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Under Gause's principle two species cannot indefinitely occupy the same niche. The north and south arms of Great Salt Lake are separated by a rail causeway, resulting in salinity differences and color variation between the arms. Farmington Bay is also separated from the south arm by a vehicular causeway to Antelope Island. These causeways allow examination of competitive exclusion of cyanobacteria in the hypersaline environment of the Great Salt Lake. Cyanobacterial distributions partially map salinity, with Aphanothece halophytica proliferating in the north arm, and Nodularia spumigena in the south arm. I hypothesized that cyanobacterial species abundant north of the railway causeway are competitively excluded from the south by other species, and that cyanobacterial species that thrive and bloom south of the Antelope Island causeway cannot grow in the high salinity of the north. To test these hypotheses, 129 flasks of autoclaved water from the north and south sides of each causeway were inoculated with Great Salt Lake water samples from the north and south sides of the causeways. Four genera of cyanobacteria, Aphanothece, Oscillatoria, Phormidium, and Nodularia were identified and counted from the culture flasks using comparative differential interference contrast, fluorescence, and scanning electron microscopy. Counts of the cyanobacteria found in each flask were totaled and two way Analysis of Variance tests as well as exact tests were performed. Rankings of median abundances were also calculated. These data support the first hypothesis because Aphanothece halophytica was found in all inocula, but appears to be suppressed by the presence of Nodularia spumigena, which periodically blooms. The second hypothesis is also supported by the data because N. spumigena was found only in inocula from the less saline waters south of Antelope Island causeway, and apparently cannot survive the high saline waters north of the railway causeway.

Algal blooms are a common occurrence in water bodies of all shapes and sizes throughout the United States and countries around the world. The State of Florida is no exception to this phenomenon. Cyanobacteria, or blue-green algae, have proven to be of special concern due to its proliferation and potential to produce toxins that are harmful to humans, livestock and wildlife. A casual drive along the roads and in the neighborhoods of central Florida will confirm algal conditions in many areas. The potential for exposure to harmful and possibly fatal toxins associated with these algal blooms are becoming more evident as urban development progresses. Detailed studies have been previously performed for large lakes and rivers in the State of Florida, but no studies have been performed regarding stormwater ponds. Since stormwater ponds in residential neighborhoods are a common source for irrigation, research in this area is warranted due to the potential health effects associated with Cyanobacteria. This research was conducted to determine if Cyanobacteria does exist in stormwater ponds and to what extent. Cyanobacteria were found to be in stormwater ponds of various sizes, locations and watersheds in the central Florida area. Even though the algae and its associated toxins were encountered in the stormwater ponds evaluated for this study, the levels detected were much lower than the values discovered in previous studies performed in the larger lakes and rivers around the State.

<p>  </p> <p>Cyanobacteria are among the simplest organisms to display circadian rhythms that synchronize endogenous physiological activities with a ~12-hour-light:12-hour-dark (12L:12D) cycle of the external environment. Detected by the input pathway composed of CikA and LdpA proteins, light is transduced to the central circadian oscillator encoded by the gene cluster <em>kaiABC. </em>While KaiC phosphorylation is primarily regulated by KaiA and KaiB proteins, two key components of the output pathway, RpaA and SasA proteins, mediate between KaiC phosphorylation, genome-wide expression, and control of cell division. In this study, <em>Synechococcus elongatus </em>UTEX 2973 showed similar growth patterns when subjected to white light only and white light supplemented with ultraviolet A (UV-A) radiation under 12L:12D intervals, although UV-A radiation hindered growth during light periods. Under continuous illumination, growth rates of <em>S. elongatus </em>UTEX 2973 were reduced by UV-A radiation but reflected intrinsic circadian rhythmicity. To elucidate the critical role of the circadian clock, a mutant void of <em>kaiABC</em> was generated via the CRISPR/Cpf1 system. A dysfunctional clock severely disrupted inherent growth rhythmicity, which was exacerbated by UV-A radiation. To investigate the effects of UV-A radiation on transcription patterns in <em>S. elongatus </em>UTEX 2973, expression levels of circadian genes, specifically <em>kaiABC</em>, <em>cikA</em>, <em>lpdA</em>, <em>rpaA</em>, and <em>sasA</em>, were assessed by qPCR analysis. For the UV-A-treated wild-type strain, <em>kaiA</em> and <em>kaiB</em> expression was generally downregulated, <em>kaiC</em> expression was upregulated during the second dark period, and <em>rpaA</em> expression was either upregulated or downregulated depending on the period. For the UV-A-treated Δ<em>kaiABC </em>strain, <em>lpaA</em> expression was upregulated in darkness, whereas <em>rpaA</em> and <em>sasA</em> expression was downregulated during light periods. When Δ<em>kaiABC </em>and wild-type strains were examined in the presence and absence of UV-A radiation, expression of <em>lpaA</em>, <em>rpaA</em>, and <em>sasA</em> was universally downregulated, yet <em>cikA</em> expression was upregulated in the dark. This study was the first to evaluate the impact of UV-A radiation on cyanobacterial circadian rhythms, in which UV-A radiation negatively affected cyanobacterial growth and strongly altered gene expression patterns over time. Without the circadian clock, rhythmicity of growth and transcription was demolished, such that the consequences were aggravated for the output pathway that relayed signals downstream from the central oscillator. </p>

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Most species of filamentous cyanobacteria are capable of gliding motility, likely via a conserved type IV pilus-like system that may also secrete a motility-associated polysaccharide. In a subset of these organisms, motility is only achieved after the transient differentiation of hormogonia, specialized filaments that enter a non-growth state dedicated to motility. Despite the fundamental importance of hormogonia to the life cycle of many filamentous cyanobacteria, the molecular regulation of hormogonium development is largely undefined. To systematically identify genes essential for hormogonium development and motility in the model heterocyst-forming, filamentous cyanobacterium Nostoc punctiforme, a forward genetic screen was employed. The gene identified using this screen, designated ogtA, encodes a putative O-linked β-N-acetylglucosamine transferase (OGT). Deletion of ogtA abolished motility while ectopic expression of ogtA induced hormogonium development even under hormogonium repressing conditions. Transcription of ogtA is rapidly up-regulated (1 h) following hormogonium induction and an OgtA-GFPuv fusion protein localized to the cytoplasm. In developing hormogonia, accumulation of pilA transcript in the wild-type and ΔogtA strain, while a reporter construct consisting of the intergenic region 5' to pilA fused to gfp produced lower levels of fluorescence in the ΔogtA strain than the wild type. Production of hormogonium polysaccharide in the ΔogtA strain was reduced compared to the wild type, but comparable to that of a pilA-deletion strain. Collectively, these results imply that O-GlcNAc protein modification regulates the accumulation of PilA via a post-transcriptional mechanism in developing hormogonia.

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No description available.