Plant Physiol. (1979) 63, 524-5300032-0889/79/63/0524/07/$00.50/0

Effect of Growth Temperature on the Lipid and Fatty AcidComposition, and the Dependence on Temperature of Light-induced Redox Reactions of Cytochrome f and of Light EnergyRedistribution in the Thermophilic Blue-Green AlgaSynechococcus lividus'

Received for publication June 13, 1978 and in revised form November 1, 1978

DAVID C. FORK2Carnegie Institution of Washington, Department of Plant Biology, 290 Panama Street, Stanford, California94305

NORIO MURATA AND NAOKI SATODepartment of Biology, College of General Education, University of Tokyo, Komaba, Meguro-ku, Tokyo 153,Japan

ABSTRACT

The thernphic blue-green alga Synechococcus fividus was grown at55 and 38 C. Arrhenius plots of the transient reduction of cytochromeduring actinic illumination with light that excited both pigment systemsrevealed breaks near 43 and 26 C for cells grown at 55 C. In cells grownat 38 C these breaks occurred near 37 and 28 C, respectively. The shiftfrom pigment state 1 to state 2 measured by fluorescence transients alsoshowed characteristic breaks in the Arrhenius plots at 44 C for cells grownat 55 C and at 37 to 38 C and possibly at 25 C for cells grown at 38 C. Thebreak points in the Arrhenius plots for the state shift as well as for thecytochrome f reduction are discussed in relation to phase transitions ofthylakoid membrane lipids as studied by the temperature dependence ofchlopbyll a fluorescence.The variations of fatty acid composition with growth temperature was

also studied. When the growth temperature was lowered from 55 to 38 C,the amount of the saturated fatty acid 18:0 in the negatively charged lipidssulfoquinovosyl diglyceride and phosphatidyl glycerol decreased while theunsaturated fatty acids 18:1 and 16:1 increased. In mono- and digalactosyldiglycerides the saturated fatty acids 18:0 and 16:0 decreased and theunsaturated fatty acid 16:1 increased. In general there was an increase inthe more fluid lipids in all of the lipid classes when the cells were grown atthe lower temperature.

number of membrane-bound enzymes have been found to havebreaks and/or changes of slope at the temperature of phasetransition (15, 16, 26, 30).

In order to investigate the relationship between the physicalstate of thylakoid membrane lipids and photosynthetic activity wehave measured the temperatures of phase transitions and thetemperature dependencies of a number of physiological activitiesthat are related to the photosynthetic process (8, 9, 19-22, 24, 25).The extreme thermophile Synechococcus lividus used in this

study grows in alkaline hot springs and has been reported to growphotosynthetically at temperatures as high as 73 to 75 C (3, 4, 12).Although capable of growing at such extreme temperatures, thisalga can be adapted to grow at much lower temperatures.

Preliminary measurements using Chl a fluorescence indicatedthat S. lividus grown in the temperature range from 55 to 65 Cexhibited phase transitions of the thylakoid membrane lipidsaround 42 to 44 C and that electron transport measured as therate of Cytf reduction in cells grown at 55 C showed a disconti-nuity in the Arrhenius plot near these same temperatures (8).We grew the same strain of S. lividus at 55 and 38 C, analyzed

the lipid composition of the cells, and measured the temperaturedependence of Chl a fluorescence as well as the oxidation-reduc-tion reactions of Cytfand the state 1 to state 2 shift. It was foundthat the growth temperature influenced these parameters as in theblue-green alga Anacystis nidulans (22, 25).

Studies in a number of laboratories are directed at understand-ing the physical basis for temperature effects at the membranelevel. A current model for biological membranes (29) proposes alipid bilayer in which are embedded enzyme proteins and othersubstances involved in the bioenergetic process. The behavior ofsome temperature-dependent processes has been interpreted asbeing produced by changes in the physical state of the membranelipids. The straight lines in the Arrhenius plots of activities for a

l Carnegie Institution of Washington-Department of Plant Biology Pub-lication No. 627.

2To whom reprint requests should be sent.

MATERIALS AND METHODS

S. lividus (strain SY4) was obtained through the courtesy ofMercedes Edwards of the Division of Laboratories and Researchof the State of New York Department of Health who isolated itfrom thermal springs in Yellowstone Park, Wyoming. It wasgrown according to Castenholz in D-medium (4, 6, 28) at thedesired temperature with a gas phase of 0.5% C02/air in bubbletubes fitted with condensers to retard evaporation (5). The inten-sity of tungsten light used for growth was about 3,300 lux. Oneculture was grown at 55 C. A portion ofthis culture was transferredto a water bath illuminated with a combination of tungsten andwarm and cool-white fluorescent lamps (5,300 lux) and adaptedto grow at 38 C. The cells were used for the measurements after

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MEMBRANE LIPIDS AND PHOTOSYNTHESIS

growth at the respective temperatures for more than 1 week.Absorption spectra were measured with a Cary 17 spectropho-

tometer fitted with a scattered transmission accessory. Light-in-duced A changes of Cytfwere measured in a horizontally placedcuvette fitted with a stainless steel coil through which coolantcould be flowed to control temperature. The solution in the cuvettewas bubbled with gas (usually 5% C02/air) to keep the sampleaerobic during the spectroscopic measurements. A copper-con-stantan thermocouple provided a voltage that was used to deter-mine the temperature. This signal as well as the signals from thephotomultiplier (EMI 9558B) that was used to follow A changesand the signal from a photocell that followed actinic light changeswere all supplied to the analog-to-digital converter of a HewlettPackard 2116 computer. Analysis of the data provided measure-ments of rates, temperature, light intensity, and on-off times. Thetemperature was decreased or increased usually at a rate of aboutI C/min.A broad band of red light with wavelengths from 620 to 750 nm

having an intensity of about 1.8 x 105 ergs cm-2 s-' that excitedboth PSI and PSII was obtained by passing white light through 37mm ofwater, a heat-reflecting filter (Calflex C), and a 3-mm-thickred cut-off glass filter (Schott RG2). The half-bandwidth of themeasuring beam used for A change measurements was 2 nm.The pigment state 1 to state 2 shift was measured in an open,

stirred cuvette that could be gassed with 5% C02/air to providefavorable physiological conditions. For these measurements thecell suspension was illuminated continuously with 600 nm light(5.4 x 103 ergs cMn2 s-1) to excite mainly PSII. Chl a fluorescenceat 685 nm was monitored continuously by a photomultiplierplaced above the sample. The cells were in state 2 in this light. Abeam of blue light with maximum at 430 nm having an intensityof 18 x 103 ergs cm 2 s-1 and defined by Calflex C and Corningglass filters CS4-96 and CS5-60 was superimposed on the 600 nmlight for a period of 3 min and then turned off for 3 min (the 600nm beam remaining on). These cycles were repeated during whichtime the state shifts as revealed by fluorescence changes wererecorded on a strip chart recorded (Varian GIOOO).The temperature dependence of Chl a fluorescence was meas-

403

0.5 Grown at 550C

0 0 0

4 ~~~~~~~~~554

ured as previously described (9). Chl fluorescence at 685 nm wasexcited with a band of blue light having a wavelength maximumat 435 nm and an intensity of 460 ergs cm-2 s-, or with yellow-orange light at 560 rn (620 ergs cm-2 s-1) or 600 nm (350 ergscm-2 s-'). In each of these measurements DCMU was added to afinal concentration of 0.1 mm.For analysis of lipids, the cells were collected by centrifugation

at 10,000g for 5 min and then stored in liquid N2. Lipids wereextracted from the cells with a mixture of chloroform and meth-anol (2:1, v/v) according to the methods of Folch et al. (7). Thecrude lipid extract was fractionated by TLC on silica gel (WAKOGEL B-10). The solvent used for chromatography was a mixtureof chloroform, methanol, ammonium hydroxide, and 2-propyla-mine (130:70:10:1, by volume) according to Allen and Good (1).Lipids were identified by RF values on the thin layer plates (1).Lipid zones were collected and the lipids were extracted with amixture of chloroform and methanol (2:1, v/v). The extracts werewashed with water (7), and concentrated under reduced pressure.The lipids were methanolyzed in 3% HCl-containing methanol at90 C for 2 h, and fatty acid methylesters were analyzed by gaschromatography using a Shimadzu GC-4BM. Detailed methodsfor the lipid and fatty acid analyses were described elsewhere (27).

RESULTS AND DISCUSSION

Microsopic examination of cultures grown at the two differenttemperatures revealed both consisted of rod-shaped cells about 7um long and 1.5 ,m wide. Cells grown at 38 C and at the lightintensity used were yellow-green, compared to the usual blue-green color seen when the cells were grown at 55 C. This colorchange was apparently caused by an increase of carotenoids anda decrease of phycobilins as indicated by the enhanced A at 430,452, and 480 am and reduced A at 616 am of cells grown at 38 C(data not shown).

Figure 1 shows the light-minus dark difference spectrum meas-ured at 25, 31 and 38 C for cells grown at 38 C. These spectra arealmost identical at the three temperatures and represent an almostpure oxidized-minus-reduced spectrum for Cyt f with negative

Wavelength, nmFIG. 1. Light minus dark difference spectra measured at 50, 35, and 20 C for S. lividus grown at 55 C and measured at 38, 31, and 25 C for cells

grown at 38 C. The A difference was measured between the A change level attained after 15-s of actinic illumination and the level in the dark I s afterturning off the actinic light.

Plant Physiol. Vol. 63, 1979 525

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FORK, MURATA, AND SATO Plant Physiol. Vol. 63, 1979

peaks at 419 and 554 nm and a positive peak near 403 nm. Analmost identical light-induced difference spectrum was obtainedat 20, 35, and 50 C using cells grown at 55 C. In this case, a distinctshoulder, probably produced by the light-induced oxidation ofP700, was seen near 433 nm.As observed previously (8), the kinetics of the Cytfchange near

420 nm are complex. Upon illumination with high intensity redlight that excited both photosystems, there was an initial, rapidphotooxidation of Cyt followed by a partial reduction and finallyby a further slow oxidation until a steady-state level of oxidationwas attained in the light. Upon darkening the cells a rapid Cytreduction took place. PSII was responsible for the transient re-duction of Cyt in the light since it was eliminated by DCMU andwas not seen in far red light that excited only PSI.We measured the transient reduction of Cyt f in the light by

determining the reciprocal of the quarter decay time and plottedit as a function of the reciprocal of absolute temperature. Figure2 shows the Arrhenius plot for the rate of Cytf reduction over atemperature range from 52 to 18 C for cells grown at 55 C. Breaksof straight lines can be seen near 43 and 26 C. The activationenergy was 7.2 kcal mol' above 43 C; 13.9 kcal mol' between 43and 26 C; and 24.3 kcal mol' below 26 C. The same experimentwas done with cells grown at 38 C (Fig. 3). Breaks in the Arrheniusplot were seen near 37 and 27 C (decreasing the temperature). Theactivation energy was 8.1 kcal mol-1 above 37 C, 21.3 kcal mol-1between 37 and 27 C, and 37.3 kcal mol' below 27 C. After thetemperature had decreased to about 22 C the sample of cellsgrown at 38 C was heated and measurements continued. The rightside of Figure 3 illustrates the reversibility of the results. TheArrhenius plot showed breaks occurring at about the same tem-peratures as before. However, the activation energies were lowerparticularly above the 38 C point. Although not shown in Figure2, a similar reversibility was noted for the 55 C cells. The revers-ibility of the break points and the changed activation energiesafter the cells had been cooled and reheated were noted previously(8).The temperature dependence of the pigment state 1 to state 2

shift (2, 17, 18) was also studied. For this experiment the algalcells were exposed to 600 nm light that was absorbed mainly byPSII. During this period an alteration of the thylakoid membranetook place such that some of the quanta absorbed by PSII were

transferred to PSI (18). This flexibility of quantum distributionhelps somewhat to overcome the rate-limiting step(s) caused byproviding illumination that initially produced unbalanced excita-tion of the two photosystems. When the cells were illuminatedwith strong blue light absorbed preferentially by PSI the reversechange of quantum distribution occurred.The inset ofFigure 4 shows the fluorescence transients measured

Temperature, 0C

T

0)

E> 100au0)

L-

o

I-a

0 -30au00.

0)a::

50

3.1

40 30 20

3.2 3.3 3.4

I/T x 103 OK-'FIG. 2. Arrhenius plot of transient reduction of Cytfmeasured at 420

nm during a period of red actinic illumination in S. lividus grown at 55 C.Time for the transient seen immediately after onset of illumination todecay to one-quarter of its initial value was taken as the relative rate ofelectron transfer from PSII to Cytf (see Fig. 11 in Ref. 8). Arrow showsdirection of temperature change. Values in parentheses are activationenergies in kcal mol-1.

40 30

3.2 3.3

Temperature, °C20,,50

3.4 "3.1

I/T x 103 OK-'FIG. 3. Arrhenius plot of transient reduction of Cytf measured as described in Figure 2 for S. lividus grown at 38 C. Arrows indicate direction of

temperature change. Temperature of the cells was first decreased then increased. Values in parentheses are activation energies in kcal mol-'.

526

(7.2)

(13.9)

Grown at 550CI -

(24.3) O%

II I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

50

100

u0)

E

au0)

I-0)

a

.4_0

LI

au:

301-

(8.)

0

Grown at 38°C(21.3)

2801l,

(36.8)

(37.3)

I

40

3.2

30

3.3

20

3.4lol

3.1

430XL

019.1)

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MEMBRANE LIPIDS AND PHOTOSYNTHESIS

at 53 C for cells grown at 55 C. The cells were exposed to acontinuous beam of 600 nm light to excite mainly PSII. Blue lightabsorbed by PSI was then superimposed on the 600 nm light forseveral min. Under this strong blue light the oxidized forms ofelectron transport carriers accumulated. This is reflected by thelow level (I) of fluorescence yield after the blue light was turnedoff. Reduction of these oxidized intermediates by the 600 nmbackground excitation light gave rise to the rapid increase influorescence yield from I to P. The slow fluorescence declineduring continued exposure to 600 nm light (P to S) reflects thepigment state 1 to state 2 shift. In order to measure this shiftquantitatively we measured the initial rate of the P to S decline

C

c-Z

01x

a-

6)a

I')6)

a(I)

50 40

527

and divided it by the extent of the fluorescence yield change (AFin the inset) (22).The pigment state 1 to state 2 shift of light quantum distribution

between the two photosystems was very strongly affected by thetemperature. Figure 4 shows the Arrhenius plot of this measure ofthe rate of the state 1 to state 2 shift for cells grown at 55 C. Thisplot shows a clear break near 44 C. Below this temperature thestate changes declined sharply. Below 33 C the changes were sosmall and slow as to be unmeasurable.

Figure 5 shows the same experiment done for cells grown at 38C. Here the Arrhenius plot showed a break at 37 C upon decreas-ing the temperature. Another break may have occurred near 25 C

Temperature, °C

30 20 10

3.1 3.2 3.3 3.4 3.5 3.6

I/T x 103 OK-'FIG. 4. Arrhenius plot of shift of state I to state 2 in S. lividus grown at 55 C. Inset: time course of fluorescence transients caused by state 1 to state

2 shift measured at 53 C as described in text. Arrows indicate direction of temperature change.

Temperature, 0C

c

E

x

-Z-a

(-

tn

a

(J)

3

1.0

0.3

40

3.2

30 40

3.3 3.2

I/T x 103 OK-'

30

3.3 3.4

FIG. 5. Arrhenius plot of the shift of state I to state 2 in S. lividus grown at 38 C. Temperature was first decreased then immediately increased asindicated by arrows.

Plant Physiol. Vol. 63, 1979

0(44)K<\b440

State State State2 2--1 1--2

3 Measured at 53 C

p

(31.6) T

.0 Grownaof55C* .On Off 20%Sysftem ,-1 min--II light

f I // I

Grown at 38°C

9) 370 0 0 3

~ 8J7)250156)

\ oX ~~~~~250

1 //

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FORK, MURATA, AND SATO

but this conclusion rests on only one point taken at a temperaturewhere the fluorescence yield changes were very slow and small.Increasing the temperature in the same sample again producedthe possible break at 25 C and a break at 38 C. These results forthe state 1 to state 2 shift and those discussed earlier for the Cytredox change reaction suggest that there are two characteristicpoints in the temperature dependence of these reactions.Measurements of the temperature dependence of Chl a fluores-

cence in A. nidulans showed that a maximum appeared near thetemperature where a transition of the physical phase of themembrane lipids occurred (19, 22). These types of measurementswere done for S. lividus grown at 38 and 55 C (Fig. 6). All of thecurves were measured m the presence of DCMU to preventelectron transport reactions from producing fluorescence yieldchanges. Chl a fluorescence was excited directly by using blueactinic light (435 nm), or indirectly via phycocyanin excitationusing orange actinic light (560 nm). The excitation intensities werekept low (several hundred ergs cm-' s-1) to prevent temperature-dependent pigment state changes such as those described in Fig-ures 4 and 5. (Low actinic light, 400 ergs cm-2 s-', was also usedpreviously [19-22] for the measurements with A. nidulans-, but theintensity used was erroneously reported (22) to be 10 times higher.)The curve of Chl a fluorescence versus temperature that was

produced using phycocyanin excitation (Fig. 6A) had a maximumnear 41 C on decreasing the temperature. Increasing the temper-ature produced a maximum around 43 C. The dependence of Chla fluorescence for cells grown at 55 C using direct Chl excitationshowed peaks at 40 and 42 C upon decreasing and increasing thetemperature respectively (Fig. 6B). These observations suggeststhat a transition of the phase of the thylakoid membrane lipidstakes place near this temperature and is associated with thecharacteristic break points seen at the higher temperature in theArrhenius plots for both the Ctyf reaction and the state 1 to state2 shift. No maxima were observed in the fluorescence versustemperature curve in the low temperature region (25 C) where thecharacteristic discontinuity points for the physiological activitieswere seen.

In the fluorescence versus temperature curve for cells grown at

6)u

101

0

38 C, a maximum (or shoulder) was seen around 25 C, wherecharacteristic break points at the low temperature region appearedin the Cytf reaction and the pigment state I to state 2 shift. Nomaxima or shoulders in the curve for the temperature dependenceof fluorescence were observed around 38 C where the othercharacteristic discontinuity points for the physiological activitiesappeared. This absence of maxima near 38 C remains to beexplained.

S. lividus, similar to other blue-green algae (10, 11, 23, 27),contains four major lipids: mono- and digalactosyl diglyceride,sulfoquinovosyl diglyceride, and phosphatidyl glycerol (Table I).Similar to A. nidulans (27), the cells of S. lividus do not containany polyunsaturated fatty acids but only saturated and monoun-saturated fatty acids. Other species of blue-green algae such asAnabaena variabilis (27) contain linoleic and linolenic acids. Per-haps this difference in fatty acid composition may partially explainthe thermophilic nature of S. lividus and A. nidulans.A comparison of the fatty acid composition of the separated

lipids of cells grown at 55 C and 38 C can be seen in Table I.Monounsaturated fatty acids 18:1 and 16:1 from the negativelycharged lipids sulfoquinovosyl diglyceride and phosphatidyl glyc-erol increased when the growth temperature was lowered from 55to 38 C while the saturated fatty acid 16:0 remained unchangedand 18:0 decreased. In the galactolipids mono- and digalactosyldiglyceride, and the saturated fatty acids 16:0 and 18:0 decreasedwhile the unsaturated fatty acid 16:1 increased and 18:1 remainedunchanged when the growth temperature was lowered from 55 to38 C.

In general, cells grown at the lower temperature had an increaseof the more fluid (unsaturated and short chained) fatty acids in allof the lipid classes. The ratio of unsaturated to saturated fattyacids in the total lipids was 0.31 for cells grown at 55 C andincreased over four times to 1.31 in cells grown at 38 C. The ratioof C16 to C18 fatty acids in the total lipids increased about twotimes when the growth temperature was lowered from 55 to 38 C.Similar changes with growth temperature in the ratios were ob-served in all of the four lipid classes. The change in fatty acidcomposition in this alga would seem to be related to the shift of

10 20 30 40 50 10 20 30 40

Temperature, 0C50

FIG. 6. Temperature dependence of Chl a fluorescence in S. lividus grown at 38 and 55 C. Chl a fluorescence was excited directly with blue light orindirectly via phycocyanin excitation (yellow-orange light) as described in text. Arrows indicate direction of temperature change.

I T IItIll

Phycocyanin excitationA. Grown ot 55°C 414 C. Grown t38

10%

140° Chlorophyll excitationB. Grown at 55 C

// \ D. Grown ct38°C

22 0 250

528 Plant Physiol. Vol. 63, 1979

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MEMBRANE LIPIDS AND PHOTOSYNTHESIS

Table I. FATTY ACID COMPOSITIONS IN LIPIDS OF Synechococcus Zividus GROWN AT 55 and 38 C.

GROWN AT 55 C

FATTY ACID Monogalactosyl Digalactosyl Sulfoquinovosyl Phosphatidyl TOTALdiglyceride diglyceride diglyceride glycerol LIPIDS

16:0 50.2 53.3 58.7 55.1 53.816:1 14.9 10.2 1.0 4.5 9.617:0 0.4 0.5 0.4 0.4 0.517.1 0.1 0.0 0.0 0.3 0.018:0 21.4 17.7 28.1 21.9 22.318:1 13.0 18.2 11.9 17.8 13.8

Unsaturated/ Saturated0.40 0.40 0.15 0.29 0.31

C16acids/C 8 acids 1.9 1.8 1.5 1.5 1.8

GROWN AT 38 C

16:0 36.4 35.6 59.2 52.6 42.416:1 47.3 43.1 10.8 20.2 35.917:0 0.2 0.2 0.2 0.4 0.417:1 0.5 0.6 0.3 0.4 0.518:0 0.5 0.9 0.4 1.8 0.518:1 15.2 19.7 29.2 24.6 20.3

Unsaturated/ Saturated1.70 1.73 0.67 0.82 1.31

C16 d acids 3.8 2.4 2.8 3.8

Fatty acid contents expressed as molar percent

temperature of the characteristic points in the temperature de-pendence of the Cytf reaction, the state 1 to state 2 shift, and theChi a fluorescence.As noted in the previous studies with Anacystis nidulans, Ana-

baena variabilis, and Cyanidium caldarium (9, 19, 21, 22) thetemperatures at which lipid phase transitions occurred dependedupon the growth temperature. These differences appear to becaused by growth temperature-dependent changes in the fatty acidcomposition of the membrane lipids. Lowering the growth tem-perature from 38 to 22 C produced an increase in the desaturationof fatty acids in A. variabilis and a decrease in the chain length offatty acids in A. nidulans (27). Similar trends were noted in C.caldarium where a 3-fold increase in the ratio of unsaturated tosaturated fatty acids was noted when the temperature was loweredfrom 55 to 20 C (13, 14).

LITERATURE CITED

1. ALLEN CF, P GOOD 1971 Acyl lipids in photosynthetic systems. Methods Enzymol 23: 523-5472. BONAVENTURA C, J MYERS 1969 Fluorescence and oxygen evolution from Chlorellapyrenoidosa

Biochim Biophys Acta 189: 366-3833. BROCK TD 1967 Micro-organisms adapted to high temperatures. Nature 214: 882-8854. CASTENHOLZ RW 1969 Thermophilic blue-green algae and the thermal environment. Bacteriol

Rev 33: 476-5045. CASTENHOLZ RW 1970 Laboratory culture of the thermophilic cyanophytes. Schweiz Z Hydrol

32: 538-5516. CASTENHOLZ RW 1972 Low temperature acclimation and survival in thermophilic Oscillaioria

terebriformis. In TV Desikachary, ed, Taxonomy and Biology of Blue-Green Algae. Univer-sity of Madras, India, pp 406-418

7. FOLCH J, M LESs, GH SLOANE-STANLEY 1957 A simple method for the isolation and purificationof total lipides from animal tissues. J Biol Chem 226: 497-509

8. FoRK DC, N MURATA 1977 Studies on the effect of transition of the physical phase ofmembrane lipids on electron transport in the extreme thermophile Synechococcus lividus.Camegie Inst Wash Year Book 76: 222-226

9. FoRtc DC, N MURATA 1977 The relationship between changes in the physical phase of

membrane lipids and photosynthesis in the thermophilic alga Cyanidium caldarium. SpecialIssue of Plant Cell Physiol 427-436

10. HIRAYAMA 0 1967 Lipids and lipoprotein complex in photosynthetic tissues. II. Pigments andlipids in blue-green alga Anacystis nidulans. J Biochem 61: 179-185

11. HOLTON RW, HH BLEcKER, M ONORE 1964 Effect of growth temperature on the fatty acidcomposition of a blue green alga. Phytochemistry 3: 595-602

12. KEMPNER ES 1963 Upper temperature limit of life. Science 142: 1318-131913. KLEINSCHMSDT MG, VA MCMAHON 1970 Effect of growth temperature on the lipid composi-

tion of Cyanidium caldarium I. Class separation of lipids. Plant Physiol 46: 286-28914. KLEINSCHMIDT MG, VA MCMAHON 1970 Effect of growth temperature on the lipid composi-

tion of Cyanidium caldarium II. Glycolipid and phospholipid components. Plant Physiol 46:290-293

15. LINDEN CD, KL WRIGtrr, HM McCoNmELu, CF Fox 1973 Lateral phase separation inmembrane lipids and the mechanism of sugar transport in Eschenchia coli Proc Nat AcadSci USA 70: 2271-2275

16. MABREY SG, JB Powis, TR TRITTON 1977 Calorimetric study of microsomal membrane. J.Biol Chem 252: 2929-2933

17. MURATA N 1969 Control of excitation transfer in photosynthesis. I. Light-induced change ofchlorophyll a fluorescence in Porphyridium crsentum. Biochim Biophys Acta 172: 242-251

18. MURATA N 1970 Control of excitation transfer in photosynthesis. IV. Kinetics of chlorophylla fluorescence in Porphyra yezoensis. Biochim Biophys Acta 205: 379-389

19. MURATA N, DC FoRK 1975 Temperature dependence of chlorophyll a fluorescence in relationto the physical phase of membrane lipids in algae and higher plants. Plant Physiol 56: 791-7%

20. MURATA N, DC FoRK 1977 Temperature dependence of chlorophyll a fluorescence in lettuceand spinach chloroplasts at sub-zero temperatures. Plant Cell Physiol 18: 1265-1271

21. MURATA N, DC FoRK 1977 Temperature dependence of the light-induced spectral shift ofcarotenoids in Cyanidium caldarium and higher plant leaves. Evidence for an effect of thephysical phase of chloroplast membrane lipids on the permeability of the membrane to ions.Biochim Biophys Acta 461: 365-378

22. MURATA N, JH TROUGHTON, DC FoRKC 1975 Relationships between the transition of thephysical phase of membrane lipids and photosynthetic parameters in Anacystis nidulans andlettuce and spinach chloroplasts. Plant Physiol 56: 508-517

23. NICHOLS BW, RV HARRIS, T JAMEs 1965 The lipid metabolism of blue-green algae. BiochemBiophys Res Commun 20 256-262

24. ONo T, N MURATA 1977 Temperature dependence of the delayed fluorescence of chlorophylla in blue-green algae. Biochim Biophys Acta 460: 220-229

25. ONo T, N MURATA 1978 Temperature dependence of the photosynthetic activities in thethylakoid membranes from the blue-green alga Anacystis nidulans. Biochim Biophys Acta.

529Plant Physiol. Vol. 63, 1979

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530 FORK, MURATA, AND SATO Plant Physiol. Vol. 63, 1979

In press 28. SHERIDAN RP 1966 Photochemical and dark reduction of sulfate and thiosulfate to hydrogen26. RAISON JK, JM LYONS, WW THOMPSON 1971 The influence of membranes on the temperature- sulfite in Synechococcus lividus. PhD thesis. Univ Oregon, Eugene

induced changes in the kinetics of some respiratory enzymes of mitochondria. Arch Biochem 29. SINGER SJ, GL NICOLSON 1972 The fluid mosaic model of the structure of cell membranes.Biophys 142: 83-90 Science 175: 720-731

27. SATO N, N MURATA, Y MIURA, N UETA 1978 Effect of growth temperature on lipid and fatty 30. WATSON K, E BERTOLI, DE GRIFFITHS 1975 Phase transitions in yeast mitochondrial mem-acid compositions in the blue-green algae Anabaena variabilis and Anacystis nidulans. branes. The effect of temperature on the energies of activation of the respiratory enzymes ofBiochim Biophys Acta. In press Saccharomyces cerevisiae. Biochem J 146: 401-407

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