MICROBIOLOGICALLY INFLUENCED CORROSION OF CARBON STEEL IN SULFIDOGENIC ENVIRONMENTS: THE LINK TO THIOSULFATE REDUCTION AND BIOLOGICAL STABILITY OF ALTERNATIVE FUELS

Biocorrosion or microbiologically influenced corrosion (MIC) refers to the mutiple underlying mechanisms wherein microbial activity directly or indirectly enhances the corrosion of metallic and non-metallic materials. Biocorrosion associated with metallic materials (e.g., carbon steel) is notoriously known for causing costly damage in both the upstream and downstream energy infrastructure, often with catastrophic environmental consequences. While numerous mechanisms are known or have been proposed for this long-standing problem, a thorough fundamental understanding of biocorrosion is still lacking and therefore no panacea exists for the diagnosis and treatment of this complicated process. The first two chapters of this dissertation focus on the biocorrosion of carbon steel in upstream operations by the dominant thiosulfate reducing bacteria (TRB) cultivated from hot oil pipelines or from high salinity produced water after the hydraulic fracturing of shale formations. The last two chapters deal with an assessment of the biological stability of second-generation and next-generation biofuels and their impact on corrosion of carbon steel in the downstream fueling infrastructure. It is well recognized that microorganisms can corrode metallic surfaces under diverse conditions with a combination of different electron donors and acceptors. Historically, the importance of sulfate-reducing bacteria (SRB) in biocorrosion processes has been well documented, but it is entirely possible that other important groups of microorganisms also play crucial roles in catalyzing this activity. We found that TRB were more numerically abundant than SRB in a “PIG” sample from a hot oil pipeline on Alaska’s North Slope. The thiosulfate-reducing and methanogenic enrichments cultivated from this sample were dominated by thermophiles from the genus of Anaerobaculum. The corrosion assay indicated that sulfidogenesis coupled to the thiosulfate-reducing enrichment was more aggressive in exacerbating the corrosion of carbon steel relative to the methanogenic enrichment. This work highlighted the importance of fermentative, thiosulfate-reducing bacteria in the corrosion of oil pipelines under thermophilic conditions. In contrast, methanogenic processes coupled to either complex organic matter metabolism or the metal itself was far less important in catalyzing the corrosion of carbon steel. An exploration of the microbial ecology of highly saline produced water systems from a hydraulic fractured shale gas production facility was also carried out. A molecular survey revealed that the microbial community of this produced water system was predominated by halophilic bacteria affiliated with the genus Halanaerobium. We further hypothesized that these organisms played important roles in carbon and sulfur cycling in the fractured shale formations and contributed to corrosion through sulfide and acid production. One of the dominant microorganisms (Halanaerobium sp., strain DL-01) was isolated and found to degrade guar gum, the major gelling agent in the fracture fluid and produce acetate and sulfide when thiosulfate was served as a terminal electron acceptor. A corrosion scenario in this hydraulically fractured site was tentatively proposed based on the metabolic capacity of Halanaerobium sp. DL-01 and the well-known corrosivity of acetate and sulfide in oil and gas industry. This work mainly implicated that sulfide and acetate produced by fermentative, thiosulfate-reducing halophiles in the deep fractured subsurface may contribute to corrosion in the downstream gas pipelines and storage. Apart from the conventional corrosion problems associated with upstream energy facilities in the oil and gas industry, the increasing global interest in the adoption of alternative fuels raised new issues about the compatibility of emerging biofuels with the existing carbon-steel infrastructure. A protocol was developed to comprehensively assess the biological stability of fuels and applied to the study of second-generation biofuels (camelina-JP5 and FT-F76). That is, the biodegradability of the fuels as well as their potential to exacerbate carbon steel biocorrosion was assessed using three coastal seawaters as starting inocula. The highest sulfate reduction rates were always associated with camelina-JP5, a finding that suggested that this hydroprocessed fuel might be more susceptible to biodegradation relative to other fuels. Metabolite profiling attested to the anaerobic metabolism of n-alkanes and alkylbenzenes in the fuel. The relatively strong linear correlation between sulfate reduction and corrosion (both general and pitting corrosion) suggested that biogenic sulfide production linked to anaerobic metabolism of fuel constitutes can largely account for the increased biocorrosion in marine environments. An important implication of this work was that caution should be exerted with the use of hydroprocessed camelina-JP5 during long term storage due to its relative liability. While numerous efforts are still underway toward the development of second generation alternative fuels, next generation biofuels such as terpene dimer fuel (TDF) have recently been synthesized. This fuel was designed to meet the demand for a high-density biofuel that might be used in conjunction with petroleum fuels. It was hypothesized that TDF might resist anaerobic biodegradation due to the dimerization and hydrogenation of the parent substrates. Using the same protocol, it was found that TDF was relatively recalcitrant and had negligible influence on corrosion over an extended incubation period. These results suggest that this synthetic biofuel might be safe with respect to corrosion of carbon steel but may raise environmental concerns due to its relative persistence under anaerobic conditions should it ever be spilled. Given the well-recognized importance of surface inclusions as sites for pit initiation, the relationship between the manganese dissolution from the metal and pitting corrosion in TDF-laden environments was investigated. The low manganese (Mn)/weight loss value differentially associated with coupons exhibiting a greater degree of pitting corrosion substantiated the hypothesis that this ratio is potentially useful as an indicator of this important corrosion process

Permafrost Active Layer Microbes From Ny Ålesund, Svalbard (79°N) Show Autotrophic and Heterotrophic Metabolisms With Diverse Carbon-Degrading Enzymes

The active layer of permafrost in Ny Ålesund, Svalbard (79°N) around the Bayelva River in the Leirhaugen glacier moraine is measured as a small net carbon sink at the brink of becoming a carbon source. In many permafrost-dominating ecosystems, microbes in the active layers have been shown to drive organic matter degradation and greenhouse gas production, creating positive feedback on climate change. However, the microbial metabolisms linking the environmental geochemical processes and the populations that perform them have not been fully characterized. In this paper, we present geochemical, enzymatic, and isotopic data paired with 10 Pseudomonas sp. cultures and metagenomic libraries of two active layer soil cores (BPF1 and BPF2) from Ny Ålesund, Svalbard, (79°N). Relative to BPF1, BPF2 had statistically higher C/N ratios (15 ± 1 for BPF1 vs. 29 ± 10 for BPF2; n = 30, p < 10–5), statistically lower organic carbon (2% ± 0.6% for BPF1 vs. 1.6% ± 0.4% for BPF2, p < 0.02), statistically lower nitrogen (0.1% ± 0.03% for BPF1 vs. 0.07% ± 0.02% for BPF2, p < 10–6). The d13C values for inorganic carbon did not correlate with those of organic carbon in BPF2, suggesting lower heterotrophic respiration. An increase in the δ13C of inorganic carbon with depth either reflects an autotrophic signal or mixing between a heterotrophic source at the surface and a lithotrophic source at depth. Potential enzyme activity of xylosidase and N-acetyl-β-D-glucosaminidase increases twofold at 15°C, relative to 25°C, indicating cold adaptation in the cultures and bulk soil. Potential enzyme activity of leucine aminopeptidase across soils and cultures was two orders of magnitude higher than other tested enzymes, implying that organisms use leucine as a nitrogen and carbon source in this nutrient-limited environment. Besides demonstrating large variability in carbon compositions of permafrost active layer soils only ∼84 m apart, results suggest that the Svalbard active layer microbes are often limited by organic carbon or nitrogen availability and have adaptations to the current environment, and metabolic flexibility to adapt to the warming climate.Peer Reviewe

An electroporation chip based on flexible microneedle array for in vivo nucleic acid delivery

This paper reports a flexible microneedle array (MNA) electroporation chip for in vivo nucleic acid delivery, which is of great importance for gene therapy. Silicon MNA is proposed to penetrate the high-resistant stratum corneum, while a flexible parylene substrate is used to fit the natural shape of electroporated objects. The chip provides a sufficient electrical field beneath the skin for electroporation with low voltage, which is less likely to harm tissues. Using the proposed chip, we successfully achieved plasmid DNA expression and siRNA delivery in living tissue with low voltage (30-40V). Neither physical nor biological harm to skin was observed. ? 2014 IEEE.EICPCI-S(ISTP)

Investigation and analysis of the current situation of programming education in primary and secondary schools

With the rapid development of the era of artificial intelligence, the application ability of programming is also highlighted. As one of the necessary abilities of social talents in the future, primary and secondary schools pay more and more attention to this, and programming education is also in full swing. Therefore, based on previous studies, this paper further clarifies the current situation when the current situation of programming education in primary and secondary schools is ambiguous. This paper is aimed at a wide range of primary and secondary school teachers. With 1500 teachers who participated in the online training class for programming teachers as the object in Chinese primary, middle and high school stages, mainly from the three levels of schools, teachers, and students. The questionnaire with good reliability and validity test was used as the research method, the survey data were statistically described and analyzed, and differences were analyzed using Microsoft Excel2019, SPSS26.0 and so on, it investigates and analyzes the current situation of programming education in primary and secondary schools. Results indicate that the overall quality of programming education offerings in elementary and secondary schools is subpar, and the construction of programming education curriculum in schools requires improvement. Nevertheless, schools prioritize improving students' comprehensive abilities, and teachers hold a positive attitude towards programming education and teaching. Although students demonstrate a strong interest in learning, their foundation is weak, resulting in poor learning outcomes. Consequently, the author provides specific recommendations regarding programming education's working mechanism, curriculum standard system, teacher training, and educational resources sharing to better develop programming education in primary and secondary schools

Genome-centric resolution of novel microbial lineages in an excavated Centrosaurus dinosaur fossil bone from the Late Cretaceous of North America

Background: Exceptional preservation of endogenous organics such as collagens and blood vessels has been frequently reported in Mesozoic dinosaur fossils. The persistence of these soft tissues in Mesozoic fossil bones has been challenged because of the susceptibility of proteins to degradation and because bone porosity allows microorganisms to colonize the inner microenvironments through geological time. Although protein lability has been studied extensively, the genomic diversity of microbiomes in dinosaur fossil bones and their potential roles in bone taphonomy remain underexplored. Genome-resolved metagenomics was performed, therefore, on the microbiomes recovered from a Late Cretaceous Centrosaurus bone and its encompassing mudstone in order to provide insight into the genomic potential for microbial alteration of fossil bone. Results: Co-assembly and binning of metagenomic reads resulted in a total of 46 high-quality metagenomeassembled genomes (MAGs) affiliated to six bacterial phyla (Actinobacteria, Proteobacteria, Nitrospira, Acidobacteria, Gemmatimonadetes and Chloroflexi) and 1 archaeal phylum (Thaumarchaeota). The majority of the MAGs represented uncultivated, novel microbial lineages from class to species levels based on phylogenetics, phylogenomics and average amino acid identity. Several MAGs from the classes Nitriliruptoria, Deltaproteobacteria and Betaproteobacteria were highly enriched in the bone relative to the adjacent mudstone. Annotation of the MAGs revealed that the distinct putative metabolic functions of different taxonomic groups were linked to carbon, nitrogen, sulfur and iron metabolism. Metaproteomics revealed gene expression from many of the MAGs, but no endogenous collagen peptides were identified in the bone that could have been derived from the dinosaur. Estimated in situ replication rates among the bacterial MAGs suggested that most of the microbial populations in the bone might have been actively growing but at a slow rate. Conclusions: Our results indicate that excavated dinosaur bones are habitats for microorganisms including novel microbial lineages. The distinctive microhabitats and geochemistry of fossil bone interiors compared to that of the external sediment enrich a microbial biomass comprised of various novel taxa that harbor multiple gene sets related to interconnected biogeochemical processes. Therefore, the presence of these microbiomes in Mesozoic dinosaur fossils urges extra caution to be taken in the science of paleontology when hunting for endogenous biomolecules preserved from deep time

Anaerobic biodegradation of biofuels and their impact on the corrosion of a Cu-Ni alloy in marine environments

Fuel biodegradation linked to sulfate reduction can lead to corrosion of the metallic infrastructure in a variety of marine environments. However, the biological stability of emerging biofuels and their potential impact on copper-nickel alloys commonly used in marine systems has not been well documented. Two potential naval biofuels (Camelina-JP5 and Fisher-Tropsch-F76) and their petroleum-derived counterparts (JP5 and F76) were critically assessed in seawater/sediment incubations containing a metal coupon (70/30 Cu-Ni alloy). Relative to a fuel-unamended control (1.2 +/- 0.4 mu M/d), Camelina-JP5 (86.4 +/- 1.6 mu M/ d) and JP5 (77.6 +/- 8.3 M/d) stimulated much higher rates of sulfate reduction than either FT-F76 (11.4 +/- 2.7 mu M/d) or F76 (38.4 +/- 3.7 mu M/d). The general corrosion rate (r(2) = 0.91) and pitting corrosion (r(2) = 0.92) correlated with sulfate loss in these incubations. Despite differences in microbial community structure on the metal or in the aqueous or sediment phases, sulfate reducing bacteria affiliated with Desulfarculaceae and Desulfobacteraceae became predominant upon fuel amendment. The identification of alkylsuccinates and alkylbenzylsuccinates attested to anaerobic metabolism of fuel hydrocarbons. Sequences related to Desulfobulbaceae were highly enriched (34.2-64.8%) on the Cu-Ni metal surface, regardless of whether the incubation received a fuel amendment. These results demonstrate that the anaerobic metabolism of biofuel linked to sulfate reduction can exacerbate the corrosion of Cu-Ni alloys. Given the relative lability of Camelina-JP5, particular precaution should be taken when incorporating this hydroprocessed biofuel into marine environments serviced by a Cu-Ni metallic infrastructure. (C) 2017 Elsevier Ltd. All rights reserved

Anaerobic Biodegradation of Alternative Fuels and Associated Biocorrosion of Carbon Steel in Marine Environments

Fuels that biodegrade too easily can exacerbate through-wall pitting corrosion of pipelines and tanks and result in unintentional environmental releases. We tested the biological stability of two emerging naval biofuels (camelina-JP5 and Fischer-Tropsch-F76) and their potential to exacerbate carbon steel corrosion in seawater incubations with and without a hydrocarbon-degrading sulfate-reducing bacterium. The inclusion of sediment or the positive control bacterium in the incubations stimulated a similar pattern of sulfate reduction with different inocula. However, the highest rates of sulfate reduction were found in incubations amended, with camelina-JPS [(57.2 +/- 2.2)-(80.8 +/- 8.1) mu M/day] or its blend with petroleum-JPS (76.7 +/- 2.4 mu M/day). The detection of a suite of metabolites only in the fuel-amended incubations confirmed that alkylated benzene hydrocarbons were metabolized via known anaerobic mechanisms. Most importantly, general (r(2) = 0.73) and pitting (r(2) = 0.69) corrosion were positively correlated with sulfate loss in the incubations. Thus, the anaerobic biodegradation of labile fuel components coupled with sulfate respiration greatly contributed to the biocorrosion of carbon steel. While all fuels were susceptible to anaerobic metabolism, special attention should be given to camelina-JPS biofuel due to its relatively rapid biodegradation. We recommend that this biofuel be used with caution and that whenever possible extended storage periods should be avoided

Metagenome-assembled genomes from active layer in Ny Ålesund, Svalbard (79°N) show population dynamics related to seasonal thawing and soil depth

The active layer of permafrost in Ny Ålesund, Svalbard (79°N), is increasing in thickness at a rate of ~one vertical centimeter per year in most locations around the Bayelva River in the Leirhaugen glacier moraine. Microbes in the active layers may drive organic carbon degradation and greenhouse gas production, creating a positive feedback on climate change. However, the microbial metabolisms relating to the environmental geochemistry and population dynamics have not been well characterized. We tested if organismal abundance was related to site or stratigraphy by analyzing metagenome assembled genomes (MAGs) from 56 highly resolved intervals of five active layer permafrost sites. Two sites were collected in the winter time (April 2018) and three were collected in the summer (September 2019). The MAGs’ read recruitment to metagenome libraries showed an Actinobacteria population that was dominant when the soils were thawed (September 2019) and when the surface soil were covered in snow (April 2018). Inversely, another group of Actinobacteria dominated the deeper depths while the soils were frozen and were nearly absent during the thawed/summer season. We show that microbial populations in the Svalbard active layer shift by depth and season, maintaining populations of continuously metabolically active microbes at all depths, year-round