Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-07T14:00:25Z No. of bitstreams: 1 marianajunqueiramelgacooliveira.pdf: 598733 bytes, checksum: 3becd25207b04ce9206aa81dc277118f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-07T16:36:04Z (GMT) No. of bitstreams: 1 marianajunqueiramelgacooliveira.pdf: 598733 bytes, checksum: 3becd25207b04ce9206aa81dc277118f (MD5) / Made available in DSpace on 2017-04-07T16:36:04Z (GMT). No. of bitstreams: 1 marianajunqueiramelgacooliveira.pdf: 598733 bytes, checksum: 3becd25207b04ce9206aa81dc277118f (MD5) Previous issue date: 2007-06-14 / O aumento da ocorrência e dominância de Cylindrospermopsis raciborskii em ecossistemas aquáticos continentais, observado em todo o mundo tem resultado, em muitos casos, na substituição de outras espécies de cianobactérias, como Microcystis aeruginosa. Os fatores relacionados a essa dominância ainda não são bem compreendidos. O objetivo deste trabalho foi avaliar a influência da luz e nutrientes na competição entre C. raciborskii e M. aeruginosa. Foram realizados experimentos em cultivos unialgais visando determinar a dinâmica de absorção de nitrogênio (N) e fósforo (P) por 4 cepas (2 cepas de C. raciborskii, 2 de M. aeruginosa). As habilidades competitivas das duas espécies foram avaliadas em cultivos mistos em 3 condições de intensidade luminosa (alta, média e baixa) e de limitação de N e P. As quatro cepas estudadas apresentaram a mesma dinâmica na assimilação de nutrientes,absorvendo rapidamente N e P (ca. 24hs) e com taxas de crescimento, tempo de duplicação e rendimento máximo da cultura semelhantes. Nos experimentos de competição as cepas de M. aeruginosa foram dominantes na maior intensidade luminosa nas condições P-limitada e controle e na limitação por N apenas no ultimo bloco. Na menor intensidade foi dominante apenas nos dois últimos blocos na condição controle. Na intensidade média foi dominante na condição controle no ultimo bloco, com limitação de fósforo e nitrogênio nos dois últimos blocos. Enquanto que apenas uma cepa C. raciborskii foi dominante na condição controle na menor intensidade luminosa. Na condição N-limitada, C. raciborskii foi dominante apenas na menor intensidade no primeiro bloco e na maior intensidade no segundo bloco de experimentos. Na condição P-limitada, C. raciborskii não foi dominante em nenhum momento. Fica evidente portanto, a influência e interação da disponibilidade de luz e nutrientes na competição entre C. raciborskii e M. aeruginosa, contudo, as respostas são dependentes das cepas, e as generalizações específicas devem ser avaliadas com cuidado. / The increase in occurrence and dominance of the cyanobacteria Cylindrospermopsis raciborskii in freshwater ecosystems, observed worldwide, has resulted, in many cases, in a replacement of other species like Microcystis aeruginosa. The factors related with this dominance are still unknown. The aim of this work was to evaluate the influence of light and nutrients in the competition between C. raciborskii and M. aeruginosa. Experiments with 4 strains (2 strains of C. raciborskii, 2 strains of M. aeruginosa) in unialgal cultures have been accomplished to determine the nitrogen (N) and phosphorus (P) uptake dynamics. Competitive abilities of the two species have been evaluated in mixed cultures under 3 light intensities (high, medium and low) and under N and P limitation. The 4 studied strains presented the same nutrient uptake dynamics, absorbing N and P quickly (ca. 24 hours) and similar growth rates, mean doubling time and maximum yield of the cultures. At competition experiments M. aeruginosa was dominant in P-limited and control conditions under high and medium light intensities. C. raciborskii strains presented different responses: one of them was dominant in all conditions under low light intensity and also N-limited condition under medium light intensity. The other was dominant only in the N-limited and control conditions under low light intensity. It’s then evident the influence of the availability of light and nutrients in the competition between C. raciborskii and M. aeruginosa, however, the responses rely on the strains and specific generalization should be carefully evaluated.

Cyanobacteria are notorious for their potential to produce toxins with human health effects, particularly the hepatotoxic microcystins (MCs), but cyanobacteria also produce other bioactive compounds. A wide variety of oligopeptides including aeruginosins, cyanopeptolins and cyanobactins may be as toxic as MCs. To investigate the production of these compounds, an UPLC QTOF-MS/MS method was developed to compare the metabolomic profiles of various strains of a common bloom-forming and toxigenic species, Microcystis aeruginosa, as well as those obtained from lakes with mixed cyanobacterial assemblages. Although many compounds could not be confirmed, MCs were rarely the dominant secondary metabolite in any sample. Since the biological role of MCs remains unknown, I tested the hypothesis that MCs provide protection against oxidative stress as induced through exposure to the herbicide atrazine and UV radiation in pure cultures of toxic vs non-toxic strains. Results were inconclusive and varied between strains suggesting other mechanisms exist to counter oxidative stress.

La pollution lumineuse, résultat de l'éclairage nocturne anthropique, est un problème répandu dans le monde. Elle affecte une grande variété d'êtres vivants dans les milieux où elle est présente. Les effets exacts qu'elle peut avoir sur les organismes n'ont pas été beaucoup explorés . À ce sujet, rien n'est connu de son influence sur le phytoplancton. En l'occurrence, les cyanobactéries sont des organismes unicellulaires du phytoplancton. Dans cette étude, une cyanobactérie, Microcystis aeruginosa , a été cultivée en turbidostat en absence et en présence d'éclairage nocturne tel qu'observé à la surface d'un lac urbain éclairé. Plusieurs mesures ont été réalisées des intervalles de deux heures sur trois périodes de 48h afin d'observer les changements sur l'écophysiologie des cyanobactéries en présence de pollution lumineuse. Certaines de ces mesures montrent un effet de la pollution lumineuse,. comme le rendement quantique de photosynthèse, la quantité de chlorophylle a et de protéines photosynthétiques par cellule, démontrant ainsi l'effet de la pollution lumineuse sur M. aeruginosa . D'autres mesures n'ont pas été affectées par la pollution lumineuse. Celles-ci comprennent la quantité de certaines protéines photosynthétiques, la mesure d'efficacité photosynthétique par 14 [degrés Celsius] et la microcystine intracellulaire. Une hypothèse permettant d'expliquer les résultats a été émise. En conclusion, l'étude a permis de montrer qu'un éclairage d'une intensité lumineuse semblable à ce qui est retrouvé dans nos villes peut causer des changements dans l'écophysiologie de Microcystis aeruginosa en laboratoire.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21813号 / 農博第2326号 / 新制||農||1066(附属図書館) / 学位論文||H31||N5185(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 左子 芳彦, 教授 澤山 茂樹, 准教授 吉田 天士 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Algal blooms caused by toxigenic cyanobacterial species are an increasing economic burden globally, as high anthropogenic inputs of nitrogen and phosphorous, coupled with rising levels of atmospheric CO2, promote eutrophication and enhance bloom proliferation. Of the freshwater bloom forming species, Microcystis aeruginosa has garnered the most attention due to the production of toxic secondary metabolites known as microcystins. These cyclic peptides are potent eukaryotic protein phosphatase 1 and 2A inhibitors, and can induce hepatic damage if concentration levels reach above the World Health Organization level of 1 µg/L. Current mitigation strategies of water column disruption or by use of broad acting chemicals, are limited in their range and may cause unwanted off target effects to the surrounding biota. Antisense oligonucleotides are short single-stranded DNA polymers that hybridize with transcribed mRNA, and suppress translation of protein products through steric hindrance of ribosomes, or by RNAse H degradation of the DNA/RNA bound complex. While antisense oligonucleotide applications have proven successful in the pharmaceutical industry, their potential remains largely unexplored in environmental contexts. For this reason, we investigated the knockdown of microcystin synthetase gene cluster mcyE in M. aeruginosa. We found that ionic charge neutralization coupled with heat shock were effective chemical competence based methods for delivery, mcyE transcript abundance in cells treated with phosphodiester linked antisense oligonucleotides significantly decreased in RT-qPCR analysis, and production of intracellular microcystin significantly decreased over a 24 hour period (-1.9 fg/cell). This work demonstrates a novel proof of concept for the potential use of exogenous antisense oligonucleotides to target M. aeruginosa in harmful algal bloom occurrences.

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Microcystis aeruginosa is known widely for the obnoxious nature of its bloom. Problems resulting from blooms of the alga include: death of fish and other aquatic life, clogging of filter systems in water treatment plants, taste and odor problems, and death of cattle and water fowl via extracellular polypeptides. Blooms of this nuisance alga have historically occurred in waters receiving pollution from sewage effluents or runoff from agricultural lands. Studies have shown that 2,4-0ichlorophenoxyacetic acid (2,4-0) and 2,4,5-Trichlorophenoxyacetic acid (2,4,S-T) mimic the metabolic activities of the plant hormone indoleacetic Acid (IAA). IAA has been shown to stimulate the growth of some green and blue-green algae. Recent evidence suggests that blooms of Microcystis aeruginosa were triggered when the herbicides 2,4-D and 2,4,5-T were introduced to lakes and rivers. The results of this study showed that batch cultures of non-axenic Microcystis aeruginosa containing 2,4-D and 2,4,5-T exhibited significantly more growth than controls over a wide range of herbicide concentrations. Growth in 2,4-D treated cells was statistically significant from the control at a = 0.05 at concentrations as low as 10 -7 M (0.020 mg/l) and 10 -5M (2.5 mg/l) for 2,4,5-T. Also, a plot of maximum cell yield values versus herbicide concentrations resulted in a linear relationship. / Master of Science

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