Data of Thesis
Author: Maria Elisângela Venâncio dos Santos.
Title: Effect of exudate in physiological autoregulation of Microcystis sp.
Year: 2009. Full text (in Portuguese)
Abstract:
Effect of exudates on the physiological self Microcystis sp. Quorum sensing is a process of cell communication that plays a central role in the physiology of microorganisms. Many bacteria use this system and coordinate their activities in a manner similar to multicellular organisms. This study aimed to investigate whether cyanobacteria use signaling molecules of quorum sensing to regulate their physiology, and the entry of the population in stationary phase of growth, as already observed in other bacteria. For this study, a strain of Microcystis sp. (Milj-48) was grown in media previously conditioned by itself (exudatos), obtained from different stages of growth. To evaluate the effect of higher concentrations of exudato, was also an experiment with the addition of exudatos focused on 100 and 50x for crops. The effects produced by exudatos was verified by assessment: cell growth, by counting the cells, the variation of the concentration of chlorophyll a and varying the concentrations of microcystins, using the method of enzyme immunoassay (ELISA) for detection of total microcystins and High Performance Liquid Chromatography (HPLC) for detection of intracellular microcystin. It demonstrated an inhibition of cell growth with all exudatos tested on the control. The most pronounced effect was obtained with exudato the 6th day of growth (phase exponencial). There was no effect by increasing the concentration of this exudato. The cultures showed no inhibition in the production of chlorophyll a. The addition of the exudato cultivation resulted in cell aggregation and chlorosis, phenomena typical of cultures in stationary phase or in limitation of nutrients. A positive correlation between production of toxin and inhibition of growth is apparent. It is suggested that the strain of Microcystis sp. (Milj-48) promotes the release of a yet unknown signal that interferes with their own cell division, we raise the possibility of involvement of this signaling microcystin.
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