Contents

16 April 1999
Vol 284, Issue 5413

About The Cover

Cover image expansion

COVER A large sulfur bacterium, Thiomargarita, was discovered in sediments off the coast of Namibia that breaks records of size among bacteria. The photomicrograph shows three cells under polarized light (middle cell is ~0.2 mm in diameter), and the small yellow spheres are sulfur globules that are restricted to the thin outer layer of the cell. These bacteria oxidize sulfide using nitrate, coupling the nitrogen and sulfur cycles in the sediment. See page 493.[Image: Ferran Garcia-Pichel]