Platforms to differentiate exotic pathovars of plant bacteria

Many of the EPPs that pose the biggest threat to the biosecurity of Australia’s plant industries are bacterial, but difficulties in identification to the subspecific or ‘ pathovar ’ level can seriously delay incursion management and affect market access. Pathovars are defined by host specificity so bio assays remain the definitive means of identification, but these require high level physical containment and can be slow and subjective , delaying diagnosis . Some pathovar - specific serological and molecular tests are available but better diagnostic methods are often required. This project used proteomics and metabolomics, platforms that identify functional molecules potentially associated with plant - pathogen interactions, to identify biomarkers that differentiate pathovars in species of Xanthomonas . Membrane - associated proteins from a collection of bacterial isolates were compared on 2Dimensional gels. Proteins that were found to be differentially expressed between distinct pathovars may be important modulators of host specificity so they were identified and the genes that encode them located by reference to genomic sequences . DNA - based assays targeting these genes were designed and validated for their specificity to the pathovar level . We have developed two new assays that provide levels of specificity not reported elsewhere in the literature. These assays specifically target the bacteria causing the different forms of citrus canker, but without cross - reaction to the closely - related organisms causing bacterial blight on cotton and Citrus Bacterial Spot. The molecular assays will be incorporated into the National Diagnostic Protocol for citrus canker through the SPHDS process. The metabolomics component has analysed metabolite expression in selected bacterial pathovars. Results showed separation between the different pathovars based on differential levels of expression of particular metabolites. These metabolites may be important determinants of pathogenicity. Neither proteomics nor metabolomics had been implemented before in the study of phytopathogenic bacteria and whilst both proved to be technically demanding, each delivered new biomarkers that differentiate phytopathogenic bacteria to a subspecific level . This confirmed the viability of these approaches as platforms to discover novel diagnostic targets. The new methods developed will be implemented into the national incursion response capability , improving the specificity of diagnostic testing available and reducing the possibility of false positive diagnosis . The project has fostered new collaborative partnerships both nationally (NSW, Victoria, WA) and internationally (to Thailand and the USA). The next phase of this work will provide a strong start - up project to the Plant Biosecurity Cooperative Research Centre ( PBCRC ) . This project has directly enhanced the plant bacteriology capacity of NSW and Australia trough the recruitment and training of science professionals and an undergraduate student , and supported the specialist training of a Thai scientist through allied project CRC20093

Sensory attributes of wine influenced by variety and berry shading discriminated by NMR metabolomics

Sensory analysis of wine is expensive and time consuming. Alternatives to characterise aspects of wine flavour and aroma are thus highly desirable. Here, it can be demonstrated that certain mouth-feel parameters identified from sensory analysis can be strongly correlated to NMR-based metabolomics analysis of wine. Wines were made from Cabernet Sauvignon and Shiraz grapes (Vitis vinifera L.) subjected to different levels of sun exposure in a commercial vineyard in the Sunraysia region of Victoria, Australia. Descriptive analysis revealed that the wines from the shaded treatment were significantly different from other treatments for a number of flavour and aroma characters, particularly those related to mouth-feel. Metabolomic analysis allowed classification of the wines based on grape variety and shade treatment in a manner similar to that by sensory analysis. The NMR analysis described here is rapid, inexpensive and allows the simultaneous assessment of multiple metabolites contributing to wine quality. Metabolomic analysis of wine may therefore offer a more affordable technique to investigate certain sensory aspects of wine.Simone Rochfort, Vilnis Ezernieks, Susan E.P. Bastian and Mark O. Downeyhttp://www.elsevier.com/wps/find/journaldescription.cws_home/405857/description#descriptio

Heat Stress in Dairy Cattle Alters Lipid Composition of Milk.

Heat stress, potentially affecting both the health of animals and the yield and composition of milk, occurs frequently in tropical, sub-tropical and temperate regions. A simulated acute heat stress experiment was conducted in controlled-climate chambers and milk samples collected before, during and after the heat challenge. Milk lipid composition, surveyed using LC-MS, showed significant changes in triacylglycerol (TAG) and polar lipid profiles. Heat stress (temperature-humidity index up to 84) was associated with a reduction in TAG groups containing short- and medium-chain fatty acids and a concomitant increase in those containing long-chain fatty acids. The abundance of five polar lipid classes including phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, lysophosphatidylcholine and glucosylceramide, was found to be significantly reduced during heat stress. Lysophosphatidylcholine, showing the greatest reduction in concentration, also displayed a differential response between heat tolerant and heat susceptible cows during heat stress. This phospholipid could be used as a heat stress biomarker for dairy cattle. Changes in TAG profile caused by heat stress are expected to modify the physical properties of milk fat, whereas the reduction of phospholipids may affect the nutritional value of milk. The results are discussed in relation to animal metabolism adaptation in the event of acute heat stress