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

Abstract

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.

Quest for Nitrous Oxide-reducing Bacteria Present in an Anammox Biofilm Fed with Nitrous Oxide

“…This spatial arrangement did not appear to change with or without the N 2 O supply, which is consistent with previous findings ( Wong et al , 2023 ). In addition, filamentous Chloroflexota has been suggested to function as a junction for biomass aggregates and degrade EPS secreted by anammox bacteria, which are responsible for decomposing EPS to SMP available to other heterotrophic bacteria ( Wong et al , 2023 ). Our Anaerolineae MAG (bin 60) was also well annotated with pathways (alpha-amylase and beta-glucosidase) involved in the degradation of polysaccharide chains ( Oshiki et al , 2022a ) ( Fig.…”

A comprehensive catalog encompassing 1376 species-level genomes reveals the core community and functional diversity of anammox microbiota

“…Although the number of core taxa (particularly strict core genera) was much smaller, these taxa exhibited the highest abundance within anammox microbiota. Our ndings also underlined the widespread distribution of speci c denitrifying bacteria except for several genera from the phylum Chloro exota [72]. Importantly, the coexistence of multiple anammox species is consistently observed in complex environments, such as in full-scale plants [19,26].…”

“…Previous studies have elucidated the crucial functions of the phylum Chloro exota (e.g., the core genera UBA12294 and OLB14) in anammox microbiota [71][72][73]. However, previous studies underestimated the signi cance of several core taxa associated with the phylum Proteobacteria [20,74].…”

Cross-Feeding between Filamentous Cyanobacteria and Symbiotic Bacteria Favors Rapid Photogranulation

“…After dehydration, the granules were embedded in an optimum cutting temperature compound overnight and sliced into 60 μm sections with a cryostat at −20 °C (Leica CM1950, Germany). The probes for hybridization included Alexa Fluor 488 (green)-labeled CFX1223 and GNSB941 for Chloroflexi, and THAU832 for Thauera . The distribution of FC and microalgae was observed by the spontaneous fluorescence of chlorophyll-a (red) as described previously .…”