Resistance of microalgae to modern water contaminants as the result of rare spontaneous mutations

Resistance to glyphosate in the cyanobacterium Microcystis aeruginosa as result of pre-selective mutations

“…Adaptation of cyanobacteria and algae, which are the principal primary producers of aquatic ecosystems, to environmental changes resulting from anthropogenic contamination (or even to extreme natural environments) seems to be the result of a rare event: the spontaneous mutation from sensitivity to resistance that occurs randomly prior to the cells coming into contact with the selective agent (Costas et al 2001;Ló pez-Rodas et al 2001;Baos et al 2002;García-Villada et al 2002FloresMoya et al 2005). The rate of mutation from G s fi G r (from 3.1 · 10 -7 to 3.6 · 10 -7 mutants per cell per generation) was one to two orders of magnitude lower than the mutation rates we have described (from 2.12 · 10 -5 to 1.76 · 10 -6 mutants per cell per generation) for the resistance to several biocides in other cyanobacterial and microalgal species (Costas et al 2001;Ló pez-Rodas et al 2001;Baos et al 2002;García-Villada et al, 2002, but of the same order of magnitude found for the resistance to sulphureous waters in the chlorophycean Spirogyra insignis (2.7 · 10 -7 mutants per cell per generation) (Flores-Moya et al 2005). Nevertheless, the pre-selective G s fi G r mutations are sufficiently frequent in M. aeruginosa populations to allow them to adapt to the presence of glyphosate in culture.…”

“…A modified Luria-Delbrü ck analysis was performed as previously described (Ló pez- Rodas et al 2001) to distinguish resistant cells that had their origin in random spontaneous pre-selective mutations (prior to glyphosate exposure) from those arising through acquired post-selective adaptation (during the exposure to glyphosate) (Fig. 1).…”

Adaptation of Phytoplankton to Novel Residual Materials of Water Pollution: An Experimental Model Analysing the Evolution of an Experimental Microalgal Population Under Formaldehyde Contamination

“…The mutation rate from formaldehyde susceptibility to formaldehyde resistance in D. chlorelloides (3.61 9 10 -6 divisions) was found to be on the same order of magnitude than mutation rates we have described for resistance to many other biocides in chlorophyta López-Rodas et al 2001;Baos et al 2002;García-Villada et al 2002), significantly higher than mutation rates for SET 1 (105 tubes) They were allowed to grow, before adding the substance in study, till they reached the number of 4.2 9 10 5 cells. Set 2 consists on 25 tubes control with 4.2 9 10 5 cells that directly incorporated the studied product.…”

A novel approach to improve specificity of algal biosensors using wild-type and resistant mutants: an application to detect TNT

“…In the present work, the occurrence of resistant mutants to a given contaminant, appeared by rare spontaneous mutations (Costas et al, 1998López-Rodas et al, 2001;García-Villada et al, 2002), has been used as a new approach to give specificity to algal biosensors. These resistant mutants were obtained by a modified Luria-Delbrück fluctuation analysis (Luria and Delbrück, 1943).…”

“…Luria-Delbrück's procedure was originally developed as a combined experimental and statistical approach to study the occurrence of resistant variants in bacterial populations. Subsequent theoretical and experimental studies have modified the fluctuation test to be used with a wide group of organisms, from bacteria to human cells (Cole et al, 1976;Jones et al, 1994;Rossman et al, 1995;Asteris and Sarkar, 1996;Crane et al, 1996), including microalgae López-Rodas et al, 2001;García-Villada et al, 2002).…”