Table 1. Coding efficiency of experimentally determined essential vs. non-essential genes.

Organism	Data set	Coding efficiency
		All genes	Metabolic genes
E. coli	Gerdes et al., 2003 [10]	5.1e-9	7.7e-4
	Hashimoto et al., 2005 [11]	7.6e-51	3.3e-8
	Joyce et al., 2006 [12]	1.2e-18	7.3e-9
	Baba et al., 2006 [13]	2e-39	8.2e-7
S. cerevisiae	Giaever et al., 2002 [14]	8.6e-24	3.6e-4

P-values are reported, denoting the difference in coding efficiency between non-essential and essential genes in one-sided ranksum tests (checking for higher coding efficiency of essential genes). This analysis is done for all genes (left), as well as only including metabolic genes (right). The criterion for including a gene as ‘metabolic’ was that it exists in the E. coli or S. cerevisiae metabolic models.