Joëlle Dupont

Comparison of the fuel oil biodegradation potential of hydrocarbon-assimilating microorganisms isolated from a temperate agricultural soil

Strains of hydrocarbon-degrading microorganisms (bacteria and fungi) were isolated from an agricultural soil in France. In a field, a portion was treated with oily cuttings resulting from the drilling of an onshore well. The cuttings which were spread at the rate of 600 g HC m-2 contained 10% of fuel oil hydrocarbons (HC). Another part of the field was left untreated. Three months after HC spreading, HC adapted bacteria and fungi were isolated at different soil depths in the two plots and identified. The biodegradation potential of the isolated strains was monitored by measuring the degradation rate of total HC, saturated hydrocarbons, aromatic hydrocarbons and resins of the fuel. Bacteria of the genera Pseudomonas, Brevundimonas Sphingomonas, Acinetobacter, Rhodococcus, Arthrobacter, Corynebacterium and fungi belonging to Aspergillus, Penicillium, Beauveria, Acremonium, Cladosporium, Fusarium, and Trichoderma were identified. The most active strains in the assimilation of saturates and aromatics were Arthrobacter sp., Sphingomonas spiritivorum, Acinetobacter baumanii, Beauveria alba and Penicillum simplicissimum. The biodegradation potential of the hydrocarbon utilizing microorganisms isolated from polluted or unpolluted soils were similar. In laboratory pure cultures, saturated HC were more degraded than aromatic HC, whereas resins were resistant to microbial attack. On an average, individual bacterial strains were more active than fungi in HC biodegradation.

Botrytis pseudocinerea, a new cryptic species causing gray mold in French vineyards in sympatry with Botrytis cinerea.

Botrytis cinerea is a major crop pathogen infesting >220 hosts worldwide. A cryptic species has been identified in some French populations but the new species, B. pseudocinerea, has not been fully delimited and established. The aim of this study was to distinguish between the two species, using phylogenetic, biological, morphological, and ecological criteria. Multiple gene genealogies confirmed that the two species belonged to different, well-supported phylogenetic clades. None of the morphological criteria tested (spore size, germination rate, or mycelial growth) was able to discriminate between these two species. Sexual crosses between individuals from the same species and different species were carried out. Only crosses between individuals from the same species were successful. Moreover, population genetics analysis revealed a high level of diversity within each species and a lack of gene flow between them. Finally, a population survey over time showed that B. cinerea was the predominant species but that B. pseudocinerea was more abundant in spring, on floral debris. This observation could not be explained by temperature adaptation in tests carried out in vitro or by aggressiveness on tomato or bean leaves. This study clearly establishes that B. cinerea and B. pseudocinerea constitute a complex of two cryptic species living in sympatry on several hosts, including grapevine and blackberry. We propose several biological or molecular tools for unambiguous differentiation between the two species. B. pseudocinerea probably makes a negligible contribution to gray mold epidemics on grapevine. This new species has been deposited in the MycoBank international database.

Multiple recent horizontal transfers of a large genomic region in cheese making fungi

While the extent and impact of horizontal transfers in prokaryotes are widely acknowledged, their importance to the eukaryotic kingdom is unclear and thought by many to be anecdotal. Here we report multiple recent transfers of a huge genomic island between Penicillium spp. found in the food environment. Sequencing of the two leading filamentous fungi used in cheese making, P. roqueforti and P. camemberti, and comparison with the penicillin producer P. rubens reveals a 575 kb long genomic island in P. roqueforti—called Wallaby—present as identical fragments at non-homologous loci in P. camemberti and P. rubens. Wallaby is detected in Penicillium collections exclusively in strains from food environments. Wallaby encompasses about 250 predicted genes, some of which are probably involved in competition with microorganisms. The occurrence of multiple recent eukaryotic transfers in the food environment provides strong evidence for the importance of this understudied and probably underestimated phenomenon in eukaryotes.

Expression and Functional Role of Peroxisome Proliferator-Activated Receptor-γ in Ovarian Folliculogenesis in the Sheep

Abstract Peroxisome proliferator-activated receptor (PPARγ) is a nuclear receptor that is activated by fatty acids and derivatives and the antidiabetic glitazones, which plays a role in the control of lipid and glucose homeostasis. In the present work, we tested the hypothesis that PPARγ plays a role in reproductive tissues by studying its expression and function in the hypothalamo-pituitary-ovary axis in the sheep. PPARγ 1 and PPARγ 2 proteins and mRNAs were detected in whole ovine pituitary and ovary but not in hypothalamic extracts. In situ hybridization on ovarian section localized PPARγ mRNA in the granulosa layer of follicles. Interestingly, PPARγ expression was higher in small antral (1–3 mm diameter) than in preovulatory follicles (>5 mm diameter) (P < 0.001) and was not correlated with healthy status. To assess the biological activity of ovarian PPARγ, ovine granulosa cells were transfected with a reporter construct driven by PPARγ-responsive elements. Addition of rosiglitazone, a PPARγ ligand, stimulated reporter gene expression, showing that endogenous PPARγ is functional in ovine granulosa cells in vitro. Moreover, rosiglitazone inhibited granulosa cell proliferation (P < 0.05) and increased the secretion of progesterone in vitro (P < 0.05). This stimulation effect was stronger in granulosa cells from small than from large follicles. In contrast, rosiglitazone had no effect on LH, FSH, prolactin and growth hormone secretion by ovine pituitary cells in vitro. Overall, these data suggest that PPARγ ligands might stimulate follicular differentiation in vivo likely through a direct action on granulosa cells rather than by modulating pituitary hormone secretion.

A taxonomic and ecological overview of cheese fungi

Cheese is made from milk by a succession of microbes (bacteria, yeasts and fungi) that determine the consistency and flavor of the cheese. Apart from the emblematic species, Penicillium camemberti and Penicillium roqueforti, cheese fungi are not well known. Here we present a taxonomic and phylogenetic overview of the most important filamentous cheese Ascomycota based on 133 isolates provided by the producers of cheese and cheese starter cultures and 97 isolates from culture collections. We checked the congruence of different gene genealogies to circumscribe cheese species and our results allow us to propose molecular targets for their identification. To study their phylogenetic affiliation, we used LSU rDNA and showed that cheese fungi are found in two classes, the Eurotiomycetes with Penicillium species (Eurotiales) and Sporendonema casei/Sphaerosporium equinum (Onygenales), and the Sordariomycetes with Scopulariopsis species (Microascales) and Fusarium domesticum (Hypocreales). Some of these fungi, such as, P. camemberti, F. domesticum, Scopulariopsis flava and S. casei, are only known from cheeses and are probably adapted to this particular habitat, which is extremely rich in protein and fat. Other cheese fungi are ubiquitous, such as, P. roqueforti, Scopulariopsis candida and Scopulariopsis fusca.

Regulation of anti-Müllerian hormone production in domestic animals

In mammals, anti-Müllerian hormone (AMH) expression is detected in the granulosa cells of all growing follicles and is highest in healthy small antral follicles, which contribute most significantly to AMH endocrine levels. AMH is a reliable endocrine marker of this population of gonadotrophin-responsive follicles in ruminants and, over the longer term, plasma AMH concentrations are characteristic of individual animals. In the cow, plasma AMH concentrations follow specific dynamic profiles throughout the prepubertal period, the oestrous cycle and the change from gestation to the post partum period, with the alterations most likely reflecting numerical changes in the population of high AMH-producing follicles. In granulosa cells, bone morphogenetic proteins (BMP) enhance AMH gene expression and AMH synthesis, with these effects antagonised by FSH. BMP could both support follicular growth and contribute significantly to the induction and/or maintenance of AMH expression in small growing follicles. AMH expression decreases sharply in large follicles when they become oestrogenic, suggesting a role for FSH and/or oestradiol in these changes, but the underlying mechanisms remain hypothetical. A better understanding of the factors and mechanisms regulating AMH production is needed to propose new strategies for managing the reserve of primordial and small growing follicles, as well as for improving embryo production.

Phaeoacremonium viticola, a new species associated with Esca disease of grapevine in France

A group of Phaeoacremonium isolates first distinguished by the red pigmentation of the reverse of their colonies, is described as a new species, P. viticola, on the basis of molecular data. An intensive sampling in French vineyards affected by the Esca disease has shown that this species is rare compared to P. aleophilum and P chlamydosporum and is often associated with symptoms on the fruits.

Biodegradation potential of hydrocarbon-assimilating tropical fungi

Abstract Strains of hydrocarbon-degrading fungi were isolated from tropical polluted environments in Indonesia: a forest soil and the sediments of a river which had been contaminated by petroleum spills. The biodegradation potential of these isolates was monitored by measuring the degradation rate of total petroleum, saturated hydrocarbons, aromatic hydrocarbons, resins and asphaltenes. Members of the genera Aspergillus, Penicillium, Gliocladium, Emericella, Graphium, Acremonium, Eupenicilium and Talaromyces were identified. The most active strains in the assimilation of saturates and aromatics were Emericella nidulans, Graphiwn putredinis, Eupenicillium javanicum and Aspergillus flavipes . Some isolates degraded significantly the resins and asphaltenes. Monospecific cultures were as efficient as mixed cultures. The degradative capacities were not constant within a species and this metabolic activity cannot be used in taxonomic studies.

Longevity effect of IGF-1R+/− mutation depends on genetic background-specific receptor activation

Growth hormone (GH) and insulin‐like growth factor (IGF) signaling regulates lifespan in mice. The modulating effects of genetic background gained much attention because it was shown that life‐prolonging effects in Snell dwarf and GH receptor knockout vary between mouse strains. We previously reported that heterozygous IGF‐1R inactivation (IGF‐1R+/−) extends lifespan in female mice on 129/SvPas background, but it remained unclear whether this mutation produces a similar effect in other genetic backgrounds and which molecules possibly modify this effect. Here, we measured the life‐prolonging effect of IGF‐1R+/− mutation in C57BL/6J background and investigated the role of insulin/IGF signaling molecules in strain‐dependent differences. We found significant lifespan extension in female IGF‐1R+/− mutants on C57BL/6J background, but the effect was smaller than in 129/SvPas, suggesting strain‐specific penetrance of longevity phenotypes. Comparing GH/IGF pathways between wild‐type 129/SvPas and C57BL/6J mice, we found that circulating IGF‐I and activation of IGF‐1R, IRS‐1, and IRS‐2 were markedly elevated in 129/SvPas, while activation of IGF pathways was constitutively low in spontaneously long‐lived C57BL/6J mice. Importantly, we demonstrated that loss of one IGF‐1R allele diminished the level of activated IGF‐1R and IRS more profoundly and triggered stronger endocrine feedback in 129/SvPas background than in C57BL/6J. We also revealed that acute oxidative stress entails robust IGF‐1R pathway activation, which could account for the fact that IGF‐1R+/− stress resistance phenotypes are fully penetrant in both backgrounds. Together, these results provide a possible explanation why IGF‐1R+/− was less efficient in extending lifespan in C57BL/6J compared with 129/SvPas.

Stylicins, a new family of antimicrobial peptides from the Pacific blue shrimp Litopenaeus stylirostris

The present study reports the characterization of Ls-Stylicin1, a novel antimicrobial peptide from the penaeid shrimp, Litopenaeus stylirostris. The predicted mature peptide of 82 residues is negatively charged (theoretical pI=5.0) and characterized by a proline-rich N-terminal region and a C-terminal region containing 13 cysteine residues. The recombinant Ls-Stylicin1 has been isolated in both monomeric and dimeric forms. Both display strong antifungal activity against Fusarium oxysporum (1.25 microM<MIC<2.5 microM), a pathogenic fungus of shrimp, but lower antimicrobial activity against Gram (-) bacteria, Vibrio sp. (40 microM<MIC<80 microM). However, rLs-Stylicin1 is able to agglutinate Vibrio penaeicidae in vitro in agreement with its potent LPS-binding activity on immobilized LPS of V. penaeicidae (dissociation constant (K(d)) of 9.6x10(-8)M). This molecule with no evident homology to other hitherto described antimicrobial peptides but identified herein several species of penaeid shrimp is thought to be the first member of a shrimp antimicrobial peptide family, which we termed stylicins.