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1.
Potassium requirement for cell division in Anacystis nidulans.   总被引:1,自引:0,他引:1       下载免费PDF全文
A potassium requirement for growth can be readily demonstrated in the autotrophic blue-green bacterium Anacystis nidulans strain TX20 equivalent to 0.7% of the cellular dry weight. Starvation of this organism for potassium partially dissociates growth from cell division, thereby inducing 50% of the population to form filaments.  相似文献   

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Summary Genetic transformation experiments have been performed in Anacystis nidulans using donor material from two sources, namely chemically extracted DNA and extracellular nucleic acids. A high proportion of the transformants became mutant at sites which were wild type in both parental strains. Linkage was less extensive in transformation mediated by chemically extracted DNA, and this increased frequency of recombination was associated with enhanced mutation frequencies. The frequencies of recombination and mutation were varied to the same extent by changing the DNA concentration, and both processes were prevented by pretreatment of donor DNA with DNase. Mutational events are, therefore, closely associated with recombination in A. nidulans.  相似文献   

5.
Summary The blue-green alga, Anacystis nidulans was successfully synchronized in continuous light (15,000 lux) by a 14 hr cycle, consisting of 8 hrs at 26°C, and 6 hrs at 32°C, coupled with periodic dilution of the algal suspension to a constant cell number at the end of each cycle. The alga continues to grow at the lower temperature, and a division burst begins 2 hrs after transfer to the higher temperature.
Zusammenfassung Die Cyanophycee Anacystis nidulans wurde in Dauerlicht von 15 000 Lux vollständig synchronisiert. Die Cyclen bestehen aus 8 Std bei 26° C und 6 Std bei 32° C, an ihrem Ende wurde jeweils mit frischer Nährlösung auf die Ausgangszellzahl von 3·107 Zellen/ml verdünnt. Bei beiden Temperaturen kann sich die Alge vermehren, unter den synchronisierenden Bedingungen des Temperaturwechsels beginnt der Teilungsschub (Verdopplung der Zellzahl) bei 32° C nach 2 Std.


Pringsheim (1968) renamed this alga as Lauterbornia nidulans.  相似文献   

6.
A new technique of short alternating lightdark periods was successfully used to synchronize the blue-green alga Anacystis nidulans. Oxygen evolution during the cell cycle is characterized by a maximum in the middle of the cycle and by a minimum at the time of division, a pattern very similar to that found in synchronized green algae.  相似文献   

7.
Phycobilisomes were demonstrated in Anacystis nidulans by chemical and morphological studies on cells grown in red light. These cells showed a marked reduction in the chlorophyll-phycocyanin ratio owing to a decreased chlorophyll content. Granular structures of approximately 35 nm were observed throughout red light-grown cells, but were most distinct in the peripheral region. The presence of phycobilisomes in cells grown in red light as well as in cells grown in white light is supported by experiments in which glutaraldehyde was used to stabilize the attachment between the phycobiliprotein and the thylakoids, allowing the isolation of both in the same fraction by sucrose density gradient centrifugation.  相似文献   

8.
Maureen A. Dewar  J. Barber 《Planta》1974,117(2):163-172
Summary Anacystis nidulans will take up and accumulate chloride ions. When the external concentration was 0.2 mM Cl- the level in the cells was 2.8 mM Cl- and under these conditions the flux across the cell surface was in the region of 10-13equiv Cl-·sec-1·cm-2. It is suggested that this Cl- influx is active and operates against an electrochemical potential gradient estimated to be 117 mV or 2.68 kcal/mole. The uptake of 36Cl was inhibited by low temperatures and there was a net loss of Cl- from the cells with the level decreasing towards the equilibrium value as estimated from K+ distribution. Although the active influx of Cl- was often stimulated by light this was not always the case. Dark storage treatment and regulation of the chlorophyll a/phycocyanin ratios as well as total pigment content of the cells did not clarify the conditions which brought about light stimulation. Moreover, the metabolic inhibitors CCCP and CMU and also the use of anaerobic conditions did not clearly indicate the relationship between the influx mechanism and light-dark metabolism and no firm conclusions could be made about the nature of the energy source. The variation in the degree of light stimulation probably reflects the fact that in this procaryotic organism the photosynthetic and respiratory units are located on the same membrane systems and are in very close proximity to the probable site of the Cl- pump, the plasmalemma.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - CMU 3-(4-chlorophenyl)-1,1-dimethylurea  相似文献   

9.
Cation regulation in Anacystis nidulans   总被引:1,自引:1,他引:1  
Maureen A. Dewar  J. Barber 《Planta》1973,113(2):143-155
Summary Anacystis nidulans accumulates K+ in preference to Na+. The majority of the internal K+ exchanges with 42K by a first order process at rates of about 1.3 pequiv·cm-2·sec-1 in the light and 0.26 pequiv·cm-2·sec-1 in the dark. Although the K+/K+ exchange was stimulated by light and inhibited by 10-4 M CCCP and 10-5 M DCMU there are several indications that this cation is passively distributed in Anacystis. Inhibition of the exchange by CCCP and DCMU occurred at concentrations greater than those required to inhibit photosynthesis and the K+ fluxes were stimulated by low temperatures. Moreover, although valinomycin stimulated the exchange this compound did not induce a net K+ leak. Assuming K+ is passively distributed and in free solution within the cytoplasm, as indicated by osmotic studies, would imply that there is an active Na+ extrusion pump operating in this organism. As yet there are no firm conclusions about the nature of the energy source for this efflux pump.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea  相似文献   

10.
Cells of Anacystis nidulans strain 1402-1 incorporate [methyl-3H]thymidine or [8-3H]adenine into DNA; in synchronous cultures (21/2 h full light, 1/2 h weak light, 5 h dark), this incorporation occurs in the dark to different extents according to the labeled precursor offered or to its specific activity. The specific activity of in vivo, uniformly labeled DNA decreases to half the initial value when the cells are grown in the absence of radioactive DNA precursors during the light phase; it does not decrease during the following dark phase. If unlabeled thymidine is given during the dark phase, the specific activity of the DNA starts to decrease at the onset of the next light phase. The time course of the decrease supports the hypothesis that all cells start their DNA replication immediately after illumination and that the first cells have completed if after 1.25 h. The slowest cells then need 3.75 h for completion of DNA replication. It is discussed whether the incorporation during the dark might be due to pool size effects.  相似文献   

11.
Phycobilisomes in Anacystis nidulans can be seen more readily in spheroplasts than in cells with intact walls.  相似文献   

12.
Polyphosphate-deficient mutants of Anacystis nidulans have been isolated by either ethyl methanesulfonate (EMS) or N-methyl nitrosoguanidine (NTG) mutagenesis and penicillin-enrichment techniques. Mutagenised stock was preincubated in a medium lacking sulfate, then transferred to a phosphate-lacking medium before penicillin treatment. Many single-colony isolates, in contrast to wild-type, show little growth in absence of phosphate, and have altered polyphosphate, and have altered polyphosphate kinase levels indicating that the lesions affect either the activity or the expression of this enzyme. In these same mutants radioactive phosphate incorporation is severely retarded. Electron micrographs confirm the absence of polyphosphate granules in some mutants.  相似文献   

13.
Photosynthetic Membrane System in Anacystis nidulans   总被引:10,自引:8,他引:10       下载免费PDF全文
Cultures of Anacystis nidulans were grown under conditions of varying light intensity and temperature. Changes in pigment content were compared with changes in the fine structure of these cells. Pigment concentration and lamellar content varied inversely with the light intensity in cells grown with 100 and 1,000 foot candles of fluorescent light. Estimations of the relative area and volume of lamellae in cells showed that the amount of double membrane was directly proportional to the chlorophyll content of whole cells. Continuity of double membranes with cytoplasmic membrane was observed.  相似文献   

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Cells of Anacystis nidulans grown at 30°C were incubatedwith 14C-Chlorella protein hydrolysate at the elevated temperatures(30–55°C) and the effect of heat shock treatment onprotein synthesis was studied. Incubation temperatures higherthan 45°C caused a significant decrease in the incorporationof amino acids into proteins. Further, the heat shock treatmentinduced significant changes in the fluorographic profile ofthe newly synthesized proteins. (Received October 25, 1985; Accepted December 4, 1985)  相似文献   

16.
Summary The tolerance of the unicellular blue-green alga Anacystis nidulans to nitrosoguanidine increased from an initial level of 5 g NTG/ml to 20 g/ml during the course of 10 successive transfers in NTG-supplemented medium.Single treatments of log-phase cells with NTG at pH 5–6 resulted in a significant increase in the frequency of streptomycin-resistant mutants but only a marginal increase in the frequency of ultraviolet-resistant mutants was observed following single or 10 successive treatments with NTG.Attempts to score mutants resistant to penicillin, aminotriazole or NTG were unsuccessful since these agents failed to effectively kill or bleach the sensitive background population on the agar plates.  相似文献   

17.
Chloride uptake by the cyanobacterium Anacystis nidulans at 38°C is energy dependent showing maximum rate (around 5.10-7 mol Cl-xml cell water-1xmin-1) and accumulation (up to 160 fold) in light and air. The respective values in air and darkness were 40–70% lower. In the dark under N2 no uptake was found. Chloride transport had an optimum at pH 6.7 and a K M of 2.10-5 M which was pH-independent. It was inhibited by carbonyl cyanide m-chlorophenylhydrazone and N,N′-dicyclohexylcarbodiimide in the light and in the dark, and also to a lesser extent by valinomycin. 3-(3,4-dichlorophenyl)-1,1-dimethylurea in the light caused a moderate stimulation. To obtain information about the energy source of active chloride transport the action of the four inhibitors on membrane potential (determined through the distribution of triphenylmethylphosphonium) and ATP level (determined by the firefly method) was examined. It was found that a high negative membrane potential was unfavorable for chloride accumulation probably by stimulating passive efflux. On the other hand a good correlation between ATP level and chloride transport activity was obtained. Attempts to induce chloride uptake by sudden acidification of the external medium in presence of N,N′-dicyclohexyl-carbodiimide or during anaerobiosis were not successful. Two mechanisms of chloride uptake are discussed:
  1. primary active transport by an ATP-dependent pump, and
  2. “chemiosmotic” secondary active transport linked to a proton gradient, the present data favoring mechanism a.
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18.
Structure of oxidized flavodoxin from Anacystis nidulans   总被引:7,自引:0,他引:7  
The structure of oxidized flavodoxin from the cyanobacterium Anacystis nidulans has been determined at 2.5 A resolution with phases calculated from ethylmercury phosphate and dimercuriacetate derivatives. The determination of partial sequences, including a total of 85 residues, has assisted in the interpretation of the electron density. Preliminary refinement of a partial model (1072 atoms) has reduced R to 0.349 for the 10.997 reflections between 2.0 and 5.0 A with 1 greater than 2 sigma. The polypeptide backbone, which comprises 167 residues in the current model, adopts the familiar beta-alpha-beta conformation found in other flavodoxins and in the nucleotide-binding domains of the pyridine-nucleotide dehydrogenases, with five parallel strands in the central sheet. Comparison with flavodoxin from Clostridium MP (138 residues) shows that extra residues of A. nidulans flavodoxin are accommodated in a major insertion about 20 residues in length, which forms a lobe adjacent to the fifth strand of parallel sheet, and in additions to several external segments. Residues added between the fourth sheet strand and the start of the third helix alter the environment of the pyrimidine end of the flavin mononucleotide ring. The flavin mononucleotide phosphate binds to the start of helix 1, interacting with hydroxyamino acids and with main-chain amide groups. Two hydrophobic residues, both tentatively identified as Trp, enclose the isoalloxazine ring; the solvent-exposed Trp is nearly parallel to the flavin ring. The hydrophobic environment provided by these residues must be partly responsible for the pronounced vibrational resolution of the flavin spectrum near 450 nm. The flavin ring is tilted relative to its orientation in Clostridium MP flavodoxin. In addition, atoms N-3 and O-2 alpha of the isoalloxazine appear to form hydrogen bonds to the backbone at CO97 and NH99 in a conformation entirely different from that found in Clostridium MP flavodoxin but structurally analogous to Desulfovibrio vulgaris flavodoxin.  相似文献   

19.
Aminolevulinic acid, the common precursor of linear and cyclic tetrapyrroles, can arise either by condensation of succinate and glycine or from the ent  相似文献   

20.
Summary A mutant strain of the blue-green alga Anacystis nidulans showing a 1000-fold increased resistance to streptomycin over the parental strain was isolated following treatment with diethyl sulphate. The mutant strain was found to show profuse filamentation, partial requirement of streptomycin for pigment production, and greater resistance to ultraviolet radiation. It also showed greater sensitivity to dimethyl sulphate than the parental strain. It seems that the streptomycin-resistant strain is a composite one comprising at least four kinds of mutations, namely streptomycin-resistance, filamentation, u.v.-resistance and partial dependence on streptomycin for pigment accumulation. Further. the streptomycin-resistant mutant seems nuclear rather than extra-nuclear in nature.Treatment with diethyl sulphate also conferred a slight increase in resistance to penicillin in this alga.  相似文献   

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