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Cyanobacteria associated with mosses play a key role in the nitrogen (N) cycle in unpolluted ecosystems. Mosses have been found to release molecules that induce morphophysiological changes in epiphytic cyanobionts. Nevertheless, the extent of moss influence on these microorganisms remains unknown. To evaluate how mosses or their metabolites influence N2 fixation rates by cyanobacteria, we assessed the nitrogenase activity, heterocyte frequency and biomass of a cyanobacterial strain isolated from the feather moss Hylocomium splendens and a non-symbiotic strain when they were either growing by themselves, together with H. splendens or exposed to H. splendens water, acetone, ethanol, or isopropanol extracts. The same cyanobacterial strains were added to another moss (Taxiphyllum barbieri) and a liverwort (Monosolenium tenerum) to assess if these bryophytes affect N2 fixation differently. Although no significant increases in nitrogenase activity by the cyanobacteria were observed when in contact with H. splendens shoots, both the symbiotic and non-symbiotic cyanobacteria increased nitrogenase activity as well as heterocyte frequency significantly upon exposure to H. splendens ethanol extracts. Contact with T. barbieri shoots, on the other hand, did lead to increases in nitrogenase activity, indicating low host-specificity to cyanobacterial activity. These findings suggest that H. splendens produces heterocyte-differentiating factors (HDFs) that are capable of stimulating cyanobacterial N2 fixation regardless of symbiotic competency. Based on previous knowledge about the chemical ecology and dynamics of moss-cyanobacteria interactions, we speculate that HDF expression by the host takes place in a hypothetical new step occurring after plant colonization and the repression of hormogonia. [ABSTRACT FROM AUTHOR]

Microplastic pollution is widespread around the world and inevitably comes into contact with organisms. With the accumulation of microplastics in the environment, the negative impact of microplastics on organisms has become the main focus in the field of microplastics. In this study, the different particle and concentration effects of fluorescent polystyrene microplastics (PS-MPs) on Nostocaceae and Daphnia Magna were researched. The results indicate that PS-MPs adhered to Nostocaceae through static electricity, which hindered the absorption of photons and CO2 by Nostocaceae, resulting in a decrease in chlorophyll, a low growth rate and high mortality for Nostocaceae. PS-MPs with very small particles may be integrated into the blood of Daphnia Magna, leading to an increasing trend of mortality and a decrease in spawning rate. The research provides basic data and a reference for the effect of PS-MPs on freshwater organisms and has implications for the further study of microplastics. [ABSTRACT FROM AUTHOR]

هدف از این مطالعه، یافتن روابط فیلوژنتیک سیانوباکتری‌ها براساس ژن‌های 16S rRNA و ITS و توالی‌های پالیندرومی HIP، ERIC و STRR بوده است. به این منظور، نمونه‌برداری از پنج چشمه از قنات‌های کم‌عمق روستاهای گنبدکاووس (استان گلستان) انجام شد و در محیط کشت Z8 خالص‌سازی گردید. پس از استخراج DNA، ژن‌های 16S rRNA و ITS تکثیر و توالی‌یابی شدند. درخت فیلوژنتیک با استفاده از روش Likelihood Maximum و مدل مناسب به کمک وب سرور برخط Iqtree server ساخته شد. ساختار ثانویه ITS، در بخش‌های مختلف مارپیچ D1-D1′، D2، D3، tRNAIle، tRNAAla، BOX B، BOX A و V3 به کمک برنامه Mfold رسم شد. سپس، آنالیز فیلوژنتیک انگشت‌نگاری‌ها به کمک حضور و عدم حضور باندهای مجزا و قابل تکثیر در هر الگوی انگشت‌نگاری DNA تولید شده با پروفایل‌های PCR HIP، ERIC و STRR، به اطلاعات دوتایی تبدیل برای ساختن دندروگرام مرکب، استفاده شد. نتایج نشان داد که سویه‌های مورد بررسی متعلق به چهار تیره به اسامی Aphanizomenonaceae، Nostocaceae، Hapalosiphonaceae و Calotrichaceae از زیربخش راسته Nostocales بودند. نتایج کلاسترهای دندروگرام‌های رسم شده حاصل از تکثیر توالی‌های پالیندرومی تاییدکننده کلاستربندی‌های درخت‌های فیلوژنتیکی بود. به هر ‌حال، نتایج حاصل از بخش‌های متغیر در بخش‌های D1-D1′ و Box-B ژن ITS، ساختارهای ثانویه منحصر به ‌فردی یافت گردید که الگوی مشابهی با سویه‌های نزدیک به خود را نداشتند. نتایج کلی نشان داد که داده‌های حاصل از انگشت‌نگاری‌های ژنومیک، آنالیزهای درون‌رایانه‌ای و فیلوژنتیکی، برای تمایز سویه‌های نزدیک به هم سیانوباکتری‌ها بسیار مفید می‌باشند.

During a study of biodiversity of cyanobacteria in Gorely volcano soils (Kamchatka Peninsula), a strain of heterocytous, a false branching cyanobacterium with gradually tapered filaments, was isolated. Prominent features of the strain were purplish-grey trichomes and firm, distinct multilayered sheaths. Based on the results obtained from the morphological, ecological, and phylogenetic analysis using the 16S rRNA and 16S–23S ITS region, 16S–23S ITS secondary structure analysis, comparison of flanking regions of BoxB and V3 helices, and the p-distance between the 16S–23S ITS region, we describe our strain K7 as a novel species of the genus Roholtiella with the name Roholtiella volcanica sp. nov., in accordance with the International Code of Nomenclature for algae, fungi, and plants. This work continues the rapid expansion of the description of new taxa of cyanobacteria, and particularly demonstrates a coming phase in cyanobacterial taxonomy in which the discovery of new species in recently described genera rapidly increases our understanding of the diversity in this phylum. [ABSTRACT FROM AUTHOR]

Microplastic pollution is widespread around the world and inevitably comes into contact with organisms. With the accumulation of microplastics in the environment, the negative impact of microplastics on organisms has become the main focus in the field of microplastics. In this study, the different particle and concentration effects of fluorescent polystyrene microplastics (PS-MPs) on Nostocaceae and Daphnia Magna were researched. The results indicate that PS-MPs adhered to Nostocaceae through static electricity, which hindered the absorption of photons and CO2 by Nostocaceae, resulting in a decrease in chlorophyll, a low growth rate and high mortality for Nostocaceae. PS-MPs with very small particles may be integrated into the blood of Daphnia Magna, leading to an increasing trend of mortality and a decrease in spawning rate. The research provides basic data and a reference for the effect of PS-MPs on freshwater organisms and has implications for the further study of microplastics.

Cyanobacteria are recognized as important colonizers and protectors of soil surfaces, particularly in biological soil crusts (BSCs) of arid and semiarid regions. Comparatively, little attention has been paid to the growth of cyanobacteria, algae, and moss on agricultural soils in more humid regions like eastern North America. Growth of soil surface consortia (SSCs) in agricultural fields is typically rapid and ephemeral yet recurrent, thereby differing from classical BSCs of semiarid regions and algal mats of aquatic systems. Naturally occurring or intentionally applied cyanobacteria to agricultural soils could thus provide renewable sources of carbon and nitrogen (N) and a means to improve soil resilience. Here, we describe a soil microcosm-based protocol to assess cyanobacteria for their ability to form SSCs using three criteria: reliability of serial transfers in N-free culture media, robust growth in soil microcosms, and resistance to detachment from soil particles subjected to water flushing. Screening of 100 enrichment cultures from local SSCs yielded three that exhibited robust growth on N-free solid media and consistent microscopic appearance as filamentous, heterocystous cyanobacteria. One enrichment (DG1) grew reliably in liquid N-free media and was selected for comparison with pure cultures of commercial strains of other heterocystous cyanobacteria. Growth and biomass density of DG1 and commercial strains on moist, N-limited soils were tracked using chlorophyll a measurements and water flush tests. Anabaena spp. grew faster on soil surfaces, but their 80-day SSCs did not adhere to soil as well as DG1 or Nostoc spp. in water flush tests. The ability of DG1 and Nostoc spp. to produce flocculated growth in liquid culture appeared to be associated with greater soil adherence. While Nostoc spp. formed stable SSCs in soil microcosms, they exhibited lower growth rates and biomass densities than DG1. Attempts to purify the cyanobacterial strain(s) from other bacteria in the DG1 enrichment were unsuccessful. Based on initial metagenomics analysis, the DG1 enrichment was a consortium containing at least six other bacterial genotypes but dominated by one or more closely related strains of Cylindrospermum spp. (Nostocaceae). The presence of bacterial associates did not interfere with rapid growth and high biomass density in soil microcosms, as well as SSC stability in water flush tests. The artificial SSCs formed by DG1 showed good potential for use as a renewable N source for agroecosystems. [ABSTRACT FROM AUTHOR]

Benthic cyanobacteria recognized as producers of natural products, including cyanotoxins, have been neglected for systematic toxicological studies. Thus, we have performed a broad study investigating cyanotoxin potential of 311 non-planktic nostocacean representatives combining molecular and chemical analyses. Out of these, a single strain Nostoc sp. Treb K1/5, was identified as a new microcystin producer. Microcystins [Asp 3 ]MC-YR, [Asp 3 ]MC-FR, [Asp 3 ]MC-HtyR and Ala-Leu/Ile-Asp-Arg-Adda-Glu-Mdha are reported for the first time from the genus Nostoc . All the studied strains were also analyzed for the occurrence of nodularins, cylindrospermopsin and (homo)anatoxin-a, yet no novel producer has been discovered. Our findings indicate rare occurrence of the common cyanotoxins in non-planktic nostocaceae which is in contrast with frequent reports of cyanotoxin producers among phylogenetically closely related planktic cyanobacteria. [ABSTRACT FROM AUTHOR]

Abstract: Plants associated with symbiotic N‐fixing bacteria play important roles in early successional, riparian and semi‐dry ecosystems. These so‐called N‐fixing plants are widely used for reclamation of disturbed vegetation and improvement of soil fertility in agroforestry. Yet, available information about plants that are capable of establishing nodulation is fragmented and somewhat outdated. This article introduces the NodDB database of N‐fixing plants based on morphological and phylogenetic evidence (available at https://doi.org/10.15156/bio/587469) and discusses plant groups with conflicting reports and interpretation, such as certain legume clades and the Zygophyllaceae family. During angiosperm evolution, N‐fixing plants became common in the fabid rather than in the ‘nitrogen‐fixing’ clade. The global GBIF plant species distribution data indicated that N‐fixing plants tend to be relatively more diverse in savanna and semi‐desert biomes. The compiled and re‐interpreted information about N‐fixing plants enables accurate analyses of biogeography and community ecology of biological N fixation. [ABSTRACT FROM AUTHOR]

Summary: Heterocyst‐forming cyanobacteria are organized as multicellular filaments of tightly interacting, functionally specialized cells. N2‐fixing heterocysts differentiate from vegetative cells under nitrogen limitation in a semi‐regular pattern along the filament. Diazotrophic growth requires metabolite exchange between neighboring cells within the filament. This exchange occurs via cell–cell junction complexes that span the gap between the plasma membranes and thereby cross the septal peptidoglycan through an array of uniform nanopores formed by AmiC‐type cell wall hydrolases. We investigated how the lytic hydrolase AmiC1 (Alr0092) from Anabaena sp. PCC 7120, whose activity needs to be tightly controlled to avoid cell lysis, is regulated by the LytM factor Alr3353. Inactivation of alr3353 resulted in significantly fewer nanopores and as a consequence, a lower rate of fluorescent tracer exchange between cells. The mutant was not able to grow with N2 as sole nitrogen source, although heterocysts were formed. Alr3353 localized mainly to fully developed intercellular septa of vegetative cells. The purified protein bound to peptidoglycan and enhanced the hydrolytic activity of AmiC1 in vitro. Our data show that the LytM factor Alr3353 regulates nanopore formation and cell–cell communication by directly interacting with AmiC1. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Phylogenetic relationships among heterocytous genera (the Nostocales order) have been profoundly modified since the use of polyphasic approaches that include molecular data. There is nonetheless still ample scope for improving phylogenetic delineations of genera with broad ecological distributions, particularly by integrating specimens from specific or up-to-now poorly sampled habitats. In this context, we studied 36 new isolates belonging to Chrysosporum, Dolichospermum , Anabaena , Anabaenopsis , and Cylindrospermopsis from freshwater ecosystems of Burkina-Faso, Senegal, and Mayotte Island. Studying strains from these habitats is of particular interest as we suspected different range of salt variations during underwent periods of drought in small ponds and lakes. Such salt variation may cause different adaptation to salinity. We then undertook a polyphasic approach, combining molecular phylogenies, morphological analyses, and physiological measurements of tolerance to salinity. Molecular phylogenies of 117 Nostocales sequences showed that the 36 studied strains were distributed in seven lineages: Dolichospermum , Chrysosporum, Cylindrospermopsis / Raphidiopsis , Anabaenopsis , Anabaena sphaerica var tenuis / Sphaerospermopsis , and two independent Anabaena sphaerica lineages. Physiological data were congruent with molecular results supporting the separation into seven lineages. In an evolutionary context, salinity tolerance can be used as an integrative marker to reinforce the delineation of some cyanobacterial lineages. The history of this physiological trait contributes to a better understanding of processes leading to the divergence of cyanobacteria. In this study, most of the cyanobacterial strains isolated from freshwater environments were salt-tolerant, thus suggesting this trait constituted an ancestral trait of the heterocytous cyanobacteria and that it was probably lost two times secondarily and independently in the ancestor of Dolichospermum and of Cylindrospermopsis . [ABSTRACT FROM AUTHOR]

Nostocacean cyanobacteria are one of the important components of paddy fields due to their ability to fix atmospheric nitrogen and supply phytohormones for crop growth. In this study, 13 Nostoc strains isolated from paddy soils in Vietnam were classified using a polyphasic approach. The results showed a high diversity of the isolated strains that represented seven morphotypes corresponding to five genotypes, with 16S rRNA gene sequence similarity values ranging between 94.97–99.78% compared to the available sequences from GenBank. Bioassay assessment revealed that 11 out of 13 strains possessed antibacterial activities, three of which exhibited cytotoxic activities on MCF7 and HCT116 cells with an IC 50 ranging from 47.8 μg mL −1 to 232.0 μg mL −1 . Interestingly, strains with identical 16S rRNA gene sequences displayed different antibacterial and cytotoxic activity profiles. [ABSTRACT FROM AUTHOR]

Allelopathy has been proposed as a sustainable means to control undesired algal growth and to reduce blooms threatening freshwater systems worldwide. In this study, the allelopathic effects of Myriophyllum aquaticum and its exudate on two typical bloom-forming cyanobacteria, Microcystis aeruginosa and Anabaena flos-aquae, were investigated under laboratory conditions. The growth of the cyanobacteria was strongly inhibited by live M. aquaticum while the primary addition of M. Aquaticum exudates had a significant inhibitory effect on the growth of M. aeruginosa but not A. flos-aquae. The results suggested that the persistent release of allelochemicals from live M. aquaticum was needed to effectively constrain the growth of A. flos-aquae. Analysis of cyanobacterial physiological indexes indicated that M. aquaticum produced an inhibitory effect on SOD enzyme activity of A. flos-aquae, while it affected membrane lipid peroxidation in M. aeruginosa. The results show the potential of M. aquaticum to mitigate cyanobacterial blooms in coexistence systems. [ABSTRACT FROM AUTHOR]

The halotolerant cyanobacterium Anabaena sp was grown under NaCl concentration of 0, 170 and 515 mM and physiological and proteomic analysis was performed. At 515 mM NaCl the cyanobacterium showed reduced photosynthetic activities and significant increase in soluble sugar content, proline and SOD activity. On the other hand Anabaena sp grown at 170 mM NaCl showed optimal growth, photosynthetic activities and comparatively low soluble sugar content, proline accumulation and SOD activity. The intracellular Na content of the cells increased both at 170 and 515 mM NaCl. In contrast, the K content of the cyanobacterium Anabaena sp remained stable in response to growth at identical concentration of NaCl. While cells grown at 170 mM NaCl showed highest intracellular K/Na ratio, salinity level of 515 mM NaCl resulted in reduced ratio of K/Na. Proteomic analysis revealed 50 salt-responsive proteins in the cyanobacterium Anabaena sp under salt treatment compared with control. Ten protein spots were subjected to MALDI-TOF-MS/MS analysis and the identified proteins are involved in photosynthesis, protein folding, cell organization and energy metabolism. Differential expression of proteins related to photosynthesis, energy metabolism was observed in Anabaena sp grown at 170 mM NaCl. At 170 mM NaCl increased expression of photosynthesis related proteins and effective osmotic adjustment through increased antioxidant enzymes and modulation of intracellular ions contributed to better salinity tolerance and optimal growth. On the contrary, increased intracellular Na content coupled with down regulation of photosynthetic and energy related proteins resulted in reduced growth at 515 mM NaCl. Therefore reduced growth at 515 mM NaCl could be due to accumulation of Na ions and requirement to maintain higher organic osmolytes and antioxidants which is energy intensive. The results thus show that the basis of salt tolerance is different when the halotolerant cyanobacterium Anabaena sp is grown under low and high salinity levels. [ABSTRACT FROM AUTHOR]

In the last decade, many studies have been conducted to employ genetically engineered cyanobacteria in the production of various metabolites. However, the lack of a strict gene regulation system in cyanobacteria has hampered these attempts. The filamentous cyanobacterium Anabaena sp. PCC 7120 performs both nitrogen and carbon fixation and is, therefore, a good candidate organism for such production. To employ Anabaena cells for this purpose, we intended to develop artificial gene regulation systems to alter the cell metabolic pathways efficiently. We introduced into Anabaena a transcriptional repressor TetR, widely used in diverse organisms, and green fluorescent protein (GFP) as a reporter. We found that anhydrotetracycline (aTc) substantially induced GFP fluorescence in a concentration-dependent manner. By expressing tetR under the nitrate-specific promoter nirA, we successfully reduced the concentration of aTc required for the induction of gfp under nitrogen fixation conditions (to 10% of the concentration needed under nitrate-replete conditions). Further, we succeeded in the overexpression of GFP by depletion of nitrate without the inducer by means of promoter engineering of the nirA promoter. Moreover, we applied these gene regulation systems to a metabolic enzyme in Anabaena and successfully repressed glnA, the gene encoding glutamine synthetase that is essential for nitrogen assimilation in cyanobacteria, by expressing the small antisense RNA for glnA. Consequently, the ammonium production of an ammonium-excreting Anabaena mutant was significantly enhanced. We therefore conclude that the gene regulation systems developed in this study are useful tools for the regulation of metabolic enzymes and will help to increase the production of desired substances in Anabaena. [ABSTRACT FROM AUTHOR]

The colonization and succession of diazotrophs are essential for the development of organic soil layers in desert. We examined the succession of diazotrophs in the well-established revegetated areas representing a chronosequence of 0 year (control), 22 years (restored artificially since 1981), 57 years (restored artificially since 1956), and more than 100 years (restored naturally) to determine the community assembly and active expression of diazotrophs. The pyrosequencing data revealed that Alphaproteobacteria-like diazotrophs predominated in the topsoil of our mobile dune site, while cyanobacterial diazotrophs predominated in the revegetated sites. The cyanobacterial diazotrophs were primarily composed of the heterocystous genera Anabaena, Calothrix, Cylindrospermum, Nodularia, Nostoc, Trichormus, and Mastigocladus. Almost all the nifH sequences belonged to the Cyanobacteria phylum (all the relative abundance values >99.1 %) at transcript level and all the active cyanobacterial diazotrophs distributed in the families Nostocaceae and Rivulariaceae. The most dominant active cyanobacterial genus was Cylindrospermum in all the samples. The rank abundance and community analyses demonstrated that most of the diazotrophic diversity originated from the 'rare' species, and all the DNA-based diazotrophic libraries were richer and more diverse than their RNA-based counterparts in the revegetated sites. Significant differences in the diazotrophic community and their active population composition were observed among the four research sites. Samples from the 1981-revegetating site (predominated by cyanobacterial crusts) showed the highest nitrogenase activity, followed by samples from the naturally revegetating site (predominated by lichen crusts), the 1956-revegetating site (predominated by moss crusts), and the mobile dune site (without crusts). Collectively, our data highlight the importance of nitrogen fixation by the primary successional desert topsoil and suggest that the N-fixing cyanobacteria are the key diazotrophs to the nitrogen budget and the development of topsoil in desert, which is critical for the succession of the degraded terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Cylindrospermopsis raciborskii is a toxic cyanobacterium which is responsible for the formation of Harmful Algal Blooms (HABs) and it is commonly described to prefer low light conditions. To elucidate the mechanisms that makes this species successful in such environments, we studied the physiological characteristics of C. raciborskii (strain NPD) exposed to both saturating (80 μmol photons m −2 s −1 ) and suboptimal (10 μmol photons m −2 s −1 ) light intensities. When exposed to the low light of 10 μmol photons m −2 s −1 , C. raciborskii showed a slower cell division rate ( μ c ), lower respiration rate ( R d ) and higher cell quotas of Chl a and phycocyanin. However, no differences in the cellular light harvesting efficiency ( α ) and maximal photosynthetic rate ( P max ) were observed. Under low light, the unchanged photosynthesis was associated with both functional maintenance of the photosynthetic machinery and a larger cross-sectional area of PSIIα-centres (σPSIIα). In relation to the literature, our results indicate that C. raciborskii NPD responds to low light by changing the size of the light harvesting antenna. Ecologically, the physiological acclimations observed suggest that C. raciborskii NPD can perform well in environments where light intensity is low and relatively stable, as might occur during the final stages of HABs. [ABSTRACT FROM AUTHOR]

The induction of systemic defence responses in zucchini leaves treated by a water extract of Anabaena sp. BEA0300B strain was studied firstly through a bioassay under Podosphaera xanthii (Castagne) U. Braun and Shishkoff challenge. In a second experiment, enzyme activities correlated to induced systemic resistance were assayed 1, 2 and 3 days after treatment (DAT) with BEA0300B on untreated cotyledonar leaves. Endochitinase, β-N- acetylhexosaminidase, chitin 1,4- β -chitobiosidase, β -1,3-glucanase and peroxidases were spectrophotometrically determined. Enzyme isoforms were detected after isoelectric focusing. The extract reduced P. xanthii symptoms by 25%, similarly to chitosan, the positive control. BEA0300B treatment caused systemic accumulation of all the enzymes. In particular, the treatment provoked an early increase of total chitinase activity (15–38%) and of the expression of two constitutive chitinase isoforms, pI 4.4 (159%) and pI 4.6 (433%). The total β -1,3-glucanase and peroxidase activities were transiently increased. The expression of two constitutive isoforms of these enzyme increased, particularly pI 5.0 glucanase (148%, 1 DAT) and pI 4.9 peroxidase (181%, 2 DAT). BEA0300B water extract also showed a direct antifungal activity on pathogen sporulation. [ABSTRACT FROM AUTHOR]

The family Microchaetaceae is a large group of heterocytous cyanobacteria, whose members bear typical morphological features of uniseriate heteropolar filaments never terminated by thin hairs and with simple false branching. However, phylogenetic analyses of the gene for 16S rRNA showed that members of this traditionally morphologically delimited family form several distant groups and therefore the current concept is hereafter indefensible. In this study, we provide reassessment of the status of the family Microchaetaceae based on morphology, ecology, biogeography, and phylogeny of 16S rRNA gene. Thorough examination of strains of the nominate genus Microchaete revealed their affiliation to two groups, Nostocaceae and Rivulariaceae, and their distant position to other traditional members of Microchaetaceae such as Tolypothrix, Hassallia, and Coleodesmium. To reflect the phylogenetic relationships and to accommodate members of the traditional family Microchaetaceae that are clearly not related to any of the Microchaete representatives, we propose establishment of two new families, Tolypothrichaceae and Godleyaceae. Based on both molecular and morphological evidence, we also provide a description of three new species of the genus Fortiea. [ABSTRACT FROM AUTHOR]

Anabaena variabilis ATCC 29413 is a filamentous, heterocyst-forming cyanobacterium that has served as a model organism, with an extensive literature extending over 40 years. The strain has three distinct nitrogenases that function under different environmental conditions and is capable of photoautotrophic growth in the light and true heterotrophic growth in the dark using fructose as both carbon and energy source. While this strain was first isolated in 1964 in Mississippi and named Anabaena flos-aquae MSU A-37, it clusters phylogenetically with cyanobacteria of the genus Nostoc. The strain is a moderate thermophile, growing well at approximately 40° C. Here we provide some additional characteristics of the strain, and an analysis of the complete genome sequence. [ABSTRACT FROM AUTHOR]

Twenty-six strains morphologically identified as Cylindrospermum as well as the closely related taxon Cronbergia siamensis were examined microscopically as well as phylogenetically using sequence data for the 16S r RNA gene and the 16S-23S internal transcribed spacer (ITS) region. Phylogenetic analysis of the 16S r RNA revealed three distinct clades. The clade we designate as Cylindrospermum sensu stricto contained all five of the foundational species, C. maius, C. stagnale, C. licheniforme, C. muscicola, and C. catenatum. In addition to these taxa, three species new to science in this clade were described: C. badium, C. moravicum, and C. pellucidum. Our evidence indicated that Cronbergia is a later synonym of Cylindrospermum. The phylogenetic position of Cylindrospermum within the Nostocaceae was not clearly resolved in our analyses. Cylindrospermum is unusual among cyanobacterial genera in that the morphological diversity appears to be more evident than sequence divergence. Taxa were clearly separable using morphology, but had very high percent similarity among ribosomal sequences. Given the high diversity we noted in this study, we conclude that there is likely much more diversity remaining to be described in this genus. [ABSTRACT FROM AUTHOR]

An original and convenient domino route to natural nostoclides I and II has been developed using a two-step sequence consisting of a copper-catalyzed tandem reaction associated with Suzuki cross-coupling. The methodology employed for this total synthesis appeared to be an interesting and sufficiently flexible tool to allow the synthesis of numerous analogues of these nostoclides. [ABSTRACT FROM AUTHOR]

Nodularia spumigena is a filamentous diazotrophic cyanobacterium that forms blooms in brackish water bodies. This cyanobacterium produces linear and cyclic peptide protease inhibitors which are thought to be part of a chemical defense against grazers. Here we show that N. spumigena produces structurally novel members of the aeruginosin family of serine protease inhibitors. Extensive chemical analyses including NMR demonstrated that the aeruginosins are comprised of an N-terminal short fatty acid chain, L-Tyr, L-Choi and L-argininal and in some cases pentose sugar. The genome of N. spumigena CCY9414 contains a compact 18-kb aeruginosin gene cluster encoding a peptide synthetase with a reductive release mechanism which offloads the aeruginosins as reactive peptide aldehydes. Analysis of the aeruginosin and spumigin gene clusters revealed two different strategies for the incorporation of N-terminal protecting carboxylic acids. These results demonstrate that strains of N. spumigena produce aeruginosins and spumigins, two families of structurally similar linear peptide aldehydes using separate peptide synthetases. The aeruginosins were chemically diverse and we found 11 structural variants in 16 strains from the Baltic Sea and Australia. Our findings broaden the known structural diversity of the aeruginosin peptide family to include peptides with rare N-terminal short chain (C2–C10) fatty acid moieties. [ABSTRACT FROM AUTHOR]

Nodularia spumigena is a filamentous diazotrophic cyanobacterium that forms blooms in brackish water bodies. This cyanobacterium produces linear and cyclic peptide protease inhibitors which are thought to be part of a chemical defense against grazers. Here we show that N. spumigena produces structurally novel members of the aeruginosin family of serine protease inhibitors. Extensive chemical analyses including NMR demonstrated that the aeruginosins are comprised of an N-terminal short fatty acid chain, L-Tyr, L-Choi and L-argininal and in some cases pentose sugar. The genome of N. spumigena CCY9414 contains a compact 18-kb aeruginosin gene cluster encoding a peptide synthetase with a reductive release mechanism which offloads the aeruginosins as reactive peptide aldehydes. Analysis of the aeruginosin and spumigin gene clusters revealed two different strategies for the incorporation of N-terminal protecting carboxylic acids. These results demonstrate that strains of N. spumigena produce aeruginosins and spumigins, two families of structurally similar linear peptide aldehydes using separate peptide synthetases. The aeruginosins were chemically diverse and we found 11 structural variants in 16 strains from the Baltic Sea and Australia. Our findings broaden the known structural diversity of the aeruginosin peptide family to include peptides with rare N-terminal short chain (C2–C10) fatty acid moieties. [ABSTRACT FROM AUTHOR]

Akinetes are spore-like nonmotile cells that differentiate from vegetative cells of filamentous cyanobacteria from the order Nostocales. They play a key role in the survival and distribution of these species and contribute to their perennial blooms. Various environmental factors were reported to trigger the differentiation of akinetes including light intensity and quality, temperature, and nutrient deficiency. Here, we report that deprivation of potassium ion ( K+) triggers akinete development in the cyanobacterium Aphanizomenon ovalisporum. Akinetes formation is initiated 3 d-7 d after an induction by K+ depletion, followed by 2-3 weeks of a maturation process. Akinete formation occurs within a restricted matrix of environmental conditions such as temperature, light intensity or photon flux. Phosphate is essential for akinete maturation and P-limitation restricts the number of mature akinetes. DNA replication is essential for akinete maturation and akinete development is limited in the presence of Nalidixic acid. While our results unequivocally demonstrated the effect of K+ deficiency on akinete formation in laboratory cultures of A. ovalisporum, this trigger did not cause Cylindrospermopsis raciborskii to produce akinetes. Anabaena crassa however , produced akinetes upon potassium deficiency, but the highest akinete concentration was achieved at conditions that supported vegetative growth. It is speculated that an unknown internal signal is associated with the cellular response to K+ deficiency to induce the differentiation of a certain vegetative cell in a trichome into an akinete. A universal stress protein that functions as mediator in K+ deficiency signal transduction cascade, may communicate between the lack of K+ and akinete induction. [ABSTRACT FROM AUTHOR]

Akinetes are spore-like nonmotile cells that differentiate from vegetative cells of filamentous cyanobacteria from the order Nostocales. They play a key role in the survival and distribution of these species and contribute to their perennial blooms. Various environmental factors were reported to trigger the differentiation of akinetes including light intensity and quality, temperature, and nutrient deficiency. Here, we report that deprivation of potassium ion ( K+) triggers akinete development in the cyanobacterium Aphanizomenon ovalisporum. Akinetes formation is initiated 3 d-7 d after an induction by K+ depletion, followed by 2-3 weeks of a maturation process. Akinete formation occurs within a restricted matrix of environmental conditions such as temperature, light intensity or photon flux. Phosphate is essential for akinete maturation and P-limitation restricts the number of mature akinetes. DNA replication is essential for akinete maturation and akinete development is limited in the presence of Nalidixic acid. While our results unequivocally demonstrated the effect of K+ deficiency on akinete formation in laboratory cultures of A. ovalisporum, this trigger did not cause Cylindrospermopsis raciborskii to produce akinetes. Anabaena crassa however , produced akinetes upon potassium deficiency, but the highest akinete concentration was achieved at conditions that supported vegetative growth. It is speculated that an unknown internal signal is associated with the cellular response to K+ deficiency to induce the differentiation of a certain vegetative cell in a trichome into an akinete. A universal stress protein that functions as mediator in K+ deficiency signal transduction cascade, may communicate between the lack of K+ and akinete induction. [ABSTRACT FROM AUTHOR]

Ford Lake in southeastern Michigan has a history of midsummer cyanobacterial blooms marked by a regular succession from heterocystousAphanizomenon flos-aquaeto nonheterocystousMicrocystis aeruginosa. Nitrogen (N)-fixingAphanizomenonhas an advantage following seasonal thermal stratification because nitrate is consumed by assimilative uptake in the epilimnion and by anaerobic respiration in the anoxic hypolimnion. If nitrate levels increase, however,MicrocystissucceedsAphanizomenon. Bioassays corroborated the importance of nitrate toMicrocystissuccess in late summer. Experimental releases of hypolimnetic water from the hydroelectric outlet dam before anoxia developed in 2006 destabilized the water column without altering lake volume and promoted a diatom bloom rather than cyanobacteria. To establish that the experimental manipulation was reproducible, we followed 2006 with a control year and then a second experimental year. In 2007, experimental manipulation was not performed, water was withdrawn from the epilimnion alone, and the lake reverted to historical dominance by firstAphanizomenonand thenMicrocystis. In 2008 we again commenced hypolimnetic discharge at onset of thermal stratification, and a sequence of diatom blooms resulted, demonstrating that community transformation first produced in 2006 was reproducible. The algal community again became transformed from cyanobacteria to diatoms, but overall biomass did not change. Bioassays demonstrated thatAphanizomenonbecame P limited during diatom dominance. Cyanobacterial blooms were postponed until after termination of the whole lake experiment and subsequent diatom decline. [ABSTRACT FROM AUTHOR]

Abstract: Accumulation and breakthrough of several potentially toxic cyanobacterial species within drinking water treatment plants (DWTP) have been reported recently. The objectives of this project were to test the efficiency of different treatment barriers in cyanobacterial removal. Upon observation of cyanobacterial blooms, intensive sampling was conducted inside a full scale DWTP at raw water, clarification, filtration and oxidation processes. Samples were taken for microscopic speciation/enumeration and microcystins analysis. Total cyanobacteria cell numbers exceeded World Health Organisation and local alert levels in raw water (6,90,000 cells/mL). Extensive accumulation of cyanobacteria species in sludge beds and filters, and interruption of treatment were observed. Aphanizomenon cells were poorly coagulated and they were not trapped efficiently in the sludge. It was also demonstrated that Aphanizomenon cells passed through and were not retained over the filter. However, Microcystis, Anabaena, and Pseudanabaena cells were adequately removed by clarification and filtration processes. The breakthrough of non toxic cyanobacterial cells into DWTPs could also result in severe treatment disruption leading to plant shutdown. Application of intervention threshold values restricted to raw water does not take into consideration the major long term accumulation of potentially toxic cells in the sludge and the risk of toxins release. Thus, a sampling regime inside the plant adapted to cyanobacterial occurrence and intensity is recommended. [Copyright &y& Elsevier]

Nodularia spumigena is a filamentous diazotrophic cyanobacterium that dominates the annual late summer cyanobacterial blooms in the Baltic Sea. But N. spumigena also is common in brackish water bodies worldwide, suggesting special adaptation allowing it to thrive at moderate salinities. A draft genome analysis of N. spumigena sp. CCY9414 yielded a single scaffold of 5,462,271 nucleotides in length on which genes for 5,294 proteins were annotated. A subsequent strand-specific transcriptome analysis identified more than 6,000 putative transcriptional start sites (TSS). Orphan TSSs located in intergenic regions led us to predict 764 non-coding RNAs, among them 70 copies of a possible retrotransposon and several potential RNA regulators, some of which are also present in other N2-fixing cyanobacteria. Approximately 4% of the total coding capacity is devoted to the production of secondary metabolites, among them the potent hepatotoxin nodularin, the linear spumigin and the cyclic nodulapeptin. The transcriptional complexity associated with genes involved in nitrogen fixation and heterocyst differentiation is considerably smaller compared to other Nostocales. In contrast, sophisticated systems exist for the uptake and assimilation of iron and phosphorus compounds, for the synthesis of compatible solutes, and for the formation of gas vesicles, required for the active control of buoyancy. Hence, the annotation and interpretation of this sequence provides a vast array of clues into the genomic underpinnings of the physiology of this cyanobacterium and indicates in particular a competitive edge of N. spumigena in nutrient-limited brackish water ecosystems. [ABSTRACT FROM AUTHOR]

Upper Klamath Lake in southwestern Oregon has experienced harmful algal blooms of the nitrogen-fixing cyanobateriumAphanizomenon flos-aquaefor 5 decades. The appearance ofA. flos-aquaecoincided with loss of wetlands to agricultural use starting at the end of the 19th century. Plant degradation produces colored dissolved organic matter (CDOM) or humic substances that affect algal and cyanobacterial growth. We conducted a series of controlled laboratory assays and anin situlimnocorral experiment to assess the effectiveness of plant materials that contribute high levels of CDOM upon decomposition (i.e., barley straw, barley straw extracts, marsh water, and wetland plants) to suppress growth of the cyanobacteriumA. flos-aquae. Our results indicate that the application of barley straw or dried wetland plants were most effective at suppressing growth or causing mortality ofA. flos-aquae. Mortality was dependent on the amount of CDOM released and incident ultraviolet (UV) light. We hypothesize that mortality is due to the well-known production of reactive oxygen species from the absorption of UV light by CDOM. In general, direct application of plant material under high UV exposure resulted in near completeA. flos-aquaemortality within 24 hours. Because the mortality was rapid, these results are consistent with toxicosis and not the binding of essential nutrients. We suggest that fringing wetlands may play an important role in regulating harmful cyanobacterial blooms by providing CDOM and that this role should be considered when determining wetland value. [ABSTRACT FROM AUTHOR]