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Abstract: Biological hydrogen production is an ideal system for three main reasons i) forms a renewable energy source, ii) gives clean fuel and iii) serves as a good supplement to oil reserves. The major challenges faced in biological hydrogen production are the presence of uptake hydrogenase and lack of sustainability in the cyanobacterial hydrogen production system. Three different marine cyanobacterial species viz. Leptolyngbya valderiana BDU 20041, Dichothrix baueriana BDU 40481 and Nostoc calcicola BDU 40302 were studied for their potential use in hydrogen production. Among these, L. valderiana BDU 20041, was found to produce hydrogen even in 100% nitrogen atmosphere which was 85% of the hydrogen produced in argon atmosphere. This is the first report of such a high rate of production of hydrogen in a nitrogen atmosphere by a cyanobacterium, which makes it possible to develop sustained hydrogen production systems. L. valderiana BDU 20041, a dark hydrogen producer uses the reductant essentially supplied by the respiratory pathway for hydrogen production. Using inhibitors, this organism was found to produce hydrogen due to the activities of both nitrogenase and bidirectional hydrogenase, while it had no ‘uptake’ hydrogenase activity. The other two organisms though had low levels of bidirectional hydrogenase, possessed considerable ‘uptake’ hydrogenase activity and hence could not release much hydrogen either in argon or nitrogen atmosphere. [ABSTRACT FROM AUTHOR]

In this paper we report the metabolism of hexosamines and the cellular compartmentalization of glycoconjugates in the cyanobacterium Leptolyngbya VRUC 135 by using d-[U-14C]glucosamine as tracer. Glycoproteins as well as lipopolysaccharides were detected in the cell wall, membrane and buffer-soluble polymers. Evidence is also reported on the presence of lipopolysaccharides as released polymers. Abbreviation: RPs, released polymers [ABSTRACT FROM AUTHOR]

Abstract: Ruidera Pools Natural Park, Spain, constitutes one of the most representative systems of carbonate precipitation in Europe. The prokaryotic community of a dry modern stromatolite recovered from the park has been analyzed by molecular techniques that included denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene clone library analysis, together with microscopic observations from the sample and cultures. Ribosomal RNA was directly extracted to study the putatively active part of the microbial community present in the sample. A total of 295 16S rRNA gene sequences were analyzed. Libraries were dominated by sequences related to Cyanobacteria, most frequently to the genus Leptolyngbya. A diverse and abundant assemblage of non-cyanobacterial sequences was also found, including members of Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Acidobacteria, Planctomycetes and Chloroflexi groups. No amplification was obtained when using archaeal primers. The results showed that at the time of sampling, when the pool was dry, the bacterial community of the stromatolites was dominated by groups of highly related Cyanobacteria, including new groups that had not been previously reported, although a high diversity outside this phylogenetic group was also found. The results indicated that part of the Cyanobacteria assemblage was metabolically active and could thus play a role in the mineralization processes inside the stromatolites. [Copyright &y& Elsevier]

Cyanobacteria that grow above seawater salinity at temperatures above 45°C have rarely been studied. Cyanobacteria of this type of thermo-halophilic extremophile were isolated from siliceous crusts at 40–45°C in a geothermal seawater lagoon in southwest Iceland. Iceland Clone 2e, a Leptolyngbya morphotype, was selected for further study. This culture grew only at 45–50°C, in medium ranging from 28 to 94 g L−1 TDS, It showed 3 doublings 24 h−1 under continuous illumination. This rate at 54°C was somewhat reduced, and death occurred at 58°C. A comparison of the 16S rDNA sequence with all others in the NCBI database revealed 2 related Leptolyngbya isolates from a Greenland hot spring (13–16 g L−1 TDS). Three other similar sequences were from Leptolyngbya isolates from dry, endolithic habitats in Yellowstone National Park. All 6 formed a phylogenetic clade, suggesting common ancestry. These strains shared many similarities to Iceland Clone 2e with respect to temperature and salinity ranges and optima. Two endolithic Leptolyngbya isolates, grown previously at 23°C in freshwater medium, grew well at 50°C but only in saline medium. This study shows that limited genotypic similarity may reveal some salient phenotypic similarities, even when the related cyanobacteria are from vastly different and remote habitats. [ABSTRACT FROM AUTHOR]

Black band disease (BBD) is a cyanobacteria-dominated microbial mat that migrates across living coral colonies lysing coral tissue and leaving behind exposed coral skeleton. The mat is sulfide-rich due to the presence of sulfate-reducing bacteria, integral members of the BBD microbial community, and the sulfide they produce is lethal to corals. The effect of sulfide, normally toxic to cyanobacteria, on the photosynthetic capabilities of five BBD cyanobacterial isolates of the genera Geitlerinema (3), Leptolyngbya (1), and Oscillatoria (1) and six non-BBD cyanobacteria of the genera Leptolyngbya (3), Pseudanabaena (2), and Phormidium (1) was examined. Photosynthetic experiments were performed by measuring the photoincorporation of [14C] NaHCO3 under the following conditions: (1) aerobic (no sulfide), (2) anaerobic with 0.5 mM sulfide, and (3) anaerobic with 0.5 mM sulfide and 10 μM 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU). All five BBD cyanobacterial isolates tolerated sulfide by conducting sulfide-resistant oxygenic photosynthesis. Five of the non-BBD cyanobacterial isolates did not tolerate sulfide, although one Pseudanabaena isolate continued to photosynthesize in the presence of sulfide at a considerably reduced rate. None of the isolates conducted anoxygenic photosynthesis with sulfide as an electron donor. This is the first report on the physiology of a culture of Oscillatoria sp. found globally in BBD. [ABSTRACT FROM AUTHOR]

A previously undescribed, filamentous, nonheterocystous cyanobacterium was isolated from the South China Sea. The nonbranching and nonmotile filaments had well-defined sheaths of variable thickness. Trichomes were 1.1–1.5 gm in diameter, while individual cells ranged from 1.2 to 2.4 gm in length under culturing conditions. Thylakoids within individual cells were peripheral and appeared to become confluent at one end of the cell. Cells did not contain gas vacuoles. Cultures grew under a wide range of conditions, including salinities ranging from freshwater to 60 ppt of sodium chloride. Nonaxenic cultures could be grown indefinitely (for at least 2 years) in media devoid of any combined nitrogen source but grew much more rapidly in the presence of ammonium or nitrate ions. A unique feature of this organism was the presence, under dim light, of well-defined multicellular structures (nodules), distributed at irregular intervals along the filaments. Nodules were highly variable in shape and size, with each nodule constructed of a region of a filament tightly folded and wrapped into a discrete unit and surrounded by a firm common sheath. The internal structure of cells within nodules appeared identical to the structures of cells occurring along other portions of the filament. Comparisons of 16S rDNA, the 16S-23S internal transcribed spacer (ITS) sequence, and morphological characteristics of this strain to corresponding features of other cyanobacteria indicate that it is a member of the genus Leptolyngbya. Differences in DNA sequences and isolation habitat of this organism, along with the occurrence of nodules, indicate that it is not closely related to the type species, L. boryana, and should be assigned a distinct specific epithet. We propose the name Leptolyngbya nodulosa for this organism. [ABSTRACT FROM AUTHOR]

Epilithic phototrophic biofilms develop inside Roman Necropolis and Catacombs on rock surfaces exposed to artificial light sources and are composed by a microbial consortium dominated by cyanobacteria. In this work, six non-axenic cultures ofLeptolyngbyasp. strains isolated from biofilms from different Roman hypogea and maintained in cultures from 11 to 20 years were analysed along with their associated bacteria isolated in culture. The employment of PCR-fingerprinting techniques, using HIP1 and ERIC derived primers, allowed the clustering in three groups of the six Leptolyngbya strains and the typing of their isolated bacteria. The bacterial fingerprinting patterns were in agreement with the 16S rRNA gene sequencing and showed the presence inLeptolyngbyaisolates ofPseudomonas, Stenotrophomonas, AgrobacteriumandBacillusrepresentatives that were detected also in biofilms sampled from catacombs. [ABSTRACT FROM AUTHOR]

Inhibitory effects of brefeldin A (BFA) on the functioning of secretory systems has been extensively investigated in eukaryotic cells. In this study we report, for the first time, the in vivo effect of 50 and 100?µg?ml ?–?1 BFA on the biosynthesis of exo- and cell wall-polysaccharides in the cyanobacterium, Leptolyngbya VRUC 135, isolated from Roman hypogea (archaeological underground chambers). The drug inhibited the synthesis and the translocation of both exo- and cell wall-polysaccharides. This inhibitory effect could be due to direct or indirect alterations in membrane organization and, consequently, membrane function. [ABSTRACT FROM AUTHOR]

Abstract: Due to the irreversible inhibition of nitrogenase by O2, N2 fixation is incompatible with the oxygenic photosynthesis of cyanobacteria. These organisms have therefore evolved various strategies for growing diazotrophically. One group of N2-fixing cyanobacteria has specialized cells, heterocysts, which contain the nitrogenase, lack the oxygenic photosystem II, and are virtually anoxic inside as the result of respiratory activity and a thick glycolipid cell wall. The hetR gene encodes a serine protease which is thought to be involved in the regulation of heterocyst development and in DNA binding. Although hetR is also present in many non-heterocystous N2-fixing cyanobacteria, its function in these organisms is unknown. In this study, hetR sequences of the N2-fixing, non-heterocystous cyanobacterium Trichodesmium spp. and related genera were examined for signatures of selection. In parsimony- or distance-based hetR phylogenies, the filamentous non-heterocystous cyanobacteria Symploca sp. and Leptolyngbya sp. were closest to Trichodesmium sp. However, accommodating molecular attributes of hetR such as nucleotide frequencies and rate heterogeneity in phylogenetic analyses suggested that many other genera could not be excluded as sister taxa of Trichodesmium. Maximum likelihood analysis of the dN/dS ratio (ω) showed that—irrespective of the use of Symploca, Leptolyngbya, or more distant taxa as an outgroup—the lineage between an outgroup and Trichodesmium (ω 1=0.02–0.05) and a lineage leading to Trichodesmium erythraeum (ω 1=0.02) were under much stronger purifying selection than the other lineages in Trichodesmium (ω 0=0.13–0.32). Although the results from the maximum likelihood analyses are most trustworthy because of codon usage bias in Trichodesmium, the results from a simpler tree-based McDonald–Kreitman test were in general agreement. Due to their quite different assumptions, the combination of these two methods of analysis circumvents multiple testing which, in general, is problematic when using branch models. Although the causal selective forces underlying the substitution patterns in hetR have not yet been identified, these findings parallel the variety of physiological, molecular, and behavioral differences in cyanobacteria related to N2 fixation. The heterogeneity of selection pressures in Trichodesmium is more surprising, because multiple adaptation mechanisms have not been described in this genus. [Copyright &y& Elsevier]

A new genus of moderately halophilic, moderately halotolerant and moderately thermophilic cyanobacteria with very thin trichomes is described. The four strains included in this genus were isolated from benthic microbial mats in a man-made hypersaline pond. Trichomes were around 1 µm thick, with small constrictions at the cross-walls and diffluent colorless sheaths. Thylakoids were parallel to the cell wall, but thylakoids and nucleoid were often excentrically arranged within the cytoplasm with respect to the main trichome axis. Strains grew at between 3.2 and 12–15% (w/v) salinity with optima between 3.2 and 12%. They showed lower temperature limits around 20 °C and upper limits between 45 and 50 °C, with optima between 28 and 45–50 °C. Carotenoid and mycosporine amino-acid complements were identical among strains. Phylogenetic analyses based on 16S rRNA gene sequence showed that all strains were closely related (99% or higher similarity) and distantly related to other cyanobacteria (91% or lower similarity). We propose the new genus and species Halomicronema excentricum for these strains. The type strain is TFEP1. [ABSTRACT FROM AUTHOR]

Biocrust cyanobacteria are ubiquitous organisms in dryland environments that can enhance soil stability and improve nutrient conditions in reconstructed or disturbed soils. Despite the demonstrated benefits of cyanobacterial inoculation for promoting soil fertility, there is limited knowledge about the impacts of introducing cultured cyanobacteria on the indigenous microbial communities. Here, we conducted a microcosm experiment under controlled conditions using indigenous biocrust cyanobacteria and locally sourced topsoil substrate commonly used in dryland restoration in the Australian arid zone. We inoculated the topsoil with a consortium composed of Leptolyngbya sp. and Scytonema sp. cyanobacteria, to assess the effects of the inoculated cyanobacteria on (i) the soil chemical properties, i.e., pH, electrical conductivity (EC), total organic carbon (TOC), and nitrogen (TN) of the inoculated topsoil, (ii) the early formation of an artificial soil biocrust and iii) the composition and diversity of the resident bacterial community. Our results showed that the inoculated cyanobacterial consortia decreased the EC, but changes in the TOC and TN were not significant after 80 days. A higher content of chlorophyll a in the inoculated samples compared to the control, confirmed the survival of the cyanobacterial inoculants after 80 days. The inoculated cyanobacteria promoted gypsum formation on the soil surface indicating that they are actively modifying the upper layers of the soil profile and improving habitability. Although immediately after inoculation cyanobacteria dominated the abundance of bacterial phylotypes, these were replaced by other phyla such as Actinobacteria, after 80 days. The Shannon diversity and Simpson diversity indexes between control and inoculated soils differed at the time of inoculation but were similar at the end of the experiment. These results suggest that, in the short term, the introduced cyanobacteria do not significantly affect the native resident bacterial communities and are capable of colonizing the topsoil without affecting the natural community. [ABSTRACT FROM AUTHOR]

Microsatellites (simple sequence repeats, SSRs) are ubiquitously distributed in almost all known genomes. Here, the first investigation was designed to examine the SSRs and compound microsatellites (CSSRs) in genomes of Leptolyngbya-like strains. The results disclosed diversified patterns of distribution, abundance, density, and diversity of SSRs and CSSRs in genomes, indicating that they may be subject to rapid evolutionary change. The numbers of SSRs and CSSRs were extremely unevenly distributed among genomes, ranging from 11,086 to 24,000 and from 580 to 1865, respectively. Dinucleotide SSRs were the most abundant category in 31 genomes, while the other 15 genomes followed the pattern: mono- > di- > trinucleotide SSRs. The patterns related to SSRs and CSSRs showed differences among phylogenetic groups. Both SSRs and CSSRs were overwhelmingly distributed in coding regions. The numbers of SSRs and CSSRs were significantly positively correlated with genome size (p < 0.01) and negatively correlated with GC content (p < 0.05). Moreover, the motif (A/C)n and (AG)n was predominant in mononucleotide and dinucleotide SSRs, and unique motifs of CSSRs were identified in 39 genomes. This study provides the first insight into SSRs and CSSRs in genomes of Leptolyngbya-like strains and will be useful to understanding their distribution, predicting their function, and tracking their evolution. Additionally, the identified SSRs may provide an evolutionary advantage of fast adaptation to environmental changes and may play an important role in the cosmopolitan distribution of Leptolyngbya strains to globally diverse niches. [ABSTRACT FROM AUTHOR]

In order to determine the nearly complete 16S rRNA gene sequences of cyanobacteria originating from nonaxenic cultures, a cyanobacterium-specific oligonucleotide probe was developed to distinguish polymerase chain reaction (PCR) products of the cyanobacterial rRNA operons from those resulting from amplification of contaminating bacteria. Using this screening method the 16S rRNA genes of four nonaxenic filamentous cyanobacterial strains belonging to the genera Leptolyngbya and Oscillatoria were cloned and sequenced. For the genus Leptolyngbya, the 16S rRNA sequence of the axenic strain PCC 73110 was also determined. Phylogenetic trees were constructed based on complete and partial sequences. The results show that the strains Leptolyngbya foveolarum Komárek 1964/112, Leptolyngbya sp. VRUC 135 Albertano 1985/1, and Leptolyngbya boryanum PCC 73110 belong to the same cluster. Strain Oscillatoria cf. corallinae SAG 8.92, which contains the rare photosynthetic pigment CU-phycoerythrin, is not closely related to other CU-phycoerythrin-containing cyanobacteria. Oscillatoria agardhii CYA 18, which is a representative of planktonic Oscillatoria species that form toxic blooms in Norwegian inland waters, has no close relatives in the tree. [ABSTRACT FROM AUTHOR]

This study combines electrocoagulation (EC) and cyanobacteria-based cultivation for the two-step treatment of brewery wastewater (BW), with the aim to develop a viable alternative to conventional activated sludge technology. The first step applied EC as a pretreatment method, using different electrode materials (aluminum and iron), to remove color and some pollutant load from the BW. After 30 min of EC treatment, decolorization of BW exceeded 80% for both electrode materials and a 100% reduction of total suspended solids was achieved. In the second step, the electrochemically pretreated BW was used as substrate for a cyanobacteria-based cultivation. After 15 days of cultivation total biomass concentrations (containing up to 50% carbohydrates) reached 525.0 mg L−1 and 740.0 mg L−1, for aluminum- and iron-pretreated BW, respectively. Moreover, the cyanobacterial community assimilated most of the residual aluminum and iron produced by the EC process, therefore verifying its bioremediation abilities. The combined process also proved effective at pollutant removal (89.1%, 100%, 89.4%, 98.5% and 91.6% of nitrate, ammonium, total Kjeldahl nitrogen, total phosphorus and chemical oxygen demand, respectively). The two-stage treatment method proposed could offer a promising alternative to conventional BW treatment technologies as it combines both efficiency and sustainability. Image 1 • Electrocoagulation effectively removes suspended solids that cause turbidity. • Cyanobacterial consortium removes most residual organic and inorganic pollutants. • Electrocoagulation pretreatment with iron electrodes promotes cyanobacterial growth. • Cyanobacteria accumulate residual iron/aluminum, performing effluent bioremediation. • Biomass is a potential bioethanol feedstock due to its high carbohydrate content. [ABSTRACT FROM AUTHOR]

Artificial, non-sterile, microalgal biofilms present a promising biotechnological avenue for the production of valuable biomass, biofuels and biochemicals while simultaneously engaging in photosynthetic carbon capture. Here we use a psbA amplicon library and high-throughput 16S and 18S rRNA gene sequencing to investigate the effects of time and CO 2 concentration on the composition and community dynamics of photoautotrophically grown microalgal biofilms pre-conditioned with wastewater and heavily seeded with the green alga Scenedesmus obliquus. While biomass increased in a stable, linear manner, our analysis revealed that the photoautotrophic community dramatically changed over time. Photoautotrophs such as Chorella and the cyanobacterium Leptolyngbya , presumably seeded from the wastewater, rapidly established as constituents of the biofilm while the seed species was far less dominant than anticipated. With time, photoautotrophic diatoms and dinoflagellates also established themselves as constituents of the biofilm. Low CO 2 (0.04% v/v) favoured the early proliferation of cyanobacteria while high CO 2 (12%) delayed, but did not prevent the proliferation. In addition, a phylogenetically diverse array of heterotrophic α-, β- and γ-proteobacteria, Bacteriodetes along with a selection of eukaryotic microorganisms inhabited the biofilms. Principal coordinate analyses reveal unique clustering patterns indicating that the composition of the initial and the final microbial communities were distinctly different from one another. Alpha diversity measures indicated that the 16S (prokaryotic) community peaked around day 10 / 11 at both 0.04% and 12% CO 2. However, unlike the 18S (eukaryotic) community where diversity was at a maximum at the end of the 26-day time-course, prokaryotic diversity achieved minimum values, particularly for biofilms grown at 0.04% CO 2 , where the cyanobacteria proliferated. In spite of the planned experimental design bias toward S. obliquus biofilm growth, the collective data suggest that selection against undesirable microorganism also needs to be incorporated as an essential feature of biofilm photobioreactor design and operation. • Non-sterile Scenedesmus -seeded biofilm biomass increased with time and [CO 2. • The biofilm photoautotrophic community dramatically changed over time. • The seed species declined in rDNA sequence abundance. • Cyanobacteria, Chlorophytes and diatoms increased • A complex, dynamic microbial biofilm community arose including potential grazers. [ABSTRACT FROM AUTHOR]

Leptolyngbya is known to be used for human purposes, including for biofuel production. Therefore, it is important to study the physiology of these microorganisms. This study is expected to provide information on the temperature of growth ability of Leptolyngbya HS-16 and Leptolyngbya HS-36, so that storage conditions of culture space in subsequent research can be arranged to prevent these strains from dying or not growing well. In the utilization of cyanobacteria, a clear physiological characterization of the cyanobacteria is required. Temperature is one of the major factors affecting the growth of cyanobacteria. The growth differences between cyanobacteria strains Leptolyngbya HS-16 and Leptolyngbya HS-36 which were incubated in 20 °C, 35 °C, and 50 °C had been studied. Those strains were isolated from Gunung Pancar (Leptolyngbya HS-16) and Maribaya (Leptolyngbya HS-36) hot springs which located in West Java, Indonesia. The water temperature of habitat was 69 °C (Gunung Pancar) and 42 °C (Maribaya). Those strains were grown in batch culture methods for 21 days in BG-11 medium. This research aims to determine the best growth temperature of Leptolyngbya HS-16 and Leptolyngbya HS-36 based on the biomass weight of chlorophyll content. The result showed that the biomass weight and chlorophyll content in 35 °C of Leptolyngbya HS-16 and Leptolyngbya HS-36 were the highest. Both Leptolyngbya were likely thermotolerant cyanobacteria and had optimum cultured temperature 35 °C. There was no correlation between biomass weight and chlorophyll of Leptolyngbya HS-16 and Leptolyngbya HS-36. Further research should be focus on utilizing Leptolyngbya on various photobioreactor systems and biofuel development due their ability to growth optimally in that temperature. [ABSTRACT FROM AUTHOR]

The use of cyanobacteria in biological wastewater treatment technologies can greatly reduce operation costs by combining wastewater bioremediation and production of lipid suitable as biodiesel feedstock. In this work, an attached growth system was employed to achieve the above-mentioned dual objective using a mixed microbial culture dominated by Leptolyngbya and Limnothrix species in diverse heterotrophic consortia. Kinetic experiments on different initial pollutant concentrations were carried out to determine the ability of the established culture to remove organic load (expressed by d-COD, dissolved-Chemical Oxygen Demand), N and P from agroindustrial wastewaters (dairy, winery and raisin). Biomass and oil productivity were determined. It was found that significant removal rates of nutrients were achieved in all the wastewaters examined, especially in that originated from winery in which the highest d-COD removal rate (up to 97.4%) was observed. The attached microbial biomass produced in winery wastewater contained 23.2% lipid/biomass, wt/wt, which was satisfying. The growth in the dairy wastewater yielded the highest attached biomass productivity (5.03 g m−2 day−1) followed by the mixed effluent of winery-raisin (4.12 g m−2 day−1) and the winery wastewater (3.08 g m−2 day−1). The produced microbial lipids contained high percentages of saturated and mono-unsaturated fatty acids (over 89% in total lipids) in all substrates examined. We conclude that the proposed attached growth photobioreactor system can be considered an effective wastewater treatment system that simultaneously produces microbial lipids suitable as biodiesel feedstock. [ABSTRACT FROM AUTHOR]

The genus Leptolyngbya includes morphotypes with thin cells and simple morphology, and is one of the most common cyanobacterial genera found in a wide range of environments. In many cases, however, the morphotypes assigned to this genus do not share a common ancestor based on 16S rRNA gene phylogeny, which has led to the description of novel genera, such as Nodosilinea, Oculatella, Pantanalinema, Alkalinema, Thermoleptolyngbya, Onodrimia, Timaviella and Toxifilum. Thus, four novel isolates, with a comparable morphology to Leptolyngbya, were recovered from the Amazon and Solimões rivers. The novel 16S rRNA gene sequences obtained from these strains were placed together as a new and distinct phylogenetic lineage that is more closely related to the clusters embracing the genera Nodosilinea, Haloleptolyngbya and Halomicronema than to the genus Leptolyngbya. Additionally, these novel 16S rRNA gene sequences showed similarity values lower than 95 % compared with those from the most phylogenetic related groups and/or established genera. Altogether, these results supported the erection of a novel genus, named Amazoninema, to accommodate the novel isolates. Likewise, a comparison of their 16S rRNA gene sequences revealed similarities higher than 99.8 %, indicating that they belong to a single species, which was corroborated by analysing their 16S-23S internal transcribed spacer regions and unique Box-B helix pattern. Few studies have been undertaken to uncover the cultured diversity of cyanobacteria from Amazonia, and to our knowledge, this is the first cyanobacteria genus erected, considering morphotypes isolated exclusively from Brazilian Amazonian rivers.

The cyanobacteria are a diverse, ancient lineage of oxygenic, phototrophic bacteria. Ubiquitous in nearly all ecosystems, the alpha-level diversity of these organisms lags behind other algal lineages due to a perceived dearth of phylogenetically useful characters. Recent phylogenetic studies of species within the genus Leptolyngbya have demonstrated that this is a polyphyletic assemblage. One group of strains that fits within the current circumscription of Leptolyngbya is genetically and phylogenetically distinct from Leptolyngbya sensu stricto. Members of this clade possess both a morphological synapomorphy and shared 16S-23S internal transcribed spacer (ITS) secondary structure, allowing the diagnosis of the new cyanobacterial genus Nodosilinea. Members of this genus are united by the unique ability to form nodules along the length of the filament. This trait has been previously observed only in the species Leptolyngbya nodulosa Z. Li et J. Brand, and we have chosen this species as the generitype of Nodosilinea. We currently recognize four species in the genus, N. nodulosa (Z. Li et J. Brand) comb. nov., N. bijugata (Kong.) comb. nov., N. conica sp. nov., and N. epilithica sp. nov., (© 2011 Phycological Society of America.)