Disentangling mechanisms involved in the adaptation of the cyanobacterium Microcystis aeruginosa to the extreme sulphureous water from Los Baños de la Hedionda (S Spain)

Abstract

Backgrounds Los Baños de la Hedionda (Málaga, S Spain) is a natural sulphureous spa where sulphide can reach a concentration of 150-200 µM. Although this ion has biocide properties, including inhibition of the photosynthetic process, a rich flora can be found in this extreme environment. Objectives To study the adaptation mechanisms allowing resistance of photosynthetic microorganisms to these sulphureous waters Methods For this purpose, a modified Luria–Delbrück fluctuation analysis was carried out. The adaptation to La Hedionda waters of three different strains of the cyanobacterium Microcystis aeruginosa (Kützing) Kützing (isolated from a non-sulphureous freshwater reservoir) was analyzed in order to find out if it was achieved by a physiological adaptation process (acclimation) or by the selection of rare spontaneous mutations (genetic adaptation). Conclusions Several resistant strains were obtained after 6 weeks of cultivation with La Hedionda waters. The fluctuation analysis showed that genetic adaptation was the phenomenon that allowed resistant M. aeruginosa cells from the three strains to survive, with similar mutation rates in the order of magnitude of 1 mutant resistant cell per 106-107 cell division-1. It could be hypothesized that this cyanobacterium could adapt to sulphureous environment by the selection of favoured mutants.