Pseudomona Aureginosa Corrosion 1

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Abstractmicrobially influenced corrosion has been the subjectof extensive studies for the past five decades and several models have

been proposed to explain Mechanisms governing biocorrosionone ofthe most famous bacteria in this field is Pseudomonas aeruginosa,aGram-negative motile rod bacteria and widely distributed in natureandcan grow in distilled water, laboratory hot water baths, hot tubes,wet IV tubing, and other water containing vessels. Some of theseorganisms may be primary pathogens .These Bacteria are capable ofsensing surfaces.Contacting.the surface initiates a complexdifferentiation program resulting in e.g. synthesis of alginate. Metalsurfaces are rapidly colonized by microorganisms in contact withnatural or industrial aquatic environments, giving rise to a complexand strongly adhering microbial community, termed as biofilmPseudomonas genus are acknowledged to be the pioneer colonizers inthe process of biofilm formation and often found in the primary stageof biofilm formation in aquatic environments The biofilmaccumulation not only protects microbial cells from the externalenvironment, but it is also detrimental to the underlying substratumthereby causing physicaldegradation or biodeterioration of the metalsurface.

KeywordsPseudomonas aeruginosa, microbial corrosion,microbiologically influenced corrosion (MIC), biocorrosion

I. INTRODUCTION

WING TO its economic and environmental importance,especially for the oil and gas industry, microbiallyinfluenced corrosion has been the subject of extensive

studies for the past five decades and several models have beenproposed to explain Mechanisms governing biocorrosion [1]Corrosion is a leading cause of pipe failure and is a maincomponent of the operating and maintenance costs of gasindustry pipelines.Quantifying the cost of corrosion generally,and more specifically the cost associated with microbialcorrosion, in the gas industry is not easily done and is

Hamidreza Mansouri is with Azad University Science and ResearchBranch of Tehra. Email: [email protected], Tel:+989171825738

S.A.AlaviDepartment of Chemical engineering, Azad University Scienceand Research Branch of Tehran.

Mehdi Yari, Department of Metallurgy and Materials, Azad UniversityScience and Research Branch of Tehran.

controversial. Pipeline corrosion was estimated in 1996 to costthe gas industry about $840 million/year [2] and in 2001 itwas estimated that the annual cost of all forms of corrosion tothe oil and gas industries was $13.4 billion, of whichmicrobially influenced corrosion accounted for about $2billion [3]

While it is well recognized that chemical and microbial

mechanisms both contribute to corrosion, it is uncertain what

the relative contribution of microbial activity to overall pipe

corrosion is. It has been estimated that 40% of all internal

pipeline corrosion in the gas industry can be attributed to

microbial corrosion [4] but data are needed to confirm or

revise this estimate. Basic research to increase our

understanding of the microbial species involved in microbial

Fig.1 Pseudomonas aeruginosa [19]

corrosion and their interactions with metal surfaces and with

other microorganisms will be the basis for the development of

new approaches for the detection, monitoring, and control of

microbial corrosion. A thorough knowledge of the causes of

microbially influenced corrosion and an efficient and effective

means of detecting and preventing corrosion are lacking. It iswell recognized that microorganisms are a major cause of

corrosion of metal pipes, but despite decades of study it is still

not known with certainty how many species of

microorganisms contribute to corrosion, how to reliably detect

their presence prior to corrosion events, or how to rapidly

assess the efficacy of biocides and mitigation procedures [5].

Investigations of microbial species present in gas industry

pipelines have traditionally relied upon the use of samples

obtained from pipelines to grow bacterial cultures in the

laboratory [6]. Laboratory growth media cannot accurately

A Study of Pseudomonas Aeruginosa Bacteriain Microbial Corrosion

Hamidreza Mansouri, S.A Alavi, Mehdi Yari

O

2nd International Conference on Chemical, Ecology and Environmental Sciences (ICCEES'2012) Singapore April 28-29, 2012

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reflect the true conditions within pipelines, and

microbiologists have recognized that the vast majority of

microbial species cannot currently be grown in the laboratory

[7] thus; culture-dependent approaches underestimate the

biocomplexity of microbial communities.

.

II.PSEUDOMONAS AERUGINOSABACTERIA

P. aeruginosa is a Gram-negative motile rod capable ofcausing infection in almost all of the bodys tissues. P.aeruginosa utilises a variety of virulence factors and canproduce biofilms to aid attachment and dispersal and uses itsflagella and pili to establish infections in the host. [19] Seefigure 1.

P. aeruginosa infections are often associated withblue/green pus or exudates with a characteristic musky odourP. aeruginosa widely distributed in nature (soil, water, plants,animals). it can grow in distilled water, laboratory hot waterbaths, hot tubes, wet IV tubing, and other water containingvessels. This explains why the organism is responsible for somany nosocomial infections. [8]. Pseudomonas genus are

acknowledged to be the pioneer colonizers in the process ofbiofilm formation and often found in the primary stage ofbiofilm formation in aquatic environments [9].

III. BIOFILM AND BIOCORROSION

Metal surfaces are rapidly colonized by microorganisms incontact with natural or industrial aquatic environments, givingrise to a complex and strongly adhering microbial community,termed as biofilm .[16] The biofilm accumulation not onlyprotects microbial cells from the external environment, but itis also detrimental to the underlying substratum, therebycausing physical degradation or biodeterioration of the metalsurface This phenomenon is widely recognized as

biocorrosion or microbiologically influenced corrosion(MIC).[17]

Fig.2 Model of biofilm development as a part of bacterial lifecycle [13]

Model of biofilm development as a part of bacterial lifecycle is shown in figure 2.[13] Individual planktonic cells canreach the surface by active or passive means. The initial cell-to-surface contact is often reversible, but if environmentalcues and possible signaling molecules favor surface-attachedgrowth, then the cells attach irreversibly with the aid ofexcreted extracellular polymeric substances (EPS). Division of

cells and growth of the population, while keeping cell-to-cellcontacts, result in the formation of micro colonies.Mature biofilms often possess a hallmark architecture wheremicro colonies are surrounded by a network of water channelsallowing the flow of nutrients into the interior of the biofilm.Hydrodynamics as well as cell-to-cell signaling moleculesplay a regulatory role in the development of the biofilmarchitecture.

Stoodley et al. (2002) speculated that also the maintenanceof open water channels in multi-species biofilms requiresinterspecies signalling to inhibit growth and EPS productioninto the channels. Some cells can be released to a planktoniclifestyle ensuring the occupation of new niches. The release ofcells occurs due to physical detachment caused by shearforces, or due to a programmed set of events controlled bysignaling molecules and leading to a local hydrolysis of EPSmatrix, e.g. P. aeruginosa can cleave its own EPS by alginatelays enzyme. [18].

IV. THE INFLUENCE OF PSEUDOMONAS AERUGINOSA ONALLOYS

Bacteria are capable of sensing surfaces [13].Contacting thesurface initiates a complex differentiation program resulting ine.g. synthesis of alginate. Genes essential for production ofthis major EPS component of Pseudomonas aeruginosa wereshown to be up-regulated already 15 min after attachment.[14]

Figure 3 show the SEM images of the Ni-Co discs surfacesimmersed in the medium without P. aeruginosa and with P.aeruginosa[20]after incubation for 5 h. in fig. 3a the oxidecomponents of Ni and Co can be clearly seen.

Fig.3 (a) the oxide components of Ni and Co

As displayed in Fig.3b-e after 5 hours of immersion with

medium containing bacterium, it can be seen that the Ni-Cosurface partially covered with clusters of microbial cells, EPSand metabolism products. In addition, from the Fig. 3e,pitting corrosion and crevice corrosion were observed on thesurface of the inoculated medium rather than on the surfaceexposed to only medium. Theenergy dispersive X-ray spectra(EDS) analysis of the corrosion products on discs wasillustrated in Fig.3d.


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Fig.3 (b) medium with P. aeruginosa

Fig.3 (c) medium with P. aeruginosa

Fig.3 (d) The EDS analysis of the corrosion products on discs

Fig.3 (e) pitting corrosion and crevice corrosion

The corrosivity of Pseudomonas aeruginosa and sulfate-reducing bacteria (SRB) in seawater was evaluated in aerobicand anaerobic conditions [20]. The Pseudomonas species arepotential producers of extracellular polymers (EPS), theproduction of which is intensified in the presence of oxygen.

In turn, the presence of EPS in the biofilms generates adifferent aeration gradient, creating favorable conditions forthe development of the SRB. So that, although the SRB arestrict anaerobes, a higher number of this group of bacteria isobserved in the biofilms formed under aerobic conditions [21]Two experiments were carried out (under aerobiosis andanaerobiosis) in electrochemical cells, in duplicate, aspresented in figure 4. In these systems, aseptically, AISI 1020carbon steel coupons were placed, of which 5 (about 1 cmarea) for polarization experiments and another 4 (about 5 cmarea) for both sessile microorganism quantification and weightloss measurements. Subsequently, the system was filled withsterile seawater and some nutrients in order to guarantee the

viability of the microorganisms. Each experiment lasted for 28days and was kept under slight magnetic agitation and at roomtemperature. In the experiment under anaerobiosis, nitrogenpurges were performed, before and after the inoculation, aswell as during the entire experiment in order to establishdissolved oxygen concentration lower than 3 ppm. [20].

Fig.4 Test cell Fig.5 Variationof the corrosion potential

throughout the time


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The weight loss was proportional to the exposure timepresenting practically linear behavior in the aerated system seeFigure 5.In this Figure variation of the corrosion potentialthroughout the time is shown. [20].

Another study on Copper and galvanized steel hasimplemented these materials are frequently used in theconstruction of cooling towers because of their well-knownantifouling property. Biofilm in cooling water systems is a

fairly common problem. When the biofilm layer could not becleaned, pathogen bacteria living there can lead to fataldiseases. Copper and galvanized steel coupons (50 x 25 x 1mm) were prepared according to guidelines in ASTM G1-72(ASTM 1975).Copper coupons: Surface of copper coupons(99.9% purity) were sanded. The total surface area of eachcoupon was determined. Galvanized steel coupons: Thethickness of the zinc coating covering the stainless steel was5m. The cut areas of all the coupons were coated with epoxyzinc phosphate primer (Moravia Turkey) and then coveredwith epoxy finish coating (Moravia, Turkey) to avoid theinitiation of corrosion at these disturbed areas. The totalsurface area of each coupon was determined.[21] Threecoupons of each material were removed monthly from the

cooling water system during ten months. Biofilms on theirsurfaces were scraped by sterile swab, suspended in sterile tapwater and vortexes for 60 s [22].Biofilm was confirmed bySEM on copper and galvanized coupons in experiments inFigure 7, SEM micrograph of the biofilm formed on copper(A,B) and galvanized steel (C,D) surfaces, 1th month (A,C),10thmonth (B,D) are shown.

Fig.7SEM micrograph of the biofilm formed on copper (A, B)and galvanized steel (C, D) surfaces, 1th month (A, C), 10th

month (B, D)

During ten months the result of total aerobic mesophilicheterotrophic bacteria (TAMHB) on copper and galvanizedsteel surfaces are shown in Figure 8. Statistical analysisdemonstrated that TAMHB counts were significantly (P


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mechanism for persistent contamination of the water. Theorganisms and their products may decrease disinfectant levels(by increasing disinfectant demand), pose a direct publichealth risk, or create taste and odor problems. Biofilms likelyexist in all distribution systems, and are recognized as anormal part of the distribution system.[12]P. aeruginosa is widespread in environmental waters,

especially in those waters associated with human activity. The

organism is often found in finished waters and in pipebiofilms. Although P.aeruginosa has not been conclusivelyimplicated in a reported waterborne disease outbreak, it has asignificant role in nosocomial illness, including outbreaks. It isa pathogen of concern for people with severe burns andwounds, diabetes, and is the primary cause of injury and deathin people with cystic fibrosis.[10] Some strains causepneumonia in general intensive care units (ICUs) and pediatricICUs. Clinically significant strains have been found in thehospital plumbing system, suggesting that drinking water maycontribute to nosocomial infections. A list of nosocomialoutbreaks associated with P. aeruginosa in contaminateddrinking water appears in Highsmith et al. (1986). However,the linking between the water distribution system (as opposedto the hospital plumbing system) and the presence of clinicallyimportant strains of P. aeruginosa in the nosocomial setting isstill open to question [11]. Numerous changes in generegulation cause the biofilm cells to become phenotypicallyand metabolically different from their planktonic counterparts[15]

ACKNOWLEDGMENT

The authors thank to Mr.Reza Javaherdashti for his valuablecomments in this research

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Pseudomona Aureginosa Corrosion 1