Content of phycoerythrin, phycocyanin, alophycocyanin and phycoerythrocyanin in some cyanobacterial strains: Applications

An investigation of cyanobacteria, cyanotoxins and environmental variables in selected drinking water treatment plants in New Jersey

Harmful Algal Blooms (HAB) have the potential to impact human health primarily through their possible cyanotoxins production. While conventional water treatments can result in the removal of unlysed cyanobacterial cells and low levels of cyanotoxins, during severe HAB events, cyanotoxins can break through and can be present in the treated water due to a lack of adequate toxin treatment. The objectives of this study were to assess the HAB conditions in drinking water sources in New Jersey and investigate relationships between environmental variables and cyanobacterial communities in these drinking water sources. Source water samples were collected monthly from May to October 2019 and analyzed for phytoplankton and cyanobacterial cell densities, microcystins, cylindrospermopsin, Microcystis 16S rRNA gene, microcystin-producing mcyB gene, Raphidiopsis raciborskii-specific rpoC1 gene, and cylindrospermopsin-producing pks gene. Water quality parameters included water temperature, pH, dissolved oxygen, specific conductance, fluorescence of phycocyanin and chlorophyll, chlorophyll-a, total suspended solids, total dissolved solids, dissolved organic carbon, total nitrogen, ammonia, and total phosphorus. In addition to source waters, microcystins and cylindrospermopsin were analyzed for treated waters. The results showed all five selected New Jersey source waters had high total phosphorus concentrations that exceeded the established New Jersey Surface Water Quality Standards for lakes and rivers. Commonly found cyanobacteria were identified, such as Microcystis and Dolichospermum. Site E was the site most susceptible to HABs with significantly greater HAB variables, such as extracted phycocyanin, fluorescence of phycocyanin, cyanobacterial cell density, microcystins, and Microcystis 16S rRNA gene. All treated waters were undetected with microcystins, indicating treatment processes were effective at removing toxins from source waters. Results also showed that phycocyanin values had a significantly positive relationship with microcystin concentration, copies of Microcystis 16S rRNA and microcystin-producing mcyB genes, suggesting these values can be used as a proxy for HAB monitoring. This study suggests that drinking water sources in New Jersey are vulnerable to forthcoming HAB. Monitoring and management of source waters is crucial to help safeguard public health.

The use of fluorescence lifetime imaging (FLIM) for in situ microbial detection in complex mineral substrates

The utility of fluorescence lifetime imaging microscopy (FLIM) for identifying bacteria in complex mineral matrices was investigated. Baseline signals from unlabelled Bacillus subtilis and Euglena gracilis, and Bacillus subtilis labelled with SYTO 9 were obtained using two-photon excitation at 730, 750 and 800 nm, identifying characteristic lifetimes of photosynthetic pigments, unpigmented cellular autofluorescence, and SYTO 9. Labelled and unlabelled B. subtilis were seeded onto marble and gypsum samples containing endolithic photosynthetic cyanobacteria and the ability to distinguish cells from mineral autofluorescence and nonspecific dye staining was examined in parallel with ordinary multichannel confocal imaging. It was found that FLIM enabled discrimination of SYTO 9 labelled cells from background, but that the lifetime of SYTO 9 was shorter in cells on minerals than in pure culture under our conditions. Photosynthetic microorganisms were easily observed using both FLIM and confocal. Unlabelled, nonpigmented bacteria showed weak signals that were difficult to distinguish from background when minerals were present, though cellular autofluorescence consistent with NAD(P)H could be seen in pure cultures, and phasor analysis permitted detection on rocks. Gypsum and marble samples showed similar autofluorescence profiles, with little autofluorescence in the yellow-to-red range. Lifetime or time-gated imaging may prove a useful tool for environmental microbiology. LAY DESCRIPTION: The standard method of bacterial enumeration is to label the cells with a fluorescent dye and count them under high-power fluorescence microscopy. However, this can be difficult when the cells are embedded in soil and rock due to fluorescence from the surrounding minerals and dye binding to ambiguous features of the substrate. The use of fluorescence lifetime imaging (FLIM) can disambiguate these signals and allow for improved detection of bacteria in environmental samples.

Studying the impact of phycoerythrin on antioxidant and antimicrobial activity of the fresh rainbow trout fillets

Marine cyanobacteria present a significant potential source of new bioactive compounds with vast structural diversity and relevant antimicrobial and antioxidant activities. Phycobiliproteins (PBPs) like phycocyanin (PC), phycoerythrin (PE), and water-soluble cyanobacterial photosynthetic pigments, have exhibited strong pharmacological activities and been used as natural food additives. In this study, phycoerythrin (PE) isolated from a marine strain of cyanobacterium Nostoc sp. Ft salt, was applied for the first time as a natural antimicrobial as well as an antioxidant to increase the shelf life of fresh rainbow trout i.e., (Oncorhynchus mykiss) fillets. Fresh trout fillets were marinated in analytical grade PE (3.9 μg/mL) prepared in citric acid (4 mg/mL), and stored at 4 °C and 8 °C for 21 days. Microbiological analysis, antioxidant activity and organoleptic evaluation of both control and treated fish fillets were then statistically compared. The results demonstrated noticeable (P < 0.05) differences in the microbial counts, antioxidant activity, and organoleptic characteristic values between PE-treated and non-treated groups. In addition, we observed that treating fresh fish fillets with a PE solution leads to a significant increase in shelf life by at least 14 days. Consequently, PE could be an alternative to synthetic chemical additives since it does not contain the potentially dangerous residues of the synthetic chemical additives and is thus healthier to the consumers.

Assessment of Antimicrobial and Antioxidant Potential of Oscillatoria sancta and Oscillatoria proteus Isolated from Chilika Lake

Filamentous cyanobacteria are a promising source of biologically active secondary metabolites with antioxidant, antimicrobial, antiviral and anticancer properties. Previously, cyanobacteria isolated from fresh and marine water were studied extensively, but those isolated from brackish water were less investigated. The purpose of this study was to examine the antimicrobial activities as well as the potential antioxidant capacity of two cyanobacterial strains (Oscillatoria proteus and Oscillatoria sancta) obtained from Chilika Lake. The pigment and antioxidant was assayed using a spectrophotometer; antimicrobial activity was studied by minimum inhibitory concentration (MIC); and the presence of phytoconstituents was detected using gas chromatography mass spectrometry (GC-MS). The solvents used for extraction were methanol, acetone and benzene. The experimental data indicates that the total phenolic and flavonoid content was highest in O. sancta (58.26 ± 0.72 µg/g, 38.45 ± 0.79 µg/g, respectively). Similarly, the methanol extract of O. sancta presented the maximum antioxidant potential in both DPPH (83.18 ± 0.57%) and ABTS (68.42 ± 1.40%) radicals. Besides, more reducing power was also recorded in methanol extract of O. sancta as compared to O. proteus. Further, higher enzymatic activity (superoxide dismutase and catalase) was observed in O. sancta. The antimicrobial potential against bacterial and fungal pathogens demonstrated better activity in O. sancta. In GC-MS analysis seven major chemical classes have been detected. Differential results was found in the two species of Oscillatoria; however, both have potential antimicrobial and antioxidant properties. The findings have pharmaceutical and nutraceutical importance.

A photobioreactor for production of algae biomass from gaseous emissions of an animal house

Sustainable approaches to circular economy in animal agriculture are still poorly developed. Here, we report an approach to reduce gaseous emissions of CO2 and NH3 from animal housing while simultaneously using them to produce value-added biomass. To this end, a cone-shaped, helical photobioreactor was developed that can be integrated into animal housing by being freely suspended, thereby combining a small footprint with a physically robust design. The photobioreactor was coupled with the exhaust air of a chicken house to allow continuous cultivation of a mixed culture of Arthrospira spec. (Spirulina). Continuous quantification of CO2 and NH3 concentration showed that the coupled algae reactor effectively purifies the exhaust air from the chicken house while producing algal biomass. Typical production rates of greater than 0.3 g/l*day dry mass were obtained, and continuous operation was possible for several weeks. Morphological, biochemical, and genomic characterization of Spirulina cultures yielded insights into the dynamics and metabolic processes of the microbial community. We anticipate that further optimization of this approach will provide new opportunities for the generation of value-added products from gaseous CO2 and NH3 waste emissions, linking resource-efficient production of microalgae with simultaneous sequestration of animal emissions. KEY POINTS: • Coupling a bioreactor with exhaust gases of chicken coop for production of biomass. • Spirulina mixed culture removes CO2 and NH3 from chicken house emissions. • High growth rates and biodiversity adaptation for nitrogen metabolism. Towards a sustainable circular economy in livestock farming. The functional coupling of a helical tube photobioreactor with exhaust air from a chicken house enabled the efficient cultivation of Spirulina microalgae while simultaneously sequestering the animals' CO2 and NH3 emissions.

Phycobiliproteins from microalgae: research progress in sustainable production and extraction processes

Phycobiliproteins (PBPs), one of the functional proteins from algae, are natural pigment-protein complex containing various amino acids and phycobilins. It has various activities, such as anti-inflammatory and antioxidant properties. And are potential for applications in food, cosmetics, and biomedicine. Improving their metabolic yield is of great interest. Microalgaes are one of the important sources of PBPs, with high growth rate and have the potential for large-scale production. The key to large-scale PBPs production depends on accumulation and recovery of massive productive alga in the upstream stage and the efficiency of microalgae cells breakup and extract PBPs in the downstream stage. Therefore, we reviewed the status quo in the research and development of PBPs production, summarized the advances in each stage and the feasibility of scaled-up production, and demonstrated challenges and future directions in this field.

How diverse a genus can be: An integrated multi-layered analysis into Desmonostoc (Nostocaceae, Cyanobacteriota)

Cyanobacteria (Phylum Cyanobacteriota) are Gram-negative bacteria capable of performing oxygenic photosynthesis. Although the taxonomic classification of cyanobacteria was for a long time based primarily on morphological characters, the application of other techniques (e.g. molecular phylogeny), especially in recent decades, has contributed to a better resolution of cyanobacteria systematics, leading to a revision of the phylum. Although Desmonostoc occurs as a new genus/cluster and some species have been described recently, relatively few studies have been carried out to elucidate its diversity, which encompasses strains from different ecological origins, or examine the application of new characterization tools. In this context, the present study investigated the diversity within Desmonostoc, based on morphological, molecular, metabolic, and physiological characteristics. Although the usage of physiological parameters is unusual for a polyphasic approach, they were efficient in the characterization performed here. The phylogenetic analysis based on 16S rRNA gene sequences put all studied strains (25) into the D1 cluster and indicated the emergence of novel sub-clusters. It was also possible to observe that nifD and nifH exhibited different evolutionary histories within the Desmonostoc strains. Collectively, metabolic and physiological data, coupled with the morphometric data, were in general, in good agreement with the separation based on the phylogeny of the 16S rRNA gene. Furthermore, the study provided important information on the diversity of Desmonostoc strains collected from different Brazilian biomes by revealing that they were cosmopolitan strains, acclimatized to low luminous intensities, with a large metabolic diversity and great biotechnological potential.

Characterization of cyanobacterial isolates from freshwater and saline subtropical desert lakes

Characterization of Cyanobacteria in lakes with different physicochemical properties provides insights into the diversity of this phylum and knowledge of their features that are relevant to biotechnology applications. Six Cyanobacterial isolates were recovered from freshwater Lake Nasser and saline Lake Qarun, Egypt. The isolates were identified based on both morphology and molecular markers, 16S rRNA, and RuBisCO cbbL genes. The isolates SN1, SN2, SN3, SN4, Q1, and Q2 showed homologies with Merismopedia, Oscillatoria, Limnothrix, Persinema, and Jacksonvillea, respectively. The cbbL sequences for isolates SN1, Q1, and Q2 represented the first records for candidates relating to the genera Merismopedia and Persinema, and Jacksonvillea, respectively. Biochemical contents, carbohydrates, proteins, lipids, pigments, and ash-free dry weight were measured for each isolate. Isolate SN2 had the highest content of allophycocyanin, 71 ± 4.8 mg/g DW, and phycoerythrin, 98 ± 6.7 mg/g DW, while the isolate SN4 had the highest composition of total protein, lipid, carotenoid, and chlorophyll a, recording 364.7 ± 6.4 mg/g DW, 67.6 ± 0.2 mg/g DW, 0.261 ± 0.01 mg/g DW, and 10 ± 0.6 mg/g DW, respectively. Isolate Q1 recorded the maximum amount of phycocyanin, 114 ± 20.7 mg/g DW among isolates. The isolate Q2 was observed to have the highest carbohydrate content, 274 ± 14.5 (mg/g DW), and ash-free dry weight, 891.8 ± 2.8 mg/g DW. Thus, the study indicated that the current isolates may represent promising resources for biotechnological applications.

Insights from cyanobacterial genomic and transcriptomic analyses into adaptation strategies in terrestrial environments

Phylogenomic analysis of Nostoc sp. MG11, a terrestrial cyanobacterium, and some terrestrial and freshwater Nostoc strains showed that the terrestrial strains grouped together in a distinctive clade, which reveals the effect of habitat on shaping Nostoc genomes. Terrestrial strains showed larger genomes and had higher predicted CDS contents than freshwater strains. Comparative genomic analysis demonstrated that genome expansion in the terrestrial Nostoc is supported by an increase in copy number of the core genes and acquisition of shared genes. Transcriptomic profiling analysis under desiccation stress revealed that Nostoc sp. MG11 protected its cell by induction of catalase, proteases, sucrose synthase, trehalose biosynthesis and maltodextrin utilization genes and maintained its normal metabolism during this condition by up-regulation of genes related to phycobilisomes and light reactions of photosynthesis, CO₂ fixation and protein metabolism. These results provide insights into the strategies related to survival and adaptation of Nostoc strains to terrestrial environments.

Phycobilin heterologous production from the Rhodophyta Porphyridium cruentum

Phycobiliproteins are colored, active molecules with potential use in different industries. They are the union of proteins and bilins (Chromophores). The primary source of phycobiliproteins is algae; however, the traditional algae culture has production restrictions. The production in bacterial models can be a more efficient alternative to produce these molecules. However, the lack of knowledge in some steps of the phycobiliprotein metabolic pathway limits this alternative. Porphyridium cruentum is a single cell red alga with a high phycobiliprotein content. Its protein sequences were the basis for phycobilin production in this study. In this study, we cloned and characterized enzymes presumably involved in the chromophore production of P. cruentum. Using sequences obtained from its transcriptome, we characterized two cDNA sequences predicted to code respectively for a ferredoxin-dependent bilin reductase and a bilin lyase-isomerase. We expressed these enzymes in Escherichia coli to obtain in vivo evidence of their enzymatic activity on the substrate biliverdin IXα. Lastly, we analyzed them using thin-layer chromatography, spectrophotometry, and fluorescence spectroscopy. These experiments provided evidence of bilin modification. The expressed bilin lyase-isomerase did not show significant activity over the biliverdin molecule. On the contrary, the expressed ferredoxin-dependent bilin reductase showed activity over the biliverdin.

Whole-genome characterization and comparative genomics of a novel freshwater cyanobacteria species: Pseudanabaena punensis

Cyanobacteria are emerging as a potential source of novel, beneficial bioactive compounds. However, some cyanobacteria species can harm water quality and public health through the production of toxins. Therefore, surveying the occurrence and generating genomic resources of cyanobacteria producing harmful compounds could help develop the control methods necessary to manage their growth and limit the release contaminants into the water bodies. Here, we describe a novel strain, Pseudanabaena punensis isolated from the open ends of pipelines supplying freshwater. This isolate was characterized morphologically, biochemically and by whole-genome sequence analysis. We also provide genomic information for P. punensis to help understand and highlight the features unique to this isolate. Morphological and genetic (analysis using 16S rRNA and rbcL genes) data were used to assign this novel strain to phylogenetic and taxonomic groups. The isolate was identified as a filamentous and non-heterocystous cyanobacteria. Based on morphological and 16S rRNA phylogeny, this isolate shares characteristics with the Pseudanabaenaceae family, but remains distinct from well-characterized species suggesting its polyphyletic assemblage. The whole-genome sequence analysis suggests greater genomic and phenotypic plasticity. Genome-wide sequence and comparative genomic analyses, comparing against several closely related species, revealed diverse and important genes associated with synthesizing bioactive compounds, multi-drug resistance pathway, heavy metal resistance, and virulence factors. This isolate also produces several important fatty acids with potential industrial applications. The observations described in this study emphasize both industrial applications and risks associated with the freshwater contamination, and therefore genomic resources provided in this study offer an opportunity for further investigations.

Quantification of Moss-Associated Cyanobacteria Using Phycocyanin Pigment Extraction

In the boreal forest, cyanobacteria can establish associations with feather moss and realize the biological nitrogen fixation (BNF) reaction, consisting in the reduction of atmospheric dinitrogen into bioavailable ammonium. In this ecosystem, moss-associated cyanobacteria are the main contributors to BNF by contributing up to 50% of new N input. Current environmental changes driven by anthropogenic activities will likely affect cyanobacteria activity (i.e., BNF) and populations inhabiting mosses, leading to potential important consequences for the boreal forest. Several methods are available to efficiently measure BNF activity, but quantifying cyanobacteria biomass associated with moss is challenging because of the difficulty to separate bacteria colonies from the host plant. Attempts to separate cyanobacteria by shaking or sonicating in water were shown to be poorly efficient and repeatable. The techniques commonly used, microscopic counting and quantitative PCR (qPCR) are laborious and time-consuming. In aquatic and marine ecosystems, phycocyanin (PC), a photosynthesis pigment produced by cyanobacteria, is commonly used to monitor cyanobacteria biomass. In this study, we tested if PC extraction and quantification can be used to estimate cyanobacteria quantity inhabiting moss. We report that phycocyanin can be easily extracted from moss by freeze/thaw disturbance of cyanobacteria cells and can be quickly and efficiently measured by spectrofluorometry. We also report that phycocyanin extraction is efficient (high recovery), repeatable (relative SD < 13%) and that no significant matrix effects were observed. As for aquatic systems, the main limitation of cyanobacteria quantification using phycocyanin is the difference of cellular phycocyanin content between cyanobacteria strains, suggesting that quantification can be impacted by cyanobacteria community composition. Nonetheless, we conclude that phycocyanin extraction and quantification is an easy, rapid, and efficient tool to estimate moss-associated cyanobacteria number.