miun.sePublications
Link to record
Permanent link

Direct link
BETA
Pocock, Tessa
Publications (10 of 16) Show all publications
Pocock, T. & Falk, S. (2014). Negative Impact on Growth and Photosynthesis in the Green Alga Chlamydomonas reinhardtii in the Presence of the Estrogen 17alpha-Ethynylestradiol. PLoS ONE, 9(10), e109289.
Open this publication in new window or tab >>Negative Impact on Growth and Photosynthesis in the Green Alga Chlamydomonas reinhardtii in the Presence of the Estrogen 17alpha-Ethynylestradiol
2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 10, e109289- p.Article in journal (Refereed) Published
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.

National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-23216 (URN)10.1371/journal.pone.0109289 (DOI)000343210300042 ()25310092 (PubMedID)2-s2.0-84907895409 (Scopus ID)1932-6203 (Electronic) 1932-6203 (Linking) (ISBN)
Available from: 2014-10-15 Created: 2014-10-15 Last updated: 2017-12-05Bibliographically approved
Pocock, T., Vetterli, A. & Falk, S. (2011). Evidence for phenotypic plasticity in the Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241. Journal of Experimental Botany, 62(3), 1169-1177.
Open this publication in new window or tab >>Evidence for phenotypic plasticity in the Antarctic extremophile Chlamydomonas raudensis Ettl. UWO 241
2011 (English)In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 62, no 3, 1169-1177 p.Article in journal (Refereed) Published
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.

Keyword
Acclimation; Antarctica; Chlamydomonas raudensis; climate change; phenotypic plasticity; photostasis; PSII excitation pressure
National Category
Botany
Identifiers
urn:nbn:se:miun:diva-12178 (URN)10.1093/jxb/erq347 (DOI)000286464600026 ()21041369 (PubMedID)2-s2.0-79251532057 (Scopus ID)
Available from: 2010-11-03 Created: 2010-11-02 Last updated: 2017-12-12Bibliographically approved
Pocock, T., Koziak, A., Rosso, D., Falk, S. & Hüner, N. (2007). Chlamydomonas raudensis Ettl. (UWO241) exhibits the capacity for rapid D1 repair in response to chronic photoinhibition at low temperature. Journal of Phycology, 43(5), 924-936.
Open this publication in new window or tab >>Chlamydomonas raudensis Ettl. (UWO241) exhibits the capacity for rapid D1 repair in response to chronic photoinhibition at low temperature
Show others...
2007 (English)In: Journal of Phycology, ISSN 0022-3646, E-ISSN 1529-8817, Vol. 43, no 5, 924-936 p.Article in journal (Refereed) Published
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.

Keyword
photoinhibition, low temperature, Chlamydomonas raudensis
National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-4414 (URN)10.1111/j.1529-8817.2007.00380.x (DOI)000249827400008 ()2-s2.0-34848917534 (Scopus ID)5468 (Local ID)5468 (Archive number)5468 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2017-12-12Bibliographically approved
Pocock, T., Sane, P., Falk, S. & Huner, N. P. (2007). Excitation pressure regulates the activation energy for recombination events in the photosystem II reaction centres of Chlamydomonas reinhardtii. Biochemistry and Cell Biology, 85(6), 721-729.
Open this publication in new window or tab >>Excitation pressure regulates the activation energy for recombination events in the photosystem II reaction centres of Chlamydomonas reinhardtii
2007 (English)In: Biochemistry and Cell Biology, ISSN 0829-8211, E-ISSN 1208-6002, Vol. 85, no 6, 721-729 p.Article in journal (Refereed) Published
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.

Keyword
Excitation pressure, PS II, Chlamydomonas reinhardtii, activation energy
National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-4358 (URN)10.1139/O07-144 (DOI)000252316300007 ()2-s2.0-38849102227 (Scopus ID)5469 (Local ID)5469 (Archive number)5469 (OAI)
Note

vR-Medicine, Internal

Available from: 2008-12-09 Created: 2008-12-09 Last updated: 2017-12-12Bibliographically approved
Pocock, T., Huner, N. P. .. & Falk, S. (2007). Salinity alters stress responses in an Antarctic extremophilic alga.: Aquafluo workshop 2007. .
Open this publication in new window or tab >>Salinity alters stress responses in an Antarctic extremophilic alga.: Aquafluo workshop 2007
2007 (English)Conference paper, Published paper (Other scientific)
Keyword
Stress response, low temperature, antarctic alga, Chlamydomonas raudensis
National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-1023 (URN)5471 (Local ID)5471 (Archive number)5471 (OAI)
Available from: 2008-09-30 Created: 2008-09-30Bibliographically approved
Gylle, A. M., Nygård, C. A., Pocock, T. & Ekelund, N. G. A. (2007). Salinity effect on oxygen evolution and the relative amount of RuBisCO in the brackish Fucus vesiculosus L. (Phaeophyceae). In: Pysiological responses of marine and brackish Fucuc vesiculosus L with respect to salinity (pp. 1-8). Sundsvall: Mittuniversitetet.
Open this publication in new window or tab >>Salinity effect on oxygen evolution and the relative amount of RuBisCO in the brackish Fucus vesiculosus L. (Phaeophyceae)
2007 (English)In: Pysiological responses of marine and brackish Fucuc vesiculosus L with respect to salinity, Sundsvall: Mittuniversitetet , 2007, 1-8 p.Chapter in book (Other academic)
Abstract [en]

The sublittoral Fucus vesiculosus from the brackish Bothnian Sea is adapted to a salinity of 4-5 practical salinity units (psu). This study investigated the effect of different salinities (5, 10, 20 and 35 psu) on maximum photosynthetic capacity (Pmax) and the relative amount of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). The results revealed a higher Pmax at higher salinities with the maximum at 10 psu. Higher salinities also resulted in increased relative amounts of Rubisco but this was not well correlated with the increased Pmax. Therefore, the amount of Rubisco doesn�t appear to be the main reason for the increased Pmax in higher salinities.

Place, publisher, year, edition, pages
Sundsvall: Mittuniversitetet, 2007
Series
Mid Sweden University Licentiate Thesis, ISSN 1652-8948 ; 19 [Paper IV]
Keyword
brackish, oxygen evolution, photosynthesis, Rubisco, salinity, Fucus vesiculosus immunoblotting.
National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-5936 (URN)4912 (Local ID)978-91-85317-41-7 (ISBN)4912 (Archive number)4912 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2013-01-10Bibliographically approved
Falk, S., Pocock, T., Vetterli, A. & Huner, N. (2007). Synergistic effects of salinity and temperature in an extremophilic Antarctic alga (Chlamydomonas raudensis UWO 241). Photosynt. Res. 91: 298-299. In: Proceedings from the 14th International Conference on Photosynthesis, Glasgow, 2007: Published in Photosynthesis Research, vol 91: 298-299. Paper presented at 14th International Conference on Photosynthesis (pp. 298-299). .
Open this publication in new window or tab >>Synergistic effects of salinity and temperature in an extremophilic Antarctic alga (Chlamydomonas raudensis UWO 241). Photosynt. Res. 91: 298-299
2007 (English)In: Proceedings from the 14th International Conference on Photosynthesis, Glasgow, 2007: Published in Photosynthesis Research, vol 91: 298-299, 2007, 298-299 p.Conference paper, Published paper (Other academic)
National Category
Botany
Identifiers
urn:nbn:se:miun:diva-10348 (URN)
Conference
14th International Conference on Photosynthesis
Available from: 2009-11-16 Created: 2009-11-16 Last updated: 2010-02-25Bibliographically approved
Morgan-Kiss, R., Priscu, J., Pocock, T., Gudynaite-Savitch, L. & Huner, N. (2006). Adaptation and acclimation of photosynthetic microorganisms to permanently cold environments. Microbiology and molecular biology reviews, 70(1), 222-252.
Open this publication in new window or tab >>Adaptation and acclimation of photosynthetic microorganisms to permanently cold environments
Show others...
2006 (English)In: Microbiology and molecular biology reviews, ISSN 1092-2172, E-ISSN 1098-5557, Vol. 70, no 1, 222-252 p.Article, review/survey (Refereed) Published
Abstract [en]

Persistently cold environments constitute one of our worlds largest ecosystems, and microorganisms dominate the biomass and metabolic activity in these extreme environments. The stress of low temperatures on life is exacerbated in organisms that rely on photoautrophic production of organic carbon and energy sources. Phototrophic organisms must coordinate temperature-independent reactions of light absorption and photochemistry with temperature-dependent processes of electron transport and utilization of energy sources through growth and metabolism. Despite this conundrum, phototrophic microorganisms thrive in all cold ecosystems described and (together with chemoautrophs) provide the base of autotrophic production in low-temperature food webs. Psychrophilic (organisms with a requirement for low growth temperatures) and psychrotolerant (organisms tolerant of low growth temperatures) photoautotrophs rely on low-temperature acclimative and adaptive strategies that have been described for other low-temperature-adapted heterotrophic organisms, such as cold-active proteins and maintenance of membrane fluidity. In addition, photoautrophic organisms possess other strategies to balance the absorption of light and the transduction of light energy to stored chemical energy products (NADPH and ATP) with downstream consumption of photosynthetically derived energy products at low temperatures. Lastly, differential adaptive and acclimative mechanisms exist in phototrophic microorganisms residing in low-temperature environments that are exposed to constant low-light environments versus high-light- and high-UV-exposed phototrophic assemblages.

National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-8692 (URN)10.1128/MMBR.70.1.222-252.2006 (DOI)000236410100008 ()16524924 (PubMedID)2-s2.0-33645112699 (Scopus ID)
Available from: 2009-02-26 Created: 2009-02-26 Last updated: 2016-09-28Bibliographically approved
Pocock, T., Vetterli, A., Huner, N. & Falk, S. (2006). Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis. In: International conference on alpine and polar microbiology, Insbruck Austria 2006. .
Open this publication in new window or tab >>Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis
2006 (English)In: International conference on alpine and polar microbiology, Insbruck Austria 2006, 2006Conference paper, Published paper (Other scientific)
Keyword
Photosynthesis, psychrophile, salinity, growth, photochemistry
National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-4192 (URN)4882 (Local ID)4882 (Archive number)4882 (OAI)
Available from: 2008-09-30 Created: 2008-09-30Bibliographically approved
Carlsson, F., Vetterli, A., Pocock, T., Ekelund, N. & Falk, S. (2005). A comparative study including Clamydomonas reinhardtii and Chlamydomonas raudensis Ettl. strains SAG 49.72 and UWO 241 focusing on phototaxis.. In: Proceedings of the 6th European Workshop Biotechnology of Microalgae. .
Open this publication in new window or tab >>A comparative study including Clamydomonas reinhardtii and Chlamydomonas raudensis Ettl. strains SAG 49.72 and UWO 241 focusing on phototaxis.
Show others...
2005 (English)In: Proceedings of the 6th European Workshop Biotechnology of Microalgae, 2005Conference paper, Published 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.

Keyword
Phototaxis algae Chlamydomonas reinhardtii Chlamydomonas raudensis temperature light
National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-3668 (URN)3781 (Local ID)3781 (Archive number)3781 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2011-04-06Bibliographically approved
Organisations
Identifiers

Search in DiVA

Show all publications