Surface-layer protein is a public-good matrix exopolymer for microbial community organisation in environmental anammox biofilms

Lan Li Wong, Yang Lu, James Chin Shing Ho, Sudarsan Mugunthan, Yingyu Law, Patricia Conway, Staffan Kjelleberg*, Thomas Seviour*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


Extracellular polymeric substances (EPS) are core biofilm components, yet how they mediate interactions within and contribute to the structuring of biofilms is largely unknown, particularly for non-culturable microbial communities that predominate in environmental habitats. To address this knowledge gap, we explored the role of EPS in an anaerobic ammonium oxidation (anammox) biofilm. An extracellular glycoprotein, BROSI_A1236, from an anammox bacterium, formed envelopes around the anammox cells, supporting its identification as a surface (S-) layer protein. However, the S-layer protein also appeared at the edge of the biofilm, in close proximity to the polysaccharide-coated filamentous Chloroflexi bacteria but distal to the anammox bacterial cells. The Chloroflexi bacteria assembled into a cross-linked network at the edge of the granules and surrounding anammox cell clusters, with the S-layer protein occupying the space around the Chloroflexi. The anammox S-layer protein was also abundant at junctions between Chloroflexi cells. Thus, the S-layer protein is likely transported through the matrix as an EPS and also acts as an adhesive to facilitate the assembly of filamentous Chloroflexi into a three-dimensional biofilm lattice. The spatial distribution of the S-layer protein within the mixed species biofilm suggests that it is a “public-good” EPS, which facilitates the assembly of other bacteria into a framework for the benefit of the biofilm community, and enables key syntrophic relationships, including anammox. [Figure not available: see fulltext.].

Original languageEnglish
JournalISME Journal
Pages (from-to)803–812
Number of pages10
Publication statusPublished - Jun 2023


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