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 In Vivo

Abstract

Nontypeable Haemophilus influenzae (NTHi) is an extremely common human pathobiont that persists on the airway mucosal surface within biofilm communities, and our previous work has shown that NTHi 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 NTHi biofilms, we generated an NTHi 86-028NP mutant in which luxS transcription was under the control of the xylA promoter (NTHi 86-028NP luxS xylA::luxS), 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 luxS expression and biofilm dispersal. Measurement of luxS transcript levels by real-time reverse transcription-PCR (RT-PCR) showed that luxS expression peaked as biofilms matured and waned before dispersal. Transcript profiling revealed significant changes following the induction of luxS, including increased transcript levels for a predicted family 8 glycosyltransferase (NTHI1750; designated gstA); this result was confirmed by real-time RT-PCR. An isogenic NTHi 86-028NP gstA 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 NTHi 86-028NP gstA compared to the parental strain. Therefore, we conclude that AI-2 promotes NTHi 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.

Suppression of Alternative Lipooligosaccharide Glycosyltransferase Activity by UDP-Galactose Epimerase Enhances Murine Lung Infection and Evasion of Serum IgM

“…Because mutants lacking galE produce enhanced biofilm, it is possible that reduced UDP-Gal production by GalE may occur in biofilms. While sialic acid and at least one glycosyltransferase have been implicated in biofilm production (Pang et al, 2018), the exact composition of the carbohydrates in the matrix is not known. Nevertheless, cell surface poly- N -acetylglucosamine (PNAG), is a major polysaccharide component of biofilm matrix in other bacteria (Roux et al, 2015), and the precursor for PNAG, UDP-GlcNAc, has been proposed as a precursor of biofilm matrix material in NTHi (Greiner et al, 2004).…”

Quorum Sensing as Antivirulence Target in Cystic Fibrosis Pathogens

“…P. aeruginosa is a member of the large group of the ESKAPE pathogens ( Enterococcus faecium , Staphylococcus aureus , Klebsiella pneumonia , Acinetobacter baumannii , Pseudomonas aeruginosa , and Enterobacter species) and it could be considered a “superbug” due to its pathogenesis and transmission. The extensive use of antibiotics increases the development of multidrug-resistant P. aeruginosa strains that leads to the failure of the therapies against this bacterium [98]. In this scenario, the identification of new and alternative strategies for prevention and treatment of infection is essential.…”

Interference With Quorum-Sensing Signal Biosynthesis as a Promising Therapeutic Strategy Against Multidrug-Resistant Pathogens

“…However, through which mechanisms luxS influences biofilm formation is under debate. LuxS could influence biofilm formation in an AI-2-dependent fashion, in which the expression of genes associated with bacterial adherence and biofilm matrix production may be modulated through AI-2-mediated signaling (Hardie and Heurlier, 2008; Duanis-Assaf et al, 2016; Ma R. et al, 2017; Velusamy et al, 2017; Pang et al, 2018). In addition, AI-2 may promote single and mixed species biofilm formation through chemotaxis-mediated aggregation events (Laganenka et al, 2016; Laganenka and Sourjik, 2017).…”