Phasevarion of non-typeable Haemophilus influenzae R2866

H. influenzae R2866 contains a phase-variable DNA methylase modA10, by virtue of 16 tetrameric repeats present after the start codon. Gain or loss of repeats during replication by slipped-strand mispairing can result in a non-functional reading frame. Microarray analyses of wild-type and insertionally inactivated modA were performed to determine genes affected by phase variable modification. Three replicate cultures were grown in either supplemented brain heart infusion broth (R2866 and R3763) or chemically defined media (R3790 and R3791) to an optical density at 600nm of 0.3 to 0.4 (mid-log phase). RNA was isolated by the method of Jahn et al.