glnD and mviN Are Genes of an Essential Operon in Sinorhizobium meliloti

Abstract
To evaluate the role of uridylyl-transferase, the Sinorhizobium meliloti glnD gene was isolated by heterologous complementation in Azotobacter vinelandii . The glnD gene is cotranscribed with a gene homologous to Salmonella mviN . glnD1 ::Ω or mviN1 ::Ω mutants could not be isolated by a powerful sucrose counterselection procedure unless a complementing cosmid was provided, indicating that glnD and mviN are members of an indispensable operon in S. meliloti .