Bloomington, Ind. -- The constellation of shapes and sizes among bacteria is as remarkable as it is mysterious. Why should Spirochaeta halophila resemble a bedspring coil, Stella a star and Clostridium cocleatum a partly eaten donut? No one really knows.

A new report in the Proceedings of the National Academy of Sciences by Indiana University Bloomington scientists answers that form-and-function question for one bacterium, the aquatic Caulobacter crescentus, whose cells are anchored to solid objects by conspicuous and distinctive stalks.

"We've found the bacteria can take up nutrients with their stalks," said microbiologist Yves Brun, who led the study. "This is the first example that we know of in which a major feature of a bacterium's shape can be tied to a specific function."

Despite their tiny size and readiness for laboratory study, far less is known about the physiological utility of bacterial shapes than, say, the streamlined forms of fish, sharks and dolphins, or the elongated spires of pine and redwood trees.

Brun said C. crescentus' stalk acts as a sort of antenna that amplifies the uptake of organic phosphate from the surrounding environment. The narrow stalk adds little volume to the cell, and incoming nutrients diffuse toward the cell's main body, where nutrients are quickly assimilated by metabolic processes. Phosphate is an important molecule to all organisms. It is involved in DNA repair and duplication, the expression of DNA, the regulation of protein action, membrane synthesis and the transfer of energy within cells.

The scientists used fluorescence microscopy to see where organic phosphate enters C. crescentus cells. As a gram negative bacterium, C. crescentus has two membranes -- an outer membrane and an inner membrane, with a space called the "periplasm" in between. Experiments demonstrated initial entry of organic phosphate across the entire cell surfac
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Contact: David Bricker
brickerd@indiana.edu
812-856-9035
Indiana University
18-Jul-2006