The classification of organisms at the edge of life, or Problems with virus systematics

South African Journal of Science 01/1990; 86:182-186.
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    ABSTRACT: Comparisons of genome and polyprotein sequences of hepatitis C virus (HCV) isolates world-wide has led to the identification of nine major genotypes and many subtypes. This classification is based on either complete genome/polyprotein sequences or sequence data from the 5' noncoding region, core, E1, NS3 or NS5B genes. The relative merit of different gene segments as taxonomic markers and the validity of the resulting assignments is not clear at this stage. To resolve the taxonomy of HCV genotypes and subtypes, we have compared the complete genome and polyprotein sequences of 19 HCV isolates available in the databases as well as sequences of individual genes and gene products of these isolates. Based on the correlation between sequence relationships and taxonomic assignments of other RNA viruses, we show that the nine major genotypes of HCV represent nine distinct virus species and their subtypes subspecies. Our sequence comparison of the 5' noncoding regions and the individual gene products suggests that E2, NS2, NS5B, E1, NS4A, NS4B and NS5A (in that order) are the most appropriate regions for the discrimination between species, subspecies and strains of HCV. The 5' noncoding, core and NS3 regions are less effective in distinguishing between species, subspecies and strains. Based on a comparison of the polymerase sequence identities of HCVs, pestiviruses and flaviviruses as well as the recent information on the size and morphology of HCV virions, we propose that HCVs, pestiviruses and flaviviruses should be classified into three separate families, named Hepciviridae, Pestiviridae and Flaviviridae, respectively rather than three genera of the Flaviviridae as currently classified. We also propose "Hepcivirus" as the genus name for HCVs.
    Archives of Virology 02/1995; 140(10):1747-61. · 2.03 Impact Factor
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    ABSTRACT: The role of personal computer (PC) and its associated accessories in this present knowledge-based global economy cannot be overemphasized. Its applicat ion is highly significant being a tool for the transfer of information world wide, this consequently resulted in an increase in the rate at wh ich the public interact with it. Co mputer system has been identified as formites which could serve as a portal through which pathogens can be transmitted among user. An essential part of a PC is the keyboard; certain microbes have been isolated fro m the surface of co mputer keyboard (CK) which had been linked with many infections and disease conditions. The need to identify the possibilit ies of CK to act as a reservoir host for the transmission of this pathogenic organism to ambient users led to this study. This study aimed to review the role CKs p lay in the t ransfer of pathogens in Nigeria and to sensitize Nigerian on the possibilities of contacting infectious diseases through CKs. This paper also provides policy reco mmendations on the necessary measures that could be adopted to min imize such infections.
    International Journal of Geographical Information Science 01/2012; 2012(2):37-41. · 1.61 Impact Factor
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    ABSTRACT: Summary Using a multiple alignment program, we surveyed about 150 proteins from 35 tailed phages and calculated identity percentages. Sequence similarities are generally weak, indicating an extensive diversification of tailed phages. Related proteins occur in phages of different morphology and host range. DNA and RNA polymerases, integrases, muramidases, and several other tailed phage proteins appear to be acquired from bacteria. Tailed phages seem to be a monophyletic group and to constitute a polythetic order. Proteins common to all tailed phages may be detected by comparing the three-dimensional structure of major head and tail proteins. Amino acid alignments have presently no impact on the definition of high-level taxa of tailed phages.
    Archives of Virology 02/1995; 140(10):1871-84. · 2.03 Impact Factor


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Mar 18, 2013