Interaction of desulfovibrio desulfuricans biofilms with stainless steel surface and its impact on bacterial metabolism

Aims: To study the influence of some metallic elements of stainless steel 304 (SS 304) on the development and activity of a sulfate-reducing bacterial biofilm, using as comparison a reference nonmetallic material polymethylmethacrylate (PMMA). Methods and Results: Desulfovibrio desulfuricans biofilms were developed on SS 304 and on a reference nonmetallic material, PMMA, in a flow cell system. Steady-state biofilms were metabolically more active on SS 304 than on PMMA. Activity tests with bacteria from both biofilms at steady state also showed that the doubling time was lower for bacteria from SS 304 biofilms. The influence of chromium and nickel, elements of SS 304 composition, was also tested on a cellular suspension of Des. desulfuricans. Nickel decreased the bacterial doubling time, while chromium had no significant effect. Conclusions: The following mechanism is hypothesized: a Des. desulfuricans biofilm grown on a SS 304 surface in anaerobic conditions leads to the weakening of the metal passive layer and to the dissolution in the bulk phase of nickel ions that have a positive influence on the sulfate-reducing bacteria metabolism. This phenomenon may enhance the biocorrosion process. Significance and Impact of the Study: A better understanding of the interactions between metallic surfaces such as stainless steel and bacteria commonly implied in the corrosion phenomena which is primordial to fight biocorrosion.Programme Praxis XXI; University of Santiago de Compostela

An overview on the reactors to study drinking water biofilms

The development of biofilms in drinking water distribution systems (DWDS) can cause pipe degradation, changes in the water organoleptic properties but the main problem is related to the public health. Biofilms are the main responsible for the microbial presence in drinking water (DW) and can be reservoirs for pathogens. Therefore, the understanding of the mechanisms underlying biofilm formation and behavior is of utmost importance in order to create effective control strategies. As the study of biofilms in real DWDS is difficult, several devices have been developed. These devices allow biofilm formation under controlled conditions of physical (flow velocity, shear stress, temperature, type of pipe material, etc), chemical (type and amount of nutrients, type of disinfectant and residuals, organic and inorganic particles, ions, etc) and biological (composition of microbial community e type of microorganism and characteristics) parameters, ensuring that the operational conditions are similar as possible to the DWDS conditions in order to achieve results that can be applied to the real scenarios. The devices used in DW biofilm studies can be divided essentially in two groups, those usually applied in situ and the bench top laboratorial reactors. The selection of a device should be obviously in accordance with the aim of the study and its advantages and limitations should be evaluated to obtain reproducible results that can be transposed into the reality of the DWDS. The aim of this review is to provide an overview on the main reactors used in DW biofilm studies, describing their characteristics and applications, taking into account their main advantages and limitations.This work was supported by the Operational Programme for Competitiveness Factors COMPETE and by Portuguese Foundation for Science and Technology through Project Phyto disinfectants - PTDC/DTPSAP/1078/2012 (COMPETE: FCOMP-01-0124-FEDER-028765), the Post-Doc grant awarded to Lucia Simoes (SFRH/BPD/81982/2011). Also, this work was undertaken as part of the European Research Project SUS-CLEAN (Contract n_FP7-KBBE-2011-5, project number: 287514) and the COST Action FA1202. The authors are solely responsible for this work. It does not represent the opinion of the Community, and the Community is not responsible for any use that might be made of data appearing herein

Microbially-influenced corrosion: Damage to prostheses, delight for bacteria

In natural and man-made environments, microbial communities thrive as biofilms on living (e.g. tissue) and inanimate (e.g. plastic, metal, wood, mineral) surfaces. Biofilms are found in a wide range of aqueous habitats, including physiological fluids. Numerous types of microorganisms are able to colonize catheters, implants, prosthetics, and other medical devices manufactured from different metallic and non-metallic materials dwelling within a human body. The development of biofilm is facilitated by the production of extracellular polymeric substances (EPS). Biofilms formed on surfaces of metallic materials may alter interfacial electrochemical processes, which can lead to increased corrosion of the colonized substratum. Deterioration of metallic materials in the presence of a biofilm is termed biocorrosion or microbially-influenced corrosion (MIC). In the field of biomaterials, ""biocorrosion"" is commonly used when describing the effect of host tissue on the corrosion of implant metals and alloys. Therefore, to avoid confusion, we will here use the term MIC as a reference to biofilm-influenced corrosion. It is important to realise that although most metals are prone to microbial colonization, i.e. to biofouling, this does not imply that they are susceptible to MIC. For example, a metal such as titanium, accumulates biofilm, however, it still demonstrates excellent resistance against MIC. Corrosion is, by definition, an electrochemical process, therefore, electrochemical techniques are frequently employed to determine and measure the rate of abiotic, as well as biologically driven corrosion reactions. This communication addresses the use of electrochemical techniques for monitoring (i) biofilm formation on and (ii) MIC of implant metals and alloys

Fault Tree Analysis for Fungal Corrosion of Coated Aluminum

A fault tree methodology has been used to analyze the combinations of basic factors involved in fungal degradation and corrosion. The purpose was to demonstrate the identification of mitigation actions for reducing the risk of fungal corrosion of coated aluminum in aircraft. The interaction between fungal-induced degradation processes and coatings is described, and the methodology of the fault tree analysis (FTA) is presented. The interconnection of the basic factors through conventional AND and OR logic gates in the fault tree structure reveals vulnerabilities and potential failure pathways in the system. Mitigation actions can be directed at these basic factors to reduce or eliminate failure pathways, thereby reducing the overall risk of fungal-induced corrosion. Potential applications of FTA for corrosion mitigation, design and materials selection, and failure analysis are presented

Biofilm formation on metal surfaces

SIGLEAvailable from British Library Document Supply Centre- DSC:DX91672 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Changes in mechanical properties of dental alloys induced by saliva and oral probiotic supplements

The effects of the saliva and oral probiotic supplements on roughness, friction and microhardness of the stainless steel (SS) and nickel-titanium (NiTi) alloys used in dentistry was studied. The specimens of stainless steel, uncoated, rhodium-coated and nitrided NiTi were exposed to artificial saliva with pH 4.8 and artificial saliva with addition of probiotic supplements containing bacteria Lactobacillus reuteri Prodentis through 28 days. First 5 days specimens were subjected to thermocycling to simulate intraoral conditions, 2500 cycles from 5 °C to 50 °C and the following days to the temperature of the 37±2 °C. Analyses demonstrated that oral probiotic supplements do not influence microhardness, roughness or friction of stainless steel above the influence of saliva. Probiotics increase roughness in NiTi, but without significant influence on friction, while microhardness in NiTi is not influenced. Surface nitriding reduces the influence of probiotics on roughness while rhodium coating increases itDie Einflüsse des Speichels und oraler Probiotika auf die Rauigkeit, Reibung und Mikrohärte von Edelstahl und Nickel-Titan-Legierungen, die in der Zahnmedizin angewendet werden, wurden untersucht. Es wurden unbeschichtete und Rhodium beschichtete Edelstahlproben sowie nitrierte Nickel-Titan-Legierungen bei den Versuchen berücksichtigt. Die Proben wurden künstlichem Speichel mit pH 4,8 ausgesetzt und dem Speichel mit Zusatz von Probiotikum, der das Bakterium Lactobacillus reuteri Prodentis enthält, für 28 Tage ausgesetzt. Für die ersten 5 Tage wurden die Proben mit 2500 Zyklen von 5 °C bis 50 °C thermocycliert, um die intraoralen Umstände zu simulieren und die nächsten Tage bei der Temperatur von 37�2 °C. Die Analysen bzw. Ergebnisse zeigen, dass die oralen Probiotika die Rauigkeit, Reibung und Mikrohärte des Edelstahls nicht mehr beeinflussen als Speichel. Die Probiotika vergrößern die Rauigkeit der Nickel-Titan-Legierungen, haben aber keinen bedeutsamen Einfluss auf die Reibung und die Mikrohärte der Nickel-Titan-Legierungen. Das Nitrieren der Oberfläche reduziert den Einfluss der Probiotika auf die Rauigkeit während sie die Rauigkeit der Rhodium-Beschichtung vergrößert