Browsing by Author "van Zyl, Lonnie"

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    High-level diversity of tailed phages, eukaryote-associated viruses, and virophage-like elements in the metaviromes of Antarctic soils
    (American Society for Microbiology, 2014) Zablocki, Olivier; van Zyl, Lonnie; Adriaenssens, Evelien M.; Rubagotti, Enrico; Tuffin, Marla; Cary, Stephen Craig; Cowan, Donald A.
    The metaviromes of two distinct Antarctic hyperarid desert soil communities have been characterized. Hypolithic communities, cyanobacterium-dominated assemblages situated on the ventral surfaces of quartz pebbles embedded in the desert pavement, showed higher virus diversity than surface soils, which correlated with previous bacterial community studies. Prokaryotic viruses (i.e., phages) represented the largest viral component (particularly Mycobacterium phages) in both habitats, with an identical hierarchical sequence abundance of families of tailed phages (Siphoviridae>Myoviridae>Podoviridae). No archaeal viruses were found. Unexpectedly, cyanophages were poorly represented in both metaviromes and were phylogenetically distant from currently characterized cyanophages. Putative phage genomes were assembled and showed a high level of unaffiliated genes, mostly from hypolithic viruses. Moreover, unusual gene arrangements in which eukaryotic and prokaryotic virus-derived genes were found within identical genome segments were observed. Phycodnaviridae and Mimiviridae viruses were the second-mostabundant taxa and more numerous within open soil. Novel virophage-like sequences (within the Sputnik clade) were identified. These findings highlight high-level virus diversity and novel species discovery potential within Antarctic hyperarid soils and may serve as a starting point for future studies targeting specific viral groups.
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    Screening for subtate tolerant Geobacillus pallidus RAPc8 nitrile hydratase
    (University of the Western Cape, 2009) Mketsu, Moses Clive Masisange; Cowan, Don A.; Tuffin, Marla; van Zyl, Lonnie; Dept. of Biotechnology; Faculty of Science
    In this study G. pallidus RAPc8 NHase mutants were screened for reduced substrate inhibition compared to the wild type enzyme. Wild type and mutant enzymes were expressed and purified using hydrophobic interaction chromatography. Amidase coupled enzyme stop assays were conducted using 3-cyanopyridine as a substrate, whereas continuous enzyme kinetics were conducted using acrylonitrile as a substrate.