Bacterial Biofilms Formed in Arsenic-containing Water: Bacterial Community Characterization

Abstract

The present study approaches the analyses of structure and diversity of bacterial biofilms formed on different water distribution materials in the absence and in the presence of 5mg/L of As(V). Three commercial metals (cast iron, zinc and copper) and polypropylene were used as substrata for biofilm formation. Biofilms were observed using Scanning Electron Microscopy (SEM). Microbial ecology techniques (DNA amplification by the Polymerase Chain Reaction (PCR) and Denaturing Gradient Gel Electrophoresis (DGGE)) were applied to study the bacterial community attached to each substratum. The presence of arsenic-tolerant bacteria was investigated. The microscopic observations showed that biofilm development resulted higher on those coupons exposed to the arsenic-containing water. Besides, the presence of arsenic induced qualitative and quantitative changes in the planktonic bacterial community. The clustering analysis of the sessile community profiles 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. Culturable As-tolerant bacteria were obtained from most of the biofilms. The genetic diversity of the community adapted to the presence of the contaminant was less affected by the high concentration of As(V) in the culture, reflecting the presence of populations adapted to the contaminant.