Adaptation of green microalgae to the herbicides simazine and diquat as result of pre-selective mutations

Comparative study on growth and photosynthetic pigment dynamics of two microalgae under the influence of water pollution with the herbicide glufosinate

“…Local strains of two green microalgal species, belonging to the same genus and widespread in variously polluted freshwater ponds: Scenedesmus acuminatus strain AICB 136 collected from the Tur creek near Cluj-Napoca, and Scenedesmus opoliensis strain AICB 141 originating in a pond of Săcălaia, Cluj county [5] were introduced in axenic monoalgal batch cultures, being grown in Bold's basal inorganic nutrient medium [14]. Cell cultures being at the beginning of the stationary phase of their population growth were used for initiation of the experiments.…”

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

“…Cyanobacteria, Chlorophyta, Bacillariophyta, Haptophyta isolated from continental, coastal and oceanic microalgae), simazine was able to inhibit 100% growth in all ancestral populations. Adaptation of simazine at doses of 3.1 ppm (or higher) was only possible because of the occurrence of rare spontaneous simazine-resistant mutants occurring randomly during replication of organisms before exposure to simazine (Marvá et al, 2010). Consequently, adaptations obtained by Huertas et al (2010) in the ratchet protocol (i.e.…”

“…The protocol aims at reaching equilibrium between strong selection intensity, by means of ratcheting to increase herbicide dose, and the maintenance of a population size 436 large enough to increase probability of rare spontaneous mutations that confer adaptation. These mutations occur randomly and not through specifically acquired adaptation included by herbicide (Marvá et al, 2010). From the herbicide dose-inhibition curve it is possible to calculate the lethal dose that inhibits each microalgae ancestral population (LD 100 ).…”

“…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

“…physiological adaptation, also called acclimatization; Bradshaw & Hardwick, 1989); however, some evolutionary studies in bacteria (Cairns et al, 1988;Foster, 2000;Roth et al, 2006) and yeasts (Heidenreich, 2007) have suggested that adaptive mutations could be a process resembling Lamarckism which, in the absence of lethal selection, produces mutations that relieve selective pressure. Finally, under lethal doses of Marvá et al, 2010) herbicides, genetic adaptation supported by selection of new genetic variants originated by spontaneous mutation (Sniegowski & Lenski, 1995;Belfiore & Anderson 2001;Orr, 2005) is the only possibility. Although it is assumed that this last mechanism is responsible for the arising of herbicide-resistant organisms, the empirical evidences are scarce.…”