Blue-green Alga Anabaena Doliolum Research Articles

Methylamine Regulation of Heterocyst and Nitrogenase in a Methylamine Resistant Blue-green Alga Anabaena doliolum

The ammonium analog «methylamine» inhibits the growth, nitrogenase activity, photosynthetic ATP pool and glutamine synthetase activity of the parental Anabaena doliolum . MA-caused inhibition of growth, nitrogenase activity and photosynthetic ATP pool, all become resistant to MA inhibition in the methylamine resistant mutant of A. doliolum . The N 2 growth and nitrogenase activity of the MA R strain is approximately half of that shown by the parent strain. The growing heterocystous N 2 -fixing cultures of the MA R strain in N 2 medium become nonheterocystous and nonfixer during growth in MA containing N 2 medium, thus suggesting metabolic utilization of MA like a fixed nitrogen source as a mechanism of resistance of MA R strain against inhibitory action of MA on growth, acetylene reducing activity and photosynthetic ATP pool. The MA grown culture of MA R strain shows higher ratio of glutamine synthetase biosynthetic to transferase activity than its MA free N 2 grown cultures, apparently suggesting the involvement of GS in the metabolism of the ammonium analog like a fixed nitrogen source.

Inhibitory Effects of Rice-field Herbicide Machete on Anabaena doliolum Bharadwaja and Protection by Nitrogen Sources

Summary Machete [2-chloro-2′,6′-diethyl-N-(butoxymethyl) acetanilide], a rice field herbicide, is toxic to the nitrogen fixing blue-green alga Anabaena doliolum. While low concentrations (0.05 μg · ml-1) had stimulatory effects, algal growth was completely inhibited at 20 μg · ml-1machete. Sublethal concentration (5.0 μg · ml-1) of the herbicide resulted in the decline of protein and phycobilin levels with no apparent effect on chlorophyll a, carotenoids carbohydrate, DNA and RNA. The herbicide inhibited heterocyst differentiation and nitrogen fixation. In contrast to vegetative cells, spores were more resistant to the herbicide. Since toxicity of the herbicide could be reversed by inorganic nitrogen sources (nitrate, nitrite and ammonium), it is suggested that nitrogen fixation was sensitive to the herbicide.

Developmental mutants of Anabaena doliolum defective in repair of UV-damage.

Nitrosoguanidine induced ‘blue’ pigment mutants of the blue-green alga Anabaena doliolum were isolated. The blue-mutants on further characterization were grouped into three developmental phenotypes — (i) those forming doli-form blue-spores of heterogenous size i.e., Ad 011, (ii) those forming spheroidal cells in the stationary phase, some of which behave like spores on transfer to fresh medium i.e., Ad 012, and (iii) those showing no sporulation and conditionally producing abnormal cells in the presence of combined nitrogen only i.e., Ad 007. The former two classes of mutants showed the formation of abnormal cells irrespective of the presence or absence of combined nitrogen sources in the medium. The formation of abnormal cells in the filaments of the above mutants were distinguished by their larger size and irregular mode of division leading to true-branch formation. The comparative characterization of these mutant strains with the parental one showed sluggish growth, increased UV-sensitivity, almost unchanged photorepair capacity, a marked change in the pigment composition and relative resistance to nitrosoguanidine. Irregular cell division in both space and time in the mutant strains and their increased sensitivity to ultraviolet irradiation indicate the possible involvement of dark repair system in maintaining the precision of cell cycle in this alga.

Effect of certain herbicides on survival, growth, and nitrogen fixation of blue-green alga Anabaena doliolum Bharadwaja.

Growth and fixation of nitrogen were retarded in Anabaena doliolum when grown on elemental nitrogen in presence of four different herbicides. The alga was found to be intolerant to these chemicals under nitrogen fixing conditions even in low concentrations. An inhibition of photosynthesis has been regarded as the main basis of herbicidal activity besides other interactions.

Intergeneric transfer of streptomycin-resistance marker between two blue-green algae

Intergeneric transfer of streptomycin-resistance marker from a unicellular blue-green algaAnacystis nidulans to a filamentous blue-green algaAnabaena doliolum was demonstrated. Mutants ofA. nidulans resistant to streptomycin, occurring spontaneously or mutagenically-induced could be isolated easily. Naturally occurring streptomycin-resistant mutants ofA. doliolum could not be detected. Attempts at isolating such mutants either in nitrogen-free medium or in nitrate containing medium were unsuccessful. However, a streptomycin-resistant strain (recombinant) ofA. doliolum could be isolated in a mixed culture of streptomycin-sensitiveA. doliolum and streptomycin-resistantA. nidulans.

Division of heterocysts in the blue-green alga Anabaena doliolum Bharadwaja.

Division of heterocysts in the blue-green alga Anabaena doliolum Bharadwaja.

A Mutational Study of the Nitrogen-fixing Blue-Green Alga Anabaena doliolum

A heterocystous, non-nitrogen-fixing mutant of the nitrogen-fixing blue-green alga Anabaena doliolum has been isolated following treatment with nitrosoguanidine and UV radiation. Some reversible variations in the habit and morphology of the alga were induced following its treatment with nitrosoguanidine.

Physiology of heterocyst production in the blue-gree alga Anabaena doliolum. I. Nitrate and light controls.

In the blue-green alga Anabaena doliolum heterocyst differentiation is sequential and independent of vegetative growth. Its control is photosynthetic in nature. The nature of growth curves obtained in nitrate and nitrogen-free media indicates that the heterocyst regulates vegetative growth but has no role in sporulation. The formation of the first heterocyst is determined at a certain stage during the development of a 2-celled germling into a 4-celled filament.

The effect of caffeine and light on killing of the blue-green alga Anabaena doliolum by ultraviolet radiation.

Pretreatment of spores of the blue-green alga Anabaena doliolum with caffeine is antagonistic to UV lethality and posttreatment with caffeine is synergistic to UV lethality and mutagenicity. The results of photoreactivation experiments suggest that photoreactivation is independent of photosynthesis in blue-green algae.

Pigment variations in ultraviolet-treated strains of the blue-green alga Anabaena doliolum.

Two kinds of cultures were raised from clones of Anabaena doliolum surviving on selective medium following exposure of spores to ultraviolet radiation. The pigments of these cultures have been characterized with respect to those of controls.

Inactivation and killing of the blue-green alga Anabaena doliolum grown on ultraviolet-irradiated culture medium

The spores of Anabaena doliolum were grown on UV-irradiated culture medium. The results obtained indicate that the irradiated medium causes inactivation, reduction in the frequency of sporulation and increased resistance to antibiotics in this alga. Prolonged storage of the irradiated medium and its exposure to white light immediately after irradiation rendered it non-toxic. It is concluded that as a result of irradiation of the culture medium some toxic agent is produced which might be responsible for the effects observed.

Genetic control of sporulation in the blue-green alga Anabaena doliolum Bharadwaja

Two genetically distinct, non-sporulating mutant strains of Anabaena doliolum were isolated following exposure of the alga to ultraviolet radiation. Among the progeny of a cross between the two non-sporulating strains, some filaments were able to sporulate. The spores of such filaments were of two types. Type 1 upon germination produced the parental phenotype, type 2 gave rise to wild phenotype. This suggests the involvement of heterozygosity in genetic recombination in A. doliolum. The results further indicate that the formation of spores in this alga is under the control of more than one genetic determinant, and that nuclear segregation occurs during sporulation.