Quantitative metabolomics based on gas chromatography mass spectrometry: status and perspectives

Metabolomics involves the unbiased quantitative and qualitative analysis of the complete set of metabolites present in cells, body fluids and tissues (the metabolome). By analyzing differences between metabolomes using biostatistics (multivariate data analysis; pattern recognition), metabolites relevant to a specific phenotypic characteristic can be identified. However, the reliability of the analytical data is a prerequisite for correct biological interpretation in metabolomics analysis. In this review the challenges in quantitative metabolomics analysis with regards to analytical as well as data preprocessing steps are discussed. Recommendations are given on how to optimize and validate comprehensive silylation-based methods from sample extraction and derivatization up to data preprocessing and how to perform quality control during metabolomics studies. The current state of method validation and data preprocessing methods used in published literature are discussed and a perspective on the future research necessary to obtain accurate quantitative data from comprehensive GC-MS data is provided

Can volatile organic metabolites be used to simultaneously assess microbial and mite contamination level in cereal grains and coffee beans?

A novel approach based on headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-ToFMS) was developed for the simultaneous screening of microbial and mite contamination level in cereals and coffee beans. The proposed approach emerges as a powerful tool for the rapid assessment of the microbial contamination level (ca. 70 min versus ca. 72 to 120 h for bacteria and fungi, respectively, using conventional plate counts), and mite contamination (ca. 70 min versus ca. 24 h). A full-factorial design was performed for optimization of the SPME experimental parameters. The methodology was applied to three types of rice (rough, brown, and white rice), oat, wheat, and green and roasted coffee beans. Simultaneously, microbiological analysis of the samples (total aerobic microorganisms, moulds, and yeasts) was performed by conventional plate counts. A set of 54 volatile markers was selected among all the compounds detected by GC×GC-ToFMS. Principal Component Analysis (PCA) was applied in order to establish a relationship between potential volatile markers and the level of microbial contamination. Methylbenzene, 3-octanone, 2-nonanone, 2-methyl-3-pentanol, 1-octen-3-ol, and 2-hexanone were associated to samples with higher microbial contamination level, especially in rough rice. Moreover, oat exhibited a high GC peak area of 2-hydroxy-6-methylbenzaldehyde, a sexual and alarm pheromone for adult mites, which in the other matrices appeared as a trace component. The number of mites detected in oat grains was correlated to the GC peak area of the pheromone. The HS-SPME/GC×GC-ToFMS methodology can be regarded as the basis for the development of a rapid and versatile method that can be applied in industry to the simultaneous assessment the level of microbiological contamination and for detection of mites in cereals grains and coffee beans

The spawning migrations of an exploited Albulid in the tropical Pacific: implications for conservation and community-based management

International audienceTeleost fish that form predictable spawning aggregations and undertake reproductive migrations can be particularly vulnerable to overexploitation. To support community-based management of an artisanal fishery that targets bonefish (Albula glossodonta) spawning aggregations, we used a combination of acoustic telemetry, biological sampling, and remote imagery to reveal the spatiotemporal spawning migrations of bonefish on Anaa Atoll in the Tuamotu Archipelago, French Polynesia. The spawning migrations of bonefish tracked with acoustic telemetry were restricted to the northern section of the atoll, with 99.6% of all detections at offshore spawning habitats occurring on fixed acoustic receivers adjacent to the atoll’s artisanal fish trap complex. Male bonefish undertook spawning migrations more frequently than females and these spawning migrations were common during the Austral winter and fall. The movements of bonefish spawning aggregations coincided with the lunar cycle, as a network analysis revealed an increase in network size and the diversity of habitat use within our acoustic array throughout the duration of the waning moon. Our results highlighted the need for the management of the artisanal trap fishery to prevent the overharvest of bonefish during their peak spawning periods. In response to the spatiotemporal management recommendations derived from this research, the local government established an Educational Managed Marine Area that includes the atoll’s bonefish spawning migratory corridor adjacent to Tukuhora village and a Rahui (i.e., seasonal closure) to improve the sustainability of the fishery