Heterocyst Frequency Research Articles

The heterocysts of blue-green algae. 3. Differentiation and nitrogenase activity.

The course of heterocyst development in Anabacna cylindrica was studied in relation to the ability to fix nitrogen. When non-differentiated filaments, grown in the presence of ammonium-N, were transferred into a medium free from combined nitrogen and incubated under photosynthetic conditions, the cellular C:N ratio increased from 4.5:1 to 8:1 before the percentage heterocyst frequency and nitrogenase activity reached a steady value. The initial stages of differentiation were observed 24 h after transfer into nitrogen-free medium, but nitrogenase activity was only detected when the formation of the first heterocysts was completed. The transformation of a vegetative cell into a heterocyst is characterized by the dissolution of storage granules, the deposition of a multilayered envelope, the breakdown of photosynthetic thylakoids and the formation of new membraneous structures. The latter appear to develop by the coalescence of small newly formed vesicles arising in regions of pre-existing thylakoids. The course of heterocyst development was paralleled by that of nitrogenase activity both under aerobic and anaerobic conditions. Anaerobic incubation enhanced heterocyst production as well as nitrogenase activity. The results suggest that nitrogenase synthesis in Anabaena cylindrica is associated with heterocyst formation and that the primary factor which may regulate both processes is the cellular C:N balance of the alga.

THE FREQUENCY OF HETEROCYSTS IN THE NOSTOC PHYCOBIONT OF THE LICHEN PELTIGERA CANINA WILLD.

SummaryA reliable estimate of 3.27% for the frequency of heterocysts in the cell population of the Nostoc phycobiont present in the thallus of the lichen Peltigera canina has been obtained by electron microscopy at low magnification.

Effects of chemicals on Fischerella muscicola (Thuret) Gom.

Fischerella muscicola (Thuret) Gom. was isolated in axenic culture, from the roof of a building. Effects of the incorporation of manganous chloride, caffeine, lanthanum acetate, maleic hydrazide, coumarin, thioglycollic acid, colchicine, and uranyl nitrate in the culture medium on the alga was investigated. The sublethal and lethal concentrations of chemicals were manganous chloride 5.0 mM and 7.5 mM; caffeine 5.0 mM and 10.0 mM; lanthanum acetate 0.7 mM and 1.5 mM; maleic hydrazide 2.0 mM and 4.0 mM; coumarin 1.4 mM; thioglycollic acid 1.0 mM; colchicine 10.0 mM; and uranyl nitrate 0.5 mM and 1.0 mM. The sublethal concentrations thus determined were higher than those found in bacteria.Among the effects, the killing of a few cells, lag in division of cells, cell enlargement or elongation, and formation of irregular clusters of cells were temporary in nature. On the other hand, the changes in pigment composition, vacuolization, production of gas vacuoles, increase in frequency of heterocysts, suppression of akinete formation, and formation of uniseriate prostrate branches were permanent.

The Relation of Acetylene Reduction to Heterocyst Frequency in Blue-Green Algae

The variation of acetylene reduction activity and heterocyst frequency with culture age, was studied in five species of blue-green algae. The heterocyst frequency varied between 2.5 to 12.3 per cent of total cells; and the acetylene reduction activity varied 2.0-fold (average). It is suggested that an estimate of the nitrogen fixation rates in blue-green algae may be made by in situ heterocyst counts and acetylene reduction measurements.

溜池における<i>Anabaena</i>の消長と環境条件との関係

The succession of a molecular nitrogen fixing blue-green alga, Anabaena was investigated in a farm pond where chemical fertilizers applied in Nagano Prefecture during the years of 1954 to 1956. The results were obtained as follows: 1) Maintenance of the algal blooming and acceleration of their growth rate were not found to be affected by the application of phosphorus fertilizer. The phenomenon was interpreted that the assimilable carbon played possibly a role of limiting factor. 2) “Heterocyst frequency” proposed by FOGG (1953) showed the minimum value of 2 to 3% when the growth of Anabaena had attained the maximum, suggesting that their maximum growth might be determined by the estimation of the value of heterocyst frequency. The chemical fertilization was found to have affected more on the heterocyst formation than on the resting spore formation. It seemed reasonable to assume, therefore, that in the course of the algal growing the former plays role different from the latter. 3) In three-year period of the study A. Viguieri was determined dominant species in the pond water especially in June. In 1956, with nearly complete control of water plant growth affected by the stocking of grass-carp, other two species of algae A. contorta (in July) and A. flos-aquae (in August) were also detected dominant. 4) The maximum yield of Anabaena was suppressed by the growth of water plants in the pond water, which, however, did not effect on the growth rate of the former.