Isolation and taxonomy of the blue-green algae (Cyanobacteria), Nostoc and Anabaena in Kerala State, India
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Blue-green algae (also called cyanobacteria) are ubiquitous, pristine and pioneer photosynthetic microorganisms. Many species of cyanobacteria are capable of fixing atmospheric nitrogen and such species in wet soils are simultaneously augmenting the fertility of the soil, acting as natural bio-fertilizers. Nostoc and Anabaena are the two important genera of heterocystous cyanobacteria capable of contributing nitrogen to soil, especially in paddy fields. The major objectives of the investigation included survey, collection, isolation and pure culture of nitrogen-fixing species of Cyanobacteria in the soils of Kerala state, India. Altogether, pure cultures of 12 species of Nostoc and 5 species of Anabaena are prepared.Keywords:
Nostoc
Abstract Photoautotrophic cyanobacteria often confront hydrogen peroxide (H2O2), a reactive oxygen species potentially toxic to cells when present in sufficiently high concentrations. In this study, H2O2 tolerance ability of filamentous cyanobacteria Nostoc punctiforme ATCC 29133 (Nostoc 29133) and Anabaena sp. PCC 7120 (Anabaena 7120) was investigated. Nostoc 29133 was better able to tolerate H2O2-induced inhibition of chlorophyll a and photosystem II performance, as compared to Anabaena 7120. The intracellular hydroperoxide level (indicator of oxidative status) also did not exhibit as much a rise in Nostoc 29133, as it did in Anabaena 7120 after H2O2 treatment. Accordingly, Nostoc 29133 showed higher intrinsic constitutive catalase activity than Anabaena 7120 indicating that the superior tolerance of Nostoc 29133 stems from its higher ability to decompose H2O2. It is suggested that difference in H2O2 tolerance between closely related filamentous cyanobacteria, as is borne out by this study, may be taken into account for judicious selection and effective use of strains in biotechnology.
Nostoc
Anabaena variabilis
Heterocyst
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Heterocyst
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Heterocyst
Nostoc
Anabaena variabilis
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Blue-green algae (also called cyanobacteria) are ubiquitous, pristine and pioneer photosynthetic microorganisms. Many species of cyanobacteria are capable of fixing atmospheric nitrogen and such species in wet soils are simultaneously augmenting the fertility of the soil, acting as natural bio-fertilizers. Nostoc and Anabaena are the two important genera of heterocystous cyanobacteria capable of contributing nitrogen to soil, especially in paddy fields. The major objectives of the investigation included survey, collection, isolation and pure culture of nitrogen-fixing species of Cyanobacteria in the soils of Kerala state, India. Altogether, pure cultures of 12 species of Nostoc and 5 species of Anabaena are prepared.
Nostoc
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Heterocyst
Nostoc
Phycobiliprotein
Anabaena variabilis
Hexose
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Isolation and characterization of cyanobacteria from extreme environment is important in identifying novel molecules and understanding the mechanisms underlying the tolerance. Therefore in the present study an attempt was made to isolate, identify and characterize cyanobacteria from Runn of Kutch experiencing high levels of salinity. On the basis of microscopic, morphological and cultural characteristics the identified cyanobacterial strains included Anabaena, Nostoc, Westielliopsis, Phormidiumand Synechocystis. Further analysis on the basis of 16S r DNA sequence and BLAST analysis confirmed their identity. Among the ten identified strains, seven strains such as belonging to Anabaena, Phormidium, Nostoc and Westielliopsis showed the presence of mycosporine like amino acids. Growth, cellular constituents and parameters of nitrogen assimilation in these strains were studied and showed significant differences. The present investigation helped in the identification of cyanobacterial strains producing mycosporine like amino acids which are novel compounds involved in stress tolerance.
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Synechocystis
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Summary Various species of cyanobacteria, diatoms and dinoflagellates are capable of synthesizing the non‐proteinogenic neurotoxic amino acid β‐N‐methylamino‐L‐alanine (BMAA), which is known to be a causative agent of human neurodegeneration. Similar to most cyanotoxins, the biological and ecological functions of BMAA in cyanobacteria are unknown. In this study, we show for the first time that BMAA, in micromolar amounts, inhibits the formation of heterocysts (specialized nitrogen‐fixing cells) in heterocystous, diazotrophic cyanobacteria [ Anabaena sp. PCC 7120, Nostoc punctiforme PCC 73102 (ATCC 29133), Nostoc sp. strain 8963] under conditions of nitrogen starvation. The inhibitory effect of BMAA is abolished by the addition of glutamate. To understand the genetic reason for the observed phenomenon, we used qPCR to study the expression of key genes involved in cell differentiation and nitrogen metabolism in the model cyanobacterium Anabaena sp. PCC 7120. We observed that in the presence of BMAA, Anabaena sp. PCC 7120 does not express two essential genes associated with heterocyst differentiation, namely, hetR and hepA . We also found that addition of BMAA to cyanobacterial cultures with mature heterocysts inhibits nifH gene expression and nitrogenase activity.
Cyanotoxin
Heterocyst
Alanine
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Eleven species of nitrogen-fixing cyanobacteria belonging to six genera (Cylindrospermum, Anabaena, Nostoc, Calothrix, Scytonema, and Westiellopsis) tolerate different concentrations of NaCl (from 0.05 to 0.35 M). Wide variation in the chlorophyll (Chl) a content of the species of the same genus and between genera in presence of NaCl was observed. The least tolerant (Cylindrospermum sp., Cy 6), the maximum tolerant (Westiellopsis sp., We 1), and the intermediate tolerant (Westiellopsis sp., We 6) species of cyanobacteria were selected, and their response to various concentrations of NaCl (growth, nitrogen-fixing capacity, and production of extracellular substances) was studied. Nitrogen fixing capacity of both the We 1 and We 6 was greatly impaired in comparison to the decrease in their Chl a content in the NaCl containing media. Cellular and extracellular saccharide and extracellular amino acid contents of the cyanobacteria species in the NaCl supplemented cultures were increased suggesting that presence of saccharides and amino acids enabled the cyanobacterial species to thrive under salt stress. Further, the We 1 did not adapt to the salt whereas Cy 6 showed adaptation to low concentrations of NaCl suggesting that the species which tolerate high concentrations of the salt may not possess the ability to adapt to NaCl.
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Heterocyst
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