Differences in genetic and transcriptional organization of the glpTQ operons between Haemophilus influenzae type b and nontypeable strains

The glpTQ operon of Haemophilus influenzae type b (Hib) and nontypeable H. influenzae (NTHi) strains is highly conserved, except for a 1.4-kb glpTQ intergenic region that was found in most Hib strains. The presence of this intergenic region results in divergent glpTQ transcriptional profiles for Hib and NTHi where Hib strains appear to have evolved an alternative promoter for glpQ expression. Based on the intergenic region's low G+C content, we speculate that this DNA fragment was acquired by lateral transfer.