Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): Altered development in an alfalfa root nodule formed by a Sinorhizobium meliloti mutant with impaired C4-dicarboxylic acid transport. The cross section shows uninfected plant cells (no dark inclusions), infected plant cells with developing bacteroids (numerous small dark bodies), and infected cells with infection threads (larger dark inclusions). Infected cells have an almost continuous line of starch granules at their periphery, while uninfected cells have prominent starch granules throughout the cell. This pattern is even more obvious when the starch is stained with iodine. These nodules do not fix nitrogen. (See related article on page 1161.)