title: How eukaryotic algae can adapt to the Spain's Rio Tinto: a neo-Darwinian proposal for rapid adaptation to an extremely hostile ecosystem.
abstract: Microalgae contributed 60% of the total biomass in the extremely hostile (pH 2 and metal-rich waters) environment of Rio Tinto (which is used as a model for the astrobiology of Mars). These algae are closely related to nonextreme lineages, suggesting that adaptation to Rio Tinto water (RTW) must occur rapidly. Fitness from both the microalga Dictyosphaerium chlorelloides and the cyanobacterium Microcystis aeruginosa was inhibited when they were cultured in RTW. After further incubation for several weeks, D. chlorelloides survived, as a result of the growth of a variant that was resistant to RTW, but RTW-resistant cells did not appear in M. aeruginosa. A Luria-Delbrück fluctuation test revealed that D. chlorelloides RTW-resistant cells arose randomly by rare spontaneous mutations before the RTW exposure (1.38 x 10(-6) mutants per cell division). The mutants with a diminished fitness are maintained in nonextreme waters as the result of a balance between new RTW-resistant cells arising by mutation and RTW-resistant mutants eliminated by natural selection (equilibrium at c. 15 RTW-resistant per 10(7) wild-type cells). Rapid adaptation of eukaryotic algae to RTW could be the result of selection of RTW-resistant mutants occurring spontaneously in nonextreme populations that arrived fortuitously at the river in the past, or in the present continuously.
authors.affiliation: Genética (Producción Animal), Facultad de Veterinaria, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Costas
authors.affiliation: Biología Vegetal (Botánica), Facultad de Ciencias, Universidad de Málaga, E-29071 Málaga, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Flores-Moya
authors.affiliation: Genética (Producción Animal), Facultad de Veterinaria, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: Nieves
authors.initials: N
authors.lastname: Perdigones
authors.affiliation: Genética (Producción Animal), Facultad de Veterinaria, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: Emilia
authors.initials: E
authors.lastname: Maneiro
authors.affiliation: Microbiología (Sanidad Animal), Facultad de Veterinaria, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Blanco
authors.affiliation: Microbiología (Sanidad Animal), Facultad de Veterinaria, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: Marta Eulalia
authors.initials: ME
authors.lastname: García
authors.affiliation: Genética (Producción Animal), Facultad de Veterinaria, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: Victoria
authors.initials: V
authors.lastname: López-Rodas
mesh_terms: D000143:Acids; D000222:Adaptation, Physiological / Q000235:genetics*; D005075:Biological Evolution; D017753:Ecosystem; D056890:Eukaryota / Q000235:genetics* / Q000502:physiology*; D045483:Rivers / Q000737:chemistry*; D013030:Spain; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000143:Acids; D014867:Water