Influence of As (V) on the diversity of biofilms formed on different substrata

Microorganisms, including bacteria, present in natural and artificial aquatic environments, tend to attach to and grow on immersed surfaces developing a biofilm. Many problems in drinking water networks such as corrosion, persistence of pathogenic species and increased resistance to biocides are due to the presence of biofilms. Arsenic is a contaminant widely distributed in the Argentinean underground water. Despite arsenic’s toxicity, a number of microorganisms are capable of growing in arsenic environments playing an important role in the process of arsenic mobilization. The aim of this work was to study the influence of As (V) on the bacterial planktonic community and biofilms structures grown on different drinking water distribution materials. To simulate a water distribution system, two tanks with a closed loop of polypropylene (PP) tubes were built and filled with drinking water. As(V) (5 mg L-1) was added in one of the tanks. Coupons of four materials were place in the loops for biofilm formation: commercial iron (Fe), commercial zinc (Zn), copper (Cu) and PP. Bacterial planktonic and sessile communities were analysed by culture (heterotrophic plate counts) and molecular (DNA extraction, PCR, sequencing, DGGE) techniques. Bacterial counts on Fe and Zn were higher than those obtained on Cu and PP and, except for Cu, they were higher in the presence of 5mg.L-1 of As(V). Culturable Astolerant bacteria able to grow in the presence of high As(V) concentration (up to 1g.L-1) were obtained from all the biofilms except Cu-biofilms, which grew in the presence of up to 300mg.L-1 As(V). It was possible to isolate and identify 60 colonies corresponding: 40% to the Class Bacilli, 40% α-Proteobacteria (both Classes were found in all the biofilms), 10% Actinobacteria (detected in biofilms formed on Fe in the absence of As, Cu and PP in the presence of As), 8% β-Proteobacteria (found on Fe, Zn and PP biofilms in the presence of As) and 2% γ-Proteobacteria (detected only in biofilms formed on Zn in the absence of As). The DGGE profiles of the planktonic bacterial communities were qualitative and quantitative affected by the presence of arsenic. In general, the planktonic community developed in the water without As showed higher richness and diversity indices, indicating that the presence of a toxic element induced a selection of the species in the water with Arsenic. In the case of the sessile communities, the trends were not so clear. The clustering analysis of the sessile communities showed that the nature of the substrata was a more important factor for the establishment of the community than the presence of arsenic in water.Centro de Investigación y Desarrollo en Tecnología de Pintura

Influence of As (V) on the diversity of biofilms formed on different substrata

Microorganisms, including bacteria, present in natural and artificial aquatic environments, tend to attach to and grow on immersed surfaces developing a biofilm. Many problems in drinking water networks such as corrosion, persistence of pathogenic species and increased resistance to biocides are due to the presence of biofilms. Arsenic is a contaminant widely distributed in the Argentinean underground water. Despite arsenic’s toxicity, a number of microorganisms are capable of growing in arsenic environments playing an important role in the process of arsenic mobilization. The aim of this work was to study the influence of As (V) on the bacterial planktonic community and biofilms structures grown on different drinking water distribution materials. To simulate a water distribution system, two tanks with a closed loop of polypropylene (PP) tubes were built and filled with drinking water. As(V) (5 mg L-1) was added in one of the tanks. Coupons of four materials were place in the loops for biofilm formation: commercial iron (Fe), commercial zinc (Zn), copper (Cu) and PP. Bacterial planktonic and sessile communities were analysed by culture (heterotrophic plate counts) and molecular (DNA extraction, PCR, sequencing, DGGE) techniques. Bacterial counts on Fe and Zn were higher than those obtained on Cu and PP and, except for Cu, they were higher in the presence of 5mg.L-1 of As(V). Culturable Astolerant bacteria able to grow in the presence of high As(V) concentration (up to 1g.L-1) were obtained from all the biofilms except Cu-biofilms, which grew in the presence of up to 300mg.L-1 As(V). It was possible to isolate and identify 60 colonies corresponding: 40% to the Class Bacilli, 40% α-Proteobacteria (both Classes were found in all the biofilms), 10% Actinobacteria (detected in biofilms formed on Fe in the absence of As, Cu and PP in the presence of As), 8% β-Proteobacteria (found on Fe, Zn and PP biofilms in the presence of As) and 2% γ-Proteobacteria (detected only in biofilms formed on Zn in the absence of As). The DGGE profiles of the planktonic bacterial communities were qualitative and quantitative affected by the presence of arsenic. In general, the planktonic community developed in the water without As showed higher richness and diversity indices, indicating that the presence of a toxic element induced a selection of the species in the water with Arsenic. In the case of the sessile communities, the trends were not so clear. The clustering analysis of the sessile communities showed that the nature of the substrata was a more important factor for the establishment of the community than the presence of arsenic in water.Centro de Investigación y Desarrollo en Tecnología de Pintura

Effect of arsenic on microorganisms and biofilms in MIC of water network materials

Microorganisms in natural and artificial aquatic environments attach to wet surfaces to form a biofilm (Dexter, 2003), which causes problems such as microbially induced corrosion (MIC), increased resistance to biocides and persistence of pathogenic species. Arsenic (As) is being increasingly detected in distribution water services, generating serious sanitary and social problems throughout the Planet (Pontius et al. 1994; Masud Karim 2000). The existence of bacterial species able to grow in the presence of high concentrations of this chemical is well known (Oremland and Stolz 2005). The development of molecular techniques has allowed the study of microbial communities (Muyzer 1999). Among these techniques denaturing gradient gel electrophoresis (DGGE) is commonly used for genetic fingerprint analysis of microbial community composition, diversity and dynamics (Green et al. 2009). Electron microscopy techniques such as scanning electron microscopy (SEM) and environmental SEM (ESEM) have been important for high resolution visualization of bacterial biofilm outer surfaces. The main purpose of this work was to shed light on the effect of As(V) on the sessile bacterial communities produced on four substrata used in water distribution systems and their correlation with susceptibility to MIC of these substrata, using molecular biology and microscope techniques.Centro de Investigación y Desarrollo en Tecnología de Pintura

Effect of arsenic on microorganisms and biofilms in MIC of water network materials

Microorganisms in natural and artificial aquatic environments attach to wet surfaces to form a biofilm (Dexter, 2003), which causes problems such as microbially induced corrosion (MIC), increased resistance to biocides and persistence of pathogenic species. Arsenic (As) is being increasingly detected in distribution water services, generating serious sanitary and social problems throughout the Planet (Pontius et al. 1994; Masud Karim 2000). The existence of bacterial species able to grow in the presence of high concentrations of this chemical is well known (Oremland and Stolz 2005). The development of molecular techniques has allowed the study of microbial communities (Muyzer 1999). Among these techniques denaturing gradient gel electrophoresis (DGGE) is commonly used for genetic fingerprint analysis of microbial community composition, diversity and dynamics (Green et al. 2009). Electron microscopy techniques such as scanning electron microscopy (SEM) and environmental SEM (ESEM) have been important for high resolution visualization of bacterial biofilm outer surfaces. The main purpose of this work was to shed light on the effect of As(V) on the sessile bacterial communities produced on four substrata used in water distribution systems and their correlation with susceptibility to MIC of these substrata, using molecular biology and microscope techniques.Centro de Investigación y Desarrollo en Tecnología de Pintura

Microscopy applied to biofilms in drinking water closed loop

During water distribution operation, tubing material is submitted to permanent contact with aquatic microbial species. They colonise the network surface forming biofilms which frequently cause corrosion on metallic substrata. The present study approaches the analyses of laboratory biofilms formed on water pipe materials from several (SEM, ESEM, CLSM) microscopy technique point of view and also from a microbial ecological analysis using DGGE for the study of the communities formed on each substrate. Microbial interactions with the different materials were described using an ample range of magnification. Three commercial metals (Fe, Zn, Cu) and polypropylene tubing used as substrata revealed very different behaviours. Even when it was possible to distinguish different attack morphologies and the biofilms 3-D structures formed on all materials it was not already established a clear correlation with the genetic profile of each community.Centro de Investigación y Desarrollo en Tecnología de PinturasCentro de Investigación y Desarrollo en Fermentaciones Industriale

Effect of arsenic on microorganisms and biofilms in MIC of water network materials

Microorganisms in natural and artificial aquatic environments attach to wet surfaces to form a biofilm (Dexter, 2003), which causes problems such as microbially induced corrosion (MIC), increased resistance to biocides and persistence of pathogenic species. Arsenic (As) is being increasingly detected in distribution water services, generating serious sanitary and social problems throughout the Planet (Pontius et al. 1994; Masud Karim 2000). The existence of bacterial species able to grow in the presence of high concentrations of this chemical is well known (Oremland and Stolz 2005). The development of molecular techniques has allowed the study of microbial communities (Muyzer 1999). Among these techniques denaturing gradient gel electrophoresis (DGGE) is commonly used for genetic fingerprint analysis of microbial community composition, diversity and dynamics (Green et al. 2009). Electron microscopy techniques such as scanning electron microscopy (SEM) and environmental SEM (ESEM) have been important for high resolution visualization of bacterial biofilm outer surfaces. The main purpose of this work was to shed light on the effect of As(V) on the sessile bacterial communities produced on four substrata used in water distribution systems and their correlation with susceptibility to MIC of these substrata, using molecular biology and microscope techniques.Centro de Investigación y Desarrollo en Tecnología de Pintura

Microscopy applied to biofilms in drinking water closed loop

During water distribution operation, tubing material is submitted to permanent contact with aquatic microbial species. They colonise the network surface forming biofilms which frequently cause corrosion on metallic substrata. The present study approaches the analyses of laboratory biofilms formed on water pipe materials from several (SEM, ESEM, CLSM) microscopy technique point of view and also from a microbial ecological analysis using DGGE for the study of the communities formed on each substrate. Microbial interactions with the different materials were described using an ample range of magnification. Three commercial metals (Fe, Zn, Cu) and polypropylene tubing used as substrata revealed very different behaviours. Even when it was possible to distinguish different attack morphologies and the biofilms 3-D structures formed on all materials it was not already established a clear correlation with the genetic profile of each community.Centro de Investigación y Desarrollo en Tecnología de PinturasCentro de Investigación y Desarrollo en Fermentaciones Industriale

Metallurgical Factors Affecting Microbial Colonisation and Corrosion of Drinking Water Network Materials

The present work reports the studies performed to investigate the influence of some metallurgical factors in the microbial colonisation and corrosion of drinking water network materials. Cold rolling process applied to row materials submitted to drinking water dynamic tests seems not to affect substrata areas colonisation distribution as compared to as received condition of tubing materials. However, samples exposed to hydrodynamic and static tests with three different accumulated plastic deformation show diverse magnitude of localised attack but non-correlative with the substrata surface energy.Centro de Investigación y Desarrollo en Tecnología de Pintura

Metallurgical Factors Affecting Microbial Colonisation and Corrosion of Drinking Water Network Materials

The present work reports the studies performed to investigate the influence of some metallurgical factors in the microbial colonisation and corrosion of drinking water network materials. Cold rolling process applied to row materials submitted to drinking water dynamic tests seems not to affect substrata areas colonisation distribution as compared to as received condition of tubing materials. However, samples exposed to hydrodynamic and static tests with three different accumulated plastic deformation show diverse magnitude of localised attack but non-correlative with the substrata surface energy.Centro de Investigación y Desarrollo en Tecnología de Pintura

Evaluation of biofilms formation and corrosion of steel by microscopic techniques and electrochemical impedance spectroscopy

A clean metal surface which contacts natural or industrial waters undergoes a series of processes that lead to the formation of inorganic deposits and biofilms. In these structures, microorganisms adhere irreversibly to the substrate, embedded in a matrix of extracellular polymeric substances (EPS). The problems arising from biofilm formation, such as microbiologically influenced corrosion (MIC), loss of equipment performance, product damages, generate economic costs and may lead to structural failures with consequences for operators and/or users. The aim of this study was to evaluate the corrosion associated with the formation of bacterial biofilms on carbon steel surfaces. Bacterial cultures used in the experiments were isolated from different systems that presented MIC. SAE 1010 carbon steel coupons were placed in cultures for biofilm development. After 48 h coupons were extracted and bacterial adherence was measured by viable bacteria counts, epifluorescence microscopy, crystal violet assay and EPS quantification. The biofilm morphology was analyzed by scanning electron microscopy (SEM) and epifuorescence microscopy. Surface deterioration was monitored using electrochemical impedance spectroscopy and open circuit potential measurements. Studies carried out allowed correlating the adherence of the tested strains with the degree of attack suffered by the SAE 1010 carbon steel coupons.Centro de Investigación y Desarrollo en Tecnología de Pintura