Mutation of algae from sensitivity to resistance against environmental selective agents: the ecological genetics of Dictyosphaerium chlorelloides (Chlorophyceae) under lethal doses of 3-(3,4-dichlorophenyl)-1, 1-dimethylurea herbicide

Bioremediation of Al-Sayyadin Lagoon polluted water using wild and mutant strains of microalgae

“…About the resistance of microalgae, it was found that, microalgae are able to survive short-term unpredictable environmental stress by means of physiological acclimatization as a result of the modification of gene expression (Bradshaw and Hardwick, 1989;Fogg, 2001;Costas et al, 2008). However, when environmental stress exceeds physiological limits, only the occurrence of mutations that confers resistance can allow adaptation (Costas et al, 2001). More and more examples accumulate on rapid adaptation of microalgae to extreme environments through the selection of rare spontaneous mutations conferring resistance which affects only one gene.…”

Highly Specific Biosensors to Herbicides, Based on Sensitive- and Resistant-Mutants of Microalgae

“…Using diverse functional and taxonomic groups, a screening of phytoplankters has been addressed to isolate strains highly herbicide-sensitive Costas et al, 2001;López-Rodas et al, 2007;Marvá et al, 2010;Huertas et al, 2010). The toxic effect of the herbicides has been estimated by calculating the inhibition of the acclimated maximal growth rate (m) in mid-log exponentially growing cells, in the presence of increasing concentrations of herbicides (diuron, simazine, diquat, glyphosate and others), by using the equation of Crow and Kimura (1970): m = Log e (N t /N 0 )/t where N t and N 0 are the cell numbers at the end and at the start of the experiment, respectively, and t, is the time that cultures were exposed to different doses of herbicides.…”

Genetic Adaptation of Phytoplankters to Herbicides

“…But after being further incubated a few cultures became green again, due to the growth of variants that were resistant to the herbicides. By using the fluctuation analysis, we demonstrated that resistance in different species of phytoplankters was due to the arising of new genetic variants caused by rare spontaneous mutation occurring randomly during propagation under non-selective conditions for the herbicides DCMU, glyphosate, simazine and diquat López-Rodas et al, 2001, 2007Marvá et al, 2010;see Table 1 shows the figures of mutation rate from herbicide-sensitivity to herbicide-resistance in different species of phytoplankters (ranging from 0.4 to 17.9 mutants per 10 6 cells per generation, depending of the species and the herbicide). Since mutation is recurrent in each generation, new mutant cells are arising continuously.…”

“…1). A modified fluctuation analysis for application to liquid cultures with phytoplankters López-Rodas et al, 2001) has been used to investigate the origin of herbicide-resistant cells. The modification of the analysis involves the use of liquid medium containing the selective agent (different kind of herbicides) rather than plating on a solid medium, as was done by Luria & Delbrück (1943) with bacterial cultures.…”