Examples of essential genes as determined by Tn-seq. An R. sphaeroides Tn5 mutant library was generated on rich (LB) plates grown aerobically. Transposon insertions were determined as described in the text. (A) Genomic region surrounding the essential genes RSP_1494 (putative aspartate aminotransferase), RSP_1495 (DNA translocase FtsK), and RSP_1497 (putative outer membrane lipoprotein carrier protein). (B) Genomic region surrounding the essential genes hisS (RSP_3551, histidyl-tRNA synthetase) and dnaE (RSP_3553, DNA polymerase III, α subunit).