Phylogenetic inferences reveal a large extent of novel biodiversity in chemically rich tropical marine cyanobacteria

Chemical Control of Snail Vectors as an Integrated Part of a Strategy for the Elimination of Schistosomiasis-A Review of the State of Knowledge and Future Needs

WHO promotes the implementation of a comprehensive strategy to control and eliminate schistosomiasis through preventive chemotherapy, snail control, clean water supply, improved sanitation, behaviour change interventions, and environmental management. The transmission of schistosomiasis involves infected definitive hosts (humans or animals) excreting eggs that hatch (miracidia), which infect freshwater snail vectors (also referred to as intermediate snail hosts) living in marshlands, ponds, lakes, rivers, or irrigation canals. Infective larvae (cercariae) develop within the snail, which, when released, may infect humans and/or animals in contact with the water. Snail control aims to interrupt the transmission cycle of the disease by removing the vector snails and, by so doing, indirectly improves the impact of the preventive chemotherapy by reducing reinfection. Snail control was, for many years, the only strategy for the prevention of schistosomiasis before preventive chemotherapy became the primary intervention. Snails can be controlled through various methods: environmental control, biological control, and chemical control. The chemical control of snails has proven to be the most effective method to interrupt the transmission of schistosomiasis. The current review aims to describe the vector snails of human schistosomiasis, present the chemicals and strategies for the control of snails, the challenges with the implementation, and the future needs. Snail control can play a key role in reducing schistosomiasis transmission and, thus, complements other interventions for disease control. There is a need to develop new molluscicide products or new formulations and methods of applications for existing molluscicides that would target snail vectors more specifically.

Unique Initiation and Termination Mechanisms Involved in the Biosynthesis of a Hybrid Polyketide-Nonribosomal Peptide Lyngbyapeptin B Produced by the Marine Cyanobacterium Moorena bouillonii

Lyngbyapeptin B is a hybrid polyketide-nonribosomal peptide isolated from particular marine cyanobacteria. In this report, we carried out genome sequence analysis of a producer cyanobacterium Moorena bouillonii to understand the biosynthetic mechanisms that generate the unique structural features of lyngbyapeptin B, including the (E)-3-methoxy-2-butenoyl starter unit and the C-terminal thiazole moiety. We identified a putative lyngbyapeptin B biosynthetic (lynB) gene cluster comprising nine open reading frames that include two polyketide synthases (PKSs: LynB1 and LynB2), four nonribosomal peptide synthetases (NRPSs: LynB3, LynB4, LynB5, and LynB6), a putative nonheme diiron oxygenase (LynB7), a type II thioesterase (LynB8), and a hypothetical protein (LynB9). In vitro enzymatic analysis of LynB2 with methyltransferase (MT) and acyl carrier protein (ACP) domains revealed that the LynB2 MT domain (LynB2-MT) catalyzes O-methylation of the acetoacetyl-LynB2 ACP domain (LynB2-ACP) to yield (E)-3-methoxy-2-butenoyl-LynB2-ACP. In addition, in vitro enzymatic analysis of LynB7 revealed that LynB7 catalyzes the oxidative decarboxylation of (4R)-2-methyl-2-thiazoline-4-carboxylic acid to yield 2-methylthiazole in the presence of Fe²⁺ and molecular oxygen. This result indicates that LynB7 is responsible for the last post-NRPS modification to give the C-terminal thiazole moiety in lyngbyapeptin B biosynthesis. Overall, we identified and characterized a new marine cyanobacterial hybrid PKS-NRPS biosynthetic gene cluster for lyngbyapeptin B production, revealing two unique enzymatic logics.

Cryptic Diversity of Black Band Disease Cyanobacteria in Siderastrea siderea Corals Revealed by Chemical Ecology and Comparative Genome-Resolved Metagenomics

Black band disease is a globally distributed and easily recognizable coral disease. Despite years of study, the etiology of this coral disease, which impacts dozens of stony coral species, is not completely understood. Although black band disease mats are predominantly composed of the cyanobacterial species Roseofilum reptotaenium, other filamentous cyanobacterial strains and bacterial heterotrophs are readily detected. Through chemical ecology and metagenomic sequencing, we uncovered cryptic strains of Roseofilum species from Siderastrea siderea corals that differ from those on other corals in the Caribbean and Pacific. Isolation of metabolites from Siderastrea-derived Roseofilum revealed the prevalence of unique forms of looekeyolides, distinct from previously characterized Roseofilum reptotaenium strains. In addition, comparative genomics of Roseofilum strains showed that only Siderastrea-based Roseofilum strains have the genetic capacity to produce lasso peptides, a family of compounds with diverse biological activity. All nine Roseofilum strains examined here shared the genetic capacity to produce looekeyolides and malyngamides, suggesting these compounds support the ecology of this genus. Similar biosynthetic gene clusters are not found in other cyanobacterial genera associated with black band disease, which may suggest that looekeyolides and malyngamides contribute to disease etiology through yet unknown mechanisms.

Roholtiella volcanica sp. nov., a New Species of Cyanobacteria from Kamchatkan Volcanic Soils

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.

Cyanobacterial secondary metabolites towards improved commercial significance through multiomics approaches

Cyanobacteria are ubiquitous photosynthetic prokaryotes responsible for the oxygenation of the earth's reducing atmosphere. Apart from oxygen they are producers of a myriad of bioactive metabolites with diverse complex chemical structures and robust biological activities. These secondary metabolites are known to have a variety of medicinal and therapeutic applications ranging from anti-microbial, anti-viral, anti-inflammatory, anti-cancer, and immunomodulating properties. The present review discusses various aspects of secondary metabolites viz. biosynthesis, types and applications, which highlights the repertoire of bioactive constituents they harbor. Majority of these products have been produced from only a handful of genera. Moreover, with the onset of various OMICS approaches, cyanobacteria have become an attractive chassis for improved secondary metabolites production. Also the intervention of synthetic biology tools such as gene editing technologies and a variety of metabolomics and fluxomics approaches, used for engineering cyanobacteria, have significantly enhanced the production of secondary metabolites.

Spirovetivane- and Eudesmane-Type Sesquiterpenoids Isolated from the Culture Media of Two Cyanobacterial Strains

As part of a study examining polar metabolites produced by cyanobacterial strains, we examined media extracts of a Calothrix sp. (strain R-3-1) and a Scytonema sp. (strain U-3-3). The cell mass of each was separated from the media, and HP20 resin was added for adsorption of secreted metabolites, a relatively unexplored area of cyanobacterial chemistry. HPLC-UV-LCMS-guided isolation led to the discovery of seven sesquiterpenoid compounds with five new, one known, and one previously isolated as the methyl ester. Through a complement of 1D and 2D NMR spectroscopic techniques, the planar structures and relative configurations of the seven compounds were elucidated. Spironostoic acid (1), 11,12-didehydrospironostoic acid (2), and 12-hydroxy-2-oxo-11-epi-hinesol (4) are spirovetivane-type compounds from R-3-1, while stigolone (5), 11R,12-dihydroxystigolone (6), and 11S,12-dihydroxystigolone (7) are three eudesmane-type compounds from U-3-3. Circular dichroism was utilized to decipher the absolute configurations of new compounds 1, 2, 4, 5, 6, and 7. Due to the structural variety observed among the spirovetivane- and eudesmane-type compounds in the literature and often a lack of clarity in how determinations were made, computational spectra and model compounds were used to support the interpretation of ECD and NMR spectra. A straightforward process to determine the configuration of these systems is presented.

Micrococcin P1 and P2 from Epibiotic Bacteria Associated with Isolates of Moorea producens from Kenya

Epibiotic bacteria associated with the filamentous marine cyanobacterium Moorea producens were explored as a novel source of antibiotics and to establish whether they can produce cyclodepsipeptides on their own. Here, we report the isolation of micrococcin P1 (1) (C₄₈H₄₉N₁₃O₉S₆; obs. m/z 1144.21930/572.60381) and micrococcin P2 (2) (C₄₈H₄₇N₁₃O₉S₆; obs. m/z 1142.20446/571.60370) from a strain of Bacillus marisflavi isolated from M. producens’ filaments. Interestingly, most bacteria isolated from M. producens’ filaments were found to be human pathogens. Stalked diatoms on the filaments suggested a possible terrestrial origin of some epibionts. CuSO₄·5H₂O assisted differential genomic DNA isolation and phylogenetic analysis showed that a Kenyan strain of M. producens differed from L. majuscula strain CCAP 1446/4 and L. majuscula clones. Organic extracts of the epibiotic bacteria Pseudoalteromonas carrageenovora and Ochrobactrum anthropi did not produce cyclodepsipeptides. Further characterization of 24 Firmicutes strains from M. producens identified extracts of B. marisflavi as most active. Our results showed that the genetic basis for synthesizing micrococcin P1 (1), discovered in Bacillus cereus ATCC 14579, is species/strain-dependent and this reinforces the need for molecular identification of M. producens species worldwide and their epibionts. These findings indicate that M. producens-associated bacteria are an overlooked source of antimicrobial compounds.

Diversity of bioactive compound content across 71 genera of marine, freshwater, and terrestrial cyanobacteria

Cyanobacterial blooms have increased in frequency, distribution, and intensity due to climate change and anthropogenic nutrient input. The release of bioactive compounds accumulated in these blooms can affect the health of humans and the environment. The co-occurrence of bioactive metabolites is well-documented in bloom samples from marine and freshwater ecosystems, with fewer reports from unialgal isolates. Cyanobacteria also are important terrestrial ecosystem components, especially in drylands, but reports on bioactive molecules from terrestrial cyanobacteria are sparse. This study determined bioactive metabolite profiles for 71 genera of cyanobacteria from seven orders isolated from freshwater (12 genera), marine (15 genera), and terrestrial (44 genera) habitats originally. Cultures were harvested for bioactive metabolites when entering the late-exponential phase for all 157 strains, and 33 were sampled at both early and late exponential phases. Bioactive metabolites were analyzed using an ultra high performance/pressure liquid chromatography in-line with a time-of-flight mass spectrometer. Overall, 12 bioactive classes of the 28 identified were ubiquitous in all samples. On average, each freshwater genus produced ∼12 bioactive classes, whereas each marine genus contained > 4 bioactive classes, and each terrestrial genus contained ∼6 bioactive classes. While 10 of 12 freshwater genera produced at least 10 bioactive classes, only a single genus each from marine and terrestrial habitats had the same number of bioactive classed accumulated. Aeruginosin was found in 58 of 71 total genera, carmabin in 51 of 71 genera, and anabaenopeptin in 48 of 71 genera. Chemotaxonomic use of these secondary metabolites may help resolve higher-level genetic classification(s). An additional growth curve experiment showed that bioactive metabolites were produced at both early and late exponential growth phases. The bioactive metabolite accumulation pattern between early and late exponential phases differed by bioactive classes, genera, and habitats. This survey of 55 bioactive classes in cyanobacteria isolated from freshwater, marine, and terrestrial habitats (71 genera) provides as one of the first systematic bioactive metabolite profiles for cyanobacteria, which should be useful in environmental and drinking water management. Further, it offers novel insights about the toxin potential of selected terrestrial cyanobacteria.

Shotgun metagenomic sequencing reveals the full taxonomic, trophic, and functional diversity of a coral reef benthic cyanobacterial mat from Bonaire, Caribbean Netherlands

Anthropogenic forcing is spurring cyanobacterial proliferation in aquatic ecosystems worldwide. While planktonic cyanobacterial blooms have received substantial research attention, benthic blooms of mat-forming cyanobacteria have received considerably less attention, especially benthic mat blooms on coral reefs. Resultingly, numerous aspects of coral reef benthic cyanobacterial bloom ecology remain unknown, including underlying biodiversity in the mat communities. Most previous characterizations of coral reef cyanobacterial mat composition have only considered the cyanobacterial component. Without an unbiased characterization of full community diversity, we cannot predict whole-community response to anthropogenic inputs or effectively determine appropriate mitigation strategies. Here, we advocate for the implementation of shotgun sequencing techniques to study coral reef cyanobacterial mats worldwide, utilizing a case study of a coral reef benthic cyanobacterial mat sampled from the island of Bonaire, Caribbean Netherlands. Read-based taxonomic profiling revealed that Cyanobacteria was present at only 47.57% relative abundance in a coral reef cyanobacterial mat, with non-cyanobacterial members of the sampled mat community, including diatoms (0.78%), fungi (0.25%), Archaea (0.34%), viruses (0.08%), and other bacteria (45.78%), co-dominating the community. We found numerous gene families for regulatory systems and for functional pathways (both aerobic and anaerobic). These gene families were involved in community coordination; photosynthesis; nutrient scavenging; and the cycling of sulfur, nitrogen, phosphorous, and iron. We also report bacteriophage (including prophage) sequences associated with this subtidal coral reef cyanobacterial mat, which could contribute to intra-mat nutrient cycling and bloom dynamics. Overall, our results suggest that Cyanobacteria-focused analysis of coral reef cyanobacterial mats underestimates mat diversity and fails to capture community members possessing broad metabolic potential for intra-mat nutrient scavenging, recycling, and retention that likely contribute to the contemporary success of cyanobacterial mats on reefs. We advocate for increased collaboration between microbiologists and coral reef ecologists to unite insights from each discipline and improve efforts to understand mat ecology.

The occurrence of Affixifilum gen. nov. and Neolyngbya (Oscillatoriaceae) in South Florida (USA), with the description of A. floridanum sp. nov. and N. biscaynensis sp. nov

South Florida (USA) has a subtropical to tropical climate with an extensive and diverse coastline that supports the growth of benthic cyanobacterial mats (BCMs). These BCMs are widespread and potentially house numerous bioactive compounds; however, the extent of the cyanobacterial diversity within these mats remains largely unknown. To elucidate this diversity, BCMs from select locations in South Florida were sampled and isolated into unicyanobacterial cultures for morphological and molecular studies. Phylogenetic relationships of isolated taxa were assessed using the markers 16S rRNA and 16S-23S rRNA ITS by both maximum likelihood and Bayesian inference. We propose Affixifilum gen. nov. based on morphological characteristics and the 16S rRNA phylogeny. Two species are included: Affixifilum granulosum comb nov. (=Neolyngbya granulosa) found in Brazil and Florida (USA) and A. floridanum sp. nov. Several other features, including pair-wise distance of 16S rRNA and 16S-23S rRNA ITS, 16S-23S rRNA ITS secondary structure, morphology, and ecology, provide support for Affixifilum. We also propose the transfer of Lyngbya regalis to Neolyngbya as N. regalis comb. nov. and include the description of one novel species, N. biscaynensis sp. nov.

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.

The Chemistry, Biochemistry and Pharmacology of Marine Natural Products from Leptolyngbya, a Chemically Endowed Genus of Cyanobacteria

Leptolyngbya, a well-known genus of cyanobacteria, is found in various ecological habitats including marine, fresh water, swamps, and rice fields. Species of this genus are associated with many ecological phenomena such as nitrogen fixation, primary productivity through photosynthesis and algal blooms. As a result, there have been a number of investigations of the ecology, natural product chemistry, and biological characteristics of members of this genus. In general, the secondary metabolites of cyanobacteria are considered to be rich sources for drug discovery and development. In this review, the secondary metabolites reported in marine Leptolyngbya with their associated biological activities or interesting biosynthetic pathways are reviewed, and new insights and perspectives on their metabolic capacities are gained.

The Marine Sponge Petrosia ficiformis Harbors Different Cyanobacteria Strains with Potential Biotechnological Application

Marine cyanobacteria are a source of bioactive natural compounds, with a wide range of biotechnological applications. However, information on sponge-associated cyanobacteria are relatively scarce to date. In this paper, we carried out the morphological and molecular characterization of eight cyanobacterial strains, previously isolated from the Mediterranean sponge Petrosia ficiformis, and evaluated their biological activities on epithelial- and neuron-like cultured cells of human and murine origin. The new analysis allowed maintaining the assignment of three strains (Cyanobium sp., Leptolyngbya ectocarpi, and Synechococcus sp.), while two strains previously identified as Synechococcus sp. and Leptolyngbya sp. were assigned to Pseudanabaena spp. One strain, i.e., ITAC104, and the ITAC101 strain corresponding to Halomicronema metazoicum, shared extremely high sequence identity, practically representing two clones of the same species. Finally, for only one strain, i.e., ITAC105, assignment to a specific genus was not possible. Concerning bioactivity analyses, incubation of cyanobacterial aqueous cell supernatants induced variable responses in cultured cells, depending on cell type, with some of them showing toxic activity on human epithelial-like cells and no toxic effects on human and rat neuron-like cells. Future investigations will allow to better define the bioactive properties of these cyanobacteria strains and to understand if they can be useful for (a) therapeutic purpose(s).

Assessment of the Chemical Diversity and Potential Toxicity of Benthic Cyanobacterial Blooms in the Lagoon of Moorea Island (French Polynesia)

In the last decades, an apparent increase in the frequency of benthic cyanobacterial blooms has occurred in coral reefs and tropical lagoons, possibly in part because of global change and anthropogenic activities. In the frame of the survey of marine benthic cyanobacteria proliferating in the lagoon of Moorea Island (French Polynesia), 15 blooms were collected, mainly involving three species—Anabaena sp.1, Lyngbya majuscula and Hydrocoleum majus-B. Their chemical fingerprints, obtained through high performance liquid chromatography combined with UV detection and mass spectrometry (HPLC-UV-MS) analyses, revealed a high extent of species-specificity. The chemical profile of Anabaena sp.1 was characterized by three major cyclic lipopeptides of the laxaphycin family, whereas the one of L. majuscula was characterized by a complex mixture including tiahuramides, trungapeptins and serinol-derived malyngamides. Toxicity screening analyses conducted on these cyanobacterial samples using Artemia salina and mouse neuroblastoma cell-based (CBA-N2a) cytotoxic assays failed to show any toxicity to a degree that would merit risk assessment with regard to public health. However, the apparently increasing presence of blooms of Lyngbya, Hydrocoleum, Anabaena or other benthic cyanobacteria on coral reefs in French Polynesia encourages the implementation of ad hoc monitoring programs for the surveillance of their proliferation and potential assessment of associated hazards.

Cyanobacterial bioactive metabolites-A review of their chemistry and biology

Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.

Global phylogeography of toxic cyanobacteria Moorea producens reveals distinct genetic partitioning influenced by Proterozoic glacial cycles

Lyngbya majuscula is a marine filamentous cyanobacteria belonging to the family Oscillatoriaceae. Recent phylogenetic analyses of L. majuscula have reclassified a subset of this species into various genera such as Moorea, Okeania and Dapis. From the genus Moorea, Moorea producens is a toxic invasive cyanobacterium that produces bioactive secondary metabolites that can cause severe inflammation and blistering. Despite the global distribution of M. producens, little information is available on their origin, patterns of dispersal and population structure. In this study, the spatial population structure of M. producens was investigated using near-complete 16S rRNA sequences. Analysis of the global population of M. producens by Isolation by Distance and STRUCTURE revealed two significantly distinct cosmopolitan populations that were separated by a genetic break. Lineage-specific divergence estimates of 147 cyanobacterial taxa, based on a relaxed molecular clock indicated the first global emergence of M. producens during the Mesoarchean and a subsequent global recolonization during the Mesoproterozoic period. We conclude that the genetic discontinuity between both cosmopolitan populations is attributed to refugia associated with Proterozoic glacial cycles.

Experimental Approaches for the Evaluation of Allelopathic Interactions Between Hermatypic Corals and Marine Benthic Cyanobacteria in the Colombian Caribbean

Blooms of marine benthic cyanobacteria are recurrent in several locations at the Colombian Caribbean. In these events, cyanobacteria grow over the substrate and benthic organisms although their effect has not been fully assessed. This study evaluated interactions between cyanobacteria and hermatypic corals, in order to identify any deleterious effects that could be related to allelopathic mechanisms. Organic extracts from cyanobacteria collected in San Andres, Old Providence and Rosario islands were tested against embryos of the reef-building coral Orbicella annularis. The indirect effect of cyanobacterial extracts was also assessed by resuspending the extracts in seawater and monitoring polyp retraction and recovery of the coral Madracis mirabilis (=auretenra). Additionally, the effect of direct contact between cyanobacterial extracts and the coral Porites porites was assessed by incorporating cyanobacterial extracts into PhytagelTM gels and placed in direct contact with the coral. After 24, 48 and 72 h of exposure, chromatographic profiles of associated zooxanthellae was evaluated by HPLC. A deleterious effect on the zooxanthellae was evidenced by an increase in pheophytin, a degradation product from chlorophyll. The competitive abilities of algae and cyanobacteria should be considered as a constraint to reef restoration initiatives. Cyanobacteria have the ability to compete with corals due to their growth rates, defenses against herbivory and potentially allelopathic mechanisms.

Cyanobacterial bioactive metabolites-A review of their chemistry and biology

Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.

Cyanobacterial extract with serotonin receptor subtype 7 (5-HT7 R) affinity modulates depression and anxiety-like behavior in mice

Marine cyanobacteria represent a unique source in the field of drug discovery due to the secondary metabolites they produce and the structural similarity these compounds have to endogenous mammalian receptor ligands. A series of cyanobacteria were subjected to extraction, fractionation by column chromatography and screened for affinity against CNS targets with a focus on serotonin receptors (5-HTRs). Out of 276 fractions screened, 21% had activity at 5-HTRs and/or the 5-HT transporter (SERT). One sample, a cyanobacterium identified by 16S rRNA sequencing as Leptolyngbya from Las Perlas archipelago in Panama, contained a fraction with noted affinity for the 5-HT₇ receptor (5-HT₇ R). This fraction (DUQ0002I) was screened via intracerebroventricular (ICV) injections in mice using depression and anxiety assays including the forced swim, tail suspension, elevated zero maze, and light-dark preference tests. DUQ0002I decreased depression and anxiety-like behaviors in males and did not have effects in 5-HT₇ R knockout or female mice. Administration of DUQ0002I to the CA1 of the hippocampus induced antidepression-like, but not anxiolytic-like behaviors. Testing of further purified materials showed no behavioral effects, leading us to hypothesize that the behavioral effects are likely caused by a synergistic effect between multiple compounds in the fraction. Finally, DUQ0002I was used in a model of neuropathic pain with comorbid depression (spared nerve injury-SNI). DUQ0002I had a similar antidepressant effect in animals with SNI, suggesting a role for the 5-HT₇ R in the development of comorbid pain and depression. These results demonstrate the potential that cyanobacterial metabolites have in the field of neuropharmacognosy.

Uncovering cryptic diversity of Lyngbya: the new tropical marine cyanobacterial genus Dapis (Oscillatoriales)

Cyanobacteria comprise an extraordinarily diverse group of microorganisms and, as revealed by increasing molecular information, this biodiversity is even more extensive than previously estimated. In this sense, the cyanobacterial genus Lyngbya is a highly polyphyletic group composed of many unrelated taxa with morphological similarities. In this study, the new genus Dapis was erected from the genus Lyngbya, based on a combined molecular, chemical, and morphological approach. Herein, two new species of cyanobacteria are described: D. pleousa and D. pnigousa. Our analyses found these species to be widely distributed and abundant in tropical and subtropical marine habitats. Seasonally, both species have the ability to form extensive algal blooms in marine habitats: D. pleousa in shallow-water, soft bottom habitats and D. pnigousa on coral reefs below depths of 10 m. Electron microscopy showed that D. pleousa contains gas vesicles, a character not previously reported in Lyngbya. These gas vesicles, in conjunction with a mesh-like network of filaments that trap oxygen released from photosynthesis, provide this species with an unusual mechanism to disperse in coastal marine waters, allowing D. pleousa to be present in both benthic and planktonic forms. In addition, both D. pleousa and D. pnigousa contained nitrogen-fixing genes as well as bioactive secondary metabolites. Several specimens of D. pnigousa biosynthesized the secondary metabolite lyngbic acid, a molecule that has also been isolated from many other marine cyanobacteria. Dapis pleousa consistently produced the secondary metabolite malyngolide, which may provide a promising chemotaxonomic marker for this species.

Bloom dynamics and chemical defenses of benthic cyanobacteria in the Indian River Lagoon, Florida

Cyanobacterial blooms are predicted to become more prominent in the future as a result of increasing seawater temperatures and the continued addition of nutrients to coastal waters. Many benthic marine cyanobacteria have potent chemical defenses that protect them from top down pressures and contribute to the persistence of blooms. Blooms of benthic cyanobacteria have been observed along the coast of Florida and within the Indian River Lagoon (IRL), a biodiverse estuary system that spans 250km along Florida's east coast. In this study, the cyanobacterial bloom progression at three sites within the central IRL was monitored over the course of two summers. The blooms consisted of four unique cyanobacterial species, including the recently described Okeania erythroflocculosa. The cyanobacteria produced a range of known bioactive compounds including malyngolide, lyngbyoic acid, microcolins A-B, and desacetylmicrocolin B. Ecologically-relevant assays showed that malyngolide inhibited the growth of marine fungi (Dendryphiella salina and Lindra thalassiae); microcolins A-B and desacetylmicrocolin B inhibited feeding by a generalist herbivore, the sea urchin Lytechinus variegatus; and lyngbyoic acid inhibited fungal growth and herbivore feeding. These chemical defenses likely contribute to the persistence of cyanobacterial blooms in the IRL during the summer growing period.

New Peptides Isolated from Marine Cyanobacteria, an Overview over the Past Decade

Marine cyanobacteria are significant sources of structurally diverse marine natural products with broad biological activities. In the past 10 years, excellent progress has been made in the discovery of marine cyanobacteria-derived peptides with diverse chemical structures. Most of these peptides exhibit strong pharmacological activities, such as neurotoxicity and cytotoxicity. In the present review, we summarized peptides isolated from marine cyanobacteria since 2007.

Finding food: how marine invertebrates use chemical cues to track and select food

This review covers recent research on how marine invertebrates use chemical cues to find and select food.

Unique marine derived cyanobacterial biosynthetic genes for chemical diversity

Cyanobacteria are a prolific source of structurally unique and biologically active natural products that derive from intriguing biochemical pathways. Advancements in genome sequencing have accelerated the identification of unique modular biosynthetic gene clusters in cyanobacteria and reveal a wealth of unusual enzymatic reactions involved in their construction. This article examines several interesting mechanistic transformations involved in cyanobacterial secondary metabolite biosynthesis with a particular focus on marine derived modular polyketide synthases (PKS), nonribosomal peptide synthetases (NRPS) and combinations thereof to form hybrid natural products. Further, we focus on the cyanobacterial genus Moorea and the co-evolution of its enzyme cassettes that create metabolic diversity. Progress in the development of heterologous expression systems for cyanobacterial gene clusters along with chemoenzymatic synthesis makes it possible to create new analogs. Additionally, phylum-wide genome sequencing projects have enhanced the discovery rate of new natural products and their distinctive enzymatic reactions. Summarizing, cyanobacterial biosynthetic gene clusters encode for a large toolbox of novel enzymes that catalyze unique chemical reactions, some of which may be useful in synthetic biology.

Cylindrofridins A-C, Linear Cylindrocyclophane-Related Alkylresorcinols from the Cyanobacterium Cylindrospermum stagnale

A rapid and exhaustive one-step biomass extraction as well as an enrichment and cleanup procedure has been developed for HPLC-UV detection and quantification of closely related [7.7]paracyclophanes and structural derivatives based on a two-phase solvent system. The procedure has been validated using the biomass of the carbamidocyclophane- and cylindrocyclophane-producing cyanobacterium Nostoc sp. CAVN2 and was utilized to perform a screening comprising 102 cyanobacterial strains. As a result, three new cylindrocyclophane-related alkylresorcinols, cylindrofridins A-C (1-3), and known cylindrocyclophanes (4-6) were detected and isolated from Cylindrospermum stagnale PCC 7417. Structures of 1-3 were elucidated by a combination of 1D and 2D NMR experiments, HRMS, and ECD spectroscopy. Cylindrofridin A (1) is the first naturally occurring [7.7]paracyclophane-related monomeric derivative. In contrast, cylindrofridins B (2) and C (3) represent dimers related to 1. Due to chlorination at the alkyl carbon atom in 1-3, the site of [7.7]paracyclophane macrocycle formation, the cylindrofridins represent linearized congeners of the cylindrocyclophanes. Compounds 1-3 were not toxic against nontumorigenic HaCaT cells (IC50 values >25 μM) compared to the respective cylindrocyclophanes, but 1 was the only cylindrofridin showing moderate activity against methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pneumoniae with MIC values of 9 and 17 μM, respectively.

Amantelides A and B, Polyhydroxylated Macrolides with Differential Broad-Spectrum Cytotoxicity from a Guamanian Marine Cyanobacterium

Cytotoxicity-guided fractionation of a Guamanian cyanobacterial collection yielded the new compounds amantelides A (1) and B (2). These polyketides are characterized by a 40-membered macrolactone ring consisting of a 1,3-diol and contiguous 1,5-diol units and a tert-butyl substituent. Amantelide A (1) displayed potent cytotoxicity with submicromolar IC₅₀ against HT29 colorectal adenocarcinoma and HeLa cervical carcinoma cell lines. Acetylation of the hydroxy group at C-33 in 2 caused a close to 10-fold decrease in potency. Exhaustive acetylation of the hydroxy groups abrogated the antiproliferative activity of amantelide A (1) by 20-67-fold. Further bioactivity assessment of 1 against bacterial pathogens and marine fungi indicated a broad spectrum of bioactivity.

Almiramide D, cytotoxic peptide from the marine cyanobacterium Oscillatoria nigroviridis

Marine benthic cyanobacteria are widely known as a source of toxic and potentially useful compounds.These microorganisms have been studied from many Caribbean locations, which recently include locations in the Colombian Caribbean Sea. In the present study, six lipopeptides named almiramides D to H, together with the known almiramide B are identified from a mat characterized as Oscillatoria nigroviridis collected at the Island of Providence (Colombia, S.W. Caribbean Sea). The most abundant compounds, almiramides B and D were characterized by NMR and HRESIMS, while the structures of the minor compounds almiramides E to H were proposed by the analysis of their HRESIMS and MS2 spectra. Almiramides B and D were tested against six human cell lines including a gingival fibroblast cell line and five human tumor cell lines (A549, MDA-MB231, MCF-7, HeLa and PC3) showing a strong but not selective toxicity.

Caldora penicillata gen. nov., comb. nov. (cyanobacteria), a pantropical marine species with biomedical relevance

Many tropical marine cyanobacteria are prolific producers of bioactive secondary metabolites with ecological relevance and promising pharmaceutical applications. One species of chemically rich, tropical marine cyanobacteria that was previously identified as Symploca hydnoides or Symploca sp. corresponds to the traditional taxonomic definition of Phormidium penicillatum. In this study, we clarified the taxonomy of this biomedically and ecologically important cyanobacterium by comparing recently collected specimens with the original type material and the taxonomic description of P. penicillatum. Molecular phylogenetic analyses of the 16S rRNA gene and the 16S-23S internal transcribed spacer regions showed that P. penicillatum formed an independent clade sister to the genus Symploca, and distantly related to Phormidium and Lyngbya. We propose the new genus Caldora for this clade, with Caldora penicillata comb. nov. as the type species and designate as the epitype the recently collected strain FK13-1. Furthermore, the production of bioactive secondary metabolites among various geographically dispersed collections of C. penicillata showed that this species consistently produced the metabolite dolastatin 10 and/or the related compound symplostatin 1, which appear to be robust autapomorphic characters and chemotaxonomic markers for this taxon.

Combining Mass Spectrometric Metabolic Profiling with Genomic Analysis: A Powerful Approach for Discovering Natural Products from Cyanobacteria

An innovative approach was developed for the discovery of new natural products by combining mass spectrometric metabolic profiling with genomic analysis and resulted in the discovery of the columbamides, a new class of di- and trichlorinated acyl amides with cannabinomimetic activity. Three species of cultured marine cyanobacteria, Moorea producens 3L, Moorea producens JHB, and Moorea bouillonii PNG, were subjected to genome sequencing and analysis for their recognizable biosynthetic pathways, and this information was then compared with their respective metabolomes as detected by MS profiling. By genome analysis, a presumed regulatory domain was identified upstream of several previously described biosynthetic gene clusters in two of these cyanobacteria, M. producens 3L and M. producens JHB. A similar regulatory domain was identified in the M. bouillonii PNG genome, and a corresponding downstream biosynthetic gene cluster was located and carefully analyzed. Subsequently, MS-based molecular networking identified a series of candidate products, and these were isolated and their structures rigorously established. On the basis of their distinctive acyl amide structure, the most prevalent metabolite was evaluated for cannabinomimetic properties and found to be moderate affinity ligands for CB1.

Targeted natural products discovery from marine cyanobacteria using combined phylogenetic and mass spectrometric evaluation

Combined phylogenetic and HPLC-MS-based natural products dereplication methods aimed at identifying cyanobacterial collections containing the potent cytotoxins largazole, dolastatin 10, and symplostatin 1 were developed. The profiling of the phylogeny, chemical space, and antiproliferative activity of cyanobacterial collections served to streamline the prioritization of samples for the discovery of new secondary metabolites. The dereplication methods highlighted the biosynthetic potential and combinatorial pharmacology employed by marine cyanobacteria. We found that largazole was always coproduced with dolastatin 10 or with symplostatin 1 and consequently tested combinations of these agents against colon cancer cells. Combinatorial regimens of largazole and dolastatin 10 aimed at curbing the growth of HCT116 cancer cells showed cooperative activity.

Depsipeptide companeramides from a Panamanian marine cyanobacterium associated with the coibamide producer

Two new cyclic depsipeptides, companeramides A (1) and B (2), have been isolated from the phylogenetically characterized cyanobacterial collection that yielded the previously reported cancer cell toxin coibamide A (collected from Coiba Island, Panama). The planar structures of the companeramides, which contain 3-amino-2-methyl-7-octynoic acid (Amoya), hydroxy isovaleric acid (Hiva), and eight α-amino acid units, were established by NMR spectroscopy and mass spectrometry. The absolute configuration of each companeramide was assigned using a combination of Marfey's methodology and chiral-phase HPLC analysis of complete and partial hydrolysis products compared to commercial and synthesized standards. Companeramides A (1) and B (2) showed high nanomolar in vitro antiplasmodial activity but were not overtly cytotoxic to four human cancer cell lines at the doses tested.

Carriebowlinol, an antimicrobial tetrahydroquinolinol from an assemblage of marine cyanobacteria containing a novel taxon

A combined biodiversity- and bioassay-guided natural products discovery approach was used to explore new groups of marine cyanobacteria for novel secondary metabolites with ecologically relevant bioactivities. Phylogenetic analysis of cyanobacterial collections from Belize revealed a new taxon not previously well explored for natural products. The new alkaloid 5-hydroxy-4-(chloromethyl)-5,6,7,8-tetrahydroquinoline (1), named carriebowlinol, and the known compound lyngbic acid (2) were isolated from a nonpolar extract and identified by NMR and MS techniques. Compounds 1 and 2 inhibited the growth of pathogenic and saprophytic marine fungi, and 1 inhibited the growth of marine bacteria, suggesting an antimicrobial ecological function.

Toxic alkaloids in Lyngbya majuscula and related tropical marine cyanobacteria

The cyanobacterium Lyngbya majuscula is found in the littoral zone and to a depth of 30m in tropical, subtropical and temperate regions across the globe, as well as being an important contributor to coral reef ecosystems. This cyanobacterium produces a range of chemicals that may contribute to a variety of negative health outcomes including skin, eye and respiratory irritation. The toxic compounds, lyngbyatoxin A and debromoaplysiatoxin, have been implicated in acute dermatologic reactions in human swimmers, and experiments involving these two toxins show the formation of acute dermal lesions. We explore the reported distribution and health implications of L. majuscula, with reference to factors affecting bloom frequency. The likely implications of climate change upon the distribution of the organism, and frequency of blooms are also described.

Five chemically rich species of tropical marine cyanobacteria of the genus Okeania gen. nov. (Oscillatoriales, Cyanoprokaryota)

An adverse consequence of applying morphology-based taxonomic systems to catalog cyanobacteria, which generally are limited in the number of available morphological characters, is a fundamental underestimation of natural biodiversity. In this study, we further dissect the polyphyletic cyanobacterial genus Lyngbya and delineate the new genus Okeania gen. nov. Okeania is a tropical and subtropical, globally distributed marine group abundant in the shallow-water benthos. Members of Okeania are of considerable ecological and biomedical importance because specimens within this group biosynthesize biologically active secondary metabolites and are known to form blooms in coastal benthic environments. Herein, we describe five species of the genus Okeania: O. hirsuta (type species of the genus), O. plumata, O. lorea, O. erythroflocculosa, and O. comitata, under the provisions of the International Code of Nomenclature for Algae, Fungi, and Plants. All five Okeania species were morphologically, phylogenetically, and chemically distinct. This investigation provides a classification system that is able to identify Okeania spp. and predict their production of bioactive secondary metabolites.

Quantitative molecular networking to profile marine cyanobacterial metabolomes

Untargeted liquid chromatography-MS (LC-MS) is used to rapidly profile crude natural product (NP) extracts; however, the quantity of data produced can become difficult to manage. Molecular networking based on MS/MS data visualizes these complex data sets to aid their initial interpretation. Here, we developed an additional visualization step for the molecular networking workflow to provide relative and absolute quantitation of a specific compound in an extract. The new visualization also facilitates combination of several metabolomes into one network, and so was applied to an MS/MS data set from 20 crude extracts of cultured marine cyanobacteria. The resultant network illustrates the high chemical diversity present among marine cyanobacteria. It is also a powerful tool for locating producers of specific metabolites. In order to dereplicate and identify culture-based sources of known compounds, we added MS/MS data from 60 pure NPs and NP analogs to the 20-strain network. This dereplicated six metabolites directly and offered structural information on up to 30 more. Most notably, our visualization technique allowed us to identify and quantitatively compare several producers of the bioactive and biosynthetically intriguing lipopeptide malyngamide C. Our most prolific producer, a Panamanian strain of Okeania hirsuta (PAB10FEB10-01), was found to produce at least 0.024 mg of malyngamide C per mg biomass (2.4%, w/dw) and is now undergoing genome sequencing to access the corresponding biosynthetic machinery.

Emerging trends in the discovery of natural product antibacterials

This article highlights current trends and advances in exploiting natural sources for the deployment of novel and potent anti-infective countermeasures. The key challenge is to therapeutically target bacterial pathogens that exhibit a variety of puzzling and evolutionarily complex resistance mechanisms. Special emphasis is given to the strengths, weaknesses, and opportunities in the natural product antibacterial drug discovery arena, and to emerging applications driven by advances in bioinformatics, chemical biology, and synthetic biology in concert with exploiting bacterial phenotypes. These efforts have identified a critical mass of natural product antibacterial lead compounds and discovery technologies with high probability of successful implementation against emerging bacterial pathogens.