Aerobic Corroded-Metallic.pdf

Air, Soil and Water Research ORiginAL ReSeARch Open Access Full open access to this and thousands of other papers at http://www.la-press.com. Aerobic and Facultative Microorganisms Isolated From corroded Metallic structures in a Hydroeletric power Unit in the Amazon Region of Brazil Amabel F. correia1, Jorge F.O. Segovia2, Roberto M. Bezerra3, Magda c.A. gonçalves3, Sócrates S. Ornelas4, Damaris Silveira5, José c.T. carvalho3, Sérgio P.S.S. Diniz6 and Luis i.B. Kanzaki4 1 central Public health Laboratory/LAcen, Brasília, DF, Brazil, ceP 70830-010. 2The Brazilian Agricultural Research corporation/eMBRAPA, Rodovia Juscelino Kubitschek, Fazendinha, Macapá, AP, Brazil, ceP 68903-419. 3Laboratory of Drugs, Federal University of Amapá, AP, Brazil, ceP 68902-280. 4Laboratory of Bioprospection, University of Brasília, DF, Brazil, ceP 70910-900. 5Faculty of health Sciences, University of Brasilia, DF, Brazil, ceP 70910-900. 6Laboratory of natural Products, State University of Maringá, PR, Brazil, ceP 87020-900. corresponding author email: [email protected] Abstract: Aerobic and facultative bacteria belonging to the Enterobacteriaceae, Pseudomonadaceae, Bacillaceae, Corynebacteriaceae and Streptococcaceae families have been isolated from corroded metallic structures of a hydroelectric power unit in the Amazon region of Brazil. In addition to anamorphic dematiaceous and moniliaceous fungi, members of the archeobacteria kingdom were also detected in the same samples. Scanning electron micrographs of metal bars cultivated with consortia of the isolated microorganisms depicted ­suggestive­images­of­bioilm­formation­and­corroded­metallic­structures­questioning­the­possible­role­of­these­­microorganisms­in­the­ corrosion activity. We also found Amazonian medicinal plants exhibiting inhibitory activity against some of the isolated microorganisms. Our­ new­ indings­ need­ additional­ studies­ to­ conirm­ the­ participation­ of­ some­ isolated­ microorganisms­ in­ the­ process­ of­ metallic­ ­degradation­despite­our­main­question­if­are­there­particular­microorganisms­involved­in­the­corrosion­process?­or­if­­physicochemical­ conditions­ would­ favor­ the­ development­ of­ a­ particular­ microbiota­ and­ consequently­ the­ corrosion­ process­ would­ result­ from­ its­ ­metabolism?­Therefore­we­hypothesize­that­any­microorganism­could­be­potentially­involved­in­the­genesis­of­corrosion­process.­This­is­ the­irst­report­in­the­literature­dealing­with­microbiologically­induced­corrosion­in­the­Amazon­region­which­is­especially­­characterized­ by its high humidity and elevated temperature all year round. Keywords: biocorrosion, microorganisms, metallic surfaces, hydroeletric power unit, amazon region of Brazil, Amapá state Air, Soil and Water Research 2010:3 113–121 doi: 10.4137/ASWR.S6105 This article is available from http://www.la-press.com. © the author(s), publisher and licensee Libertas Academica Ltd. This is an open access article. Unrestricted non-commercial use is permitted provided the original work is properly cited. Air, Soil and Water Research 2010:3 113 correia et al Introduction Microbiologically induced corrosion is a matter of great concern all over the world. It costs so much to prevent the corrosion process and to replace periodically deteriorated metal structures.1­The­­isolation­and­identiication­of­microorganisms­involved­in­the­­corrosion­ process is a necessary and mandatory step in order to design methods to prevent and control it.2,3­The­bioilm­ formation which is mainly determined by the interaction of a consortia of microorganisms represents the main factor involved in the etiological mechanism of biocorrosion. Composed basically of 95% of water and 5% percent of extracellular polymeric substances including organic molecules produced by the microbial metabolic activity and inorganic molecules, the bioilm­ generates­ a­ highly­ dynamic­ environment,­ promoting the exchange of ions between the metallic surface and itself. Such ionic interactions weaken the arrangement of metallic bonds’ structures, causing issures­ in­ its­ surface­ that­ in­ an­ ampliied­ scale­ and­ at a practical view result in great economic loss.1,2,4 The­algae,­fungi­and­bacteria­have­been­reported­to­ be involved in corrosion processes.5,6­ The­ members­ of the Enterobacter and Pseudomonas genera were found to be potential candidates in the etiology of biocorrosion related processes as these microorganisms are capable to interchange electrons with the adhered surface representing the fundamental mechanism of ionic interplay over the metallic surfaces leading to the corrosion process.7,8 Also, Sulfate-Reducing Bacteria (SRB), a group of phylogenetically diverse anaerobes that perform the dissimilatory reduction of­ sulfur­ compounds­ including­ sulfate,­ sulite,­ thiosulfate­ and­ even­ sulfur­ to­ form­ sulide,­ is­ involved­ in the corrosion process, in mechanisms producing cathodic depolarization by the removal of hydrogen ions (protons) from the cathodic area on the iron surface catalyzed by bacterial hydrogenases, coupled to sulfate­reduction­to­sulide­that­could­account­for­the­ severe corrosion of iron in an anoxic environment under neutral pH.9,10 Here­ we­ report­ for­ the­ irst­ time,­ the­ isolation­ and biochemical characterization of microorganisms cultivated from fragments of corroded metallic structures collected at the facilities of Coaracy Nunes hydroelectric power unit, in Amapa state, in the Amazon region of Brazil and found also the suggestive role of the isolated consortiated microorganisms in 114 the corrosion process, as also preliminary results of antimicrobial activity of Amazonian medicinal plants­ against­ the­ isolated­ microorganisms.­ Taking­ into account our results we are strongly inspired to hypothesize that any microorganism is capable to trigger mechanisms of metallic corrosion dependly mainly on the microenvironment physicochemical conditions and the molecular composition and architecture of the material surface exposed to the local microbiota. Materials and Methods The hydroeletric power unit “coaracy nunes” The­Coaracy­Nunes­hydroelectric­power­unit­(UHE)­ is located in northern Brazil, at Ferreira Gomes county, in the Amapa state, delimited at southeast by the­Amazon­river­and­northeast­by­the­Oiapoque­river,­ in the boundaries of French Guyana (00°55’00’ North and 51°15’00’ West) as depicted in Figure 1 (Map of Amapá, Brazil). corroded metallic structures At­the­UHE,­10­samples­of­corroded­fragments­and­ 2 water samples from pipelines designated AB1 to AB12 were collected from the metallic surfaces of the pipelines/valves/heat exchanger and from the­ ­refrigeration­ system.­ The­ crusts­ were­ removed­ Figure 1. geographic localization of coaracy nunes hydroeletric Power Unit in the Amapa state, in Ferreira gomes county. Air, Soil and Water Research 2010:3 Microorganisms involved in corrosion process utilizing a sterile bistouri and blade and collected on sterile falcon tubes containing transport medium (vermiculite) as also water from the pipelines refrigeration system. Microbiological culture of corroded metallic fragments and water In order to isolate and biochemically characterize the microorganisms, the collected samples were inoculated into sterile brain heart infusion medium (BHI) and incubated at 35 ± 1 °C for 24 hours and transferred to blood agar, MacConkey agar and azide agar.­The­gram­staining­was­performed­at­this­stage.­ Additional 24 hours incubation period was carried out at­the­same­conditions.­The­agar­grown­colonies­were­ recorded considering morphological and staining characteristics.­ The­ pure­ cultures­ were­ obtained­ by­ reinoculation of isolated colonies in the same media. The­complementing­biochemical­characterization­was­ performed in a semiautomatic Autoscan Walkaway (W/A) system (MicroScan, Sacramento, Calif.) and by the analysis based on the metabolic characteristics of isolated microorganisms.11 Also the previously suspended samples in BHI media were transferred to the Sabouraud agar dextrose and Mycosel agar, and kept under incubation for 10 days at 25 °C.­The­fungi­grown­colonies­were­ transferred to the Potato dextrose agar and kept at room­­temperature.­The­phenotypic­identiication­was­ based on the macroscopic and staining characteristics likewise the texture, topography and colour of the colonies as also the microscopic features displayed by the reproductive structures, the hyphae and conidia.12,13 Detection of unculturable microorganisms by molecular methods The­ samples­ collected­ from­ the­ metallic­ ­corroded­ structures in BHI medium were submitted to DNA extraction­ and­ ampliied­ by­ the­ polymerase­ chain­ reaction utilizing the Archaebacteria universal primers.14­ As­ briely­ described,­ 500­ uL­ of­ each­ collected sample, enriched in BHI medium was incubated under agitation for 24 hours at 35 °C. After growth,­ DNA­ was­ extracted­ utilizing­ the­ PureLink­ Genomic DNA kit (Invitrogen), following the steps of proteinase K digestion of bacterial lisates and RNA degradation by RNase treatment. DNA was extracted Air, Soil and Water Research 2010:3 on­columns­(PureLink­Spin­Column),­washed­out­and­ eluted.­The­quality­of­obtained­DNA­was­assessed­by­ visualization­ on­ 1%­ agarose­ gel­ and­ quantiied­ in­ a­ spectrophotometer. DNA­ samples­ were­ ampliied­ by­ the­ polymerase­ chain reaction utilizing 0.5 uM of archael primer pair A571F­and­UA1204R­(16S­rRNA),­0.2­mM­of­dNTPs,­ 1.0­U­of­Taq­polymerase­in­2.5­uL­of­buffer­(Roche)­ and 1.5 mM of Mg++­in­a­inal­volume­of­25­uL.­The­ thermocycler was programmed to 94 °C/2 min., followed by 30 cycles of 94 °C/1 min., 55 °C/1 min., 72 °C/1­ min.­ and­ inishing­ at­ 75­ °C/10 minutes. After­ampliication,­12.5­uL­of­reaction­volume­was­ analyzed by electrophoresis on 1% agarose gel and ethidium bromide staining. Analysis by scanning electron microscopy The­ corroded­ fragments­ and­ water­ (AB1­ to­AB12)­ collected in individual sterile falcon tubes were transferred to BHI sterile medium in tubes containing a metallic bar measuring 1 cm long × 1 cm large and 1 mm deep. Each 24 hours after inoculation, the turbidity­of­the­medium­was­measured­in­an­ELISA­ reader at 600 nm wavelength. After 14 days, the metal bars were washed out in distilled water, dried at room temperature and observed under the scanning electron microscope,­in­a­JEOL-JSM,­T-330­A­model,­coupled­ to an analyzer of dispersive energy, a photographic camera­ and­ a­ LEO­ microscope­ ­Leica-Zeiss,­ 440 model coupled to EDX and WDX detector in a 50×­magniier.15 Results Aerobic and facultative bacteria belonging to the Enterobacteriaceae, Pseudomonadaceae, Bacillaceae, Corynebacteriaceae and Enterococcaceae families were isolated from the corroded metallic structures and­biochemically­characterized.­The­isolates­of­the­ Enterobacteriaceae family included the Enterobacter cloacae, Escherichia coli, Hafnia alvei and Serratia marcescens, and pertaining to the Bacillaceae family we isolated the Bacillus polymyxa, Bacillus thuringiensis, Bacillus brevis and Bacillus alvei.­The­ Corynebacterium pseudodiphthericum, Pseudomonas aeruginosa and Enterococcus faecalis were the sole representatives of the Corynebacteriaceae, Pseudomonadaceae and Enterococcaceae families 115 + + + + + + + Abbreviations: +, positive; -, negative; OnPg, ortho-nitrophenyl-β-D-galactosidase; OF, oxidation and fermentation. + - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + cetrimide Acetamide Tartarate Malonate citrate Galactosidadse (OnpG) Vogesproskauer esculin hydrolisis Tryptophan deaminase Ornithine Arginine Lysine Indole Hydrogen sulite Urea Melbiose Adonitol Inositol Arabinose Ramnose Raphnose sorbitol sucrose Glucose Microorganisms Family/species + + + nitrate Fermentation + + + + Base Metabolic markers enterobacteriaceae Enterobacter cloacae Escherichia coli Hafnia alvei Serratia marcescens pseudomonadaceae Pseudomonas aeruginosa OF Glicose 116 Oxidase respectively. All biochemical parameters analyzed, manually and automatically, were displayed in Tables­ 1,­ 2­ and­ 3.­ Phenotypical­ and­ metabolic­ ­proiles­ of­ isolated­ microorganisms­ were­ assorted­ and­ based­ on­ these­ data,­ identiied­ in­ the­ W/A­ system’s computer software at the genera and species level.11­All­identiied­members­of­the­Enterobacteriaceae family, Enterobacter cloacae, Escherichia coli, Hafnia alvei and Serratia marcescens presented bacilar morphology, gram negative staining, oxidase and cetrimide negative test, ornithine and orthonitrophenyl-β-D-galactosidase positive tests, being all of them capable to utilize glucose, allowing us to differentiate them from the Pseudomonadaceae family member, Pseudomonas aeruginosa (Table 1). Members of the Bacillaceae and Corynebacteriaceae family reacted positively by the gram staining, being identiied­ mainly­ by­ their­ property­ to­ ferment­ glucose,­sucrose­and­lactose­in­the­TSI­test.­The­Bacillus polymyxa and Bacillus thuringiensis utilized all carbohydrates and the Bacillus brevis and Bacillus alvei just fermented glucose and, the solely identiied­ species­ in­ the­ Corynebacteriaceae­ family,­ the­ Corynebacterium pseudodifhtherium did not ferment any sugar (Table 2). Just one species, Enterococcus faecalis, in the Enterococcaceae family was identiied,­yielding­catalase­negative­test,­growth­on­6.5%­ NaCl broth and esculine positive test and did not hemolyze blood in agar (Table 3). The­ Myceteae kingdom was represented by the isolates of anamorphic dematiaceous and moniliaceous fungi.­The­morphological­and­staining­characteristics­ of colonies of fungi grown in Sabouraud agar are shown in Figure­2A­and­2B.­The­dematiaceous­fungi­ exhibited dark coloured, grayish or grayish-brown powdery and felt-like colonies, and their dark reverse showed curves to straight conidia, containing three to four septs and septated and dematiaeous hyphae, characteristic of Curvularia spp (Fig.­2A).­The­moniliaceous fungi presented white cotton-like colonies and a brown reverse colour with double verticillated conidiophores exhibiting globolous conidia and septated and hyaline hyphae, characteristic of Penicillium spp (Fig. 2B). Preliminary metagenomic analysis of DNA extracted from collected mixed water and corroded metallic samples detected a band in the gel after Table 1. Biochemical characterization of enterobacteriaceae and Pseudomonadaceae species isolated from corroded metallic structures in the coaracy nunes hydroelectric Power Unit, Amapa state. correia et al Air, Soil and Water Research 2010:3 Microorganisms involved in corrosion process Table 2. Biochemical identiication of species belonging to the bacillaceae and Corynebacteriaceae families isolated from corroded metallic structures in coaracy nunes hydroeletric Power Unit, Amapa state. Microorganisms Bacillaceae Bacillus polymyxa Bacillus brevis Bacillus alvei Bacillus thuringiensis corynebacteriaceae Corynebacterium pseudodifhtherium Blood agar hemolysis catalase Urea TsI up/bottom H2s β β β β + + + + + + + A/A Alc/A Alc/A A/A - β + + Alc/Alc - Abbreviations: +, positive; -, negative; β, β-hemolysis; TSi, triple sugar iron; Alc/A, alkaline and acid reaction in TSi. ­submission­ to­ electrophoresis­ of­ ampliied­ DNA­ fragments by the PCR assay, corresponding to 1,300 bp fragment stained by ethidium bromide as depicted in Figure­ 3.­The­ band­ was­ not­ resolved­ in­ sequential­gel­analysis­in­order­to­check­out­if­more­ than one band was present. Previously mentioned isolated microorganisms were found to be associated in the corroded fragments and water removed from the metallic surfaces and­ pipelines­ respectively.­ The­ scanning­ electron­ micrographs exhibiting colonies of the isolated bacteria­and­bioilm­formation­on­the­surface­of­the­metallic structures are depicted in Figures 4 and 5 as also the metallic dissolution represented by the spectra of energy dispersion of molecular oxygen and iron ions (Fig.­ 5).­The­ bacterial­ growth­ over­ the­ surface­ of­the­metallic­bars­in­the­liquid­medium­in­consortiated groups as designated in material and methods from­ AB1­ to­ AB12­ did­ not­ show­ any­ signiicative­ difference in turbidity parameters, all starting the lag phase in the second day of cultivation, determined by the measurement of the optical density values in an ELISA­ reader­ at­ 600­ nm­ wavelength­ (Fig. 6). Also we­detected­issures­in­the­surface­of­the­metallic­bars­ colonized in vitro by the consortiated microorganisms that were previously biochemically characterized. They­ were­ not­ assayed­ individually­ as­ in­ the­ natural environment those microorganisms are found associated as we corroborated in our experiments. Of 30 distinct medicinal plants collected in the Amapa state, we detected preliminarily 5 plant extracts exhibiting antimicrobial activity. All plants assayed in this research work are traditionally utilized by native people in the Amazon region to cure their diseases.­ The­ ethanolic­ extracts­ of­ Copaifera reticulata, Tabebuia serratifolia, Brosimum rubescens and Carapa guianensis presented activity against gram positive bacilli of the Bacillus genera, and the ethanolic extract of Aspidospermum carapanauba showed activity against the gram positive bacilli and Pseudomonas aeruginosa. Despite these data be preliminary, most of the microorganisms susceptible to the plants extracts are multiresistant to commonly used antibiotics (data not shown). Discussion The­Amazon­region­is­characterized­by­high­humidity and elevated temperatures all over the year. In Amapa state, the Ami and Amw climates predominate.­According­to­Köppen­classiication,­the­former­ Table 3. Biochemical identiication of the Streptococcaceae family species isolated from corroded metallic structures of the coaracy nunes hydroeletric Power Unit, Amapa state. Microorganism streptococcaceae Enterococcus faecalis Hemolisys in blood agar catalase test nacl at 6.5% Bile +฀esculin test Without hemolisys - + + Abbreviations: +, positive; -, negative. Air, Soil and Water Research 2010:3 117 correia et al W 1 Kb M 10 11 12 T.9 8 7 6 5 3 4 2 1 R CR CR CR CR CR CR CR CR CR CR CR ON C B C B B B B B B B B B B B Figure 2A. Fungus Curvullaria spp. cultivated in Agar Sabouraud. Agar surface (left). Agar reverse side (midlle). Optical microscopy (40×), stained with lactophenol, showing conidia and septated dematiae hyphae (right). is characterized by tropical rainy weather, presenting a­ well­ deined­ dry­ season,­ lacking­ ­pluviometric­ precipitation from August to December, and the latter is also characterized by tropical rainy weather but­ without­ a­ deined­ dry­ season,­ thus­ raining­ regularly during all year round.16­The­Coaracy­Nunes­ hydroeletric power unit is localized in the transition limits of both climate pattern above described. The­proper­maintanance­of­metallic­strucutures­in­a­ hydroeletric power unit, particularly in the amazon region­requires­periodic­painting­and­substitution­of­ corroded­ structures,­ demanding­ excessive­ ­inancial­ costs­ making­ the­ inal­ product,­ the­ eletricity,­ so­ expensive to the population. The­ rich­ microbiota­ in­ the­ Amazonian­ tropical­ forest greatly contributes to the widespread colonization of microorganisms in all surfaces of any material­ such­ as­ wood,­ metals,­ plastics­ whatsoever.­ The­ metallic structures composing important industrial facilities, including the electricity power unit, suffer enormous losses due to the corrosion processes, mainly induced by microorganisms. In our work, we­ could­ conirm­ the­ indings­ of­ many­ laboratories­ and also, observe in vitro the suggestive role of the Figure 2B. Fungus Penicillium spp. cultivated in Agar Sabouraud. Agar surface (left). Agar reverse side (midlle). Optical microscopy (40×), stained with lactophenol cotton blue, showing double verticillated conidiophores exhibiting globolous conidia and septated and hyaline hyphae (right). 118 Figure 3. PCR assay of uncultured microorganisms DNA ampliied utilizing Archae universal primers (16S ribossomal RnA gene). First Lane/1 Kb MW (left) showing bands of DnA molecular markers and lane/ BcR 2 showing a 1,300 bp fragment and last Lane/cOnTR as a negative control. isolated microorganisms consortiated in the corrosion process.­The­detection­of­bioilm­production­as­also­ the precipitated salts on the metallic bars allied to the detection of spectral patterns of metallic ions (Figs. 3 and 4) likewise, decrease in iron ions concentration, carbon atoms and molecular oxygen increase besides the alteration in the concentration of other elements (Fig. 5) suggests the occurrence of corrosion processes of microbial etiology. Interestingly, the microorganisms usually reported in pathological processes in humans and animals as Serratia marcescens, Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa, Enterococcus faecalis, Hafnia alvei Figure 4. Optical micrograph magniied 50× showing deposits of metallic salts and corroded areas (black spots) in metal bars incubated with consortiated microorganisms isolated from corroded metallic structures of coaracy nunes hydroeletric Power unit in Amapa state. Air, Soil and Water Research 2010:3 Microorganisms involved in corrosion process Figure 5. Scanning electron micrograph magniied 200.000× showing surface fractures over the metal bar after microbial growth of samples obtained from corroded metallic structures of the coaracy nunes Power unit in Amapa state. and Corynebacterium pseudodiphtheriticum were detected in metallic corrosion processes too.17–19 Anyway, other microorganisms uncommonly causing diseases, known as opportunistics organisms are usually widely spread in the environment, victimizing immunosupressed humans, animals and plants.20,21 Therefore,­under­this­viewpoint,­bioorganisms­defend­ dynamically themselves against invading and colonizing microorganisms22 contrary to inert material like metals that need technological devices23 to protect their surfaces against environmental microorganisms’­ colonization­ and­ consequential­ ions­ exchange­ between the microorganisms metabolic products and metal ionic surface, which generally early or later results in corrosion processes, as generally proposed to certain microorganisms.24 1,2 AB01 AB02 1 Optical density AB03 AB04 0,8 AB05 AB06 0,6 AB07 AB08 AB09 0,4 AB10 AB11 0,2 AB12 CN 0 1st day 2nd day 5th day Figure 6. growth curve (lag phase) of consortiated groups of bacteria (AB01 to AB12) in the experiment to reproduce biocorrosion in vitro. Air, Soil and Water Research 2010:3 Just a minimum percentage of microorganisms in distinct environments are cultivated by conventional microbiological methods.25­ Uncultured­ microorganisms have been detected by preliminary metagenomic analysis. In our study, the solely band found by the PCR assay of the isolated DNA samples of consortiated­microorganisms­could­represent­the­ampliication of multiple microorganisms DNA fragments.26 Utilizing­ molecular­ tools­ to­ detect­ ribosomal­ DNA­ segments from fragments of industrial pipelines carrying crude oil, about 31 distinct archaebacteria composing the Methanobacteriales, Methanomicrobiales and Methanosarcinales order were found, despite it is not known the role of these microorganisms in biocorrosion processes.27 As expected, common soil microorganisms were found among the analyzed samples, mainly represented by members of the Bacillaceae family. Ongoing studies are aiming for the isolation and characterization of anaerobes which were partially initiated by metagenomic studies and considering their important roles in biocorrosion processes.9,10 Despite­the­current­knowledge­to­ind­culprits­for­ corrosion processes, our results allied to other reports in the literature suggest that there are not particular microorganisms involved in the mechanisms of corrosion but, the physicochemical conditions of the environment determines that the particular microbiota of any surface and therefore the metabolic activity of any microorganism would interact with metallic surfaces or in other words, the redox reactions would occur initiating the corrosion process of metallic surfaces. Presently we are looking for local solutions for the problem, besides to what actually has been done, likewise the removal of damaged metallic structures and their periodic painting. As an alternative way to chemical pollutants utilized in paintings composition, we are testing Amazonian medicinal plant extracts looking at growth inhibition or destruction of microorganisms found colonizing the metallic structures. We have shown growth inhibition of multiresistant bacteria involved in human nosocomial infections by extracts of Amazonian medicinal plants.28 As many of our microorganisms isolates from corrosion processes are also involved in human and animal diseases, we proposed in this study to assay Amazonian plants as antimicrobial agents to eliminate corrosion. If from the plants assayed, crude antimicrobial agents against 119 correia et al 2500 Fe Counts 2000 1500 1000 500 Fe O S P Cl C Na SiP Cl S Fe 0 0 2 4 6 8 10 8 10 Energy (keV) 800 O Counts 600 P Fe 400 200 Fe Fe P 0 0 2 4 6 Energy (keV) Figure 7. Scanning electron micrograph magniied 50× showing metallic salts deposit (white area) and smooth zone displaying metallic dissolution as conirmed by energy spectral dispersion showed in the graphics (right side) of mainly iron and oxygen íons picks dislodgment. consortiated microorganisms could be developed, the beneits­would­prevail­as­the­plants­are­not­toxic­to­ the environment, they could be cultivated and locally processed and would also contribute to the improvement­of­quality­of­life­of­local­communities. Disclosures This­ manuscript­ has­ been­ read­ and­ approved­ by­ all­ authors.­This­paper­is­unique­and­not­under­consideration by any other publication and has not been published­elsewhere.­The­authors­and­peer­reviewers­ report­ no­ conlicts­ of­ interest.­ The­ authors­ conirm­ that they have permission to reproduce any copyrighted material. Acknowledgements We­are­grateful­to­Eletronorte/ANEEL­for­the­inancial support to carry out this study and particularly to Eletronorte/Amapa staff for the logistic support during­samples­collection­in­the­Hydroeletric­Power­Unit­ Coaracy Nunes. References 1. Beech IB, Gaylarde CC. Recent advances in the study of biocorrosion: an overview. Rev Microbiol. 1999;30(3):117–90. 2.­ Dinh­HT,­Kuever­J,­Mussmann­M,­Hassel­AW,­Stratmann­M,­Widdel­F.­Iron­ corrosion by novel anaerobic microorganisms. Nature. 2004;427(6977): 829–32. 3.­ McNamara­CJ,­Perry­TD,­Leard­R,­Bearce­K,­Dante­J,­Mitchell­R.­Corrosion­ of aluminum alloy 2024 by microorganisms isolated from aircraft fuel tanks. Biofouling. 2005;21(5–6):257–65. 120 4. Beech IB, Sunner JA, Hiraoka K. Microbe-surface interactions in biofouling and biocorrosion processes. Int Microbiol. 2005;8(3):157–68. ­ 5.­ Smirnov­ VF,­ Belov­ DV,­ Sokolova­ TN,­ Kuzina­ OV,­ Kartashov­ VR.­ Microbiological corrosion of aluminum alloys. 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