Action of mutagenic chemicals on Anacystis nidulans. III. N-methyl-N'-nitro-N-nitrosoguanidine

The tolerance of the unicellular blue-green alga Anacystis nidulans to nitrosoguanidine increased from an initial level of 5 µg NTG/ml to 20 µg/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

Studies on sulphur-selenium antagonism in blue-green algae

Anacystis nidulans and Anabaena variabilis contain sufficient sulphur reserves to enable them to perform only one round of growth cycle in the non-sulphur growth medium. Sulphate, sulphite, l-methionine and d-methionine, each can act as a suitable sulphur source, but they differ in respect of their growth promoting action; sulphate uptake seems to be a light driven phenomenon and the sulphate metabolizing enzymes are inducible in nature. Methionine appears to act as a repressor of sulphate-metabolizing enzymes

Action of mutagenic chemicals on Anacystis nidulans. V. Diethyl sulphate

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

Effects of vanadium and tungsten on the nitrogen-fixing cyanobacterium Nostoc linckia

The effects of vanadium and tungsten on growth of the heterocystous cyanobacterium Nostoc linckia (Roth.) Born. and the activity of its nitrogenase and nitrate reductase were studied. While vanadate stimulated the growth of molybdate-limited cells and also their acetylene-reducing ability, it did not stimulate nitrate reductase activity. Tungstate inhibited growth in molybdate-limited cells and also their acetylene reducing and nitrate reductase activities. Acetylene reduction response of cells grown in a tungstate-containing medium indicated certain difference between the modes of action of vanadium and molybdenum. Tungstate caused a slight increase in heterocyst frequency both in nitrogen-fixing and nitrate-grown material. Cyanophycin granules and polyhedral bodies disappeared in molybdate-deficient cells in which thick deposition of polyglucan-like granules occurred throughout the breakdown of cytoplasm and the thylakoids

Cellular differentiation and nitrogenase activity in the cyanobacterium Anabaena

Nitrogenase activity at periods of differentiation of heterocysts and akinetes was assayed by the acetylene reduction technique. There was no nitrogenase activity in ammonium grown, non-heterocystous Anabaena sp.; the activity appeared only after a lag-phase of about 17 - 21 h after the ammonium-grown culture had been transferred to medium free of combined nitrogen. This activity started appearing as the proheterocysts were developing to mature heterocysts. Maximum nitrogenase activity was attained with exponential phase of culture and mature heterocysts. This activity gradually decreased with the differentiation of akinetes. Only insignificant nitrogenase activity was observed in old cultures in which most cells had matured into akinetes

The effect of maleic hydrazide on growth and mutation of a blue-green alga

Maleic hydrazide is mutagenic to the blue-green alga Anacystis nidulans at pH 5.0, producing mutations to streptomycin-resistance and penicillin-resistance, and is non-mutagenic at pH 8.0, promoting growth in low concentrations. The maleic hydrazide-induced increases in the levels of streptomycin- and penicillin-resistance are 1000 and 500 times respectively over the parental strain. The resistant strains can further mutate spontaneously to give rise to strains resistant to still higher concentrations of the antibiotic. Cultures growing with manganese are more sensitive to maleic hydrazide-induced inhibition of growth than are those growing without manganese. However, cultures of the alga in maleic hydrazide grown in the presence of two different concentrations of manganese differ in the extent of growth which is better in those with the higher manganese concentration than in those with the lower. These results suggest different modes of interaction between manganese and maleic hydrazide, controlled primarily by manganese concentration

Heterocyst division in two blue-green algae

The heterocysts of Camptylonema lahorense and Aulosira fertilissima have been observed to undergo division, as distinct from germination, either by the constriction of the heterocyst wall and protoplast or by the formation of a transverse furrow. A two-pored heterocyst divides in this way to form two one-pored heterocysts

Action of hydroxyurea on Anabaena variabilis

Low concentrations of hydroxyurea stimulated the growth of the blue-green alga Anabaena variabilis that had been pretreated with sublethal concentrations of chloramphenicol or of certain nucleic acid base analogues. When supplemented to the culture medium, hydroxyurea also counteracted the growth inhibitory effect of chloramphenicol on this organism. In contrast, when A. variabilis cells grown in the presence of hydroxyurea were subsequently treated with chloramphenicol, they were found to have become highly susceptible to the growth inhibitory effects of chloramphenicol. The growth of hydroxyurea pretreated cells in basal medium was attended by a lag that was shorter than that of untreated controls; on the other hand, when hydroxyurea pretreated cells were inoculated into chloramphenicol-supplemented medium, they exhibited a longer lag than that shown by untreated cells in chloramphenicol. The results obtained are discussed in terms of the probable effects of hydroxyurea and chloramphenicol on certain enzyme systems

Ultraviolet Radiation Cured Bio-Fibre Composites From Oil Palm Empty Fruit Bunch.

In this study, development of ultra-violet (UV) cured biofibre composites is reported. The composites were based on the pulp made from empty fruit bunch (EFB) as the reinforcing agent and unsaturated polyester as the matrix

Estimation of Radioprotective Effects of Garcinia Indica Methanol Extract in Swiss Albino Mice

The radio protective effectiveness of methanol extract of Garcinia indica against whole body gamma radiation was premeditated in Swiss albino mice. The oral administration of Garcinia indica extract at 800 mg / kg body weight / day for 15 consecutive days before whole body exposure to radiation was found to be effective with the LD50/30 values of 7.21 and 8.83 Gy for irradiation alone and Garcinia indica andirradiation group, respectively, giving a dose reduction factor of 1.42. This effect of Garcinia indica as the modulation of the radiation-induced decrease of reduced glutathione and the radiation-induced increase in lipid per oxidation assessed in the liver and the bloo