title: Amyloid adhesins are abundant in natural biofilms.
abstract: Surface-associated amyloid fibrils have been described by bacteria in the family Enterbacteriaceae, but it is unknown to what extent amyloid adhesins are present in natural biofilms. In this study, amyloid adhesins were specifically stained with Thioflavin T and two conformationally specific antibodies targeting amyloid fibrils. These three independent detection methods were each combined with fluorescence in situ hybridization using fluorescently labelled oligonucleotide probes in order to link phenotype with identity. Escherichia coli mutants with and without amyloid adhesins (curli) served as controls. In biofilms from four different natural habitats, bacteria producing extracellular amyloid adhesins were identified within several phyla: Proteobacteria (Alpha-, Beta-, Gamma- and Deltaproteobacteria), Bacteriodetes, Chloroflexi and Actinobacteria, and most likely also in other phyla. Quantification of the microorganisms producing amyloid adhesins showed that they constituted at least 5-40% of all prokaryotes present in the biofilms, depending on the habitat. Particularly in drinking water biofilms, a high number of amyloid-positive bacteria were identified. Production of amyloids was confirmed by environmental isolates belonging to the Gammaproteobacteria, Bacteriodetes, Firmicutes and Actinobacteria. The new approach is a very useful tool for further culture-independent studies in mixed microbial communities, where the abundance and diversity of bacteria expressing amyloid adhesins seems much greater than hitherto anticipated.
authors.affiliation: Department of Biotechnology, Aalborg University, Sohngaardsholmvej 57, DK-9000, Aalborg, Denmark.
authors.forename: Poul
authors.initials: P
authors.lastname: Larsen
authors.forename: Jeppe Lund
authors.initials: JL
authors.lastname: Nielsen
authors.forename: Morten Simonsen
authors.initials: MS
authors.lastname: Dueholm
authors.forename: Ronald
authors.initials: R
authors.lastname: Wetzel
authors.forename: Daniel
authors.initials: D
authors.lastname: Otzen
authors.forename: Per Halkjaer
authors.initials: PH
authors.lastname: Nielsen
mesh_terms: D039903:Actinobacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000378:metabolism*; D000682:Amyloid / Q000378:metabolism*; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D052160:Benzothiazoles; D018441:Biofilms / Q000254:growth & development*; D004269:DNA, Bacterial / Q000032:analysis; D005456:Fluorescent Dyes / Q000378:metabolism; D008969:Molecular Sequence Data; D020560:Proteobacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012336:RNA, Ribosomal, 16S; D012623:Seawater / Q000382:microbiology; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000382:microbiology; D013844:Thiazoles / Q000378:metabolism; D014881:Water Supply
chemical_list: D018829:Adhesins, Bacterial; D000682:Amyloid; D052160:Benzothiazoles; D004269:DNA, Bacterial; D005456:Fluorescent Dyes; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D013844:Thiazoles; C009462:thioflavin T