Characterization of glycoconjugates of extracellular polymeric substances in tufa-associated biofilms by using fluorescence lectin-binding analysis.

Freshwater tufa deposits are the result of calcification associated with biofilms dominated by cyanobacteria. Recent investigations highlighted the fact that the formation of microbial calcium carbonates is mainly dependent on the saturation index, which is determined by pH, the ion activity of Ca(2+) and CO(3)(2-), and the occurrence of extracellular polymeric substances (EPS) produced by microorganisms. EPS, which contain carboxyl and/or hydroxyl groups, can strongly bind cations.

In situ detection of bacteria in calcified biofilms using FISH and CARD-FISH.

Modified protocols of fluorescence in situ hybridization (FISH) and catalyze reporter deposition fluorescence in situ hybridization (CARD-FISH) were developed in order to detect bacteria in situ in calcified stromatolite biofilms. Smooth, well-preserved thin sections of calcified biofilms (approximately 5 microm thin, vertical sectioning of approximately 1 cm deep) were obtained by cryo-sectioning using the adhesive tape-stabilization technique. A modified hybridization buffer was applied during hybridization to prevent calcite dissolution as well as false binding of oligonucleotide probes to the charged mineral surfaces.

A flow-lane incubator for studying freshwater and marine phototrophic biofilms.

Phototrophic biofilms are defined as interfacial microbial communities mainly driven by light as energy source and are studied for both ecological and technological reasons. Field investigations of biofilms usually do not offer the opportunity to study the effects of a large number of external parameters. In order to investigate the temporal development of phototrophic communities a laboratory flow-lane incubator for cultivation of freshwater and marine biofilms was developed.

Stochastic modeling for characterisation of biofilm development with discrete detachment events (sloughing).

The monitoring of biofilm development at a small-scale is often observed to be a stochastic process. This raises important issues concerning the reproducibility of biofilm growth monitoring experiments. By realising that there are limits to the latter, a model of biofilm accumulation curves that takes into account the dynamics of seemingly random fluctuations resulting from sloughing events is proposed.

On the reproducibility of microcosm experiments - different community composition in parallel phototrophic biofilm microcosms.

Phototrophic biofilms were cultivated simultaneously using the same inoculum in three identical flow-lane microcosms located in different laboratories. The growth rates of the biofilms were similar in the different microcosms, but denaturing gradient gel electrophoresis (DGGE) analysis of both 16S and 18S rRNA gene fragments showed that the communities developed differently in terms of species richness and community composition. One microcosm was dominated by Microcoleus and Phormidium species, the second microcosm was dominated by Synechocystis and Phormidium species, and the third microcosm was dominated by Microcoleus- and Planktothrix- affiliated species.