Figure 2.

Distribution of neighboring genes involving at least one trp gene. (a) Each arrow connects neighboring genes, its size and color represents number of pairs found in the Sargasso metagenome (see legend, only pairs observed more than 30 times are shown). Pairs of genes composing the two split operons E→G→D→C and F→B→A are abundant while the pair C→F was rarely found. This may hint that the trp genes are usually organized as split operons rather than as full operons. (b) The representation of classical full and split trp operons.