Adaptive strategies of carbon transformation amongst coral symbionts (Symbiodiniaceae)

University of Technology Sydney. Faculty of Science.Algal endosymbionts (family Symbiodiniaceae) fuel the metabolism of reef-forming corals through uptake and utilisation of inorganic carbon (Ci) from photosynthesis. Changes in photosynthetic performance both within, and between endosymbiont taxa influence the extent of organic carbon ultimately translocated to the host coral. However, how such changes are regulated by plasticity in light harvesting, versus Ci assimilation processes remains unknown. In this thesis, I therefore built on novel approaches to assess functional diversity of fitness traits across Symbiodiniaceae to identify the extent with which Ci-uptake and incorporation differed amongst taxa and the extent with which differences could be reconciled against evolutionary adaptation across the family to sustain reef functioning in response to climate change. This thesis focused on direct assessment of Ci-uptake, and how it is linked to light harvesting and utilisation by Symbiodiniaceae both (in culture) and (in symbiosis with their host). I first cultured a broad range of Symbiodiniaceae taxa to assess how Ci was invested into cellular uptake, excretion, and growth; and how these metrics changed when three isolates of different thermal tolerances were subjected to sub-optimal conditions of growth. I further examined how these different thermo-tolerant Symbiodiniaceae coped with a stress-inducing increase of temperature. In parallel with photophysiology and Ci-uptake rate measurements, transcriptomics were carried out to resolve the underlying molecular network driving physiological response to heat stress. Finally, I extended this laboratory-based approach to examine Ci-uptake performance of natural coral communities across complex environmental gradients (mangrove vs. reef corals) on the Great Barrier Reef to resolve the adaptations of symbionts linked to their survival to extreme environments. My results revealed that environmental regulation outweighed evolutionary adaptation of Symbiodiniaceae in their capacity for Ci-uptake, suggesting that their ecological success predominantly relies on plasticity of upstream photosynthetic processes (efficiency of light-harvesting and non-photochemical energy quenching) rather than those downstream (Ci-uptake, assimilation, and excretion). Despite exhibiting similar trends in functional gene expression, each studied Symbiodiniaceae isolate exhibited different photophysiology and Ci-uptake rates in response to thermal stress for both (previously well studied) light reactions and dark reactions of photosynthesis. When in symbiosis, flexibility in the major Symbiodiniaceae taxa between reef and mangrove corals was associated with a reduced Ci incorporation in mangrove corals compared to reef corals. Together, these results will serve as a stepping stone to future research on the long term, aiming to improve worldwide reef health in response to global climate change

Colorimetric Detection of Caspase 3 Activity and Reactive Oxygen Derivatives: Potential Early Indicators of Thermal Stress in Corals

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

Phylogenetic ctDNA analysis depicts early-stage lung cancer evolution.

The early detection of relapse following primary surgery for non-small-cell lung cancer and the characterization of emerging subclones, which seed metastatic sites, might offer new therapeutic approaches for limiting tumour recurrence. The ability to track the evolutionary dynamics of early-stage lung cancer non-invasively in circulating tumour DNA (ctDNA) has not yet been demonstrated. Here we use a tumour-specific phylogenetic approach to profile the ctDNA of the first 100 TRACERx (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy (Rx)) study participants, including one patient who was also recruited to the PEACE (Posthumous Evaluation of Advanced Cancer Environment) post-mortem study. We identify independent predictors of ctDNA release and analyse the tumour-volume detection limit. Through blinded profiling of postoperative plasma, we observe evidence of adjuvant chemotherapy resistance and identify patients who are very likely to experience recurrence of their lung cancer. Finally, we show that phylogenetic ctDNA profiling tracks the subclonal nature of lung cancer relapse and metastasis, providing a new approach for ctDNA-driven therapeutic studies

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries