Glycans in Pseudomonas aeruginosa

Introduction Pseudomonas aeruginosa is an opportunistic pathogen known to encode a neuraminidase, PaNA. It is known that some strains of P. aeruginosa glycosylate pilin and flagellin and that pseudaminic acid is a component of the cell wall. PaNA has been associated with biofilm formation and has also been characterized to have more activity against pseudaminic acid than sialic acid. An allelic knockout of PaNA resulted in strain PAO1Δ2794. This strain was shown to generate less organized biofilms and also to have a somewhat decreased virulence in mice, depending on the route of inoculation. However, when PAO1Δ2794 is grown in culture, there are marked differences between wild type PAO1 and the mutant. Namely, the PAO1Δ2794 strain is likely to vigorously produce a green‐blue pigment as well as a layer of foam under certain media conditions, while PAO1 does not. These changes are indicators that quorum‐sensing (QS) is active in this strain in a population density independent manner compared to wild type. These observations led to the question of why the absence of PaNA might lead to this apparent mis‐regulation of QS. The objective of the study was to explore the role of PaNA in P. aeruginosa . Methods P. aeruginosa strains PAO1 and PAO1Δ2794 were grown in LB media and harvested hourly for 12 hours. Bacteria were pelleted by centrifugation and lysed. Both lysates and culture supernatant were subjected to SDS‐PAGE and Lectin Blot analysis. Results There are distinctive bands in the lectin blot of lysates with Limax flavus lectin, which recognizes generic sialic acids, including pseudaminic acid. The presence of these bands indicate that some internal protein(s) are in fact glycosylated. Interestingly, over the course of the growth curve and corresponding to the time point that the PAO1Δ2794 culture began to visibly produce pigments, the strongest set of bands is lost in the blot of the Δ2794 lysates, but maintained in PAO1 lysates. Conclusion Proteins in lysates of P. aeruginosa are glycosylated and may contribute to the regulation of QS by an undetermined mechanism. Support or Funding Information Supported by R01HL107778 and T32HL076125‐11.