Cultures Of Anabaena Research Articles

Genomic Insights into Denitrifying Methane-Oxidizing Bacteria Gemmobacter fulva sp. Nov., Isolated from an Anabaena Culture.

The genus Gemmobacter grows phototrophically, aerobically, or anaerobically, and utilizes methylated amine. Here, we present two high-quality complete genomes of the strains con4 and con5T isolated from a culture of Anabaena. The strains possess sMMO (soluble methane monooxygenase)-oxidizing alkanes to carbon dioxide. Functional genes for methane-oxidation (prmAC, mimBD, adh, gfa, fdh) were identified. The genome of strain con5T contains nirB, nirK, nirQ, norB, norC, and norG genes involved in dissimilatory nitrate reduction. The presence of nitrite reductase gene (nirK) and the nitric-oxide reductase gene (norB) indicates that it could potentially use nitrite as an electron acceptor in anoxic environments. Taxonomic investigations were also performed on two strains through polyphasic methods, proposing two isolates as a novel species of the genus Gemmobacter. The findings obtained through the whole genome analyses provide genome-based evidence of complete oxidation of methane to carbon dioxide. This study provides a genetic blueprint of Gemmobacter fulva con5T and its biochemical characteristics, which help us to understand the evolutionary biology of the genus Gemmobacter.

Potential of the cyanobacteria Anabaena sp. and Dolichospermum sp. for being produced using wastewater or pig slurry: Validation using pilot-scale raceway reactors

Indoor trials using 0.3 L bubble columns were conducted to demonstrate the potential of two cyanobacterial strains, Anabaena sp. and Dolichospermum sp., for being produced using nutrients obtained from waste streams (wastewater or pig slurry). Filtered pig slurry diluted at a concentration of 5% (v/v) led to a biomass productivity comparable to that of the standard medium (0.72 ± 0.05 and 0.66 ± 0.09 g·L−1·day−1 for Anabaena sp. and Dolichospermum sp. respectively). When produced using wastewater, the productivity was around 0.40 g·L−1·day−1 for both strains. The process was up-scaled using a 1.04 m3 raceway reactor located outdoors and operated at a culture depth of 0.12 m. Dilution rates of 0.1–0.3 day−1 were evaluated, achieving maximum biomass productivities when operating at a dilution rate of 0.3 day−1: 20.9 and 28.0 g·m−2·day−1 for Anabaena sp. and Dolichospermum sp., respectively. The maximum total nitrogen (N-NH4+ plus N-NO3−) removal rates for Anabaena sp. and Dolichospermum sp. were 2471 and 3621 mg·m−2·day−1, achieved when operating at a dilution rate of 0.3 day−1. Nitrification and stripping contributed to the N-NH4+ removal. When operating at 0.3 day−1, maximum P-PO43− removal rates for cultures of Anabaena sp. and Dolichospermum sp. were 81.5 and 87.1 mg·m−2·day−1. Illumina sequencing results revealed that both strains dominated the prokaryotic community of both cultures with other notable eukaryotic and prokaryotic genus detected including human pathogens. However, annual studies are needed to assess the potential of producing biomass rich in these strains at large-scale outdoors.

Coexistence of Communicating and Noncommunicating Cells in the Filamentous Cyanobacterium Anabaena.

In filamentous heterocyst-forming (N2-fixing) cyanobacteria, septal junctions join adjacent cells, mediating intercellular communication, and are thought to traverse the septal peptidoglycan through nanopores. Fluorescence recovery after photobleaching (FRAP) analysis with the fluorescent marker calcein showed that cultures of Anabaena sp. strain PCC 7120 grown in the presence of combined nitrogen contained a substantial fraction of noncommunicating cells (58% and 80% of the tested vegetative cells in nitrate- and ammonium-grown cultures, respectively), whereas cultures induced for nitrogen fixation contained far fewer noncommunicating cells (16%). A single filament could have communicating and noncommunicating cells. These observations indicate that all (or most of) the septal junctions in a cell can be coordinately regulated and are coherent with the need for intercellular communication, especially under diazotrophic conditions. Consistently, intercellular exchange was observed to increase in response to N deprivation and to decrease rapidly in response to the presence of ammonium in the medium or to nitrate assimilation. Proteins involved in the formation of septal junctions have been identified in Anabaena and include SepJ, FraC, and FraD. Here, we reevaluated rates of intercellular transfer of calcein and the number of nanopores in mutants lacking these proteins and found a strong positive correlation between the two parameters only in cultures induced for nitrogen fixation. Thus, whereas the presence of a substantial number of noncommunicating cells appears to impair the correlation, data obtained in diazotrophic cultures support the idea that the nanopores are the structures that hold the septal junctions.IMPORTANCE Multicellularity is found in bacteria as well as in eukaryotes, and the filamentous heterocyst-forming (N2-fixing) cyanobacteria represent a simple and ancient paradigm of multicellular organisms. Multicellularity generally involves cell-cell adhesion and communication. The cells in the cyanobacterial filaments are joined by proteinaceous septal junctions that mediate molecular diffusion. The septal junctions traverse the septal peptidoglycan, which bears holes termed nanopores. Our results show that the septal junctions can be coordinately regulated in a cell and emphasize the relationship between septal junctions and nanopores to build intercellular communication structures, which are essential for the multicellular behavior of heterocyst-forming cyanobacteria.

Application of Three Cyanobacteria in Foods and Feeds Biotechnology: Phosphorus Affects.

Cyanobacteria grown under abiotic stress affect on some metabolites that used as promising for foods and feeds biotechnology. Thus, the objective of the study was to evaluate the 3 local cyanobacteria isolates for production of foods and feeds under various concentration of phosphorus. Cyanobacteria namely; Anabaena sp., Merismopedia tenuissima and Spirulina platensis were grown photoautotrophically in modified medium. The growth pattern in the medium containing various phosphorus concentrations were followed and harvested around 14 days. A decrease in phosphorus concentrations by 50% led to an increase in chlorophyll-a of M. tenuissima and S. platensis. The application of high concentration of phosphorus (+100%) to the culture of Anabaena sp. led to an increase in dry weight and growth rate by 0.382 mg mL-1 and 0.013 h-1, respectively. The deficiency of phosphorus concentrations led to a decrease in carbohydrate contents of Anabaena, Merismopedia and Spirulina with compared to the control culture. In general, the total lipid contents of Anabaena sp. and M. tenuissima were stimulated by phosphorus deficiency. The phosphorus-free media and increase in phosphorus concentration by 100% resulted in an increase in protein fractions such as soluble, insoluble, globulins, prolamines, glutelins and total protein content of Anabaena sp. The application of high concentration of phosphorus (+100%) to the culture of S. platensis led to an increase in total lipid contents in comparison to control. The highest phycobiliprotein contents of S. platensis were recorded at 50% phosphorus deficiency. Cyanobacteria has a soft cell wall that makes it especially easy to digest and is additionally full of live active enzymes which further enhances metabolism and the efficient intake of nutrients.

Molecular taxonomic evaluation of Anabaena and Nostoc strains from the Mosonmagyaróvár Algal Culture Collection

The taxonomy of genera Anabaena and Nostoc is very controversial. They are typically paraphyletic within phylogenetic trees and show similar morphological characters. The present study aimed to determine the taxonomic relationships among Anabaena and Nostoc strains of the Mosonmagyaróvár Algal Culture Collection (MACC) using 16S rRNA and rbcLX gene sequences. We concluded on the basis of the number of unsuccessful amplifications that more of the examined MACC Nostoc cultures are axenic than the Anabaena cultures. In agreement with previous studies we noticed that the applied phylogenetic algorithms gave congruent results in phylogenetic analyses. However, the genus Nostoc clearly was found not monophyletic in the present study and this finding differed from many of the previous studies. Molecular results contradicted the previous morphology-based classification of some MACC cyanobacteria strains, therefore polyphasic taxonomic approaches are required for the reliable identification of cyanobacterial species. Some strains seemed to be identical based on the alignment of 16S rRNA or rbcLX sequences.

Impact of substrate material on algal biofilm biomass growth.

Algae are being grown for wastewater purification and biofuels production. Their growth on a substrate facilitates these uses by allowing facile separation of algae from the water. Here, we compare different materials to determine which would best serve this purpose. A mixed culture of Anabaena and Chlorella was grown on various synthetic and natural fiber fabric substrates in a trough system with recirculating simulated wastewater. Filter materials studied as substrates for algal growth were muslin, olefin, pellon (acrylic), two types of polyester, and two types of nylon. Biomass accumulation on the various filter substrates was recorded at 7, 14, and 28days. Filters were weighed before and after the growth periods and changes in dry biomass were recorded. Biomass accumulation was significantly affected by the fabric type. Olefin fostered the greatest increase in biomass while nylon and polyester also supported competitive increases in biomass. Pellon showed the smallest biomass increase and muslin decreased in mass due to material disintegration. Other concerns such as abrasion resistance and UV susceptibility are discussed.

Role of Ca2+ as protectant under heat stress by regulation of photosynthesis and membrane saturation in Anabaena PCC 7120.

The present study was aimed at understanding the effects of heat stress on selected physiological and biochemical parameters of a model cyanobacterium, Anabaena PCC 7120 in addition to amelioration strategy using exogenous Ca2+. A comparison of the cells exposed to heat stress (0-24h) in the presence or absence of Ca2+ clearly showed reduction in colony-forming ability and increase in reactive oxygen species (ROS) leading to loss in the viability of cells of Ca2+-deficient cultures. There was higher level of saturation in membrane lipids of the cells supplemented with Ca2+ along with higher accumulation of proline. Similarly, higher quantum yield (7.8-fold) in Ca2+-supplemented cultures indicated role of Ca2+ in regulation of photosynthesis. Relative electron transport rate (rETR) decreased in both the sets with the difference in the rate of decrease (slow) in Ca2+-supplemented cultures. The Ca2+-supplemented sets also maintained high levels of open reaction centers of PS II in comparison to Ca2+-deprived cells. Increase in transcripts of both subunits ((rbcL and rbcS) of RubisCO from Ca2+-supplemented Anabaena cultures pointed out the role of Ca2+ in sustenance of photosynthesis of cells via CO2 fixation, thus, playing an important role in maintaining metabolic status of the heat-stressed cyanobacterium.

Succession and toxicity of Microcystis and Anabaena (Dolichospermum) blooms are controlled by nutrient-dependent allelopathic interactions

Microcystis and Anabaena (Dolichospermum) are among the most toxic cyanobacterial genera and often succeed each other during harmful algal blooms. The role allelopathy plays in the succession of these genera is not fully understood. The allelopathic interactions of six strains of Microcystis and Anabaena under different nutrient conditions in co-culture and in culture-filtrate experiments were investigated. Microcystis strains significantly reduced the growth of Anabaena strains in mixed cultures with direct cell-to-cell contact and high nutrient levels. Cell-free filtrate from Microcystis cultures proved equally potent in suppressing the growth of nutrient replete Anabaena cultures while also significantly reducing anatoxin-a production. Allelopathic interactions between Microcystis and Anabaena were, however, partly dependent on ambient nutrient levels. Anabaena dominated under low N conditions and Microcystis dominated under nutrient replete and low P during which allelochemicals caused the complete suppression of nitrogen fixation by Anabaena and stimulated glutathione S-transferase activity. The microcystin content of Microcystis was lowered with decreasing N and the presence of Anabaena decreased it further under low P and high nutrient conditions. Collectively, these results indicate that strong allelopathic interactions between Microcystis and Anabaena are closely intertwined with the availability of nutrients and that allelopathy may contribute to the succession, nitrogen availability, and toxicity of cyanobacterial blooms.

Optimization of biomass and hydrogen production by Anabaena sp. (UTEX 1448) in nitrogen-deprived cultures

Hydrogen is a non-polluting source of energy, which is renewable and very abundant in the universe. Microalgae and cyanobacteria produce hydrogen by breaking down water and organic compounds. The aim of this research was to develop hydrogen production using cyanobacterium Anabaena sp. by nitrogen deprivation in two experimental phases of cultivation, optimizing its biomass from physicochemical variables. The experiment was carried out with axenic culture, in BG-11 medium, in triplicate, in two steps and under continuous illumination: in the first step, cultures were maintained in an aerobic condition until the first half of growth phase under nitrogen limitation; in the second step, the biomass was transferred, by centrifugation and cell wash, to anaerobic photobioreactors under nitrogen deprivation and the atmosphere was changed by argon for hydrogen production. Hydrogen was detected by gas chromatography and the hydrogen production parameters were tested using the Gompertz model and the volume by the general ideal gas equation. The optimization of biomass in the first step of cultivation increased its yield by 18.3% and heterocysts formation was 3.4 times higher in nitrogen privation conditions. Therefore, hydrogen production by cell increased 55.2% and the productivity 57.6% when compared to the culture of Anabaena sp. in control condition. The method and the strain were effective for hydrogen production and the pH, temperature and light intensity affected the improvement of this production and increased the biomass yield.

Biodegradation of the aminopolyphosphonate DTPMP by the cyanobacterium Anabaena variabilis proceeds via a C-P lyase-independent pathway.

Cyanobacteria, the only prokaryotes capable of oxygenic photosynthesis, play a major role in carbon, nitrogen and phosphorus global cycling. Under conditions of increased P availability and nutrient loading, some cyanobacteria are capable of blooming, rapidly multiplying and possibly altering the ecological structure of the ecosystem. Because of their ability of using non-conventional P sources, these microalgae can be used for bioremediation purposes. Under this perspective, the metabolization of the polyphosphonate diethylenetriaminepenta(methylenephosphonic) acid (DTPMP) by the strain CCALA 007 of Anabaena variabilis was investigated using 31 P NMR analysis. Results showed a quantitative breakdown of DTPMP by cell-free extracts from cyanobacterial cells grown in the absence of any phosphonate. The identification of intermediates and products allowed us to propose a unique and new biodegradation pathway in which the formation of (N-acetylaminomethyl)phosphonic acid represents a key step. This hypothesis was strengthened by the results obtained by incubating cell-free extracts with pathway intermediates. When Anabaena cultures were grown in the presence of the phosphonate, or phosphorus-starved before the extraction, significantly higher biodegradation rates were found.

Development and evaluation of an organically certifiable growth medium for cultivation of cyanobacteria

On-farm cultivation of phototrophic, N-fixing cyanobacteria, grown in raceway ponds, could provide organic farmers an alternative N source to meet crop fertilizer needs. The application of cyanobacterial fertilizer in certified organic agriculture requires a growth medium of certified organic ingredients. This study compared growth and N-fixation of cyanobacteria cultured in two media, Allen and Arnon (AA) and a growth medium of organic-approved ingredients (RB) developed by the authors. A xenic culture of Anabaena sp. was grown for 2 weeks in the laboratory. The RB medium had significantly lower concentrations of P, Fe, B, Zn, and Cu than the AA medium. Cyanobacteria grown in RB had significantly greater exponential growth rate but significantly lower net total Kjeldahl nitrogen (TKN) than those grown in AA. In a follow-up replicated field study, the xenic culture of Anabaena sp. was inoculated into raceways aerated by paddle wheels. There was no significant difference in exponential or linear growth rate between the two treatments though the RB medium had lower concentrations of P, Co, Zn, and B than the AA medium. The lack of difference could be the result of an overarching limiting factor evident in both treatments such as light or C depletion or that the lower nutrient concentrations in RB were still sufficient for growth and N-fixation. There was no difference in net TKN between the two treatments, suggesting similar rates of N-fixation. Since bone meal contributed trace amounts of N to the RB media, it is possible that maximal N-fixation was not achieved. However, RB medium was able to support growth similar to that of the AA medium in raceway cultivation.

Membrane targeting of MnSOD is essential for oxidative stress tolerance of nitrogen-fixing cultures of Anabaena sp. strain PCC7120.

The nitrogen-fixing cyanobacterium, Anabaena PCC7120 encodes for a membrane-targeted 30kDa Mn-superoxide dismutase (MnSOD) and a cytosolic FeSOD. The MnSOD is post-translationally processed to 27 and 24kDa forms in the cytosol and periplasm/thylakoid lumen. The extent of cleavage of signal and linker peptides at the N-terminus is dependent on the availability of combined nitrogen during growth. While the 24 and 27kDa forms are present in near equal proportions under nitrogen-fixing conditions, the 24kDa form is predominant under nitrogen-supplemented conditions. Individual contribution of these forms of MnSOD to total oxidative stress tolerance was analysed using recombinant Anabaena strains overexpressing either different molecular forms of MnSOD or MnSOD defective in the cleavage of signal/linker peptide. Targeting of MnSOD to the membrane and subsequent cleavage to release both the 24 and 27kDa forms was essential for oxidative stress tolerance under nitrogen-fixing conditions. On the other hand, the cleavage of linker peptide was absolutely essential and the release of cytosolic 24kDa form of MnSOD was obligatory for developing oxidative stress tolerance under nitrogen-supplemented conditions. Thus, a single MnSOD caters to the reduction of superoxide radical in both cytosol and thylakoid lumen/periplasm irrespective of the N-status of growth by regulating its cleavage. This is the first report on the physiological advantage of membrane-targeting and processing of MnSOD in either bacteria or plants. The higher oxidative stress tolerance offered by the cytosolic form of MnSOD has possibly resulted in retention of only the cytosolic form in bacterial non-nitrogen-fixers during evolution.

Effect of plant-growth-promoting rhizobacteria inoculation on plant growth, productivity and economics of Basmati rice

A field experiment was conducted in a wet season (Kharif) to study the effects of plant growth-promoting rhizobacteria(PGPR) inoculation on agronomic traits and productivity of Basmati rice (cv. ‘Pusa Basmati 1401’) in a randomized block with twelve treatments. We evaluated one bacterial (Providencia sp. PW5) and one cyanobacterial strain (Anabaena sp. CR3), and also a Multani mitti (Fuller’s earth)-based blue-green algal biofertilizer (a composite culture of Anabaena, Nostoc, Tolypothrix and Aulosira sp.). Plant growth, yield attributes, yield and net return of rice were significantly improved due to the rhizobacterial inoculation. The highest responses were recorded from combined inocula of bacteria and cyanobacteria together with compost.Keywords: Bacterial inoculants; BGA; cyanobacterial inoculants, PGPR; yield attributes.

Assessment of the CO2 fixation capacity of Anabaena sp. ATCC 33047 outdoor cultures in vertical flat-panel reactors

The extent of biological CO2 fixation was evaluated for outdoor cultures of the cyanobacterium Anabaena sp. ATCC 33047. Culture conditions were optimized indoors in bubble-column photochemostats operating in continuous mode, subjected to irradiance cycles mimicking the light regime outdoors. Highest values achieved for CO2 fixation rate and biomass productivity were 1 and 0.6gL−1day−1, respectively. The comparison among different reactors operating simultaneously – open pond, horizontal tubular reactor and vertical flat-panel – allowed to assess their relative efficiency for the outdoor development of Anabaena cultures. Despite the higher volumetric CO2 fixation capacity (and biomass productivity) exhibited by the tubular photobioreactor, yield of the flat-panel reactor was 50% higher than that of the tubular option on a per area basis, reaching values over 35g CO2 fixed m−2d−1. The flat-panel reactor actually represents a most suitable system for CO2 capture coupled to the generation of valuable biomass by Anabaena cultures.

Detection of Anatoxin-a and Three Analogs in Anabaena spp. Cultures: New Fluorescence Polarization Assay and Toxin Profile by LC-MS/MS

Anatoxin-a (ATX) is a potent neurotoxin produced by several species of Anabaena spp. Cyanobacteria blooms around the world have been increasing in recent years; therefore, it is urgent to develop sensitive techniques that unequivocally confirm the presence of these toxins in fresh water and cyanobacterial samples. In addition, the identification of different ATX analogues is essential to later determine its toxicity. In this paper we designed a fluorescent polarization (FP) method to detect ATXs in water samples. A nicotinic acetylcholine receptor (nAChR) labeled with a fluorescein derivative was used to develop this assay. Data showed a direct relationship between the amount of toxin in a sample and the changes in the polarization degree of the emitted light by the labeled nAChR, indicating an interaction between the two molecules. This method was used to measure the amount of ATX in three Anabaena spp. cultures. Results indicate that it is a good method to show ATXs presence in algal samples. In order to check the toxin profile of Anabaena cultures a LC-MS/MS method was also developed. Within this new method, ATX-a, retention time (RT) 5 min, and three other molecules with a mass m/z 180.1 eluting at 4.14 min, 5.90 min and 7.14 min with MS/MS spectra characteristic of ATX toxin group not previously identified were detected in the Anabaena spp. cultures. These ATX analogues may have an important role in the toxicity of the sample.

A sequential procedure for the quantification of biologically produced polyphosphate in sediment samples

A sequential procedure for the quantification of biologically produced polyphosphate in sediment samples Polyphosphate (poly-P) is a phosphate storage compound widespread in prokaryotic and eukaryotic cells. Its quantification, however, is not yet well developed for sediment samples because of the difficulties associated with using a single extractant to extract a specifie P compound without altering others. The present work uses an analytical procedure already developed to measure poly-P in algal cultures and later modified here for sediments to study poly-P in the sediment. The procedure uses the Ethylenediaminetetraacetic aeid (EDTA) method for sequential P-fractionation. This approach ensures that the main inorganic phosphate compounds (Le., Fe- and Ca-bound phosphate) are extracted prior to poly-P quantification. We applied this method to suspensions likely to contain biologically produced poly-P, such as laboratory cultures of Synechocystis PCC 6803 (Cyanobacteriaceae), Anabaena variabilis (Cyanobacteriaceae), and Chlorella sp. (Chlorophyceae) growing in a P­enriched medium, and activated sludge. According to this procedure, the concentrations of poly-P in Synechocystis PCC 6803, Anabaena variabilis and Chlorella cultures were 15.4, 6.2 and 7.2 % of the sum of all P-fractions, respectively, whereas activated sludge showed a lower percentage (3.7 %). Known volumes of these suspensions and a commercially available synthetic poly-P standard (Trimetaphosphate) were added to natural sediment. The P-composition of each sample was then compared in duplicate to the corresponding control samples (sediment alone). Poly-P in all control sediment samples was extremely low (0-2 ~g g-l d.w.). It increased in all sediment suspensions to which biological samples had been added. The increase was particularly noteworthy for Synechocystis (up to 220 ~g g-l d.w. of poly-P). The recovery of poly-P in sediment samples to which Anabaena cultures had been added showed some deviation from al: 1 expected:observed ratio, particularly when 2 mi of the culture were added (ratio of 0.79). However, the recovery improved to 1.12: 1 when a larger volume was added (5 mi), probably owing to the inhomogeneous nature of the cyanobacteria culture. In contrast, the addition of 500 mg of trimetaphosphate to the control sediment did not significantly increase (p > 0.05) the percentage found for the observed poly-P fraction. Consequently, biologically produced poly-P can be associated with the fraction of poly-P extracted through use of this procedure.

Unusual radioresistance of nitrogen-fixing cultures of Anabaena strains

Nitrogen-fixing cultures of two species of the filamentous, heterocystous cyanobacterium Anabaena, namely Anabaena sp. strain L-31 and Anabaena torulosa were found to be highly tolerant to 60Co gamma radiation. No adverse effect on diazotrophic growth and metabolism were observed up to a dose of 5 kGy. At higher doses, radiation tolerance showed a correspondence with the inherent osmotolerance, with Anabaena L-31 being the more radiation tolerant as well as osmotolerant strain. In Anabaena L-31, exposure to 6 kGy of gamma rays resulted in genome disintegration, but did not reduce viability. Irradiation delayed heterocyst differentiation and nitrogen fixation, and marginally affected diazotrophic growth. All the affected parameters recovered after a short lag, without any discernible postirradiation phenotype. The radiation tolerance of these Gram-negative photoautodiazotrophs is comparable with that of the adiazotrophic photoautotrophic cyanobacterium Chroococcidiopsis or adiazotrophic heterotroph Deinococcus radiodurans. This is the first report of extreme radioresistance in nitrogen-fixing Anabaena cultures.

Utilization of the cyanobacteria Anabaena sp. ATCC 33047 in CO 2 removal processes

In this paper the utilization of the cyanobacteria Anabaena sp. in carbon dioxide removal processes is evaluated. For this, continuous cultures of this strain were performed at different dilution rates; alternatives for the recovery of the organic matter produced being also studied. A maximum CO 2 fixation rate of 1.45 g CO 2 L −1 day −1 was measured experimentally, but it can be increased up to 3.0 g CO 2 L −1 day −1 outdoors. The CO 2 is mainly transformed into exopolysaccharides, biomass representing one third of the total organic matter produced. Organic matter can be recovered by sedimentation with efficiencies higher than 90%, the velocity of sedimentation being 2 · 10 −4 s −1. The major compounds were carbohydrates and proteins with productivities of 0.70 and 0.12 g L −1 day −1, respectively. The behaviour of the cultures of Anabaena sp. has been modelized, also the characteristics parameters requested to design separation units being reported. Finally, to valorizate the organic matter as biofertilizers and biofuels is proposed.

Molecular response of Anabaena flos‐aquae to differing concentrations of phosphorus: A combined Fourier transform infrared and X‐ray microanalytical study

SUMMARYThe response of Anabaena flos‐aquae to varying levels of P availability was determined using the combined techniques of Fourier transform infrared (FTIR) microspectroscopy and energy‐dispersive X‐ray microanalysis (EDXRMA). Batch cultures of Anabaena were grown at initial P concentrations of 50 μg (low‐P culture), 500 μg (intermediate‐P) and 5000 μg (high‐P) (PO4‐P L−1) and were monitored for total biovolume, chlorophyll a, media nutrients (PO4‐P and NO3‐N), cellular P quota (EDXRMA) and carbon allocation (FTIR spectroscopy). The high‐P culture showed a sixfold increase in total biovolume over the sampling period. Phosphorus in the media remained at more than ∼4000 μg L−1 and intracellular P concentration (P quota) as determined by EDXRMA showed no decline, remaining at more than 0.20% dry weight (DW). The intermediate‐P culture showed a similar increase in total biovolume, but P concentrations in the media fell to ∼20 μg L−1, and this was reflected in a decline in the cellular P quota from 0.24% to 0.06% DW. Although the high‐ and intermediate‐P treatments differed markedly in both internal and external P, analysis of the FTIR spectra from the two treatments, using both hierarchical cluster analysis (HCA) and principal component analysis (PCA), indicated no difference in carbon allocation. Cells from the low‐P treatment showed strong evidence for P deficiency. P concentrations in the media were undetectable (<5 μg L−1), total biovolume was much reduced, and P quotas were low, falling from 0.08% to 0.01% DW. HCA and PCA clearly separated FTIR spectra from low‐P cells from those of intermediate‐ and high‐P cultures, with low‐P cells having increased absorbance in the region of the spectra associated with carbohydrate. Both FTIR spectroscopy and EDXRMA have the resolution to study the elemental and macromolecular composition of single species within mixed phytoplankton populations and the combined use of these techniques has considerable potential for the study of cyanobacterial responses to environmental stress.

The Effect of Polymeric Substances on Apatite Reactivity in the Presence of a Freshwater Cyanobacterium

Marine cyanobacteria have evolved phosphate uptake systems to live where P is limiting. Ultimately, P derives from apatite in rocks but little is known about apatite solubilization by cyanobacteria. Fluorapatite (FAP) was added to a P-free culture medium with and without Anabaena, as well as in cell-free supernatant to test reports that the cyanobacterium Anabaena PCC 7120 enhances the dissolution of fluorapatite (FAP). Anabaena, a fresh-water organism, is an analogue to harder-to-grow marine cyanobacteria. The initial abiotic release rate ratios (Ca/P) are significantly higher than the similar stoichiometric ratio of apatite. The majority of the “missing” P in abiotic experiments is sorbed to precipitates formed from Fe added as a nutrient to the culture medium. In contrast to literature reports, Ca release from FAP in the presence of Anabaena or culture supernatant was lower than abiotic release. However, Anabaena cultures aggregate and cells attach to the FAP when P-limited. Adhesion is explained by surface charge rather than P content because significant adhesion on boehmite occurred in similar experiments. X-ray photoelectron spectroscopic (XPS) analysis of the FAP surface after incubation with Anabaena is consistent with sorbed proteins that promote adhesion. These released polymers are also inferred to complex with Ca during dissolution, contributing to nucleation of Ca-P precipitates in experiments with cells or supernatant. These experiments emphasize that for Anabaena growing under P-limited conditions, polymeric material is important for cellular adhesion to mineral particles and for the concentration of phosphate as Ca-or Fe-complexes or nanoparticles.