Description of four new filamentous cyanobacterial taxa from freshwater habitats in the Azores Archipelago.

Simple filamentous cyanobacteria comprise a diverse and polyphyletic group of species, primarily in the orders Leptolyngbyales and Oscillatoriales, that need more sampling to improve their taxonomy. Oceanic islands, such as the Azores archipelago, present unique habitats and biogeographic conditions that harbor an unknown range of diversity of microorganisms. Filamentous cyanobacteria isolated from aquatic habitats in the Azores and maintained in the BACA culture collection were described using morphology, both light and transmission electron microscopy, ecology, and genetic data of the 16S rRNA gene sequences and 16S-23S Internal Transcribed Spacer (ITS) rRNA region secondary structure. Our analyses revealed two new monophyletic genera: Tumidithrix elongata gen. sp. nov. (Pseudanabaenaceae) and Radiculonema aquaticum gen. sp. nov. (Leptolyngbyaceae). In addition, two new species Leptodesmis lacustris sp. nov. (Leptolyngbyaceae) and Pycnacronema lacustrum sp. nov. (Wilmottiaceae) are reported as the first aquatic species for these genera. The description of these new taxa and the genetic study of an isolate of Leptodesmis alaskaensis from the Azores followed the polyphasic approach, identifying diacritical features. Our results reinforce the need for taxonomic studies on cyanobacteria from less-studied habits and geographic regions, which have a potential for new taxa description.

Empirical testing of cryoconite granulation: Role of cyanobacteria in the formation of key biogenic structure darkening glaciers in polar regions.

Cryoconite, the dark sediment on the surface of glaciers, often aggregates into oval or irregular granules serving as biogeochemical factories. They reduce a glacier's albedo, act as biodiversity hotspots by supporting aerobic and anaerobic microbial communities, constitute one of the organic matter (OM) sources on glaciers, and are a feeder for micrometazoans. Although cryoconite granules have multiple roles on glaciers, their formation is poorly understood. Cyanobacteria are ubiquitous and abundant engineers of cryoconite hole ecosystems. This study tested whether cyanobacteria may be responsible for cryoconite granulation as a sole biotic element. Incubation of Greenlandic, Svalbard, and Scandinavian cyanobacteria in different nutrient availabilities and substrata for growth (distilled water alone and water with quartz powder, furnaced cryoconite without OM, or powdered rocks from glacial catchment) revealed that cyanobacteria bind mineral particles into granules. The structures formed in the experiment resembled those commonly observed in natural cryoconite holes: they contained numerous cyanobacterial filaments protruding from aggregated mineral particles. Moreover, all examined strains were confirmed to produce extracellular polymeric substances (EPS), which suggests that cryoconite granulation is most likely due to EPS secretion by gliding cyanobacteria. In the presence of water as the only substrate for growth, cyanobacteria formed mostly carpet-like mats. Our data empirically prove that EPS-producing oscillatorialean cyanobacteria isolated from the diverse community of cryoconite microorganisms can form granules from mineral substrate and that the presence of the mineral substrate increases the probability of the formation of these important and complex biogeochemical microstructures on glaciers.

Anti-Inflammatory Dysidazirine Carboxylic Acid from the Marine Cyanobacterium Caldora sp. Collected from the Reefs of Fort Lauderdale, Florida.

Dysidazirine carboxylic acid (1) was isolated from the lipophilic extract of a collection of the benthic marine cyanobacterium Caldora sp. from reefs near Fort Lauderdale, Florida. The planar structure of this new compound was determined by spectroscopic methods and comparisons between HRMS and NMR data with its reported methyl ester. The absolute configuration of the single chiral center was determined by the conversion of 1 to the methyl ester and the comparison of its specific rotation data with the two known methyl ester isomers, 2 and 3. Molecular sequencing with 16S rDNA indicated that this cyanobacterium differs from Caldora penicillata (Oscillatoriales) and represents a previously undocumented and novel Caldora species. Dysidazirine (2) showed weak cytotoxicity against HCT116 colorectal cancer cells (IC50 9.1 µM), while dysidazirine carboxylic acid (1) was non-cytotoxic. Similar cell viability patterns were observed in RAW264.7 cells with dysidazirine only (2), displaying cytotoxicity at the highest concentration tested (50 µM). The non-cytotoxic dysidazirine carboxylic acid (1) demonstrated anti-inflammatory activity in RAW264.7 cells stimulated with LPS. After 24 h, 1 inhibited the production of NO by almost 50% at 50 µM, without inducing cytotoxicity. Compound 1 rapidly decreased gene expression of the pro-inflammatory gene iNOS after 3 h post-LPS treatment and in a dose-dependent manner (IC50 ~1 µM); the downregulation of iNOS persisted at least until 12 h.

Untangling filamentous marine cyanobacterial diversity from the coast of South Florida with the description of Vermifilaceae fam. nov. and three new genera: Leptochromothrix gen. nov., Ophiophycus gen. nov., and Vermifilum gen. nov.

Benthic cyanobacterial mats are an integral component of aquatic communities in tropical marine waters. These mats can develop into massive nuisances at risk of expansion due to climate change. The extent of diversity occurring within these mats, still remains largely unexplored, especially in Florida. To reveal this diversity, coastal environments of South Florida were sampled and subsequently processed for isolation and systematic identification. Three new genera are proposed based on the molecular phylogeny, morphology, and ecology. These new genera are characterized by discoid cells and homocytous, unbranched filaments without sheaths. Individual genus morphological differences include either rounded bent, rounded, or conical rounded apical cells. A unique molecular fingerprint including a base pair insert within the 16S rRNA gene sequence and genetic similarities facilitates the delimitation of a novel family Vermifilaceae. Using the polyphasic approach, our research presents three new genera and four new species of marine cyanobacteria inhabiting coastal ecosystems of South Florida.

Pathological effects of cyanobacteria on sea fans in southeast Florida.

In early August 2008, observations by divers indicated that sea fans, particularly Gorgonia ventalina, Gorgonia flabellum, and Iciligorgia schrammi, were being covered by benthic filamentous cyanobacteria. From August 2008 through January 2009 and again in April 2009, tissue samples from a targeted G. ventalina colony affected by cyanobacteria and from a nearby, apparently healthy (without cyanobacteria) control colony, were collected monthly for histopathological examination. The primary cellular response of the sea fan to overgrowth by cyanobacteria was an increase in the number of acidophilic amoebocytes (with their granular contents dispersed) that were scattered throughout the coenenchyme tissue. Necrosis of scleroblasts and zooxanthellae and infiltration of degranulated amoebocytes were observed in the sea fan surface tissues at sites overgrown with cyanobacteria. Fungal hyphae in the axial skeleton were qualitatively more prominent in cyanobacteria-affected sea fans than in controls.

Nonheterocytous cyanobacteria from Brazilian saline-alkaline lakes.

Saline-alkaline lakes are extreme environments that limit the establishment and development of life. The Nhecolândia, a subregion of the Pantanal wetland in Brazil, is characterized by the existence of ~500 saline-alkaline lakes, which support an underexplored and rich diversity of microorganisms. In this study, unicellular and homocytous cyanobacteria from five saline-alkaline lakes were accessed by culture-dependent approaches. Morphological evaluation and analyses of near complete sequences (~1400 nt) of the 16S rRNA genes were applied for phylogenetic and taxonomic placement. This polyphasic approach allowed for the determination of the taxonomic position of the isolated strains into the following genera: Cyanobacterium, Geminocystis, Phormidium, Leptolyngbya, Limnothrix, and Nodosilinea. In addition, fourteen Pseudanabaenales and Oscillatoriales representatives of putative novel taxa were found. These sequences fell into five new clades that could correspond to new generic units of the Pseudanabaenaceae and Phormidiaceae families.

Corrigendum: The survivor strain: Isolation and characterization of Phormidium yuhuli AB48, a filamentous phototactic cyanobacterium with biotechnological potential.

[This corrects the article DOI: 10.3389/fbioe.2022.932695.].

Genome sequence of freshwater nontoxigenic Limnoraphis associated with microcystin-producing blooms.

A sample from a 2019 cyanobacterial bloom in a freshwater reservoir in eastern Oregon, USA, was used to produce a metagenome from which the complete, circular 7.3 Mbp genome of Limnoraphis sp. WC205 was assembled. The Limnoraphis sp. WC205 genome contains gas vesicle genes, genes for N2-fixation and genes for both phycocyanin- and phycoerythrin-containing phycobilisomes. Limnoraphis was present in Willow Creek Reservoir throughout the summer and fall, coexisting with various other cyanobacteria in blooms that were associated with microcystin. The absence of cyanotoxin genes from the Limnoraphis sp. WC205 genome showed this cyanobacterium to be non-toxigenic, although it is predicted to produce cyanobactins closely related to Microcystis aeruginosa microcyclamides. DNA sequence corresponding to the Microcystis mcyG gene identified Microcystis as the microcystin producer in this lake.

The survivor strain: isolation and characterization of Phormidium yuhuli AB48, a filamentous phototactic cyanobacterium with biotechnological potential.

Despite their recognized potential, current applications of cyanobacteria as microbial cell factories remain in early stages of development. This is partly due to the fact that engineered strains are often difficult to grow at scale. This technical challenge contrasts with the dense and highly productive cyanobacteria populations thriving in many natural environments. It has been proposed that the selection of strains pre-adapted for growth in industrial photobioreactors could enable more productive cultivation outcomes. Here, we described the initial morphological, physiological, and genomic characterization of Phormidium yuhuli AB48 isolated from an industrial photobioreactor environment. P. yuhuli AB48 is a filamentous phototactic cyanobacterium with a growth rate comparable to Synechocystis sp. PCC 6803. The isolate forms dense biofilms under high salinity and alkaline conditions and manifests a similar nutrient profile to Arthrospira platensis (Spirulina). We sequenced, assembled, and analyzed the P. yuhuli AB48 genome, the first closed circular isolate reference genome for a member of the Phormidium genus. We then used cultivation experiments in combination with proteomics and metabolomics to investigate growth characteristics and phenotypes related to industrial scale cultivation, including nitrogen and carbon utilization, salinity, and pH acclimation, as well as antibiotic resistance. These analyses provide insight into the biological mechanisms behind the desirable growth properties manifested by P. yuhuli AB48 and position it as a promising microbial cell factory for industrial-scale bioproduction[221, 1631].

Description of new filamentous toxic Cyanobacteria (Oscillatoriales) colonizing the sulfidic periphyton mat in marine mangroves.

In this multidisciplinary study, we combined morphological, physiological, and phylogenetic approaches to identify three dominant water bloom-forming Cyanobacteria in a tropical marine mangrove in Guadeloupe (French West Indies). Phylogenetic analysis based on 16S rRNA gene sequences place these marine Cyanobacteria in the genera Oscillatoria (Oscillatoria sp. clone gwada, strain OG) or Planktothricoides ('Candidatus Planktothricoides niger' strain OB and 'Candidatus Planktothricoides rosea' strain OP; both provisionally novel species within the genus Planktothricoides). Bioassays showed that 'Candidatus Planktothricoides niger' and 'Candidatus Planktothricoides rosea' are toxin-producing organisms. This is the first report of the characterization of Cyanobacteria colonizing periphyton mats of a tropical marine mangrove. We describe two novel benthic marine species and provide new insight into Oscillatoriaceae and their potential role in marine sulfide-rich environments such as mangroves.