Sandra Barnard

Biological crusts of serpentine and non-serpentine soils from the Barberton Greenstone Belt of South Africa

Climate and geography can influence biological soil crust (BSC) community composition, but local heterogeneity in variables such as soil characteristics or microclimate gradients can also impact cryptogamic diversity. Heavy metals and nutrient imbalances in serpentine soils are known to influence the distributions of higher plants, but cryptogamic species appear to be more tolerant of substrate. The aim of this study was to compare the cryptogamic composition of serpentine and non-serpentine soils by using integrative taxonomy, which combines morphological and DNA barcoding data, to determine how soil characteristics in combination with rainfall can influence BSC community composition. Samples from serpentine and non-serpentine soils were enumerated and total genomic DNA was isolated from the soil samples. Analyses of the 16S rRNA gene and ITS sequences were done using the quantitative insights into microbial ecology (QIIME) workflow to determine which eukaryotic microorganisms were present in the samples. Sixty genera from the Cyanophyceae (38), Chlorophyceae (10), Bacillariophyceae (6), Eustigmatophyceae (4), Trebouxiophyceae (1) and Xanthophyceae (1) classes were detected with this approach. Results confirm that algae and cyanobacteria are tolerant of most substrates and can even colonize environments with high levels of heavy metal and nutrient imbalances, if moisture is present. Genera such as Acaryochloris, Annamia, Brasilonema, Chrocosphaera, Halomicronema, Planktothricoides, Rubidibacter, and Toxopsis are reported for the first time for South African soil.

Assessing the Likelihood of Gene Flow From Sugarcane (Saccharum Hybrids) to Wild Relatives in South Africa

Pre-commercialization studies on environmental biosafety of genetically modified (GM) crops are necessary to evaluate the potential for sexual hybridization with related plant species that occur in the release area. The aim of the study was a preliminary assessment of factors that may contribute to gene flow from sugarcane (Saccharum hybrids) to indigenous relatives in the sugarcane production regions of Mpumalanga and KwaZulu-Natal provinces, South Africa. In the first instance, an assessment of Saccharum wild relatives was conducted based on existing phylogenies and literature surveys. The prevalence, spatial overlap, proximity, distribution potential, and flowering times of wild relatives in sugarcane production regions based on the above, and on herbaria records and field surveys were conducted for Imperata, Sorghum, Cleistachne, and Miscanthidium species. Eleven species were selected for spatial analyses based on their presence within the sugarcane cultivation region: four species in the Saccharinae and seven in the Sorghinae. Secondly, fragments of the nuclear internal transcribed spacer (ITS) regions of the 5.8s ribosomal gene and two chloroplast genes, ribulose-bisphosphate carboxylase (rbcL), and maturase K (matK) were sequenced or assembled from short read data to confirm relatedness between Saccharum hybrids and its wild relatives. Phylogenetic analyses of the ITS cassette showed that the closest wild relative species to commercial sugarcane were Miscanthidium capense, Miscanthidium junceum, and Narenga porphyrocoma. Sorghum was found to be more distantly related to Saccharum than previously described. Based on the phylogeny described in our study, the only species to highlight in terms of evolutionary divergence times from Saccharum are those within the genus Miscanthidium, most especially M. capense, and M. junceum which are only 3 million years divergent from Saccharum. Field assessment of pollen viability of 13 commercial sugarcane cultivars using two stains, iodine potassium iodide (IKI) and triphenyl tetrazolium chloride, showed decreasing pollen viability (from 85 to 0%) from the north to the south eastern regions of the study area. Future work will include other aspects influencing gene flow such as cytological compatibility and introgression between sugarcane and Miscanthidium species.

The impact of zeta potential changes on Ceratium hirundinella cell removal and the ability of cells to restore its natural surface charge during drinking water purification

Unit processes of a conventional water purification facility are designed to remove suspended material from source water (both inorganic and organic impurities). Organic substances in source water include phytoplankton species (algae and cyanobacteria) that are generally negatively charged on the surface of the cells. The zeta potential (ZP) of algal cells needs to be destabilized in order to enhance removal thereof during water purification. The aims of this study were to investigate the ZP changes of Ceratium hirundinella (C. hirundinella) cells and the ability of cells to restore their natural ZP during the water purification process. C. hirundinella cells (>500 cells per mL) were collected from the Middle Lake in South Africa (coordinates: 26°10′50.40′′S; 28°17′50.11E). A six paddle jar test apparatus was used to simulate unit processes under laboratory conditions using 3 different coagulant options. The ZP analyser with a built-in calibrated pH meter was used to analyse the ZP and pH of the cells and the filtered source water. The coagulant concentration of 10 mg L−1 Ca(OH)2 and 10 mg L−1 organic polymer achieved the best coagulation conditions as assessed against an operation ZP window of between −10 mV to +3 mV. This Ca(OH)2 and organic polymer dosing concentration was used to purify water with increasing cell concentrations (2000 cells per mL to 7000 cells per mL, increments of 1000) applying settling times of 20 minutes, 120 minutes and 240 minutes. Results obtained indicated high percentages of cell removal after 20 minutes (82–88%), 120 minutes (93%) and 240 minutes (95%) respectively. However, after extended settling times (120–240 minutes), more metabolically active cells were observed in the supernatant of samples containing higher cell concentrations. The findings showed that the ZP of C. hirundinella cells changes as a result of adding coagulants to form flocs, but may be restored when water purification facilities employ poor optimization practices and allow extended settling periods or retention times.