An in situ technique to measure bacterial chemotaxis in natural aquatic environments.

A simple and reliable technique to study bacterial chemotaxis in natural aquatic environments is reported. This technique uses the test chemicals in known volumes of semi-solid agar media placed in double layered, highly porous, polyester tubes. Following in situ incubation, bacteria attracted by the test chemicals are enumerated with fluorescence microscopy following acridine orange staining. Studies in an eutrophic reservoir showed that significant numbers of bacteria were attracted to D-glucose and glycine; no significant effects were observed with L-serine, sodium succinate, or sodium chloride.