Production of Fumonisin B(inf1) and Moniliformin by Gibberella fujikuroi from Rice from Various Geographic Areas

Gibberella fujikuroi strains isolated from rice in the United States, Asia, and other geographic areas were tested for sexual fertility with members of mating population D and for production of fumonisin B(inf1) and moniliformin in culture. Of the 59 field strains tested, 32 (54%) were able to cross with tester strains of mating population D, but only a few ascospores were produced in most of these crosses. Thirty-four strains produced more than 10 (mu)g of fumonisin B(inf1) per g, but only three strains produced more than 1000 (mu)g/g. Twenty-five strains produced more than 100 (mu)g of moniliformin per g, and 15 produced more than 1,000 (mu)g/g. Seven field strains produced both fumonisin B(inf1) and moniliformin, but none of these strains produced a high level of fumonisin B(inf1) (>1,000 (mu)g/g). However, a genetic cross between a strain that produced fumonisin B(inf1) but no moniliformin and a strain that produced moniliformin but no fumonisin B(inf1) yielded progeny that produced high levels of both toxins. Strains of G. fujikuroi isolated from rice infected with bakanae disease are similar to strains of mating population D isolated from maize in their ability to produce both fumonisins and moniliformin. This finding suggests a potential for contamination of rice with both fumonisins and moniliformin.     

Mycotoxins in developing countries: A case study of maize in Nepal

Maize (Zea mays) is an important food crop in the foothills of the Nepal Himalaya Mountains. Surveys have found that maize in Nepal is contaminated withFusarium species, mainlyF. verticillioides andF. proliferatum, which produce fumonisins, andF. graminearum, which produces trichothecenes, mainly nivalenol and 4-deoxynivalenol. Maize from smallholder farms and markets is often contaminated with fumonisins and trichothecenes above 1000 ng/g, a level of concern for human health. These mycotoxins were not eliminated by traditional fermentation for producing maize beer, but Nepalese women were able to detoxify contaminated maize by hand-sorting visibly disease kernels. An integrated approach to reduce mycotoxins risks in maize in Nepal and other developing countries should include plant breeding to produce ear rot resistant cultivars, along with education in mycotoxins risks and in agricultural and grain storage practices to reduce mycotoxin contamination. Presented at the EU-USA Bilateral Workshop on Toxigenic Fungi & Mycotoxins, New Orleans, USA, July 5–7, 2005     

Effect of sulphate on photosynthesis in greenhouse–grown tomato plants

Sulphate accumulates in the rhizosphere of plants grown in hydroponic systems. To avoid such sulphate accumulation and promote the use of environmentally sound hydroponic systems, we examined the effects of four sulphate concentrations (0.1, 5,2, 10.4 and 20.8 m M ) on photosynthesis, ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) activities and related physiological processes in greenhouse–grown tomato plants ( Lycopersicon esculentum Mill. cv. Trust). The lowest sulphate concentration (0.1 m M ) significantly decreased photosynthetic capacity (P_c) and Rubisco activities on a leaf area basis. This result was supported by our data for dry matter per plant, which was low for plants in the 0.1 m M treatment. The photosynthesis-related variables such as leaf conductance, chlorophyll and soluble protein were lowest for the 0.1 m M treatment. Both total Rubisco activity and the activated ratio were reduced with this treatment. However, Rubisco activities expressed per g of protein or per g of chlorophyll were not significantly affected. These results suggest that sulphur deficiency depressed P_c– by reducing the amount of both Rubisco and chlorophyll and by causing an inactivation of Rubisco. The ratio of organic sulphur vs organic nitrogen (S/N) in plants of the 0.1 m M treatment was far below the normal values. This low S/N ratio might be accountable for the negative effect of low sulphate on P_c and plant growth. P_c and dry matter were not affected until sulphate concentration in the nutrient solution reached a high level of 20.8 m M .     

Development and characterization of continuous avian cell lines depleted of mitochondrial DNA

Summary Populations of quail and chicken cells were treated with ethidium bromide, an inhibitor of mitochondrial DNA replication. After long-term exposure to the drug, the cell populations were transferred to ethidium bromide (EtdBr)-free medium, and cloned. Clones HCF7 (quail) and DUS-3 (chicken) were propagated for more than a year, and then characterized. Analysis of total cellular DNA extracted from these cells revealed no characteristic mitochondrial DNA molecule by Southern blot hybridization of HindIII- or AvaI-digested total cellular DNA probed with cloned mitochondrial DNA fragments. Reconstruction experiments, where a small number of parental cells was mixed with HCF7 cells and DUS-3 cells before extraction of total cellular DNA, further strengthen the notion that the drug-treated cells are devoid of mitochondrial DNA molecules. The cell populations were found to proliferate at a moderately reduced growth rate as compared to their respective parents, to be auxotrophic for uridine, and to be stably resistant to the growth inhibitory effect of EtdBr and chloramphenicol. At the ultrastructural level, mitochondria were considerably enlarged and there was a severe reduction in the number of cristae within the organelles and loss of cristae orientation. Morphometric analysis revealed a fourfold increase of the mitochondrial profile area along with a twofold decrease of the numerical mitochondrial profiles. Analysis of biochemical parameters indicated that the cells grew with mitochondria devoid of a functional respiratory chain. The activity of the mitochondrial enzyme dihydroorotate dehydrogenase was decreased by 95% and presumably accounted for uridine auxotrophy. This work was supported by a grant from the Medical Research Council of Canada.     

Production of fumonisins by Fusarium moniliforme strains from various substrates and geographic areas.

Strains of Fusarium moniliforme from different geographic areas and from corn and other substrates were tested for the ability to produce fumonisins in culture. The test results indicate that the potential exists for production of fumonisins by such strains in agricultural commodities and other substrates in widespread geographic areas.     

Stainless steel mesh supports high density cell growth and production of recombinant Mullerian Inhibiting Substances

Summary Stainless steel mesh supported the high density growth of anchorage dependent CHO fibroblasts without the use of a special culture system. CHO cells, designated B-9, containing an amplified genomic construct of the human gene for Mullerian Inhibiting Substance (MIS), grew to a high confluent density on stainless steel meshwork while producing substantial amounts of human recombinant MIS over a long period of time. The mesh could be easily coated with various extracellular matrix proteins, such as Laminin, Fibronectin, Collagen or Matrigel, which permitted the testing of the effects of surface modifications on cell yield and recombinant protein production. Since the amount of medium per surface area required for optimal cell growth is lower than for some large volume cell culture methods, media costs can be reduced using mesh. In addition, no special cell culture equipment or complex manipulations are required. Thus, the use of meshwork for anchorage-dependent cells can increase the efficiency of growth and decrease the cost of recombinant protein production. This work is supported by NIH grant CA 17393 and American Cancer Society grant PDT 221A to P. K. D. and NIH grant EY 06535 to J. E. Editor's Statement This approach to large scale, high density cultivation of cells, one of several which are based on increasing surface area of the cultures, allows the production of large amounts of recombinant product within a research laboratory with modest bulk culture capability.     

Modulation of endocytosis in nuclear factor IL-6(-/-) macrophages is responsible for a high susceptibility to intracellular bacterial infection

Activated macrophages kill bacteria, a function known to depend on the expression of NF-IL-6. Here, it is demonstrated that the attenuated Brucella abortus vaccine strain 19 replicates much better in NF-IL-6-/- than in NF-IL-6(+/+) and NF-IL-6(+/+)-activated murine macrophages and at levels comparable to those observed in normal macrophages infected with the pathogenic strain 2308. The role of NF-IL-6 in the inhibition of intracellular bacterial replication is related to its control of endocytosis and membrane fusion between endosomes and Brucella-containing phagosomes. Addition of the granulocyte-CSF (G-CSF), whose induction is impaired in NF-IL-6(-/-) macrophages, restores both endocytosis and the morphology of endosomes, together with bactericidal activity. Regulation of membrane traffic in endocytosis by G-CSF whose expression is controlled by NF-IL-6 may explain how a host cell can control intracellular bacterial replication.