Biology subjects

McDonald, I. R.

Publications and source records attributed to McDonald, I. R..

4 recordsLinked to original sources

bioRxiv2025

Antarctic Soil Auxiliarome: unraveling the pan-auxiliary metabolic genes catalogue in a transect across different ice-free regions of Antarctica

The Transantarctic Mountains host a significant portion of Antarcticas ice-free soils and support diverse microbial communities, but the role of viruses in these extreme ecosystems remains poorly understood. To address this gap, we conducted the first comprehensive analysis of both RNA and DNA soil viruses across ten locations along a regional-scale latitudinal transect. This study revealed high viral diversity, including the first description of 18 previously unreported viral families in Antarctic soils, alongside significant local viral endemicity. Elevation emerged as the primary driver of viral diversity, while distance to the coast explained the distribution of auxiliary metabolic genes (AMGs), and distance to the sea influenced the metabolic pathways associated with these AMGs. The concept of the "auxiliarome," a pan-AMG catalogue at the community level, underscores the critical role of AMGs in engineering host metabolism. These genes contribute to the metabolism of cofactors and vitamins, amino acids, carbohydrates, and sulfur, as well as ecologically significant traits such as bacterial restriction-modification systems or antibiotic production and resistance. This study expands our understanding of Antarctic soil viruses and highlights their ecological importance in shaping microbial communities and biogeochemical processes in extreme environments.

microbiology↗

bioRxiv2024

Antarctic geothermal soils exhibit an absence of regional habitat generalist microorganisms

Active geothermal systems are relatively rare in Antarctica and represent metaphorical islands ideal to study microbial dispersal. In this study, we tested the macroecological concept that high dispersal rates result in communities being dominated by either habitat generalists or specialists by investigating the microbial communities on four geographically separated geothermal sites on three Antarctic volcanoes (Mts. Erebus, Melbourne and Rittman). We found that the microbial communities at higher temperature (max 65{square}) sites (Tramway Ridge on Erebus and Rittmann) were unique from each other and were dominated by a variety of novel Archaea from class Nitrososphaeria, while lower temperature (max 50{square}) sites (Western Crater on Erebus and Melbourne) had characteristically mesophilic communities (Planctomycetes, Acidobacteriota, etc) that were highly similar. We found that 97% of the detected microbial taxa were regional habitat specialists, with no generalists, with community assembly driven by high dispersal rates and drift (25 and 30% of community assembly, respectively), not environmental selection. Our results indicate that for microbial communities experiencing high dispersal rates between isolated communities, habitat specialists may tend to out-compete habitat generalists.

microbiology↗

bioRxiv2024

Geothermal ecosystems on Mt. Erebus, Antarctica, support diverse and taxonomically novel biota

Mt. Erebus, Antarctica, is the southernmost active volcano in the world and harbors a diverse and geochemically unique array of geothermal ecosystems including Subglacial and Exposed features, surrounded by a vast desert of ice and snow. Previous studies, although limited in scope, have highlighted the unique and potentially endemic biota present on Mt. Erebus. In this study, we provide a systematic biodiversity study across all domains of life and all types of geothermal features present on Mt. Erebus. We present physicochemical and biological data from 39 Exposed samples and 9 Subglacial samples from Mt. Erebus. The taxonomic novelty of prokaryotes and fungi found supports past hypotheses of high endemism among the biota of Mt. Erebus; in particular, the large number of taxonomically divergent fungal sequences was surprising. We found that different site types had unique physicochemistry and biota; in particular, Exposed sites were significantly warmer than Subglacial sites (median: 40 vs 10 for Exposed and Subglacial, respectively) and tended to have greater abundances of photosynthetic organisms (Cyanobacteria and Chlorophyta). Subglacial sites were characterized by a greater abundance of prokaryotes from the phylum Actinobacteriota, correlated with the greater concentrations of Ca, Mg, and Sr present. Additionally, we found that Tramway Ridge differed from other Exposed sites as well as all Subglacial sites in physicochemistry (significantly greater conductivity, water content, total carbon, and total nitrogen levels) and biota (greater relative abundances of order Nitrososphaeria and phylum Bacteroidota). In this study, we provide a blueprint for future work aimed at better understanding the novel biota of Mt. Erebus.

microbiology↗

bioRxiv2018

Microbial biogeography of 1,000 geothermal springs in New Zealand

Geothermal springs are model ecosystems to systematically investigate microbial biogeography as they i) represent discrete, homogenous habitats; ii) are abundantly distributed across multiple geographical scales; iii) span broad geochemical gradients; and iv) have simple community structures with reduced metazoan interactions. Taking advantage of these traits, we undertook the largest known consolidated study of geothermal ecosystems (http://1000springs.org.nz) to determine factors that influence biogeographical patterns. Rigorously standardised methodologies were used to measure microbial communities, 46 physicochemical parameters, and metadata from 1,019 hotspring samples across New Zealand. pH was found to be the primary influence on diversity in springs < 70 {degrees}C with community similarity decreasing with geographic distance. Surprisingly, community composition was dominated by two genera (Venenivibrio and Acidithiobacillus) in both average relative abundance (11.2 and 11.1 %) and prevalence (74.2 and 62.9 % respectively) across physicochemical spectrums of 13.9 - 100.6 {degrees}C and pH < 1 - 9.7. This study provides an unprecedented insight into the ecological conditions that drive community assembly in geothermal springs, and can be used as a foundation to improve the characterisation of global microbial biogeographical processes.

microbiology↗