Cover photograph (Copyright © 2003, American Society for Microbiology. All Rights Reserved.): Model RNA polymerase holoenzyme (coordinates from the Thermus thermophilus crystal structure) showing the positions of amino acids (orange and red) that are altered by mutations that rescue the defects of a Sinorhizobium meliloti relA mutant. Suppressor mutations map to either rpoB, the subunit (light aqua), or rpoC, the ` subunit (yellow ribbon). Since suppressors were selected in planta by their ability to restore symbiotic competence to the relA mutant, intricate coordination of bacterial metabolism by the stringent response may be required for successful interaction with host plants. (See related article on page 5602.)