Aeromonas salmonicida Growth in Response to Atlantic Salmon Mucins Differs between Epithelial Sites, Is Governed by Sialylated and-Acetylhexosamine-Containing-Glycans, and Is Affected by Ca.

Abstract

causes furunculosis in salmonids and is a threat to Atlantic salmon aquaculture. The epithelial surfaces that the pathogen colonizes are covered by a mucus layer predominantly comprised of secreted mucins. By using mass spectrometry to identify mucin glycan structures with and without enzymatic removal of glycan residues, coupled to measurements of bacterial growth, we show here that the complex Atlantic salmon intestinal mucin glycans enhancegrowth, whereas the more simple skin mucin glycans do not. Of the glycan residues present terminally on the salmon mucins, only-acetylglucosamine (GlcNAc) enhances growth. Sialic acids, which have an abundance of 75% among terminal glycans from skin and of <50% among intestinal glycans, cannot be removed or used byfor growth-enhancing purposes, and they shield internal GlcNAc from utilization. A Caconcentration above 0.1 mM is needed forto be able to utilize mucins for growth-promoting purposes, and 10 mM further enhances bothgrowth in response to mucins and binding of the bacterium to mucins. In conclusion, GlcNAc and sialic acids are important determinants of theinteraction with its host at the mucosal surface. Furthermore, since the mucin glycan repertoire affects pathogen growth, the glycan repertoire may be a factor to take into account during breeding and selection of strains for aquaculture.