Phylogenetic characterization of bacterial consortia obtained of corroding gas pipelines in Mexico

Characterization of the microbial populations formed in gas pipelines is essential to understand the metallic surface-microbe interaction, their role in metal corrosion, and to implement efficient monitoring and control strategies. Microbial community analysis in a corroded gas pipeline in a petroleum-producing facility in the Southeast region in Mexico was performed by traditional cultivation techniques and identification based on 16S rRNA gene sequence. In all samples, thin bacterial biofilms were observed and pitting corrosion was reveled after removing the biofilms. Six pure or mixed cultures of anaerobic bacteria were obtained and their 16S rRNA libraries were constructed, respectively. At least two members of each RFLP profile were sequenced and the phylogenetic affiliations of cloned bacterial 16S rRNA genes indicated that native biofilms were mainly colonized by Desulfovibrio vulgaris and Desulfovibrio desulfuricans, sulfate-reducing bacteria members; Citrobacter freundii, an Enterobacteriaceae member; Clostridium celerecrescens and Clostridium sporogenes, spore-forming anaerobic species and Cetobacterium somerae, a microaerotolerant, non-spore-forming fusobacteria. Some of these species have been observed consistently in other steel pipelines previously, but Cetobacterium members and C. celerecrescens are described for the fist time in this corroded gas pipeline. The potential role of each species in biofilm formation and steel corrosion is discussed.     

Use of dissolved ozone for controlling planktonic and sessile bacteria in industrial cooling systems

Cooling water treatment requires effective, environmentally-safe biocides compatible with system operation. The unique combination of high biocidal activity during use with no toxic discharge, could render dissolved ozone a safe biocide for cooling water treatment. Planktonic and sessile cells of Pseudomonas fluorescens (a frequent microbial contaminant of industrial systems) were used in this work to assess the biocidal effectiveness of ozone. Dissolved ozone showed to be effective at concentrations between 0.1 and 0.3 ppm, to eliminate completely the levels of planktonic cells used in this paper (10⁷–10⁸ cell/ml) within a range of contact times between 10 and 30 min. However, ozone at 0.15 ppm was only able to diminish sessile cell population by two or three orders of magnitude. This minor biocidal effectiveness of ozone against bacterial biofilms is discussed in this paper, taking into account recent concepts on structure and dynamics of biofilms. Different metallic substrata were assayed to verify if there was any effect of metal nature on the biocidal action. Open circuit potentials vs. time experiments and potentiodynamic polarization curves were made for assessing the effect of dissolved ozone on the corrosion behavior of the metals tested.     

Biodeterioration of stone: a review

The alteration and weathering of stone is basically determined by natural and anthropogenic impacts influencing various physical, chemical and biological damage factors at the object site. Whether as direct or catalytically enhancing factor, the biodeterioration of stone is coupled with nearly all environmentally induced degradation processes: the presence of the one makes deterioration by the other all the more effective. The bioreceptivity of stone is described by its structure and chemical composition, while the intensity of the microbial contamination is determined by the referring climatic conditions and the anthropogenic euthrophication of the atmosphere. The microflora improves the nutrient and moisture-restricted growth conditions on building stones by the formation of surface-covering biofilms. Besides the aesthetical impairment caused by the coloured biopatina, the biofouling effect promotes even “abiotic” deterioration processes due to the alteration of the material structure as well as their thermo-hygric properties; in addition, mechanical pressure due to the shrinking and swelling of the colloidal biofilms might cause a further weakening of the mineral lattice. Acidolytic and oxido-reductive biocorrosion processes complete the biodeteriorating attack of stone acting as a preliminary precursor for the latter formation of detrimental crusts. Suitable and reliable methods for the detection of biodeterioration processes are available, but only the interdisciplinary diagnosis and evaluation of the entire decay process of stone allows the formulation of adaequate countermeasure strategies. In case the significance of biodeterioration impacts is proven, the possible effects of the microbial contamination on cleaning procedures, protective treatments as well as biocidal applications has to be considered. This paper will give a comprehensive overview to the biodeterioration of stone and stresses the practical relevance for the conservation.     

The Geological Roles Played by Microfungi in Interaction with Sulfide Minerals from Libiola Mine,Liguria, Italy

The potential role played by fungi in the weathering of sulfide abandoned mines and waste rock dumps is scarcely investigated, yet. In particular microfungi may produce biofilms that work as sites of metals and minerals precipitation. This study aimed to investigate interactions, bioalteration, and biocorrosion between three microfungi (Trichoderma harzianum group, Penicillium glandicola, P. brevicompactum) isolated from the Libiola sulfide mine (Liguria, Italy) and pyrite-rich mineralizations occurring within the waste rock dumps. After six weeks of incubation, Environmental Scanning Electron Microscope (ESEM) analyses showed how single pyrite crystals were completely corroded and altered by all the selected species. These results represent the first step to establish that fungi play a central role in the biogeochemical cycles of extreme and contaminated sites such as sulfide mines, and that they actively contribute to the evolution of the degraded ecosystem to more harmonized scenery.     

Role of <Emphasis Type="Italic">Serratia marcescens</Emphasis> ACE2 on diesel degradation and its influence on corrosion

A facultative anaerobic species Serratia marcescens ACE2 isolated from the corrosion products of diesel transporting pipeline in North West, India was identified by 16S rDNA sequence analysis. The role of Serratia marcesens ACE2 on biodegradation of diesel and its influence on the corrosion of API 5LX steel has been elucidated. The degrading strain ACE2 is involved in the process of corrosion of steel API 5LX and also utilizes the diesel as an organic source. The quantitative biodegradation efficiency (BE) of diesel was 58%, calculated by gas-chromatography–mass spectrum analysis. On the basis of gas-chromatography–mass spectrum (GC–MS), Fourier Transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD), the involvement of Serratia marcescens on degradation and corrosion has been investigated. This basic study will be useful for the development of new approaches for detection, monitoring and control of microbial corrosion.     

Prevention and control of biocorrosion

Microbial colonization of metals and alloys of industrial usage takes place through the formation of biofilms made of bacteria, extracellular polymeric substances (EPS) and mainly water. These biological deposits can drastically modify the corrosion behavior of structural metals and alloys enhancing localized alterations in the type and concentrations of ions, pH, and oxygen levels. However, biofilms also facilitate the formation of diffusional barriers to the exchange of chemical species from and towards the metal/solution interface. Problems due to biocorrosion and biofouling of industrial systems range from heavy microbiological contamination with consequent energy and efficiency losses to structural failures owing to corrosion.The use of appropriate monitoring strategies complemented with field and laboratory microbiological techniques is necessary to reach a proper understanding of the effects derived from microbiological activity and the role of biofilms in the corrosion reaction to later implement effective control and preventive countermeasures. It must be emphasized that this assessment should be made for each industrial system, considering its previous history, present operational conditions, physicochemical composition of the intake water and the number and identity of microbial contaminants.Cleaning procedures, most relevant biocides and other methods for prevention and control of biocorrosion like coatings, and cathodic protection are successively described. Updated information about monitoring strategies is also included in the final part of the paper.     

Bulk phase resource ratio alters carbon steel corrosion rates and endogenously produced extracellular electron transfer mediators in a sulfate-reducing biofilm

Desulfovibrio alaskensis G20 biofilms were cultivated on 316 steel, 1018 steel, or borosilicate glass under steady-state conditions in electron-acceptor limiting (EAL) and electron-donor limiting (EDL) conditions with lactate and sulfate in a defined medium. Increased corrosion was observed on 1018 steel under EDL conditions compared to 316 steel, and biofilms on 1018 carbon steel under the EDL condition had at least twofold higher corrosion rates compared to the EAL condition. Protecting the 1018 metal coupon from biofilm colonization significantly reduced corrosion, suggesting that the corrosion mechanism was enhanced through attachment between the material and the biofilm. Metabolomic mass spectrometry analyses demonstrated an increase in a flavin-like molecule under the 1018 EDL condition and sulfonates under the 1018 EAL condition. These data indicate the importance of S-cycling under the EAL condition, and that the EDL is associated with increased biocorrosion via indirect extracellular electron transfer mediated by endogenously produced flavin-like molecules.     

Role of iron-reducing bacteria in corrosion and protection of carbon steel

The role of iron-reducing bacteria (IRB) in biocorrosion is under discussion. According to some reports, IRB are able to induce protection of carbon steel while others suggest an important enhancement of corrosion through the reduction and removal of passive films of ferric compounds on the metal surface. In this work, we review recent knowledge concerning microbial respiration, the ecology of IRB containing biofilms and the corrosive or protective effect of such biofilms on metal surfaces.     

Microbiological induced corrosion of AA 6061 nuclear alloy in highly diluted media by Bacillus cereus RE 10

Microbiological studies of a spent nuclear fuel pool in Argentina were performed to evaluate the risk of microbiological induced corrosion and determine the cultivable bacterial population. Based on standard methods and sequencing of the 16sRNA gene, eighteen microorganisms were identified. Bacillus cereus RE 10 was the predominant organism isolated, and was selected to investigate the biofilm formation process and the corrosion effect on aluminum alloy AA 6061 and on pure aluminum (Al 99.999%). To simulate the environmental conditions, the experiments were performed using a highly diluted medium. After 20 days of exposure, major pits covered with deposits were found on AA 6061 samples exposed to B. cereus RE 10 but not on Al 99.999%. There was a close correlation between biofilm patches, corrosion deposits, pitting and Al-(Fe or Ti)-Si inclusions. We postulate that this correlation is a consequence of a light local alkalinization around the inclusions that produces changes in the expression pattern of B. cereus RE 10 and allows bacterial survival using other substrates. Under these conditions, the generated biofilm induces a crevice corrosion effect around the intermetallic inclusions of the alloy. Our results will be useful for further studies related to the microbial impact on nuclear safety in nuclear waste storage facilities in Argentina.     

Understanding microbial inhibition of corrosion. A comprehensive overview

Microorganisms are able to drastically change the electrochemical conditions at the metal/solution interface by biofilm formation. These changes can range from the induction or acceleration of corrosion to corrosion inhibition. Any inhibitory action developed by bacteria may be accomplished within the varied and complex biofilm/corrosion products interactions occurring on a biofouled metal surface.Biocorrosion and its counter process, microbial inhibition of corrosion, are rarely linked to a single mechanism or to a single species of microorganisms. Microorganisms can induce corrosion inhibition according to two general mechanisms or their combination: i) neutralizing the action of corrosive substances present in the environment; ii) forming protective films or stabilizing pre-existing protective films on a metal. Different practical cases illustrating these mechanisms are presented in this overview.It must be stressed that some times the inhibitory action of bacteria can be reversed to a corrosive action in bacterial consortia located within biofilm thickness.