Autoinducer 2 (AI-2) Production by Nontypeable Haemophilus influenzae 86-028NP Promotes Expression of a Predicted Glycosyltransferase That Is a Determinant of Biofilm Maturation, Prevention of Dispersal, and Persistence .

Nontypeable (NT) is an extremely common human pathobiont that persists on the airway mucosal surface within biofilm communities, and our previous work has shown that NT biofilm maturation is coordinated by the production and uptake of autoinducer 2 (AI-2) quorum signals. To directly test roles for AI-2 in maturation and maintenance of NT biofilms, we generated an NT 86-028NP mutant in which transcription was under the control of the promoter (NT 86-028NP ::), rendering AI-2 production inducible by xylose. Comparison of biofilms under inducing and noninducing conditions revealed a biofilm defect in the absence of xylose, whereas biofilm maturation increased following xylose induction. The removal of xylose resulted in the interruption of expression and biofilm dispersal. Measurement of transcript levels by real-time reverse transcription-PCR (RT-PCR) showed that expression peaked as biofilms matured and waned before dispersal. Transcript profiling revealed significant changes following the induction of , including increased transcript levels for a predicted family 8 glycosyltransferase (NTHI1750; designated ); this result was confirmed by real-time RT-PCR. An isogenic NT 86-028NP mutant had a biofilm defect, including decreased levels of sialylated matrix and significantly altered biofilm structure. In experimental chinchilla infections, we observed a significant decrease in the number of bacteria in the biofilm population (but not in effusions) for NT 86-028NP compared to the parental strain. Therefore, we conclude that AI-2 promotes NT biofilm maturation and the maintenance of biofilm integrity, due at least in part to the expression of a probable glycosyltransferase that is potentially involved in the synthesis of the biofilm matrix.