Microbe-surface interactions in biofouling and biocorrosion processes

The presence of microorganisms on material surfaces can have a profound effect on materials performance. Surface-associated microbial growth, i.e. a biofilm, is known to instigate biofouling. The presence of biofilms may promote interfacial physico-chemical reactions that are not favored under abiotic conditions. In the case of metallic materials, undesirable changes in material properties due to a biofilm (or a biofouling layer) are referred to as biocorrosion or microbially influenced corrosion (MIC). Biofouling and biocorrosion occur in aquatic and terrestrial habitats varying in nutrient content, temperature, pressure and pH. Interfacial chemistry in such systems reflects a wide variety of physiological activities carried out by diverse microbial populations thriving within biofilms. Biocorrosion can be viewed as a consequence of coupled biological and abiotic electron-transfer reactions, i.e. redox reactions of metals, enabled by microbial ecology. Microbially produced extracellular polymeric substances (EPS), which comprise different macromolecules, mediate initial cell adhesion to the material surface and constitute a biofilm matrix. Despite their unquestionable importance in biofilm development, the extent to which EPS contribute to biocorrosion is not well-understood. This review offers a current perspective on material/microbe interactions pertinent to biocorrosion and biofouling, with EPS as a focal point, while emphasizing the role atomic force spectroscopy and mass spectrometry techniques can play in elucidating such interactions. [Int Microbiol 2005; 8(3):157-168

Metabolomic and high-throughput sequencing analysis—modern approach for the assessment of biodeterioration of materials from historic buildings

Preservation of cultural heritage is of paramount importance worldwide. Microbial colonization of construction materials, such as wood, brick, mortar and stone in historic buildings can lead to severe deterioration. The aim of the present study was to give modern insight into the phylogenetic diversity and activated metabolic pathways of microbial communities colonized historic objects located in the former Auschwitz II-Birkenau concentration and extermination camp in Oświęcim, Poland. For this purpose we combined molecular, microscopic and chemical methods. Selected specimens were examined using Field Emission Scanning Electron Microscopy (FESEM), metabolomic analysis and high-throughput Illumina sequencing. FESEM imaging revealed the presence of complex microbial communities comprising diatoms, fungi and bacteria, mainly cyanobacteria and actinobacteria, on sample surfaces. Microbial diversity of brick specimens appeared higher than that of the wood and was dominated by algae and cyanobacteria, while wood was mainly colonized by fungi. DNA sequences documented the presence of 15 bacterial phyla representing 99 genera including Halomonas, Halorhodospira, Salinisphaera, Salinibacterium, Rubrobacter, Streptomyces, Arthrobacter and 9 fungal classes represented by 113 genera including Cladosporium, Acremonium, Alternaria, Engyodontium, Penicillium, Rhizopus and Aureobasidium. Most of the identified sequences were characteristic of organisms implicated in deterioration of wood and brick. Metabolomic data indicated the activation of numerous metabolic pathways, including those regulating the production of primary and secondary metabolites, for example, metabolites associated with the production of antibiotics, organic acids and deterioration of organic compounds. The study demonstrated that a combination of electron microscopy imaging with metabolomic and genomic techniques allows to link the phylogenetic information and metabolic profiles of microbial communities and to shed new light on biodeterioration processes

Metabolomic and metagenomic analysis of two crude oil production pipelines experiencing differential rates of corrosion

Corrosion processes in two North Sea oil production pipelines were studied by analyzing pig envelope samples via metagenomic and metabolomic techniques. Both production systems have similar physico-chemical properties and injection waters are treated with nitrate, but one pipeline experiences severe corrosion and the other does not. Early and late pigging material was collected to gain insight into the potential causes for differential corrosion rates. Metabolites were extracted and analyzed via ultra-high performance liquid chromatography/high-resolution mass spectrometry with electrospray ionization (ESI) in both positive and negative ion modes. Metabolites were analyzed by comparison with standards indicative of aerobic and anaerobic hydrocarbon metabolism and by comparison to predicted masses for KEGG metabolites. Microbial community structure was analyzed via 16S rRNA gene qPCR, sequencing of 16S PCR products, and MySeq Illumina shotgun sequencing of community DNA. Metagenomic data were used to reconstruct the full length 16S rRNA genes and genomes of dominant microorganisms. Sequence data were also interrogated via KEGG annotation and for the presence of genes related to terminal electron accepting (TEA) processes as well as aerobic and anaerobic hydrocarbon degradation. Significant and distinct differences were observed when comparing the ‘high corrosion’ (HC) and the ‘low corrosion’ (LC) pipeline systems, especially with respect to the TEA utilization potential. The HC samples were dominated by sulfate-reducing bacteria (SRB) and archaea known for their ability to utilize simple carbon substrates, whereas LC samples were dominated by pseudomonads with the genetic potential for denitrification and aerobic hydrocarbon degradation. The frequency of aerobic hydrocarbon degradation genes was low in the HC system, and anaerobic hydrocarbon degradation genes were not detected in either pipeline. This is in contrast with metabolite analysis, which demonstrated the presence of several succinic acids in HC samples that are diagnostic of anaerobic hydrocarbon metabolism. Identifiable aerobic metabolites were confined to the LC samples, consistent with the metagenomic data. Overall, these data suggest that corrosion management might benefit from a more refined understanding of microbial community resilience in the face of disturbances such as nitrate treatment or pigging, which frequently prove insufficient to alter community structure toward a stable, less-corrosive assemblage.This work was supported in part by grants from the University of Oklahoma Biocorrosion Center, the National Science Foundation (OCE 1634630 and MCB 1329890) and BP (The Gulf of Mexico Research Initiative, Project No. 130206). The instrumentation for the metabolomic analysis was funded by ONR through a DURIP grant (Award no. N000140910797), and the method development by ONR through a MURI grant (Award no. N000141010946).Ye

An activated carbon substrate surface for laser desorption mass spectrometry

AbstractA method to obtain laser desorption/ionization mass spectra of organic compounds by depositing sample solutions onto a carbon substrate surface is demonstrated. The substrate consists of a thin layer of activated carbon particles immobilized on an aluminum support. In common with the porous carbon suspension samples used in previous “surface-assisted laser desorption/ionization” (SALDI) work, the mass spectra contain only a few “matrix” background ion peaks, minimizing interference with analyte ion peaks. The presence of glycerol ensured that the ion signals were stable over hundreds of laser shots. In addition, the carbon substrate surface has several advantages over the suspension samples. The use of a very thin layer of carbon significantly improves the sensitivity. Detection limits range from attomoles for crystal violet to femtomoles for bradykinin. Very little sample preparation is required as the analyte solution is simply pipetted onto the substrate surface and glycerol added. When using an alternate sample deposition method, a mass resolution for bradykinin of 1800 is achieved in linear time-of-flight mode. This is close to the resolution limit set by the detector system and above instrument specification for matrix-assisted laser desorption/ionization mass spectra

Space-Charge-Dominated Mass Spectrometry Ion Sources: Modeling and Sensitivity

AbstractThe factors determining the sensitivity of space-charge-dominated (SCD) unipolar ion sources, such as electrospray (ESP) and corona atmospheric pressure ionization (API) have been studied theoretically. The most important parameters are the ion density and ion drift time in the vicinity of the sampling orifice. These are obtained by solving a system of differential equations, “the space-charge problem.” For some simple geometries, analytical solutions are known. For a more realistic “needle-in-can” geometry, a solution to the space-charge problem was obtained using a finite-element method. The results illustrate some general characteristics of SCD ion sources. It is shown that for typical operating conditions the minimum voltage required to overcome the space-charge effect in corona API or ESP ion sources constitutes a dominant or significant fraction of total applied voltage. Further, the electric field and the ion density in the region of the ion-sampling orifice as well as the ion residence time in the source are determined mainly by the space charge. Finally, absolute sensitivities of corona API ion sources were calculated by using a geometry-independent treatment of space charge

Denaturation of Lysozyme and Myoglobin in Laser Spray

In laser spray, the tip of an electrospray capillary is irradiated with a continuous CO2 laser beam. Here, we report results from a modified laser spray method that employs a relatively low laser irradiance level. With a laser power of ∼2 W and a focal spot size (∼0.3 mm), which covered the entire front surface of the electrospray capillary, the irradiance was ∼3 × 103 W/cm2. This resulted in a quiescent and smooth vaporization of aqueous solutions. This “evaporation-mode” laser spray method yielded the best results so far obtained in our laboratory with laser-irradiated electrospray, producing higher and more stable signals. The method was applied to the analysis of aqueous solutions of lysozyme and myoglobin. Mass spectra were obtained as a function of laser power from 0 W (electrospray) to ∼2 W. The spray generated at the tip of the stainless steel capillary was observed with a CCD camera. With increase of laser power, the droplets in the spray became finer and the Taylor cone became progressively smaller. The strongest ion signals were recorded when the sample solution protruded only slightly from the tip of the capillary. A broadening of the lysozyme charge-state distribution, attributable to protein unfolding, was observed with a laser power of 2 W. No denaturation of myoglobin took place up to a laser power of 1.6 W. However, a sudden onset of denaturation was observed at 1.8 W as a broadening of the myoglobin charge distribution and the appearance of apo-myoglobin peaks. These findings demonstrate that laser spray is capable of dissociating the noncovalent complexes selectively without breaking covalent bonds

Transfer of bacteria between stainless steel and chicken meat: A CLSM and DGGE study of biofilms

This study aimed to assess the interaction between bacteria and food processing surfaces using novel methods. Microbial cross contamination between stainless steel, a common food processing material, and raw chicken was studied using microbiological culture, specialized microscope and molecular techniques. Confocal laser scanning microscopy (CLSM) allowed the visualization of biofilms containing single or dual species of Escherichia coli O157:H7, Salmonella typhimurium, Bacillus cereus, Staphylococcus aureus and Pseudomonas aeruginosa, formed after 6 days’ incubation on stainless steel or 4h on raw chicken. The results provided information on intra-biofilm location and stratification of species within dual species biofilms. Top-to-bottom Z-stack images revealed that, on both materials, S. typhimurium and E. coli attached concurrently, the former in greater numbers. E. coli and B. cereus segregated on steel, E. coli more frequent near the metal surface, B. cereus almost the only species in outer layers. Few cells of S. aureus, found at all depths, were seen in the 2.9 µm thick biofilm on steel with E. coli. Greatest attachment was shown by P. aeruginosa, followed by S. typhimurium, E. coli and finally Gram positive species. Large amounts of EPS in P. aeruginosa biofilms made visualization difficult on both materials, but especially on chicken meat, a limitation of this technique. Nevertheless, CLSM was useful for determining time sequence of adhesion and species makeup of thin biofilms. The technique showed that five min contact between bacterially-contaminated chicken and sterile steel resulted in greatest transfer of P. aeruginosa, followed by S. typhimurium. This was confirmed using DGGE. Gram positive bacteria transferred poorly. A biofilm containing 2.3 × 105  cfu·cm−2 B. cereus on steel transferred an undetectable number of cells to chicken after 5 min contact. This species was unable to form biofilm on chicken when incubated for 4 h in growth medium. S. typhimurium and P.aeruginosas were most efficiently transferred from contaminated steel to raw chicken within 5 min contact, with 20–30% transfer from single species biofilms. All other species, and all cells in dual species biofilms, showed less than 2% transfer. CLSM and DGGE were shown to be useful techniques for the study of bacterial adhesion to stainless steel