Distribution of nitrogen-fixing cyanobacteria (Nostocaceae) during rice cultivation in fertilized and unfertilized paddy fields

This study describes the development of nitrogen-fixing cyanobacteria (Nostocaceae) during different stages of rice seedlings plantation in fertilized and unfertilized paddy fields in north Bihar, India. A heterogeneous population of cyanobacteria was randomly harvested around day 20, 40 and 60 of rice seedlings plantation, and the diversity was analyzed. Thirtytwo species (7 genera) were identified from unfertilized fields, of which Anabaena was represented by 12 species, Anabaenopsis and Aulosira by 3 each, Cylindrospermum by 4, Nostoc by 8 and Aphanizomenon and Nodularia by 1 species each. However, fertilized fields contained only 25 species (7 genera), of which 8 each belonged to Nostoc and Anabaena , 3 to Cylindrospermum , 2 to each Anabaenopsis and Aulosira and 1 to each Aphanizomenon and Nodularia . Although Nostoc and Anabaena were dominant in both fertilized and unfertilized paddy fields, a marked decrease in nitrogen-fixing cyanobacteria was recorded from fertilized fields. In both treatments, the diversity of nitrogen-fixing cyanobacteria was at a maximum around day 60 after seedling plantation. The current study concludes that there is a negative effect of nitrogenous fertilizers on the development of heterocystous cyanobacteria in rice fields. It is proposed that early appearing efficient nitrogen-fixers should be used as nitrogen fertilizers in the management for better establishment and exploitation of heterocystous cyanobacteria for sustainable agricultural practices.     

Pigment analysis and ammonia excretion in herbicide tolerant cyanobacteria

Isolation of cyanobacteria was attempted from herbicide applied rice soils. The predominant genera were Westiellopsis followed by Anabaena, Nostoc and Oscillatoria. The herbicide tolerance was further tested by growing the cyanobacterial cultures in BG-11 medium supplemented with varying concentrations of the commonly used rice herbicide, viz butachlor under in vitro condition. The chlorophyll-a, phycobiliproteins and ammonia excretion were assessed at periodic intervals. Westiellopsis showed the maximum tolerance followed by Anabaena, Nostoc and Oscillatoria.     

Molecular detection of uncultured cyanobacteria and aminotransferase domains for cyanotoxin production in sediments of different Kenyan lakes

PCR-based denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments was used to identify the cyanobacterial phylotypes in sediments and plankton of saline–alkaline and freshwater lakes of Kenya. The detection of the aminotransferase domain located on modules mcyE and ndaF using specific molecular markers confirmed the presence of potential toxin-producing cyanobacteria. The eight nucleotide sequences obtained from DGGE bands were placed in three divergent cyanobacterial clusters. Five nucleotide sequences were close to members of the genera Anabaenopsis and Umezakia ( Nostocales ), two sequences fell in the cluster with Arthrospira sp. ( Oscillatoriales ) and one sequence was related to Chroococcidiopsis sp. ( Pleurocapsales ). The presence of the latter taxon was demonstrated de novo in the investigated lakes. All nine attained nucleotide sequences of the aminotransferase region belonged to the mcyE module. Five sequences of the aminotransferase domain were included in the cluster having the nucleotide sequence of Anabaena sp. but showed a separate lineage. Other four aminotransferases were placed in the cluster represented by nucleotide sequence of Microcystis aeruginosa . To our knowledge, this is the first report on molecular detection of cyanobacterial phylotypes in sediments of African lakes and aminotransferase domains for cyanotoxin production from sediment samples in general.     

A rapid and cost-effective method of genomic DNA isolation from cyanobacterial culture,mat and soil suitable for genomic fingerprinting and community analysis

This study presents a phenol and lysozyme free protocol for genomic DNA isolation of cyanobacteria from culture, mats and soil. For an efficient and pure DNA isolation from cyanobacteria having tough cell wall, extra steps of glass beading and Sepharose 4B purification were added. The modified method gave a higher yield of DNA than the phenol: chloroform extraction method. Four parameters selected for purity testing of the isolated DNA were: (i) restriction digestion with Hind III, (ii) randomly amplified polymorphic DNA-PCR of axenic culture of cyanobacteria to assess phylogenetic relatedness, (iii) denaturing gradient gel electrophoretic (DGGE) analysis of cyanobacterial mat and soil to ascertain the applicability of the isolated DNA for community analysis, and (iv) sequencing of partial 16S rDNA of Hapalosiphon intricatus BHULCR1, Anabaena doliolum LCR1, Anabaena oryzae LCR2, Aulosira fertilissima LCR4, and Tolypothrix tenuis LCR7 and BLAST analysis to confirm their cyanobacterial identity. Data generated from above analyses lead us to conclude that the modified method in question is rapid, cost effective, health and time conscious and promising for genetic fingerprinting and community analysis of cyanobacteria from diverse habitats.     

Comparison of light and dark nitrogenase activity in selected soil cyanobacteria

Frequency of heterocytes and nitrogenase activity (NA) under light and dark cultivation conditions was determined in 12 cyanobacterial strains isolated from various soil habitats. In spite of a high variability, significant differences in NA among the strains were found in response of light and dark cultivation. Relatively high NA (9.9-15.3 micromol/h C2H4 per g fresh mass) under light conditions and basal NA after 12 h of dark cultivation were detected in Anabaena, Nodularia, Tolypothrix, and 1 of Cylindrospermum strains. On the other hand, significantly lower NA (0.76-5.4 micromol/h C2H4 per g fresh mass) was found under light conditions in Trichormus, Nostoc and another Cylindrospermum strain; the activity completely disappeared after 12 h of dark cultivation. NA values were not directly related to the frequency of the heterocytes. The total NA of cyanobacterial colony was found to be probably independent of the number and/or position of heterocytes. Remarkable differences in NA between strains isolated from cultivated fields and strains originating from natural or non-cultivated soils were found.     

Molecular characterization of endolithic cyanobacteria inhabiting exposed dolomite in central Switzerland

The phototrophic microbial community inhabiting exposed dolomite in the alpine Piora Valley (Switzerland) forms a distinct endolithic bilayer that features adjacent red dolomite (exterior) and green dolomite (interior) layers that are c. 0.5-1 mm below the rock surface. Characterization of the community, with an emphasis on cyanobacteria, was conducted with culture-dependent and -independent approaches. Direct microscopy of green dolomite revealed four distinct morphotypes consistent with Chlorophyta genera Chlorella and Stichococcus and the Cyanobacterial genera Nostoc and Calothrix, whereas only Stichococcus and Nostoc were observed in the red dolomite. Enrichment in BG-11 media resulted in the growth of Chlorella and Stichococcus. Denaturing gradient gel electrophoresis (DGGE) analysis of DNA extracted from the enrichment revealed two dominant phylotypes with sequence similarity to Chlorella osrokiniana chloroplast and the cyanobacteria genus Leptolyngbya. 16S rRNA gene-based DGGE analysis of DNA extracted directly from both layers indicated that although both layers harboured phylotypes most similar to the Cyanobacterial genera Nostoc, Chroococcidiopsis, and Microcoleus, and the Chlorophyte Stichococcus bacillaris, the two layers also harboured unique genera such as Scytonema, and Symploca (red, external layer of dolomite) and Chlorella (green, internal layer of dolomite). The unique community structure of each layer suggests a selection process directed by the pressures of the endolithic environment. We conclude that the overall composition of the phototrophic community closely resembles that of endolithic communities located in extreme habitats, suggesting that a cosmopolitan community inhabits this defined niche.     

Amino acid transport in taxonomically diverse cyanobacteria and identification of two genes encoding elements of a neutral amino acid permease putatively involved in recapture of leaked hydrophobic amino acids.

The activities of uptake of thirteen 14C-labeled amino acids were determined in nine cyanobacteria, including the unicellular strains Synechococcus sp. strain PCC 7942 and Synechocystis sp. strain PCC 6803; the filamentous strain Pseudanabaena sp. strain PCC 6903, and the filamentous, heterocyst-forming strains Anabaena sp. strains PCC 7120 and PCC 7937; Nostoc sp. strains PCC 7413 and PCC 7107; Calothrix sp. strain PCC 7601 (which is a mutant unable to develop heterocysts); and Fischerella muscicola UTEX 1829. Amino acid transport mutants, selected as mutants resistant to some amino acid analogs, were isolated from the Anabaena, Nostoc, Calothrix, and Pseudanabaena strains. All of the tested cyanobacteria bear at least a neutral amino acid transport system, and some strains also bear transport systems specific for basic or acidic amino acids. Two genes, natA and natB, encoding elements (conserved component, NatA, and periplasmic binding protein, NatB) of an ABC-type permease for neutral amino acids were identified by insertional mutagenesis of strain PCC 6803 open reading frames from the recently published genomic DNA sequence of this cyanobacterium. DNA sequences homologous to natA and natB from strain PCC 6803 were detected by hybridization in eight cyanobacterial strains tested. Mutants unable to transport neutral amino acids, including natA and natB insertional mutants, accumulated in the extracellular medium a set of amino acids that always included Ala, Val, Phe, Ile, and Leu. A general role for a cyanobacterial neutral amino acid permease in recapture of hydrophobic amino acids leaked from the cells is suggested.     

Associative cyanobacteria isolated from the roots of epiphytic orchids

Associative cyanobacteria were isolated from the rhizoplane and velamen of the aerial roots of the epiphytic orchids Acampe papillosa, Phalaenopsis amabilis, and Dendrobium moschatum and from the substrate roots of Acampe papillosa and Dendrobium moschatum. Cyanobacteria were isolated on complete and nitrogen-free variants of BG-11 medium. On all media and in all samples, cyanobacteria of the genus Nostoc predominated. Nostoc, Anabaena, and Calothrix were isolated from the surface of the A. papillosa aerial roots, whereas the isolates from the substrate roots were Nostoc, Oscillatoria, and representatives of the LPP-group (Lyngbia, Phormidium, and Plectonema, incapable of nitrogen fixation). On the D. moschatum substrate roots, Nostoc and LPP-group representatives were also found, as well as Fischerella. On the aerial roots of P. amabilis and D. phalaenopsis grown in a greenhouse simulating the climate of moist tropical forest, cyanobacteria were represented by Nostoc, LPP-group, and Scytonema in the D. phalaenopsis and by Nostoc, Scytonema, Calothrix, Spirulina, Oscillatoria, and the LPP-group in P. amabilis. For D. moschatum, the spectra of cyanobacteria populating the substrate root zhizophane and the substrate (pine bark) were compared. In the parenchyma of the aerial roots of P. amabilis, fungal hyphae and/or their half-degraded remains were detected, which testifies to the presence of mycorrhizal fungi this plant. This phenomenon is attributed to the presence of a sheath formed by cyanobacteria and serving as a substrate for fungi.     

Nitrogenase activity of blue-green algae on seasonally flooded soils in Bangladesh

Blue-green algal communities formed an extensive cover on soils at five deepwater rice-growing locations in Bangladesh during the month before the arrival of floodwater. The principal taxa wereAnabaena, Cylindrospermum, Lyngbya, Microcoleus, Nostoc, Prophyrosiphon notarisii, Scytonema mirabile andTolypothrix byssoidea. One of two locations studied after the floodwaters had receded also had an extensive cover, mainlyScytonema mirabile. Nitrogenase activity assayed at mid-day was from one to three orders of magnitude higher per unit area of community than bare soil. Nostoc showed higher activity than Tolypothrix, whether expressed per unit area or biomass. Whole field estimates of N₂ fixed by blue-green algal communities during the pre-flood period ranged from 1.0 to 10.2 kg N ha^–1. Much of this is probably not recycled until floodwaters cover the fields. However N₂ fixed after floodwaters have receded is probably recycled rapidly due to ploughing.     

Taxonomic studies of some cultured strains of Cyanobacteria (Nostocales) isolated from the Yenisei River basin

Twenty-one strains of cyanobacteria representing the genera Anabaena, Cylindrospermum, Mojavia, Nostoc, Trichormus, and Wollea (Nostocales, Cyanobacteria) isolated from algocenoses of the Yenisei River basin (eastern Siberia, Russia) were taxonomically studied. New taxa characteristic of this region were discovered. The properties of pure cultures of Anabaena sedovii, A. zinserlingii,Cylindrospermum stagnale f. tortuosum, Nostoc kihlmani, Trichormus variabilis f. tenuis, and Wollea saccata have never been described before. The primary taxonomic features (the position of akinetes and heterocysts, the width of vegetative cells, akinetes and heterocysts, and the shape of terminal cells) of these cyanobacteria when cultured were shown to fit the diagnosis of the identified taxa.     

General distribution of the nitrogen control gene ntcA in cyanobacteria.

The ntcA gene from Synechococcus sp. strain PCC 7942 encodes a regulatory protein which is required for the expression of all of the genes known to be subject to repression by ammonium in that cyanobacterium. Homologs to ntcA have now been cloned by hybridization from the cyanobacteria Synechocystis sp. strain PCC 6803 and Anabaena sp. strain PCC 7120. Sequence analysis has shown that these ntcA genes would encode polypeptides strongly similar (77 to 79% identity) to the Synechococcus NtcA protein. Sequences hybridizing to ntcA have been detected in the genomes of nine other cyanobacteria that were tested, including strains of the genera Anabaena, Calothrix, Fischerella, Nostoc, Pseudoanabaena, Synechococcus, and Synechocystis.     

十四属蓝藻液泡的检查和分离

采用压片法,渗透冲击法和原生质球法,对14个属的不同蓝藻进行了液泡存在的检查和分离试验,每种蓝藻都检查到液泡,无一例外。其中鱼腥藻、念珠藻、项圈藻、席藻、简孢藻等都能形成液泡化原生质球,原生质球低渗破裂释放液泡,液泡得率极高,不同种的液泡都耐低渗。因此,本研究证明液泡在蓝藻中的存在是普遍的。     

Molecular typing and distribution of filamentous heterocystous cyanobacteria isolated from two distinctly located regions in North-Eastern India

The diversity of cyanobacteria in the North-Eastern region of India has not been studied except for a few sporadic and inconclusive reports. Loktak Lake is a huge reservoir for various kinds of organisms, including cyanobacteria. The present study describes the isolation and molecular diversity of 72 filamentous, heterocystous cyanobacterial strains isolated from samples collected from Loktak Lake, its adjoining rice fields and rice fields in Indian Council of Agricultural Research (ICAR) complex, Shillong, Meghalaya, India. The isolated strains belonged to the genera Anabaena, Nostoc, Calothrix, Cylindrospermum and Mastigocladus. The molecular analysis of isolates revealed the occurrence of certain strains being present in the sample collected from the rice fields falling in the catchment area of Loktak Lake, Manipur and rice fields in ICAR complex, Shillong, Meghalaya both. A polyphasic approach based on morphological features and PCR based molecular polymorphism revealed enormous level of molecular diversity. Out of three primers targeted regions used for determining genetic polymorphism, STRR1A produced best fingerprint profile of cyanobacterial strains. The morphological diversity of isolates was assured by light microscope whereas PCR based multiple fingerprint profile was used for molecular characterization. Molecular typing using short tandemly repeated repetitive STRR1A sequences as primer provided strain specific fingerprint profiles of the isolates.     

Phylogenetic and molecular clock inferences of cyanobacterial strains within Rivulariaceae from distant environments

Heterocyst-forming cyanobacteria are important players at both evolutionary and ecological scales, but to date it has been difficult to establish their phylogenetic affiliations. We present data from a phylogenetic and molecular clock analysis of heterocystous cyanobacteria within the family Rivulariaceae, including the genera Calothrix, Rivularia, Gloeotrichia and Tolypothrix. The strains were isolated from distant geographic regions including fresh and brackish water bodies, microbial mats from beach rock, microbialites, pebble beaches, plus PCC strains 7103 and 7504. Phylogenetic inferences (distance, likelihood and Bayesian) suggested the monophyly of genera Calothrix and Rivularia. Molecular clock estimates indicate that Calothrix and Rivularia originated ～1500 million years ago (MYA) ago and species date back to 400-300 MYA while Tolypothrix and Gloeotrichia are younger genera (600-400 MYA).     

Physiological and molecular diversity of feather moss associative N2-fixing cyanobacteria

Cyanobacteria colonizing the feather moss Pleurozium schreberi were isolated from moss samples collected in northern Sweden and subjected to physiological and molecular characterization. Morphological studies of isolated and moss-associated cyanobacteria were carried out by light microscopy. Molecular tools were used for cyanobacteria identification, and a reconstitution experiment of the association between non-associative mosses and cyanobacteria was conducted. The influence of temperature on N2 fixation in the different cyanobacterial isolates and the influence of light and temperature on N2-fixation rates in the moss were studied using the acetylene reduction assay. Two different cyanobacteria were effectively isolated from P. schreberi: Nostoc sp. and Calothrix sp. A third genus, Stigonema sp. was identified by microscopy, but could not be isolated. The Nostoc sp. was found to fix N2 at lower temperatures than Calothrix sp. Nostoc sp. and Stigonema sp. were the predominant cyanobacteria colonizing the moss. The attempt to reconstitute the association between the moss and cyanobacteria was successful. The two isolated genera of cyanobacteria in feather moss samples collected in northern Sweden differ in their temperature optima, which may have important ecological implications.     

Morphological variability in selected heterocystous cyanobacterial strains as a response to varied temperature, light intensity and medium composition

The effect of temperature, light and nutrient composition on morphological traits was determined in seven nostocacean cyanobacteria (Anabaena planctonica, A. sphaerica var. conoidea, A. spiroides, Aphanizomenon gracile, Nostoc sp., Scytonema sp., and Tolypothrix sp.). Their morphological variability was high but only some of the features showed changes reflecting varied growth conditions. The frequency of heterocyst occurrence decreased with increasing nitrogen concentration. Within the range studied, the effect of temperature on heterocyst frequency of Tolypothrix sp. and planktonic Anabaena strains could be fitted by a normal curve with a clear optimum while linear correlation was found in Aphanizomenon gracile. T-and S-type branching was observed in both Scytonema sp. and Tolypothrix sp. strains. T-type branching was found to be markedly dependent on nitrogen concentration. The abundance of necridic cells of Tolypothrix sp. increased linearly with temperature and light intensity. Regularity of trichome coiling of A. spiroides depended on culture medium, suggesting that nutrient composition may be the main controlling factor. In contrast, the effect of the experimental conditions on the dimensions of vegetative cells and heterocysts was weak. Their variability was markedly higher within each experimental treatment than between treatments.     

Acclimation of chlorophyll a and carotenoid levels to different irradiances in four freshwater cyanobacteria

This study investigated carotenoid and chlorophyll a (Chl-a) contents under two different growth irradiances in four freshwater cyanobacterial strains. We found an increased weight ratio of zeaxanthin to Chl-a after exposure to high irradiances over several days. Two out of four strains showed higher zeaxanthin amounts on a biomass basis as well. It appears that cyanobacteria enhance their carotenoid pool in response to high light conditions, as increased production of other carotenoids with photoprotective abilities has also been observed under high irradiance levels. Cyanobacteria do not possess the violaxanthin cycle, which enables a rapid reversible conversion from violaxanthin into zeaxanthin and functioning as a quencher of excessive energy, and elevated zeaxanthin concentrations could therefore be seen as an adaptive strategy against excess light energy. Some differences in the acclimation pattern were revealed between different cyanobacteria. Anabaena torulosa contained higher amounts of every carotenoid, while Nostoc sp. mainly increased zeaxanthin, and myxoxanthophyll. Anabaenopsis elenkinii produced exceptionally high amounts of myxoxanthophyll and beta-carotene under higher irradiances. Anabaena cylindrica generally showed less variation of carotenoids under different irradiances.     

Metabolites produced by cyanobacteria belonging to several species of the familyNostocaceae

This paper provides a comprehensive overview of metabolites, including lipids and lipid-like compounds, nitrogen metabolites, oligopeptides and amino acid derivatives, produced by cyanobacteria of the genera Anabaenopsis, Aphanizomenon, Aulosira, Cylindrospermopsis, Cylindrospermum, Nodularia, and Richelia of the family Nostocaceae.