Biogas through Darwinibacteriales
- The newly named Darwinibacteriales are one of the most common taxonomic groups of microorganisms involved in anaerobic digestion (biogas production) .
- This was the conclusion reached by researchers* in the EU-funded MICRO4BIOGAS project, who analyzed 80 samples from 45 biogas plants across Europe as part of their strategy to study and improve the production of this renewable fuel.
- The discovery has been published in two articles on the pre-print repository bioRxiv and has yet to be peer reviewed.
Scientists* involved in the European MICRO4BIOGAS research project have discovered and characterized a new taxonomic order of bacteria specialized in organic matter decomposition that could hold the key to improving biogas production. The new order was named Darwinibacteriales. It is one of the most abundant orders in biogas plants, but has never been scientifically characterized before.
The discovery was made by researchers from Germany - including Brandenburg University of Technology Cottbus-Senftenberg (BTU) - Spain and the Netherlands. They took 80 samples of decomposing organic material from 45 industrial biogas plants in Germany, the Netherlands and Austria and studied their microbial composition using DNA sequencing. "Interestingly, members of the Darwinibacteriales were present in all 80 samples, despite the differences and distance between these annexes," explains Prof. Dr. Christian Abendroth of BTU Cottbus-Senftenberg.
The scientists* were looking for the key microbial players in a process called anaerobic digestion, which breaks down organic material and then converts it into energy-rich gas that is subsequently used as fuel. This process is considered a black box because the role and dynamics of most of the microorganisms involved are still unknown. Improving biogas production would be a game changer in Energy Economics, reducing dependence on fossil fuels and energy imports, but the lack of microbiology research has held the sector back.
"This is a fine example of something that was right under our noses, essential to biogas production, but has long eluded us," says Dr. Manuel Porcar, Micro4Biogas coordinator from Spain's University of Valencia and co-author of both studies. "Our work reveals the tip of a microbial iceberg that most likely holds the key to biogas production, but has never been characterized at the genomic level."
With this discovery, MICRO4BIOGAS consortium scientists* are able to create customized, super-efficient communities of biogas-producing microbes. Their goal is to make biogas plants more robust and less dependent on subsidies to operate economically, giving a boost to renewable energy worldwide.
One of the most comprehensive datasets on anaerobic microbiomes
The initial characterization of 80 digested sludges was carried out by Pascal Otto of TU Dresden, Jeroen Tideman of Bioclear Earth and Prof. Dr. Christian Abendroth of BTU Cottbus-Senftenberg. As part of the sampling, technical parameters were also recorded and a large number of process chemical parameters were analyzed. According to Prof. Abendroth, together with the subsequent sequencing, one of the most comprehensive data sets to characterize anaerobic microbiomes to date was created. The complete analysis of the data set has not yet been completed. However, as a first milestone, the characterization of the above-mentioned Darwinibacteriales can now already be pointed to.
An overlooked group of microbes
In order to understand the composition and diversity of the microbial communities in all samples taken, a taxonomic analysis was carried out in which a specific gene (the 16s rRNA gene) was sequenced for all samples. The scientists* then compared the results to reference databases to determine which species or taxa - groups of living things that can be described by common characteristics and distinguished from other groups - were present and their relative abundance.
MBA03 had been mentioned in other studies as a group of uncultured bacteria (those not grown in the lab), but no one had paid particular attention to it before. "It was usually discovered during analysis of microbiomes from anaerobic digestion by sequencing the 16s rRNA gene , " explains Adriel Latorre, Ph.D., director of genomics at Darwin Bioprospecting Excellence and corresponding author of one of the two studies.
To thoroughly explore this unknown group, 30 samples in which the presence of MBA03 had been confirmed were fully sequenced. "Surprisingly, however, when we analyzed the complete metagenomes of the 30 samples, we were unable to detect MBA03 in any of them. This revealed a technical limitation: the genome of this taxon was not available in the databases. From that moment, our goal was clear: we had to isolate and describe in detail the genome of MBA03," says Dr. Latorre.
Using the MICRO4BIOGAS dataset, phylogenetic and phylogenomic reconstructions confirmed that MBA03 represents a new order that is a taxonomic group above family, genus and species. The new order has now been named Darwinibacteriales.
The scientists* suggest that a particular family within this new order (i.e., the Darwinibacteriaceae family) acts in mutual cooperation with so-called methanogenic archaea - another type of microorganism involved in anaerobic digestion. According to the study, the bacteria produce metabolic compounds that methanogenic archaea use to produce methane gas. This is consistent with previous studies that analyzed a link between the abundance of MBA03 and biogas production. If confirmed, these bacteria are a promising target for developing strategies to increase and improve biogas production.
About the MICRO4BIOGAS project
Micro4Biogas is an EU-funded project (H2020, contract number 101000470) to develop customized microbial consortia to increase biogas production.
The project, which involves 15 institutions from six countries (including universities, companies and the local government of a Spanish city where a state-of-the-art biogas plant is being built), aims to increase the yield, speed, quality and reproducibility of biogas production and consolidate this renewable energy as an environmentally, politically and economically viable option.
Literature reference
- Roser Puchol-Royo, Javier Pascual, Asier Ortega-Legarreta, Pascal Otto, Jeroen Tideman, Sjoerd-Jan de Vries, Christian Abendroth, Kristie Tanner, Manuel Porcar, Adriel Latorre-Perez. 2023. "Unveiling the Ecology, Taxonomy and Metabolic Capabilities of MBA03, a Potential Key Player in Anaerobic Digestion."
bioRxiv doi: https://doi.org/10.1101/2023.09.08.556800 - Pascal Otto, Roser Puchol-Royo, Asier Ortega-Legarreta, Kristie Tanner, Jeroen Tideman, Sjoerd-Jan de Vries, Javier Pascual, Manuel Porcar, Adriel Latorre-Perez, Christian Abendroth. 2023. "Multivariate comparison of taxonomic, chemical and technical data of 80 large-scale anaerobic digester systems."
bioRxiv doi: https://doi.org/10.1101/2023.09.08.556802
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