Artificial tripartite symbiosis involving a green alga (Chlamydomonas), a bacterium (Azotobacter) and a fungus (Alternaria): morphological and physiological characterization.

A long-living artificial tripartite symbiosis involving a green alga (Chlamydomonas), a bacterium (Azotobacter) and a fungus (Alternaria) was established on carbon- and nitrogen-free medium. The basis of the interdependence is the complementation of photosynthetic CO2 assimilation and atmospheric nitrogen fixation. Green color of the colonies indicated that the algal cells had enough nitrogen to synthesize chlorophylls. The chlorophyll content was nearly 40% of the control cells. The relatively high rate of photosynthetic oxygen evolution proved that nitrogen was effectively used for building up a well functioning photosynthetic apparatus. This was supported by the analysis of photosystems and ultrastructural investigations. In comparison with degreened algae cultured on nitrogen-free medium, the chloroplasts in the symbiont algal cells contained a well-developed, stacked thylakoid membrane system without extreme starch or lipid accumulation. The occurrence of the fungus in the association greatly increased the chlorophyll content. Far fewer types of amino acids were excreted by the tripartite cultures than by pure cultures. Cystathionine, which is a common intermediate in the sulfur-containing amino acid metabolism, was produced in high quantities by the tripartite symbiosis. This can mostly be attributed to the activity of the fungus.

[Biological activity and structure of antitumor compounds from Plantago media L]. / Plantago media L antitumor hatóanyagainak szerkezete és biológiai aktivitása.

Tyrosine kinase inhibition and tumor growth inhibition activity of verbascoside and homoplantaginin are described. Both molecules proved to be equally significant inhibitors of isolated EGF-R tyrosine kinases, nevertheless their in vitro antiproliferative activity was variable in cellular assays. Their different inhibitory efficacies could be interpreted on the basis of conformational analysis and lipophilicity evaluation.

Photosynthetic functions and thylakoid membrane polypeptide composition in light-sensitive mutants of Chlamydomonas reinhardii.

In this paper we compared the pigment composition, photochemical activity, chloroplast ultrastructure, thylakoid membrane polypeptide composition and ribosomal content of wild-type and seven light-sensitive mutants of Chlamydomonas reinhardii.All the mutants had low chlorophyll and carotenoid content compared to wild-type. Mutants lts-30 and lts-135 were also characterized by a complete absence of visible carotenoids, while mutant lts-19 was fully deficient in chlorophylls.In most mutants, the chloroplast fragment could not carry out any DCIP photoreduction and O2 evolution was also blocked. The PSI/P700/activity was decreased in most cases.The mutant strains contained mostly single lamellae in their plastids, that is the stacking capacity of the thylakoid membranes was very decreased or fully absent. In most cases the number of lamellae was also very low.The relative amounts of 70 S ribosomes were decreased in all of the mutants. The thylakoid membranes showed anomalies in the region of 24 000-30 000 dalton polypeptides. The common characteristic for them was the relatively higher amount of the 30 000 dalton polypeptide and considerably decreased level of the 27 000 and 24 000 dalton polypeptides relative to the wild-type. These polypeptides were probably constituents of the chlorophyll-protein complex II which has been suggested to be the light harvesting pigment complex for PSII. The polypeptide of 30 000 daltons is the precursor for the LHCP apoprotein (24 000 dalton protein). It may be that the lighstimulated conversion of this precursor into LHCP apoprotein was blocked in our pigment-deficient mutants.

Acid phosphatase isoenzymes of Chlamydomonas reinhardii.

Acid phosphatase isoenzymes of Chlamydomonas reinhardii were investigated by isoelectric focusing in polyacrylamide gel systems. In this paper we describe in detail an original method for isoelectric focusing of acid phosphatases extracted from wild-type and acid phosphatase-lacking mutant algae, obtained from Laboratoire de Génetique of University of Liège. Three isoenzymes can be separated from the buffer-soluble components of these cells. An additional isoenzyme type can be visualized using the nonionic detergent NP40 as solubilizer. We conclude that these four isoenzymes are related to the structural gene of the soluble constitutive acid phosphatase, which was shown by their appearance in P2 and their total absence in mutant Pa. The pI values of soluble constitutive acid phosphatase isoenzymes range between pH 5.2 and 6.2. As a result of treatment with NP40 the extracts from both wild-type and mutant lines contain two additional active phosphatase forms which can be characterized by their high heat resistance and low pI values. These enzymes are fully active using either alpha-naphthyl phosphate or different acetate esters as substrates.

Protein deficient chloroplast ribosomes in a yellow mutant of Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and a yellow mutant of Chlamydomonas reinhardii were analyzed and compared by two-dimensional gel electrophoresis. The mixothrophically grown yellow-76 mutant differs from wild-type cells in lowered chlorophyll content and photosynthetic activity per chlorophyll unit. The latter is connected with the decreased activity of the ribulose-I,5-diphosphate-carboxylase enzyme. Analytical ultracentrifugation of cell extracts shows a normal amount of free 70S ribosomes and 50S subunit in the mutant cells. Two-dimensional gel electrophoresis shows considerable alterations in the protein composition of the 70S ribosomes of the mutant. Two proteins are absent from the electrophoretograms of the yellow-76 mutant, and seven proteins are present in reduced amounts. The genetical analysis shows a Mendelian pattern of inheritance, indicating that protein alterations presumably are localized in nuclear DNA.

Altered chloroplast ribosomal proteins in a yellow mutant of Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and a yellow mutant of Chlamydomonas reinhardii were analysed and compared by two-dimensional gel electrophoresis. Mixothrophycally grown yellow-27 mutant differs from wild-type cells in lowered chlorophyll content and grana formation of the chloroplast. Analytical ultracentrifuge analyses of cell extracts show a reduced amount of free 70S ribosomes and increased level of 50S subunits in the mutant cells. Similar results were obtained by electronmicroscopical method. Two-dimensional gel electrophoresis shows alterations in protein composition of 70S ribosomes of the mutant. Two proteins of 70S ribosomes have been altered. One of them with high molecular weight is practically absent while there is an additional, intensively stained spot in the mutant. Since the mutation is inherited in a non-Mendelian manner it is possible that the protein alterations in 70S ribosome are localized in the chloroplast DNA.

Yellow mutations alter chloroplast ribosomal proteins in Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and three yellow mutants of Chlamydomonas reinhardii were analyzed and compared by two-dimensional gel-electrophoresis. Mixotrophycally grown mutants differ from wild-type cells in lowered chlorophyll content. Analytical ultracentrifugation analysis of cell extracts showed a reduced amount of 70S ribosomes and an increased level of 50S subunits in mutants y-27 and y-28. Two-dimensional gel electrophoresis indicated considerable alterations in the protein composition of 70S ribosomes of the mutants. Two proteins of 70S ribosomes were altered in the y-27 and y-28 mutants. Two proteins were absent from the electrophoretograms of the yellow-76 mutant and seven proteins were present in lowered concentrations. The mutations are inherited in a non-Mendelian manner. The protein alterations in 70S ribosome are most probably localized in the chloroplast DNA.

Studies on the biological effect of fast neutrons. II. Variation of total nucleic acid content and ultrastructure in barley leaves vs. dose.

The effect of fast neutrons on the ultrastructure and nucleic acid content of leaves of barley seedlings was studied. Irradiation led to chloroplast degeneration. The walls of the cells containing degenerated plastides were abnormally thickened. Irradiation reduced the water content of the leaves. Variations in the RNA and DNA content of the leaves, expressed on a dry weight basis, could not be written as a simple function of the dose. Their content have a minimum at the semi-lethal dose.

Pigment composition and plastid structure in leaves of carotenoid mutants of maize.

In monogenic, recessive chloroplast mutants of maize which contain chlorophylls, and lycopene or χ-carotene but no normal carotenoids, great variability in the size of plastids was associated with a number of ultrastructural abnormalities. In the mutant accumulating lycopene some plastids contain dense bundles of lamellae, whereas the chloroplasts of the χ-carotene mutant show poor thylakoid development. Neither of the mutants was able to form normal grana.A comparison of chlorophyll/carotenoid ratios in different chloroplast fractions of normal and mutant leaves showed that plastids of small size and delicate structure contain relatively less chlorophyll than fully differentiated chloroplasts.