Aims: To obtain a bacterial strain that can be used to quantify biodegradable polysaccharides at concentrations of a few micrograms per litre in freshwater.
Methods and results: Flavobacterium johnsoniae strain A3 was isolated from tap water supplemented with laminarin, pectin or amylopectin at 100 microg C l(-1) and river Rhine water. The organism utilized 14 of 23 oligo- and polysaccharides, and 1 of 9 monosaccharides, but none of the sugar acids, sugar alcohols, carboxylic acids or aromatic acids tested at 10 microg C l(-1). Amino acids promoted growth of strain A3, but not in coculture with assimilable organic carbon (AOC) test strain Pseudomonas fluorescens P17, which utilized these compounds more rapidly than strain A3. Compounds released by strain P17 and AOC test strain Spirillum sp. NOX grown on acetate promoted the growth of strain A3 at N(max) values of > or = 2 x 10(5) CFU ml(-1) of strain P17 and > or = 5 x 10(5) CFU ml(-1) of strain NOX. Significant growth of strain A3 was observed in surface water and in tap water in the presence of strain P17 (N(max) P17 < 2 x 10(5) CFU ml(-1)).
Conclusions: Strain A3 utilizes oligo- and polysaccharides at microgram-per-litre levels. In surface water and in tap water, the organism was able to utilize compounds that were not utilized by strain P17. These compounds may include oligo- and/or polysaccharides.
Significance and impact of the study: Phytoplanktonic and bacterial polysaccharides can constitute an important biodegradable fraction of natural organic matter in water and may promote growth of heterotrophic bacteria during water treatment and drinking water distribution. Strain A3 can be used to quantify a group of compounds that includes oligo- and polysaccharides at microgram-per-litre levels in freshwater.