Characterization of biofilm formation on a humic material

Abstract

Biofilms are major sites of carbon cycling in streams. Therefore, it is crucial to improve knowledge about biofilms' structure and microbial composition to understand their contribution in the self-purification of surface water. The present work intends to study biofilm formation in the presence of humic substances (HSs) as a carbon source. Two biofilm flowcells were operated in parallel; one with synthetic stream water, displaying a background carbon concentration of 1.26+/-0.84 mg L(-1), the other with added HSs and an overall carbon concentration of 9.68+/-1.00 mg L(-1). From the biofilms' results of culturable and total countable cells, it can be concluded that the presence of HSs did not significantly enhance the biofilm cell density. However, the biofilm formed in the presence of HSs presented slightly higher values of volatile suspended solids (VSS) and protein. One possible explanation for this result is that HSs adsorbed to the polymeric matrix of the biofilm and were included in the quantification of VSS and protein. The microbial composition of the biofilm with addition of HSs was characterized by the presence of bacteria belonging to beta-Proteobacteria, Cupriavidus metallidurans and several species of the genus Ralstonia were identified, and gamma-Proteobacteria, represented by Escherichia coli. In the biofilm formed without HSs addition beta-Proteobacteria, represented by the species Variovorax paradoxus, and bacteria belonging to the group Bacteroidetes were detected. In conclusion, the presence of HSs did not significantly enhance biofilm cell density but influenced the bacterial diversity in the biofilm.

Characterization of refractory organic substances by NEXAFS using a compact X-ray source

“…This procedure has also been applied to the other spectra. The middle part of Table 1 shows the outcome of our study on the HA from Sigma Aldrich in comparison with published data from Monteil-Rivera et al (2000) and Rodrigues et al (2008). Our approximation of the elemental compositions yields values close to the analytical data, directly taken from the supply company, Sigma Aldrich.…”

“…The information yielded by the polyimide spectrum was helpful to characterize the second reference sample, a wellinvestigated HA standard sample (Monteil-Rivera et al 2000;Sierra et al 2005;Plucinski et al 2007;Rodrigues et al 2008). The spectrum is displayed in Fig.…”

Humic Acid-Oxidizing, Nitrate-Reducing Bacteria in Agricultural Soils

“…Further supporting our findings based on pure culture and community results, a recent study also identified the dominance of 16S rRNA gene sequences from the Burkholderiales , Ralstonia , and Cupriavidus spp. in reduced HA biofilms but not detected in controls not treated with humic acid (38). …”

Soft x-ray spectromicroscopy of environmental and biological samples

“…The information gained from the PI spectrum was helpful to characterize the second reference sample, a well investigated HA [125,146,155,173], a widely used standard sample, purchased from Sigma Aldrich. The spectrum is displayed in Fig.…”