TABLE 1 .

Conserved cotranscription of genes for complex-forming proteins

Genes	Complexa	Cotranscription (% of genera)b		No. of genera
		Likelyc	Unlikelyd
trpB-trpA	+	69	21	204
malF-malG	+	100	0	9
carA-carB	+	58	29	226
nrdA-nrdB	+	63	18	68
trpE-trpD	–	6	42	178
malE-malF	–	43	43	7
thrA-thrB	–	41	43	58
thrB-thrC	–	20	80	164

^a +E. coli: trpB-trpA, tryptophan synthase; malF-malG, maltose ABC transporter; carA-carB, carbamoyl phosphate synthetase; nrdA-nrdB, ribonucleoside diphosphate reductase. –, pairs cotranscribed in E. coli and used for the same pathway but are not complex forming (15).

^b Data shown for one representative member of each genus obtained from the JVCI-CMR database (bacterial and archaeal genomes) (16). Some gene pairs were absent in some genera.

^c Genes were judged likely to be cotranscribed when they were in the same orientation and the end of the upstream gene is <150 bp from the start of the other.

^d Genes were judged unlikely to be cotranscribed when the intergenic distance was larger than 5,000 bp or when the genes were in opposite orientations. Some gene pairs could not be placed into either of these categories.