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Antiviral drug discovery: preparing for the next pandemic

  • Authors: Adamson, Catherine S , Chibale, Kelly , Goss, Rebecca J M , Jaspars, Marcel , Newman, David J , Dorrington, Rosemary A
  • Date: 2021
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/177499 , vital:42827 , DOI: 10.1039/d0cs01118e
  • Description: Clinically approved antiviral drugs are currently available for only 10 of the more than 220 viruses known to infect humans. The SARS-CoV-2 outbreak has exposed the critical need for compounds that can be rapidly mobilised for the treatment of re-emerging or emerging viral diseases, while vaccine development is underway. We review the current status of antiviral therapies focusing on RNA viruses, highlighting strategies for antiviral drug discovery and discuss the challenges, solutions and options to accelerate drug discovery efforts.
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  • Date Issued: 2021

Unlocking the Diversity of Pyrroloiminoquinones Produced by Latrunculid Sponge Species

  • Authors: Kalinski, Jarmo-Charles J , Krause, Rui W M , Parker-Nance, Shirley , Waterworth, Samantha C , Dorrington, Rosemary A
  • Date: 2021
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/191802 , vital:45165 , xlink:href="https://doi.org/10.3390/md19020068"
  • Description: Sponges of the Latrunculiidae family produce bioactive pyrroloiminoquinone alkaloids including makaluvamines, discorhabdins, and tsitsikammamines. The aim of this study was to use LC-ESI-MS/MS-driven molecular networking to characterize the pyrroloiminoquinone secondary metabolites produced by six latrunculid species. These are Tsitsikamma favus, Tsitsikamma pedunculata, Cyclacanthia bellae, and Latrunculia apicalis as well as the recently discovered species, Tsitsikamma nguni and Tsitsikamma michaeli. Organic extracts of 43 sponges were analyzed, revealing distinct species-specific chemical profiles. More than 200 known and unknown putative pyrroloiminoquinones and related compounds were detected, including unprecedented makaluvamine-discorhabdin adducts and hydroxylated discorhabdin I derivatives. The chemical profiles of the new species T. nguni closely resembled those of the known T. favus (chemotype I), but with a higher abundance of tsitsikammamines vs. discorhabdins. T. michaeli sponges displayed two distinct chemical profiles, either producing mostly the same discorhabdins as T. favus (chemotype I) or non- or monobrominated, hydroxylated discorhabdins. C. bellae and L. apicalis produced similar pyrroloiminoquinone chemistry to one another, characterized by sulfur-containing discorhabdins and related adducts and oligomers. This study highlights the variability of pyrroloiminoquinone production by latrunculid species, identifies novel isolation targets, and offers fundamental insights into the collision-induced dissociation of pyrroloiminoquinones.
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  • Date Issued: 2021

An update on the indigenous vascular flora of sub-Antarctic Marion Island: taxonomic changes, sequences for DNA barcode loci, and genome size data

  • Authors: Chau, John H , Mtsi, Nasipi I S , Münbergová, Zuzana , Greve, Michelle , le Roux, Peter C , Mairal, Mario , Le Roux, Johannes J , Dorrington, Rosemary A , van Vuuren, Bettine
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/160344 , vital:40437 , https://0-doi.org.wam.seals.ac.za/10.1007/s00300-020-02747-7
  • Description: The flora of sub-Antarctic Marion Island forms part of the unique South Indian Ocean Biogeographic Province, and is under threat from climate change and invasive species. Current information on the flora is necessary to rapidly identify and manage future changes. We conducted a literature search on the taxonomy of indigenous vascular plant species on Marion Island and found nomenclatural changes following taxonomic revisions for Austroblechnum penna-marina (Poir.) Gasper and V.A.O.Dittrich, Carex dikei (Nelmes) K.L.Wilson, Leptinella plumosa Hook.f., Notogrammitis crassior (Kirk) Parris, Phlegmariurus saururus (Lam.) B.Øllg., and Polypogon magellanicus (Lam.) Finot. Additionally, Ranunculus moseleyi Hook.f. was removed from our species checklist due to its long absence in floristic surveys, leaving 21 species in the indigenous vascular plant flora present on Marion Island. We also amplified and sequenced the universal plant barcoding loci rbcL and matK for 19 and 13 species, respectively, and found that ample interspecific genetic distance and minimal intraspecific genetic distance allowed for easy discrimination between species.
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  • Date Issued: 2020

Conserved bacterial genomes from two geographically isolated peritidal stromatolite formations shed light on potential functional guilds

  • Authors: Waterworth, Samantha C , Isemonger, Eric W , Rees, Evan R , Dorrington, Rosemary A
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/429411 , vital:72608 , xlink:href="https://doi.org/10.1111/1758-2229.12916"
  • Description: Stromatolites are complex microbial mats that form lithified layers. Fossilized stromatolites are the oldest evidence of cellular life on Earth, dating back over3.4 billion years. Modern stromatolites are relatively rare but may provide clues about the function and evolution of their ancient counterparts. In this study, we focus on peritidal stromatolites occurring at Cape Recife and Schoenmakerskop on the southeastern South African coastline, the former being morphologically and structurally similar to fossilized phosphatic stromatolites formations. Using assembled shotgun metagenomic analysis, we obtained 183 genomic bins, of which the most dominant taxa were from the Cyanobacteria phylum. We identified functional gene sets in genomic bins conserved across two geographically isolated stromatolite formations, which included relatively high copy numbers of genes involved in the reduction of nitrates and phosphatic compounds. Additionally, we found little evidence of Archaeal species in these stromatolites, suggesting that they may not play an important role in peritidal stromatolite formations, as proposed for hypersaline formations.
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  • Date Issued: 2020

Living phosphatic stromatolites in a low-phosphorus environment: Implications for the use of phosphorus as a proxy for phosphate levels in paleosystems

  • Authors: Buttner, Steffen H , Isemonger, Eric W , Isaacs, Michelle , van Niekerk, Deon , Sipler, Rachel E , Dorrington, Rosemary A
  • Date: 2020
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/429450 , vital:72611 , xlink:href="https://doi.org/10.1111/gbi.12415"
  • Description: In the geological record, fossil phosphatic stromatolites date back to the Great Oxidation Event in the Paleoproterozoic, but living phosphatic stromatolites have not been described previously. Here, we report on cyanobacterial stromatolites in a supratidal freshwater environment at Cape Recife, South African southern coast, precipitating Ca carbonate alternating with episodes of Ca phosphate deposition. In their structure and composition, the living stromatolites from Cape Recife closely resemble their fossilized analogues, showing phosphatic zonation, microbial casts, tunnel structures and phosphatic crusts of biogenic origin. The microbial communities appear to be also similar to those proposed to have formed fossil phosphatic stromatolites. Phosphatic domains in the material from Cape Recife are spatially and texturally associated with carbonate precipitates, but form distinct entities separated by sharp boundaries. Electron Probe Micro-Analysis shows that Ca/P ratios and the overall chemical compositions of phosphatic precipitates are in the range of octacalcium phosphate, amorphous tricalcium phosphate and apatite. The coincidence in time of the emergence of phosphatic stromatolites in the fossil record with a major episode of atmospheric oxidation led to the assumption that at times of increased oxygen release the underlying increased biological production may have been linked to elevated phosphorus availability. The stromatolites at Cape Recife, however, form in an environment where ambient phosphorus concentrations do not exceed 0.28μM, one to two orders of magnitude below the previously predicted minimum thresh-old of >5 μM for biogenic phosphate precipitation in paleo-systems. Accordingly, we contest the previously proposed suitability of phosphatic stromatolites as a proxy for high ambient phosphate concentrations in supratidal to shallow ocean settings in earth history.
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  • Date Issued: 2020

Molecular Networking Reveals Two Distinct Chemotypes in Pyrroloiminoquinone-Producing Tsitsikamma favus Sponges

  • Authors: Kalinski, Jarmo-Charles J , Waterworth, Samantha C , Noundou, Xavier S , Jiwaji, Meesbah , Parker-Nance, Shirley , Krause, Rui W M , McPhail, Kerry L , Dorrington, Rosemary A
  • Date: 2019
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/131618 , vital:36673 , https://doi.org/10.3390/md17010060
  • Description: The temperate marine sponge, Tsitsikamma favus, produces pyrroloiminoquinone alkaloids with potential as anticancer drug leads. We profiled the secondary metabolite reservoir of T. favus sponges using HR-ESI-LC-MS/MS-based molecular networking analysis followed by preparative purification efforts to map the diversity of new and known pyrroloiminoquinones and related compounds in extracts of seven specimens. Molecular taxonomic identification confirmed all sponges as T. favus and five specimens (chemotype I) were found to produce mainly discorhabdins and tsitsikammamines. Remarkably, however, two specimens (chemotype II) exhibited distinct morphological and chemical characteristics: the absence of discorhabdins, only trace levels of tsitsikammamines and, instead, an abundance of unbranched and halogenated makaluvamines. Targeted chromatographic isolation provided the new makaluvamine Q, the known makaluvamines A and I, tsitsikammamine B, 14-bromo-7,8-dehydro-3-dihydro-discorhabdin C, and the related pyrrolo-ortho-quinones makaluvamine O and makaluvone. Purified compounds displayed different activity profiles in assays for topoisomerase I inhibition, DNA intercalation and antimetabolic activity against human cell lines. This is the first report of makaluvamines from a Tsitsikamma sponge species, and the first description of distinct chemotypes within a species of the Latrunculiidae family. This study sheds new light on the putative pyrroloiminoquinone biosynthetic pathway of latrunculid sponges
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  • Date Issued: 2019

A cytotoxic pentadecapeptide from a South African Didemnid tunicate

  • Authors: Gallegos, D , Serrill, J , Parker-Nance, Shirley , Dorrington, Rosemary A , Ishmael, J , McPhail, Kerry L
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/65935 , vital:28863 , https://doi.org/10.1055/s-0036-1596683
  • Description: publisher version , The rate of discovery of new natural product chemical entities has plateaued, and unique populations of endemic, biologically diverse sessile marine organisms represent increasingly critical opportunities to discover new chemistry. Discovery of the mandelalides [1] as potent inhibitors of cancer cell growth from the new South African tunicate Lissoclinum mandelai is an example of the diverse suites of metabolites with potent biological activities that have been isolated from tunicates and other filter-feeding sessile marine organisms that house complex microbial consortia. Further investigation of archived and new tunicate collections from Algoa Bay, South Africa, has revealed a group of didemnid tunicates with an unusual gelatinous morphology similar to Lissoclinum mandelai. Using a bioassay-guided isolation approach, a new “gelatinous” species of the genus Didemnum has yielded a cytotoxic pentadecapeptide with a molecular mass of 1603.7688 Da, comprising fifteen residues including both proteinogenic and non-proteinogenic amino acids. The pure compound inhibited both HeLa cervical cancer and NCI-H460 non-small cell lung cancer cell lines when tested at 30 nM in preliminary assays against cells seeded at low densities. Inhibition of cancer cells at low starting density may be indicative of an anti-proliferative mechanism of action. The compound did not show antibacterial activity against Vibrio cholera. Didemnin B and its clinically approved analogue dehydrodidemnin B (plitidepsin, Aplidin®) [2, 3] are important macrocyclic depsipeptides from a didemnid tunicate. The pentadecapeptide reported here provides justification for our continued investigation of unique, endemic didemnid tunicates from South Africa as a source of new macrocyclic natural products with cytotoxic, anti-viral or antimicrobial activity. , We acknowledge the South African government for permission to collect the subject tunicate (Collection Permit No. 278 RES2013/43)
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  • Date Issued: 2016

Binding and entry of a non-enveloped T=4 insect RNA virus is triggered by alkaline pH

  • Authors: Penkler, David L , Jiwaji, Meesbah , Domitrovic, Tatiana , Short, James R , Johnson, John E , Dorrington, Rosemary A
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/65995 , vital:28875 , https://doi.org/10.1016/j.virol.2016.08.028
  • Description: publisher version , Tetraviruses are small, non-enveloped, RNA viruses that exclusively infect lepidopteran insects. Their particles comprise 240 copies of a single capsid protein precursor (CP), which undergoes autoproteolytic cleavage during maturation. The molecular mechanisms of capsid assembly and maturation are well understood, but little is known about the viral infectious lifecycle due to a lack of tissue culture cell lines that are susceptible to tetravirus infection. We show here that binding and entry of the alphatetravirus, Helicoverpa armigera stunt virus (HaSV), is triggered by alkaline pH. At pH 9.0, wild-type HaSV virus particles undergo conformational changes that induce membrane-lytic activity and binding to Spodoptera frugiperda Sf9 cells. Binding is followed by entry and infection, with virus replication complexes detected by immunofluorescence microscopy within 2 h post-infection and the CP after 12 h. HaSV particles produced in S. frugiperda Sf9 cells are infectious. Helicoverpa armigera larval virus biofeed assays showed that pre-treatment with the V-ATPase inhibitor, Bafilomycin A1, resulted in a 50% decrease in larval mortality and stunting, while incubation of virus particles at pH 9.0 prior to infection restored infectivity. Together, these data show that HaSV, and likely other tetraviruses, requires the alkaline environment of the lepidopteran larval midgut for binding and entry into host cells.
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  • Date Issued: 2016

Expanding the host range of small insect RNA viruses: Providence virus (Carmotetraviridae) infects and replicates in a human tissue culture cell line

  • Authors: Jiwaji, Meesbah , Short, James R , Dorrington, Rosemary A
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/65979 , vital:28874 , https://doi.org/10.1099/jgv.0.000578
  • Description: publisher version , Tetraviruses are small, positive (+ve)-sense ssRNA viruses that infect the midgut cells of lepidopteran larvae. Providence virus(PrV) is the only member of the family Carmotetraviridae (previously Tetraviridae). PrV particles exhibit the characteristic tetraviral T=4 icosahedral symmetry, but PrV is distinct from other tetraviruses with respect to genome organization and viral non-structural proteins. Currently, PrV is the only tetravirus known to infect and replicate in lepidopteran cell culture lines. In this report we demonstrate, using immunofluorescence microscopy, that PrV infects and replicates in a human tissue culture cell line (HeLa), producing infectious virus particles. We also provide evidence for PrV replication in vitro in insect, mammalian and plant cell-free systems. This study challenges the long-held view that tetraviruses have a narrow host range confined to one or a few lepidopteran species and highlights the need to consider the potential for apparently non-infectious viruses to be transferred to new hosts in the laboratory.
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  • Date Issued: 2016

Keeping it in the family: coevolution of latrunculid sponges and their dominant bacterial symbionts

  • Authors: Matcher, Gwynneth F , Waterworth, Samantha C , Walmsley, Tara A , Matsatsa, Tendayi , Parker-Nance, Shirley , Davies-Coleman, Michael T , Dorrington, Rosemary A
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/65603 , vital:28818 , https://doi.org/10.1002/mbo3.417
  • Description: publisher version , The Latrunculiidae are a family of cold water sponges known for their production of bioactive pyrroloiminoquinone alkaloids. Previously it was shown that the bacterial community associated with a Tsitsikamma sponge species comprises unusual bacterial taxa and is dominated by a novel Betaproteobacterium. Here, we have characterized the bacterial communities associated with six latrunculid species representing three genera (Tsitsikamma, Cyclacanthia, and Latrunculia) as well as a Mycale species, collected from Algoa Bay on the South African southeast coast. The bacterial communities of all seven sponge species were dominated by a single Betaproteobacterium operational taxonomic unit (OTU0.03), while a second OTU0.03 was dominant in the Mycale sp. The Betaproteobacteria OTUs from the different latrunculid sponges are closely related and their phylogenetic relationship follows that of their hosts. We propose that the latrunculid Betaproteobacteria OTUs are members of a specialized group of sponge symbionts that may have coevolved with their hosts. A single dominant Spirochaetae OTU0.03 was present in the Tsitsikamma and Cyclacanthia sponge species, but absent from the Latrunculia and Mycale sponges. This study sheds new light on the interactions between latrunculid sponges and their bacterial communities and may point to the potential involvement of dominant symbionts in the biosynthesis of the bioactive secondary metabolites. , This research was supported by a SARChI grant from the South African National Research Foundation (NRF, GUN: 87583) and the Rhodes University Sandisa Imbewu Programme. S. C. W. was supported by an NRF Innovation PhD Scholarship and a Rhodes University Henderson PhD Scholarship. T. A. W. was supported by PhD Fellowships from the NRF and the German Academic Exchange Service (DAAD)
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  • Date Issued: 2016

Latrunculid sponges, their microbial communities and secondary metabolites: connecting conserved bacterial symbionts to pyrroloiminoquinone production

  • Authors: Dorrington, Rosemary A , Hilliar, Storm Hannah , Kalinski, Jarmo-Charles J , Krause, Rui W M , McPhail, Kerry L , Parker-Nance, Shirley , Wlalmsley, Tara A , Waterworth, Samantha C
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/65915 , vital:28858 , https://doi.org/10.1055/s-0036-1596655
  • Description: publisher version , The Latrunculiidae are cold water sponges known for their production of bioactive pyrroloiminoquinone alkaloids (e.g. makaluvamines, discorhabdins and tsitsikammamines). Since pyrroloiminoquinones have also been isolated from sponges belonging to other families, ascidians and microorganisms, the biosynthetic origin of these alkaloids in latrunculid sponges is likely microbial. This study focuses on the secondary metabolites produced by closely-related Tsitsikamma species and Cyclacanthia bellae, all latrunculid sponges endemic to Algoa Bay on the South African southeast coast. The sponges produced suites of related pyrroloiminoquinones, including tsitsikammine A and B, and discohabdin C and V, the combination and relative abundance of which is species-specific. Characterisation of the diversity of sponge-associated bacterial communities revealed the unprecedented conservation of two dominant bacterial species. The first, a Betaproteobacterium, is also found in other latrunculids and related sponge families, representing a novel clade of sponge endosymbionts that have co-evolved with their hosts. The second conserved bacterial symbiont is a spirochaete found only in Cyclacanthia and Tsitsikamma species that is likely to have been recruited from free-living spirochaetes in the environment. This study sheds new light on the interactions between latrunculid sponges, their dominant bacterial symbionts, and the potential involvement of these bacteria in pyrroloiminoquinone biosynthesis.
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  • Date Issued: 2016

SEAmester – South Africa’s first class afloat

  • Authors: Ansorge, Isabelle J , Brundrit, Geoff , Brundrit, Jean , Dorrington, Rosemary A , Fawcett, Sarah , Gammon, David , Henry, Tahlia , Hermes, Juliet , Hölscher, Beate , d’Hotman, Jethan , Meiklejohn, Ian , Morris, Tammy , Pinto, Izidine , Du Plessis, Marcel , Roman, Raymond , Saunders, Clinton , Shabangu, Fannie W , De Vos, Marc , Walker, David R , Louw, Gavin
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/65539 , vital:28808 , https://doi.org/10.17159/sajs.2016/a0171
  • Description: publisher version , From Introduction: Marine science is a highly competitive environment. The need to improve the cohort of South African postgraduates, who would be recognised both nationally and internationally for their scientific excellence, is crucial. It is possible to attract students early on in their careers to this discipline via cutting-edge science, technology and unique field experiences. Through the engagement of students with real-life experiences such as SEAmester, universities supporting marine science postgraduate degree programmes can attract a sustainable throughput of numerically proficient students. By achieving a more quantitative and experienced input into our postgraduate degree programmes, we will, as a scientific community, greatly improve our long-term capabilities to accurately measure, model and predict the impacts of current climate change scenarios. The short-term goal is to attract and establish a cohort of proficient marine and atmospheric science graduates who will contribute to filling the capacity needs of South African marine science as a whole. The SEAmester programme, by involving researchers from across all the relevant disciplines and tertiary institutions, provides an opportunity to build a network of collaborative teaching within the marine field. In doing so, these researchers will foster and strengthen new and current collaborations between historically white and black universities (Figure 1). The long-term objective of SEAmester is to build critical mass within the marine sciences to ensure sustained growth of human capacity in marine science in South Africa – aligning closely with the current DST Research and Development strategies and the Operation Phakisa Oceans Economy initiative.
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  • Date Issued: 2016

South Africa in the Antarctic Circumnavigation Expedition: a multi-institutional and interdisciplinary scientific project

  • Authors: Halo, Issufo , Dorrington, Rosemary A , Bornman, Thomas G , De Villiers, Stephanie , Fawcett, Sarah
  • Date: 2016
  • Language: English
  • Type: article
  • Identifier: http://hdl.handle.net/10962/65428 , vital:28790 , https://doi.org/10.17159/sajs.2016/a0173
  • Description: publisher version , The polar regions are more critically affected by climate change than any other region on our planet.1,2 On the Antarctic continent and in its surrounding oceans, the effects of climate change are likely to be dramatic,3 and include largescale catastrophic ice melt, loss of habitat and biodiversity, and global sea level rise. The ‘Southern Ocean’ refers to the region where Atlantic, Indian and Pacific Ocean waters come together to encircle Antarctica. These waters connect the different ocean basins by linking the shallow and deep limbs of the global ocean current system (‘overturning circulation’) and play a critical role in storing and distributing heat and carbon dioxide (CO2 ). The Southern Ocean thus regulates not only the climate of the Antarctic, but of the entire earth system.1,4 By extension, the capacity of the global ocean to ameliorate earth’s changing climate is strongly controlled by the Southern Ocean. Marine phytoplankton (microscopic plants inhabiting the sunlit upper ocean) convert CO2 (an inorganic form of carbon) dissolved in surface waters into organic carbon through photosynthesis. This organic carbon fuels upper trophic levels such as fish, mammals and birds, and a portion sinks into the deep ocean where it remains stored for hundreds to thousands of years. This mechanism, which lowers the atmospheric concentration of CO2 , is termed the ‘biological pump’.5 The efficiency of the global ocean’s biological pump is currently limited by the Southern Ocean, where the macronutrients (nitrate and phosphate) required for photosynthesis are never fully consumed in surface waters. In theory, increased consumption of these nutrients could drive higher organic carbon removal to the deep ocean, enhancing the oceanic uptake of atmospheric CO2 . Indeed, more complete consumption of Southern Ocean nutrients is a leading hypothesis for the decrease in atmospheric CO2 that characterised the ice ages.6 Despite the global importance of the Southern Ocean, knowledge of the controls on and interactions among the physical, chemical and biological processes operating in Antarctic ecosystems is limited, largely because of a scarcity of in-situ observational data, compounded by the challenge of integrating siloed scientific fields. Given predictions that diverse aspects of Southern Ocean physics and carbon biogeochemistry are likely to change in the coming decades, a transdisciplinary approach to studying Antarctic systems is critical.
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  • Date Issued: 2016

Stromatolite microbial communities as a source of new bioactive secondary metabolites

  • Authors: Flatt, P M , Damarjanan, C , Isamonger, E , Kalinski, Jarmo-Charles J , Dorrington, Rosemary A , McPhail, Kerry L
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/65871 , vital:28851 , https://doi.org/10.1055/s-0036-1596638
  • Description: publisher version , Stromatolites represent some of the earliest microbial communities on Earth. They are formed by accretion and precipitation of layered calcium carbonate structures that result from the metabolic activity of complex microbial communities and the geochemical conditions of their environment. Modern stromatolite communities include aerobic heterotrophs, sulphide-oxidizing bacteria, sulphate-reducing bacteria, fermentative bacteria and cyanobacteria. Phylogenetic analyses revealed the presence of new and known cyanobacterial taxa related to known producers of biologically active secondary metabolites in tufa stromatolites along the South African southeast coast [1]. Prompted us to investigate their potential for producing novel bioactive secondary metabolites. A series of three tide pools provided the opportunity to collect stromatolites along a vertical transect from pool A (highest elevation, low nitrogen input, fresh water), pool B (within high tide zone, brackish water) and pool C (within tidal zone). The microbial community in pool A is particularly distinct. Chemical extracts of stromatolites from different pools have been profiled by LC-MS/MS and the data subjected to molecular spectral networking using the GnPS platform [2] in order to establish the diversity and biological potential of the microbial metabolome that is being expressed within each of these microhabitats. Correlation of the phylogenetic and secondary metabolomic data is expected to guide the isolation of new natural products with biomedical relevance.
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  • Date Issued: 2016

Tufa stromatolite ecosystems on the South African south coast

  • Authors: Perissinotto, Renzo , Bornman, Tommy G , Steyn, Paul-Pierre , Miranda, Nelson A F , Dorrington, Rosemary A , Matcher, Gwynneth F , Strydom, Nadine A , Peer, Nasreen
  • Date: 2014
  • Language: English
  • Type: Article
  • Identifier: vital:6490 , http://hdl.handle.net/10962/d1014585 , http://dx.doi.org/10.1590/sajs.2014/20140011
  • Description: Following the first description of living marine stromatolites along the South African east coast, new investigations along the south coast have revealed the occurrence of extensive fields of actively calcifying stromatolites. These stromatolites have been recorded at regular distances along a 200-km stretch of coastline, from Cape Recife in the east to the Storms River mouth in the west, with the highest density found between Schoenmakerskop and the Maitland River mouth. All active stromatolites are associated with freshwater seepage streams flowing from the dune cordon, which form rimstone dams and other accretions capable of retaining water in the supratidal platform. Resulting pools can reach a maximum depth of about 1 m and constitute a unique ecosystem in which freshwater and marine organisms alternate their dominance in response to vertical mixing and the balance between freshwater versus marine inflow. Although the factors controlling stromatolite growth are yet to be determined, nitrogen appears to be supplied mainly via the dune seeps. The epibenthic algal community within stromatolite pools is generally co-dominated by cyanobacteria and chlorophytes, with minimal diatom contribution.
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  • Date Issued: 2014

The African coelacanth genome provides insights into tetrapod evolution:

A broad host range reporter plasmid for the analysis of divergent promoter regions

  • Authors: Jiwaji, Meesbah , Matcher, Gwynneth F , Dorrington, Rosemary A
  • Date: 2008
  • Language: English
  • Type: Article
  • Identifier: vital:6476 , http://hdl.handle.net/10962/d1006164 , http://www.scielo.org.za/scielo.php?pid=S0038-23532008000400013&script=sci_arttext
  • Description: Although many vectors exist for Escherichia coli and closely related species, there are few broad host range vectors that can be conjugated into a large variety of Gram-negative bacteria. We have constructed a broad host range vector, pMJ445, that facilitates the analysis of divergent promoters in Gram-negative bacteria. The vector was validated using two intergenic regions derived from gene clusters involved in hydantoin hydrolysis, from the environmental isolates Pseudomonas putida and Agrobacterium tumefaciens. The DNA sequences analysed were capable of activating expression of the reporter enzymes, β-glucuronidase and β-galactosidase, present on pMJ445, indicating the presence of divergent promoters in the sequences selected. In addition, we demonstrated that pMJ445 can be applied to gene regulation studies.
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  • Date Issued: 2008

Characterization of a succession of small insect viruses in a wild South African population of Nudaurelia cytherea capensis (Lepidoptera: Saturniidae)

  • Authors: Walter, Cheryl T , Tomasicchio, Michelle , Hodgson, V , Hendry, Donald A , Hill, Martin P , Dorrington, Rosemary A
  • Date: 2008
  • Language: English
  • Type: Article
  • Identifier: vital:6474 , http://hdl.handle.net/10962/d1006161 , http://www.scielo.org.za/scielo.php?pid=S0038-23532008000200015&script=sci_arttext
  • Description: The Tetraviridae are a family of small insect RNA viruses first discovered in South Africa some 40 years ago. They consist of one or two single-stranded (+) RNAs encapsidated in an icosahedral capsid of approximately 40 nm in diameter, with T = 4 symmetry. The type members of the two genera within this family, Nudaurelia β virus (NβV) and Nudaurelia ω virus (NωV), infect Nudaurelia cytherea capensis (pine emperor moth) larvae. The absence of N. capensis laboratory colonies and tissue culture cell lines susceptible to virus infection have limited research on the biology of NβV and NωV because the availability of infectious virus is dependent upon sporadic outbreaks in the wild N. capensis populations. In September 2002, dead and dying N. capensis larvae exhibiting symptoms similar to those reported previously in other tetravirus infections were observed in a wild population in a pine forest in the Western Cape province of South Africa. We report here the isolation of three small insect viruses from this population over a period of three years. Transmission electron microscopy and serological characterization indicate that all three are tetra-like virus isolates. One isolate was shown by cDNA sequence analysis to be NβV, which was thought to have been extinct since 1985. The two other isolates are likely new tetraviruses, designated Nudaurelia ψ virus (NψV) and Nudaurelia ζ virus (NζV), which are morphologically and serologically related to NωV and NβV, respectively.
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  • Date Issued: 2008

Molecular biology studies on the coelacanth: a review

  • Authors: Modisakeng, Keoagile W , Amemiya, Chris T , Dorrington, Rosemary A , Blatch, Gregory L
  • Date: 2006
  • Language: English
  • Type: Article
  • Identifier: vital:6466 , http://hdl.handle.net/10962/d1005795
  • Description: The discovery of the African coelacanth in 1938 and subsequently the Indonesian coelacanth in 1998 has resulted in a keen interest in molecular studies on the coelacanth. A major focus has been on the phylogenetic position of the coelacanth. Lobe-finned fish such as the coelacanth are thought to be at the base of the evolutionary branch of fish leading to tetrapods. These studies have further aimed to resolve the phylogenetic relationship of extant lobe-finned fish (two coelacanth species and the lungfishes) to vertebrates. Notwithstanding the lack of readily accessible good-quality coelacanth tissue, several major contributions to coelacanth molecular studies and biology have been possible. The mitochondrial genome sequences of both species of the coelacanth suggest that they diverged from one another 40–30 million years ago. A number of large gene families such as the HOX, protocadherin and heat shock protein clusters have been characterized. Furthermore, the recent successful construction of a large-insert (150–200 kilobase) genomic library of the Indonesian coelacanth will prove to be an invaluable tool in both comparative and functional genomics. Here we summarize and evaluate the current status of molecular research, published and databased, for both the African (Latimeria chalumnae) and the Indonesian (Latimeria menadoensis) coelacanth.
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  • Date Issued: 2006

Isolation of genes encoding heat shock protein 70 (hsp70s) from the coelacanth, Latimeria chalumnae

  • Authors: Modisakeng, Keoagile W , Dorrington, Rosemary A , Blatch, Gregory L
  • Date: 2004
  • Language: English
  • Type: Article
  • Identifier: vital:6459 , http://hdl.handle.net/10962/d1005788
  • Description: Under stress conditions, proteins unfold or misfold, leading to the formation of aggregates. Molecular chaperones can be defined as proteins that facilitate the correct folding of other proteins, so that they attain a stable tertiary structure. In addition, they promote the refolding and degradation of denatured proteins after cellular stress. Heat shock proteins form one of the main classes of molecular chaperones. We are interested in determining if the genome of the coelacanth (Latimeria chalumnae) encodes a heat shock protein-based cytoprotection mechanism. We have isolated 50 kb and larger coelacanth genomic DNA from frozen skin tissue of L. chalumnae. From the alignments of several fish Hsp70 proteins, conserved regions at the N- and C-termini were identified. Codon usage tables were constructed from published coelacanth genes and degenerate primers were designed to isolate the full-length hsp70 gene and regions encoding the ATPase and the peptide binding domains. Since it is known that the tilapia and Fugu inducible hsp70 genes are intronless, we proceeded on the assumption that a coelacanth inducible hsp70 would also be intronless. A large fragment (1840 bp) encoding most of a coelacanth Hsp70 protein, and two partial fragments encoding a coelacanth Hsp70ATPase domain (1048 bp) and peptide binding domain (873 bp), were isolated by polymerase chain reaction amplification. Protein sequences translated from all the nucleotide sequences were closely identical to typical Hsp70s. This is the first study to provide evidence for a cytoprotection mechanism in the coelacanth involving an inducible Hsp70.
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  • Date Issued: 2004
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