Toxicology of Gambierdiscus spp. (Dinophyceae) from Tropical and Temperate Australian Waters

Ciguatera Fish Poisoning (CFP) is a human illness caused by the consumption of marine fish contaminated with ciguatoxins (CTX) and possibly maitotoxins (MTX), produced by species from the benthic dinoflagellate genus Gambierdiscus. Here, we describe the identity and toxicology of Gambierdiscus spp. isolated from the tropical and temperate waters of eastern Australia. Based on newly cultured strains, we found that four Gambierdiscus species were present at the tropical location, including G. carpenteri, G. lapillus and two others which were not genetically identical to other currently described species within the genus, and may represent new species. Only G. carpenteri was identified from the temperate location. Using LC-MS/MS analysis we did not find any characterized microalgal CTXs (P-CTX-3B, P-CTX-3C, P-CTX-4A and P-CTX-4B) or MTX-1; however, putative maitotoxin-3 (MTX-3) was detected in all species except for the temperate population of G. carpenteri. Using the Ca2+ influx SH-SY5Y cell Fluorescent Imaging Plate Reader (FLIPR) bioassay we found CTX-like activity in extracts of the unidentified Gambierdiscus strains and trace level activity in strains of G. lapillus. While no detectable CTX-like activity was observed in tropical or temperate strains of G. carpenteri, all species showed strong maitotoxin-like activity. This study, which represents the most comprehensive analyses of the toxicology of Gambierdiscus strains isolated from Australia to date, suggests that CFP in this region may be caused by currently undescribed ciguatoxins and maitotoxins

Surface Immuno-Functionalisation for the Capture and Detection of <i>Vibrio</i> Species in the Marine Environment: A New Management Tool for Industrial Facilities

<div><p>Bacteria from the genus <i>Vibrio</i> are a common and environmentally important group of bacteria within coastal environments and include species pathogenic to aquaculture organisms. Their distribution and abundance are linked to specific environmental parameters, including temperature, salinity and nutrient enrichment. Accurate and efficient detection of Vibrios in environmental samples provides a potential important indicator of overall ecosystem health while also allowing rapid management responses for species pathogenic to humans or species implicated in disease of economically important aquacultured fish and invertebrates. In this study, we developed a surface immuno-functionalisation protocol, based on an avidin-biotin type covalent binding strategy, allowing specific sandwich-type detection of bacteria from the <i>Vibrio</i> genus. The assay was optimized on 12 diverse <i>Vibrio</i> strains, including species that have implications for aquaculture industries, reaching detection limits between 7×10³ to 3×10⁴ cells mL⁻¹. Current techniques for the detection of total Vibrios rely on laborious or inefficient analyses resulting in delayed management decisions. This work represents a novel approach for a rapid, accurate, sensitive and robust tool for quantifying Vibrios directly in industrial systems and in the environment, thereby facilitating rapid management responses.</p></div

Affinity of the different <i>Vibrio</i> strains and commercial positive control to the functionalised surface using optimised conditions.

<p>Absorbance signals obtained after a 30 min cell capture step on the functionalised surface and a 30 min detection step using a 1/1000 dilution of horseradish peroxidase anti-<i>Vibrio</i> antibody (HRP-α<i>Vib</i> Pab).</p

Comparison of the <i>Vibrio</i> counts obtained using both the TCBS plate culturing and ELISA detection method.

<p>Comparison of the <i>Vibrio</i> counts obtained using both the TCBS plate culturing and ELISA detection method.</p

Effect of the capture medium.

<p>Signals obtained for increasing <i>Vibrio parahaemolyticus</i> (dashed line) or <i>S. marcescens</i> (solid line) cell concentrations when carrying out the capture step either in PBS (▪), filtered (▴) or unfiltered (•) natural seawater.</p

Linear part of the ELISA standard curve.

<p>Absorbance values obtained for increasing <i>V. parahaemolyticus</i> cell concentrations ranging from 1×10⁴ to 1×10⁸ cells ml⁻¹.</p

LOD, IC50 and sensitivity values obtained for each <i>Vibrio</i> strain with or without functionalising the plate surface.

<p>LOD, IC50 and sensitivity values obtained for each <i>Vibrio</i> strain with or without functionalising the plate surface.</p

Live cell analysis at sea reveals divergent thermal performance between photosynthetic ocean microbial eukaryote populations

Experimentation at sea provides insight into which traits of ocean microbes are linked to performance in situ. Here we show distinct patterns in thermal tolerance of microbial phototrophs from adjacent water masses sampled in the south-west Pacific Ocean, determined using a fluorescent marker for reactive oxygen species (ROS). ROS content of pico-eukaryotes was assessed after 1, 5 and 25 h of incubation along a temperature gradient (15.6–32.1 °C). Pico-eukaryotes from the East Australian Current (EAC) had relatively constant ROS and showed greatest mortality after 25 h at 7 °C below ambient, whereas those from the Tasman Sea had elevated ROS in both warm and cool temperature extremes and greatest mortality at temperatures 6–10 °C above ambient, interpreted as the outcome of thermal stress. Tracking of water masses within an oceanographic circulation model showed populations had distinct thermal histories, with EAC pico-eukaryotes experiencing higher average temperatures for at least 1 week prior to sampling. While acclimatization and community assembly could both influence biological responses, this study clearly demonstrates that phenotypic divergence occurs along planktonic drift trajectories

Pharmacological inhibition of TBK1/IKKε blunts immunopathology in a murine model of SARS-CoV-2 infection

Abstract TANK-binding kinase 1 (TBK1) is a key signalling component in the production of type-I interferons, which have essential antiviral activities, including against SARS-CoV-2. TBK1, and its homologue IκB kinase-ε (IKKε), can also induce pro-inflammatory responses that contribute to pathogen clearance. While initially protective, sustained engagement of type-I interferons is associated with damaging hyper-inflammation found in severe COVID-19 patients. The contribution of TBK1/IKKε signalling to these responses is unknown. Here we find that the small molecule idronoxil inhibits TBK1/IKKε signalling through destabilisation of TBK1/IKKε protein complexes. Treatment with idronoxil, or the small molecule inhibitor MRT67307, suppresses TBK1/IKKε signalling and attenuates cellular and molecular lung inflammation in SARS-CoV-2-challenged mice. Our findings additionally demonstrate that engagement of STING is not the major driver of these inflammatory responses and establish a critical role for TBK1/IKKε signalling in SARS-CoV-2 hyper-inflammation