Biology subjects

Dawson, R. A.

Publications and source records attributed to Dawson, R. A..

3 recordsLinked to original sources

bioRxiv2025

Distribution of carbon monoxide-oxidizing microorganisms along a chronosequence on Piton De La Fournaise volcano

Volcanic soils provide a unique environment for studying microbial colonization and succession due to their extreme conditions and distinct geochemical profiles. This study focused on carbon monoxide (CO)-oxidizing microbial communities in volcanic soils of varying ages at Piton De La Fournaise (Reunion island). Soil samples from three sites were analyzed to assess microbial community structure using 16S rRNA gene sequencing and metagenomic analysis to identify functional genes involved in CO oxidation. The activity of CO oxidizing microbes in soils was measured. Phylum-level analysis showed increasing Acidobacteriota and Chloroflexota, decreasing Actinomycetota and Bacteroidota, and stable Pseudomonadota, while class-level patterns included rising Alphaproteobacteria and Acidobacteriia, with Ktenobacteria emerging in the oldest soils. CO dehydrogenase-related genes were found in 17 metagenome-assembled genomes across all sites. CO-oxidizing microbes were present across soil ages, with detectable activity in the younger soils and greatest activity in the oldest, suggesting that these microbes actively use CO as an energy source even in soils with primary vegetation, contrary to general understanding. The findings highlight the intricate dynamics of microbial succession in volcanic soils and challenge conventional expectations about community complexity over time. Understanding pioneer communities elucidates soil restoration processes, which will become critical when countering anthropogenic soil degradation.

microbiology↗

bioRxiv2023

Carboxydovores from the Pseudomonadota colonise volcanic soils during succession

Carbon monoxide (CO) degrading microorganisms are present in volcanic deposits throughout succession, with vegetation and soil influencing the communities present. The carboxydovores are a subset of CO degraders that use CO only as an energy source, raising the question of how the physiological and metabolic features of the carboxydovores can make these bacteria more competitive in harsh volcanic ecosystems. An enrichment strategy was modified, which enabled the isolation of two carboxydovore representatives from genera that were abundant in the native soils, Cupriavidus sp. CV2T (92.3% ANI vs. Cupriavidus basilensis DSM 11853) and a putative strain of Paraburkholderia terrae (Pb. terrae COX) (96.42% ANI vs. Pb. terrae KU-64T). These isolates oxidise CO across a very broad range of concentrations, and genome sequence analysis indicated that they use form-I carbon monoxide dehydrogenase (CODH) to do so. Cupriavidus sp. CV2T and Pb. terrae COX each oxidised CO specifically at stationary phase, but the conditions for induction of CODH expression were distinct. Cupriavidus sp. CV2T expressed CODH only in the presence of CO, while Pb. terrae COX expressed CODH regardless of the presence of CO. Based on metabolic and phylogenetic analyses, Cupriavidus sp. CV2T is recommended as a novel species within the genus Cupriavidus. Therefore, we propose the name Cupriavidus ulmosensis sp. nov. for the type strain CV2T (= NCIMB 15506T, = CECT 30956T). This study provides valuable insights into the physiology and metabolism of carboxydovores, which colonise volcanic ecosystems during succession. ImportanceVolcanic ecosystems harbour many bacteria that contribute to the environmentally important process of carbon monoxide (CO) oxidation. We demonstrate a modified method for isolating bacteria, which consume CO at very low concentrations as a supplementary energy source (carboxydovory), leading to the isolation of two novel strains (Cupriavidus sp. CV2T and Paraburkholderia terrae COX) from volcanic strata that formed in 1917 and 2015, respectively. The conditions under which CO consumption occurs were investigated; each strain consumed CO during stationary phase, but Pb. terrae COX consumed CO regardless of the prior growth conditions while Cupriavidus sp. CV2 was more controlled. Cupriavidus sp. CV2 is a type strain of a new species, Cupriavidus ulmosensis str. CV2, which demonstrates relatively high tolerance for CO. These strains provide the basis for further study of the physiology, metabolism, and genetics of CO oxidation by carboxydovores, and will help us to understand how bacteria colonise harsh volcanic ecosystems.

microbiology↗

bioRxiv2023

Antimicrobial resistance in Arctic soils is mediated by competition and facilitation

Antimicrobial resistance (AMR) is widespread in terrestrial ecosystems. However, the natural processes shaping the spatial and temporal dissemination of AMR in soils are not well understood. We aimed to determine whether, how, and why AMR varies in recently deglaciated pioneer and developing Arctic soils. We showed that antibiotic-resistant genes (ARGs), mobile genetic elements (MGEs), and antibiotic-resistant bacteria (ARB) are abundant, exhibit a non-uniform distribution, and generally increase with soil age. Our analyses suggest a strong positive relationship between soil age and ARG and ARB, which we attribute to increased competition between microbes in older soils. We also observed a weak negative relationship between soil age and ARG diversity mediated by soil organic matter - suggesting facilitation due to the alleviation of nutrient limitation. The microbial processes regulating the spread of AMR in Arctic soils may be further susceptible to the effects of future climate change and human activities. TeaserThe spatial and temporal spread of antimicrobial resistance in Arctic soils is dependent on microbial interactions for nutrients

microbiology↗