Browsing by Author "Loo TS"

Now showing 1 - 5 of 5
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    Apoplastic effector candidates of a foliar forest pathogen trigger cell death in host and non-host plants
    (2021-08-09) Hunziker L; Tarallo M; Gough K; Guo M; Hargreaves C; Loo TS; McDougal RL; Mesarich CH; Bradshaw RE
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    Apoplastic effector candidates of a foliar forest pathogen trigger cell death in host and non-host plants.
    (7/10/2021) Hunziker L; Tarallo M; Gough K; Guo M; Hargreaves C; Loo TS; McDougal RL; Mesarich CH; Bradshaw RE
    Forests are under threat from pests, pathogens, and changing climate. A major forest pathogen worldwide is the hemibiotroph Dothistroma septosporum, which causes dothistroma needle blight (DNB) of pines. While D. septosporum uses effector proteins to facilitate host infection, it is currently unclear whether any of these effectors are recognised by immune receptors to activate the host immune system. Such information is needed to identify and select disease resistance against D. septosporum in pines. We predicted and investigated apoplastic D. septosporum candidate effectors (DsCEs) using bioinformatics and plant-based experiments. We discovered DsCEs that trigger cell death in the angiosperm Nicotiana spp., indicative of a hypersensitive defence response and suggesting their recognition by immune receptors in non-host plants. In a first for foliar forest pathogens, we developed a novel protein infiltration method to show that tissue-cultured pine shoots can respond with a cell death response to a DsCE, as well as to a reference cell death-inducing protein. The conservation of responses across plant taxa suggests that knowledge of pathogen-angiosperm interactions may also be relevant to pathogen-gymnosperm interactions. These results contribute to our understanding of forest pathogens and may ultimately provide clues to disease immunity in both commercial and natural forests.
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    Emetic toxin production of Bacillus cereus in a biofilm
    (Elsevier Ltd, 2022-01-15) Huang Y; Flint SH; Loo TS; Palmer JS
    Bacillus cereus sensu stricto (B. cereus) belongs to the B. cereus group, and is a well-known foodborne pathogen causing human disease including emesis which is caused by an emetic toxin, cereulide, with 105-108 cells per gram required to cause disease. The presence of this highly heat, pH and protease-resistant toxin presents a serious challenge to the food industry, as the bacteria itself may be eliminated during processing but the cereulide toxin will survive most food processing techniques. This study shows that cereulide toxin is associated with cells and biofilm structures rather than suspended in the surrounding liquid phase or environment. This is the first report investigating the cereulide toxin production in the presence of biofilms of B. cereus, showing that the cereulide toxin produced is associated with biofilm complex and also attaches to the substrate such as glass and stainless-steel on which the biofilm grows. The RT-qPCR showed that the expression of cesA and cesB were comparable between planktonic cells and biofilms. This study contributes a better understanding of food safety issues in the industry caused by cereulide toxin produced by B. cereus, and provides valuable information for developing control methods for cereulide toxin in the food industry.
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    Fibrillisation of faba bean protein isolate by thermosonication for process efficacy: Microstructural characteristics, assembly behaviour, and physicochemical properties
    (Elsevier Ltd, 2024-09) Hu Y; Cheng L; Gilbert EP; Loo TS; Lee SJ; Harrison J; Yang Z
    The effect of thermosonication (TS) (90 °C, 10–30 min) on the fibrillisation of faba bean protein isolate (FPI) was studied. The self-assembly behaviour, microstructural characteristics and techno-functional (gelation and emulsification) properties of FPI fibrils obtained from TS treatment were compared with those obtained from conventional prolonged heating (CH) at 90 °C up to 8 h. Compared to CH treatment, TS treatment was shown to significantly accelerate the formation of FPI fibrils with prominent β-sheet structures as revealed by Thioflavin T (ThT) fluorescence, Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD). The characteristics of fibril building blocks were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography linked to tandem mass spectrometry (LC-MS/MS) to obtain the differences between TS and CH induced fibrillisation of FPI. Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) showed that 4 h CH and 10 min TS treatments resulted in the fibrils with similar radius (from 5 to 10 nm). Furthermore, SANS indicated that TS treatment induced the formation of an entangled FPI fibrillar network, which could lead to the observed viscoelastic properties of FPI at a high concentration (10 wt%). Finally, high internal phase O/W emulsions (HIPE, φ = 0.75) stabilised by 30 min TS induced FPI fibrils (3 wt%) demonstrated a stronger gel strength and smaller oil droplet size compared to those prepared with untreated FPI, suggesting a superior emulsification capability of FPI fibrils. This finding demonstrates that TS treatment is a promising and efficient method for fibrillisation of plant proteins with the resultant fibrils generating excellent gelation and emulsification properties.
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    The impact of heating and drying on protease activities of ruminant milk before and after in vitro infant digestion
    (Elsevier Ltd, 2023-12-15) Leite JAS; Montoya CA; Loveday SM; Mullaney JA; Loo TS; McNabb WC; Roy NC
    This study investigated the effect of heating (63°C/30 min or 75°C/15 s) and drying (spray-drying or freeze-drying) on plasmin, cathepsin D, and elastase activities in bovine, ovine, and caprine milk, compared to non-dried raw milk counterparts. Protease activities and protein hydrolysis were assessed before and after in vitro infant digestion with or without gastric and pancreatic enzymes. At 75°C/15 s, plasmin activity in caprine and ovine milk decreased (69-75%, p<0.05), while cathepsin D activity in spray-dried bovine milk heated increased (2.8-fold, p<0.05). Plasmin and cathepsin D activities increased (<1.2-fold, p<0.05) after in vitro digestion with pancreatin, regardless of milk species. Endogenous milk enzymes hydrolyzed more proteins than gastric enzymes during gastric digestion and contributed to small intestinal digestion. In summary, milk proteases remained active after processing with effects dependent on the species of milk, and they contributed to in vitro protein hydrolysis in the stomach and small intestine.