AME 38:283-294 (2005)  -  doi:10.3354/ame038283

ABSTRACT: Biofilms were cultivated in rotating annular reactors supplied with river water supplemented with carbon, nitrogen, phosphorus or a combined nutrient addition. Confocal laser scanning microscopy and digital image analysis were used in combination with a panel of fluor-conjugated lectin probes to assess the changes in biofilm glycoconjugates with depth, time and in response to the nutrient additions. In addition, nucleic acid staining and autofluorescence were utilised to monitor bacterial and photosynthetic populations respectively. These analyses indicated that in lotic biofilms both quantitative and proportional differences in glycoconjugate composition developed under each nutrient regime. The differences in the biofilms were detected with time and with depth. Comparison of C, N, P, and CNP treatments with the control showed differences in the total amount of photosynthetic organisms, bacteria and extracellular polymeric substance (EPS)-specific glycoconjugates. For example, C, N, and CNP nutrient additions resulted in a minimal increase of 50% lectin-specific EPS glycoconjugates. Accumulation of different glycoconjugates over time in the different biofilms showed a similar pattern in the single nutrient treatments, with a maximum accumulation at 3 wk, followed by sloughing in Week 5 and regrowth in Week 7. In contrast, both the control and the combined CNP treatment showed a continuous increase and a plateau phase for the glycoconjugates as a whole. Both visualisation and quantification indicated that under each treatment the distribution of 4 specific glycoconjugates (Arachis hypogaea, Canavalia ensiformis, Glycine max, Ulex europaeus) varied with depth and, in addition, changed over time. Further, the glycoconjugate make-up of the single nutrient additions were similar to each other, as was the make-up of the control and combined nutrient treatment. Application of fluorescence in situ hybridisation analysis indicated that significant changes occurred in the beta-proteobacteria community composition as a consequence of nutrient addition. The results demonstrate the effect of nutrient regime on the cellular composition and glycoconjugate chemistry of lotic biofilms.

KEY WORDS: Biofilms · Lectins · Extracellular polymeric substances · EPS · Glycoconjugates · Nutrients · Fluorescence · Confocal laser scanning microscopy · CLSM