Regulatory characteristics of a fructose bisphosphatase from the blue-green bacterium Anacystis nidulans.

A specific fructose 1,6-bisphosphatase (EC 3.1.3.11) has been partially purified from the obligately autotrophic blue-green bacterium Anacystis nidulans. It was most active at pH 8.0. The K_m for fructose 1,6-bisphosphate was 0.088 mm at pH 8.0 and 0.105 mm at pH 7.0; the K_m for MgCl₂ was 0.95 mm at pH 8.0. Activity at netural pH was particularly sensitive to the MgCl₂ concentration. AMP was an allosteric inhibitor, 50% inhibition being exerted by 0.058 mm AMP at pH 7.0 and 0.085 mm AMP at pH 8.O. The way in which changes in intracellular pH and the concentrations of Mg²⁺ and AMP might influence the activity of the enzyme in the Calvin cycle, the oxidative pentose phosphate pathway and in glycolysis and gluconeogenesis is discussed.     

Effect of carbon dioxide concentration on pigmentation in the blue-green alga Anacystis nidulans

The pigment content in the blue-green alga Anacystis nidulanswas found to be dependent upon CO₂ concentration during growth.In cells grown with 1% CO₂ in air the total pigment constituted20.5% of the dry weight while it was only 11.1% of dry weightof cells grown in air (0.03% CO₂). This decrease in total pigmentwas found to be almost entirely ascribable to decrease in phycocyanin.Since light absorbed by phycocyanin has been shown to providenearly equal rates of photoreactions I and II, the "CO₂ control"of phycocyanin is viewed as an effective means of regulationof the photoreactions without upsetting the balance of operationof the two photoreactions. (Received December 25, 1970; )     

Genetic transformation of the blue-green bacterium,Anacystis nidulans

Evidence is presented which confirms the existence of genetic transformation in the blue-green bacterium, Anacystis nidulans. This process has been demonstrated for three mutations: streptomycin resistance, a phenylalanine requirement and an ornithine requirement. The optimal conditions under which transformation occurs are also investigated, and the potential of this system for genetic mapping is discussed.This work was submitted by K. G. O. in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology, Bryn Mawr College.     

Leucine biosynthesis in the blue-green bacterium Anacystis nidulans.

Leucine-requiring auxotrophs of the unicellular blue-green bacterium Anacystis nidulans have been isolated. Extracts of these mutants were deficient in alpha-isopropylmalate synthetase (EC 4.1.3.12). In wild-type cells, this enzyme was subject to feedback inhibition by leucine. However, formation of the enzymes of leucine biosynthesis was little affected by exogenous leucine in either wild-type or mutant strains. Cultures of the latter subjected to extreme leucine deprivation showed no change in specific activity of beta-isopropylmalate isomerase (EC 4.2.1.33) and at most a 50% increase in the specific activity of beta-isopropylmalate dehydrogenase (EC 1.1.1.85). These results are compared with others bearing on the evolution of the control of amino acid biosynthesis in blue-green bacteria.     

Effect of growth temperature on lipid and fatty acid compositions in the blue-green algae, Anabaena variabilis and Anacystis nidulans.

The lipid composition was affected by growth temperature in Anacystis nidulans, but was not in Anabaena variabilis. A. variabilis contained fatty acids of 18 and 16 carbon atoms, which were localized at 1- and 2-positions, respectively, of the glycerol moiety of lipids. Desaturation of C18 acids was affected by the growth temperature. A. nidulans contained fatty acids of 14, 16 and 18 carbon atoms. Monounsaturated and saturated acids were esterified mainly to 1- and 2-position, respectively. Desaturation and chain length of fatty acids were influenced by the growth temperature. The variations in lipid and fatty acid compositions with the growth temperature are discussed in relation to the growth temperature-dependent shift of thermotropic phase transition temperature of the membrane lipids in the blue-green algae.     

Mutations arising during transformation in the blue-green alga Anacystis nidulans

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.     

Evidence for genetic transformation in blue-green alga Anacystis nidulans

Summary Evidence has been presented that blue-green alga Anacystic nidulans can undergo genetic transformation. DNA from erythromycin-, streptomycin-resistant of filamentous strains has been found to transform appropriate markers to a wild type or some other recipients. Favourable conditions for transformation have been described with respect to the revealing of transformants, the concentration of DNA and the competence of cells.     

Particle aggregation in photosynthetic membranes of the blue-green alga Anacystis nidulans

Freeze-fracture electron microscopy demonstrates that in photosynthetic membranes of the blue-green alga Anacystis nidulans quenched from a temperature below growth temperature, areas devoid of membrane particles occur. We suggest that this phenomenon is related to phase transitions in the photosynthetic membrane.     

Fluorescence from sensitizing phycobilin chromophores in the blue-green alga Anacystis nidulans

Regeneration of the pigment system of Anacystis nidulans was studied following nitrate starvation. Three new, distinct fluorescence bands, at 596, 615 and 636 nm attributed to sensitizing phycobilin chromophores were detected. They each possess a separate excitation band at 425, 395 and 410 nm, respectively.     

The labelling of nucleic acids by radioactive precursors in the blue-green algae Anacystis nidulans and Synechocystis aquatilis Sanv.

Summary The labelling of nucleic acids of growing cells of the blue-green algae Anacystis nidulans and Synechocystis aquatilis by radioactive precursors has been studies. A. nidulans cells most actively incorporate radioactivity from [2-¹⁴C]uracil into both RNA and DNA, while S. aquatilis cells incorporate most effectively [2-¹⁴C]uracil and [2-¹⁴C]thymine.Deoxyadenosine does not affect incorporation of label from [2-¹⁴C]thymidine into DNA, but weakly inhibits [2-¹⁴C]thymine incorporation into both nucleic acids and significantly suppresses the incorporation of [2-¹⁴C]uracil.The radioactivity from [2-¹⁴C]uracil and [2-¹⁴C]thymine is found in RNA uracil and cytosine and DNA thymine and cytosine. The radioactivity of [2-¹⁴C]thymidine is incorporated into DNA thymine and cytosine. These results and data of comparative studies of nucleic acid labelling by [2-¹⁴C]thymine and [5-methyl-¹⁴C]thymine suggest that the incorporation of thymine and thymidine into nucleic acids of A. nidulans and S. aquatilis is accompanied by demethylation of these precursors. In this respect blue-green algae resemble fungi and certain green algae.     

Synchronous growth and genome replication in the blue-green alga Anacystis nidulans

Summary Following the induction of synchronous growth of Anacystis nidulans by light and CO₂ deprivation, cell mass and RNA and DNA content during two cell cycles were measured. Both RNA and DNA synthesis were discontinuous and marked variation in survival to ultraviolet light was related to the state of replication. A model is presented which accounts for the proportion of cells (66%) induced into synchronous genome replication which is also related to the state of replication at the onset of pre-synchrony treatment.