Microbe holds fast.

A common aquatic microbe makes a sticky substance that produces "the strongest biological adhesion ever discovered;' says biophysicist Jay X. Tang of Brown University in Providence, R.I.

The adhesive might lead scientists to new water-resistant glues. The bacterium Caulobacter cres-centus begins its life as a mobile, tail-sporting cell. As it matures, it loses its tail, or flagellum, and replaces it with a stalk that it uses to attach to rocks or other surfaces. The tip of the stalk secretes an adhesive made of sugars and proteins.

Tang and his colleagues measured the strength of the adhesive, which scientists call holdfast. They grew the microbe on a thin, flexible micropipette, then pulled away its body. The team calculated holdfast's strength by measuring how far the micropopette bent before the microbe detached from it, says Tang.

The adhesive's strength measured 68 newtons per square millimeter ([N/mm.sup.2]), the researchers report in the April 11 Proceedings of the National Academy of Sciences. A single, hairlike protrusion on the toe of the much-studied gecko has an adhesive strength of about 10 [N/mm.sup.2].

A wet, 10-square-centimeter surface slathered with holdfast could potentially hold about 70 tons, Tang says.--A.C.