@article{SpijkermanBaruaGerloffEliasetal.2007,
  author    = {Spijkerman, Elly and Barua, Deepak and Gerloff-Elias, Antje and Gaedke, Ursula and Heckathorn, S. A.},
  title     = {Stress responses and metal tolerance of Chlamydomonas acidophila in metal-enriched lake water and artificial medium},
  doi       = {10.1007/s00792-007-0067-0},
  year      = {2007},
  abstract  = {Chlamydomonas acidophila faces high heavy-metal concentrations in acidic mining lakes, where it is a dominant phytoplankton species. To investigate the importance of metals to C. acidophila in these lakes, we examined the response of growth, photosynthesis, cell structure, heat-shock protein (Hsp) accumulation, and metal adsorption after incubation in metal-rich lake water and artificial growth medium enriched with metals (Fe, Zn). Incubation in both metal-rich lake water and medium caused large decreases in photosystem II function (though no differences among lakes), but no decrease in growth rate (except for medium + Fe). Concentrations of small Hsps were higher in algae incubated in metal-rich lake- water than in metal-enriched medium, whereas Hsp60 and Hsp70A were either less or equally expressed. Cellular Zn and Fe contents were lower, and metals adsorbed to the cell surface were higher, in lake-water-incubated algae than in medium- grown cells. The results indicate that high Zn or Fe levels are likely not the main or only contributor to the low primary production in mining lakes, and multiple adaptations of C. acidophila (e.g., high Hsp levels, decreased metal accumulation) increase its tolerance to metals and permit survival under such adverse environmental conditions. Supposedly, the main stress factor present in the lake water is an interaction between low P and high Fe concentrations.},
  language  = {en}
}
@article{GerloffEliasSpijkermanSchubert2005,
  author    = {Gerloff-Elias, Antje and Spijkerman, Elly and Schubert, H.},
  title     = {Light acclimation of Chlamydomonas acidophila accumulating in the hypolimnion of an acidic lake (pH 2.6)},
  issn      = {0046-5070},
  year      = {2005},
  abstract  = {1. The unicellular green alga Chlamydomonas acidophila accumulates in a thin phytoplankton layer in the hypolimnion (deep chlorophyll maximum, DCM) of an extremely acidic lake (Lake 111, pH 2.6, Lusatia, Germany), in which the underwater light spectrum is distorted and red-shifted. 2. Chlamydomonas acidophila exhibited a significantly higher absorption efficiency and a higher cellular chlorophyll b content when incubated in the red shifted underwater light of Lake 111 than in a typical, blue-green dominated, light spectrum. 3. Chlamydomonas acidophila has excellent low light acclimation properties (increased chlorophyll b content, increased oxygen yield and a low light saturation point for photosynthesis) that support survival of the species in the low light climate of the DCM. 4. In situ acclimation to the DCM under low light and temperature decreased maximum photosynthetic rate in autotrophic C. acidophila cultures, whereas the presence of glucose under these conditions enhanced photosynthetic efficiency and capacity. 5. The adaptive abilities of C. acidophila to light and temperature shown in this study, in combination with the absence of potent competitors because of low lake pH, most probably enable the unusual dominance of the green alga in the DCM of Lake 111},
  language  = {en}
}
@article{GerloffEliasSpijkermanProschold2005,
  author    = {Gerloff-Elias, Antje and Spijkerman, Elly and Proschold, T.},
  title     = {Effect of external pH on the growth, photosynthesis and photosynthetic electron transport of Chlamydomonas acidophila Negoro, isolated from an extremely acidic lake (pH 2.6)},
  issn      = {0140-7791},
  year      = {2005},
  abstract  = {In extremely acidic lakes, low primary production rates have been measured. We assumed that proton stress might explain these observations and therefore investigated the photosynthetic behaviour of a Chlamydomonas species, a main primary producer in acidic lakes, over a range of pH values. Identified as C. acidophila using small subunit rDNA analysis, this species is identical to other isolates from acidic environments in Europe and South America, suggesting a worldwide distribution. Laboratory experiments with C. acidophila, revealed a broad pH-tolerance for growth and photosynthesis, the lower pH limit lying at pH 1.5 and the upper limit at pH 7. Growth rates at optimum pH conditions (pH 3 and 5) were equal to those of the mesophilic Chlamydomonas reinhardtii. In contrast, photosynthetic rates were significantly higher, suggesting that higher photosynthetic rates compensated for higher dark respiration rates, as confirmed experimentally. Electron transport capacities of PSI and PSII, P700(+) re-reduction times and measurements of PSII fluorescence revealed the induction of alternative electron transport mechanisms, such as chlororespiration, state transitions and cyclic electron transport, only at suboptimal pH values (pH 1.5; 4 and 6-7). The results indicate, that C. acidophila is well adapted to low pH and that the relatively low primary production rates are not a result of pH stress},
  language  = {en}
}
@article{GerloffEliasBaruaMoelichetal.2006,
  author    = {Gerloff-Elias, Antje and Barua, Deepak and M{\"o}lich, Andreas and Spijkerman, Elly},
  title     = {Temperature- and pH-dependent accumulation of heat-shock proteins in the acidophilic green alga Chlamydomonas acidophila},
  issn      = {0168-6496},
  doi       = {10.1111/j.1574-6941.2006.00078.x},
  year      = {2006},
  abstract  = {Chlamydomonas acidophila, a unicellular green alga, is a dominant phytoplankton species in acidic water bodies, facing severe environmental conditions such as low pH and high heavy metal concentrations. We examined the pH-, and temperature-dependent accumulation of heat-shock proteins in this alga to determine whether heat-shock proteins play a role in adaptation to their environment. Our results show increased heat-shock proteins accumulation at suboptimal pHs, which were not connected with any change in intracellular pH. In comparison to the mesophilic Chlamydomonas reinhardtii, the acidophilic species exhibited significantly higher accumulations of heat-shock proteins under control conditions, indicating an environmental adaptation of increased basal levels of heat-shock proteins. The results suggest that heat- shock proteins might play a role in the adaptation of C. acidophila, and possibly other acidophilic algae, to their extreme environment},
  language  = {en}
}