Uptake of Neutral Red by the Vacuoles of a Green Alga, Micrasterias pinnatifida

Neutral red (NR) in the culture medium entered the vacuolesof a green alga, Micrasterias pinnatifida, at a higher rateat pH 8 than at pH 5. NR remained soluble in vacuoles of cellscultured at pH 5, while it precipitated and formed granulesin cells cultured at pH 8. The vacuoles of cells cultured atpH 8 contained fibrils, but those of cells cultured at pH 5did not. The amount of NR that entered the cells was markedlyreduced by the addition to the medium of nigericin at 10^-5M,monensin at 10^-5M, bafilo-mycin A₁ at 10^-5M, or ammonium chlorideat 50 mM. The formation of NR granules in vacuoles were stronglyinhibited and the disorganization of NR granules were acceleratedby the addition of nigericin at 10^-5M, or bafilomycin A₁ at10^-5M to the culture medium. The possibility is discussed thatNR which enters vacuoles might become positively charged (NRH⁺)by protons brought into vacuoles by proton pumps and that NRH⁺might combine with some negatively charged macromolecules toform aggregates or granules. (Received April 18, 1996; Accepted May 27, 1996)     

Effects of Some Metabolic Inhibitors on Heterocyst Formation in the Blue-green Alga, Anabaena doliolum

3, p-chlorophenyl urea, dinitrophenol, iodoacetic acid, andsodium azide inhibit heterocyst formation, whereas maleic hydrazidedoes not. Glucose promotes the frequency of heterocysts andis very effective in counteracting the inhibition by CMU andazide. The DNP inhibition is not reversed by glucose but ATPcauses a partial reversal. The iodoacetic acid inhibition isreversed partially by pyruvic acid; ATP and glucose are ineffectivein this case. Red light increases heterocyst frequency; greenand blue lights are inhibitory. It is concluded in the light of the mechanisms of action ofthe inhibitors that heterocyst formation depends on the availabilityof carbon intermediates and ATP. The former is supplied by photosynthesisand the latter most probably by oxidative metabolism.     

Effects of Metabolic Inhibitors on the Calcification of a Freshwater Green Alga, Gloeotaenium loitlesbergarianum Hansgirg. 1. Effects of Some Photosynthetic and Respiratory Inhibitors

The effect of a number of metabolic inhibitors on the calcificationof Gloeotaenium loitlesbergarianum Hansgirg, a freshwater greenalga, was studied. The inhibitors used were methylamine, trimethylamine,mercuric chloride, imidazole, fluoride, arsenate, atrazine,DCMU and dinitrophenol. The effects of these inhibitors showthat transport, or stimulation of respiratory carbon dioxideevolution inhibits calcification. Calcification in Gloeotaeniumis, at least partly, due to a local rise in pH as a result ofphotosynthetic carbon dioxide assimilation. There is also someevidence that, apart from its role in carbon dioxide assimilation,photosynthesis supplies the additional energy needed for calcification. Calcification, Gloeotaenium loitlesbergarianum Hansgirg, green algae, Chlorophyceae, metabolic inhibitors, photosynthesis, respiration     

Effect of Inhibitors of Bacterial Cell Wall Synthesis on the Growth of Anabaena variabilis,a Blue-green Alga

The effects of penicillins and several other antibiotics (vancomycin, ristocetin, bacitracin, novobiocin, and d-cycloserine), all known as inhibitors of bacterial cell wall synthesis, were tested on the growth of Anabaena variabilis, a strain of blue-green alga.

All the antibiotics tested inhibited the growth of Anabaena variabilis at concentrations ranging from 10 µg to 1 mg per ml. However, penicillins and the other antibiotics tested did not inhibit growth of strains of green algae.     

Effects of Metabolic Inhibitors on the Calcification of a Freshwater Green Alga Gloeotaenium loitlesbergarianum Hansgirg. 2. Effects of Some Inhibitors of Protein Synthesis

The effects of five inhibitors of protein synthesis, viz. streptomycin,aurin tricarboxylic acid, tetracycline, chloramphenicol, andcycloheximide, on the calcification of Gloeotaenium loitlesbergarianumHansgirg, a freshwater green alga were studied. Streptomycinhad no effect while aurin tricarboxylic acid at 50 µgml^–1 and tetracyline, chloramphenicol and cycloheximideat 20 µg ml^–1 completely inhibited calcificationin the alga. High concentrations of chloramphenicol and cycloheximidewere not completely inhibitory when added 26 h and 32 h respectivelyafter the material was incubated in the induction medium. Itis concluded that the effects by these substrates are the resultsof inhibition of protein synthesis, which is directly or indirectlylinked to calcification. calcification, Gloeotaenium loitlesbergarianum Hansgirg, green alga, chlorophyceae, protein synthesis inhibitors     

Characteristics of the Deposition of Microfibrils during Formation of the Polylamellate Walls in the Coenocytic Green Alga Chamaedoris orientalis

Characteristics of the deposition of cellulose microfibrilsduring formation of polylamellate walls and the arrangementof cortical microtubules in the tip-growing bipolar cells ofChamaedoris orientalis were examined by replica preparationmethods and indirect immunofluorescence microscopy. The polylamellatewall is made up of two or three kinds of wall lamella whichdiffer in terms of the orientation of microfibrils. Individuallamellae were periodically initiated one after another fromthe pole that was situated exactly at each growing apex of thecell and they were deposited basipetally. The orientation ofmicrofibrils in each lamella was constant during deposition.Microfibrils in different lamellae were deposited at the sametime through the cell wall but the timing of the depositionwas staggered between neighboring lamellae so that the microfibrilswould not be interwoven. By contrast, cortical microtubuleswere persistently arranged longitudinally all over the celland no focal points to which they converged helically were visible,even around the cell apices. The mechanisms that regulate theformation of the polylamellate wall are discussed and a modelfor interpreting the involvement of the cortical microtubulesin such mechanisms is proposed. (Received July 31, 1989; Accepted January 27, 1990)     

Characteristics of Chlorophyll Formation in the Green Alga Golenkinia

Cells of the alga Golenkinia are bleached by growth in darknessin media containing sodium acetate. Re-greening of these cellsis light dependent; neither glucose nor intermediates of chlorophyllsynthesis can substitute. The amount of chlorophyll synthesizedis proportional to the light intensity between darkness and1,000 lux and to the duration of the exposure. Initially, onlychlorophyll a is synthesized. After 9–12 hr illumination,formation of chlorophyll b and carotenoids begins. Chlorophyllproduction apparently occurs in two stages: (1) the first 12–16hr of greening. This stage is sensitive to cyanide, azide oranaerobiosis and relatively resistant to DCMU. (2) the second16–24 hr of greening. This stage is sensitive to DCMUand relatively resistant to inhibitors of respiration. Glucosestimulates greening in both stages. The metabolic requirementsof chlorophyll synthesis are discussed. (Received December 17, 1980; Accepted June 25, 1981)     

Transformation of trans-Golgi Network During the Cell Cycle in a Green Alga, Botryococcus braunii

trans -Golgi network (TGN), and the changes in its structure and behavior throughout the cell cycle of a unicellular green alga, Botryococcus braunii, were examined with deep-etching replicas and in cryo-fixed/freeze-substituted specimens. In interphase cells, the TGN consisted of a hemispherically shaped cisterna (TGN-cisterna) with regularly distributed pores on the surface and a tubular network (TGN-tubules) with clathrin-coated vesicles. The TGNs changed their structure drastically throughout the cell cycle. The TGN-cisterna disappeared from the beginning of nuclear division to the completion of the cell wall, in contrast that TGN-tubules with the clathrin-coated vesicles were always observed. The TGN-tubules produced at least five other kinds of vesicles depending on the stage of the cell cycle: 200-nm vesicles with fibrillar substances and multivesicular bodies in interphase, 180–240 nm vesicles during cell division, and 400–450 nm vesicles containing fibrils and small masses of electron-dense substances, and 200-nm vesicles containing electron-dense spherical substances just after cell division. During cell wall formation, TGN-tubules were small and had only a few clathrin-coated vesicles. After cell wall formation, TGN-tubules grew and a TGN-cisterna with pores appeared again. Received 19 October 1998/ Accepted in revised form 1 March 1999     

Phosphorus-Limited Growth of a Green Alga and a Blue-Green Alga

The phosphorus-limited growth kinetics of the chlorophyte Scenedesmus quadricauda and the cyanophyte Synechococcus Nägeli were studied by using batch and continuous culturing techniques. The steady-state phosphate transport capability and the phosphorus storage capacity is higher in S. Nägeli than in S. quadricauda. Synechococcus Nägeli can also deplete phosphate to much lower levels than can S. quadricauda. These results, along with their morphological characteristics, were used to construct partial physiological profiles for each organism. The profiles indicate that this unicellular cyanophyte (cyanobacterium) is better suited for growth in phosphorus-limited oligotrophic niches than is this chlorophyte (green alga).     

Division of Chloroplasts in a Green Alga, Pediastrum duplex

The division of chloroplasts in a green alga, Pediastrum duplex,was studied by electron microscopy. Cells were treated for observationwith the freeze-substitution method. Fibrils, or fibrous belts,which we had observed previously at the dividing constrictionsof chloroplasts in Trebouxia potteri were not visible in Pediastrum,even though the method of preparation was the same for bothsets of samples. Microtubules (MTs) and the septum seem notto participate directly in the division of the single chloroplastin Pediastrum cells. Many thin fibrils, 7–20 nm in diameter,attached to, or protruding from, the surface of the dividingconstriction were seen. These fibres were less densely distributedat the constrictions of non-dividing chloroplasts. It is suggestedthat these fibrils are involved in the divison of chloroplastsin Pediastrum duplex. Cell wall, chloroplast division, freeze-substitution, intermediate fibres, Pediastrum duplex, transmission electron microscopy     

Division of Chloroplasts in a Green Alga, Trebouxia potteri

The division of chloroplasts in Trebouxia potteri was studiedby electron microscopy. At the beginning of chloroplast division,vesicles with fine fibrils (FVs) and ER attach to the isthmusof the chloroplast. Then, filaments appear around the isthmusparallel to the direction of constriction and seem to contractin order to decrease the diameter of the isthmus. It is suggestedthat the FVs are involved in the formation of the filamentsand that the ER is involved in the contraction of the filaments.At the final stages of the division of the chloroplast, thefilaments decompose. FVs are partially surrounded and decomposedby lysosomal sheets. For the next cycle of division of the chloroplast,the recovery of substances from decomposed filaments by functionalFVs seems a realistic possibility. chloroplast division, division apparatus, division cycle, transmission electron microscopy, Trebouxia potteri.     

Division of Chloroplasts in a Green Alga, Trebouxia potteri

The division of chloroplasts in Trebouxia potteri was studiedby electron microscopy. At the beginning of chloroplast division,vesicles with fine fibrils (FVs) and ER attach to the isthmusof the chloroplast. Then, filaments appear around the isthmusparallel to the direction of constriction and seem to contractin order to decrease the diameter of the isthmus. It is suggestedthat the FVs are involved in the formation of the filamentsand that the ER is involved in the contraction of the filaments.At the final stages of the division of the chloroplast, thefilaments decompose. FVs are partially surrounded and decomposedby lysosomal sheets. For the next cycle of division of the chloroplast,the recovery of substances from decomposed filaments by functionalFVs seems a realistic possibility. chloroplast division, division apparatus, division cycle, transmission electron microscopy, Trebouxia potteri     

Blue Light-Induced Lethality of a Cell Wall-Deficient Mutant of the Unicellular Green Alga Chlamydomonas reinhardtii

When synchronized cultures of a cell wall-deficient Chlamydomonasreinhardtii mutant strain were grown under heterotrophic conditionsand subsequently transferred to the light, a considerable decreaseof the cell number was observed during transition to the celldivision phase. Lethality of the wall-deficient cells was inducedby blue light, but not by red or far-red light, and could notbe prevented by addition of the photosystem II inhibitor DCMU.The light-induced lethality was found to be restricted to wall-deficientcells which were agitated by bubbling with filtered air or nitrogenor vigorously shaken during the transition to the cell divisionphase. Therefore, a (blue) light-induced sensitivity to anymechanical stress seems to be the cause for cell death. In heterotrophicallygrowing cultures of the Chlamydomonas wild-type, illuminationwith blue or white light did not cause a decrease of the cellnumber but only a delay of cell divisions. The latter effectwas also observed in case of the wall-deficient mutant. Bothblue light effects are observed during the transition to thecell division phase and can be induced during the same periodof the cell cycle. Furthermore, the (blue) light-induced lethalityof wall-deficient cells was found to be prevented when the transitionto the cell division phase was inhibited by addition of antibiotics.Therefore, we assume that there is a connection between theblue light-induced sensitivity to mechanical stress and theblue light-induced delay of cell divisions. (Received September 3, 1993; Accepted November 12, 1993)