual, step-wise addition of nitrite up to 20 mM resulted in the retention of microbial activity and localized pitting corrosion, especially near the bioreactor inlet. We conclude that: (1) SRB control by nitrate or nitrite reduction shifts the corrosion risk from the bioreactor outlet to the inlet (i.e. from production to injection wells) and (2) souring treatment by continuous addition of a high inhibitory nitrite dose is preferable from a corrosion-prevention point of view.