69 Annales Universitatis Paedagogicae Cracoviensis Studia Naturae, 2: 69–80, 2017, ISSN 2543-8832 DOI: 10.24917/25438832.2.5 Katarzyna Możdżeń*, Patrycja Zagata Leśnicka, Mateusz Ślęczka, Magdalena Greczek-Stachura Institute of Biology, Pedagogical University of Kraków, Podchorążych 2 St., 30-084 Kraków, Poland, *katarzyna.mozdzen@up.krakow.pl The photosynthetic activity of Paramecium bursaria endosymbiotic algae in varying temperature conditions Introduction Microbial organisms are ideal to study adaptation to a variable environment. �ey are characterised by large population sizes, short generation time, and the ability to ma- nipulate their environment in controlled conditions (Jessup et al., 2004). Paramecium bursaria Ehrenberg 1831 is cosmopolitan organism, inhabiting stand- ing or slowly �owing water with relatively high purity. P. bursaria forms the endosym- biotic relationship with algae of Chlorella species (Reisser, 1980). �is relationship is an unusual example of optional and mutualist interaction between the two species. �ere are up to several hundred symbiotic algae inside the cell of P. bursaria (Kar- akashian et al., 1968) (Fig. 1). �e symbiotic algae are enclosed in a perialgal vacuole membrane (derived from the host digestive vacuole), and this membrane protects the algae from the hosts lysosomal digestion (Kodama, Fujishima, 2005). �e host cell protects endosymbionts from infections by Chlorella virus. Paramecium supply algal cells with nitrogen components and the CO2 necessary for photosynthesis (Reisser, 1980; Albers, Wiessner, 1985; Kodama, Fujishima, 2005). Green endosymbionts carry out photosynthesis and thus provide the host with maltose and oxygen (Brown, Niels- en, 1974); therefore, P. bursaria becomes completely or partially independent of the external source of food (Sommaruga, Sonntag, 2009). Endosymbionts inside P. bursaria are sensitive to di�erent environmental factors, e.g., temperature. Long-term exposure ciliates to low temperatures may cause changes in the early stages of development of their metabolism and consequently lead to the microorganisms extinction (unpublished). Global warming leads to changes in the process of photosynthesis and respiration in autotrophic organisms. PSII seems to be one of the most thermo-sensitive protein complex pigments, which regulates photo- synthetic activity in algae, cyanobacteria, as well as in higher plants (Strasser et al., S yl w ia Ś liw iń sk a- W ilc ze w sk a, A ga ta C ie sz yń sk a, A da m L at ał a 70 1995; Morgan-Kiss et al., 2006). Chlorella vulgaris Beijer. cells regulate photosynthetic processes at the level of LHCII polypeptides, chlorophyll molecules, as well as through the xanthophyll cycle, in response to di�erent temperatures and light intensities (Wil- son, Huner, 2000). �e aim of this study was to investigate the e�ects of temperatures (21°C, 24°C, 27°C, 30°C, and 33°C) on the photosynthesis carried out by endosymbiotic green al- gae of two P. bursaria strains from warm climate (Ardmore, USA) with an average annual temperature of +23.7°C (Ard7) and from cold climate (Kamchatka, Russia) with an average air temperature of -6°C (KD64). Fig. 1. Paramecium bursaria with green endosymbionts – A; endosymbiotic algae isolated from the Par- amecium bursaria cell – B (Photo. M. Ślęczka) 71 Material and methods �e experiments were conducted at the Institute of Biology of Pedagogical University of Kraków. �e study material was Paramecium bursaria strains from (1) Kamchatka (KD64) located in the Asian part of Russia (58°36ʹ40ʹʹN; 38°54ʹ44ʹʹE) and (2) Ard- more (Ard7) located in the south-eastern Carter County, Oklahoma, United States (34°10ʹ52ʹʹN; 97°07ʹ46ʹʹW). Paramecium bursaria culture techniques Green Paramecium bursaria strains were grown on a lettuce medium with Klebsiella pneumoniae (SMC strain) (Sonneborn, 1970). �e cultures were maintained under constant light/dark cycle (12L:12D) at 18°C, at light intensity 200 µmol m-2 s-1 for 7 days at the following temperatures: 21°C, 24°C, 27°C, 30°C and 33°C. Chlorophyll a �uorescence Chlorophyll a �uorescence was measured using a Handy Plant E�ciency Analyser �uorimeter (Hansatech Instruments, United Kingdom). A 1 ml sample, with green P. bursaria, was taken into glass cell, then the sample was darkened for 5 minutes The photosynthetic activity of Param ecium bursaria endosym biotic algae in varying tem perature conditions Fig. 2. Chlorophyll a �uorescence parameters of Paramecium bursaria strains: KD64 and Ard7, incubated at di�erent temperatures; di�erent letters di�er signi�cantly according to the Duncan test at p ≤ 0.05; n = 5 S yl w ia Ś liw iń sk a- W ilc ze w sk a, A ga ta C ie sz yń sk a, A da m L at ał a 72 to make the conditions needed to expire the light phase of photosynthesis. �e ob- tained results were analysed as follows: F0 – chlorophyll �uorescence intensity meas- ured when all photosystem II reaction centres are open, Fm – maximal chlorophyll �uorescence intensity measured when all photosystem II reaction centres are closed, Fv – variable chlorophyll �uorescence (Fm/F0), Fv/F0 – e�ciency of the water-splitting complex on the donor side of PSII and Fv/Fm – maximum quantum yield of PSII. In addition, Tfm – time needed for reaching Fm (ms), RC/ABS – index expression as the density of reaction centres (RC), PI – indicator of the functioning of PSII, TRo/RC – trapped energy �ux per cross section (RC) at t = 0, ETo/RC – electron transport �ux per cross section (RC) at t = 0, and Vj – relative change in chlorophyll �uorescence during the light phase of photosynthesis. Emission �uorescence – spectro�uorimetry method Measurement of blue-green and red �uorescence emission spectra were performed according to Lichtenthaler et al. (2004) with a spectro�uorimeter (Perkin-Elmer LS55B, United Kingdom) equipped with a liquid measuring device. Measurements of �uorescence intensity in the range of blue-green light (430–650 nm) were performed at 390 nm and near and far red (650–800 nm) with blue 430 nm. �e slot for the ex- citation radius was 15 nm, and for the emitted 20 nm. Results were analysed using FL WinLab version No. 3.00. Statistic analysis A parametric multi-factorial ANOVA / MANOVA test was used to compare the vari- ables tested, based on multiple Duncan homogeneous tests at p ≤ 0.05; n = 5. Calcula- tions were made using StatSo�, Inc. (2014). STATISTICA®12. Program. Results �e minimum (F0) and maximum (Fm) �uorescence values for both strains increased with temperature. �e highest F0 values were observed at 30°C. Parameters of max- imum PSII (Fv/Fm) photochemical e�ciency and maximum splash water yield a�er PSII donor side (Fv/F0) were highest at 18°C and lowest at 30°C for two Paramecium bursaria strains (Fig. 2). �e chlorophyll a �uorescence values were considerably di�erent at tested tem- peratures compared to the control group. �e chlorophyll �uorescence parameters (F0 and Fm) were signi�cantly higher for the KD64 strain compared to the Ard7 strain (Fig. 2–3). �e blue-green and red �uorescence emission spectra in KD64 and Ard7 strains were similar in the shape (Fig. 4). �e increase of blue-green emission �uorescence 73 The photosynthetic activity of Param ecium bursaria endosym biotic algae in varying tem perature conditions Fi g. 3 . C hl or op hy ll a �u or es ce nc e pa ra m et er s [ sh ow n as % o f c on tr ol ] o f P ar am ec iu m b ur sa ri a st ra in s i nc ub at ed a t d i� er en t t em pe ra tu re s S yl w ia Ś liw iń sk a- W ilc ze w sk a, A ga ta C ie sz yń sk a, A da m L at ał a 74 Fi g. 4 . � e bl ue -g re en (A ) a nd r ed (B ) � uo re sc en ce e m is si on s pe ct ra K D 64 a nd A rd 7 st ra in s of P ar am ec iu m b ur sa ri a in cu ba te d at d i� er en t t em - pe ra tu re s 75 was clearly shown at two wavelengths. �e �rst peak was observed at a wavelength 450–460 nm, and the second peak was at 485–490 nm. �e blue-green �uorescence emissions at 21°C were similar to the control group. �e �uorescence emission in- creased with temperature. Red �uorescence emission spectra for both strains of P. bursaria were character- ised by a distinct peak at a wavelength 675–685 nm with an arm at 750 nm. Fluores- cence intensity increased at temperatures 24°C to 30°C. �e values of F450/F685, F450/F735, F485/F685, and F485/F735 for P. bursaria strains decreased with increasing temperature. �e parameter F450/F530 increased with temperature, and the highest value was observed at 30°C (Tab. 1). Tab. 1. Fluorescence emission factors values of Ard7 – (A) and KD64 – (B) strains incubated at di�erent temperatures. Values shown as di�erent letters within the line di�er signi�cantly according to the Dun- can test at p ≤ 0.05; n = 5 Ratio Temperature [°C] 18 21 24 27 30 A B A B A B A B A B F450/F685 65.5a 49.1b 48.5b 45.9bc 40.9bcd 42.7bcd 36.90cd 44.2bcd 26.9e 35.2d F450/F735 652.7a 341.9ab 392.0ab 339.5ab 373.3ab 299.2ab 298.5ab 292.9ab 278.1b 262.6b F450/F530 1.43c 1.10g 1.46bc 1.27f 1.47b 1.27f 1.47b 1.30e 1.72a 1.40d F485/F685 72.3a 52.9bc 52.6bc 56.1b 44.6cd 49.3bcd 44.0cd 48.3bcd 29.2e 40.2d F485/F735 724.2a 394.0ab 466.3ab 391.6ab 407.6ab 341.1ab 323.5ab 320.6ab 301.0b 300.2b F685/F735 6.1a 5.4a 9.2a 6.6a 9.8a 8.0a 10.5a 7.4a 10.6a 8.5a Discussion Temperature has a major structuring e�ect at all levels of biological organisation. At the cell level, the temperature a�ects both energetic requirements and division rates, growth rate, and the decomposition and exchange of carbon dioxide and oxygen. �e functioning of the whole ecosystems depends on temperature (Brown et al., 2004; Savage et al., 2004). Green algae tolerance is not the same for constant and variable temperature treat- ments (Feder, Hofmann, 1999). Ciliates respond promptly and di�erently to environ- mental change (Jiang, Morin, 2004; Esteban, Finlay, 2007). In the present study, there was revealed a signi�cant e�ect of temperature on the photosynthetic activity of en- dosymbionts inside the Paramecium bursaria cells, which originated from a warm and cold climate. One-week incubation of ciliates at di�erent temperatures caused changes in chlorophyll a �uorescence parameters (Fig. 2–3), and an increase of �uorescence The photosynthetic activity of Param ecium bursaria endosym biotic algae in varying tem perature conditions S yl w ia Ś liw iń sk a- W ilc ze w sk a, A ga ta C ie sz yń sk a, A da m L at ał a 76 emission intensity (Fig. 4). �e values of emission �uorescence ratios (F450/F530 and F685/F730) were increased with temperature (Tab. 1). �ese changes may indicate a decrease in the e�ciency of primary reactions occurring in PSII and the activation of defence mechanisms of endosymbiont photosynthetic apparatus (Lichtenthaler, Rin- derle, 1988; Chemeris et al., 2004). At high temperatures, cell membrane permeability and damage of PSII subunits increase (Kota et al., 2002). �e changes are observed (I) in the structure of proteins and lipids, (II) in the functioning of ion channels, (III) disturbances in electron transport and in the reduction of electron acceptors, (IV) in the e�ciency of oxygen extraction, and (V) the dissipation of heat (Weng, Lai, 2005). High temperatures cause a blockade of energy transfer from the reaction centre to plastochinone (Reigosa, Weiss, 2001). Changes in F450/F530 values indicate an in- crease in phenolic compounds, and changes in F685/F730 values indicate a decrease in chlorophyll content (Lang et al., 1991; Lichtenthaler et al., 2004). �e rate of P. bursaria metabolism depends on the number of endosymbiotic Chlo- rella cells and their photosynthetic activity (Weis, 1969). �e photosynthetic products of symbiotic green algae increase the tolerance to high temperatures of the host cell (Iwatsuki et al., 1998). P. bursaria cells with Chlorella algae are more tolerant to high temperatures than algae-free ciliates (Miwa, 2009). �e studies on the e�ect of temperature on the morphology and physiology of al- gae show that the optimal growth temperatures for Chlorella vulgaris range from 26°C to 34°C (Mayo, 1997; Ma et al., 2014). Duncan et al. (2011) showed that Paramecium from variable environments grow well at both 23°C and 35°C. At temperatures from 29°C to 39°C, Chlorella sp. strain R-06/2 originating from geothermal source in Rupite (Bulgaria) is highly photosynthetically e�cient (Gacheva, Pilarski, 2008). Under nat- ural lighting conditions, the highest increase in chlorophyll content, carotenoids and proteins in C. vulgaris are observed at temperatures from 25°C to 30°C. Under contin- uous light conditions and at temperatures from 30°C to 35°C, algae growth is minimal (Sharma et al., 2012). Changes in physiological properties are due to the endosymbi- otic close relationship between paramecium and algae (Reisser, 1986). According to McAuley et al. (1996), the host regulates the growth of symbiotic algae. In the present study, the higher di�erences in photosynthetic activity were observed in the KD64 strain from Kamchatka (Fig. 2–4; Tab. 1). �e environmental stressors may cause many adverse changes in aquatic ecosys- tems, as well as for the economy and human health. �at is why it attaches great im- portance to ensuring continuous monitoring of waters, so that changes can be noted and appropriate corrective or preventive measures taken in the natural environment. Given the signi�cant ecological role played by ciliates, it is important to understand how temperature a�ects the adaptation of organisms in their local environment. 77 Conclusion �e study showed a signi�cant e�ect of temperature on the activity of the photo- synthetic apparatus of the Paramecium bursaria green endosymbionts. With an in- crease of temperature, changes in PSII were observed. High temperature caused an increase of blue-green and red �uorescence emission of endosymbiotic algae. �e strain of P. bursaria from Kamchatka (KD64) was more sensitive than the strain from Admore (Ard7). References Albers, D., Wiessner, W. (1985). Nitrogen nutrition of endosymbiotic Chlorella spec. Endocytobiosis Cell Research, 1, 55–64. Brown, J.A., Nielsen, P.J. (1974). Transfer of photosynthetically produced carbohydrate from endosymbi- otic Chlorellae to Paramecium bursaria. �e Journal of Protozoology, 21, 569–570. Brown, J.H., Gillooly, J.F., Allen, A.P., Savage, V.M., West, G.B. (2004). Toward a metabolic theory of ecol- ogy. Ecology, 85, 1771–89. DOI: 10.1890/03-9000 Chemeris, Y.K., Korol’kov, N.S., Seifullina, N.K., Rubin, A.B. (2004). Changes in the contents of inactive complexes of photosystem II in Chlorella cells incubated in the light and darkness. Russian Journal of Plant Physiology, 51, 287–293. DOI: 10.1023/B:RUPP.0000028673.79956.a2 Duncan, A.B., Fellous, S., Quillery, E., Kaltz, O. (2011). Adaptation of Paramecium caudatum to vari- able conditions of temperature stress. Research in Microbiology, 162, 939–944. DOI: 10.1016/j.re- smic.2011.04.012 Esteban, G.F., Finlay, B.J. (2007). Exceptional species richness of ciliated Protozoa in pristine intertidal rock pools. Marine Ecology Progress Series, 335, 133–141. DOI: 10.3354/meps3351338 Feder, M.E., Hofmann, G.E. (1999). Heat-shock proteins, molecular chaperones, and the stress response: evolutionary and ecological physiology. Annual Review of Physiology, 61, 243–282. DOI: 10.1146/ annurev.physiol.61.1.243 Gacheva, G., Pilarski, P. (2008). �e resistance of a new strain Chlorella sp. R-06/2, isolated from an ex- treme habitat to environmental stress factors. General and Applied Plant Physiology, 34(3–4), 347–360. Iwatsuki, K., Nishidoi, M., Suehiro, K. (1998). Symbiotic Chlorella enhances the thermal tolerance in Paramecium bursaria. Comparative Biochemistry and Physiology – Part A: Molecular & Integrative Physiology, 121, 405–409. DOI: 10.1016/S1095-6433(98)10151-4 Jessup, C.M., Kassen, R., Forde, S.E., Kerr, B., Buckling, A., Rainey., P.B., Bohannan, B.J. (2004). Big ques- tions, small worlds: microbial model systems in ecology. Trends in Ecology & Evolution, 19, 189–197. DOI: 10.1016/j.tree.2004.01.008 Jiang, L., Morin, P.J. (2004). Temperature-dependent interactions explain unexpected responses to envi- ronmental warming in communities of competitors. Journal of Animal Ecology, 73, 569–576. DOI: 10.1111/j.0021-8790.2004.00830.x Karakashian, S.J., Karakashian , M.W., Rudzińska, M.A. (1968). Electron microscopic observations on the symbiosis of Paramecium bursaria and its intracellular algae. Journal of Eukaryotic Microbiology, 15, 113–118. DOI: 10.1111/j.1550-7408.1968.tb02095.x Kodama, Y., Fujishima, M. (2005). Symbiotic Chlorella sp. of the ciliate Paramecium bursaria do not pre- vent acidi�cation and lysosomal fusion of host digestive vacuoles during infection. Protoplasma, 225, 191–203. DOI: 10.1007/s00709-005-0087-5 The photosynthetic activity of Param ecium bursaria endosym biotic algae in varying tem perature conditions S yl w ia Ś liw iń sk a- W ilc ze w sk a, A ga ta C ie sz yń sk a, A da m L at ał a 78 Kota, Z., Horvath, L.I., Droppa, M., Horvath G., Farkas, T., Pali, T. (2002). Protein assembly and heat stability in developing thylakoid membranes during greening. Proceedings of the National Academy of Sciences, 99, 12149–12154. DOI: 10.1073/pnas.192463899 Lang, M., Stober, F., Lichtenthaler, H.K. (1991). Fluorescence emission spectra of plant leaves and plant constituents. Radiation and Environmental Biophysics, 30, 333–347. DOI: 10.1007/BF01210517 Lichtenthaler, H.K., Knapp, M., Buschmann, C. (2004). Recording chlorophyll �uorescence emission spectra with the Perkin Elmer �uorescence spectrometer LS 50. In: M. Filek, J. Biesaga-Kościelniak, I. Marcińska (eds.), Analytical methods in plant stress biology. Kraków: Drukrol, 112–124. Lichtenthaler, H.K., Rinderle, U. (1988). �e role of chlorophyll �uorescence in the detection of stress conditions in plants. Critical Reviews in Analytical Chemistry, 19, S29–S85. Ma, X., Zheng, H., Huang, H., Liu, Y., Ruan, R. (2014). E�ects of temperature and substrate concentration on lipid production by Chlorella vulgaris from enzymatic hydrolysates of lipid-extracted microal- gal biomass residues (LMBRs). Applied Biochemistry and Biotechnology, 174(4), 1631–1650. DOI: 10.1007/s12010-014-1134-5 Mayo, A.W. (1997). E�ects of temperature and pH on the kinetic growth of unialga Chlorella vulgaris cultures containing bacteria. Water Environment Research, 69(1), 64–72. DOI: 10.2175/106143097X125191 McAuley, J.P., Dorling, M., Hodge, H. (1996). E�ect of maltose release on uptake and assimilation of ammonium by symbiotic Chlorella (Chlorophyta). Journal of Phycology, 32, 839–846. DOI: 10.1111/j.0022-3646.1996.00839.x Miwa, I. (2009). Regulation of circadian rhythms of Paramecium bursaria by symbiotic Chlorella species. In: M. Fujishima (ed.) Endosymbionts in Paramecium. Microbiology Monographs, 12, 83–110. Morgan-Kiss, R., Ivanov, A.G., Williams, J., Khan, M., Huner, N.P.A. (2002). Di�erential thermal e�ects on the energy distribution between photosystem II and photosystem I in thylakoid membranes of a psychrophilic and a mesophilic alga. Biochimica et Biophysica Acta (BBA)-Biomembranes, 1561(2), 251–265. DOI: 10.1016/S0005-2736(02)00352-8 Reigosa, R.M.J., Weiss, O. (2001). Fluorescence techniiques. In: R.M. Reigosa (ed.) Handbook of plant ecophysiology techniques. Dordrecht: �e Netherlands Kluwer Academic Publishers, 155–171. Reisser, W. (1980). �e metabolic interactions between Paramecium bursaria and Chlorella spec. in the Paramecium bursaria-symbiosis. Archives of Microbiology, 125, 291–293. DOI: 10.1007/BF00446890 Reisser, W. (1986). Endosymbiotic associations of freshwater protozoa and algae. Program Protistol- gy, 1, 195–214. Savage, V.M., Gillooly, J.F., Brown, J.H., West, G.B., Charnov, E.L. (2004). E�ects of body size and temper- ature on population growth. American Naturalist, 163, 429–441. DOI: 10.1086/381872 Sharma, R., Singh, G.P., Sharma, V.K. (2012). E�ects of culture conditions on growth and biochemical pro- �le of Chlorella vulgaris. Journal of Plant Pathology and Microbiology, 3(5), 1–6. DOI: 10.4172/2157- 7471.1000131 Sommaruga, R., Sonntag, B. (2009). Photobiological aspects of the mutualistic association between Para- mecium bursaria and Chlorella. In: M. Fujishima (ed.), Endosymbionts in Paramecium. Microbiology Monographs, 12, 111–130. DOI: 10.1007/978-3-540-92677-1_5 Sonneborn, T.M. (1970). Methods in Paramecium research. In: E.D.M Prescott (ed.), Methods in cell biol- ogy. New York: Academy Press, 241–339. Strasser, R.J., Strvastava, A., Govindjee (1995). Polyphasic chlorophyll a �uorescence transient in plants and cyanobacteria. Photochemistry and Photobiology, 61, 32–34. DOI: 10.1111/j.1751-1097.1995. tb09240.x Weis, D.S. (1969). Regulation of host and symbiont population size in Paramecium bursaria. Experientia, 25(6), 664–6. 79 Weng, J.H., Lai, M.F. (2005). Estimating heat tolerance among plant species by two chlorophyll �uores- cence parameters. Photosynthetica, 43, 439–444. DOI: 10.1007/s11099-005-0070-6 Wilson, K.E., Huner, N.P. (2000).�e role of growth rate, redox-state of the plastoquinone pool and the trans-thylakoid deltapH in photoacclimation of Chlorella vulgaris to growth irradiance and temper- ature. Planta, 212(1), 93–102. DOI: 10.1007/s004250000368 Abstract �e aim of this study was to investigate the e�ect of higher temperatures on the photosynthesis of endo- symbiotic Chlorella sp. of two Paramecium bursaria Ehrenberg 1831 strains originating from regions with a warmer and colder climate (Ardmore – USA and Kamchatka – Russia, respectively). A�er seven days of protozoa incubation at 18°C (control), 21°C, 24°C, 27°C, 30°C and 33°C, the chlorophyll a �uorescence measurements were carried out and �uorescence spectra were measured in blue-green and red light. As a result of the studies, a signi�cant e�ect of higher temperature on the photosynthesis process of P. bursaria endosymbionts was observed. Weekly incubation at 33°C was lethal for both protozoan strains in compar- ison to the control temperature (18°C). �e blue-green �uorescence spectra were characterised by marked peaks at 450 nm and 490 nm. Within the red light range, the peak was observed at about 690 nm with a lesser arm at 730 nm. Endosymbionts from Kamchatka were more sensitive to the temperature increase than algae from areas with relatively warm climates. Key words: emission �uorescence, high temperatures, PSII activity, spectro�uorimetry, Chlorella vulgaris Received: [2017.08.13] Accepted: [2017.11.14] Aktywność fotosyntetyczna endosymbiotycznych glonów Paramecium bursaria w zróżnicowanych warunkach temperatury Streszczenie Celem niniejszej pracy było zbadanie wpływu podwyższonej temperatury na przebieg procesu fotosyntezy endosymbiontów z gatunku Chlorella sp. dwóch szczepów Paramecium bursaria Ehrenberg 1831, pocho- dzących z terenów o niskich i wysokich temperaturach powietrza (Ardmore – USA i Kamczatka – Rosja). Po 7 dniach inkubacji pierwotniaków w każdej z temperatur 18°C (kontola), 21°C, 24°C, 27°C, 30°C i 33°C przeprowadzono pomiary �uorescencji chloro�lu a  i  wyznaczono widma emisji �uorescencji w  zakresie niebiesko-zielonym i czerwonym.W wyniku przeprowadzonych badań zaobserwowano istotny wpływ pod- wyższonej temperatury na proces fotosyntezy endosymbiontów P. bursaria. Tygodniowa inkubacja w tem- peraturze 33°C była letalna dla obu szczepów pierwotniaka, w porównaniu z temperaturą kontrolną (18°C). Widma emisji �uorescencji niebiesko-zielonej charakteryzowały wyraźnymi pikami przy 450nm i 490 nm. W  zakresie czerwonym pik zaobserwowano przy około 690 nm z  mało wyraźnym ramieniem przy 730 nm. Endosymbionty szczepu pochodzącego z Kamczatki były bardziej wrażliwe na wzrost temperatury od glonów pochodzących z terenów o stosunkowo ciepłym klimacie. Słowa kluczowe: wysoka temperatura, aktywność PSII, spektro�uorymetria, szczepy Chlorella vulgaris Information on the authors Katarzyna Możdżeń Her scienti�c interests concentrate on the e�ects of di�erent environmental factors (light, ozone, heavy metals, allelopathic extracts) on the morphology and physiology plants cultivated, protected, and inva- sive species. Patrycja Zagata Leśnicka She is graduate of Doctoral Studies at the Institute of Biology at the Pedagogical University in Kraków. Her scienti�c interests concern microbiology and algology, and especially the endosymbionts of Parame- cium bursaria. The photosynthetic activity of Param ecium bursaria endosym biotic algae in varying tem perature conditions S yl w ia Ś liw iń sk a- W ilc ze w sk a, A ga ta C ie sz yń sk a, A da m L at ał a 80 Mateusz Ślęczka He graduated from the Environmental Protection at the Pedagogical University in Kraków. His scienti�c interests concern environmental microbiology. Magdalena Greczek-Stachura She is associate professor at the Pedagogical University in Cracow. Her interest is in the broadly unders- tood microbiology and algology. In recent years, her research has focused on endosymbiosis in a group of Ciliata (animal Protista).