9,10-Anthraquinone Reduces the Photosynthetic Efficiency of Oscillatoria perornata and Modifies Cellular Inclusions

The natural compound 9,10-anthraquinone was found to inhibit the growth of the musty odor-producing cyanobacterium Oscillatoria perornata at a low concentration (1 μM) in previous laboratory studies. In this study, the mode of action of 9,10-anthraquinone was investigated by observing ultrastructural changes in O. perornata and by monitoring chlorophyll fluorescence as an indicator of photosynthetic efficiency. Results indicate that 9,10-anthraquinone inhibits photosynthetic electron transport, probably at PSII, and thereby affects growth. Moreover, 9,10-anthraquinone treatment caused thylakoid disorganization and reduced the number of ribosomes in O. perornata. The thylakoid disorganization is identical to reported modification in a cyanobacterium treated with simazine, a PSII inhibitor.     

Global transcriptional response to mammalian temperature provides new insight into <Emphasis Type="Italic">Francisella tularensis</Emphasis> pathogenesis

Background  

After infecting a mammalian host, the facultative intracellular bacterium,Francisella tularensis, encounters an elevated environmental temperature. We hypothesized that this temperature change may regulate genes essential for infection.     

Replication and transmission of H9N2 influenza viruses in ferrets: evaluation of pandemic potential

H9N2 avian influenza A viruses are endemic in poultry of many Eurasian countries and have caused repeated human infections in Asia since 1998. To evaluate the potential threat of H9N2 viruses to humans, we investigated the replication and transmission efficiency of H9N2 viruses in the ferret model. Five wild-type (WT) H9N2 viruses, isolated from different avian species from 1988 through 2003, were tested in vivo and found to replicate in ferrets. However these viruses achieved mild peak viral titers in nasal washes when compared to those observed with a human H3N2 virus. Two of these H9N2 viruses transmitted to direct contact ferrets, however no aerosol transmission was detected in the virus displaying the most efficient direct contact transmission. A leucine (Leu) residue at amino acid position 226 in the hemagglutinin (HA) receptor-binding site (RBS), responsible for human virus-like receptor specificity, was found to be important for the transmission of the H9N2 viruses in ferrets. In addition, an H9N2 avian-human reassortant virus, which contains the surface glycoprotein genes from an H9N2 virus and the six internal genes of a human H3N2 virus, showed enhanced replication and efficient transmission to direct contacts. Although no aerosol transmission was observed, the virus replicated in multiple respiratory tissues and induced clinical signs similar to those observed with the parental human H3N2 virus. Our results suggest that the establishment and prevalence of H9N2 viruses in poultry pose a significant threat for humans.     

Bio-degradation of lignin in olive pomace by freshly-isolated species of Basidiomycete

The solid waste (pomace) from olive oil processing cannot be used directly as an animal feed, but it was thought that an appropriate series of fermentations might improve its nutritional value. As a first step, typical samples of pomace were subjected, after an alkaline pre-treatment, to delignification by Phanerochaete chrysosporium (ATCC 19343), Oxysporus sp., Schizophyllum commune, Hyphoderma sp. or Ganoderma sp.; the last four species being freshly isolated from decaying wood collected in a woodland in Jordan. The relative activity of the species was judged by the levels of ligninase or laccase secreted and the extent of lignin degradation under a range of experimental conditions. Oxysporus sp. (ca. 69%) and S. commune (ca. 53%) gave significantly higher levels of breakdown of the lignified material than the other recent isolates. P. chrysosporium (ca. 60%) was not as active as in previously reported studies, and it may be that culturing the fungus on a standard laboratory medium had reduced its ability to generate ligninase. Further work is needed to establish whether the delignified pomace could be further processed into a feed for poultry.     

Effect of salt on the binding of the linker histone H1 to DNA and nucleosomes

The linker histones are involved in the salt-dependent folding of the nucleosomes into higher-order chromatin structures. To better understand the mechanism of action of these histones in chromatin, we studied the interactions of the linker histone H1 with DNA at various histone/DNA ratios and at different ionic strengths. In direct competition experiments, we have confirmed the binding of H1 to superhelical DNA in preference to linear or nicked circular DNA forms. We show that the electrophoretic mobility of the H1/supercoiled DNA complex decreases with increasing H1 concentrations and increases with ionic strengths. These results indicate that the interaction of the linker histone H1 with supercoiled DNA results in a soluble binding of H1 with DNA at low H1 or salt concentrations and aggregation at higher H1 concentrations. Moreover, we show that H1 dissociates from the DNA or nucleosomes at high salt concentrations. By the immobilized template pull-down assay, we confirm these data using the physiologically relevant nucleosome array template.