ORCID Profile
0000-0001-8059-861X
Current Organisation
University of Pretoria
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Microbial Ecology | Other Biological Sciences | Soil Biology | Microbiology | Environmental Management | Climate Change Processes | Global Change Biology
ANZSRC Socio-Economic Objective (SEO)
Antarctic and Sub-Antarctic Flora, Fauna and Biodiversity | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Ecosystem Assessment and Management of Antarctic and Sub-Antarctic Environments | Environmental Policy, Legislation and Standards not elsewhere classified | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Biotic interactions are an unexpected yet critical control on the complexity of an abiotically driven polar ecosystem
Publisher: Springer Science and Business Media LLC
Date: 15-02-2019
DOI: 10.1038/S42003-018-0274-5
Abstract: Abiotic and biotic factors control ecosystem bio ersity, but their relative contributions remain unclear. The ultraoligotrophic ecosystem of the Antarctic Dry Valleys, a simple yet highly heterogeneous ecosystem, is a natural laboratory well-suited for resolving the abiotic and biotic controls of community structure. We undertook a multidisciplinary investigation to capture ecologically relevant biotic and abiotic attributes of more than 500 sites in the Dry Valleys, encompassing observed landscape heterogeneities across more than 200 km 2 . Using richness of autotrophic and heterotrophic taxa as a proxy for functional complexity, we linked measured variables in a parsimonious yet comprehensive structural equation model that explained significant variations in biological complexity and identified landscape-scale and fine-scale abiotic factors as the primary drivers of ersity. However, the inclusion of linkages among functional groups was essential for constructing the best-fitting model. Our findings support the notion that biotic interactions make crucial contributions even in an extremely simple ecosystem.
Antarctic microbial communities are functionally redundant, adapted and resistant to short term temperature perturbations
Publisher: Elsevier BV
Date: 12-2016
Meeting Report: 1st International Functional Metagenomics Workshop May 7–8, 2012, St. Jacobs, Ontario, Canada.
Publisher: Springer Science and Business Media LLC
Date: 15-04-2013
DOI: 10.4056/SIGS.3406845
Multiple energy sources and metabolic strategies sustain microbial diversity in Antarctic desert soils
Publisher: Proceedings of the National Academy of Sciences
Date: 03-11-2021
Abstract: Diverse microbial life has been detected in the cold desert soils of Antarctica once thought to be barren. Here, we provide metagenomic, biogeochemical, and culture-based evidence that Antarctic soil microorganisms are phylogenetically and functionally distinct from those in other soils and adopt various metabolic and ecological strategies. The most abundant community members are metabolically versatile aerobes that use ubiquitous atmospheric trace gases to potentially meet energy, carbon, and, through metabolic water production, hydration needs. Lineages capable of harvesting solar energy, oxidizing edaphic inorganic substrates, or adopting symbiotic lifestyles were also identified. Altogether, these findings provide insights into microbial adaptation to extreme water and energy limitation and will inform ongoing efforts to conserve the unique bio ersity on this continent.
Hypolithic Microbial Community of Quartz Pavement in the High-Altitude Tundra of Central Tibet
Publisher: Springer Science and Business Media LLC
Date: 25-03-2010
Challenges to the future conservation of the Antarctic
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-07-2012
Abstract: Changing environments and resource demands present challenges to Antarctic conservation.
Atmospheric chemosynthesis is phylogenetically and geographically widespread and contributes significantly to carbon fixation throughout cold deserts
Publisher: Springer Science and Business Media LLC
Date: 06-08-2022
DOI: 10.1038/S41396-022-01298-5
Abstract: Cold desert soil microbiomes thrive despite severe moisture and nutrient limitations. In Eastern Antarctic soils, bacterial primary production is supported by trace gas oxidation and the light-independent RuBisCO form IE. This study aims to determine if atmospheric chemosynthesis is widespread within Antarctic, Arctic and Tibetan cold deserts, to identify the breadth of trace gas chemosynthetic taxa and to further characterize the genetic determinants of this process. H 2 oxidation was ubiquitous, far exceeding rates reported to fulfill the maintenance needs of similarly structured edaphic microbiomes. Atmospheric chemosynthesis occurred globally, contributing significantly ( p 0.05) to carbon fixation in Antarctica and the high Arctic. Taxonomic and functional analyses were performed upon 18 cold desert metagenomes, 230 dereplicated medium-to-high-quality derived metagenome-assembled genomes (MAGs) and an additional 24,080 publicly available genomes. Hydrogenotrophic and carboxydotrophic growth markers were widespread. RuBisCO IE was discovered to co-occur alongside trace gas oxidation enzymes in representative Chloroflexota , Firmicutes , Deinococcota and Verrucomicrobiota genomes. We identify a novel group of high-affinity [NiFe]-hydrogenases, group 1m, through phylogenetics, gene structure analysis and homology modeling, and reveal substantial genetic ersity within RuBisCO form IE ( rbcL1E ), and high-affinity 1h and 1l [NiFe]-hydrogenase groups. We conclude that atmospheric chemosynthesis is a globally-distributed phenomenon, extending throughout cold deserts, with significant implications for the global carbon cycle and bacterial survival within environmental reservoirs.
Effect of nitrate and nitrite on the selection of microorganisms in the denitrifying anaerobic methane oxidation process
Publisher: Wiley
Date: 16-12-2011
DOI: 10.1111/J.1758-2229.2010.00227.X
Abstract: Two cultures were inoculated with sludges taken from a parent culture containing archaea distantly related to anaerobic methanotrophic archaea (ANME) and bacteria related to Candidatus Methylomirabilis oxyfera, both of which have previously been found in cultures performing denitrifying anaerobic methane oxidation process. The cultures were fed with nitrate and nitrite, respectively, along with methane. The nitrate-fed culture, Culture B, showed a stable microbial community composition and denitrifying anaerobic methane oxidation activity. In contrast, the nitrite-fed culture, Culture A, achieved a substantial increase in the nitrite consumption rate, from 1.1 to 7.3 mmol NO2 (-) -N (g VSS)(-1) day(-1) in 90 days. Concurrent with this activity increase, the archaeal population in Culture A decreased with time, and became undetectable after 100 days, while bacteria related to M. oxyfera increasingly dominated the culture. This observation suggests that the bacteria related to M. oxyfera are more competitive for nitrite reduction compared with the archaea related to ANME. This study showed that nitrate or nitrite feeding has a significant impact on the ecology and activities of microorganisms in the denitrifying anaerobic methane oxidation process. This study also revealed that nitrite overloading may have a toxic effect on the bacteria related to M. oxyfera.
Genetic diversity among populations of Antarctic springtails (Collembola) within the Mackay Glacier ecotone
Publisher: Canadian Science Publishing
Date: 09-2016
Abstract: Climate changes are likely to have major influences on the distribution and abundance of Antarctic terrestrial biota. To assess arthropod distribution and ersity within the Ross Sea region, we examined mitochondrial DNA (COI) sequences for three currently recognized species of springtail (Collembola) collected from sites in the vicinity, and to the north of, the Mackay Glacier (77°S). This area acts as a transition between two biogeographic regions (northern and southern Victoria Land). We found populations of highly ergent in iduals (5%–11.3% intraspecific sequence ergence) for each of the three putative springtail species, suggesting the possibility of cryptic ersity. Based on molecular clock estimates, these ergent lineages are likely to have been isolated for 3–5 million years. It was during this time that the Western Antarctic Ice Sheet (WAIS) was likely to have completely collapsed, potentially facilitating springtail dispersal via rafting on running waters and open seaways. The reformation of the WAIS would have isolated newly established populations, with subsequent dispersal restricted by glaciers and ice-covered areas. Given the currently limited distributions for these genetically ergent populations, any future changes in species’ distributions can be easily tracked through the DNA barcoding of springtails from within the Mackay Glacier ecotone.
South African research in the Southern Ocean: New opportunities but serious challenges
Publisher: Academy of Science of South Africa
Date: 26-03-2013
Abstract: South Africa has a long track record in Southern Ocean and Antarctic research and has recently invested considerable funds in acquiring new infrastructure for ongoing support of this research. This infrastructure includes a new base at Marion Island and a purpose-built ice capable research vessel, which greatly expand research opportunities. Despite this investment, South Africa’s standing as a participant in this critical field is threatened by confusion, lack of funding, lack of consultation and lack of transparency. The research endeavour is presently bedevilled by political manoeuvring among groups with ergent interests that too often have little to do with science, while past and present contributors of research are excluded from discussions that aim to formulate research strategy. This state of affairs is detrimental to the country’s aims of developing a leadership role in climate change and Antarctic research and squanders both financial and human capital.
Threat management priorities for conserving Antarctic biodiversity
Publisher: Public Library of Science (PLoS)
Date: 22-12-2022
DOI: 10.1371/JOURNAL.PBIO.3001921
Abstract: Antarctic terrestrial bio ersity faces multiple threats, from invasive species to climate change. Yet no large-scale assessments of threat management strategies exist. Applying a structured participatory approach, we demonstrate that existing conservation efforts are insufficient in a changing world, estimating that 65% (at best 37%, at worst 97%) of native terrestrial taxa and land-associated seabirds are likely to decline by 2100 under current trajectories. Emperor penguins are identified as the most vulnerable taxon, followed by other seabirds and dry soil nematodes. We find that implementing 10 key threat management strategies in parallel, at an estimated present-day equivalent annual cost of US$23 million, could benefit up to 84% of Antarctic taxa. Climate change is identified as the most pervasive threat to Antarctic bio ersity and influencing global policy to effectively limit climate change is the most beneficial conservation strategy. However, minimising impacts of human activities and improved planning and management of new infrastructure projects are cost-effective and will help to minimise regional threats. Simultaneous global and regional efforts are critical to secure Antarctic bio ersity for future generations.
Ancient landscapes of the Namib Desert harbor high levels of genetic variability and deeply divergent lineages for Collembola
Publisher: Wiley
Date: 04-2019
DOI: 10.1002/ECE3.5103
Biodegradation of high-concentration isopropanol by a solvent-tolerant thermophile, Bacillus pallidus
Publisher: Springer Science and Business Media LLC
Date: 26-03-2002
DOI: 10.1007/S00792-001-0260-5
Abstract: The aerobic biodegradation of high-concentration, to 24 g l(-1), 2-propanol (IPA) by a thermophilic isolate ST3, identified as Bacillus pallidus, was successfully carried out for the first time. This solvent-tolerant B. pallidus utilized IPA as the sole carbon source within a minimal salts medium. Cultivation was carried out in 100-ml shake flasks at 60 degrees C and compared with cultivation within a 1-l stirred tank reactor (STR). Specific growth rate (micro) was about 0.2 h(-1) for both systems, with a maximum cell density of 2.4 x 10(8) cells ml(-1) obtained with STR cultivation. During exponential growth and stationary phase, IPA biodegradation rates were found to be 0.14 and 0.02 g l(-1) h(-1), respectively, in shake-flask experiments, whereas corresponding values of 0.09 and 0.018 g l(-1) h(-1) were achievable in the STR. Generation of acetone, the major intermediate in aerobic IPA biodegradation, was also monitored as an indicator of microbial IPA utilization. Acetone levels reached a maximum of 2.2-2.3 g l(-1) after 72 and 58 h for 100-ml and 1-l systems, respectively. Both IPA and acetone were completely removed from the medium following 160 and 175 h, respectively, during STR growth, although this was not demonstrated within shake-flask reactions. Growth of B. pallidus on acetone or IPA alone demonstrated that the maximum growth rate ( micro ) obtainable was 0.247 h(-1) at 4 g l(-1) acetone and 0.202 h(-1) at 8 g l(-1) IPA within shake-flask cultivation. These results indicate the potential of the solvent-tolerant thermophile B. pallidus ST3 in the bioremediation of hot solvent-containing industrial waste streams.
Polar soils exhibit distinct patterns in microbial diversity and dominant phylotypes
Publisher: Elsevier BV
Date: 03-2022
Genetic diversity of soil invertebrates corroborates timing estimates for past collapses of the West Antarctic Ice Sheet
Publisher: Proceedings of the National Academy of Sciences
Date: 24-08-2020
Abstract: Changes in the extent of ice sheets through evolutionary timescales have influenced the connectivity of soil invertebrate populations across the Antarctic landscape. We use genetic ergences to estimate isolation times for soil invertebrates along the Transantarctic Mountains. Four species of Collembola (Arthropoda) each showed genetically distinct populations at locations likely isolated for millions of years. Two further species were less genetically erse although also range restricted. Our genetic data corroborate climate reconstructions and estimates of past warm periods of reduced ice and absent ice shelf in the Ross Sea region, during which time open seaways would have facilitated dispersal of Collembola, and possibly other taxa.
Non-indigenous microorganisms in the Antarctic: Assessing the risks
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.TIM.2011.07.008
Abstract: The Antarctic continent is frequently cited as the last pristine continent on Earth. However, this view is misleading for several reasons. First, there has been a rapid increase in visitors to Antarctica, with large increases at research bases and their environs and to sites of major tourist interest (e.g. historical sites and concentrations of megafauna). Second, although substantial efforts are made to avoid physical disturbance and contamination by chemical, human and other wastes at these sites, little has been done to prevent the introduction of non-indigenous microorganisms. Here, we analyse the extent and significance of anthropogenic introduction of microbial 'contaminants' to the Antarctic continent. We conclude that such processes are unlikely to have any immediate gross impact on microbiological community structure or function, but that increased efforts are required to protect the unique ecosystems of Antarctica from microbial and genetic contamination and homogenisation.
Endolithic Microbial Colonization of Limestone in a High-altitude Arid Environment
Publisher: Springer Science and Business Media LLC
Date: 25-11-2009
DOI: 10.1007/S00248-009-9607-8
Abstract: The morphology of endolithic colonization in a limestone escarpment and surrounding rocky debris (termed float) at a high-altitude arid site in central Tibet was documented using scanning electron microscopy. Putative lichenized structures and extensive coccoid bacterial colonization were observed. Absolute and relative abundance of rRNA gene signatures using real-time quantitative polymerase chain reaction and phylogenetic analysis of environmental phylotypes were used to characterize community structure across all domains. Escarpment endoliths were dominated by eukaryotic phylotypes suggestive of lichenised associations (a Trebouxia lichen phycobiont and Leptodontidium lichen mycobiont), whereas float endoliths were dominated by bacterial phylotypes, including the cyanobacterium Chroococcidiopsis plus several unidentified beta proteobacteria and crenarchaea. Among a range of abiotic variables tested, ultraviolet (UV) transmittance by rock substrates was the factor best able to explain differences in community structure, with eukaryotic lichen phylotypes more abundant under conditions of greater UV-exposure compared to prokaryotes. Variously pigmented float rocks did not support significantly different communities. Estimates of in situ carbon fixation based upon (14)C radio-labelled bicarbonate uptake indicated endolithic productivity of approximately 2.01 g C/m(2)/year(-1), intermediate between estimates for Antarctic and temperate communities.
The Functional Potential of the Rhizospheric Microbiome of an Invasive Tree Species, Acacia dealbata
Publisher: Springer Science and Business Media LLC
Date: 09-06-2018
DOI: 10.1007/S00248-018-1214-0
Abstract: Plant-microbe interactions mediate both the invasiveness of introduced plant species and the impacts that they have in invaded ecosystems. Although the phylogenetic composition of the rhizospheric microbiome of Acacia dealbata (an invasive Australian tree species) has been investigated, little is known about the functional potential of the constituents of these altered microbial communities. We used shotgun DNA sequencing to better understand the link between bacterial community composition and functional capacity in the rhizospheric microbiomes associated with invasive A. dealbata populations in South Africa. Our analysis showed that several genes associated with plant growth-promoting (PGP) traits were significantly overrepresented in the rhizospheric metagenomes compared to neighbouring bulk soils collected away from A. dealbata stands. The majority of these genes are involved in the metabolism of nitrogen, carbohydrates and vitamins, and in various membrane transport systems. Overrepresented genes were linked to a limited number of bacterial taxa, mostly Bradyrhizobium species, the preferred N-fixing rhizobial symbiont of Australian acacias. Overall, these findings suggest that A. dealbata enriches rhizosphere soils with potentially beneficial microbial taxa, and that members of the genus Bradyrhizobium may play an integral role in mediating PGP processes that may influence the success of this invader when colonizing novel environments.
Related Organisations
University Of The Western Cape Faculty Of Natural Science
Location: South Africa
Related Funding Activities
Discovery Projects - Grant ID: DP220103430
Start Date: 2022
End Date: 12-2024
Amount: $490,649.00
Funder: Australian Research Council
View Funded ActivitySpecial Research Initiatives - Grant ID: SR200100005
Start Date: 06-2021
End Date: 06-2030
Amount: $36,000,000.00
Funder: Australian Research Council
View Funded Activity