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  • 1. Axblom, Caroline
    et al.
    Grönlund, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Astaxanthin from microalgae: effects of temperature and nutrient stress on production in the green alga Haematococcus lacustris1999In: 4th international Ecological Engineering conference: Manging the Wastewater Resource, June 7-11, Aas, Norway, 1999Conference paper (Other academic)
  • 2. Carlsson, F.
    et al.
    Vetterli, A.
    Pocock, Tessa
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    A comparative study including Clamydomonas reinhardtii and Chlamydomonas raudensis Ettl. strains SAG 49.72 and UWO 241 focusing on phototaxis.2005In: Proceedings of the 6th European Workshop Biotechnology of Microalgae, 2005Conference paper (Other academic)
    Abstract [en]

    Phototaxis is movement induced by light; this phenomenon has been detected in several solitary green algae species and generally works as a balancing force against gravitaxis, creating a system for optimum vertical placing in relation to irradiance, (energy -demands/restrictions). We study phototaxis in the mesophilic green algae, Chlamydomonas reinhardtii and C. raudensis SAG 49.72, relative to phototaxis in the from Antarctica newly isolated obligate psychrophilic strain of C. Raudensis (UWO 241) (henceforth called UWO 241). This species has some unusual movement patterns (Pocock et. al 2004) which function is yet to be revealed. Phototactic movement has not earlier been monitored in the normal conditions (high salinity, low temperature) for this strain, though when exposed to extreme temperatures (25C) the organism displays movement patterns interpreted as positive phototaxis. (Pocock et. al 2004). This behaviour should lead to a more rapid destruction of the organism due to the damaging high light (high energy input). The study shows that the three species responds different to light stimuli, when temperature is set to 12 C (culturing temperature) or the respective optimum culture temperatures. Light response curves of phototaxis in the range of 0,5 to 3000 μmol quanta m-2 s-1, shows that C. raudensis SAG 49.72 produce positive phototaxis over the entire range while C. reinhardtii mainly shows negative reactions. UWO 241 seem to be unaffected by irradiance, thus showing only nondirectional behaviour. In a second set of experiments the cells were kept in Petri dishes and exposed to 3000 μmol quanta m-2 s-1 under 40 min, in a temperature range of 5C to 25C for each sample. The results show that C. reinhardtii was negatively phototactic at 5C, switching to positive phototaxis at 25C.

  • 3.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Competition for photosynthetic energy between CO2- and NH4+-uptake in Selenastrum minutum: 5th European workshop on biotechnology in algae2003Conference paper (Other scientific)
  • 4.
    Falk, Stefan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Pocock, Tessa
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Vetterli, Adrien
    Huner, N.P.A.
    Synergistic effects of salinity and temperature in an extremophilic Antarctic alga (Chlamydomonas raudensis UWO 241). Photosynt. Res. 91: 298-2992007In: Proceedings from the 14th International Conference on Photosynthesis, Glasgow, 2007: Published in Photosynthesis Research, vol 91: 298-299, 2007, 298-299 p.Conference paper (Other academic)
  • 5.
    Grönlund, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Craggs, R
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hanaeus, J
    Advanced pond system for wastewater treatment in cold climates: assessment of sustainability2002In: Algal Biotechnology - A Sea of Opportunities,: the 1st congress of the International Society for Applied Phycology, 26-30 May 2002 at Aguadulce, Roquetas de Mar. Universidad de Almeria, Almeria, Spain, Almería :: Univ. de Almería, Servicio de Publ , 2002, 310- p.Conference paper (Other academic)
  • 6.
    Grönlund, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hanaeus, J
    Produktiv rening med mikroalger i kallt klimat2002In: Vatten, ISSN 0042-2886, Vol. 58, 251-258 p.Article in journal (Other academic)
  • 7.
    Grönlund, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hanaeus, J
    Use of microalgae in wastewater treatment in cold climate2001In: Vatten, ISSN 0042-2886, Vol. 57, 135-145 p.Article in journal (Other academic)
  • 8.
    Grönlund, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hanæus, J
    Productive treatment of wastewater with microalgae in cold climate -laboratory experiments2001In: Ecological Engineering for Landscape Services and Products. The Annual Conference of the International Ecological Engineering Society, November 25th to 29th 2001, Christchurch, New Zealand., Christchurch, New Zealand, 2001Conference paper (Other academic)
  • 9.
    Grönlund, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Hanaeus, Jörgen
    Johansson, Erica
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Performance of an Experimental Wastewater Treatment High-Rate Algal Pond in Subarctic Climate2010In: Water environment research, ISSN 1061-4303, E-ISSN 1554-7531, Vol. 82, no 9, 830-839 p.Article in journal (Refereed)
    Abstract [en]

    A pilot-scale experimental high-rate algal pond (HRAP) was investigated in the subarctic mid-Sweden region, at latitude 63°N. During autumn 2002, conditions included temperatures below 10°C and photosynthetic active radiation below 200 µE/m2·s. Biochemical oxygen demand was reduced by approximately 90% (approximately 40 g/m3), chemical oxygen demand by 65% (approximately 80 g/m3), total phosphorus by 20% (approximately 1 g/m3), and total nitrogen by 46% (approximately 15 g/m3), at a retention time of approximately 2.5 days. During autumn 2003, the performance of the HRAP appeared better with a more dense microalgae culture; however, as a result of poor settling of the microalgae, the reduction was considerably lower. A major difference between the years was the microalgae composition. In 2002, the large green algae Coelastrum dominated with Chlamydomonas, Scenedesmus, Lagerheimia, and the Cryptophyte Rhodomonas. In 2003, there was a total dominance of the very small green algae Chlorella, known to be difficult to settle. In batch growth experiments during spring 2002, doubling times of 4 to 6 days were achieved. The period of temperatures above 10°C and an insolation of more than approximately 270 uE/m2·s (125 Langleys), which is well-documented as appropriate for HRAP function (<xref ref-type="bibr" rid="i1061-4303-82-9-830-Oswald2">Oswald, 1988a</xref>, <xref ref-type="bibr" rid="i1061-4303-82-9-830-Oswald4">1988c</xref>), were measured to last for 4 to 4.5 months from early May to late September. However, the growth and treatment performance experiments indicated that a longer season may be possible—6.5 to 7 months, at best—from early April to late October.

  • 10.
    Grönlund, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Johansson, E
    Hanaeus, J
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Seasonal microalgae variation in a subarctic wastewater stabilization pond using chemcial precipitation2004In: Vatten, ISSN 0042-2886, Vol. 60, no 4, 239-249 p.Article in journal (Refereed)
    Abstract [en]

    Surface water microalgae samples were collected during the ice-free period in a small subarctic wastewater stabilization pond system, complemented with chemical precipitation during the winter period (fellingsdam), and serving 310 persons. In the primary pond microalgae dominance alternated between the Cryptophyte Cryptomonas and green algae (Chlorophyta). In the second and third pond the general pattern was that Cryptomonas dominated during summer but was replaced by green algae in autumn and the following spring. Estimations of the microalgae part of the effluent COD and phosphorus showed that microalgae dominated these parameters for only 3-4 weeks of 12 evaluated. This does not support the reasoning behind the European Union directive of the use of filtered samples for effluent BOD, COD and SS from stabilization ponds, in contrast to other wastewater treatment methods. The reasons behind the EU's procedure for ponds are based on the assumption that stabilization ponds convert "sewage BOD" to "algal BOD". The results of this study suggest that further investigations of the microalgae function in subarctic wastewater stabilization ponds and fellingsdams should be conducted, before implementing the EC directive into Swedish law, or into similar laws in other countries with subarctic regions.

  • 11.
    Grönlund, Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Klang, Anders
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hanaeus, Jörgen
    Sustainability of wastewater treatment with microalgae in cold climate, evaluated with emergy and socio-ecological principles2004In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 22, no 3, 155-174 p.Article in journal (Refereed)
    Abstract [en]

    The sustainability of a microalgae wastewater treatment plant model (ALGA), assumed serving a small Swedish town with 10,000 inhabitants at latitude 60°N, was tested by comparing it to a conventional three-step treatment plant (WWTP), and a mechanical and chemical treatment plant (TP) complemented with a constructed wetland (TP + CW). Using two assessment methods—the socio-ecological principles method and emergy analysis—the ALGA model considered to have a better position for sustainable development, than the other two. In emergy terms the ALGA model had about half the resource use of the other two alternatives, and used most local free environmental resources, four times the TP + CW, and 100 times the WWTP. The violations against the second and third socio-ecological principles were considered equal for the three alternatives, the fourth was estimated to be in favor of the ALGA model, and the first principle was calculated to be in favor of the ALGA model with about eight times lower indicator value sum. Recirculation of nutrients back to society or production of economically viable products from the treatment by-products would strongly influence the sustainability. The ALGA model has a potential advantage due to interesting biochemical contents in the microalgae biomass, depending on what species will become dominating.

  • 12.
    Ljunggren, L
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Staffan, F
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Linden, B
    Mendes, J
    Weaning of juvenile pikeperch (Stizostedion lucioperca (L.)) and perch (Perca fluviatilis (L.)) to formulated feed.2003In: Aquaculture Research, ISSN 1355-557X, Vol. 34, no 4, 281-287 p.Article in journal (Refereed)
    Abstract [en]

    Weaning success of pond-cultured pikeperch and wild-caught perch (mean length 51 and 48 mm respectively) was evaluated using different weaning techniques and different formulated feeds. Juveniles that were fed formulated feed grew as well as or better than juveniles that were weaned successively using zooplankton or yolk. Four different formulated feeds (agglomerated marine larvae feed, marine larvae feed, trout feed and a semi-moist feed) were evaluated regarding specific growth rate (SGR), condition factor and a subjective stomach fullness estimate. The agglomerated marine larvae feed gave significantly better weaning performance than the other feeds regarding all parameters (SGR = 7.3% day(-1) and 3.4% day(-1) for pikeperch and perch respectively).

  • 13. Miskiewicz, E
    et al.
    Ivanov, AG
    Williams, JP
    Khan, MU
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Huner, NPA
    Photosynthetic acclimation of the Filamentous Cyanobacterium Plectonema boryanum UTEX 485 to Temperature and Light.2000In: Plant and Cell Physiology, ISSN 0032-0781, E-ISSN 1471-9053, Vol. 41, no 6, 767-775 p.Article in journal (Refereed)
    Abstract [en]

    Photosynthetic acclimation to temperature and irradiance was studied in the filamentous, non-heterocystous cyanobacterium Plectonema boryanum UTEX 485. Growth rates of this cyanobacterium measured at ambient CO2 were primarily influenced by temperature with minimal effects of irradiance. Both growth temperature and irradiance affected linolenic (18:3) and linoleic acid (18:2) levels in the four major lipid classes in an independent but additive manner. In contrast, photosynthetic acclimation was not due to either growth temperature or irradiance per se, but rather, due to the interaction of these environmental factors. P. boryanum grown at low temperature and moderate irradiance mimicked cells grown at high light. Compared to cells grown at either 29°C/150 μmol m-2 s-1 (29/150) or 15/10, P. boryanum grown at either 15/150 or 29/750 exhibited: (1) reduced cellular levels of Chl a and phycobilisomes (PBS), and concomitantly higher content of an orange-red carotenoid, myxoxanthophyll; (2) higher light saturated rates (Pmax) when expressed on a Chl a basis but lower apparent quantum yields of oxygen evolution and (3) enhanced resistance to high light stress. P. boryanum grown at 15/150 regained normal blue-green pigmentation within 16 h after a temperature shift to 29°C at a constant irradiance of 150 μmol m-2 s-1. DBMIB and KCN but not DCMU and atrazine partially inhibited the change in myxoxanthophyll/Chl a ratio following the shift from 15 to 29°C. We conclude that P boryanum responds to either varying growth temperature or varying growth irradiance by adjusting the ability to absorb light through decreasing the cellular contents of Chl a and light-harvesting pigments and screening of excessive light by myxoxanthophyll predominantly localized in the cell wall/cell membrane to protect PSII from over-excitation. The possible role of redox sensing/signalling for photosynthetic acclimation of cyanobacteria to either temperature or irradiance is discussed.

  • 14.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Smart Lighting ERC, Rensselaer Polytechnic InstituteTroy, NY, United States.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Negative Impact on Growth and Photosynthesis in the Green Alga Chlamydomonas reinhardtii in the Presence of the Estrogen 17alpha-Ethynylestradiol2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 10, e109289- p.Article in journal (Refereed)
    Abstract [en]

    It is well known that estrogenic compounds affect development of fertilized eggs of many species of birds, fish and amphibians through disrupted activity of carbonic anhydrase (CA). The most potent activity comes from the most commonly occurring synthetic sterol, 17alpha-Ethynylestradiol (EE2). Less is known about the responses of aquatic phytoplankton to these compounds. Here we show for the first time that, in comparision to the control, the addition of 7 microM EE2 reduced the growth rate of the green alga Chlamydomonas reinhardtii by 68% for cells grown at high CO2. When cells were grown in ambient air (low Ci) with a fully activated carbon concentrating mechanism through the induction of CA activity, the growth rates were reduced by as much as 119%. A reduced growth rate could be observed at EE2 concentrations as low as 10 pM. This was accompanied by a reduced maximum capacity for electron transport in photosystem II as determined by a lower FV/FM for low Ci-grown cells, which indicates the involvement of CAH3, a CA specifically located in the thylakoid lumen involved in proton pumping across the thylakoid membranes. These results were in agreement with an observed reduction in the chloroplastic affinity for Ci as shown by a strong increase in the Michaelis-Menten K0.5 for HCO3-. In itself, a lowering of the growth rate of a green alga by addition of the sterol EE2 warrants further investigation into the potential environmental impact by the release of treated waste water.

  • 15.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Huner, Norman P.A.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Salinity alters stress responses in an Antarctic extremophilic alga.: Aquafluo workshop 20072007Conference paper (Other scientific)
  • 16.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Koziak, Alexandra
    Rosso, Dominic
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hüner, Norman
    Chlamydomonas raudensis Ettl. (UWO241) exhibits the capacity for rapid D1 repair in response to chronic photoinhibition at low temperature2007In: Journal of Phycology, ISSN 0022-3646, E-ISSN 1529-8817, Vol. 43, no 5, 924-936 p.Article in journal (Refereed)
    Abstract [en]

    Maximum photosynthetic capacity indicates that the Antarctic psychrophile Chlamydomonas raudensis H. Ettl UWO 241 is photosynthetically adapted to low temperature. Despite this finding, C. raudensis UWO 241 exhibited greater sensitivity to low-temperature photoinhibition of PSII than the mesophile Chlamydomonas reinhardtii P. A. Dang. However, in contrast with results for C. reinhardtii, the quantum requirement to induce 50% photoinhibition of PSII in C. raudensis UWO 241 (50 μmol photons) was comparable at either 8°C or 29°C. To our knowledge, this is the first report of a photoautotroph whose susceptibility to photoinhibition is temperature independent. In contrast, the capacity of the psychrophile to recover from photoinhibition of PSII was sensitive to temperature and inhibited at 29°C. The maximum rate of recovery from photoinhibition of the psychrophile at 8°C was comparable to the maximum rate of recovery of the mesophile at 29°C. We provide evidence that photoinhibition in C. raudensis UWO 241 is chronic rather than dynamic. The photoinhibition-induced decrease in the D1 content in C. raudensis recovered within 30 min at 8°C. Both the recovery of the D1 content as well as the initial fast phase of the recovery of Fv/Fm at 8°C were inhibited by lincomycin, a chloroplast protein synthesis inhibitor. We conclude that the susceptibility of C. raudensis UWO 241 to low-temperature photoinhibition reflects its adaptation to low growth irradiance, whereas the unusually rapid rate of recovery at low temperature exhibited by this psychrophile is due to a novel D1 repair cycle that is adapted to and is maximally operative at low temperature.

  • 17.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Rosso, D
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hunter, NPA
    Recovery from photoinhibition in the low-light adapted psychrophilic green alga, Chlamydomonas raudensis (UWO 241).: 13th International Congress of Photosynthesis2004Conference paper (Other scientific)
  • 18.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Rosso, Dominic
    Koziak, A
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Huner, N P A
    Recovery from photoinhibition in the low light-adapted psychrophilic green alga Chlamydomonas raudensis (UWO 241).2004In: Photosynthesis: Fundamental Aspects to Global Perspectives.: Proceedings from the 13th International Congress on Photosynthesis., 2004, 525-527 p.Conference paper (Refereed)
  • 19.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sane, P.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Huner, N. P. A.
    Excitation pressure regulates the activation energy for recombination events in the photosystem II reaction centres of Chlamydomonas reinhardtii2007In: Biochemistry and Cell Biology, ISSN 0829-8211, E-ISSN 1208-6002, Vol. 85, no 6, 721-729 p.Article in journal (Refereed)
    Abstract [en]

    Using in vivo thermoluminescence, we examined the effects of growth irradiance and growth temperature on charge recombination events in photosystem IT reaction centres of the model green alga Chlamydomonas reinhardtii. We report that growth at increasing irradiance at either 29 or 15 degrees C resulted in comparable downward shifts in the temperature peak maxima (T-M) for S(2)Q(B)(-) charge pair recombination events, with minimal changes in S(2)Q(A)(-) recombination events. This indicates that such growth conditions decrease the activation energy required for S(2)QB(-) charge pair recombination events with no concomitant change in the activation energy for S(2)Q(A)(-) recombination events. This resulted in a decrease in the Delta T-M between S(2)Q(A)(-) and S(2)Q(B)(-) recombination events, which was reversible when shifting cells from low to high irradiance and back to low irradiance at 29 degrees C. We interpret these results to indicate that the redox potential of Q(B) was modulated independently of Q(A), which consequently narrowed the redox potential gap between Q(A) and Q(B) in photosystem II reaction centres. Since a decrease in the Delta T-M between S(2)Q(A)(-) and S(2)Q(B)(-) recombination events correlated with growth at increasing excitation pressure, we conclude that acclimation to growth under high excitation pressure narrows the redox potential gap between Q(A) and Q(B) in photosystem 11 reaction centres, enhancing the probability for reaction center quenching in C. reinhardtii. We discuss the molecular basis for the modulation of the redox state of Q(B), and suggest that the potential for reaction center quenching complements antenna quenching via the xanthophyll cycle in the photoprotection of C. reinhardtii from excess light.

  • 20.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Vetterli, A
    Huner, NPA
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis2006In: International conference on alpine and polar microbiology, Insbruck Austria 2006, 2006Conference paper (Other scientific)
  • 21.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Vetterli, A.
    Huner, N.P.A.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic psychrophile Chlamydomonas raudensis UWO 241.2005In: ICPEP-3: Proceedings of the 3rd International Conference on Plants and Environmental Pollution. Lucknow, India. Nov 28-Dec 2, 2005, 2005Conference paper (Other scientific)
  • 22.
    Pocock, Tessa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Vetterli, Adrien
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Evidence for phenotypic plasticity in the Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 2412011In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 62, no 3, 1169-1177 p.Article in journal (Refereed)
    Abstract [en]

    Life in extreme environments poses unique challenges to photosynthetic organisms. The ability for an extremophilic green alga and its genetic and mesophilic equivalent to acclimate to changes in their environment was examined to determine the extent of their phenotypic plasticities. The Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241 (UWO) was isolated from an ice-covered lake in Antarctica, whereas its mesophilic counterpart C. raudensis Ettl. SAG 49.72 (SAG) was isolated from a meadow pool in the Czech Republic. The effects of changes in temperature and salinity on growth, morphology, and photochemistry were examined in the two strains. Differential acclimative responses were observed in UWO which include a wider salinity range for growth, and broader temperature- and salt-induced fluctuations in Fv/Fm, relative to SAG. Furthermore, the redox state of the photosynthetic electron transport chain, measured as 1–qP, was modulated in the extremophile whereas this was not observed in the mesophile. Interestingly, it is shown for the first time that SAG is similar to UWO in that it is unable to undergo state transitions. The different natural histories of these two strains exert different evolutionary pressures and, consequently, different abilities for acclimation, an important component of phenotypic plasticity. In contrast to SAG, UWO relied on a redox sensing and signalling system under the growth conditions used in this study. It is proposed that growth and adaptation of UWO under a stressful and extreme environment poises this extremophile for better success under changing environmental conditions.

  • 23. Vetterli, A
    et al.
    Carlsson, F
    Pocock, Tessa
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The effect of salinity on the growth and photosynthesis of a novel psychrophilic and halotolerant Chlamydomonas species from Antarctica2005In: Proceedings. 6th European Workshop Biotechnology of Microalgae, 2005Conference paper (Other scientific)
    Abstract [en]

    The effect of salt on the green alga Chlamydomonas raudensis Ettl (UWO241) was investigated. This physchrophilic alga was discovered in a permanently ice-covered lake in Antarctica in the beginning of the 90's and was then classified as Chlamydomonas subcaudata. A phylogenetic study by Pocock et al. (2004) revealed that this alga was in fact a C.raudensis species. The latter type species was first discovered in an alpine meadow in Czech republic and kept in the SAG culture collection as strain number 49.72. The aim of this study was to use the potential high sensitivity of the extremophile to understand the effect of salinity on photosynthesis of phytoplankton in the oceans, where microalgae play a key role in the carbon cycle on earth. It has to be determined if global warming, which is leading to the melting of the north ice cap and thus to the dilution of the North Atlantic ocean will have a negative impact on algal populations. This study lays the foundations for a larger study, which focuses on the compounds released by these green algae that could potentially counteract the greenhouse effect by increasing the albedo on earth. The study includes a comparison of C. raudensis UWO241 (psychrophilic strain) with C. raudensis SAG 49.72 (mesophilic strain) and the model organism C.reinhardtii, (mesophile). Also none of the latter two are known to be halotolerant. The growth kinetics of the three species has been investigated at different salinities ranging from 2 µM to 200 mM NaCl and between 24°C and 28°C for the mesophiles and from 2 µM to 850 mM at 8°C for the psychrophile. All algae were grown under 20 μmol quanta m-2 s-1 irradiance. Furthermore, chlorophyll a fluorescence was used to determine the stress level caused by the salt on the three species.

1 - 23 of 23
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