Enrichment and description of novel bacteria performing syntrophic propionate oxidation at high ammonia level

Abstract

Inefficient syntrophic propionate degradation causes severe operating disturbances and reduces biogas productivity in many high-ammonia anaerobic digesters, but propionate-degrading microorganisms in these systems remain unknown. Here, we identified candidate ammonia-tolerant syntrophic propionateoxidising bacteria using propionate enrichment at high ammonia levels (0.7-0.8 g NH 3 L −1) in continuously-fed reactors. We reconstructed 30 highquality metagenome-assembled genomes (MAGs) from the propionate-fed reactors, which revealed two novel species from the families Peptococcaceae and Desulfobulbaceae as syntrophic propionate-oxidising candidates. Both MAGs possess genomic potential for the propionate oxidation and electron transfer required for syntrophic energy conservation and, similar to ammonia-tolerant acetate degrading syntrophs, both MAGs contain genes predicted to link to ammonia and pH tolerance. Based on relative abundance, a Peptococcaceae sp. appeared to be the main propionate degrader and has been given the provisional name "Candidatus Syntrophopropionicum ammon iitolerans". This bacterium was also found in highammonia biogas digesters, using quantitative PCR. Acetate was degraded by syntrophic acetateoxidising bacteria and the hydrogenotrophic methanogenic community consisted of Methanocul leus bourgensis and a yet to be characterised Methanoculleus sp. This work provides knowledge of cooperating syntrophic species in high-ammonia systems and reveals that ammonia-tolerant syntrophic propionate-degrading populations share common features, but diverge genomically and taxonomically from known species.

Microbiological Surveillance of Biogas Plants: Targeting Acetogenic Community

“…This OTU, also found in C3-K1/2 and in the stable phase in C5-A1/3, were 84-92% similar to Peptococcaceae bacterium 1109, previously proposed to be a syntrophic organic acid-oxidising bacterium (Town et al, 2014;Town and Dumonceaux, 2016;Buettner et al, 2019;Wirth et al, 2019;Singh et al, 2021a). The OTU could also be related to the recently discovered and uncultured syntrophic propionate oxidising bacteria Candidatus Syntrophopropionicum ammoniitolerans isolated from propionate oxidising enrichments (Singh et al, 2021b). As this OTU was observed during the high levels of VFA (3-17 g/L) including propionate (2-10 g/L), its involvement in propionate degradation is further supported.…”

“…Further, the results from this study indicates that the applied method is able to target not only the potential acetogenic community but also syntrophic organic-acid oxidising bacterial communities viz. syntrophic acetate-oxidising bacteria (SAOB; phylum Cloacimonetes, Tepidanaerobacter, Peptococcaceae bacterium 1109; Sekiguchi et al, 2006;Westerholm et al, 2011b;Town et al, 2014;Town and Dumonceaux, 2016;Buettner et al, 2019;Wirth et al, 2019), syntrophic-propionate oxidising bacteria (phylum Cloacimonetes, family Peptococcaceae; Pelletier et al, 2008;Dyksma and Gallert, 2019;Singh et al, 2021b), syntrophic fatty-acid degraders (Syntrophomonas, Syntrophothermus; Sekiguchi et al, 2000;Zhang et al, 2004;Sousa et al, 2007) and syntrophic benzene degrading bacteria (family Peptococcaceae; van der Zaan et al, 2012;Gieg et al, 2014;Zhuang et al, 2015). Syntrophic organic-acid oxidising bacteria play a key role in the biogas process and even though not all being acetogens they can be detected due to the presence of FTHFS gene (Singh et al, 2019;Singh, 2021).…”

Syntrophic Acetate-Oxidizing Microbial Consortia Enriched from Full-Scale Mesophilic Food Waste Anaerobic Digesters Showing High Biodiversity and Functional Redundancy

“…Continuous feeding with volatile fatty acids (VFAs) is known to enrich syntrophic VFA-oxidizing bacteria ( 19 , 26 ). The combination of this enrichment process with high-throughput metagenomic sequencing makes it possible to acquire high-quality draft genomes of some novel syntrophic members with low abundance in full-scale digesters ( 27 ).…”

Effect of magnetite addition on transcriptional profiles of syntrophic Bacteria and Archaea during anaerobic digestion of propionate in wastewater sludge

“…Propionivorax syntrophicum (Hao et al ., 2020), Ca . Syntrophopropionicum ammoniitolerans (Singh et al ., 2021) and uncultured Cryptanaerobacter (Ahlert et al ., 2016; Wang et al ., 2019) were proposed as propionate oxidizers that are phylogenetically closely related to Pelotomaculum spp. Members of the candidate phylum Cloacimonadota such as Ca .…”