>Magister Scientiae - MSc / Salt pans are a characteristic feature of many dry deserts. The microbial communities inhabiting salt pans are thought to be particularly complex and are generally dominated by halophilic microorganisms. Although saline pools are frequently found within the hyper-arid Namib Desert, the microbial communities of these saline sites have been scarcely investigated. The aim of the present study was to characterise the archaeal, bacterial and cyanobacterial diversity inhabiting these extreme saline pools using three culture independent molecular techniques (DGGE, T-RFLP and 16S rRNA clone libraries). The physiochemical results, mainly the conductivity readings recorded from the sampling sites, indicated that the Gobabeb (103.0mS/cm) region was less saline than the two Swakopmund [(Sps01) (150.0mS/cm) and Sps02 (180.0mS/cm)] sites. Results obtained from DGGE and T-RFLP data were in agreement for both bacterial and cyanobacterial analysis indicating that the Gobabeb site was more diverse than the two Swakopmund sites (Sps01 and Sps02). In comparison, the archaeal community profiles for DGGE and T-RFLP analysis were in agreement illustrating that the archaeal community were more abundant in the two extreme Swakopmund saline sites. Phylogenetic data obtained from 16S rRNA gene clone libraries identified halophilic phylotypes (Rhodothermaceae, Idiomarinaceae Puniceicoccaceae and Cyanobacteria/Chloroplast, Family VII) normally associated with salt rich sites. In addition, a large number of unclassified taxa were identified. To conclude, the study highlighted the presence of a rich microbial diversity present within the salt pans of the Namib Desert and establishes a platform for future investigations. / National Research Foundation

Coryphantha scheeri var. robustispina (Schott) L. Benson, the Pima pineapple cactus, herein referred to as C. scheeri, was declared an endangered species in 1993 and only occurs in a limited range in Arizona, USA and northern Sonora, Mexico between 2,300'-4,500' asl. Development within the range of C. scheeri threatens individuals, but transplanting to conserve them while allowing for development has been considered to be ineffective for conservation due to low post-transplant survival rates in past studies. The construction of a natural gas pipeline provided the opportunity to conduct a transplant experiment on 82 individual C. scheeri transplanted in July and August 2014. The plants were randomized into one of four transplant methods: bare-root with supplemental water, bare-root without supplemental water, soil-and-plant moved with supplemental water, and soil-and-plant moved without supplemental water. Higher than average precipitation occurred during the 2014 monsoon season including after transplanting. A subset of the transplanted C. scheeri (n=17) were transplanted back onto the pipeline after pipeline construction was completed. Survival rates were monitored through December 2016 and compared to undisturbed C. scheeri near the pipeline ROW and those on other sites. For the plants transplanted once, no significant effect of moving the plants with soil compared to no soil (X2 = 2.9, p = 0.09), no significant effect of adding water at the time of transplant compared to not adding water (X2 = 1.2, p = 0.26), and no significant interaction among treatments (X2 = 0.06, p = 0.81) was observed. For plants transplanted twice, a significant effect of moving the plants with the soil compared to no soil (X2 = 5.0, p = 0.02) was found, while due to the random selection of plants to be transplanted twice there was too little data to adequately test other comparisons. There was no significant difference in mortality between the transplanted once (27% mortality) and the transplanted twice (31% mortality) treatments (p = 0.78), but there was a significant difference between transplanted and non-transplanted plants (2% mortality in non-transplanted plants; p < 0.05). Soil series did not appear correlated with mortality. Plants in good condition (scored 4 or 5 on scale of 0-5) at the time of transplanting had low mortality rates (16%) while plants scored 3 or lower had high mortality rates (60%) but deaths did not occur immediately after transplanting: 5 died after 8 or 9 months, 4 after 13-16 months, and 9 after 23 or 24 months. The majority of the deaths occurred after numerous months of declining in condition but six plants died suddenly. Good condition plants were more likely to flower than those in poor condition. Transplanting appears to conserve some of the C. scheeri population which would have otherwise been lost to development.

Global deserts occupy one-third of the Earth's surface and contribute significantly to organic carbon storage, a process at risk in dryland ecosystems that are highly vulnerable to climate-driven ecosystem degradation. The forces controlling desert ecosystem degradation rates are poorly understood, particularly with respect to the relevance of the arid-soil microbiome. Here we document correlations between increasing aridity and soil bacterial and archaeal microbiome composition along arid to hyperarid transects traversing the Atacama Desert, Chile. A meta-analysis reveals that Atacama soil microbiomes exhibit a gradient in composition, are distinct from a broad cross-section of nondesert soils, and yet are similar to three deserts from different continents. Community richness and diversity were significantly positively correlated with soil relative humidity (SoilRH). Phylogenetic composition was strongly correlated with SoilRH, temperature, and electrical conductivity. The strongest and most significant correlations between SoilRH and phylum relative abundance were observed for Acidobacteria, Proteobacteria, Planctomycetes, Verrucomicrobia, and Euryarchaeota (Spearman's rank correlation [r(s)] = >0.81; false-discovery rate [q] = <= 0.005), characterized by 10- to 300-fold decreases in the relative abundance of each taxon. In addition, network analysis revealed a deterioration in the density of significant associations between taxa along the arid to hyperarid gradient, a pattern that may compromise the resilience of hyperarid communities because they lack properties associated with communities that are more integrated. In summary, results suggest that arid-soil microbiome stability is sensitive to aridity as demonstrated by decreased community connectivity associated with the transition from the arid class to the hyperarid class and the significant correlations observed between soilRH and both diversity and the relative abundances of key microbial phyla typically dominant in global soils. IMPORTANCE We identify key environmental and geochemical factors that shape the arid soil microbiome along aridity and vegetation gradients spanning over 300 km of the Atacama Desert, Chile. Decreasing average soil relative humidity and increasing temperature explain significant reductions in the diversity and connectivity of these desert soil microbial communities and lead to significant reductions in the abundance of key taxa typically associated with fertile soils. This finding is important because it suggests that predicted climate change-driven increases in aridity may compromise the capacity of the arid-soil microbiome to sustain necessary nutrient cycling and carbon sequestration functions as well as vegetative cover in desert ecosystems, which comprise one-third of the terrestrial biomes on Earth.

5 pp. / Chia seeds are a popular food lately, which people have deemed as a superfood. Chia seeds are rich source of many vitamins and minerals as well as omega-3 fatty acids and fiber. This article explores the history of chia seeds, the nutritional benefits, as well as illustrates some ways to include this food into your diet.

Cette étude examine la place que les peuples situés à l’ouest de la Vallée du Nil occupent dans la culture pharaonique depuis les premières sources dynastiques jusqu’à la fin du Moyen Empire (3150-1800 av. J.-C.). Le sujet est abordé de manière thématique, d’un point de vue archéologique, historique et linguistique. Après avoir délimité l’espace dans lequel ces peuples évoluent et déterminé leurs différentes représentations dans les sources égyptiennes, il s’agit de mettre en évidence la nature des relations qu’ils entretiennent avec les habitants de la vallée. L’enjeu est de saisir la manière dont ces « Libyens » sont perçus et reconnus dans la société égyptienne. / The present study concentrates on the position of the people living west to the Nile Valley in the Pharaonic culture since the first dynastic sources until the end of the Middle Kingdom. The subject has been thematically organized, from an archaeological, historical and linguistic point of view. After having outlined their geographical area where they have lived and having determined their various representations in the Egyptian sources, the aim if this research is to highlight the nature of the relations they maintained with the inhabitants of the Nile Valley. The goal is to understand how these “Libyans” are perceived and recognized in the Egyptian society.

Previous studies on the regulation of salt and water reabsorption in the insect excretory system have concentrated on the rectum, while regulation of the ileum has received little attention. Cl⁻ transport is the predominant ion transport process in both the ileum and rectum of the desert locust and drives fluid absorption. The central nervous system (CNS) was surveyed for factors which stimulate Cl⁻-dependent short-circuit current (I[formula omitted]) using in vitro flat sheet preparations of locust ileum as a bioassay. All ganglia extracts tested (except the corpora allata) caused significant increases in ileal I[formula omitted]. Extracts of muscle tissue, used as a control, had no effect on ileal I[formula omitted] indicating that stimulants were not general metabolites present in locust tissue. Crude extracts of the corpus cardiacum (CC) and fifth ventral ganglion (VG5) stimulated ileal I[formula omitted] in a dose-dependent manner and both caused an increase in K⁺ and Na⁺ absorption as previously observed with cAMP. CC and VG5 had no effect on ileal NH₄⁺ secretion but both inhibited ileal H⁺ secretion. Most of the stimulatory effects of CC and VG were largely abolished by treatment with trypsin and chymotrypsin, suggesting that the stimulants were peptides. CC and VG5 factors were apparently separate compounds because they differed in the time courses of ileal I[formula omitted] response, thermal stability, and extraction properties. Reversed-phase high performance liquid chromatography (RP-HPLC) of water extracts of CC identified two distinct factors (fractions D and F) which stimulated ileal I[formula omitted] and a third factor (fraction G) which had little effect on I[formula omitted], but which caused a five-fold increase in ileal fluid transport (J[formula omitted]). None of these fractions increased rectal J[formula omitted]; moreover, fraction D stimulated rectal I[formula omitted] at higher doses. These results provided the first indication that separate stimulants act on locust rectum and ileum. The most potent factor in CC acting on ileal I[formula omitted] was isolated using a four-step purification procedure, utilizing C₈ and phenyl RP-columns for separation. Amino acid analysis of this purified peptide indicated a molecular weight of 7700 daltons and a near complete amino acid sequence (50 out of 65) was determined. The purified factor (S. gregaria ion transport peptide; ScgITP) was assayed on all ileal ion transport processes influenced by crude CC extracts. ScgITP caused quantitatively the same range of effects as crude CC extracts, in that it stimulated Cl⁻, K⁺, and Na⁺ reabsorption and inhibited H⁺ secretion. High doses of ScgITP (5 CC equiv.ml⁻¹) caused the same maximum response on all these systems as crude CC extracts (0.25 CC equiv.ml⁻¹). ScglTP is unlikely to be chloride transport stimulating hormone, previously reported to act on the rectum, because a maximum rectal I[formula omitted] response was not achieved and there was no effect on rectal J[formula omitted], which is Cl⁻-dependent. It appears that ScgITP acts through cAMP as the second messenger to stimulate reabsorptive processes because this cyclic nucleotide mimicked the actions of ScgITP and crude CC extracts. In support of this view, ileal I[formula omitted] was also stimulated to maximum levels by 5mM theophylline and 50μM forskolin. The inhibition of H⁺ secretion by ScgITP must occur through a different intracellular pathway because this action was not mimicked by cAMP. / Science, Faculty of / Zoology, Department of / Graduate

The cellular mechanisms responsible for rectal acidification in the desert locust, Schistocerca gregaria, were investigated in isolated recta mounted as flat sheets in modified Ussing chambers. In the absence of exogenous CO₂, HCO₃⁻, and phosphate, the isolated rectum (under both open- and short-circuit current conditions) was capable of rates of net acid secretion (J[subscript]H+) similar to those observed in vivo, demonstrating the viability of the preparation and suggesting that rectal acidification was due to proton secretion rather than selective movements of HCO₃⁻ or phosphate. The possibility that trace levels of metabolic CO₂ might be generating sufficient HCO₃⁻ to account for the observed rates of rectal acidification (via HCO₃⁻ reabsorption) was assessed by adding exogenous CO₂/HCO₃⁻ to the contraluminal bath. The small increases in J[subscript]H+ observed after addition of 2% or 5% CO₂ were shown to be due to simple hydration of CO₂ which had diffused into the lumen (from the contraluminal bath), rather than changes in rates of HCO₃⁻ reabsorption. Since measurable quantities of luminal HCO₃⁻ did not directly affect the apical acid/base transport mechanism per se, it was concluded that metabolic CO₂ could not generate sufficient HCO₃⁻ in the lumen to account for the rates of rectal acidification observed under nominally CO₂/HCO₃⁻-free conditions and that J[subscript]H+ must be due to a proton secretory rather than bicarbonate reabsorptive mechanism. Microelectrode measurements of intracellular pH (pHi) and apical and basolateral membrane potentials (Va and Vb respectively) indicated that luminal pH was not in equilibrium with either contraluminal pH or pHi and that the mechanism responsible for active luminal acid secretion resided on the apical membrane. Preliminary measurements of bath total ammonia (ie. NH₃ + NH₄+) levels in the previous experiments suggested that the rectum was actively secreting ammonia at significant rates across the apical membrane into the lumen. If the ammonia crossed the apical membrane as NH₃ rather than NH₄+, rates of luminal ammonia secretion (J[subscript]Amm) would have to be added to J[subscript]H+ to obtain corrected values of luminal proton secretion. In the absence of exogenously added ammonia and CO₂, ammonia was preferentially secreted into the lumen under both open- and short-circuit current conditions. J[subscript]Amm was dependent on the presence of luminal amino acids and was relatively unaffected by K[superscript]+ removal or changes in luminal pH from 7.00 to 5.00. Bilateral Na+ substitution or luminal addition of ImM amiloride reduced J[subscript]Amm by 63% and 65% respectively. The data consistently demonstrate that the rectum secretes significant quantities of endogenously produced ammonia preferentially into the lumen as NH₄+ rather than NH₃ via an apical Na[superscript]+/NH₄[superscript]+ exchange mechanism. Clearly, rates of net acid secretion estimated by titratable acidity do not have to include a correction for luminal ammonia secretion. Although J[subscript]H+ was completely unaffected by changes in contraluminal pH, it could be progressively reduced (and eventually abolished) by imposition of either transepithelial pH gradients (lumen acid) or transepithelial electrical gradients (lumen positive). Under short-circuit current conditions, the bulk of J[subscript]H+ was not dependent on Na[superscript]+, K[superscript]+, CI⁻, Mg₂+, or Ca+ and was due to a primary electrogenic proton translocating mechanism located on the apical membrane. A small component (10-16%) of J[subscript]H+ measured under these conditions could be attributed to an apical amiloride-inhibitable Na[superscript]+/H[superscript]+ exchange mechanism. Inhibition of JH+ by anoxia or reduction of luminal pH unmasked a significant proton diffusional pathway on the apical membrane in parallel with the active proton pump. The fact that J[subscript]H+ was significantly inhibited (42%-66%) by contraluminal addition of ImM cAMP and relatively unaffected by changes in contraluminal pCO₂ or pH suggests that net acid secretion in the locust rectum in vivo is modulated by circulating hormonal factors rather than haemolymph pH or pCO₂ per se. / Science, Faculty of / Zoology, Department of / Graduate

This dissertation explores Jerome’s use of space in the Vita Hilarionis, through the use of the theory of critical spatiality. Three different spaces, all interrelated, are explored: desert space, monastic space and city space. The vita falls within the genre of Hagiography, a short biography that attempts to capture the life of a saint or holy man or woman. The Vita Hilarionis centres around the saint Hilarion, and follows his journey into the desert of Palestine in his goal to become an ascetic. One of Jerome’s goals with the writing of the vita is to show that Hilarion was the originator of monasticism in Palestine. Upon closer inspection of the spaces that Jerome describes to us, his greater ideological goal can also be exposed. Jerome, a Christian with a classical Roman education, makes use of older classical models in order to write his social geography of the late ancient Mediterranean world, such as traditional notions of centre and periphery. However, as theologian, he also reconstructs or re-imagines Roman spaces, such as the circus, to propagate Christianity, the new religion for the old world. Critical space has not yet fully been applied to text in late antiquity (100 – 600 CE) or early Christianity. This approach is steered by insights from social scientific criticism that not only views a text such as the vita as a literary piece of fiction, but also as a social product of its time. Through this view, largely spiritual themes in the vita can be viewed as also ideologically motivated, the social position and role of the ascetic in late Roman/ early Christian society understood, the spaces he/she moves in analysed and applied to shed light on early Christian identities. / Dissertation (MA)--University of Pretoria 2015. / Ancient Languages / Unrestricted

No description available.

<p>In arid regions, springs are important in many aspects of society due to the scarcity of surface water features. In the Great Basin of the United States, desert springs support the majority of regional biodiversity and are critical for supporting rare, threatened, and endangered organisms. Despite their importance, there are numerous threats to desert springs, with the most ubiquitous being climate change. In contrast to many studies examining potential metrics to describe the vulnerability of streams, wetlands and other surface water features to the effects of climate change, springs are often overlooked. Part of the knowledge gap stems from the complexity of springflow generation and the rarely field-tested connection between groundwater response time and groundwater residence time.</p> <p> This dissertation tests, in a systematic way, different metrics that may help define criteria to evaluate whether a spring is likely to persist or desiccate with increasing regional hydrologic stress due to climate change. Field data was collected over a 4-year period from >80 springs across the topographically and geologically heterogeneous terrain of the southern Great Basin. </p> <p>Throughout this dissertation, I use a variety of different tools (e.g., remote sensing, environmental tracers, geospatial analysis) to “attack” this complicated problem from different angles. I begin by examining factors indicative of hydrogeologic resistance to major drought. After finding a connection between groundwater residence time and hydrogeologic resistance, I examine other factors (e.g., geochemical, topographic, ecological, variability) that are related to groundwater residence time and also identify where these relationships fail. </p>