ORCID Profile
0000-0002-2703-0694
Current Organisation
Institute for Biology III, Faculty of Biology, University of Freiburg, Germany
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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)
Biological Oceanography | Microbial Ecology | Ecological Impacts of Climate Change | Ecology | Chemical Oceanography | Microbiology | Ecological Physiology
ANZSRC Socio-Economic Objective (SEO)
Marine Oceanic Processes (excl. climate related) | Expanding Knowledge in the Environmental Sciences | Ecosystem Adaptation to Climate Change | Marine Flora, Fauna and Biodiversity | Climate and Climate Change not elsewhere classified |
Related Links
Publications
Chemotaxis by natural populations of coral reef bacteria
Publisher: Springer Science and Business Media LLC
Date: 23-01-2015
A comparative analysis of photosynthetic recovery from thermal stress: a desert plant case study
Publisher: Springer Science and Business Media LLC
Date: 24-06-2014
DOI: 10.1007/S00442-014-2988-5
Abstract: Our understanding of the effects of heat stress on plant photosynthesis has progressed rapidly in recent years through the use of chlorophyll a fluorescence techniques. These methods frequently involve the treatment of leaves for several hours in dark conditions to estimate declines in maximum quantum yield of photsystem II (F(V)/F(M)), rarely accounting for the recovery of effective quantum yield (ΔF/F(M')) after thermally induced damage occurs. Exposure to high temperature extremes, however, can occur over minutes, rather than hours, and recent studies suggest that light influences damage recovery. Also, the current focus on agriculturally important crops may lead to assumptions about average stress responses and a poor understanding about the variation among species' thermal tolerance. We present a chlorophyll a fluorescence protocol incorporating subsaturating light to address whether species' thermal tolerance thresholds (T 50) are related to the ability to recover from short-term heat stress in 41 Australian desert species. We found that damage incurred by 15-min thermal stress events was most strongly negatively correlated with the capacity of species to recover after a stress event of 50 °C in summer. Phylogenetically independent contrast analyses revealed that basal ergences partially explain this relationship. Although T 50 and recovery capacity were positively correlated, the relationship was weaker for species with high T 50 values (>51 °C). Results highlight that, even within a single desert biome, species vary widely in their physiological response to high temperature stress and recovery metrics provide more comprehensive information than damage metrics alone.
Characterisation of coral explants: a model organism for cnidarian–dinoflagellate studies
Publisher: Springer Science and Business Media LLC
Date: 21-11-2014
Thrill and adventure seeking in risky driving at work: The moderating role of safety climate
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.JSR.2017.08.007
Abstract: Introduction Within many industrialized countries, the leading cause of worker fatalities and serious injuries can be attributed to road trauma. In non-occupational research, high levels of sensation seeking personality, and specifically thrill and adventure seeking, have been associated with risky driving behaviors. In work driving literature, high organizational safety climate has been associated with reduced risky driving in work drivers. However, the extent that factors such as safety climate and thrill seeking interact in regard to work driving safety remains unclear, and the current research examined this interaction. Methods A total of 1,011 work drivers from four organizations participated in the research. Surveys were distributed online and hardcopies were sent via mail. The survey included measures of thrill and adventure seeking, safety climate and work-related driving behaviors, as well as questions relating to participant demographics and information about their work driving. Results The results demonstrated that safety climate significantly moderated the effect of thrill and adventure seeking trait on driving errors, driving violations, and driving while fatigued. Conclusion These results suggest that the development of a strong safety climate has the potential to improve work driving safety outcomes by reducing the impact of particular personality traits such as thrill seeking within an organizational context. Practical application To improve work driving safety, organizations and management need to develop strategies to encourage and foster positive work driving safety climate, particularly within work settings that may attract thrill and adventure seeking employees.
Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO<sub>2</sub> tolerance in phytoplankton productivity
Publisher: Copernicus GmbH
Date: 11-01-2018
Abstract: Abstract. High-latitude oceans are anticipated to be some of the first regions affected by ocean acidification. Despite this, the effect of ocean acidification on natural communities of Antarctic marine microbes is still not well understood. In this study we exposed an early spring, coastal marine microbial community in Prydz Bay to CO2 levels ranging from ambient (343 µatm) to 1641 µatm in six 650 L minicosms. Productivity assays were performed to identify whether a CO2 threshold existed that led to a change in primary productivity, bacterial productivity, and the accumulation of chlorophyll a (Chl a) and particulate organic matter (POM) in the minicosms. In addition, photophysiological measurements were performed to identify possible mechanisms driving changes in the phytoplankton community. A critical threshold for tolerance to ocean acidification was identified in the phytoplankton community between 953 and 1140 µatm. CO2 levels ≥ 1140 µatm negatively affected photosynthetic performance and Chl a-normalised primary productivity (csGPP14C), causing significant reductions in gross primary production (GPP14C), Chl a accumulation, nutrient uptake, and POM production. However, there was no effect of CO2 on C : N ratios. Over time, the phytoplankton community acclimated to high CO2 conditions, showing a down-regulation of carbon concentrating mechanisms (CCMs) and likely adjusting other intracellular processes. Bacterial abundance initially increased in CO2 treatments ≥ 953 µatm (days 3–5), yet gross bacterial production (GBP14C) remained unchanged and cell-specific bacterial productivity (csBP14C) was reduced. Towards the end of the experiment, GBP14C and csBP14C markedly increased across all treatments regardless of CO2 availability. This coincided with increased organic matter availability (POC and PON) combined with improved efficiency of carbon uptake. Changes in phytoplankton community production could have negative effects on the Antarctic food web and the biological pump, resulting in negative feedbacks on anthropogenic CO2 uptake. Increases in bacterial abundance under high CO2 conditions may also increase the efficiency of the microbial loop, resulting in increased organic matter remineralisation and further declines in carbon sequestration.
Regional and Microenvironmental Scale Characterization of the Zostera muelleri Seagrass Microbiome.
Publisher: Frontiers Media SA
Date: 14-05-2019
Abstract: Seagrasses are globally distributed marine plants that represent an extremely valuable component of coastal ecosystems. Like terrestrial plants, seagrass productivity and health are likely to be strongly governed by the structure and function of the seagrass microbiome, which will be distributed across a number of discrete microenvironments within the plant, including the phyllosphere, the endosphere and the rhizosphere, all different in physical and chemical conditions. Here we examined patterns in the composition of the microbiome of the seagrass Zostera muelleri , within six plant-associated microenvironments s led across four different coastal locations in New South Wales, Australia. Amplicon sequencing approaches were used to characterize the ersity and composition of bacterial, microalgal, and fungal microbiomes and ultimately identify “core microbiome” members that were conserved across s ling microenvironments. Discrete populations of bacteria, microalgae and fungi were observed within specific seagrass microenvironments, including the leaves and roots and rhizomes, with “core” taxa found to persist within these microenvironments across geographically disparate s ling sites. Bacterial, microalgal and fungal community profiles were most strongly governed by intrinsic features of the different seagrass microenvironments, whereby microscale differences in community composition were greater than the differences observed between s ling regions. However, our results showed differing strengths of microbial preferences at the plant scale, since this microenvironmental variability was more pronounced for bacteria than it was for microalgae and fungi, suggesting more specific interactions between the bacterial consortia and the seagrass host, and potentially implying a highly specialized coupling between seagrass and bacterial metabolism and ecology. Due to their persistence within a given seagrass microenvironment, across geographically discrete s ling locations, we propose that the identified “core” microbiome members likely play key roles in seagrass physiology as well as the ecology and biogeochemistry of seagrass habitats.
Southern Ocean phytoplankton physiology in a changing climate
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.JPLPH.2016.05.004
Abstract: The Southern Ocean (SO) is a major sink for anthropogenic atmospheric carbon dioxide (CO
The impact of iron limitation on the physiology of the Antarctic diatom Chaetoceros simplex
Publisher: Springer Science and Business Media LLC
Date: 29-01-2014
A novel mechanism for host-mediated photoprotection in endosymbiotic foraminifera
Publisher: Springer Science and Business Media LLC
Date: 11-2016
A biophysical representation of seagrass growth for application in a complex shallow-water biogeochemical model
Publisher: Elsevier BV
Date: 04-2016
Can we manage coastal ecosystems to sequester more blue carbon?
Publisher: Wiley
Date: 10-04-2017
DOI: 10.1002/FEE.1484
Shifts in dimethylated sulfur concentrations and microbiome composition in the red-tide causing dinoflagellate <i>Alexandrium minutum</i> during a simulated marine heatwave
Publisher: Copernicus GmbH
Date: 19-11-2019
Abstract: Abstract. The biogenic sulfur compounds dimethyl sulfide (DMS), dimethyl sulfoniopropionate (DMSP) and dimethyl sulfoxide (DMSO) are produced and transformed by erse populations of marine microorganisms and have substantial physiological, ecological and biogeochemical importance spanning organism to global scales. Understanding the production and transformation dynamics of these compounds under shifting environmental conditions is important for predicting their roles in a changing ocean. Here, we report the physiological and biochemical response of a robust strain of Alexandrium minutum, a dinoflagellate with the highest reported intracellular DMSP content, exposed to a 6 d increase in temperature mimicking mild and extreme coastal marine heatwave conditions (+4 and +12 ∘C). Under mild temperature increases (+4 ∘C), A. minutum growth was enhanced, with no measurable physiological stress response. However, under a very acute increase in temperature (+12 ∘C) triggering thermal stress, A. minutum growth declined, photosynthetic efficiency (FV∕FM) was impaired, and enhanced oxidative stress was observed. These physiological responses indicative of thermal stress were accompanied by increased DMS and DMSO concentrations followed by decreased DMSP concentration. At this temperature extreme, we observed a cascading stress response in A. minutum, which was initiated 6 h after the start of the experiment by a spike in DMS and DMSO concentrations and a rapid decrease in FV∕FM. This was followed by an increase in reactive oxygen species (ROS) and an abrupt decline in DMS and DMSO on day 2 of the experiment. A subsequent decrease in DMSP coupled with a decline in the growth rate of both A. minutum and its associated total bacterial assemblage coincided with a shift in the composition of the A. minutum microbiome. Specifically, an increase in the relative abundance of the operational taxonomic units (OTUs) matching Oceanicaulis (17.0 %), Phycisphaeraceae SM1A02 (8.8 %) and Balneola (4.9 %) as well as a decreased relative abundance of Maribacter (24.4 %), Marinoscillum (4.7 %) and Seohaeicola (2.7 %) were primarily responsible for differences in microbiome structure observed between temperature treatments. These shifts in microbiome structure are likely to have been driven by either the temperature itself, the changing physiological state of A. minutum cells, shifts in biogenic sulfur concentrations, the presence of other solutes, or a combination of all. Nevertheless, we suggest that these results point to the significant effect of extreme heatwaves on the physiology, growth and microbiome composition of the red-tide causing dinoflagellate A. minutum, as well as potential implications for biogenic sulfur cycling processes and marine DMS emissions.
Ocean acidification alters the nutritional value of Antarctic diatoms
Publisher: Wiley
Date: 05-01-2022
DOI: 10.1111/NPH.17868
Abstract: Primary production in the Southern Ocean is dominated by diatom‐rich phytoplankton assemblages, whose in idual physiological characteristics and community composition are strongly shaped by the environment, yet knowledge on how diatoms allocate cellular energy in response to ocean acidification (OA) is limited. Understanding such changes in allocation is integral to determining the nutritional quality of diatoms and the subsequent impacts on the trophic transfer of energy and nutrients. Using synchrotron‐based Fourier transform infrared microspectroscopy, we analysed the macromolecular content of selected in idual diatom taxa from a natural Antarctic phytoplankton community exposed to a gradient of f CO 2 levels (288–1263 µatm). Strong species‐specific differences in macromolecular partitioning were observed under OA. Large taxa showed preferential energy allocation towards proteins, while smaller taxa increased both lipid and protein stores at high f CO 2 . If these changes are representative of future Antarctic diatom physiology, we may expect a shift away from lipid‐rich large diatoms towards a community dominated by smaller taxa, but with higher lipid and protein stores than their present‐day contemporaries, a response that could have cascading effects on food web dynamics in the Antarctic marine ecosystem.
A multi-trait systems approach reveals a response cascade to bleaching in corals
Publisher: Springer Science and Business Media LLC
Date: 12-2017
Nutrient uplift in a cyclonic eddy increases diversity, primary productivity and iron demand of microbial communities relative to a western boundary current
Publisher: PeerJ
Date: 25-04-2016
DOI: 10.7717/PEERJ.1973
Abstract: The intensification of western boundary currents in the global ocean will potentially influence meso-scale eddy generation, and redistribute microbes and their associated ecological and biogeochemical functions. To understand eddy-induced changes in microbial community composition as well as how they control growth, we targeted the East Australian Current (EAC) region to s le microbes in a cyclonic (cold-core) eddy (CCE) and the adjacent EAC. Phototrophic and diazotrophic microbes were more erse (2–10 times greater Shannon index) in the CCE relative to the EAC, and the cell size distribution in the CCE was dominated (67%) by larger micro-plankton $(\\geq 20\\lrm{\\mu }\\mathrm{m})$, as opposed to pico- and nano-sized cells in the EAC. Nutrient addition experiments determined that nitrogen was the principal nutrient limiting growth in the EAC, while iron was a secondary limiting nutrient in the CCE. Among the diazotrophic community, heterotrophic NifH gene sequences dominated in the EAC and were attributable to members of the gamma-, beta-, and delta-proteobacteria, while the CCE contained both phototrophic and heterotrophic diazotrophs, including Trichodesmium , UCYN-A and gamma-proteobacteria. Daily s ling of incubation bottles following nutrient amendment captured a cascade of effects at the cellular, population and community level, indicating taxon-specific differences in the speed of response of microbes to nutrient supply. Nitrogen addition to the CCE community increased picoeukaryote chlorophyll a quotas within 24 h, suggesting that nutrient uplift by eddies causes a ‘greening’ effect as well as an increase in phytoplankton biomass. After three days in both the EAC and CCE, diatoms increased in abundance with macronutrient (N, P, Si) and iron amendment, whereas haptophytes and phototrophic dinoflagellates declined. Our results indicate that cyclonic eddies increase delivery of nitrogen to the upper ocean to potentially mitigate the negative consequences of increased stratification due to ocean warming, but also increase the biological demand for iron that is necessary to sustain the growth of large-celled phototrophs and potentially support the ersity of diazotrophs over longer time-scales.
Snapshot prediction of carbon productivity, carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy
Publisher: Springer Science and Business Media LLC
Date: 31-07-2016
Reactive oxygen species (ROS) and dimethylated sulphur compounds in coral explants under acute thermal stress
Publisher: The Company of Biologists
Date: 2017
DOI: 10.1242/JEB.153049
Abstract: Coral bleaching is intensifying with global climate change. Although the causes for these catastrophic events are well understood, the cellular mechanism that triggers bleaching is not well established. Our understanding of coral bleaching processes is hindered by the lack of robust methods for studying interactions between host and symbiont at the single-cell level. Here, we exposed coral explants to acute thermal stress and measured oxidative stress, more specifically, reactive oxygen species (ROS), in in idual symbiont cells. Furthermore, we measured concentrations of dimethylsulphoniopropionate (DMSP) and dimethylsulphoxide (DMSO) to elucidate the role of these compounds in coral antioxidant function. This work demonstrates the application of coral explants for investigating coral physiology and biochemistry under thermal stress and delivers a new approach to study host-symbiont interactions at the microscale, allowing us to directly link intracellular ROS with DMSP and DMSO dynamics.
Photophysiological responses of fragilariopsis cylindrus (bacillariophyceae) to nitrogen depletion at two temperatures
Publisher: Wiley
Date: 20-12-2012
DOI: 10.1111/J.1529-8817.2011.01107.X
Abstract: The photosynthetic efficiency and photoprotective capacity of the sea-ice diatom, Fragilariopsis cylindrus (Grunow) W. Krieg., grown in a matrix of nitrogen repletion and depletion at two different temperatures (-1°C and +6°C) was investigated. Temperature showed no significant effect on photosynthetic efficiency or photoprotection in F. cylindrus. Cultures under nitrogen depletion showed enhanced photoprotective capacity with an increase in nonphotochemical quenching (NPQ) when compared with nitrogen-replete cultures. This phenomenon was achieved at no apparent cost to the photosynthetic efficiency of PSII (FV /FM ). Nitrogen depletion yielded a partially reduced electron transport chain in which maximum fluorescence (FM ) could only be obtained by adding 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). reoxidation curves showed the presence of QB nonreducing PSII centers under nitrogen depletion. Fast induction curves (FICs) and electron transport rates (ETRs) revealed slowing of the electrons transferred from the primary (QA ) to the secondary (QB ) quinone electron acceptors of PSII. The data presented show that nitrogen depletion in F. cylindrus leads to the formation of QB nonreducing PSII centers within the photosystem. On a physiological level, the formation of QB nonreducing PSII centers in F. cylindrus provides the cell with protection against photoinhibition by facilitating the rapid induction of NPQ. This strategy provides an important ecological advantage, especially during the Antarctic spring, maintaining photosynthetic efficiency under high light and nutrient-limiting conditions.
Can macroalgae contribute to blue carbon? An Australian perspective
Publisher: Wiley
Date: 25-06-2015
DOI: 10.1002/LNO.10128
Photosynthesis and net primary productivity in three Antarctic diatoms: possible significance for their distribution in the Antarctic marine ecosystem
Publisher: Inter-Research Science Center
Date: 15-09-2011
DOI: 10.3354/MEPS09291
Rapid photoprotection in sea-ice diatoms from the East Antarctic pack ice
Publisher: Wiley
Date: 05-2010
Dimethylsulfoniopropionate, superoxide dismutase and glutathione as stress response indicators in three corals under short-term hyposalinity stress
Publisher: The Royal Society
Date: 10-02-2016
Abstract: Corals are among the most active producers of dimethylsulfoniopropionate (DMSP), a key molecule in marine sulfur cycling, yet the specific physiological role of DMSP in corals remains elusive. Here, we examine the oxidative stress response of three coral species ( Acropora millepora , Stylophora pistillata and Pocillopora damicornis ) and explore the antioxidant role of DMSP and its breakdown products under short-term hyposalinity stress. Symbiont photosynthetic activity declined with hyposalinity exposure in all three reef-building corals. This corresponded with the upregulation of superoxide dismutase and glutathione in the animal host of all three species. For the symbiont component, there were differences in antioxidant regulation, demonstrating differential responses to oxidative stress between the Symbiodinium subclades. Of the three coral species investigated, only A. millepora provided any evidence of the role of DMSP in the oxidative stress response. Our study reveals variability in antioxidant regulation in corals and highlights the influence life-history traits, and the subcladal differences can have on coral physiology. Our data expand on the emerging understanding of the role of DMSP in coral stress regulation and emphasizes the importance of exploring both the host and symbiont responses for defining the threshold of the coral holobiont to hyposalinity stress.
Partitioning of fungal assemblages across different marine habitats
Publisher: Wiley
Date: 16-02-2016
Abstract: Fungi are a highly erse group of microbes that fundamentally influence the biogeochemistry of the biosphere, but we currently know little about the ersity and distribution of fungi in aquatic habitats. Here we describe shifts in marine fungal community composition across different marine habitats, using targeted pyrosequencing of the fungal Internal Transcribed Spacer (ITS) region. Our results demonstrate strong partitioning of fungal community composition between estuarine, coastal and oceanic s les, with each habitat hosting discrete communities that are controlled by patterns in salinity, temperature, oxygen and nutrients. Whereas estuarine habitats comprised a significant proportion of fungal groups often found in terrestrial habitats, the open ocean sites were dominated by previously unidentified groups. The patterns observed here indicate that fungi are potentially a significant, although largely overlooked, feature of the ocean's microbiota, but greater efforts to characterize marine species are required before the full ecological and biogeochemical importance of marine fungi can be ascertained.
The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones
Publisher: Copernicus GmbH
Date: 02-2011
Abstract: Abstract. The roles of iron and light in controlling biomass and primary productivity are clearly established in the Southern Ocean. However, their influence on net community production (NCP) and carbon export remains to be quantified. To improve our understanding of NCP and carbon export production in the Subantarctic Zone (SAZ) and the northern reaches of the Polar Frontal Zone (PFZ), we conducted continuous onboard determinations of NCP as part of the Sub-Antarctic Sensitivity to Environmental Change (SAZ-Sense) study, which occurred in January–February 2007. Biological O2 supersaturation was derived from measuring O2/Ar ratios by equilibrator inlet mass spectrometry. Based on these continuous measurements, NCP during the austral summer 2007 in the Australian SAZ was approximately 43 mmol O2 m−2 d−1. NCP showed significant spatial variability, with larger values near the Subtropical front, and a general southward decrease. For shallower mixed layers ( m), dissolved Fe concentrations and Fe sufficiency, estimated from variable fluorescence, correlated strongly with NCP. The strong correlation between NCP and dissolved Fe may be difficult to interpret because of the correlation of dissolved Fe to MLD and because the concentration of iron may not be a good indicator of its availability. At stations with deeper mixed layers, NCP was consistently low, regardless of iron sufficiency, consistent with light availability also being an important control of NCP. Our new observations provide independent evidence for the critical roles of iron and light in mediating carbon export from the Southern Ocean mixed layer.
Iron-limitation and high light stress on phytoplankton populations from the Australian Sub-Antarctic Zone (SAZ)
Publisher: Elsevier BV
Date: 11-2011
Diel variation of chlorophyll-a fluorescence, phytoplankton pigments and productivity in the Sub-Antarctic and Polar Front Zones south of Tasmania, Australia
Publisher: Elsevier BV
Date: 11-2011
NLRC5 promotes transcription of BTN3A1-3 genes and Vγ9Vδ2 T cell-mediated killing
Publisher: Elsevier BV
Date: 2021
Microbial tropicalization driven by a strengthening western ocean boundary current
Publisher: Wiley
Date: 27-07-2020
DOI: 10.1111/GCB.15257
The CD3 Conformational Change in the γδ T Cell Receptor Is Not Triggered by Antigens but Can Be Enforced to Enhance Tumor Killing
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.CELREP.2014.04.049
Abstract: Activation of the T cell receptor (TCR) by antigen is the key step in adaptive immunity. In the αβTCR, antigen induces a conformational change at the CD3 subunits (CD3 CC) that is absolutely required for αβTCR activation. Here, we demonstrate that the CD3 CC is not induced by antigen stimulation of the mouse G8 or the human Vγ9Vδ2 γδTCR. We find that there is a fundamental difference between the activation mechanisms of the αβTCR and γδTCR that map to the constant regions of the TCRαβ/γδ heterodimers. Enforced induction of CD3 CC with a less commonly used monoclonal anti-CD3 promoted proximal γδTCR signaling but inhibited cytokine secretion. Utilizing this knowledge, we could dramatically improve in vitro tumor cell lysis by activated human γδ T cells. Thus, manipulation of the CD3 CC might be exploited to improve clinical γδ T cell-based immunotherapies.
Seasonal heterogeneity in the photophysiological response to air exposure in two tropical intertidal seagrass species
Publisher: Inter-Research Science Center
Date: 22-05-2013
DOI: 10.3354/MEPS10229
Desiccation stress in two intertidal beachrock biofilms
Publisher: Springer Science and Business Media LLC
Date: 17-05-2014
Phytoplankton Sources and Sinks of Dimethylsulphoniopropionate (DMSP) in Temperate Coastal Waters of Australia
Publisher: MDPI AG
Date: 29-07-2022
DOI: 10.3390/MICROORGANISMS10081539
Abstract: The ecologically important organic sulfur compound, dimethylsulfoniopropionate (DMSP), is ubiquitous in marine environments. Produced by some species of phytoplankton and bacteria, it plays a key role in cellular responses to environmental change. Recently, uptake of DMSP by non-DMSP-producing phytoplankton species has been demonstrated, highlighting knowledge gaps concerning DMSP distribution through the marine microbial food web. In this study, we traced the uptake and distribution of DMSP through a natural marine microbial community collected from off the eastern coastline Australia. We found a erse phytoplankton community representing six major taxonomic groups and conducted DMSP-enrichment experiments both on the whole community, and the community separated into large (≥8.0 µm), medium (3.0–8.0 µm), and small (0.2–3.0 µm) size fractions. Our results revealed active uptake of DMSP in all three size fractions of the community, with the largest fraction ( µm) forming the major DMSP sink, where enrichment resulted in an increase of DMSPp by 144%. We observed evidence for DMSP catabolism in all size fractions with DMSP enrichment, highlighting loss from the system via MeSH or DMS production. Based on taxonomic ersity, we postulate the sources of DMSP were the dinoflagellates, Phaeocystis sp., and Trichodesmium sp., which were present in a relatively high abundance, and the sinks for DMSP were the diatoms and picoeucaryotes in this temperate community. These findings corroborate the role of hitherto disregarded phytoplankton taxa as potentially important players in the cycling of DMSP in coastal waters of Australia and emphasize the need to better understand the fate of accumulated DMSP and its significance in cellular metabolism of non-DMSP producers.
The BTG2-PRMT1 module limits pre-B cell expansion by regulating the CDK4-Cyclin-D3 complex
Publisher: Springer Science and Business Media LLC
Date: 19-06-2017
DOI: 10.1038/NI.3774
Abstract: Developing pre-B cells in the bone marrow alternate between proliferation and differentiation phases. We found that protein arginine methyl transferase 1 (PRMT1) and B cell translocation gene 2 (BTG2) are critical components of the pre-B cell differentiation program. The BTG2-PRMT1 module induced a cell-cycle arrest of pre-B cells that was accompanied by re-expression of Rag1 and Rag2 and the onset of immunoglobulin light chain gene rearrangements. We found that PRMT1 methylated cyclin-dependent kinase 4 (CDK4), thereby preventing the formation of a CDK4-Cyclin-D3 complex and cell cycle progression. Moreover, BTG2 in concert with PRMT1 efficiently blocked the proliferation of BCR-ABL1-transformed pre-B cells in vitro and in vivo. Our results identify a key molecular mechanism by which the BTG2-PRMT1 module regulates pre-B cell differentiation and inhibits pre-B cell leukemogenesis.
Heterogeneity in the photoprotective capacity of three Antarctic diatoms during short-term changes in salinity and temperature
Publisher: Springer Science and Business Media LLC
Date: 28-01-2011
Fluorescence as a Tool to Understand Changes in Photosynthetic Electron Flow Regulation
Publisher: Springer Netherlands
Date: 2010
Photoprotection of sea-ice microalgal communities from the east antarctic pack ice
Publisher: Wiley
Date: 13-01-2011
DOI: 10.1111/J.1529-8817.2010.00944.X
Abstract: All photosynthetic organisms endeavor to balance energy supply with demand. For sea-ice diatoms, as with all marine photoautotrophs, light is the most important factor for determining growth and carbon-fixation rates. Light varies from extremely low to often relatively high irradiances within the sea-ice environment, meaning that sea-ice algae require moderate physiological plasticity that is necessary for rapid light acclimation and photoprotection. This study investigated photoprotective mechanisms employed by bottom Antarctic sea-ice algae in response to relatively high irradiances to understand how they acclimate to the environmental conditions presented during early spring, as the light climate begins to intensify and snow and sea-ice thinning commences. The sea-ice microalgae displayed high photosynthetic plasticity to increased irradiance, with a rapid decline in photochemical efficiency that was completely reversible when placed under low light. Similarly, the photoprotective xanthophyll pigment diatoxanthin (Dt) was immediately activated but reversed during recovery under low light. The xanthophyll inhibitor dithiothreitol (DTT) and state transition inhibitor sodium fluoride (NaF) were used in under-ice in situ incubations and revealed that nonphotochemical quenching (NPQ) via xanthophyll-cycle activation was the preferred method for light acclimation and photoprotection by bottom sea-ice algae. This study showed that bottom sea-ice algae from the east Antarctic possess a high level of plasticity in their light-acclimation capabilities and identified the xanthophyll cycle as a critical mechanism in photoprotection and the preferred means by which sea-ice diatoms regulate energy flow to PSII.
State transitions and nonphotochemical quenching during a nutrient-induced fluorescence transient in phosphorus-starved Dunaliella tertiolecta
Publisher: Wiley
Date: 10-2008
DOI: 10.1111/J.1529-8817.2008.00585.X
Abstract: Assessments of nutrient-limitation in microalgae using chl a fluorescence have revealed that nitrogen and phosphorus depletion can be detected as a change in chl a fluorescence signal when nutrient-starved algae are resupplied with the limiting nutrient. This photokinetic phenomenon is known as a nutrient-induced fluorescence transient, or NIFT. Cultures of the unicellular marine chlorophyte Dunaliella tertiolecta Butcher were grown under phosphate starvation to investigate the photophysiological mechanism behind the NIFT response. A combination of low temperature (77 K) fluorescence, photosynthetic inhibitors, and nonphotochemical quenching analyses were used to determine that the NIFT response is associated with changes in energy distribution between PSI and PSII and light-stress-induced nonphotochemical quenching (NPQ). Previous studies point to state transitions as the likely mechanism behind the NIFT response however, our results show that state transitions are not solely responsible for this phenomenon. This study shows that an interaction of at least two physiological processes is involved in the rapid quenching of chl a fluorescence observed in P-starved D. tertiolecta: (1) state transitions to provide the nutrient-deficient cell with metabolic energy for inorganic phosphate (Pi )-uptake and (2) energy-dependent quenching to allow the nutrient-stressed cell to avoid photodamage from excess light energy during nutrient uptake.
Phenotypic plasticity of southern ocean diatoms: Key to success in the sea ice habitat?
Publisher: Public Library of Science (PLoS)
Date: 21-11-2013
Related Organisations
Institute For Biology III, Faculty Of Biology, University Of Freiburg, Germany
Location: Germany
Related Funding Activities
Discovery Projects - Grant ID: DP140101045
Start Date: 2014
End Date: 12-2017
Amount: $588,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP210101360
Start Date: 06-2021
End Date: 05-2024
Amount: $531,000.00
Funder: Australian Research Council
View Funded Activity