Microbe Magazine

Cover: Polished slice through a rock showing layers of a fossilized stromatolite. Each layer began as a covering of bluegreen algae (cyanobacteria), which captured grains of sediment and became mineralized. Over time layers accumulate to form a stromatolite, or rocky mound. Fossilized stromatolites as old as 3.5 billion years have been found, making them the oldest fossilized remains of life on Earth (see p. 75). (Image © Dirk Wiersma/Photo Researchers, Inc.) Microbe VOLUME 6, NUMBER 2 CODEN ASMBO 6 (2) 52-102 (2011) ISSN: 1558-7452 Microbe / Volume 6, Number 2, 2011