The effect of humic substances isolated from a variety of marine and lacustrine environments on different microorganisms

The antimicrobial activity of twelve preparations of humic substances isolated from sea water, marine bottom sediments and lake water was examined. Humic substances from marine bottom sediment samples were fractionated into humic and/or fulvic acids. The susceptibility of 11 strains of anaerobic, 8str ains of aerobic bacteria and 2 strains of yeast-like fungi to preparations of humic substances, humic and/or fulvic acids was determined employing the plate dilution technique in Brucella agar (anaerobic bacteria), Mueller-Hinton agar (aerobic bacteria) and Sabouraud agar (yeast-like fungi). Concentrations from 150 to 600 μg ml−1 of the preparations examined inhibited the growth of numerous microorganisms (Table). The results obtained seem to indicate that humic substances are involved in the self-purification of sea and lake waters.