Glycosylated amyloid-like proteins in the structural extracellular polymers of aerobic granular sludge enriched with ammonium-oxidizing bacteria

Yuemei Lin, Clara Reino, Julián Carrera, Julio Pérez, Mark C.M. van Loosdrecht

Research output: Contribution to journalArticleResearch

19 Citations (Scopus)

Abstract

© 2018 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd. A new type of structural extracellular polymers (EPS) was extracted from aerobic granular sludge dominated by ammonium-oxidizing bacteria. It was analyzed by Raman and FTIR spectroscopy to characterize specific amino acids and protein secondary structure, and by SDS-PAGE with different stains to identify different glycoconjugates. Its intrinsic fluorescence was captured to visualize the location of the extracted EPS in the nitrifying granules, and its hydrogel-forming property was studied by rheometry. The extracted EPS is abundant with cross ß-sheet secondary structure, contains glycosylated proteins/polypeptides, and rich in tryptophan. It forms hydrogel with high mechanical strength. The extraction and discovery of glycosylated proteins and/or amyloids further shows that conventionally used extraction and characterization techniques are not adequate for the study of structural extracellular polymers in biofilms and/or granular sludge. Confirming amyloids secondary structure in such a complex sample is challengeable due to the possibility of amyloids glycosylation and self-assembly. A new definition of extracellular polymers components which includes glycosylated proteins and a better approach to studying them is required to stimulate biofilm research.
Original languageEnglish
Article numbere00616
JournalMicrobiologyOpen
Volume7
DOIs
Publication statusPublished - 1 Dec 2018

Keywords

  • aerobic granular sludge
  • ammonium-oxidizing bacteria
  • amyloid
  • extracellular polymeric substances
  • glycoproteins

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