Ribosomes from the blue-green alga Anabaena variabilis

Summary Extracts from the blue-green alga Anabaena variabilis were prepared by ultrasonic disintegration or by extrusion through a French pressure cell; examination by sucrose density gradient centrifugation and analytical ultracentrifugation indicated the existence of a procaryotic (70S) ribosome. However both the ribosomes and their sub-units were found to be relatively unstable after isolation and examination in tris buffer pH 7.4 but not in 10^-3 m-sodium phosphate buffer pH 7.0 containing 10^-1 m-potassium chloride. Experiments with ³²P and ³⁵S isotopes indicated that this instability was associated with the loss of ³⁵S labelled material, presumably therefore protein rather than nucleic acid. A comparison of behaviour with that of bacterial ribosomes is presented and the existence of certain similarities to ribosome preparations from chloroplasts of several plant species discussed.     

Photoorganotrophic growth of a blue-green alga, Anabaena variabilis

By training Anabaena variabilis in the presence of glucose andcasamino acids, the cells became proliferable without a supplyof CO₂. Their growth under these conditions was not affectedby CMU and their growth rates were linearly proportional tothe light intensity, inferring that this growth was independentof photosystem II action and its nutritional mode was of photoorganotrophicnature. The process of transition to this nutritional mode includedat least two consecutive stages: relief from the susceptibilityto organic substances which initially evoked arrest of cellgrowth, followed by the shift of cellular metabolism to organotrophy.In cells grown photoorganotrophically, the contents of phycobilinpigments decreased to nearly one-fifth as much as that of lithotrophicallygrown cells with concomitant degradation of the activity ofphotosynthetic oxygen evolution, while the chlorophyll contentsremained less altered. Accompanying these results, the activityfor incorporating external amino acids into cellular proteinswas enhanced several hundred times. Neither in the dark norin anaerobiosis was this organotrophic growth permitted butwhen light too dim to support lithotrophic growth was supplied,the organotrophic growth was affected at a slow but discerniblerate. (Received August 2, 1974; )     

Die-offs of the blue-green alga,Anabaena variabilis,in fish ponds

Dense populations of the blue-green alga, Anabaena variabilis, frequently develop in fish ponds at Auburn, Alabama, during windy weather in March and early April. Massive die-offs of this alga can be expected when it forms surface scums during prolonged periods of calm, clear, warm weather between mid April and mid May. Dissolved oxygen concentrations decline following die-offs and fish kills may result.     

Photosystem I-dependent oxidation of organic acids in blue-green alga, Anabaena variabilis

Photosynthetic lamellar fragments isolated from photoautotrophicallygrown cells of Anabaena variabilis were tested for their methylviologen photoreduction activity by coupled oxygen uptake inthe presence of CMU. Four kinds of organic acids, glycolate,malate, succinate and isocitrate, were found to serve as electrondonors of photosystem I, bypassing photosystem II, as in thecase of reduced DCPIP. Spectrophotometric measurement revealedthat the dark reduction of photooxidized cytochrome f and P700was markedly accelerated if one of the four organic acids waspresent. (Received April 18, 1975; )     

Intracellular ATP level and light-induced inhibition of respiration in a blue-green alga, Anabaena variabilis

To evaluate the possibility that the respiration of photosyntheticorganisms competes with photophosphorylation for ADP in vivo,we determined the intracellular ATP level in cells of Anabaenavariabilis under various respiratory conditions; maintainedin darkness, light-inhibited or uncoupled. No substantial differencein ATP level was observed between the light-inhibited and dark-keptcells. Under dark anaerobic conditions, however, the ATP leveldecreased to nearly one-third that of the aerobic level, indicatinga capacity for oxidative phosphorylation in this alga. In thepresence of 10^–5 M CCCP, the ATP level was reduced toabout half that of the control, but the light-inhibited respirationwas not eliminated by this agent, suggesting that it is notdue to the decreased ADP level. A possible mechanism for thephotoinhibition is discussed with special reference to the procaryoticintracellular structure of this alga. (Received October 24, 1975; )     

The C550 photoresponse at room temperature observed in membrane fragments of the blue-green alga Anabaena variabilis

The C550 photoresponse at room temperature was studied withmembrane fragments of the blue-green alga Anabaena variabilis.The kinetics, light minus dark difference spectrum and DCMUeffect were the same as those reported for spinach chloroplasts.The photoresponse size suggested that the number of the photosystemII center is half that for the photosystem I center in thisorganism grown under our autotrophic culture conditions. (Received September 16, 1975; )     

The light-induced oxidation-reduction reaction of cytochrome b-559 in membrane fragments of the blue-green alga Anabaena variabilis

Light-induced oxidation-reduction reactions of cytochrome b-559were investigated with membrane fragments of Anabaena variabilisand supplementarily with Plectonema boryanum. The oxidation-reduction reactions of cytochrome b-559 observedwith membrane fragments were similar in their kinetics to thoseof the cytochrome in aged chloroplasts. The reactions were annihilatedby the addition of Ferro, indicating that the cytochrome ofhigh redox potential (E'_o=+373 mV, pH 6.5) was photoreducedand oxidized. Titration with reducing agents indicated that cytochrome b-559is contained in Anabaena membrane fragments in an amount 1.5times as much as the content of P700 on a molar basis; the contentof the species of high redox potential was estimated to be around70%. Kinetic treatment of the photoreduction indicated that the cytochromewas reduced at some site of the electron transport system betweenthe two photosystems. The photo-oxidation depended on the actionof either photosystem II or I even in the presence of DCMU,indicating that the photooxidation was induced by both photosystems.The oxidation by photosystem I action was inhibited by HgCl₂-treatment,indicating that this reaction is mediated by plastocyanin. EDTA (5?10^-3 M) suppressed the cytochrome photoreduction andenhanced the rapid phase of the photooxidation. The latter effectappeared only when an appropriate dark time (3 min) was insertedafter the cytochrome photoreduction. The phenomenon was interpretedas showing that EDTA modifies the reactivity of the electroncarrier which directly donates electrons to cytochrome b-559.The oxidation, and probably also the reduction of cytochromeb-559, was assumed to be regulated by the oxidation-reductionstate of this carrier. (Received April 26, 1974; )     

Association of NAD and NADP linked glyceraldehyde-3-phosphate dehydrogenase in the blue-green alga,Anabaena variabilis

Summary Gel-filtration of glyceraldehyde-3-phosphate dehydrogenase from Anabaena variabilis indicates a mol. wt. of 200,000–300,000, which is significantly greater than previously reported for this enzyme from other sources. Reaction rates in the presence NAD of and NADP suggest that one enzyme only is operative, being active with either coenzyme at any one time. Centrifugation and electrophoretic studies support this conclusion. The possible consequences of these results in the control of intermediary metabolism are discussed.     

A probable lack of function of c-type cytochrome in the photosynthetic system of the blue-green alga Anabaena variabilis

Quantitative study of the cytochrome c acting in the photosyntheticsystem of the blue-green alga Anabaena variabilis (M-2) wasdone with membrane fragments and intact cells. Membrane fragments highly active in the NADP⁺-Hill reaction(above 200 µmoles/mg chl.a;-hr) retained photoresponsivecytochrome c equal only one-tenth that of P700, while the plastocyanincontent was almost equal to that of P700. The cytochrome contentin intact cells was a little larger than that in membrane fragmentson the chlorophyll a basis. However, the values relative toP700 (1/9) and plastocyanin (1/10) were identical with thosein membrane fragments. The content was also far smaller thanthat of reaction center II's (1/6). If the cytochrome mediatesall electrons from reaction center II, the cytochrome oxidation-reductionshould have a rate constant of 2.4?102 sec^–1 which isone order above of the rate constant of the cytochrome reduction(2.3 to 3.5?10¹sec^–1). These quantitative relationshipsindicate that in Anabaena variabilis (M-2), c-type cytochrome,either cytochrome f or algal cytochrome c, cannot function inthe main electron flow between two reaction centers. (Received September 8, 1978; )     

Further investigation of the light-induced cytochrome b-559 reaction in membrane fragments of the blue-green alga Anabaena variabilis

Oxidation-reduction reactions of the low redox potential cytochromeb-559 were studied for membrane fragments of the blue-greenalga Anabaena variabilis. Cytochrome photooxidation was observableat room temperature when the membrane fragments had been preincubatedat room temperature in the dark. A CCCP addition (10^–4M) strongly enhanced the reaction. Oxidation consisted of a DCMU-sensitive and an insensitive reaction.The former depended on actinic illumination of short wavelength.The latter showed a dependency on longer wavelength light. Theformer was assumed to be induced by the action of photosystemII and the latter by that of photosystem I. The photosystem II oxidation was small before preincubation,and was enhanced by added DPIP or Ferro. This was interpretedas photosystem II action inducing oxidation as well as reduction;reduction being inactivated during dark incubation or beingsuppressed by added redox reagents which compete for electronacceptance from photosystem II so that oxidation was apparentlyenhanced. The oxidationreduction reactions of this cytochromewith low redox potential were assumed to be almost identicalwith those of the high redox potential form, at least in themembrane fragments of Anabaena variabilis. (Received June 8, 1975; )