Candidatus Dormibacterota, a phylum of trace-gas oxidizing bacteria from Antarctic soils
Candidatus Dormibacterota is a soil bacterial phylum identified in unusually high relative abundances within East Antarctic desert soil. Despite being widely distributed, albeit at low relative abundances (< 1%), within soils across the globe, Ca. Dormibacterota lacks a cultured representative. G...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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UNSW, Sydney
2021
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| Online Access: | http://hdl.handle.net/1959.4/100154 https://unsworks.unsw.edu.au/bitstreams/cb83a1b3-57ae-481e-8054-89c0b628facf/download https://doi.org/10.26190/unsworks/2064 |
| Summary: | Candidatus Dormibacterota is a soil bacterial phylum identified in unusually high relative abundances within East Antarctic desert soil. Despite being widely distributed, albeit at low relative abundances (< 1%), within soils across the globe, Ca. Dormibacterota lacks a cultured representative. Given its ‘unculturable’ status there is little functional information available on this enigmatic phylum. Metabolic reconstructions from metagenome-assembled genomes (MAGs) of Ca. Dormibacterota from East Antarctic deserts implicated members of Ca. Dormibacterota as potentially capable of a novel metabolic process called ‘atmospheric chemosynthesis’. During atmospheric chemosynthesis, H2, CO2 and CO from the atmosphere are oxidised by bacteria containing high-affinity enzymes as a source of energy and carbon. The proposed enzymes include Type 1h/5 hydrogenases, Type 1E RuBisCO and carbon monoxide dehydrogenases. Firstly, we established a protocol for the extraction of bacterial cells from cold and temperate soil samples. The optimised protocol resulted in improved cell yields and decreased carry-over of detritus from soil, which is known to hamper downstream microscopy and DNA extraction processes. This allowed for the successful isolation of microbial cells from Antarctic soil, for subsequent analysis via confocal microscopy using newly designed order-level fluorescence in situ hybridisation (FISH) probes (DORM1164-Cy3 and AEOL1170-Cy3). Cells were revealed to be small (312 nm-1.4 µm in diameter) and consistently coccoid in shape. Confocal microscopy showed that some members of Ca. Dormibacterota form interspecific aggregations with another bacterial species, indicating a potentially symbiotic relationship. Next, we produced six new high-quality MAGs and combined them with three publicly available MAGs to perform a phylogenetic analysis of Ca. Dormibacterota present in Antarctic soils. We found that Ca. Dormibacterota consists of a single class, Ca. Dormibacteria, that contains two order level divisions; Ca. ... |
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