Infect Immun. 2016 Aug 1. pii: IAI.00277-16. [Epub ahead of print]

Neuraminidase A exposed galactose promotes Streptococcus pneumoniae biofilm formation during colonization.

Blanchette KA1, Shenoy AT2, Milner J 2nd3, Gilley RP1, McClure E4, Hinojosa CA1, Kumar N4, Daughtery SC4, Tallon LJ4,Ott S4, King SJ5, Ferreira DM6, Gordon SB6, Tettelin H4, Orihuela CJ7.

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Abstract

Streptococcus pneumoniae is an opportunistic pathogen that colonizes the nasopharynx. Herein we show that carbon availability is distinct between the nasopharynx and bloodstream of adult humans: glucose being absent in the nasopharynx whereas galactose being abundant. We demonstrate that pneumococcal neuraminidase A (NanA), which cleaves terminal sialic acid residues from host glycoproteins, exposed galactose on the surface of septal epithelial cells thereby increasing its availability during colonization. We observed that mutants of S. pneumoniae deficient in NanA and β-galactosidase A (BgaA) failed to form biofilms in vivo despite normal biofilm-forming abilities in vitro Subsequently, we observed that glucose, sucrose, and fructose were inhibitory for biofilm formation, whereas galactose, lactose and low concentrations of sialic acid were permissive. Together these findings suggested that the genes involved in biofilm formation were under some form of carbon catabolite repression (CCR), a regulatory network during which genes involved in the uptake and metabolism of less-preferred sugars are silenced during growth with preferred sugars. Supporting this notion, we observed that a mutant deficient in pyruvate oxidase, which converts pyruvate to acetyl-phosphate during non-CCR inducing growth conditions, was unable to form biofilms. Subsequent comparative RNA-seq analyses of planktonic- and biofilm-grown pneumococci showed that metabolic pathways involving the conversion of pyruvate to acetyl-phosphate and subsequently leading to fatty acid biosynthesis were consistently up-regulated during diverse biofilm growth conditions. We conclude carbon availability in the nasopharynx impacts pneumococcal biofilm formation in vivo Additionally, biofilm formation involves metabolic pathways not previously appreciated to play an important role.

Copyright © 2016, American Society for Microbiology. All Rights Reserved.

PMID: 27481242 DOI: 10.1128/IAI.00277-16

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