Map of pSymA. The position of the first nucleotide (denoted 1) was assigned adjacent to and clockwise from the repABC genes and putative origin of replication (6). Selected genes and regions mentioned in text are labeled. Locations of insertion sequence (IS) elements and IS fragments are marked with colored triangles. Additional information on IS elements is available in ref. 6 and at the genome web site (http://sequence.toulouse.inra.fr/meliloti.html). Putative chemotaxis genes (che), pilus assembly genes (pil), and NADH–ubiquinone dehydrogenase genes (nuo) are discussed in a concurrent publication (6). Sites of infrequently cutting restriction enzymes (SwaI, PacI, and PmeI) are marked. SMA designations for regions shown on the map are: tRNA-sec, SMa0011; groESL3, SMA0124–125; pilQ, SMA0163; gdhA, SMA0228; gabD3, SMA0260; fdh, SMA0478; idn, SMA0512–514; nrt, SMA0581–585; fix-3, SMA0612–622; arcABC, SMA0693–697; groESL2, SMA0744–745; fix-2, SMA0760–769; gabD4, SMA0805; nif, SMA0825–831; nod, SMA0840–878; dnaE3, SMA0892; oriT, SMa4018; att, SMA0950–958; fixL-like, SMA1142; nos, SMA1179–1188; fix-1, SMA107–1229; nir, SMA1247–1250; nor, SMA1269–1279; vir, SMA1302–1321; nuo, SMA1516–1536; che/pil, SMA1552–1578; arcDA, SMA1667–1670; argI2, SMA1711; bet, SMA1726–1731; iron uptake, SMA1740–1747; argE, SMA1836; gabD5, SMA1848; sulfur metabolism, SMA2067–2103; glyA2, SMA2135; tRNA-met, SMa2168; opine metabolism, SMA2223–2225; and oriV, SMa4019.