Microscale and Molecular Assessment of Impacts of Nickel, Nutrients, and Oxygen Level on Structure and Function of River Biofilm Communities

Abstract

Studies were carried out to assess the influence of nutrients, dissolved oxygen (DO) concentration, and nickel (Ni) on river biofilm development, structure, function, and community composition. Biofilms were cultivated in rotating annular reactors with river water at a DO concentration of 0.5 or 7.5 mg liter ؊1 , with or without a combination of carbon, nitrogen, and phosphorus (CNP) and with or without Ni at 0.5 mg liter ؊1 . The effects of Ni were apparent in the elimination of cyanobacterial populations and reduced photosynthetic biomass in the biofilm. Application of lectin-binding analyses indicated changes in exopolymer abundance and a shift in the glycoconjugate makeup of the biofilms, as well as in the response to all treatments. Application of the fluorescent live-dead staining (BacLight Live-Dead staining kit; Molecular Probes, Eugene, Oreg.) indicated an increase in the ratio of live to dead cells under low-oxygen conditions. Nickel treatments had 50 to 75% fewer 'live' cells than their corresponding controls. Nickel at 0.5 mg liter ؊1 corresponding to the industrial release rate concentration for nickel resulted in reductions in carbon utilization spectra relative to control and CNP treatments without nickel. In these cases, the presence of nickel eliminated the positive influence of nutrients on the biofilm. Other culture-dependent analyses (plate counts and most probable number) revealed no significant treatment effect on the biofilm communities. In the presence of CNP and at both DO levels, Ni negatively affected denitrification but had no effect on hexadecane mineralization or sulfate reduction. Analysis of total community DNA indicated abundant eubacterial 16S ribosomal DNA (rDNA), whereas Archaea were not detected. Amplification of the alkB gene indicated a positive effect of CNP and a negative effect of Ni. The nirS gene was not detected in samples treated with Ni at 0.5 mg liter ؊1 , indicating a negative effect on specific populations of bacteria, such as denitrifiers, resulting in a reduction in diversity. Denaturing gradient gel electrophoresis revealed that CNP had a beneficial impact on biofilm bacterial diversity at high DO concentrations, but none at low DO concentrations, and that the negative effect of Ni on diversity was similar at both DO concentrations. Notably, Ni resulted in the appearance of unique bands in 16S rDNA from Ni, DO, and CNP treatments. Sequencing results confirmed that the bands belonged to bacteria originating from freshwater and marine environments or from agricultural soils and industrial effluents. The observations indicate that significant interactions occur between Ni, oxygen, and nutrients and that Ni at 0.5 mg liter ؊1 may have significant impacts on river microbial community diversity and function.

Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment

“…Changes in exopolymer structure, abundance and composition are reported to be commonly induced by heavy metal stress in biofilms; however, the changes do not follow a universal pattern. Marine biofilms increase EPS production in response to several heavy metals, including copper (Fang et al, 2002), while EPS content of river biofilms substantially declines on exposure to Ni(II) (Lawrence et al, 2004). The carbohydrate/protein ratio is frequently altered by heavy metals, but the changes observed vary widely in different studies (Jang et al, 2001;Lawrence et al, 2004).…”

“…Experiments carried out under controlled conditions are essential to verify the impact of pollutants on microbial ecosystems (Lawrence et al, 2004). In this study, the combination of different microbiological, analytic, microscopic and molecular techniques allowed the characterization of the biological adaptation of the microbial biofilm and the evolution of its community composition in response to copper stress in a laboratory-scale aerobic biofilter designed for the decontamination of groundwater polluted with Cu(II).…”

“…Marine biofilms increase EPS production in response to several heavy metals, including copper (Fang et al, 2002), while EPS content of river biofilms substantially declines on exposure to Ni(II) (Lawrence et al, 2004). The carbohydrate/protein ratio is frequently altered by heavy metals, but the changes observed vary widely in different studies (Jang et al, 2001;Lawrence et al, 2004). Modifications in EPS composition of biofilms are attributed to the selective pressure of the heavy metals on the community, which favours bacterial populations producing an EPS having the characteristics that confer resistance to a particular metal ion (Lawrence et al, 2004).…”

Elevated seawater temperature causes a microbial shift on crustose coralline algae with implications for the recruitment of coral larvae

“…Biofilm age and depth can affect the inductive and inhibitory capacities of biofilms (Wieczorek and Todd, 1997;Webster et al, 2004), and localised anthropogenic impact can also shift the biofilm composition (Meyer-Reil and Koster, 2000;Lawrence et al, 2004) and potentially influence subsequent invertebrate recruitment (Webster et al, 2006). However, to date no research has addressed how variables associated with a changing climate (elevated sea-surface temperature (SST), ocean acidification and eutrophication) will affect the inductive ability of marine microbial biofilms.…”

Shifts in Root-Associated Microbial Communities ofTypha LatifoliaGrowing in Naphthenic Acids and Relationship to Plant Health

“…essentially as described by Lawrence et al, (2004). For each treatment, 300 ng of amplified 16S rRNA gene product was loaded per lane onto an 8% acrylamide gel with a 40-60% urea-formamide denaturing gradient.…”