Biochemical Evidence that the Higher Plant Photosystem II Core Complex is Organized as a Dimer

The organization of the pigmented multiprotein core complexof higher plant PS II has been examined. Oxygen-evolving PSII particles or thylakoid membranes of wild-type and Chi b-lessbarley were extracted with various glycosidic surfactants andelectrophoretically fractionated. The predominant multiproteincore complex II (CC II) fractions had sizes on gel electrophoresisof M_r=230,000 and M_r= 140,000 and were photochemically active.Both fractions had identical absorption spectra, contained thebeta-carotene-chl a-proteins (Cp47 and Cp43), the PS II reactioncenter subunits (Dl and D2), and the two cytochrome b₅₅₉ subunitsin unit stoichiometry. The M_r=230,000 fraction could evolveoxygen in the light and contained an M_r=33,O0O oxygen evolutionenhancer (OEE 33) polypeptide, whereas the M_r= 140,000 fractionlacked OEE 33 and could not evolve oxygen. The apparent sizesof the two fractions were also estimated by gel filtration asM_r=490,000 and M_r=220,000, respectively; the estimates by gelfiltration more accurately reflect their predicted sizes. Furtheranalyses by nondenaturing gel electrophoresis indicated thatCp47, Cp43 and the three OEE gene products probably occur ashomodimers in situ. Our data suggest that phosphorylation ofCC II subunits occurs when they are located in the oligomericform. We propose that the native state of the PS II core complexin higher plants is dimeric, and that this state, which waspreviously observed only in thermophilic cyanobacteria, is probablythe form present in all oxygenic organisms. (Received August 9, 1991; Accepted September 26, 1991)     

Preliminary Characterization of Glutathione S-Transferases That Accumulate in Callus Cells of Pumpkin (Cucurbita maxima Duch.)

Glutathione S-transferases (GSTs; EC 2.5.1.18 [EC] ) in sarcocarptissue of pumpkin (Cucurbita maxima Duch.) fruit and in callusinduced from the tissue were examined. The specific activityof GST in the callus was 6.9-fold higher than that in the tissue.The specific activity in the callus remained constant duringcultivation. Column chromatography on DEAE-cellulose, hydroxylapatite,and S-hexylglutathione-agarose was used to fractionate solubleproteins that were precipitated by ammonium sulfate at 30% to70% saturation from homogenates of the sarcocarp tissue of pumpkinfruit and the callus and GST activity was monitored. Two andseven isozymes of GST were identified in the tissue and in thecallus, respectively. Furthermore, column chromatography onSephadex G-200 and SDS-polyacrylamide gel electrophoresis, indicatedthat these GST isozymes were homo- and heterodimers of subunitsof M_r 22,000 (Puga), and 23,000 (Pugb), 24,000 (Pugc) or 24,500(Pugd). Puga and Pugb were predominant in the sarcocarp tissueand in the callus, respectively. Puga, Pugb, Pugc and Pugd hadacidic pI values of 5.45, 5.00, 5.35 and 5.75, respectively.Rabbit antiserum against Pugb did not cross-react with the threeother subunits of GST during immunoblotting. (Received July 15, 1993; Accepted December 14, 1993)     

Glycosylation of S-RNases may influence pollen rejection thresholds in Solanum chacoense

A survey of Solanum chacoense plants expressing an authenticS₁₁-RNase transgene identified a line with partial compatibilityto S₁₁ pollen. By comparing fruit set to the S-RNase levelsdetermined immunologically in single styles, the minimum levelof S₁₁-RNase required for full rejection of S₁₁ pollen was estimatedto be 18 ng per style. The S₁₁-RNase threshold levels are thusconsiderably lower than those previously reported for the S₁₂-RNase.Interestingly, these two allelic S-RNases differ dramaticallyin the extent of glycosylation, with the number of glycosylationsites varying from one (S₁₁-RNase) to four (S₁₂-RNase). It issuggested that reduced glycosylation of the S₁₁-RNase may berelated to the lower threshold for pollen rejection. Key words: Gametophytic self-incompatibility, glycosylation, pistil-by-pistil analysis, S-RNase, Solanum chacoense, threshold Received 13 August 2007; Revised 27 November 2007 Accepted 30 November 2007     

Isolation, Properties and a Possible Function of a Water-Soluble Chlorophyll a/b-Protein from Brussels Sprouts

A water-soluble Chl a/b-protein (CP673) was isolated and purifiedfrom Brussels sprouts (Brassica oleracea L. var. gemmifera DC).The protein had a molecular mass of 78 kDa and an isoelectricpoint of 4.7, consisted of three or four subunits of 22 kDaand was extremely heat-stable. Although CP673 contained aboutone Chl a per protein, the blue and red absorption bands ofChl a that consisted of three or four Chl a forms with differentabsorption maxima suggested that there are several differentmodes or sites of binding for Chl a. Chl a/b ratio of largerthan 10 also indicated that Chl b is present only in a smallfraction of CP673. The heterogeneity of CP673 in terms of compositionand binding of Chl suggests that Chl is not an intrinsic componentof the Chl-protein. Homology search showed that the N-terminalamino acid sequence of CP673 is highly homologous with thatof a 22 kDa protein that accumulates in water-stressed leavesof two Brassicaceae plants, rapeseed and radish, but not withthose of the light-harvesting Chl a/b-proteins of photosynthesis.A possible function of the water-soluble Chl-protein was discussed. (Received September 17, 1996; Accepted November 18, 1996)     

Supramolecular Assembly of Fucoxanthin-Chlorophyll-Protein Complexes Isolated from a Brown Alga, Petalonia fascia. Electron Microscopic Studies

Using a mild detergent, octyl sucrose, light-harvesting fucoxanthin-Chla/c-protein complexes of a brown alga, Petalonia fascia, wereisolated in the form of supramolecular assemblies. Negativelystained images of these assemblies (FCPAs) were extremely uniformin size and shape. Each was discoidal in shape, being 11.2 nmin diameter and 10.2 nm in height, with a small pit at the centerof disc. From the sedimentation rate (S_{20, w} = 21.6) and theobserved dimensions, the molecular mass (Mr) of FCPA was calculatedas about 697?10³, and each FCPA was deduced to contain 128 moleculesof Chl a 27 of Chl c, 69 of fucoxanthin and 8 of violaxanthin.Fresh FCPA showed highly efficient transfer of excitation energyfrom fucoxanthin to Chl a but the energetic coupling was disruptedon storage with accompanying distortion of fine structures.Given the occurrence of similar supramolecular assemblies offucoxanthin-chlorophyll a/c-protein complexes in another brownalga, Dictyota dichotoma [Katoh et al. (1989) Biochim. Biophys.Acta 976: 233], the molecular assemblies of fucoxanthin-Chla/c-protein complexes is assumed to be common to the light harvestingsystems in all brown algae. (Received December 28, 1989; Accepted March 5, 1990)     

Thylakoid Membrane Development and Differentiation: Assembly of the Chlorophyll a-b Light-Harvesting Complex and Evidence for the Origin of Mr=19, 17.5 and 13.4 kDa Proteins

Pea plants were grown under intermittent illumination (ImL)conditions. The low dosage of light given to ImL plastids limitedthe rate of chlorophyll (Chl) a and Chl b biosynthesis and,therefore, it retarded the rate of photosynthetic unit formationand thylakoid membrane development. Depending on the developmentalstage of the photosynthetic unit, ImL plastids had variableChl a/Chl b ratios (2.7 <Chl a/Chlb<20) and showed distinctintermediates in the assembly of the chlorophyll a–b light-harvestingcomplex (LHC) of photosystem-II (PSII). The results are consistentwith a step-wise increment in the PSII antenna size involvingthree distinct forms of the PSII unit: (i) a PSII-core formwith about 37 Chl a molecules; (ii) a PSIL_ß form containingthe PSII-core and the LHC-II-inner antenna with a total of about130 Chl (a + b) molecules, and (iii) the mature PSII_a form containingPSII_ß and the LHC-II-peripheral antenna with a totalof 210–300 Chl (a + b) molecules. The thylakoid membranecontained polypeptide subunits b, c and d (the Lhcb1, 2 and3 gene products, respectively) when only the LHC-II-inner waspresent. Polypeptide subunit a, (the apoprotein of the chlorophyll-proteinknown as CP29), along with increased amounts of b and c appearedlater in the development of thylakoids, concomitant with theassembly of the LHC-II-peripheral. The results suggest thatpolypeptide subunit d has priority of assembly over subunita. It is implied that, of all LHC-II constituent proteins, subunitd is most proximal to the PSII-core complex and that it servesas a linker in the transfer of excitation energy from the bulkLHC-II (subunits b and c) to the PSII-core. The work also addressesthe origin of low-molecular-weight proteins (M_r = 19, 17.5 and13.4 kDa) which co-isolate with intact developing plastids andwhose abundance decreases during plastid development. Aminoacid compositional and immunoblot analyses show a nuclear histoneorigin for these low-molecular-weight proteins and suggest co-isolationof histone-containing nuclear vesicles along with intact developingplastids. ¹Present address: Plant Physiology Research Group, The Universityof Calgary, Department of Biological Sciences, 2500 UniversityDrive N.W., Calgary, Alberta CANADA T2N 1N4.     

Determination of chlorophylls and carotenoids of marine phytoplankton: separation of chlorophyll a from divinylchlorophyll a and zeaxanthin from lutein

A rapid reverse-phase HPLC method is presented for the identificationand quantification of most of the phytoplankton pigments. Thismethod yields the resolution of divinyl-chlorophyll a and chlorophylla, as well as the partial resolution of lutein and zeaxanthin,and of divinyl-chlorophyll b and chlorophyll b. In addition,chlorophylls c_1,2 and c₃ are well resolved. The analysis timefor one sample is 20 mm, which makes this method particularlysuited when large numbers of samples have to be processed.     

The Isolation and Characterization of a Cytochrome b6f Complex from the Cyanobacterium Spirulina sp.

A cytochrome b₆f complex was isolated and purified from Spirulinasp. The complex was solubilized with n-heptyl ß-D-thioglucosideand chromatographed on a DEAE-Toyopearl 650M column. The purifiedcomplex contained a small amount of chlorophyll and carotenoid.At least four polypeptides were present in the complex: cytochromef (29 kDa), cytochrome b₆(23 kDa), iron-sulfur protein (ISP,23 kDa), and a 17 kDa polypeptide. Each polypeptide was separatedfrom the complex treated with 2-mercaptoethanol or urea. Theabsorption spectra of cytochrome b₆ and cytochrome f were similarto those of Anabaena and spinach as expected. The complex wasactive in supporting ubiquinol-cytochrome c oxidoreductase activity.Fifty percent inhibition of the activity was accomplished by1 µM dibromothymoquinone (DBMIB). The K_m values for ubiquinol-2and cytochrome c (horse heart) were 5.7 µM and 7.4 µM,respectively. (Received August 15, 1988; Accepted November 14, 1988)     

Formation of Chlorophyll-Protein Complexes during Greening. 2. Redistribution of Chlorophyll among Apoproteins

The formation of Chl-protein complexes (CPs) in cucumber cotyledonsduring a dark period after a brief illumination was studied.SDS-PAGE analysis showed that the P700-Chl a-protein complex(CP1) and Chl a-protein complex of the PS II core (CPa) increased,with a concomitant decrease in the light-harvesting Chl a/6-proteincomplex of PS II (LHCII), during 24-h dark incubation of cotyledonsafter 6h of continuous illumination. In agreement with theseresults, curve analysis revealed that spectral components characteristicof CP1 and CPa increased while those of Chi b decreased duringthe dark incubation. Since Chl is not synthesized in the dark,Chl must be released from LHCII and re-incorporated into CP1and CPa. The amounts of apoproteins of CP1 and 43 kDa protein(one of the apoproteins of CPa) increased during the dark incubation,and the increase could be inhibited by chloramphenicol (CAP).CP1 did not increase in the dark when tissues were incubatedwith CAP which inhibited the synthesis of apoproteins of CP1,indicating that CP formation by Chl redistribution needs newlysynthesized apoproteins. The decrease in LHCII apoproteins duringdark incubation was inhibited by CAP probably because Chl wasnot removed from LHCII by apoproteins of CP1 and CPa, whosesynthesis was blocked by the presence of CAP. When intermittently-illuminatedcotyledons containing a little LHCII were incubated with CaCl₂in the dark, Chl b and LHCII apoproteins accumulated with thedisappearance of 43 kDa protein; Chl of 43 kDa protein may beutilized for LHCII formation. We concluded that Chl moleculesonce bound with their apoproteins are redistributed among theapoproteins. (Received October 17, 1990; Accepted December 6, 1990)     

Properties of the Cytochrome c Oxidase Activity of Cytochrome b561 from Photoanaerobically Grown Rhodopseudomonas sphaeroides

Cytochrome b₅₆₁ from Rhodopseudomonas sphaeroides had cytochromec (c2) oxidase activity and a pH optimum at 6.0 for this activity.The activity was affected by the ionic strength of the reactionmixture. The apparent K_m and maximal velocity (V_max) valuesin the absence of addea salts were 14 µM and 120 nmoloxidized per min per mg protein for horse heart cytochrome c.Reduced horse heart cytochrome c was reoxidized in first-orderkinetics by this cytochrome b₅₆₁. The specific activity was0.7 s^–1 per mg protein at 20°C at the concentrationof 30 µMM cytochrome c. Activity was inhibited by KCN and NaN₃, but not by antimycin.The addition of a low concentration of KCN to the cytochromeb₅₆₁ produced a change in the absorption spectrum, evidencethat KCN interacts with the heme moiety of cytochrome b₅₆₁.Results of this and preceeding studies show that the cytochromeoxidase (cytochrome "o") described earlier (Sasaki et al. 1970)is cytochrome b₅₆₁. (Received May 16, 1983; Accepted September 8, 1983)     

Formation of Chlorophyll-Protein Complexes during Greening 1. Distribution of Newly Synthesized Chlorophyll among Apoproteins

The relationship between the accumulation of Chl and the apoproteinsof the light-harvesting Chl a/b-protein complex of PS II (LHCII)during the greening of cucumber cotyledons was studied. LHCIIapoproteins were not detected in etiolated cotyledons. Uponillumination, Chl a was formed as a result of photoconversionof protochlorophyllide (Pchlide) which had accumulated in thedark. During the lag period that preceded the accumulation ofChl, a small amount of LHCII apoproteins appeared. The amountof LHCII apoproteins increased with increases in levels of Chlb, though somewhat more rapidly during the first 10 h of greening.Treatment with benzyladenine (BA) or levulinic acid (LA) wasused to vary the supply of Chl a for apoproteins by promotingor inhibiting the synthesis of Chl a, respectively. LA decreasedbut BA increased the rate of accumulation of Chl b and LHCIIapoproteins. Only small amounts of Chl b and LHCII apoproteinswere formed under intermittent illumination. However, in thepresence of chloramphenicol (CAP), which inhibits the synthesisof plastome-coded proteins including apoproteins of the P700-Chla-protein complex (CP1) and a Chl a-protein complex of PS II(CPa), we observed the accumulation of Chl b and LHCII apoproteins,both of which are of nuclear origin. During incubation in thedark after intermittent exposure to light, CAP alone allowedneither destruction nor accumulation of Chl b and LHCII apoproteins,but it did enhance the effect of CaCl₂ in inducing both Chlb and these apoproteins. These results can be explained by assumingthat apoproteins of CP1 and CPa have a higher affinity for Chla than do LHCII apoproteins. When the availability of Chl ais limited, these apoproteins compete with one another for Chla, with the resultant preferential formation of CP1 and CPa.However, when the supply of Chl a becomes large enough for saturationof apoproteins of CP1 and CPa, some of the Chl a is incorporatedinto LHCII apoproteins either directly or after conversion toChl b. Thus, the formation of different Chl-protein complexes(CPs) is regulated by the relative rates of synthesis of Chla and apoproteins and by differential affinities of the apoproteinsfor Chl a. ⁴Present address: Kyowa Hakko Co., Ltd., 4041, Ami-machi, Inashiki,Ibaraki, 300-03 Japan (Received September 14, 1989; Accepted April 26, 1990)     

The Responses of Net Photosynthesis to Vapour Pressure Deficit and CO2 Concentration in Spartina townsendii (sensu lato), a C4 Species from a Cool Temperate Climate

As the initial part of a detailed study of photosynthetic CO₂assimilation in the temperate C₄ grass, Spartina townsendii,the responses of net photosynthesis to the leaf-air vapour pressuredeficit (VPD) and to CO₂ concentration are examined. Water vapourand CO₂ exchange for single attached leaves were measured undercontrolled-environment conditions in an open gas-exchange system.The responses of net photosynthesis, stomatal resistance (r_s),and residual resistance (r_r) to vapour pressure deficit(VPD)and CO₂ concentration under a range of light and temperatureconditions are reported. Net photosynthesis was insensitiveto increase in the VPD up to 1.0 kPa, but beyond this valuenet photosynthesis decreased with further increase in VPD asa result of an increase in r_s. The residual resistance was notaffected by VPD under any of the conditions examined. Net photosynthesisresponded linearly to increase in the CO₂ concentration in theexternal air (C_a up to the normal atmospheric concentrationwhere there was a sharp change in the response, net photosynthesisbeing independent of any further increase in C_a. Differencesbetween the response curves observed here and in other studiesare discussed and the possible reasons for these differencesare considered.     

Purification and Characterization of Light-Harvesting Chlorophyll a/b-Protein Complexes of Photosystem II from the Green alga, Bryopsis maxima

Light-harvesting chlorophyll a/b-proteins of photosystem II(LHC II) were purified from thylakoid membranes of the greenalga, Bryopsis maxima. Extraction with digitonin did not solubilizechlorophylls (Chl) and carotenoids to any significant extent.Two forms of purified LHC II, P4 and P5, with respective apparentparticle sizes of 280 and 295 kDa, were obtained by sucrosedensity gradient centrifugation and column chromatography onDEAE-Toyopearl. P4 and P5 had similar spectral absorption at77 K with Chl a maxima at 674, 658 and 438 nm and Chl b maximaat 649 and 476 nm. Carotene was not present in P4 or P5. Fluorescenceexcitation spectra demonstrated that Chl b, siphonaxanthin andsiphonein can efficiently transfer absorbed light energy toChl a. P4 and P5 each contained two apoproteins of 28 and 32kDa, with similar but not identical amino acid compositions.P5 contained 6 molecules of Chl a, 8 of Chl b and 5 of xanthophyll(three molecules of siphonaxanthin and one each of siphoneinand neoxanthin) per polypeptide. (Received September 11, 1989; Accepted December 11, 1989)     

Purification and Characterization of Arginine Decarboxylase from Soybean (Glycine max) Hypocotyls

Arginine decarboxylase (EC 4.1.1.19 [EC] ) was purified from soybean,Glycine max, hypocotyls by a procedure which includes ammoniumsulfate fractionation, acetone precipitation, gel filtrationchromatography, and affinity chromatography. Using this procedure,ADC was purified to one band in non-denaturing PAGE. The purifiedADC has an M_r of 240 kDa based on gel filtration chromatographyand is a trimer of identical subunits which has an estimatedM_r of 74 kDa based on SDS-PAGE. ADC is active between 30 and50°C and has a K_m value of 46.1 µM. ADC is very sensitiveto agmatine or putrescine but not to spermidine or spermine.In the presence of 0.5 mM agmatine (or putrescine), the enzymeactivity was inhibited by 70%. However, at the same concentrationof spermidine (or spermine), the enzyme activity was inhibitedby only 10–20%. (Received April 2, 1997; Accepted August 18, 1997)     

Chromatographic separation of photosystems I and II from the thylakoid membrane isolated from a thermophilic blue-green alga

The thylakoid membrane of a thermophilic blue-green alga, Synechococcussp., was separated into four chlorophyll-containing fractionsby a single chromatographic manipulation with a diethylaminoethyl-cellulosecolumn after digitonin treatment. Photosystems I and II, orchlorophyll a forms, were unevenly distributed among the fourfractions, which were designated F-1, F-2, F-3 and F-4 in theorder of elution from the column. F-1 has a simple composition of the chlorophyll a form and totallylacks photochemical activity. This fraction may be an antennachlorophyll a-protein in the blue-green alga. F-2 is rich inshorter wavelength chlorophyll a forms and shows the three-bandedfluorescence emission spectrum characteristic of photosystemII at liquid nitrogen temperature. This fraction is highly activein 2,6-dichloroindophenol photoreduction and contains one photooxidizablecytochrome b₅₅₉ per 50–100 chlorophyll a, whereas theP-700 content is as low as one P-700 per 2,000 chlorophyll a.Thus, F-2 represents photosystem II in a highly purified state.F-3 is rich in photosystem I, since this fraction is inactivein 2,6-dichloroindophenol photoreduction, and contains one P-700per 200 chlorophyll a and smaller amounts of cytochrome b₅₅₉.Longer wavelength chlorophyll a forms are abundant and a peakat 730 nm is the most prominent in the low-temperature fluorescencespectrum in this fraction. F-4, which consists of larger membranefragments shows spectral and photochemical features similarto those of F-3. (Received August 8, 1979; )     

Are Mistletoes Shade Plants? CO2Assimilation and Chlorophyll Fluorescence of Temperate Mistletoes and their Hosts

Mistletoes usually have slower rates of photosynthesis thantheir hosts. This study examines CO₂assimilation, chlorophyllfluorescence and the chlorophyll content of temperate host–parasitepairs (nine hosts parasitized by Ileostylus micranthus and Carpodetusserratus parasitized by Tupeia antarctica). The hosts of I.micranthus had higher mean annual CO₂assimilation (3.59 ±0.41 µmol m^-2 s^-1) than I. micranthus(2.42 ± 0.20µmol m^-2 s^-1), and C. serratus(2.41 ± 0.43 µmolm^-2 s^-1) showed higher CO₂assimilation than T. antarctica(0.67± 0.64 µmol m^-2 s^-1). Hosts saturated at significantlyhigher electron transport rates (ETR) and light levels thanmistletoes. The positive relationship between CO₂assimilationand electron transport suggests that the lower CO₂assimilationrates in mistletoes are a consequence of lower electron transportrates. When photosynthetic rates, ETR and chlorophyll a /b ratioswere adjusted for photosynthetically active radiation, hostsdid not have significantly higher CO₂assimilation (3.21 ±0.37 µmol m^-2 s^-1) than mistletoes (2.54 ± 0.41µmol m^-2 s^-1), but still had significantly higher ETRand chlorophyll a / b ratios. The electron transport rates,saturating light and chlorophyll a / b ratios of sun leavesfrom mistletoes were similar to host shade leaves. These responsesindicate that in comparison with their hosts, mistletoe leaveshave the photosynthetic characteristics of the leaves of shadeplants. Copyright 2000 Annals of Botany Company CO₂assimilation, photosynthetic active radiation (PAR), chlorophyll fluorescence, electron transport rate (ETR), photochemical quenching (q_p), non-photochemical quenching (q_n), sun and shade leaves, chlorophyll content, Ileostylus micranthus, Tupeia antarctica, New Zealand     

S-Locus-Specific Glycoproteins Associated with Self-Incompatibility in Brassica campestris

Specific S-glycoproteins were isolated from three Brassica campestriscultivars homozygous with respect to the S-alleles S₈, S₉ andS₁₂. Amino acid sequences of various peptide fragments of theS-proteins were determined using a gas-phase protein sequencer,and a nearly complete amino acid sequence of the S₈-glycoproteinwas determined on the basis of the revised cDNA sequence ofthe B. oleracea S-specific glycoprotein. The lysyl endopeptidasefragments of S₉ and S₁₂-glycoproteins were aligned in comparisonwith the sequence of the S₈-glycoprotein. Although extensivesequence homology was evident among the three S-glycoproteins,the sequences of the middle part were relatively different fromeach other. The numbers and positions of N-glycosylation alsodiffered among the S-glycoproteins of Brassica species. (Received April 20, 1987; Accepted July 29, 1987)     

Spectral characterization of five chlorophyll-protein complexes

Sodium dodecyl sulfate-solubilized chloroplast internal membranes of higher plants (cowpea [Vigna unguiculata L. Walp], chinese cabbage [Brassica chinensi L.], and tobacco [Nicotiana tabacum L.]) are resolved by polyacrylamide gel electrophoresis into two chlorophyll a- and three chlorophyll a,b-proteins. A small portion (about 15%) of the membrane chlorophyll migrates as a component of high electrophoretic mobility and presumably consists of detergent-complexed, protein-free pigment.

One of the chlorophyll a-proteins is qualitatively similar to the P₇₀₀ chlorophyll a-protein but contains a much larger proportion of total chlorophyll (about 30%) than previously reported. The second chlorophyll a-protein is a recently discovered component of the membrane and accounts for about 7% of the total chlorophyll. The absorption and fluorescence emission spectra of these two chlorophyll a-proteins differ.

The three chlorophyll a,b-proteins are components of the chloroplast membrane chlorophyll a,b-light-harvesting complex which was previously resolved as a single chlorophyll-protein band. The two additional chlorophyll a,b-proteins observed in our work probably represent larger aggregates contained within that membrane complex which are preserved under the solubilization and electrophoretic conditions used here.

     

Changes in cytochrome contents and respiratory activity of Bacillus cereus Strain T during germination, vegetative growth and sporulation

Vegetative cells of Bacillus cereus Strain T contain cytochromeb-562, a minor b-type component, in addition to known components,cytochrome a+a₃, cytochrome b-557 and cytochrome c-551. Also,the spores contain low but definite amounts of cytochromes b-562and c-551, which were oxidized when the spores were shaken withair. Contents of cytochromes a, b and c per cell and per cellnitrogen, and the activity of glucose oxidation increased duringspore germination and elongation. During the stage precedingfirst cell division, cytochrome contents per cell increasedin parallel with the increase of cell nitrogen, while the activityof glucose oxidation decreased. During early exponential growth,the content of cytochrome b per cell nitrogen and respiratoryactivity with glucose again increased. When cells entered thesporulation stage, characterized by structural changes insidethe cells, the activity of glucose oxidation began to decrease,while that of acetate or succinate oxidation started to increase.During the sporulation process, the contents of the three cytochromecomponents continued to increase and reached the highest levelin cells containing completed spores, but the activity of respirationwith endogenous or added substrates was negligible in thesecells. (Received November 10, 1975; )     

The optical properties of a turbid reservoir and its phytoplankton in relation to photosynthesis and growth (Mount Bold Reservoir, South Australia)

In situ light measurements were used to obtain information oninherent and apparent optical properties. The average verticalattenuation coefficient K_d(ave) varied from 1.1 to 4.6 In unitsm^–1 During three periods the variation in K_d(ave) correlatedwith changes in chlorophyll a concentration and specific attenuationcoefficients K_s, of 0.013, 0.014 and 0.022 m² mg Chl a^–1were calculated. Chlorophyll-specific diffuse absorption coefficients(A,) for these periods were 0.012. 0.013 and 0.017 m² mg Chla^–1 and only varied significantly from estimates of K_sin the period when scattering was intense. Absorption coefficientsa(z^mid) and scattering coefficients b(z^mid) calculated for themid-point of the euphotic zone ranged between 0.45 and 2.9 mand 3.5–52.0 m respectively. Chlorophyll-specific absorptioncoefficients K_a, of 0.005, 0.006 and 0.007 m² mg Chl a^–1and scattering coefficients K_b of 0.05. 0.09 and 0.191 m² mgChl a^–1 were measured during the three periods. The highK_b value occurred when gas-vacuolate cyanobactena were dominant.Algal photosynthesis and light absorption were related throughthe maximum quantum yield _m which varied between 0.019 and 0.11mol C Einstein^–1 while average quantum yields _a, variedbetween 0.006 and 0.024 with a mean of 0.013 mol C Einstein^–1A comparison of changes in the mean irradiance of the mixedzone and chlorophyll concentration indicated that growth waslight limited below 0.04–0.05 Einsteins absorbed mg Chla^–1 day^–1.