Size matters: Anaerobic granules exhibit distinct ecological and physico-chemical gradients across biofilm size

Year: 2025

Type: article

Abstract: Anaerobic biological decomposition of organic matter is ubiquitous in Nature wherever anaerobic environments prevail, and is catalysed by hydrolytic, fermentative, acetogenic, methanogenic, and various other groups. It is also harnessed in innovative ways in engineered systems that may rely on small (0.1-4.0 mm), spherical, anaerobic granules. These biofilms are crucial to the operational success of a range of widely applied engineered-ecosystems designed for wastewater treatment. The structure and function of granule microbiomes underpin their utility. Here, granules were separated into ten size fractions (proxies for age), hypothesizing that small granules are 'young' and larger ones are 'old'. Gradients were observed across size in terms of volatile solids, density, settleability, biofilm morphology, methanogenic activity, and profiles of extracellular polymeric substances, suggesting ongoing development of physico-chemical characteristics as granules develop. Short-read amplicon sequencing indicated a negative relationship between granule size and community diversity. Furthermore, as size increased, the methanogenic archaea dominated the microbiome. Small granules were found to harbour a sub-group of highly specific taxa, and the identification of generalists and specialists may point to substantial resilience of the microbiome. The findings of this study indicate opportunities for precision management of wastewater treatment systems. They suggest that size is an important indicator for aggregate utility - size may, indeed, determine many of the characteristics of both the individual-granule microbiomes and the overall function of a wastewater treatment system.

Source: Environmental Science and Ecotechnology

DOI: 10.1016/j.ese.2025.100561

Authors: Anna Trego, Cristina Morabito, Isabelle Bourven, Giles Guibaud, Vincent O'Flaherty, Gavin Collins, Umer Zeeshan Ijaz

Institutions: Ollscoil na Gaillimhe – University of Galway, Eau Environnement Limoges, Université de Limoges, University of Glasgow

Language: English

Topic: Anaerobic Digestion and Biogas Production

Subfield: Building and Construction

Field: Engineering

Domain: Physical Sciences

SDGs: Clean water and sanitation, Responsible consumption and production

Open Access status: gold

Estimated APC paid: $2,000

Funders: European Cooperation in Science and Technology, Enterprise Ireland, Higher Education Authority, Science Foundation Ireland, University of Galway, Università degli Studi di Torino, Engineering and Physical Sciences Research Council, Natural Environment Research Council, European Research Council, European Regional Development Fund

OpenAlex ID: W4408954974