The interindividual variation in the sensitivity to bitterness is attributed in part to genetic polymorphism at the taste receptor level, but other factors, such as saliva composition, might be involved. In order to investigate this, 2 groups of subjects (hyposensitive, hypersensitive) were selected from 29 healthy male volunteers based on their detection thresholds for caffeine, and their salivary proteome composition was compared. Abundance of 26 of the 255 spots detected on saliva electrophoretic patterns was significantly different between hypo- and hypersensitive subjects. Saliva of hypersensitive subjects contained higher levels of amylase fragments, immunoglobulins, and serum albumin and/or serum albumin fragments. It also contained lower levels of cystatin SN, an inhibitor of protease. The results suggest that proteolysis occurring within the oral cavity is an important perireceptor factor associated to the sensitivity to the bitter taste of caffeine.

Conventional identification (CI) of yeasts is based on morphological, biochemical and/or immunological methods. Matrix-assisted laser desorption/ionization - time of flight (MALDI-TOF or MT-MS) mass spectrometry has been proposed as a new method for the identification of microorganisms. This prospective study compared the performance of MT-MS and CI for the identification of yeasts isolated from clinical samples. Sequencing of the internal transcribed spacer (ITS) regions of ribosomal DNA was used as the reference method in the analysis of a total of 1207 yeast isolates. Concordance between MT-MS and CI was observed for 1105 isolates (91.5%), while 74 isolates (6.1%) were misidentified. Molecular identification revealed that 73 of these 74 isolates were identified correctly by MT-MS and CI correctly identified the last one. Concordance between the two techniques was excellent for the medically-important species (98-100%), including the identification of closely-related species (Candida albicans/C. dubliniensis; C. inconspicua/C. norvegensis; C. parapsilosis/C. metapsilosis/C. orthopsilosis). Only 2.3% of isolates belonging to C. famata, C. lambica and C. magnoliae or to Geotrichum spp. and Trichosporon spp. were not identified by MT-MS. This investigation highlights the potential of MT-MS-based yeast identification as a reliable, time and cost-efficient alternative to CI.

saliva protein composition may contribute to bitter taste acceptance in the younger infants.

-Genetic variation has been assessed in 73 (mostly French) populations of the wild service tree (Sorbus torminalis) using 15 isozymes loci. In spite of a relatively high coefficient of genetic differentiation among populations (F ST = 15%), only a weak geographical structure was detected. This may be explained by the small size and young age of the populations due to the importance of founder effects, combined with the high levels of seed flow among populations. These features are typical of species characterised by metapopulation dynamics.genetic diversity / differentiation / metapopulation / Rosaceae / spatial structure Résumé -Variabilité génétique d'une espèce forestière disséminée : Sorbus torminalis L. (Crantz). De nombreuses études se sont intéressées à la diversité génétique des plantes rares, menacées de disparition, ou à celles largement répandues qui présentent un grand intérêt économique. Par contre, le cas des espèces ayant une aire de répartition importante mais présentant des densités faibles reste peu abordé, en particulier chez les arbres forestiers. Dans les forêts tempérées, les arbres forestiers disséminés occupent une place secondaire. L'alisier torminal (Sorbus torminalis) est une espèce fruitière disséminée au comportement post-pionnier nomade. Ses graines sont dispersées par les oiseaux. 67 populations françaises et 6 populations d'Europe centrale ont été étudiées à l'aide des isozymes. Une forte différentiation entre populations a été trouvée (F ST = 15 %), combinée à une faible structuration géographique. Ceci peut s'expliquer par les effets de fondation importants liés au comportement écologique de l'espèce, et aux flux de graines entre populations éloignées, liés à la dissémination par des oiseaux. Le modèle en métapopulation, avec des populations subissant des phé-nomènes de colonisation et d'extinction, mais restant interconnectées par des flux de gènes, semble particulièrement bien s'appliquer à cette espèce. Au vu de ces résultats, une gestion permettant l'implantation de l'alisier dans de nouveaux sites pouvant recevoir des flux de gènes des populations préexistantes doit être encouragée.Rosaceae / diversité génétique / métapopulation / differentiation / structure spatiale

Saliva is a biological fluid playing numerous roles in the oral cavity and increasingly considered as a source of markers. The role of saliva in sensory perception has been known for years but it is only recently that its potential role in oral fatty acids (FA) perception has been suggested. The aim of the present work was to study the relationships between taste sensitivity to oleic acid and the salivary proteome (2D electrophoresis) and metabolome (H-1 NMR). This was achieved by comparing saliva from two groups of subjects, highly (sensitive+) and weakly sensitive (sensitive-) to the taste of oleic acid. Partial least squares-discriminant analyses (PLS-DA) were used to model the relationship between sensitivity to C18:1, and the proteome and metabolome data. The two groups could be discriminated by ten spots. In particular, cystatin SN, cystatin D, zinc-alpha-2-glycoprotein and carbonic anhydrase 6 were overexpressed in the sensitive+ group. The latter result was confirmed by ELISA. The overexpression of these proteins, which have been associated to taste perception, supports the argument that C18: 1 is perceived by the taste system. The two groups could also be discriminated on the basis of eight metabolites, with FA, FA/proline, lysine and FA/pyruvate overexpressed in the sensitive+ group and acetate, leucine/isoleucine and butyrate overexpressed in the sensitive-group. The overexpression of these metabolites suggests a higher bacterial load in this group which could be implicated in perception of FAs