Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Resultados da Pesquisa
Item The inorganic carbon source and concentration affect growth and central metabolism in a microcystin producer cyanobacteria(Universidade Federal de Viçosa, 2019-07-31) Castro, Naira Valle de; Araújo, Wagner Luiz; http://lattes.cnpq.br/4819826519596425Cyanobacteria, microorganisms belonging to the Bacteria domain, are widely distributed geographically, yet most genera are found in freshwater environments. Some cyanobacterial strains are able to produce toxins (cyanotoxins), like microcystins (MCs), that show hepatotoxic effect in animals. The genetic basis, chemical structure, and biosynthetic route as well as microcystin action in eukaryotic organisms have been deeply studied. However, it remains unknown which are the roles played by such compounds in the producing organism. Here, we tested the hypothesis that growth medium supplied with different concentrations of inorganic carbon (Ci) source promotes metabolic and physiological adjustments coupled with changes in MC production. To this end, the cyanobacterial strain Scytonemataceae CCM-UFV057 was cultured in different growth medium, (i) standard BG-11 0 (supplied with 0.02 g·L - of sodium carbonate), as control; (ii) BG-11 0 without Ci (T1); and (iii) BG-11 0 supplied with two concentrations of sodium bicarbonate, 0.016 g·L -1 (T2) and 1.6 g·L -1 (T3). Growth evaluation together with physiological and biochemical analysis as well as MC’s quantification were carried out. Growth parameters of CCM-UFV057 were similar for all growth conditions. Both T1 and T2 lead to similar metabolic patterns, despite different responses in both photosynthetic and respiratory rates. The strain CCM-UFV057 was able to produce five MCs congeners, with the variants showing m/z of 540 and 1037 as the most abundant forms in all conditions. MCs production was highly influenced by Ci concentration, and T1 and T3 lead to the higher and lower MC concentration, respectively, indicating that low Ci concentrations somehow improve the MC production. Notably, the carbon source (carbonate versus bicarbonate) did not seems to affect MC production. Taken together, our data suggest that high amounts of MC under low Ci conditions can contribute to the maintenance of photosynthetic rates, keeping both higher carbon assimilation rates and cellular homeostasis without growth impairments.Item An integrated multi-layered analysis on Desmonostoc(Universidade Federal de Viçosa, 2019-07-31) Almeida, Allan Victor Martins; Araújo, Wagner Luiz; http://lattes.cnpq.br/5605331353460376Cyanobacteria (phylum Cyanobacteria) are gram-negative bacteria, capable of performing oxygenic photosynthesis. These microorganisms form a phylogenetically coherent group despite presenting a great morphological diversity. Although the taxonomic classification of cyanobacteria was for a long time based primarily on morphological characters the application of other techniques, especially in the last decades, contributed to a better resolution of the cyanobacteria systematics, leading to a revision of the phylum. Accordingly, polyphasic approaches applied to the study of strains described as belonging to the genus Nostoc have indicated a polyphyletic origin of this genus, when considered its description based solely on morphological criteria. Thus, the taxonomy and systematics of strains closely related to the genus Nostoc have been reviewed leading to the description of new genera. Although the genus Desmonostoc occurs as one new genera, relatively few studies have been carried out to elucidate the phylogenetic and morphological relationships among its species, as well as between members of this genus and those closely related. In fact, only one study performed the characterization of a Desmonostoc strain, culminating with the description of the species D. salinum whereas another described the possible biotechnological application of members of this genus. In this context, the present study investigated the diversity within the genus Desmonostoc, based on morphological, molecular, metabolic and physiological characters. Although the last character is a non-usual tool used in the polyphasic approach it was efficient in the characterization of the genus Desmonostoc performed here. Our phylogenetic analysis for the 16S rRNA gene put all strains used here in the D1 cluster of Desmonostoc and demonstrate the possible emergence of two novel sub-clusters. It was also possible to observe that the nitrogenase genes, nifD and nifH, exhibits different evolutionary histories within the Desmonostoc strains. Collectively metabolic and physiological data, coupled with the morphometric ones are, in general, in good agreement with the separation based on the 16S phylogeny. Furthermore, it provide important information on the diversity of Desmonostoc lineages collected from different brazilian biomes by revealing that they are cosmopolitan strains, acclimatized to low luminous intensities, with great metabolic diversity within the same genus and with biotechnological potential.Item Desmonostoc salinum CCM-UFV059, a novel cyanobacteria from a saline- alkaline lake: molecular and physiological responses to light, desiccation and salt stress(Universidade Federal de Viçosa, 2019-02-22) Alvarenga, Luna Viggiano de; Araújo, Wagner Luiz; http://lattes.cnpq.br/5025552116262277Cyanobacteria are widespread photosynthetic prokaryotes and are among the oldest organisms on Earth. During their long evolution, cyanobacteria developed an enormous diversity in terms of morphology, metabolic plasticity and molecular properties, which seems to be important factors to cope with limiting environmental conditions and allowed their ecological success in almost all known photic ecosystems. The first part of this work consisted of the taxonomic characterization, using the polyphasic approach, of the strain Desmonostoc salinum CCM-UFV059, a filamentous heterocytous cyanobacterium isolated from a hypersaline lake. Taken together, our data allowed the description of a new species and the first strain of the Desmonostoc genus from a saline environment. The second part of this work aimed to decipher the main salt acclimation mechanisms present in Desmonostoc salinum CCM-UFV059, because most studies on cyanobacterial salt acclimation have been carried out on unicellular strains, which cannot fix N 2 . We performed a comparative study using the model strain Nostoc PCC7120, and we could observe a remarkable high salt tolerance displayed by Desmonostoc salinum CCM-UFV059. In cells of Desmonostoc salinum CCM-UFV059 the intracellular sodium content was significantly lower than in Nostoc PCC7120 and these cells were able to sustain photosynthetic activity up to 0.5 M NaCl while Nostoc PCC7120 cells were not. Moreover, Desmonostoc salinum CCM- UFV059 induced sucrose over-accumulation under desiccation stress conditions, which allowed this strain to survive harsh desiccation stress. Together with the presence of highly unsaturated lipids in the membrane, the high sucrose production and the intense export of sodium could explain, at least partially, how Desmonostoc salinum CCM-UFV059 is capable of acclimate to high salinities and to resist longer desiccation periods. Collectively, our results provide the first insights into the physiological adaptations explaining the remarkable high salt and desiccation tolerance presented by this strain. Furthermore, given that cyanobacteria have several biotechnological applications, such as the production of biomass for human and animal consumption, and metabolites of industrial interest, the third part of this work was performed to analyze the physiological and metabolic responses of Desmonostoc salinum CCM-UFV059 submitted to different light availabilities, aiming at finding the light regime suitable for maximal biomass production as well as to better understand how distinct growth conditions may interfere within the basal metabolism. Collectively our results indicate that Desmonostoc salinum CCM-UFV059 display a highly plastic metabolism and the ability to grow in a large range of light regimes, that open the possibility to outdoor cultivation and commercial use of this species that has a great biotechnological potential. Notwithstanding, further research is clearly required in order to enable a large scale cultivation of Desmonostoc salinum CCM-UFV059.