I grew up in Corsica (France) and completed my PhD on Bacterial Symbioses in Nautiloids at the University Pierre and Marie Curie in Paris (2006). This was followed by a one-year Teaching and Researching position on “Phylogenetic and functional aspects of bacterial symbioses in Cephalopods” at the National Museum of Natural History in Paris (2007-2008).
In 2008, I was awarded with a three-year Marie Curie outgoing postdoctoral fellowship to study the influence of environmental stresses on cnidaria-dinoflagellate symbioses in Australia (University of Queensland, Brisbane). In January 2012, I started a postdoctoral contract funded by the Swiss National Science Foundation (EPFL, Lausanne Switzerland) to undertake collaborative research with the Climate Change Cluster (C3) combining my technical skills and knowledge on symbiosis with world leading expertise in coral photobiology and modelling.
Since January 2014, I am a Research fellow and deputy team leader within (C3), where I develop research on coral symbiosis, seagrass and genetic engineering of microalgae. The ultimate aim of this research is to develop and implement the next generation of Environmental Impact Assessment on marine ecosystems including coral reefs and seagrass.
Member of the International Symbiosis Society
Member of editorial board of Nature Scientific Reports, Frontiers in Microbial Symbioses (Frontiers Microbiology) and Frontiers in Coral research (Frontiers in Marine Science).
Reviewer of scientific papers for ISME Journal,Trends in Microbiology, Environmental Microbiology, Frontiers Microbiology, Molecular Ecology, Bioessays, Plos ONE, Journal of Experimental Biology, Autophagy, Marine Biology, Marine Environmental Research, Marine Biotechnology, Ecotoxicology.
- Ecophysiology of symbioses
- Development of sublethal markers of stress for coral reef and seagrass monitoring
- Genetic engineering of microalgae
- Development of imaging techniques combined with isotopic labelling to study metabolic function
Coral reef Ecosystems:
Coordinator of coral bleaching project on the Marine Productivity and Climate Change (42h, UTS Subject Number 91156).
Programme director for the Advanced Degree in Environmental Biotechnology and Lecturer for Biotechnology (2h, UTS Subject Number 91142).
Other teaching areas include: Seagrass, Symbiotic interactions, Environmental Impact Assessment, Molecular Biology, Physiology.
Achlatis, M., Pernice, M., Green, K., Guagliardo, P., Kilburn, M.R., Hoegh-Guldberg, O. & Dove, S. 2018, 'Single-cell measurement of ammonium and bicarbonate uptake within a photosymbiotic bioeroding sponge.', The ISME journal.View/Download from: Publisher's site
Some of the most aggressive coral-excavating sponges host intracellular dinoflagellates from the genus Symbiodinium, which are hypothesized to provide the sponges with autotrophic energy that powers bioerosion. Investigations of the contribution of Symbiodinium to host metabolism and particularly inorganic nutrient recycling are complicated, however, by the presence of alternative prokaryotic candidates for this role. Here, novel methods are used to study nutrient assimilation and transfer within and between the outer-layer cells of the Indopacific bioeroding sponge Cliona orientalis. Combining stable isotope labelling, transmission electron microscopy (TEM) and nanoscale secondary ion mass spectrometry (NanoSIMS), we visualize and measure metabolic activity at the individual cell level, tracking the fate of 15N-ammonium and 13C-bicarbonate within the intact holobiont. We found strong uptake of both inorganic sources (especially 13C-bicarbonate) by Symbiodinium cells. Labelled organic nutrients were translocated from Symbiodinium to the Symbiodinium-hosting sponge cells within 6h, and occasionally to other sponge cells within 3 days. By contrast, prokaryotic symbionts were not observed to participate in inorganic nutrient assimilation in the outer layers of the sponge. Our findings strongly support the metabolic interaction between the sponge and dinoflagellates, shedding light on the ecological advantages and adaptive capacity of photosymbiotic bioeroding sponges in oligotrophic marine habitats.
Davey, P.A., Pernice, M., Ashworth, J., Kuzhiumparambil, U., Szabó, M., Dolferus, R. & Ralph, P.J. 2018, 'A new mechanistic understanding of light-limitation in the seagrass Zostera muelleri.', Marine environmental research, vol. 134, pp. 55-67.View/Download from: Publisher's site
In this study we investigated the effect of light-limitation (20mol photons m-2s-1) on the southern hemisphere seagrass, Zostera muelleri. RNA sequencing, chlorophyll fluorometry and HPLC techniques were used to investigate how the leaf-specific transcriptome drives changes in photosynthesis and photo-pigments in Z. muelleri over 6 days. 1593 (7.51%) genes were differentially expressed on day 2 and 1481 (6.98%) genes were differentially expressed on day 6 of the experiment. Differential gene expression correlated with significant decreases in rETRMax, Ik, an increase in Yi (initial photosynthetic quantum yield of photosystem II), and significant changes in pigment composition. Regulation of carbohydrate metabolism was observed along with evidence that abscisic acid may serve a role in the low-light response of this seagrass. This study provides a novel understanding of how Z. muelleri responds to light-limitation in the marine water column and provides potential molecular markers for future conservation monitoring efforts.
Sablok, G., Hayward, R.J., Davey, P.A., Santos, R.P., Schliep, M., Larkum, A., Pernice, M., Dolferus, R. & Ralph, P.J. 2018, 'SeagrassDB: An open-source transcriptomics landscape for phylogenetically profiled seagrasses and aquatic plants.', Scientific reports, vol. 8, no. 1, p. 2749.View/Download from: Publisher's site
Seagrasses and aquatic plants are important clades of higher plants, significant for carbon sequestration and marine ecological restoration. They are valuable in the sense that they allow us to understand how plants have developed traits to adapt to high salinity and photosynthetically challenged environments. Here, we present a large-scale phylogenetically profiled transcriptomics repository covering seagrasses and aquatic plants. SeagrassDB encompasses a total of 1,052,262 unigenes with a minimum and maximum contig length of 8,831bp and 16,705bp respectively. SeagrassDB provides access to 34,455 transcription factors, 470,568 PFAM domains, 382,528 prosite models and 482,121 InterPro domains across 9 species. SeagrassDB allows for the comparative gene mining using BLAST-based approaches and subsequent unigenes sequence retrieval with associated features such as expression (FPKM values), gene ontologies, functional assignments, family level classification, Interpro domains, KEGG orthology (KO), transcription factors and prosite information. SeagrassDB is available to the scientific community for exploring the functional genic landscape of seagrass and aquatic plants at: http://22.214.171.124/index.php .
Kim, M., Brodersen, K.E., Szabó, M., Larkum, A.W.D., Raven, J.A., Ralph, P.J. & Pernice, M. 2017, 'Low oxygen affects photophysiology and the level of expression of two-carbon metabolism genes in the seagrass Zostera muelleri.', Photosynthesis research.View/Download from: UTS OPUS or Publisher's site
Seagrasses are a diverse group of angiosperms that evolved to live in shallow coastal waters, an environment regularly subjected to changes in oxygen, carbon dioxide and irradiance. Zostera muelleri is the dominant species in south-eastern Australia, and is critical for healthy coastal ecosystems. Despite its ecological importance, little is known about the pathways of carbon fixation in Z. muelleri and their regulation in response to environmental changes. In this study, the response of Z. muelleri exposed to control and very low oxygen conditions was investigated by using (i) oxygen microsensors combined with a custom-made flow chamber to measure changes in photosynthesis and respiration, and (ii) reverse transcription quantitative real-time PCR to measure changes in expression levels of key genes involved in C4 metabolism. We found that very low levels of oxygen (i) altered the photophysiology of Z. muelleri, a characteristic of C3 mechanism of carbon assimilation, and (ii) decreased the expression levels of phosphoenolpyruvate carboxylase and carbonic anhydrase. These molecular-physiological results suggest that regulation of the photophysiology of Z. muelleri might involve a close integration between the C3 and C4, or other CO2 concentrating mechanisms metabolic pathways. Overall, this study highlights that the photophysiological response of Z. muelleri to changing oxygen in water is capable of rapid acclimation and the dynamic modulation of pathways should be considered when assessing seagrass primary production.
Goyen, S., Pernice, M., Szabó, M., Warner, M.E., Ralph, P.J. & Suggett, D.J. 2017, 'A molecular physiology basis for functional diversity of hydrogen peroxide production amongst Symbiodinium spp. (Dinophyceae)', Marine Biology: international journal on life in oceans and coastal waters, vol. 164, no. 3.View/Download from: UTS OPUS or Publisher's site
Wangpraseurt, D., Holm, J.B., Larkum, A.W.D., Pernice, M., Ralph, P.J., Suggett, D.J. & Kühl, M. 2017, 'In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?', Frontiers in microbiology, vol. 8, p. 59.View/Download from: UTS OPUS or Publisher's site
Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching.
Raina, J.-.B., Clode, P.L., Cheong, S., Bougoure, J., Kilburn, M.R., Reeder, A., Forêt, S., Stat, M., Beltran, V., Thomas-Hall, P., Tapiolas, D., Motti, C.M., Gong, B., Pernice, M., Marjo, C.E., Seymour, J.R., Willis, B.L. & Bourne, D.G. 2017, 'Subcellular tracking reveals the location of dimethylsulfoniopropionate in microalgae and visualises its uptake by marine bacteria.', eLife, vol. 6, pp. 1-17.View/Download from: UTS OPUS or Publisher's site
Phytoplankton-bacteria interactions drive the surface ocean sulfur cycle and local climatic processes through the production and exchange of a key compound: dimethylsulfoniopropionate (DMSP). Despite their large-scale implications, these interactions remain unquantified at the cellular-scale. Here we use secondary-ion mass spectrometry to provide the first visualization of DMSP at sub-cellular levels, tracking the fate of a stable sulfur isotope ((34)S) from its incorporation by microalgae as inorganic sulfate to its biosynthesis and exudation as DMSP, and finally its uptake and degradation by bacteria. Our results identify for the first time the storage locations of DMSP in microalgae, with high enrichments present in vacuoles, cytoplasm and chloroplasts. In addition, we quantify DMSP incorporation at the single-cell level, with DMSP-degrading bacteria containing seven times more (34)S than the control strain. This study provides an unprecedented methodology to label, retain, and image small diffusible molecules, which can be transposable to other symbiotic systems.
Jiang, Z., Kumar, M., Padula, M.P., Pernice, M., Kahlke, T., Kim, M. & Ralph, P.J. 2017, 'Development of an Efficient Protein Extraction Method Compatible with LC-MS/MS for Proteome Mapping in Two Australian Seagrasses Zostera muelleri and Posidonia australis.', Frontiers in plant science, vol. 8, p. 1416.View/Download from: UTS OPUS or Publisher's site
The availability of the first complete genome sequence of the marine flowering plant Zostera marina (commonly known as seagrass) in early 2016, is expected to significantly raise the impact of seagrass proteomics. Seagrasses are marine ecosystem engineers that are currently declining worldwide at an alarming rate due to both natural and anthropogenic disturbances. Seagrasses (especially species of the genus Zostera) are compromised for proteomic studies primarily due to the lack of efficient protein extraction methods because of their recalcitrant cell wall which is rich in complex polysaccharides and a high abundance of secondary metabolites in their cells. In the present study, three protein extraction methods that are commonly used in plant proteomics i.e., phenol (P); trichloroacetic acid/acetone/SDS/phenol (TASP); and borax/polyvinyl-polypyrrolidone/phenol (BPP) extraction, were evaluated quantitatively and qualitatively based on two dimensional isoelectric focusing (2D-IEF) maps and LC-MS/MS analysis using the two most abundant Australian seagrass species, namely Zostera muelleri and Posidonia australis. All three tested methods produced high quality protein extracts with excellent 2D-IEF maps in P. australis. However, the BPP method produces better results in Z. muelleri compared to TASP and P. Therefore, we further modified the BPP method (M-BPP) by homogenizing the tissue in a modified protein extraction buffer containing both ionic and non-ionic detergents (0.5% SDS; 1.5% Triton X-100), 2% PVPP and protease inhibitors. Further, the extracted proteins were solubilized in 0.5% of zwitterionic detergent (C7BzO) instead of 4% CHAPS. This slight modification to the BPP method resulted in a higher protein yield, and good quality 2-DE maps with a higher number of protein spots in both the tested seagrasses. Further, the M-BPP method was successfully utilized in western-blot analysis of phosphoenolpyruvate carboxylase (PEPC-a key enzyme for carbon metabolism). ...
Davey, P.A., Pernice, M., Sablok, G., Larkum, A., Lee, H.T., Golicz, A., Edwards, D., Dolferus, R. & Ralph, P. 2016, 'The emergence of molecular profiling and omics techniques in seagrass biology; furthering our understanding of seagrasses.', Functional & Integrative Genomics, vol. 16, no. 5, pp. 465-480.View/Download from: UTS OPUS or Publisher's site
Seagrass meadows are disappearing at alarming rates as a result of increasing coastal development and climate change. The emergence of omics and molecular profiling techniques in seagrass research is timely, providing a new opportunity to address such global issues. Whilst these applications have transformed terrestrial plant research, they have only emerged in seagrass research within the past decade; In this time frame we have observed a significant increase in the number of publications in this nascent field, and as of this year the first genome of a seagrass species has been sequenced. In this review, we focus on the development of omics and molecular profiling and the utilization of molecular markers in the field of seagrass biology. We highlight the advances, merits and pitfalls associated with such technology, and importantly we identify and address the knowledge gaps, which to this day prevent us from understanding seagrasses in a holistic manner. By utilizing the powers of omics and molecular profiling technologies in integrated strategies, we will gain a better understanding of how these unique plants function at the molecular level and how they respond to on-going disturbance and climate change events.
Ros, M., Pernice, M., Le Guillou, S., Doblin, M.A., Schrameyer, V. & Laczka, O. 2016, 'Colorimetric detection of caspase 3 activity and reactive oxygen derivatives: Potential early indicators of thermal stress in corals', Journal of Marine Biology, vol. 2016, pp. 1-11.View/Download from: UTS OPUS or Publisher's site
© 2016 Mickael Ros et al. There is an urgent need to develop and implement rapid assessments of coral health to allow effective adaptive management in response to coastal development and global change. There is now increasing evidence that activation of caspase-dependent apoptosis plays a key role during coral bleaching and subsequent mortality. In this study, a "clinical" approach was used to assess coral health by measuring the activity of caspase 3 using a commercial kit. This method was first applied while inducing thermal bleaching in two coral species, Acropora millepora and Pocillopora damicornis. The latter species was then chosen to undergo further studies combining the detection of oxidative stress-related compounds (catalase activity and glutathione concentrations) as well as caspase activity during both stress and recovery phases. Zooxanthellae photosystem II (PSII) efficiency and cell density were measured in parallel to assess symbiont health. Our results demonstrate that the increased caspase 3 activity in the coral host could be detected before observing any significant decrease in the photochemical efficiency of PSII in the algal symbionts and/or their expulsion from the host. This study highlights the potential of host caspase 3 and reactive oxygen species scavenging activities as early indicators of stress in individual coral colonies.
Wangpraseurt, D., Pernice, M., Guagliardo, P., Kilburn, M.R., Clode, P.L., Polerecky, L. & Kuehl, M. 2016, 'Light microenvironment and single-cell gradients of carbon fixation in tissues of symbiont-bearing corals', ISME JOURNAL, vol. 10, no. 3, pp. 788-792.View/Download from: UTS OPUS or Publisher's site
Pernice, M., Sinutok, S., Sablok, G., Commault, A., Schliep, M., Macreadie, P., Rasheed, M. & Ralph, P. 2016, 'Molecular physiology reveals ammonium uptake and related gene expression in the seagrass Zostera muelleri', Marine Environmental Research.View/Download from: UTS OPUS or Publisher's site
Kumar, M., Kuzhiumparambil, U., Pernice, M., Jiang, Z. & Ralph, P.J. 2016, 'Metabolomics: an emerging frontier of systems biology in marine macrophytes', ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS, vol. 16, pp. 76-92.View/Download from: UTS OPUS or Publisher's site
Kumar, M., Padula, M.P., Davey, P., Pernice, M., Jiang, Z., Sablok, G., Contreras-Porcia, L. & Ralph, P.J. 2016, 'Proteome Analysis Reveals Extensive Light Stress-Response Reprogramming in the Seagrass Zostera muelleri (Alismatales, Zosteraceae) Metabolism.', Frontiers in Plant Science, vol. 7, p. 2023.View/Download from: UTS OPUS or Publisher's site
Seagrasses are marine ecosystem engineers that are currently declining in abundance at an alarming rate due to both natural and anthropogenic disturbances in ecological niches. Despite reports on the morphological and physiological adaptations of seagrasses to extreme environments, little is known of the molecular mechanisms underlying photo-acclimation, and/or tolerance in these marine plants. This study applies the two-dimensional isoelectric focusing (2D-IEF) proteomics approach to identify photo-acclimation/tolerance proteins in the marine seagrass Zostera muelleri. For this, Z. muelleri was exposed for 10 days in laboratory mesocosms to saturating (control, 200 mol photons m-2 s-1), super-saturating (SSL, 600 mol photons m-2 s-1), and limited light (LL, 20 mol photons m-2 s-1) irradiance conditions. Using LC-MS/MS analysis, 93 and 40 protein spots were differentially regulated under SSL and LL conditions, respectively, when compared to the control. In contrast to the LL condition, Z. muelleri robustly tolerated super-saturation light than control conditions, evidenced by their higher relative maximum electron transport rate and minimum saturating irradiance values. Proteomic analyses revealed up-regulation and/or appearances of proteins belonging to the Calvin-Benson and Krebs cycle, glycolysis, the glycine cleavage system of photorespiration, and the antioxidant system. These proteins, together with those from the inter-connected glutamate-proline-GABA pathway, shaped Z. muelleri photosynthesis and growth under SSL conditions. In contrast, the LL condition negatively impacted the metabolic activities of Z. muelleri by down-regulating key metabolic enzymes for photosynthesis and the metabolism of carbohydrates and amino acids, which is consistent with the observation with lower photosynthetic performance under LL condition. This study provides novel insights into the underlying molecular photo-acclimation mechanisms in Z. muelleri, in addition to identify...
Pernice, M., Dunn, S.R., Tonk, L., Dove, S.G., Domart-Coulon, I., Hoppe, P., Schintlmeister, A., Wagner, M. & Meibom, A. 2015, 'A nanoscale secondary ion mass spectrometry study of dinoagellate functional diversity in reef-building corals', Environmental Microbiology, vol. 17, no. 10, pp. 3570-3580.View/Download from: UTS OPUS or Publisher's site
Nutritional interactions between corals and symbiotic dinoflagellate algae lie at the heart of the structural foundation of coral reefs. Whilst the genetic diversity of Symbiodinium has attracted particular interest because of its contribution to the sensitivity of corals to environmental changes and bleaching (i.e. disruption of coraldinoflagellate symbiosis), very little is known about the in hospite metabolic capabilities of different Symbiodinium types. Using a combination of stable isotopic labelling and nanoscale secondary ion mass spectrometry (NanoSIMS), we investigated the ability of the intact symbiosis between the reef-building coral Isopora palifera, and Symbiodinium C or D types, to assimilate dissolved inorganic carbon (via photosynthesis) and nitrogen (as ammonium). Our results indicate that Symbiodinium types from two clades naturally associated with I.?palifera possess different metabolic capabilities. The Symbiodinium C type fixed and passed significantly more carbon and nitrogen to its coral host than the D type. This study provides further insights into the metabolic plasticity among different Symbiodinium types in hospite and strengthens the evidence that the more temperature-tolerant Symbiodinium D type may be less metabolically beneficial for its coral host under non-stressful conditions.
Pulpitel, T., Pernice, M., Simpson, S.J. & Ponton, F. 2015, 'Tissue-Specific Immune Gene Expression in the Migratory Locust, Locusta Migratoria.', Insects, vol. 6, no. 2, pp. 368-380.View/Download from: UTS OPUS or Publisher's site
The ability of hosts to respond to infection involves several complex immune recognition pathways. Broadly conserved pathogen-associated molecular patterns (PAMPs) allow individuals to target a range of invading microbes. Recently, studies on insect innate immunity have found evidence that a single pathogen can activate different immune pathways across species. In this study, expression changes in immune genes encoding peptidoglycan-recognition protein SA (PGRP-SA), gram-negative binding protein 1 (GNBP1) and prophenoloxidase (ProPO) were investigated in Locusta migratoria, following an immune challenge using injected lipopolysaccharide (LPS) solution from Escherichia coli. Since immune activation might also be tissue-specific, gene expression levels were followed across a range of tissue types. For PGRP-SA, expression increased in response to LPS within all seven of the tissue-types assayed and differed significantly between tissues. Expression of GNBP1 similarly varied across tissue types, yet showed no clear expression difference between LPS-injected and uninfected locusts. Increases in ProPO expression in response to LPS, however, could only be detected in the gut sections. This study has revealed tissue-specific immune response to add a new level of complexity to insect immune studies. In addition to variation in recognition pathways identified in previous works, tissue-specificity should be carefully considered in similar works.
Schliep, M., Pernice, M., Sinutok, S., Bryant, C.V., York, P.H., Rasheed, M.A. & Ralph, P.J. 2015, 'Evaluation of Reference Genes for RT-qPCR Studies in the Seagrass Zostera muelleri Exposed to Light Limitation', SCIENTIFIC REPORTS, vol. 5.View/Download from: UTS OPUS or Publisher's site
Nielsen, D.A., Pernice, M., Schliep, M., Sablok, G., Jeffries, T.C., Kuehl, M., Wangpraseurt, D., Ralph, P.J. & Larkum, A.W.D. 2015, 'Microenvironment and phylogenetic diversity of Prochloron inhabiting the surface of crustose didemnid ascidians', ENVIRONMENTAL MICROBIOLOGY, vol. 17, no. 10, pp. 4121-4132.View/Download from: UTS OPUS or Publisher's site
Pernice, M. & Levy, O. 2014, 'Novel tools integrating metabolic and gene function to study the impact of the environment on coral symbiosis', Frontiers in Microbiology, vol. 5, pp. 1-6.View/Download from: UTS OPUS or Publisher's site
The symbiotic dinoflagellates (genus Symbiodinium) inhabiting coral endodermal tissues are well known for their role as keystone symbiotic partners, providing corals with enormous amounts of energy acquired via photosynthesis and the absorption of dissolved nutrients. In the past few decades, corals reefs worldwide have been increasingly affected by coral bleaching (i.e., the breakdown of the symbiosis between corals and their dinoflagellate symbionts), which carries important socio-economic implications. Consequently, the number of studies focusing on the molecular and cellular processes underlying this biological phenomenon has grown rapidly, and symbiosis is now widely recognized as a major topic in coral biology. However, obtaining a clear image of the interplay between the environment and this mutualistic symbiosis remains challenging. Here, we review the potential of recent technological advances in molecular biology and approaches using stable isotopes to fill critical knowledge gaps regarding coral symbiotic function. Finally, we emphasize that the largest opportunity to achieve the full potential in this field arises from the integration of these technological advances.
Pernice, M., Simpson, S. & Ponton, F. 2014, 'Towards an integrated understanding of gut microbiota using insects as model systems', Journal of Insect Physiology, vol. 69, pp. 12-18.View/Download from: UTS OPUS or Publisher's site
Metazoans form symbioses with microorganisms that synthesize essential nutritional compounds and increase their efficiency to digest and absorb nutrients. Despite the growing awareness that microbes within the gut play key roles in metabolism, health and development of metazoans, symbiotic relationships within the gut are far from fully understood. Insects, which generally harbor a lower microbial diversity than vertebrates, have recently emerged as potential model systems to study these interactions. In this review, we give a brief overview of the characteristics of the gut microbiota in insects in terms of low diversity but high variability at intra- and interspecific levels and we investigate some of the ecological and methodological factors that might explain such variability. We then emphasize how studies integrating an array of techniques and disciplines have the potential to provide new understanding of the biology of this micro eco-system.
Kopp, C., Pernice, M., Domart-Coulon, I., Djediat, C., Spangenberg, J.E., Alexander, D.T.L., Hignette, M., Meziane, T. & Meibom, A. 2013, 'Highly dynamic cellular-level response of symbiotic coral to a sudden increase in environmental nitrogen.', mBio, vol. 4, no. 3, pp. e00052-e00013.View/Download from: UTS OPUS or Publisher's site
UNLABELLED: Metabolic interactions with endosymbiotic photosynthetic dinoflagellate Symbiodinium spp. are fundamental to reef-building corals (Scleractinia) thriving in nutrient-poor tropical seas. Yet, detailed understanding at the single-cell level of nutrient assimilation, translocation, and utilization within this fundamental symbiosis is lacking. Using pulse-chase (15)N labeling and quantitative ion microprobe isotopic imaging (NanoSIMS; nanoscale secondary-ion mass spectrometry), we visualized these dynamic processes in tissues of the symbiotic coral Pocillopora damicornis at the subcellular level. Assimilation of ammonium, nitrate, and aspartic acid resulted in rapid incorporation of nitrogen into uric acid crystals (after ~45 min), forming temporary N storage sites within the dinoflagellate endosymbionts. Subsequent intracellular remobilization of this metabolite was accompanied by translocation of nitrogenous compounds to the coral host, starting at ~6 h. Within the coral tissue, nitrogen is utilized in specific cellular compartments in all four epithelia, including mucus chambers, Golgi bodies, and vesicles in calicoblastic cells. Our study shows how nitrogen-limited symbiotic corals take advantage of sudden changes in nitrogen availability; this opens new perspectives for functional studies of nutrient storage and remobilization in microbial symbioses in changing reef environments. IMPORTANCE: The methodology applied, combining transmission electron microscopy with nanoscale secondary-ion mass spectrometry (NanoSIMS) imaging of coral tissue labeled with stable isotope tracers, allows quantification and submicrometric localization of metabolic fluxes in an intact symbiosis. This study opens the way for investigations of physiological adaptations of symbiotic systems to nutrient availability and for increasing knowledge of global nitrogen and carbon biogeochemical cycling.
Dunn, S.R., Pernice, M., Green, K., Hoegh-Guldberg, O. & Dove, S.G. 2012, 'Thermal stress promotes host mitochondrial degradation in symbiotic cnidarians: are the batteries of the reef going to run out?', PloS one, vol. 7, no. 7, p. e39024.View/Download from: UTS OPUS or Publisher's site
The symbiotic relationship between cnidarians and their dinoflagellate symbionts, Symbiodinium spp, which underpins the formation of tropical coral reefs, can be destabilized by rapid changes to environmental conditions. Although some studies have concluded that a breakdown in the symbiosis begins with increased reactive oxygen species (ROS) generation within the symbiont due to a decoupling of photosynthesis, others have reported the release of viable symbionts via a variety of host cell derived mechanisms. We explored an alternative model focused upon changes in host cnidarian mitochondrial integrity in response to thermal stress. Mitochondria are often likened to being batteries of the cell, providing energy in the form of ATP, and controlling cellular pathway activation and ROS generation. The overall morphology of host mitochondria was compared to that of associated symbionts under an experimental thermal stress using confocal and electron microscopy. The results demonstrate that hyperthermic stress induces the degradation of cnidarian host mitochondria that is independent of symbiont cellular deterioration. The potential sites of host mitochondrial disruption were also assessed by measuring changes in the expression of genes associated with electron transport and ATP synthesis using quantitative RT-PCR. The primary site of degradation appeared to be downstream of complex III of the electron transport chain with a significant reduction in host cytochrome c and ATP synthase expression. The consequences of reduced expression could limit the capacity of the host to mitigate ROS generation and maintain both organelle integrity and cellular energy supplies. The disruption of host mitochondria, cellular homeostasis, and subsequent cell death irrespective of symbiont integrity highlights the importance of the host response to thermal stress and in symbiosis dysfunction that has substantial implications for understanding how coral reefs will survive in the face of c...
Pernice, M. & Boucher-Rodoni, R. 2012, 'Occurrence of a specific dual symbiosis in the excretory organ of geographically distant Nautiloids populations.', Environmental microbiology reports, vol. 4, no. 5, pp. 504-511.View/Download from: UTS OPUS or Publisher's site
Nautilus is one of the most intriguing of all sea creatures, sharing morphological similarities with the extinct forms of coiled cephalopods that evolved since the Cambrian (542-488mya). Further, bacterial symbioses found in their excretory organ are of particular interest as they provide a great opportunity to investigate the influence of host-microbe interactions upon the origin and evolution of an innovative nitrogen excretory system. To establish the potential of Nautilus excretory organ as a new symbiotic system, it is, however, necessary to assess the specificity of this symbiosis and whether it is consistent within the different species of present-day Nautiloids. By addressing the phylogeny and distribution of bacterial symbionts in three Nautilus populations separated by more than 6000km (N.pompilius from Philippines and Vanuatu, and N.macromphalus from New Caledonia), this study confirms the specificity of this dual symbiosis involving the presence of betaproteobacteria and spirochaete symbionts on a very wide geographical area. Overall, this work sheds further light on Nautiloids excretory organ as an innovative system of interaction between bacteria and cephalopods.
Pernice, M., Meibom, A., Van Den Heuvel, A., Kopp, C., Domart-Coulon, I., Hoegh-Guldberg, O. & Dove, S. 2012, 'A single-cell view of ammonium assimilation in coral-dinoflagellate symbiosis.', The ISME journal, vol. 6, no. 7, pp. 1314-1324.View/Download from: UTS OPUS or Publisher's site
Assimilation of inorganic nitrogen from nutrient-poor tropical seas is an essential challenge for the endosymbiosis between reef-building corals and dinoflagellates. Despite the clear evidence that reef-building corals can use ammonium as inorganic nitrogen source, the dynamics and precise roles of host and symbionts in this fundamental process remain unclear. Here, we combine high spatial resolution ion microprobe imaging (NanoSIMS) and pulse-chase isotopic labeling in order to track the dynamics of ammonium incorporation within the intact symbiosis between the reef-building coral Acropora aspera and its dinoflagellate symbionts. We demonstrate that both dinoflagellate and animal cells have the capacity to rapidly fix nitrogen from seawater enriched in ammonium (in less than one hour). Further, by establishing the relative strengths of the capability to assimilate nitrogen for each cell compartment, we infer that dinoflagellate symbionts can fix 14 to 23 times more nitrogen than their coral host cells in response to a sudden pulse of ammonium-enriched seawater. Given the importance of nitrogen in cell maintenance, growth and functioning, the capability to fix ammonium from seawater into the symbiotic system may be a key component of coral nutrition. Interestingly, this metabolic response appears to be triggered rapidly by episodic nitrogen availability. The methods and results presented in this study open up for the exploration of dynamics and spatial patterns associated with metabolic activities and nutritional interactions in a multitude of organisms that live in symbiotic relationships.
Pernice, M., Dunn, S.R., Miard, T., Dufour, S., Dove, S. & Hoegh-Guldberg, O. 2011, 'Regulation of apoptotic mediators reveals dynamic responses to thermal stress in the reef building coral Acropora millepora.', PloS one, vol. 6, no. 1, p. e16095.View/Download from: UTS OPUS or Publisher's site
Mass coral bleaching is increasing in scale and frequency across the world's coral reefs and is being driven primarily by increased levels of thermal stress arising from global warming. In order to understand the impacts of projected climate change upon corals reefs, it is important to elucidate the underlying cellular mechanisms that operate during coral bleaching and subsequent mortality. In this respect, increased apoptotic cell death activity is an important cellular process that is associated with the breakdown of the mutualistic symbiosis between the cnidarian host and their dinoflagellate symbionts.The PRESENT study reports the impacts of different stressors (colchicine and heat stress) on three phases of apoptosis: (i) the potential initiation by differential expression of Bcl-2 members, (ii) the execution of apoptotic events by activation of caspase 3-like proteases and (iii) and finally, the cell disposal indicated by DNA fragmentation in the reef building coral Acropora millepora. In corals incubated with colchicine, an increase in caspase 3-like activity and DNA fragmentation was associated with a relative down-regulation of Bcl-2, suggesting that the initiation of apoptosis may be mediated by the suppression of an anti-apoptotic mechanism. In contrast, in the early steps of heat stress, the induction of caspase-dependent apoptosis was related to a relative up-regulation of Bcl-2 consecutively followed by a delayed decrease in apoptosis activity.In the light of these results, we propose a model of heat stress in coral hosts whereby increasing temperatures engage activation of caspase 3-dependent apoptosis in cells designated for termination, but also the onset of a delayed protective response involving overexpression of Bcl-2 in surviving cells. This mitigating response to thermal stress could conceivably be an important regulatory mechanism for cell survival in corals exposed to sudden environmental changes.
Ponton, F., Chapuis, M.-.P., Pernice, M., Sword, G.A. & Simpson, S.J. 2011, 'Evaluation of potential reference genes for reverse transcription-qPCR studies of physiological responses in Drosophila melanogaster.', Journal of insect physiology, vol. 57, no. 6, pp. 840-850.View/Download from: UTS OPUS or Publisher's site
Drosophila melanogaster is one of the most important genetic models and techniques such as reverse transcription quantitative real-time PCR (RT-qPCR) are being employed extensively for deciphering the genetics basis of physiological functions. In RT-qPCR, the expression levels of target genes are estimated on the basis of endogenous controls. The purpose of these reference genes is to control for variations in RNA quantity and quality. Although determination of suitable reference genes is essential to RT-qPCR studies, reports on the evaluation of reference genes in D. melanogaster studies are lacking. We analyzed the expression levels of seven candidate reference genes (Actin, EF1, Mnf, Rps20, Rpl32, Tubulin and 18S) in flies that were injured, heat-stressed, or fed different diets. Statistical analyses of variation were determined using three established software programs for reference gene selection, geNorm, NormFinder and BestKeeper. Best-ranked references genes differed across the treatments. Normalization candidacy of the selected candidate reference genes was supported by an analysis of gene expression values obtained from microarray datasets available online. The differences between the experimental treatments suggest that assessing the stability of reference gene expression patterns, determining candidates and testing their suitability is required for each experimental investigation.
Rosic, N.N., Pernice, M., Dove, S., Dunn, S. & Hoegh-Guldberg, O. 2011, 'Gene expression profiles of cytosolic heat shock proteins Hsp70 and Hsp90 from symbiotic dinoflagellates in response to thermal stress: possible implications for coral bleaching', CELL STRESS & CHAPERONES, vol. 16, no. 1, pp. 69-80.View/Download from: UTS OPUS or Publisher's site
Rosic, N.N., Pernice, M., Rodriguez-Lanetty, M. & Hoegh-Guldberg, O. 2011, 'Validation of housekeeping genes for gene expression studies in Symbiodinium exposed to thermal and light stress.', Marine biotechnology (New York, N.Y.), vol. 13, no. 3, pp. 355-365.View/Download from: UTS OPUS or Publisher's site
Unicellular photosynthetic algae (dinoflagellate) from the genus Symbiodinium live in mutualistic symbiosis with reef-building corals. Cultured Symbiodinium sp. (clade C) were exposed to a range of environmental stresses that included elevated temperatures (29°C and 32°C) under high (100 mol quanta m(-2) s(-1) Photosynthetic Active Radiation) and low (10 mol quanta m(-2) s(-1)) irradiances. Using real-time RT-PCR the stability of expression for the nine selected putative housekeeping genes (HKGs) was tested. The most stable expression pattern was identified for cyclophilin and S-adenosyl methionine synthetase (SAM) followed by S4 ribosomal protein (Rp-S4), Calmodulin (Cal), and Cytochrome oxidase subunit 1 (Cox), respectively. Thermal stress alone resulted in the highest expression stability for Rp-S4 and SAM, with a minimum of two reference genes required for data normalization. For Symbiodinium exposed to both, light and thermal stresses, at least five reference genes were recommended by geNorm analysis. In parallel, the expression of Hsp90 for Symbiodinium in culture and in symbiosis within coral host (Acropora millepora) was evaluated using the most stable HKGs. Our results revealed a drop in Hsp90 expression after an 18 h-period and a 24 h-period of exposure to elevated temperatures indicating the similar Hsp90 expression profile in symbiotic and non-symbiotic environments. This study provides the first list of the HKGs and will provide a useful reference in future gene expression studies in symbiotic dinoflagellates.
Rosic, N.N., Pernice, M., Dunn, S., Dove, S. & Hoegh-Guldberg, O. 2010, 'Differential Regulation by Heat Stress of Novel Cytochrome P450 Genes from the Dinoflagellate Symbionts of Reef-Building Corals', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 76, no. 9, pp. 2823-2829.View/Download from: UTS OPUS or Publisher's site
Pernice, M., Boucher, J., Boucher-Rodoni, R., Joannot, P. & Bustamante, P. 2009, 'Comparative bioaccumulation of trace elements between Nautilus pompilius and Nautilus macromphalus (Cephalopoda: Nautiloidea) from Vanuatu and New Caledonia', ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY, vol. 72, no. 2, pp. 365-371.View/Download from: UTS OPUS or Publisher's site
Quevrain, E., Domart-Coulon, I., Pernice, M. & Bourguet-Kondracki, M.-.L. 2009, 'Novel natural parabens produced by a Microbulbifer bacterium in its calcareous sponge host Leuconia nivea', ENVIRONMENTAL MICROBIOLOGY, vol. 11, no. 6, pp. 1527-1539.View/Download from: UTS OPUS or Publisher's site
Pernice, M., Pichon, D., Domart-Coulon, I., Favet, J. & Boucher-Rodoni, R. 2007, 'Primary co-culture as a complementary approach to explore the diversity of bacterial associations in marine invertebrates: the example of Nautilus macromphalus (Cephalopoda : Nautiloidea)', MARINE BIOLOGY, vol. 150, no. 5, pp. 749-757.View/Download from: Publisher's site
Pernice, M., Wetzel, S., Gros, O., Boucher-Rodoni, R. & Dubilier, N. 2007, 'Enigmatic dual symbiosis in the excretory organ of Nautilus macromphalus (Cephalopoda : Nautiloidea)', PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, vol. 274, no. 1614, pp. 1143-1152.View/Download from: Publisher's site
Pernice, M., Destoumieux-Garzon, D., Peduzzi, J., Rebuffat, S. & Boucher-Rodoni, R. 2007, 'Identification of a Vibrio strain producing antimicrobial agents in the excretory organs of Nautilus pompilius (Cephalopoda : Nautiloidea)', REVIEWS IN FISH BIOLOGY AND FISHERIES, pp. 197-205.View/Download from: Publisher's site
New South Wales Department of Primary Industries, GE healthcare.