Philippe Veisseire

Bio: Philippe Veisseire is an academic researcher from University of Auvergne. The author has contributed to research in topics: Lactobacillus rhamnosus & Candida albicans. The author has an hindex of 8, co-authored 17 publications receiving 491 citations.

Effects of zinc and influence of Acremonium lolii on growth parameters, chlorophyll a fluorescence and antioxidant enzyme activities of ryegrass ( Lolium perenne L. cv Apollo)

Abstract: The effects of zinc on growth, mineral content, chlorophyll a fluorescence, and detoxifying enzyme activity (ascorbate peroxidase (APX), EC 1.11.1.11; superoxide dismutase (SOD), EC 1.15.1.1) of ryegrass infected or not by Acremonium lolii, and treated with nutrient solution containing 0-50 mM ZnSO(4) were studied. The introduction of zinc induces stress with a decrease in growth at 1, 5 and 10 mM ZnSO(4) and a cessation of growth at 50 mM ZnSO(4), in ryegrass plants infected by A. lolii or not. This decrease in growth may be due to an accumulation of zinc in leaves. Nevertheless, symbiotic plants showed higher values in tiller number, an advantage conferred by the fungus. After 24 d of Zn exposure, leaf fresh weights and leaf water content were lower in plants growing with Zn in the culture medium and no advantage was conferred by the fungus to its host. An increase in Zn supply resulted in a decrease of the Ca, K, Mg, and Cu content of the leaves, a reduction in the quantum yield of electron flow throughout photosystem II (DeltaF/F(1)(m))and a lowering of the efficiency of photosynthetic energy conversion (F(v)/F(m)), compared to control plants. To counter this zinc stress, detoxifying enzymes APX and SOD increased (100%) when Zn reached the value of 50 mM in the nutrient solution. At 10 mM ZnSO(4), the presence of the fungus in the plant led to an increase in the threshold toxicity of plants to zinc by a diminution of APX activity.

Cow Teat Skin, a Potential Source of Diverse Microbial Populations for Cheese Production

Abstract: The diversity of the microbial community on cow teat skin was evaluated using a culture-dependent method based on the use of different dairy-specific media, followed by the identification of isolates by 16S rRNA gene sequencing. This was combined with a direct molecular approach by cloning and 16S rRNA gene sequencing. This study highlighted the large diversity of the bacterial community that may be found on teat skin, where 79.8% of clones corresponded to various unidentified species as well as 66 identified species, mainly belonging to those commonly found in raw milk (Enterococcus, Pediococcus, Enterobacter, Pantoea, Aerococcus, and Staphylococcus). Several of them, such as nonstarter lactic acid bacteria (NSLAB), Staphylococcus, and Actinobacteria, may contribute to the development of the sensory characteristics of cheese during ripening. Therefore, teat skin could be an interesting source or vector of biodiversity for milk. Variations of microbial counts and diversity between the farms studied have been observed. Moreover, Staphylococcus auricularis, Staphylococcus devriesei, Staphylococcus arlettae, Streptococcus bovis, Streptococcus equinus, Clavibacter michiganensis, Coprococcus catus, or Arthrobacter gandavensis commensal bacteria of teat skin and teat canal, as well as human skin, are not common in milk, suggesting that there is a breakdown of microbial flow from animal to milk. It would then be interesting to thoroughly study this microbial flow from teat to milk.

Environmental Toxicity and Antimicrobial Efficiency of Titanium Dioxide Nanoparticles in Suspension

Abstract: The aim of this work was to evaluate the photokilling efficiency of synthesized titanium dioxide nanoparticles in suspension. Two strains of Escherichia coli, Lactobacillus casei rhamnosus and Staphylococcus aureus were used as probes to test the photokilling activities of the nanoparticles. The toxicity effects of TiO 2 nanoparticles on the environment were determined by a standard test using gram-negative bioluminescent bacteria Vibrio fischeri. The antimicrobial activity of these nanoparticles (NPs) was then investigated versus NPs concentration, UV irradiation time and mi-cro-organism strains. We evaluated the LC50 values of the nanoparticles suspension by counting the Colony-Forming Units. Results highlighted the differences in bacteria sensitivity facing photo-killing treatment induced by the irradiation of anatase TiO 2 nanoparticles suspension. At the concentration of 1 g·L −1 TiO 2 , tested bacteria were killed after 30 minutes of photo-treatment. Using different TiO 2 concentrations, the Staphylococcus aureus gram-positive/catalase-positive bacteria were more resistant than gram-negative/catalase-positive ones or gram-positive/catalase-negative bacteria. An effect of UV irradiation was evaluated by the quantification of hydrogen peroxide generated by the photolysis of water molecules in presence of the nanoparticles with or without the most resistant bacterium (S. aureus). After 30 minutes with UV irradiation in these two conditions , the concentration of hydrogen peroxide was 35 µM in presence of 1.2 g·L −1 TiO 2 suspension. This result suggested that the resistance mechanism of S. aureus was not due to an extracelullar H 2 O 2 enzymatic degradation.

Zinc in plants

Abstract: Zinc (Zn) is an essential component of thousands of proteins in plants, although it is toxic in excess. In this review, the dominant fluxes of Zn in the soil-root-shoot continuum are described, including Zn inputs to soils, the plant availability of soluble Zn(2+) at the root surface, and plant uptake and accumulation of Zn. Knowledge of these fluxes can inform agronomic and genetic strategies to address the widespread problem of Zn-limited crop growth. Substantial within-species genetic variation in Zn composition is being used to alleviate human dietary Zn deficiencies through biofortification. Intriguingly, a meta-analysis of data from an extensive literature survey indicates that a small proportion of the genetic variation in shoot Zn concentration can be attributed to evolutionary processes whose effects manifest above the family level. Remarkable insights into the evolutionary potential of plants to respond to elevated soil Zn have recently been made through detailed anatomical, physiological, chemical, genetic and molecular characterizations of the brassicaceous Zn hyperaccumulators Thlaspi caerulescens and Arabidopsis halleri.

Heavy Metal Polluted Soils: Effect on Plants and Bioremediation Methods

Abstract: Soils polluted with heavy metals have become common across the globe due to increase in geologic and anthropogenic activities. Plants growing on these soils show a reduction in growth, performance, and yield. Bioremediation is an effective method of treating heavy metal polluted soils. It is a widely accepted method that is mostly carried out in situ; hence it is suitable for the establishment/reestablishment of crops on treated soils. Microorganisms and plants employ different mechanisms for the bioremediation of polluted soils. Using plants for the treatment of polluted soils is a more common approach in the bioremediation of heavy metal polluted soils. Combining both microorganisms and plants is an approach to bioremediation that ensures a more efficient clean-up of heavy metal polluted soils. However, success of this approach largely depends on the species of organisms involved in the process.

Symbioses of grasses with seedborne fungal endophytes

Abstract: Grasses (family Poaceae) and fungi of the family Clavicipitaceae have a long history of symbiosis ranging in a continuum from mutualisms to antagonisms. This continuum is particularly evident among symbioses involving the fungal genus Epichloe (asexual forms = Neotyphodium spp.). In the more mutualistic symbiota, the epichloe endophytes are vertically transmitted via host seeds, and in the more antagonistic symbiota they spread contagiously and suppress host seed set. The endophytes gain shelter, nutrition, and dissemination via host propagules, and can contribute an array of host fitness enhancements including protection against insect and vertebrate herbivores and root nematodes, enhancements of drought tolerance and nutrient status, and improved growth particularly of the root. In some systems, such as the tall fescue N. coenophialum symbioses, the plant may depend on the endophyte under many natural conditions. Recent advances in endophyte molecular biology promise to shed light on the mechanisms of the symbioses and host benefits.