A carbonate-banded iron formation transition in the Early Protorezoicum of South Africa

Seven new and two resurveyed stratigraphic sections through the important carbonate-BIF transition in Griqualand West are presented and compared with six published sections. Lateral correlation within this zone is attempted but the variability was found to be too great for meaningful subdivision. Substantial lithological irregularity is the only unifying character of this zone, for which the new name Finsch Member (Formation) is proposed. Vertical and lateral lithological variations as well as chemical changes across this zone are discussed with reference to environmental aspects. Local and regional considerations lead to the conclusion that fresh water-sea water mixing occurred in a shallowing basin

Paleomagnetism of a lateritic paleoweathering horizon and overlying Paleoproterozoic red beds from South Africa: Implications for the Kaapvaal apparent polar wander path and a confirmation of atmospheric oxygen enrichment

The Olifantshoek Group in southern Africa contains Paleoproterozoic red beds that are exceptionally well preserved, lying unconformably atop a regionally extensive lateritic paleoweathering profile. We studied the basal unit of this succession, known as the Gamagara or Mapedi Formation, and the lateritized substrate (so-called “Drakenstein” or “Wolhaarkop” paleosol) on which it developed. Two ancient magnetic components are observed. One (INT), usually with a distributed unblocking spectrum between 300° and 600°C but occasionally persisting to >675°C, is directed shallowly southward or northward. A mesoscale fold test at South Sishen Mine indicates that this component was acquired during deformation; similarity of the direction to previous results suggests that it was acquired at ∼1240 Ma, during early Namaqua orogenesis. Combining our INT results with existing data from the Namaqua eastern zone (NEZ), we calculate the NEZ pole at (44.9°N, 021.5°E, K = 23.2, A_95 = 12.8°, Q = 5). The most stable component from our data set (HIG), always persisting as a nonzero endpoint to demagnetization at >665°–680°C, is observed in 32 samples from South Sishen and Beeshoek Mines. Directed moderately east-downward (Sishen) or west-upward (Beeshoek), this component predates the mesoscale fold at Sishen. More importantly, a conglomerate test at Beeshoek indicates that HIG was acquired prior to Paleoproterozoic deposition of the Gamagara/Mapedi Formation. The concordance between directions from the paleoweathering zone and immediately overlying red beds indicates that HIG is a primary magnetic remanence for the basal Gamagara/Mapedi (BGM) Formation. The dual-polarity BGM paleomagnetic pole (02.2°N, 081.9°E, dp = 7.2°, dm = 11.5°, Q = 6) lies neatly between previous Kaapvaal poles with ages of ∼2220 (Ongeluk lavas) and 2060 Ma (Bushveld complex). Our data thus support recent correlations of the Gamagara/Mapedi Formation with pre-Bushveld sediments of the Pretoria Group. A pre-Bushveld age for BGM is also consistent with its substantial distance from a new, albeit less reliable, paleomagnetic pole from the ∼1930-Ma Hartley lavas, higher within the Olifantshoek succession (12.5°N, 332.8°E, K = 18.6, A95 = 16.0°, Q = 3). Our conglomerate test at Beeshoek confirms previous allegations that the intense hematitization observed in the Drakenstein-Wolhaarkop paleosol occurred during Paleoproterozoic weathering under a highly oxygenated atmosphere

Evaluation of Antibacterial Activity of Bryopsis pennata and Chaetomorpha antennina against Multidrug Resistant Morganella morganii and Salmonella species Isolated from Healthy Individuals

The problem of antibiotic resistance is fast becoming a pandemic which has necessitated the need for new drugs discovery. This study was carried out to screen two green algal species- Bryopsis pennata and Chaetomorpha anteninna for antibacterial activity against multidrug resistant pathogenic enteric organisms (Morganella morganii and Salmonella species) obtained from healthy individuals. Algal samples were obtained and processed. Crude extraction was carried out with dichloromethane/methanol (2:1) while the antibacterial screening was done by agar-well diffusion method. Results revealed that M. morganii was 3.37% of the total isolates recovered while Salmonella species was 6.74%. Result also showed that C. antennina was active against all the strains of Salmonella species with inhibitory zones ranging from 10 mm to 17 mm and the M. morganii with inhibitory zone of 11 mm while B. pennata showed inhibitory activities against only S. pullorum and S. enterica subspecies diarizonae with inhibitory zones of 12 mm and 7 mm respectively as well as the M. morganii strain with 14 mm. The antibacterial activities observed from these green algae showed that Bryopsis pennata and Chaetomorpha antennina from the West African coast are promising in the quest for new drugs with potentials against multidrug resistant strains of bacteria and therefore should be intensely researched int

Assessment of potential anti-cancer stem cell activity of marine algal compounds using an in vitro mammosphere assay

Background: The cancer stem cell (CSC) theory proposes that tumours arise from and are sustained by a subpopulation of cells with both cancer and stem cell properties. One of the key hallmarks of CSCs is the ability to grow anchorage-independently under serum-free culture conditions resulting in the formation of tumourspheres. It has further been reported that these cells are resistant to traditional chemotherapeutic agents. Methods: In this study, the tumoursphere assay was validated in MCF-7 cells and used to screen novel marine algal compounds for potential anti-cancer stem cell (CSC) activity in vitro. Results: MCF-7 breast cancer cells were observed to generate tumourspheres or mammospheres after 3-5 days growth in anchorage-independent conditions and an apparent enrichment in potential CSCs was observed by an increase in the proportion of CD44high/CD24low marker-bearing cells and Oct4 expression compared to those in the bulk population grown in regular adherent conditions. Using this assay, a set of algal metabolites was screened for the ability to inhibit mammosphere development as a measure of potential anti-CSC activity. We report that the polyhalogenated monoterpene stereoisomers RU017 and RU018 isolated from the red alga Plocamium cornutum, both of which displayed no cytotoxicity against either adherent MCF-7 breast cancer or MCF-12A non-transformed breast epithelial cells, were able to prevent MCF-7 mammosphere formation in vitro. On the other hand, neither the brown algal carotenoid fucoxanthin nor the chemotherapeutic paclitaxel, both of which were toxic to adherent MCF-7 and MCF-12A cells, were able to inhibit mammosphere formation. In fact, pre-treatment with paclitaxel appeared to enhance mammosphere formation and development, a finding which is consistent with the reported resistance of CSCs to traditional chemotherapeutic agents. Conclusion: Due to the proposed clinical significance of CSC in terms of tumour initiation and metastasis, the identification of agents able to inhibit this subpopulation has clinical significance

Depth-dependent δ13 C trends in platform and slope settings of the Campbellrand-Malmani carbonate platform and possible implications for Early Earth oxygenation

Highlights • Carbon cycle of Neoarchean carbonate platform and potential oxygen oasis. • Carbon isotopes reveal a shift to aerobic biosphere and increasing oxidation state. • Rare earth element patterns reveal decrease in open ocean water influx. • Rimmed margin architecture was crucial for evolution of aerobic ecosystems. Abstract The evolution of oxygenic photosynthesis is widely seen as the major biological factor for the profound shift from reducing to slightly oxidizing conditions in Earth’s atmosphere during the Archean-Proterozoic transition period. The delay from the first biogenic production of oxygen and the permanent oxidation of Earth’s atmosphere during the early Paleoproteorozoic Great Oxidation Event (GOE) indicates that significant environmental modifications were necessary for an effective accumulation of metabolically produced oxygen. Here we report a distinct temporal shift to heavier carbon isotope signatures in lagoonal and intertidal carbonates (δ13Ccarb from -1.6 to +0.2 ‰, relative to VPDB) and organic matter (δ13Corg from about -40 to -25 ‰, relative to VPDB) from the 2.58–2.50 Gy old shallow–marine Campbellrand-Malmani carbonate platform (South Africa). This indicates an increase in the burial rate of organic matter caused by enhanced primary production as well as a change from an anaerobic to an aerobic ecosystem. Trace element data indicate limited influx of reducing species from deep open ocean water into the platform and an increased supply of nutrients from the continent, both supporting primary production and an increasing oxidation state of the platform interior. These restricted conditions allowed that the dissolved inorganic carbon (DIC) pool in the platform interior developed differently than the open ocean. This is supported by coeval carbonates from the marginal slope setting, which had a higher interaction with open ocean water and do not record a comparable shift in δ13Ccarb throughout the sequence. We propose that the emergence of stable shallow-water carbonate platforms in the Neoarchean provided ideal conditions for the evolution of early aerobic ecosystems, which finally led to the full oxidation of Earth’s atmosphere during the GOE

Size-resolved characteristics of inorganic ionic species in atmospheric aerosols at a regional background site on the South African Highveld

Aerosols consist of organic and inorganic species, and the composition and concentration of these species depends on their sources, chemical transformation and sinks. In this study an assessment of major inorganic ions determined in three aerosol particle size ranges collected for 1year at Welgegund in South Africa was conducted. SO42- and ammonium (NH4+) dominated the PM1 size fraction, while SO42- and nitrate (NO3) dominated the PM1-2.5 and PM2.5-10 size fractions. SO42- had the highest contribution in the two smaller size fractions, while NO3- had the highest contribution in the PM2.5-10 size fraction. SO42- and NO3- levels were attributed to the impacts of aged air masses passing over major anthropogenic source regions. Comparison of inorganic ion concentrations to levels thereof within a source region influencing Welgegund, indicated higher levels of most species within the source region. However, the comparative ratio of SO42- was significantly lower due to SO42- being formed distant from SO2 emissions and submicron SO42- having longer atmospheric residencies. The PM at Welgegund was determined to be acidic, mainly due to high concentrations of SO42-. PM1 and PM1-2.5 fractions revealed a seasonal pattern, with higher inorganic ion concentrations measured from May to September. Higher concentrations were attributed to decreased wet removal, more pronounced inversion layers trapping pollutants, and increases in household combustion and wild fires during winter. Back trajectory analysis also revealed higher concentrations of inorganic ionic species corresponding to air mass movements over anthropogenic source regions.Peer reviewe

Size-resolved characteristics of inorganic ionic species in atmospheric aerosols at a regional background site on the South African Highveld

Aerosols consist of organic and inorganic species, and the composition and concentration of these species depends on their sources, chemical transformation and sinks. In this study an assessment of major inorganic ions determined in three aerosol particle size ranges collected for 1year at Welgegund in South Africa was conducted. SO42- and ammonium (NH4+) dominated the PM1 size fraction, while SO42- and nitrate (NO3) dominated the PM1-2.5 and PM2.5-10 size fractions. SO42- had the highest contribution in the two smaller size fractions, while NO3- had the highest contribution in the PM2.5-10 size fraction. SO42- and NO3- levels were attributed to the impacts of aged air masses passing over major anthropogenic source regions. Comparison of inorganic ion concentrations to levels thereof within a source region influencing Welgegund, indicated higher levels of most species within the source region. However, the comparative ratio of SO42- was significantly lower due to SO42- being formed distant from SO2 emissions and submicron SO42- having longer atmospheric residencies. The PM at Welgegund was determined to be acidic, mainly due to high concentrations of SO42-. PM1 and PM1-2.5 fractions revealed a seasonal pattern, with higher inorganic ion concentrations measured from May to September. Higher concentrations were attributed to decreased wet removal, more pronounced inversion layers trapping pollutants, and increases in household combustion and wild fires during winter. Back trajectory analysis also revealed higher concentrations of inorganic ionic species corresponding to air mass movements over anthropogenic source regions.Peer reviewe

Management for improved water use efficiency in the dry areas of Africa and West Asia: proceedings of a Workshop, Ankara, Turkey, 22-26 Apr 2002

This is a report of the 2002 workshop of the Optimizing Soil Water Use (OSWU) Consortium, held in Ankara, Turkey. It describes OSWU research in West Asia (Jordan, Syria, Turkey), North Africa (Morocco), Southern Africa (South Africa, Zimbabwe), and West Africa (Burkina Faso, Niger). The consortium aims at developing and disseminating effective and practical solutions for resource-poor farmers, being aware of the uncertainties of applying classical principles of soil-crop- water relations in arid and semi-arid environments. Reports from Morocco, Turkey, Jordan and South Africa confirm the effectiveness of some existing technologies, including the use of mulches to reduce soil evaporation or runoff, sometimes combined with use of soil fertility inputs to improve water use efficiency. Other papers describe a new quality indicator to assess land degradation, the use of new decision support tools, and modeling techniques to improve research efficiency and increase the effectiveness of farmer participatory research. ICARDA and ICRISAT report on new developments within the international research centers that are now ready for testing by NARS partners in their environments. Proposals for new work were presented and approved, with the emphasis on better transfer of methods to improve soil water use, and evaluating the impact of past research projects. In recognition of the current turbulent times, and the unlikelihood of increased resources for agricultural research in dry areas, OSWU partners developed a strategic plan to achieve greater impact; this plan is outlined

Synergy between EngE, XynA and ManA from Clostridium cellulovorans on corn stalk, grass and pineapple pulp substrates

The synergistic interaction between various hemi/cellulolytic enzymes has become more important in order to achieve effective and optimal degradation of complex lignocellulose substrates for biofuel production. This study investigated the synergistic effect of three enzymes endoglucanase (EngE), mannanase (ManA) and xylanase (XynA) on the degradation of corn stalk, grass, and pineapple fruit pulp and determined the optimal degree of synergy between combinations of these enzymes. It was established that EngE was essential for degradation of all of the substrates, while the hemicellulases were able to contribute in a synergistic fashion to increase the activity on these substrates. Maximum specific activity and degree of synergy on the corn stalk and grass was found with EngE:XynA in a ratio of 75:25%, with a specific activity of 41.1 U/mg protein and a degree of synergy of 6.3 for corn stalk, and 44.1 U/mg protein and 3.4 for grass, respectively. The pineapple fruit pulp was optimally digested using a ManA:EngE combination in a 50:50% ratio; the specific activity and degree of synergy achieved were 52.4 U/mg protein and 2.7, respectively. This study highlights the importance of hemicellulases for the synergistic degradation of complex lignocellulose. The inclusion of a mannanase in an enzyme consortium for biomass degradation should be examined further as this study suggests that it may play an important, although mostly overlooked, role in the synergistic saccharification of lignocellulose