In recent years, the rhizobial taxonomy changed significantly with the discovery of novel symbiotic associations between legumes and nodulating bacteria. This was aided by the focus shift from studying only agricultural crops to legumes indigenous to certain regions, ultimately to discover new inoculant strains and to uncover the secrets of the rhizobium¬legume symbiosis. In previous studies on the diversity of South African rhizobia, it has become clear that our country has a wealth of rhizobia. Cyclopia is a legume genus, which belongs to the fynbos biome of South Africa. Honeybush tea is a herbal infusion manufactured from the leaves and stems of certain Cyclopia spp. Commercial cultivation of this potentially new agricultural crop is now developed to protect the natural Cyclopia spp. populations from harvesting and ultimately extinction. Superior inoculant strains are necessary for these commercial seedlings. The diversity of root-nodulating strains isolated from 14 Cyclopia spp. was determined using 16S-23S IGS-RFLP and partial 16S rDNA base sequencing. Based on 16S-23S IGS-RFLP and partial 16S rDNA base sequencing most of the isolates, with the exception of seven strains, were found to belong to the genus Burkholderia. More extensive phylogenetic, symbiotic and phenotypic studies of selected strains were performed using near full-length 168 rDNA base sequencing, nodA base sequencing and substrate utilisation analysis. In the genus Burkholderia, the isolates belonged to the novel root-nodulating species Burkholderia tuberum and several novel, undescribed Burkholderia genotypes. However, no new Burkholderia species could formally be proposed, since DNA-DNA hybridisation analysis, which is a prerequisite for the description of new species could not be performed in our laboratory. The seven strains not affiliated with the Burkholderia genus belonged to two Bradyrhizobium genospecies, R tropici and a possibly new genus in the a-Proteobacteria. The nodA sequences of all the Cyclopia isolates corresponded to a large extent, indicating that different chromosomal genotypes harbour the same symbiotic genotype. All the isolates of the Cyclopia genus appear to be acid-tolerant, which is in agreement with the acidic nature of the soil from which the strains were isolated. / Thesis (PhD(Microbiology))--University of Pretoria, 2004. / Microbiology and Plant Pathology / unrestricted

Many organisms form mutually beneficial, symbiotic partnerships with other organisms. Corals and sea anemones undergo mutualistic symbioses with photosynthetic algae of the family Symbiodiniaceae, and these partnerships are key for the viability of coral reef ecosystems. Cnidarian-Symbiodiniaceae symbioses are sensitive to climate change-induced ocean warming, which causes the disruption of symbiosis, commonly referred to as bleaching, and can lead to coral mortality. Cellular and molecular aspects of how this symbiosis is established and disrupted by heat stress are not well understood. The research presented herein characterizes immunity transcription factor NF-kappaB in the cnidarian model organism Exaiptasia pallida (Aiptasia). It is shown that the DNA-binding site specificity of Aiptasia NF-kappaB is similar to mammalian NF-kappaB subunit p50 and that this binding specificity is conserved across a broad expanse of metazoans. Moreover, Aiptasia and human IkappaB kinases can phosphorylate serine residues in the C-terminus of NF-kappaB, signaling the protein for proteasomal processing to allow for nuclear localization, DNA binding, and transactivation. In Aiptasia, NF-kappaB expression is downregulated by symbiosis onset in larvae, and NF-kappaB total expression, DNA-binding activity, and tissue-specific expression are increased following laboratory-induced loss of symbiosis in adult Aiptasia. NF-kappaB downregulation during the onset of symbiosis occurs only with the compatible symbiont Breviolum minutum and data suggest that host TGFbeta plays a role in NF-kappaB downregulation. Results demonstrate that aposymbiotic Aiptasia (with high NF-kappaB levels) have increased survival following bacterial infection as compared to symbiotic anemones. A bioinformatic analysis shows that potential NF-kappaB binding sites are enriched in promoter regions of immune-related genes that are upregulated in aposymbiotic Aiptasia. Increased levels of NF-kappaB are also found in a genet of the coral Pocillopora damicornis that exhibits resilience to heat-induced bleaching. Overall, the results in this thesis suggest a role for NF-kappaB-directed immunity in symbiosis onset, bleaching, and resistance to biological stressors in cnidarians. It is proposed that NF-kappaB downregulation in Aiptasia is a mechanism to lower host immunity and promote the establishment of symbiosis, but that this process compromises host immunity to pathogen infection. Nevertheless, constitutively high basal levels of NF-kappaB may be protective against bleaching in cnidarians.

Creating immersive performance design using mycorrhizalstructure methodology and iceberg theory in circusperformance settingsWhat is immersive performance design and what role does ithave in a performance-based setting and frame? Does it holdthe possibility and capability of challenging the frame in whichwe normally perform?The focus of my research is to explore the boundaries of howwe approach devising performance with particular attentionto the relationships in space and the proximity of objects andparticipants within this. I am to create a performance-basedmilieu in which spectators, practitioners, the space andobjects are in symbiosis. A space of symbiosis where no oneperson has a different status from the other, but a space thatallows for people holding different roles. The performer andthe audience, the object and the body. My definition ofsymbiosis draws inspiration from the mycorrhizae funginetwork as a starting point for me to mould a methodologyadapted to a performative setting. To this milieu I incorporateother factors and concepts, such as the role of text, thedialogue of the still and quiet and how our senses-experienceaffect our perception. I attempt to weave these concerns intomy circus practices

Mycorrhizal associations are very important to plant growth. This is mainly due to the hyphal stands that are able to utilize concentrations of nutrients that would normally be considered unavailable for plant growth, especially phosphorus. These associations are of great importance in soils that have been disturbed by mineral extraction and are consequently low in available nutrients. The ability of mycorrhizal fungi to form associations on disturbed sites may be dictated by a number of factors: moisture, soil pH, soil fertility (including heavy metal ions), salinity, and plant response. Two factorial experiments were conducted with the legume Hedysarum boreale cv utahensis and the mycorrhizal fungus Glomus mosseae. The first to observe the effects of three factors: fungi level (mycorrhizal or non-mycorrhizal), type of phosphate (P) (monocalcium or superphosphate), and irrigation intervals (2, 4, or 8 day) on root and shoot dry weights. The second experiment was conducted to observe the effects of three factors: fungi level, type of P and level of P on root and shoot dry weights, root and shoot P concentration, nodulation and nitrogen fixation. In the first experiment, the combination of fungi level and type of P had a significant effect on root /shoot ratio (weight ). In the second experiment, the interaction of fungi level, type of P and level of P had a significant effect on nodulation. The interaction of P type and P level had a significant effect on the amount of phosphorus found in plant roots and shoots. The factor, fungi level, had a significant effect on shoot dry weight, with mycorrhizal plant's shoots having a significantly greater dry weight than non-mycorrhizal shoots. Mycorrhizal infection may have been greatly reduced by the adverse soil conditions found in the mine spoil (i.e. low pH, high salinity , and high heavy metal concentration). What infection did occur may have been great enough to produce changes in the shoot dry weight, but not great enough to significantly enhance plant P uptake. The reintroduction of mycorrhizae into disturbed areas for reclamation purposes may be important for rapid establishment of plant cover and to speed up succession. Before mycorrhizae can be reestablished in a disturbed area, many potential stress factors need to be addressed and, if possible, overcome.

Anglerfishes are easily one of the most popular deep-sea creatures due to their menacing appearance, extreme sexual dimorphism, parasitic mating approach, and eye catching bioluminescent lure. Unlike most bioluminescent fishes, which intrinsically generate light, female anglerfishes belonging to nine of the 11 families within the suborder Ceratioidei (deep-sea anglerfishes) have developed a symbiotic relationship with bioluminescent bacteria that are housed within the light organs. Previous molecular work had identified symbionts from two anglerfish species as novel and possibly unculturable taxa (Haygood et al., 1992), but nothing more has been revealed about the bioluminecent symbionts of ceratioids. As part of the Gulf of Mexico Research Initiative-funded DEEPEND project (Deependconsortium.org), the objective of this study is to characterize the escal microbiome of deep-sea anglerfishes and identify potential-symbiont taxa. A total of 36 anglerfish specimens were collected on DEEPEND cruises DP01 through DP04. These specimens consist of adult and larval individuals belonging to six of the families with the suborder Ceratioidei: Ceratiidae (n=22), Oneirodidae (n=7), Linophrynidae (n=3), Melanocetidae (n=2), Centrophrynidae (n=1), Melanocetidae (n=2), Gigantactinidae (n=1). DNA was extracted from esca, skin, fin, gill, gut, and caruncle tissues, as well as seawater. High-throughput sequencing of the 16S rRNA hypervariable V4 region was carried out using the Illumina MiSeq. Sequencing revealed five potential bioluminescent-symbiont taxa (OTU IDs: 9129, 9131, 160210, 523223, and 939811), which had the greatest relative abundance (25.2% - 98.7%) within 12 of 21 adult specimens. These taxa belong to the family Vibrionaceae and were found at greater than 10% relative abundance in the escal samples of adult anglerfishes belonging to the Ceratiidae and Melanocetidae families, but they were not found in high abundance in larval individuals of the same families. Sequencing of larval samples revealed five potential bioluminescent-symbiont taxa (OTU IDs: 136178, 176420, 523223, 837366, 939811) which were of greatest relative abundance (8.1%-67.1%) within nine of 13 specimens. Also members of the family Vibrionaceae, these taxa were found in high abundance in larval anglerfishes belonging to the Oneirodidae, Linophrynidae, Gigantactinidae, and Ceratiidae families. This study is the first to to examine the bioluminescent symbionts from seven different ceratioid families.

No description available.

The overall aim of this study was to provide new and updated information about subterranean termite morphology and digestive physiology. Scanning electron microscopy was used to obtain high resolution images of morphological features of the termite cuticle not discernable by light microscopy. In addition, digital scanning electron micrographs clearly show the appearance of wood particles recovered from the termite digestive tract at different stages of digestion. The ability of termites to obtain and conserve nitrogen in their diet was demonstrated by establishing whether the insect can digest chitin, as well as from determination of levels of soluble proteins and uric acid in the feces. Finally, a technique for determining the efficiency of cellulosic food digestion was tested. Scanning electron microscope images of alate abdomens showed similar appearance of cuticular structures between two subterranean termite species. In addition, the high magnification of electron microscopy allowed for identification of a pair of cuticular structures in the vicinity of the female genitalia that had not been reported from previous light microscope studies. Scanning electron microscopy also revealed the appearance of wood undergoing degradation as it traverses worker termite digestive tract, showing detail not possible from light microscope images. Adult workers of a native termite species were found to produce the enzymes needed to digest chitin, a nitrogen containing polysaccharide ingested by termites. Specific activity of chitinase was subsequently determined to establish the efficiency of chitin digestion for the termite species tested. As termites are coprophagous, significant levels of proteins measured from the feces demonstrated an additional potential dietary nitrogen source. Uric acid was generally found to be absent from termite feces, however. Digestive efficiency of wood cellulose could not be determined for Formosan termites due to the inability to obtain sufficient feces for quantification of undigested food contained in it. Previous studies of Formosan termite digestive efficiency did not address difficulty in obtaining feces for assay. Therefore, interpretation of data from earlier studies of Formosan termite digestive efficiency should be viewed with caution.

Human activity since the Industrial Revolution has increased global greenhouse gas concentrations resulting in rapid climate change, which now threatens terrestrial and marine ecosystems. Tropical coral reefs, along with the biodiversity and communities they support, are particularly threatened by these changes in climate. Corals are a consortium of organisms, with the coral host along with its photosynthetic endosymbiont (Family Symbiodiniaceae) and diverse community of microorganisms (bacteria, archaea, fungi, and viruses) together forming the ‘coral holobiont’. However, the symbiosis between tropical corals and Symbiodiniaceae algae is sensitive to even small changes in temperature and ‘coral bleaching’ events – the loss of symbiosis – are now occurring with increased frequency and severity. These bleaching events can result in coral mortality and loss of entire reefs if stressful conditions do not subside. While research efforts have increased our ability to understand and predict coral bleaching events, fundamental questions remain surrounding how genetic diversity of the coral holobiont and interactions with its environment can drive coral resilience or resistance under climate change. The overarching goal of my dissertation is to understand how various abiotic (i.e., stress duration, spatiotemporal variation on the reef) and biotic (i.e., holobiont diversity, symbiosis) factors determine a coral’s response to environmental change at the level of phenotype and genotype. To achieve this goal, I first tested how environmental history and stress duration modulated the physiological responses of two reef-building corals under combined ocean warming and ocean acidification conditions. I found that one species was more stress-resistant (Siderastrea siderea), but that both duration of stress exposure and environmental history (inshore vs. offshore reef origin) modulated coral physiology. Next, I investigated the importance of holobiont genetic identity and abiotic environment in driving phenotypic responses of S. siderea exposed to a diel temperature variability (DTV) and subsequent heat challenge experiment. I found that while DTV increased coral growth, cryptic host diversity and their unique pairings with algal symbiont strains were the strongest predictors of holobiont physiology and response to heat challenge. Lastly, I leveraged genome-wide gene expression profiling and the facultative symbiosis between the subtropical coral Oculina arbuscula and its symbiont Breviolum psygmophilum to disentangle the independent responses of both partners to heat and cold challenges in and out of symbiosis. I found that O. arbuscula host gene expression was more plastic under temperature challenges relative to B. psygmophilum when in symbiosis, and that symbionts exhibited more gene expression plasticity in culture compared to in symbiosis. Taken together, this dissertation provides valuable insights into the phenotypic and genotypic mechanisms that contribute to coral success in a changing climate.

Arbuscular mycorrhizal (AM) fungi are ubiquitous symbionts of terrestrial plant species with associations predominantly characterized as mutualistic. In addition to well-documented enhancement of host growth response, more recent analyses have demonstrated the conferral of host benefits under numerous biotic and abiotic stressors. However, much of the established evidence originates from studies involving limited AM fungal diversity. Accordingly, this study sought to evaluate the potential effects of inoculation on plant host physiological traits within a growth chamber environment, investigate potential correlations between host trait responses, & assess the degree of phylogenetic signal observed in trait responses due to the presence of AM fungi. Overall, inoculation did not result in meaningfully different effects in host trait responses relative to controls. The effects of unique inoculum identity were also not meaningfully different from one another, although some instances of deviation from this trend were observed. Trait correlations were also largely absent after accounting for species relatedness. Further, model selection criteria tended to endorse an effect of unique inoculum identity but was not suggestive of effects due to evolutionary history. The presently described experimental implementation of AM phylogenetic diversity, comprising 36 taxa across 8 families, contributes to a greater contextual understanding of the AM symbiosis and offers an approach suitable for future studies.

No description available.