Researchers Say Pollutants Affect Marine Bacteria

Investigators at Harvard have found that chemical pollutants seriously cripple the capacity of marine bacteria to find food, and so may threaten the essential role of bacteria in the ocean food chain.

Bacteria keep the ocean clean and fertile by degrading dead plants and animals into essential nutrients.

The discovery came as a result of research by Samuel Fogel and Ilan Chet, research fellows in Applied Biology, and Ralph Mitchell, McKay Professor of Applied Biology.

The group presented its paper entitled "The Ecological Significance of Bacterial Chemotaxis" at a meeting of the American Society for Microbiology last week in Minneapolis, Minn.

Chemotaxis is the ability of bacteria to sense chemicals.

Food Finder

The three scientists found that bacteria's ability to sense chemicals-which has been known for over 60 years-may help the bacteria find food. They discovered ten different types of "representative" bacteria which were attracted to several specific chemicals-including nutrients.

Since each type of bacteria responded to the chemicals in a different way, Foget suggested that bacteria be classified on the basis of their ability to detect certain chemicals.

Building on the hypothesis that bac-teria use chemotaxis to locate food, Fogel, Chet and Mitchell investigated the effects of chemical pollutants on bacterial sensing mechanisms. They found that many of the bacteria tested could not detect food when small, non-lethal amounts of organic chemicals such as alcohol's were added to the seawater.

The concentration of pollutants needed to inhibit the chemotaxis of bacteria may reasonably be found in nature. Fogel concluded, Chet and Mitchell speculate that pollutants might concentrate in small areas of the ocean and prevent bacteria from finding food or purifying the water.

Although the research team only studied marine bacteria, Mitchell said wouldn't get exactly the same results there was "no reason to believe that we with ... any other bacteria." Thus, the cleansing action of bacteria in fresh water may also be affected by the pollutants.