MARINE MACROALGAE AS A SOURCE FOR OSMOPROTECTION FOR ESCHERICHIA-COLI

At elevated osmolarity of the mineral medium M63, marine macroalgae co nstitute important osmoprotectants and nutrients sources for Escherich ia coli. Growth of bacterial population (16 strains) was improved by s upplementing M63 salts medium with either aqueous or ethanolic algal e xtracts obtained from Ascophyllum nodosum, Fucus serratus, Enteromorph a ramulosa, Ulva lactuca, and Palmaria palmata. In their presence, gro wth was still observed even at 1.02 M NaCl. Furthermore, the E. coli Z B400 growth in presence of whole macroalgae thalli in M63/0.85 M NaCl reached its maximum within 24 h (5 X 10(7) - 5 X 10(8) colony-forming units [CFU] per milliliter). In the presence of A. nodosum, bacterial growth was inhibited. In the same experimental conditions, ethanolic e xtracts improved E. coli growth significantly, because the yield reach ed 10(11) CFU per milliliter. Ulva lactuca and P. palmata allowed the better growth. The Dragendorff-positive compounds extracted from bacte rial cells growing on each ethanolic extract exhibited an osmoprotecti ve effect as proved by a disk-diffusion assay. On the other hand, the -onium compounds (quaternary ammonium [betaines] and tertiary sulphoni um) and total free amino acid contents of U. lactuca ethanolic extract s were higher than in others. Fucaceae extracts demonstrated especiall y high protein content. Algal extracts constitute not only an apprecia ble osmoprotection source for E. coli but also nutrient sources.