Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

Candidatus Dormibacteraeota, a trace gas scavenging phyla of soil bacteria. (#212)

Kate Montgomery 1 , Julian Zaugg 2 , Timothy Williams 1 , Phil Hugenholtz 2 , Belinda Ferrari 1
  1. Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
  2. Australian Centre for Ecogenomics, University of Queensland, Brisbane, Qld, Australia

Candidatus Dormibacteraeota, previously known as candidate division AD3, is a phylum of yet to be cultured soil bacteria that are found ubiquitously across the globe. Usually representing less than 1% of the microbial population, they have been detected in relatively high abundances (up to 15%) within Antarctic desert surface soils. This enigmatic phylum has also been reported to be present in high abundances in other cold environments, predominantly permafrost.  Recently, we used shotgun sequencing and differential coverage binning on metagenomes obtained from two arid desert sites, Robinson Ridge and Mitchell Peninsula, in Eastern Antarctica. Six microbial assembled genomes (MAGs) were retrieved that were > 90% complete and contained between 0-4.6% contamination. Analysis of all six MAGs showed that Dormibacteraeota is a distinct phylum, with four of the genomes matching the typestrain Dormibacter sp., while the others matched a group commonly referred to as JG37-AG-4. Genomic analysis revealed that all six of the genomes have the capacity for aerobic respiration of glycerol and xylose, while the JG37-AG-4 genomes were also capable of anaerobic respiration. All six MAGs also contained type 1h hydrogenases, indicating their capacity for scavenging atmospheric hydrogen. While four also contained one or more carbon monoxide dehydrogenase genes, suggesting the atmospheric CO oxidation potential. Three MAGs also contained a type 1E RuBisCO. This data indicates the phylum are metabolically diverse, being genetically capable of trace gas chemosynthesis. We next aimed to visualise the Dormibacteraeota. FISH probes were designed targeting the two main groups which were subsequently validated using Clone-FISH.  Isolation of cells from Antarctic soil showed that members of both groups within the Dormibacteraeota are cocci in shape, ranging from approximately 1 μm in length. We propose that the Dormibacteraeota are a phyla perfectly adapted to life in the cold and nutrient devoid environment of Antarctic soils.