Effects of iron and chelation on Lake Kinneret bacteria.

The response of natural populations of bacteria (prepared by passing Lake Kinneret water through 1 μm filters) to additions of Fe(2+) and/or the chelator ethylenediaminetetraacetic acid (EDTA) was followed by measuring the incorporation of (3)H-thymidine into >0.2 μm particulates, and also by determining the increments in cell numbers after 24 h. In most cases, a stimulation of (3)H-thymidine incorporation was observed in supplemented samples relative to untreated controls after 3 and 24 h incubation. The increase in bacterial numbers was also enhanced by these supplements. Generally, EDTA alone evoked a greater stimulation than Fe(2+); combined supplements gave no further increase. This response pattern appeared consistently throughout the year in samples taken from near-surface lake waters. These results suggest that the availability of iron or chelators may play an important role in regulating bacterial metabolism and growth even in aquatic ecosystems like Lake Kinneret where ambient concentrations of total Fe are relatively high.