engleski

Importance of hydrophilic polysaccharide capsule for marine bacterial adhesion to n-alkane phase

Different modes of cells adhesion to droplets of diesel fuel (mixture of n-alkanes: C12-C28) and n-hexadecane are identified for two Acinetobacter strains. Hydrophobic strain RAG-1 is known to excrete the lipopolysaccharide emulsan, whereas the newly isolated species VE-C3 (Baldi et al. 1997, Di Cello et al.1997) is hydrophilic due to the polysaccharide capsule production. The fluorescence distribution of glucose or mannose in the microbial capsule was observed using molecular probes such as lectine concanavalin-A conjugated with fluoresceine isothiocyanate and confocal laser microscopy (SCLM). By using the dropping mercury electrode as in situ adhesion sensor, quantitative differences were found in biofilm formation, as well as in the mode of oil uptake. Microscopic investigations under SCLM and also under TEM by using concanavaline-A conjugated with ferritine clearly demonstrated the incorporation of n-alkane as nanodroplets into polysaccharide matrix of the capsule. The formation of a hydrophobic oil/polysaccharide nanocomposite sustains a continuous growth of VE-C3 biomass in oil degrading cultures over a prolonged period of time. These studies are extended to oil incorporation into polysaccharide gels (mucilage) during the massive macroaggregation phenomenon in the Northern Adriatic.

bacterial adhesion; bacterial polysacharide; biodegradation; marine environment

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