title: Isolation of cobalt hyper-resistant mutants of Saccharomyces cerevisiae by in vivo evolutionary engineering approach.
abstract: Cobalt is an important element with magnetic properties used in various industrial applications, but is also needed for biological activity. Very little is known about the cellular response of living systems to cobalt stress. Towards investigating this mechanism, we isolated individual Saccharomyces cerevisiae cells resistant to high cobalt concentrations up to 8 mmoll(-1), by employing four different 'in vivo' evolutionary engineering strategies: selection under constant or gradually increasing stress levels, and selection under continuous or pulse exposure to cobalt stress. Selection under continuous exposure to gradually increasing cobalt stress levels yielded the most resistant cell population to cobalt. However, the resistance was highly heterogeneous within the mutant populations ranging from 3- to 3700-fold survival rate of isolated individuals to 8 mmoll(-1) CoCl2 in the most resistant population. Moreover, cobalt-resistant individual colonies were associated with 2-4-times lower intracellular cobalt contents as compared to wild-type, and with cross-resistance to metals such as nickel, zinc, manganese, but not to copper and chromium ions. Contrary to mutants evolved under continuous exposure to cobalt, those isolated by pulse exposure strategy also exhibited resistance to heat shock and hydrogen peroxide stress. Taken together, this study reinforced the fact that evolutionary engineering is useful in selecting strains with very specific phenotypes, and further illustrated the importance of the strategy chosen to isolate the best evolved strain.
authors: Department of Molecular Biology and Genetics, Faculty of Science & Letters, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey. cakarp@itu.edu.tr
authors: Z Petek
authors: ZP
authors: Cakar
authors: Ceren
authors: C
authors: Alkim
authors: Burcu
authors: B
authors: Turanli
authors: Nilgün
authors: N
authors: Tokman
authors: Süleyman
authors: S
authors: Akman
authors: Mehmet
authors: M
authors: Sarikaya
authors: Candan
authors: C
authors: Tamerler
authors: Laurent
authors: L
authors: Benbadis
authors: Jean M
authors: JM
authors: François
mesh_terms: D002470:Cell Survival; D003035:Cobalt / Q000494:pharmacology*; D019020:Directed Molecular Evolution / Q000379:methods*; D025141:Drug Resistance, Fungal; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009154:Mutation; D009532:Nickel / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D003035:Cobalt; D009532:Nickel; D006861:Hydrogen Peroxide; C018021:cobaltous chloride