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    ABSTRACT: The phylogenetic position of diatoms belonging to the genus Attheya is presently under debate. Species belonging to this genus have been placed in the subclasses Chaetocerotophycidae and Biddulphiophycidae, but published phylogenetic trees based on 18S rDNA, morphology, and sexual reproduction indicate that this group of diatoms may be a sister group of the pennates. To clarify the position of Attheya, we studied the morphology, 18S rDNA, 16S rDNA of the chloroplasts, the rbcL large subunit (LSU) sequences of the chloroplasts, and the sterol composition of three different strains of Attheya septentrionalis (Østrup) R. M. Crawford and one strain of Attheya longicornis R. M. Crawford et C. Gardner. These data were compared with data from more than 100 other diatom species, covering the whole phylogenetic tree, with special emphasis on species belonging to the genera that have been suggested to be related to the genus Attheya. All data suggest that the investigated Attheya species form a separate group of diatoms, and there is no indication that they belong to either the Chaetocerotophycidae or the Biddulphiophycidae. Despite applying these various approaches, we were unable to determine the exact phylogenetic position of the investigated Attheya species within the diatoms.
    Journal of Phycology 03/2009; 45(2):444 - 453. · 2.24 Impact Factor
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    ABSTRACT: Marine Crenarchaeota from tropical Indian Ocean water were incubated at temperatures ranging from 25 to 40 °C to study the changes in glycerol dibiphytanyl glycerol tetraether (GDGT) membrane lipid composition. The results show that Crenarchaeota were able to thrive at temperatures up to 40 °C. Archaeal 16S ribosomal DNA analysis revealed that different species proliferated with moderate (25 °C) and high (36 °C) optimum growth temperatures. Analysis of the GDGT distribution shows a similar linear correlation of TEX86 with incubation temperature as demonstrated previously for incubation experiments at lower temperatures [Wuchter, C., Schouten, S., Coolen, M.J.L., Sinninghe Damsté, J.S., 2004. Paleoceanography 19, PA4028, doi:10.1029/2004PA001041]. Our results show that Crenarchaeota can thrive at temperatures warmer than present day tropical sea surface temperatures, such as the high temperature (up to 40 °C) inferred for tropical oceans in ancient greenhouse worlds. Our results also imply that the TEX86 is still applicable in this regime. However, the crenarchaeol regioisomer in the GDGT distribution obtained from the incubation experiments is substantially less than in sediments deposited in exceptionally warm oceans of the geological past, so our laboratory results cannot be directly used to convert TEX86 values from these sediments into temperature.
    Organic Geochemistry. 01/2007;
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    ABSTRACT: Envelope glycoprotein E(rns) of classical swine fever virus (CSFV) has been shown to contain RNase activity and is involved in virus infection. Two short regions of amino acids in the sequence of E(rns) are responsible for RNase activity. In both regions, histidine residues appear to be essential for catalysis. They were replaced by lysine residues to inactivate the RNase activity. The mutated sequence of E(rns) was inserted into the p10 locus of a baculovirus vector and expressed in insect cells. Compared to intact E(rns), the mutated proteins had lost their RNase activity. The mutated proteins reacted with E(rns)-specific neutralizing monoclonal and polyclonal antibodies and were still able to inhibit infection of swine kidney cells (SK6) with CSFV, but at a concentration higher than that measured for intact E(rns). This result indicated that the conformation of the mutated proteins was not severely affected by the inactivation. To study the effect of these mutations on virus infection and replication, a CSFV mutant with an inactivated E(rns) (FLc13) was generated with an infectious DNA copy of CSFV strain C. The mutant virus showed the same growth kinetics as the parent virus in cell culture. However, in contrast to the parent virus, the RNase-negative virus induced a cytopathic effect in swine kidney cells. This effect could be neutralized by rescue of the inactivated E(rns) gene and by neutralizing polyclonal antibodies directed against E(rns), indicating that this effect was an inherent property of the RNase-negative virus. Analyses of cellular DNA of swine kidney cells showed that the RNase-negative CSFV induced apoptosis. We conclude that the RNase activity of envelope protein E(rns) plays an important role in the replication of pestiviruses and speculate that this RNase activity might be responsible for the persistence of these viruses in their natural host.
    Journal of Virology 02/1998; 72(1):151-7. · 5.08 Impact Factor
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    ABSTRACT: antibodies and were still able to inhibit infection of swine kidney cells (SK6) with CSFV, but at a concentration higher than that measured for intact Erns. This result indicated that the conformation of the mutated proteins was not severely affected by the inactivation. To study the effect of these mutations on virus infection and replication, a CSFV mutant with an inactivated Erns (FLc13) was generated with an infectious DNA copy of CSFV strain C. The mutant virus showed the same growth kinetics as the parent virus in cell culture. However, in contrast to the parent virus, the RNase-negative virus induced a cytopathic effect in swine kidney cells. This effect could be neutralized by rescue of the inactivated Erns gene and by neutralizing polyclonal antibodies directed against Erns, indicating that this effect was an inherent property of the RNase-negative virus. Analyses of cellular DNA of swine kidney cells showed that the RNase-negative CSFV induced apoptosis. We conclude that the RNase activity of envelope protein Erns plays an important role in the replication of pestiviruses and
    Journal of virology 72, 1998, 151-157.

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