Metabolic Activities of Akinetes of the Cyanobacterium Anabaena doliolum: Oxygen Exchange, Photosynthetic Pigments and Enzymes of Nitrogen Metabolism

1988

New Phytologist

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SUMMARYThe energy requirements of akinete germination in A. doliolum were met initially from aerobic oxidation of endogenously stored carbon reserve. 'Phe germination of non-photosynthetic akinetes commenced in light with new protein synthesis followed by tbe simultaneous development of oxygenic photosynthesis, nitrate reductase activity, glutamine synthetase activity and aspartate dehydrogenase (AsDH) activity by 24 h and heterocyst formation and nitrogenase activity by 60 h. Glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GP'P) activities were present in mature akinetes and only GPT activity increased during akinete germination. The simultaneous appearance during the course of germination of oxygenic photosynthesis, nitrate reductase activity and glutamine synthetase activity much before that of N^ fixation, implies that oxygenic photosynthesis is more closely associated developmentally with carbon dioxide and nitrate assimilation than witb N2 assimilation. The activities of the transaminases (GOT and GPT) during the initial stages of germination suggest a significant role for these enzymes in amino-acid metabolism associated with germination. The appearance of nitrate reductase activity under N.j-fixing conditions, in the absence of nitrate, suggests that the nitrate assimilating enzyme is not nitrate inducible.

Section: Metabolic Changes Associated With Germination and Germling Gmentioning

confidence: 99%

“…Akinetes of A. dolioum lack the activities of nitrogenase and enzymes of inorganic nitrogen metabolism (Rao et at., 1984). Since the akinetes nevertheless, germinate in nitrogen-free medium we investigated the sequence of appearance of these enzymes.…”

Section: Metabolic Changes Associated With Germination and Germling Gmentioning

confidence: 99%

Metabolic changes associated with akinete germination in the cyanobacterium Anabaena doliolum

Rao

1988

New Phytologist

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“…The akinetes were yellow and the visual change in the colour of the cultures from blue-green to brown greatly facilitated the recognition and handling of populations of mature akinetes. The akinetes had a respiration rate of 34 9-37-6 nmol O^ uptake mg"' protein min"' in comparison with 85.8-87.2 nmol O.^ uptake mg ' protein min ' in whole heterocystous filaments, indicating a lower rate of respiration as found in akinetes of Nostoc PCC 7524 (Chauvat et al, 1982) and Anabaena doliolum (Rao . "/ al., 1984).The akinetes showed no photosynthetic O^ evolution although whole filaments had a rate of 374 to 377 nmol Oj evolved mg' protein min"'.…”

Section: C/n Ratiosmentioning

confidence: 88%

“…Anabaena doliolunt Bharadwaja is another with akinetes which are non-photosynthetic and lack the activities of the enzymes responsible for the assimilation of inorganic nitrogen (Rao, Rai & Singh, 1984).…”

Section: Introductionmentioning

confidence: 99%

Metabolic characteristics of akinetes of the cyanobacterium Fischerella muscicola

Kashyap

1988

New Phytologist

S U M M A R YMature akinetes of Fischerella rrniscicola (Thuret) Com. arc shown to have a low rate of respiration and to lack photosvnthetic pigments, photosynthetic Oj-evolving activity and the activities of the primary enzymes of inorganic nitrogen assimilation. The C/N ratio steadily increased during akinete differentiation and it is suggested that this increase results hecause, during akinete development, the loss of the activities of nitrogenase and glutamine synthetase precedes the loss of CO, fixation.

“…Photosynthetic O 2 evolution was measured using CLARK type Oxygen Electrode (Hansatech Instrument Ltd, England) as described by RAO et al (1984). N 2 -fixing abilities of test cyanobacterial strains under herbicides stress were determined Gas Chromatographically (CIC, India) by acetylene reduction assay (ARA) following the method of STEWART et al (1967).…”

Section: Determination Of Growth Photosynthesis and Nitrogenase Actimentioning

confidence: 99%

Screening and selection of most potent diazotrophic cyanobacterial isolate exhibiting natural tolerance to rice field herbicides for exploitation as biofertilizer

Datta²

2006

J. Basic Microbiol.

Periodic applications of heavy dosages of herbicides in modern rice-agriculture are a necessary evil for obtaining high crop productivity. Such herbicides are not only detrimental to weeds but biofertilizer strains of diazotrophic cyanobacteria also. It is therefore, essential to screen and select such biofertilizer strains of diazotrophic cyanobacteria exhibiting natural tolerance to common rice-field herbicides that can be further improved by mutational techniques to make biofertilizer technology a viable one. Therefore, efforts have been made to screen five dominant diazotrophic cyanobacterial forms e.g. filamentous heterocystous Nostoc punctiforme , Nostoc calcicola , Anabaena variabilis and unicellular Gloeocapsa sp. and Aphanocapsa sp. along with standard laboratory strain Nostoc muscorum ISU against increasing concentrations (0-100 mg l(-1) of four commercial grade common rice-field herbicides i.e. Arozin, Butachlor, Alachlor and 2,4-D under diazotrophic growth conditions. The lethal and IGC(50) concentrations for all four herbicides tested were found highest for A. variabilis as compared to other test cyanobacteria. The lowest reduction in chlorophyll a content, photosynthetic oxygen evolution, and N(2)-fixation was found in A. variabilis as compared to other rice field isolates and standard laboratory strain N. muscorum ISU. On the basis of prolong survival potential and lowest reductions in vital metabolic activities tested at IGC(50) concentration of four herbicides, it is concluded that A. variabilis is the most potent and promising cyanobacterial isolate as compared with other forms. This could be further improved by mutational techniques for exploitation as most potential and viable biofertilizer strain.