Cyanobacteria

Particle-Associated Bacterioplankton Communities Across the Red Sea

Pelagic particle-associated bacterioplankton play crucial roles in marine ecosystems, influencing biogeochemical cycling and ecosystem functioning. However, their diversity, composition, and dynamics remain poorly understood, particularly in unique environments such as the Red Sea. In this study, we employed eDNA metabarcoding to comprehensively characterise bacterioplankton communities associated with pelagic particles in a three-dimensional assessment spanning depths from the surface to a depth of 2300 m along the full length of the eastern Red Sea within the exclusive economic zone of the Kingdom of Saudi Arabia. Our results reveal a diverse assemblage of taxa, with Pseudomonadota, Cyanobacteriota, and Planctomycetota being the dominant phyla. We identified pronounced spatial variability in community composition among five major Red Sea geographical regions, with a third of all amplicon sequence variants being unique to the Southern Red Sea in contrast to a relatively homogenous distribution along the water column depth gradient. Our findings contribute to a deeper understanding of microbial ecology in the Red Sea and provide valuable insights into the factors governing pelagic particle-associated bacterioplankton communities in this basin.

Extraction, characterization and antioxidative potentials of UV-screening compound, mycosporine-like amino acids from epilithic cyanobacterium Lyngbya sp. HKAR - 15

Mycosporine-like amino acids (MAAs) are a unique class of UV-screening bioactive molecules with potent antioxidants and photoprotective properties, synthesized by various species of cyanobacteria in different habitats. The cyanobacterial biofilms play a crucial driver in the development of ecological communities. The current study examined the existence of the photoprotective MAAs in a novel epilithic cyanobacterium Lyngbya sp. strain HKAR-15 isolated from cyanobacterial biofilms on the rock surface. The isolated MAAs were identified, purified and characterized using UV-Vis spectroscopy, HPLC (High-Performance Liquid Chromatography), ESI-MS (Electrospray Ionization-Mass Spectrometry), FTIR (Fourier Transform Infrared Spectroscopy) and NMR (Nuclear Magnetic Resonance). The compounds were recognized as palythine (retention time (RT): 2.7 min; UV λmax: 320 nm; m/z: 245.02) and porphyra-334 (RT: 3.6 min; UV λmax: 334 nm; m/z: 347.1). FTIR spectroscopy analyses also revealed the presence of functional groups of both compounds. NMR spectroscopy analyses confirmed the presence of both palythine and porphyra-334. The UV-induced production of both MAAs was visualized under ultraviolet radiation (UVR) in contrast to the photosynthetically active radiation (PAR). The MAAs (palythine and porphyra-334) had a significant dose-dependent free radical scavenging capacity. The findings show that MAAs perform a dynamic role in the survival and photoprotection of cyanobacteria in hostile environments under high solar UV irradiances. These photoprotective compounds may have various biotechnological applications as well as role in the development of natural sunscreens.

Isolation, Characterization, Moisturization and Anti-HepG2 Cell Activities of a Novel Polysaccharide from Cyanobacterium aponinum

Polysaccharides from cyanobacteria are extensively reported for their complex structures, good biocompatibility, and diverse bioactivities, but only a few cyanobacterial species have been exploited for the biotechnological production of polysaccharides. According to our previous study, the newly isolated marine cyanobacterium Cyanobacterium aponinum SCSIO-45682 was a good candidate for polysaccharide production. This work provided a systematic study of the extraction optimization, isolation, structural characterization, and bioactivity evaluation of polysaccharides from C. aponinum SCSIO-45682. Results showed that the crude polysaccharide yield of C. aponinum reached 17.02% by hot water extraction. The crude polysaccharides showed a porous and fibrous structure, as well as good moisture absorption and retention capacities comparable to that of sodium alginate. A homogeneous polysaccharide (Cyanobacterium aponinum polysaccharide, CAP) was obtained after cellulose DEAE-52 column and Sephadex G-100 column purification. CAP possessed a high molecular weight of 4596.64 kDa. It was mainly composed of fucose, galactose, and galacturonic acid, with a molar ratio of 15.27:11.39:8.64. The uronic acid content and sulfate content of CAP was 12.96% and 18.06%, respectively. Furthermore, CAP showed an in vitro growth inhibition effect on human hepatocellular carcinoma (HepG2) cells. The above results indicated the potential of polysaccharides from the marine cyanobacterium C. aponinum SCSIO-45682 as a moisturizer and anticancer addictive applied in cosmetical and pharmaceutical industries.

Biogeographic distribution of five Antarctic cyanobacteria using large-scale k-mer searching with sourmash branchwater

Cyanobacteria form diverse communities and are important primary producers in Antarctic freshwater environments, but their geographic distribution patterns in Antarctica and globally are still unresolved. There are however few genomes of cultured cyanobacteria from Antarctica available and therefore metagenome-assembled genomes (MAGs) from Antarctic cyanobacteria microbial mats provide an opportunity to explore distribution of uncultured taxa. These MAGs also allow comparison with metagenomes of cyanobacteria enriched communities from a range of habitats, geographic locations, and climates. However, most MAGs do not contain 16S rRNA gene sequences, making a 16S rRNA gene-based biogeography comparison difficult. An alternative technique is to use large-scale k-mer searching to find genomes of interest in public metagenomes. This paper presents the results of k-mer based searches for 5 Antarctic cyanobacteria MAGs from Lake Fryxell and Lake Vanda, assigned the names Phormidium pseudopriestleyi FRX01, Microcoleus sp. MP8IB2.171, Leptolyngbya sp. BulkMat.35, Pseudanabaenaceae cyanobacterium MP8IB2.15, and Leptolyngbyaceae cyanobacterium MP9P1.79 in 498,942 unassembled metagenomes from the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA). The Microcoleus sp. MP8IB2.171 MAG was found in a wide variety of environments, the P. pseudopriestleyi MAG was found in environments with challenging conditions, the Leptolyngbyaceae cyanobacterium MP9P1.79 MAG was only found in Antarctica, and the Leptolyngbya sp. BulkMat.35 and Pseudanabaenaceae cyanobacterium MP8IB2.15 MAGs were found in Antarctic and other cold environments. The findings based on metagenome matches and global comparisons suggest that these Antarctic cyanobacteria have distinct distribution patterns ranging from locally restricted to global distribution across the cold biosphere and other climatic zones.

Network pharmacology‒based analysis of marine cyanobacteria derived bioactive compounds for application to Alzheimer's disease

In recent years, the Alzheimer's disease (AD) epidemic has become one of the largest global healthcare crises. Besides, the available systemic therapies for AD are still inadequate. Due to the insufficient therapeutic options, new treatment strategies are urgently needed to achieve a satisfactory therapeutic effect. Marine bio-resources have been accepted as one of the most economically viable and sustainable sources with potential applications for drug discovery and development. In this study, a marine cyanobacteria-Synechococcus sp. XM-24 was selected as the object of research, to systematically investigate its therapeutic potential mechanisms for AD. The major active compounds derived from the Synechococcus sp. biomass were identified via pyrolysis-gas chromatography-mass spectrometry (GC-MS), and 22 compounds were identified in this strain. The most abundant chemical compounds was (E)-octadec-11-enoic acid, with the peak area of 30.6%. Follow by tridecanoic acid, 12-methyl- and hexadecanoic acid, with a peak area of 23.26% and 18.23%, respectively. GC-MS analysis also identified indolizine, isoquinoline, 3,4-dihydro- and Phthalazine, 1-methyl-, as well as alkene and alkane from the strain. After the chemical toxicity test, 10 compounds were finally collected to do the further analysis. Then, network pharmacology and molecular docking were adopted to systematically study the potential anti-AD mechanism of these compounds. Based on the analysis, the 10 Synechococcus-derived active compounds could interact with 128 related anti-AD targets. Among them, epidermal growth factor receptor (EGFR), vascular endothelial growth factor A (VEGFA) and mitogen-activated protein kinase 3 (MAPK3) were the major targets. Furthermore, the compounds N-capric acid isopropyl ester, (E)-octadec-11-enoic acid, and 2H-Pyran-2,4(3H)-dione, dihydro-6-methyl- obtained higher degrees in the compounds-intersection targets network analysis, indicating these compounds may play more important role in the process of anti-AD. In addition, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that these active compounds exert the anti-AD effects mainly through PI3K-Akt signaling pathway, neuroactive ligand-receptor interaction and ras signaling pathway. Our study identified Synechococcus-derived bioactive compounds have the potential for application to AD by targeting multiple targets and related pathways, which will provide a foundation for future research on applications of marine cyanobacteria in the functional drug industry.

The toxic cosmopolitan cyanobacteria Moorena producens: insights into distribution, ecophysiology and toxicity

Moorena producens is a benthic filamentous cyanobacteria that has been widely documented for its toxicity. This cyanobacterium colonizes both temperate (37%) and tropical (63%) regions, making it a cosmopolitan cyanobacterium with a global distribution. M. producens grows across coral reefs in multiple locations but recurringly blooms in Queensland, Australia. Today, nuisance blooms of M. producens have resulted in major disruptions to recreational activities along coastal areas and are known to cause adverse effects on organism and human health upon contact or ingestion. Specifically, marine organisms such as the green turtle Chelonia mydas and hawksbill turtle Eretmochelys imbricata were fatally poisoned by M. producens after consumption of this cyanobacterium. Reports record a range of effects on human health, from pain and blistering or even death upon ingestion of contaminated seafood. Blooms of M. producens are triggered by influxes of nitrogen, phosphate and iron, from surrounding coastal runoffs or sewage effluents. Additions of these nutrients can result in an increase in growth rate by 4-16 times. Iron bioavailability also plays a crucial role in bloom formation. A total of 231 natural products from 66 groups were identified from M. producens, with the three dominant groups: malyngamides, microcolins and dolastatins. These bioactive secondary metabolites have displayed toxicities against a range of carcinoma cell lines and organisms such as brine shrimp Artemia salina and goldfish Carassius auratus. This review provides a thorough insight to the distribution, ecophysiology and toxicity of M. producens, with reports on bloom events and implications on organism and human health.

Unmasking photogranulation in decreasing glacial albedo and net autotrophic wastewater treatment

In both natural and built environments, microbes on occasions manifest in spherical aggregates instead of substratum‐affixed biofilms. These microbial aggregates are conventionally referred to as granules. Cryoconites are mineral rich granules that appear on glacier surfaces and are linked with expanding surface darkening, thus decreasing albedo, and enhanced melt. The oxygenic photogranules (OPGs) are organic rich granules that grow in wastewater, which enables wastewater treatment with photosynthetically produced oxygen and which presents potential for net autotrophic wastewater treatment in a compact system. Despite obvious differences inherent in the two, cryoconite and OPG pose striking resemblance. In both, the order Oscillatoriales in Cyanobacteria envelope inner materials and develop dense spheroidal aggregates. We explore the mechanism of photogranulation on account of high similarity between cryoconites and OPGs. We contend that there is no universal external cause for photogranulation. However, cryoconites and OPGs, as well as their intravariations, which are all under different stress fields, are the outcome of universal physiological processes of the Oscillatoriales interfacing with goldilocks interactions of stresses. Finding the rules of photogranulation may enhance engineering of glacier and wastewater systems to manipulate their ecosystem impacts.

Cyanotoxin Analysis and Amino Acid Profiles of Cyanobacterial Food Items from Chad

In some parts of the world, cyanobacteria are used as a food in the human diet, due to their ready availability. Lake Chad, has long been a traditional site for the collection of Arthrospira fusiformis which is dried and processed at the lake into thin wafers called Dihé for later consumption or is transported to market for sale. However, Dihé purchased from markets in Chad has not been analyzed for known cyanobacterial toxins or assessed for total amino acid content. Since BMAA in traditional foodstuffs of the indigenous Chamorro people of Guam causes neurodegenerative illness, it is important that Dihé from Chad be analyzed for this neurotoxin. BMAA and its isomer AEG were not detected in our analyses, but a further isomer DAB was detected as both a free and bound amino acid, with an increase in the free concentration after acid hydrolysis of this fraction. Microcystins were present in 6 samples at up to 20 μg/g according to UPLC-PDA, although their presence could not be confirmed using PCR for known microcystin synthetic genes. Amino acid analysis of the cyanobacterial material from Chad showed the presence of large amounts of canonical amino acids, suggesting that this may supplement indigenous people on low protein diets, although regular monitoring of the foodstuffs for the presence of cyanotoxins should be performed.

Microterracettes in Sabkha Oum Dba (Western Sahara, Morocco): Physical and Biological Interactions in the Formation of a Surface Micromorphology

Small-scale terracing (microterracettes) is a surface geomorphic feature that recurs under a range of environmental settings, such as those existing in high to low temperature geothermal springs and evaporitic environments, through the single or combined action of physicochemical agents and microbiological processes. Such morphology can also be observed in a confined sector of the Sabkha Oum Dba, which is an inland sabkha of the Western Sahara (Morocco), where field and laboratory investigations revealed that they primarily depend on the accumulation of naviculoid diatoms. Through their biofilm production ability, these benthic diatoms are able to stabilize surface morphologies and make organic alveolar frameworks where the precipitation of low Mg calcite occurs in areas subjected to active oxygenic photosynthesis. Because microterracettes arise in a specific set of environmental conditions, they have environmental significance and, thanks to a high fossilization potential due to mineral precipitation, they can be an effective source of biomorphological and chemical evidence for life. The relationship with aqueous environments, considered to be widespread on Mars especially during a period of intense hydrologic activity as in the late Noachian and Hesperian periods, make the understanding of surficial processes useful (such as the formation of microterracettes) whose formation is frequent in terrestrial analogues for martian environments, such as ephemeral saline continental lakes (sabkhas) and related to the products of bacterial and eukaryotic life, as in the case of biofilms, in search for similar life forms beyond Earth.

Desiccation and radiation stress tolerance in cyanobacteria

Cyanobacteria are among the oldest living organisms on this planet, existing since more than 3 billion years. They are ideal organisms for investigating biological processes such as photosynthesis, respiration, circadian rhythm, photoregulation of gene expression, developmental gene rearrangements, and specialized cell differentiation. They are nearly ubiquitous in distribution, have colonized a wide range of ecosystems including soil, air, dry rock, and aquatic systems, and even occupy extreme niches that are inaccessible to other organisms. Such wide ecological distribution reflects their capacity to acclimate to extreme environments. They show great adaptive abilities and have survived various adverse physiological growth conditions like desiccation, high temperatures, extreme pH, cold, osmosis, salt, light, nitrogen, and high salinity. Their ancient origin and surviving through numerous stresses during evolution indicates their remarkable capabilities to survive and prevail under different environmental and man-made stresses. It has been hypothesized that similar and overlap stress response mechanisms help them to survive different stresses. It has been stated that responses against stresses like radiation has been accidental-exhibited because of similar response against desiccation stress, which has prevailed more during evolution. These overlaps and similarities in stress responses have been instrumental in making these organisms a large class of biological entities today. Present review discuss about stress tolerance in cyanobacteria against two extreme stresses - desiccation and gamma radiation. It also discuss the commonality and underlying molecular mechanisms in these two stress responses.

Physiological and proteomic analysis of salinity tolerance of the halotolerant cyanobacterium Anabaena sp

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

Molecular characterization and the effect of salinity on cyanobacterial diversity in the rice fields of Eastern Uttar Pradesh, India

Background

Salinity is known to affect almost half of the world's irrigated lands, especially rice fields. Furthermore, cyanobacteria, one of the critical inhabitants of rice fields have been characterized at molecular level from many different geographical locations. This study, for the first time, has examined the molecular diversity of cyanobacteria inhabiting Indian rice fields which experience various levels of salinity.

Results

Ten physicochemical parameters were analyzed for samples collected from twenty experimental sites. Electrical conductivity data were used to classify the soils and to investigate relationship between soil salinity and cyanobacterial diversity. The cyanobacterial communities were analyzed using semi-nested 16S rRNA gene PCR and denaturing gradient gel electrophoresis. Out of 51 DGGE bands selected for sequencing only 31 which showed difference in sequences were subjected to further analysis. BLAST analysis revealed highest similarity for twenty nine of the sequences with cyanobacteria, and the other two to plant plastids. Clusters obtained based on morphological and molecular attributes of cyanobacteria were correlated to soil salinity. Among six different clades, clades 1, 2, 4 and 6 contained cyanobacteria inhabiting normal or low saline (having EC < 4.0 ds m^-1) to (high) saline soils (having EC > 4.0 ds m^-1), however, clade 5 represented the cyanobacteria inhabiting only saline soils. Whilst, clade 3 contained cyanobacteria from normal soils. The presence of DGGE band corresponding to Aulosira strains were present in large number of soil indicating its wide distribution over a range of salinities, as were Nostoc, Anabaena, and Hapalosiphon although to a lesser extent in the sites studied.

Conclusion

Low salinity favored the presence of heterocystous cyanobacteria, while very high salinity mainly supported the growth of non-heterocystous genera. High nitrogen content in the low salt soils is proposed to be a result of reduced ammonia volatilization compared to the high salt soils. Although many environmental factors could potentially determine the microbial community present in these multidimensional ecosystems, changes in the diversity of cyanobacteria in rice fields was correlated to salinity.

Proteomics with a pinch of salt: a cyanobacterial perspective

Cyanobacteria are ancient life forms and have adapted to a variety of extreme environments, including high salinity. Biochemical, physiological and genetic studies have contributed to uncovering their underlying survival mechanisms, and as recent studies demonstrate, proteomics has the potential to increase our overall understanding further. To date, most salt-related cyanobacterial proteomic studies have utilised gel electrophoresis with the model organism Synechocystis sp. PCC6803. Moreover, focus has been on 2-4% w/v NaCl concentrations within different cellular compartments. Under these conditions, Synechocystis sp. PCC6803 was found to respond and adapt to salt stress through synthesis of general and specific stress proteins, altering the protein composition of extracellular layers, and re-directing control of complex central intermediary pathways. Post-transcriptional control was also predicted through non-correlating transcript level data and identification of protein isoforms.In this paper, we also review technical developments with emphasis on improving the quality and quantity of proteomic data and overcoming the detrimental effects of salt on sample preparation and analysis. Developments in gel-free methods include protein and peptide fractionation workflows, which can increase coverage of the proteome (20% in Synechocystis sp. PCC6803). Quantitative techniques have also improved in accuracy, resulting in confidence in quantitation approaching or even surpassing that seen in transcriptomic techniques (better than 1.5-fold in differential expression). Furthermore, in vivo metabolic labelling and de novo protein sequencing software have improved the ability to apply proteomics to unsequenced environmental isolates. The example used in this review is a cyanobacterium isolated from a Saharan salt lake.