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Energy status and nutrients regulate photosynthetic protein expression. The unicellular green alga Chromochloris zofingiensis switches off photosynthesis in the presence of exogenous glucose (+Glc) in a process that depends on hexokinase (HXK1). Here, we show that this response requires that cells lack sufficient iron (-Fe). Cells grown in -Fe+Glc accumulate triacylglycerol (TAG) while losing photosynthesis and thylakoid membranes. However, cells with an iron supplement (+Fe+Glc) maintain photosynthesis and thylakoids while still accumulating TAG. Proteomic analysis shows that known photosynthetic proteins are most depleted in heterotrophy, alongside hundreds of uncharacterized, conserved proteins. Photosynthesis repression is associated with enzyme and transporter regulation that redirects iron resources to (a) respiratory instead of photosynthetic complexes and (b) a ferredoxin-dependent desaturase pathway supporting TAG accumulation rather than thylakoid lipid synthesis. Combining insights from diverse organisms from green algae to vascular plants, we show how iron and trophic constraints on metabolism aid gene discovery for photosynthesis and biofuel production.

To decipher the dispersal range of the cosmopolitan green microalga Tetracystis vinatzeri, two airborne-collected strains were barcoded using the 18S ribosomal DNA gene (18S) and the mitochondrial cytochrome c oxidase I subunit (COI), and their survival capacities were investigated across a stepwise acidic to alkaline pH gradient. Genetic fingerprinting confirmed the identity of the strains as representing the same biological species. Investigations of the tolerance of T. vinatzeri to pH levels refined the delimitation of its ecological niche. T. vinatzeri showed optimal growth in freshwater habitats at pH 4.3–9.6 and strains could cope with exposure to slightly more acidic (down to 3.8) and alkaline (up to 10.4) conditions. However, organismal survival was drastically affected by exposure to pH < 3 and > 11. Morphological observations showed that T. vinatzeri could better cope with exposure to acidic pH, exhibiting less cell membrane damage. Genetic analysis showed that the two airborne strains shared the same haplotype, suggesting that they either originated from the same air mass or that the haplotype has a widespread distribution. Further phylogeographic and physiological investigations are required to define the spreading dynamic of T. vinatzeri. Highlights: Tetracystis vinatzeri can grow at pH from 3.8–10.4. Strains from different habitats showed sexual compatibility. Low genetic diversity and cosmopolitan distribution suggest widespread dispersal. [ABSTRACT FROM AUTHOR]

Sea lettuce (Ulva) is a genus of green macroalgae present along all the coasts of the world's oceans. It represents about 100 species with diverse habitats. Inter- and intra-species natural variation is very large, both in terms of growth characteristics and biomass biochemical composition. As a result, Ulva biomass has a wide range of applications and strain selection can achieve significant increases in yield(s). Establishing solid, long term and cost-effective methodologies for the conservation of Ulva genetic diversity is then required to safeguard and reuse selected strains. Here, we report a cryopreservation-based protocol for the long-term preservation of foliose Ulva strains. Strains from seven different Ulva species were cryopreserved for 15 and/or 120 days in liquid nitrogen, and of the 3 replicates cryopreserved, at least one survived, allowing us to successfully recover all strains. On average, among all specimen cryo-preserved, 82% of them survived and grew post cryo-preservation. [ABSTRACT FROM AUTHOR]

Laccases are extracellular multicopper oxidases that react with a broad range of aromatic substrates and are used for many biotechnological applications. Recently, microalgal laccases were discovered and started to be characterized in some Chlorophyceae (Tetracystis aeria and a few other species). A volumetric activity of maximum 27 U L-1 could be reached with Chlamydomonas moewusii, which is largely insufficient to compete with fungi and heterologous expression systems. Here, the acidophilic green microalga Chlamydomonas pitschmannii was shown to be a new promising source of laccase competing with fungi in terms of secretion yields. By modulating culture pH and CO2 supply, laccase volumetric activity in the supernatant could be increased from 12 to 459 U L-1. Laccase-containing supernatants were found to oxidize many phenolic and non-phenolic substrates with an efficiency that was pH-dependent. 1D SDS-PAGE was achieved and lighted up that C. pitschmannii laccase is a glycosylated protein. Functional measurements pointed out the participation of glycosylation in functional enzymatic regulation and integrity. Two bands of about 50 and 45 kD were detected that presumably corresponded to laccase. In agreement with previous studies in T. aeria, we hypothesize that C. pitschmannii laccase is a heterodimer, a feature that denotes with most known laccases, essentially monomeric. Altogether, those results demonstrate that efforts of discovery and characterization of microalgal laccases must be continued with regards to the amazing potential they offer for biotechnological applications. [ABSTRACT FROM AUTHOR]

The cheese industry produces substantial amounts of raw cheese whey wastewater (RW), which requires effective treatment prior to environmental disposal. This study presents an innovative sequential batch system that combines macrophyte and microalgal cultivation for RW remediation. The efficacy of Lemna minor MO23 in first-line photobioreactors (PBR-1) and Chlorella sp. MC18 (CH) or Scenedesmus sp. MJ23-R (SC) in second-line photobioreactors (PBR-2) for pollutant removal was evaluated. The nutrient removal capacity of L. minor, CH, and SC was assessed at optimal tolerance concentrations, alongside nutrient recovery from treated RW (TRW) by PBR-1 for microalgae biomass production. The results demonstrate that all three species effectively purified the cheese whey wastewater. L. minor efficiently removed COD, nitrate, phosphate, and sulfate from RW, producing TRW effluent suitable for microalgal growth. CH and SC further purified TRW, enhancing biomass production. CH outperformed SC with a 4.79% higher maximum specific growth rate and 20.95% higher biomass yield. Biochemical analyses revealed the potential of CH and SC biomass for applications such as biofuels and aquaculture. After treatment, the physicochemical parameters of the effluent were within the regulatory limits. This demonstrates that the PBR-1 and PBR-2 series-coupled system effectively purifies and recovers dairy effluents while complying with discharge standards. [ABSTRACT FROM AUTHOR]

The availability of light and its efficient utilisation is a major limiting factor in large scale algal cultures. While algae predominantly use the blue and red spectral regions, a significant amount of incoming light energy remains untapped outside these ranges. Converting this unused light into usable wavelengths could enhance photosynthesis. This study aimed to identify the optimal spectral converter among Lumogen Red (LR), Rhodamine 8G (R8G), and Lumogen Yellow (LY), providing efficient light utilisation for algal cultivation. Chlamydomonas reinhardtii was cultivated in double-jacketed cylindrical photo-bioreactors (PBRs) using 30% UV-a and 5% UV-b fluorescent tubes. The R8G dye displayed a slight wavelength shift with a sharp peak at about 498 nm. The LY dye demonstrated several sharp peaks at the green and blue light spectra evident of photo-degradation. The LR dye maintained better photo-stability compared to R8G and LY. Carbohydrate, lipid and protein were produced early, whereas biomass increased after day 4, as a result of photo-acclimation. The LR dye converted and emitted 3.17 × 10-19 J photon-1, enhancing biomass production and increasing photochemical energy utilisation [Y(II)] while decreasing regulated energy dissipation [Y(NPQ)]. Pigment biosynthesis was initially increased and then reduced to counteract heightened irradiation as a means of photo-protection. LR had a 1.6- and 2.9-fold up-regulation of the RuBisCo gene expression. The dye-based system correlated with improved growth, lipid, protein, carbohydrate, and pigment production. The dye-based wavelength conversion system was interlinked to the sustainable development goals addressing environmental, economic, and social aspects. [ABSTRACT FROM AUTHOR]

Epilithic green algae play crucial roles in aquatic ecosystems. While traditional morphological approaches have provided valuable insights into these algae, their limitations in resolving cryptic species and fully capturing the extent of diversity have impeded a comprehensive understanding. The diversity and phylogenetic relationships of these algae largely remain unexplored. In the present study, single molecular real-time (SMRT) sequencing of the full-length 18S rDNA was employed to investigate the molecular diversity and phylogenetic relationships of epilithic green algae in biodiversity conservation hotspots. A total of 79 709 algal reads were generated, yielding 169 amplicon sequence variants (ASVs) from 21 epilithic riverine green algal assemblages classified in the Ulvophyceae, Chlorophyceae and Trebouxiophyceae. The 10 families in which the greatest number of unique ASVs (diversity) were observed were the Ulvellaceae, Protosiphonaceae, Chlorococcaceae, Watanabeaceae, Chlorellaceae, Neochloridaceae, Chaetophoraceae, Hazeniaceae, Tupiellaceae and Scenedesmaceae. Unique clades formed by a substantial number of sequences of green algae were detected within the Ulvales/Ulotrichales (Ulvophyceae) and the Chlorococcaceae/Protosiphonaceae (Chlorophyceae). This study has unveiled hidden diversity within epilithic green algae, expanding our knowledge of their evolutionary relationships and providing fundamental data for taxonomic investigations within this group, as well as contributing to the assessment of algal diversity in biodiversity conservation hotspots. This study suggests that these epilithic green algal assemblages may be significantly more diverse than previously recognized, but we acknowledge the limited ecological and temporal scope of our sampling effort and the resulting effects on which taxa are identified, warranting further research. Molecular analysis shows high hidden diversity of epilithic green algae The families Ulvellaceae and Protosiphonaceae had the greatest number of unique ASVs Many unique clades within the Ulvales/Ulotrichales and Chlorococcaceae/Protosiphonaceae [ABSTRACT FROM AUTHOR]

Phytoplankton not only acts as a water quality indicator but is also useful for biomonitoring of lentic freshwater bodies. Hence, the present study was attempted to analyse the phytoplankton composition during the four seasons of the year. Results of the present study indicate that phytoplankton were represented by 46 species belonging to Cyanophyceae, Chlorophyceae, Bacillariophyceae, Euglenophyceae and Dinophyceae. Among the various groups, Cyanophyceae dominated in terms of percentage followed by Chlorophyceae, Bacillariophyceae, Euglenophyceae and Dinophyceae. Dinophyceae was recorded only during the presummer and rainy season. The present study recorded the presence of organisms like Anabaena and Microcystis, which indicates eutrophication; Oscillatoria which indicates the presence of high organic matter and low oxygen level as well as Ceratium which indicates pollution. [ABSTRACT FROM AUTHOR]

Loej coast situated near Mangrol of Saurashtra region, Arabian Sea, Gujarat is supported by diverse flora and fauna. The present study aimed to document seaweed diversity and distribution along intertidal region of Loej coast by using belt transect sampling method from October 2021 to March 2022. From the study area, a total of 56 seaweed species belonging to 3 phyla, 3 classes, 16 orders, 25 families and 36 genera were recorded. Out of these 12 species were green seaweed, 14 species were brown and 30 species were red seaweed. Maximum number of species diversity was reported from class Rhodophyceae. Dictyotales (16%, species) was found to be dominant order followed by Gigartinales (14%, species); Ceramiales (11%, species). Among 25 families, Dictyotaceae was the dominant family reported with 14 species. Distribution study observed vertical distribution from the seashore side to the seaside of green, brown and red seaweed. Also, horizontal distribution of green seaweed and red seaweed were seen in the upper intertidal area and in the lower intertidal area, respectively. In species distribution behaviour, out of 56 species of seaweed; 8 species show aggregated behaviour, 10 species show the regular distribution and 38 species show random aggregation behaviour. Ulva lactuca was most abundantly and frequently found species with maximum density during the whole study period. During the present study, diversity indices like species diversity index (H') indicate healthy diverse seaweed fauna. Species richness index/Margalef's diversity index (D) was in the range of 3.37-4.81. Maximum species richness was reported in winter month February and minimum species richness in October. Pielou's evenness index (J) showed that seaweed species were unevenly distributed. [ABSTRACT FROM AUTHOR]

Microalgae are regarded as a promising source of renewable energy and high-value compounds. To date most large-scale microalgae cultivation is located in hot low-latitude regions; however, high temperature and high solar intensity create a risk of overheating during summer days. Here we explore the option of microalgae cultivation in low temperature regions. The impact of low temperature on microalgae growth is rarely considered in studied species and strains. To assess the optimum temperature and to test the ability to grow in low temperatures, we tested the effect of environmental temperatures ranging from 8 to 32 °C on the growth of the green microalga Chlorella vulgaris 211/11j. This strain was selected as a candidate strain for outdoor cultivation after an extensive literature review. The results indicate that C. vulgaris 211/11j has a lower optimal growth temperature than some other strains of C. vulgaris and exhibits optimal growth over a wide temperature range from 20 to 28 °C. Moreover, we demonstrate that the strain can grow successfully at low environmental temperatures that are below the optimum of this strain. Therefore, we suggest C. vulgaris 211/11j as a potential strain for cultivation in outdoor open ponds exposed to changing environmental temperatures in cooler climate regions. [ABSTRACT FROM AUTHOR]

The effects of silicon oxide nanoparticles (SNPs) on the growth of Chlorella vulgaris and its influence on biodegradation of pyrene (PYR) were evaluated. Addition of SNP to culture media at low concentrations (0.5–5 mg L−1) showed beneficial effects on growth and biomass of C. vulgaris. SNP at 1 mg L−1 showed 13% enhancement in biomass during 7 days of cultivation of C. vulgaris. The total chlorophyll content and PSII activity were highest in 1 mg L−1 SNP. We observed the toxicity mitigating aspect of SNPs (1 mg L−1) when algae were grown in a medium containing PYR (5 mg L−1). Biodegradation of PYR by C. vulgaris was significantly improved (31%) in the presence of 1 mg L−1 SNP in 5 days. The study of enzyme activity demonstrated that catechol 2,3 dioxygenase activity, which has an important role in the biodegradation of PYR, was upregulated in algal cells treated with SNP + PYR, whereas dehydrogenase activity which is also responsible for degradation of organic chemicals, was unaltered. This result proves the role of SNP in PYR biodegradation capacity of C. vulgaris through involvement of the dioxygenase pathway. Current findings suggest the possibility of SNP addition to the microalgal media to improve algal growth as well as PYR bioremediation capacity. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the novel valorization of wastewater through the desalination process of concentrated saline water (CSW) originating from the semiarid regions of Brazil using the growth of two microalgae and modeling their growth using a kinetic model. Chlorella vulgaris and Ankistrodesmus fusiformis were cultured for 15 days in BG 11 medium that was partially replaced with wastewater, and the data from the best growing conditions were fitted to the model of Gompertz. The CSW had a low heavy metal concentration and both algae grew under all conditions studied. However, each microalga exhibited a different behavior under the same conditions. C. vulgaris remained only in the adaptation phase when it was cultured in 100% CSW. In contrast, A. fusiformis was only 3 days in the lag phase and had 67% more biomass than C. vulgaris. 75% CSW was best for both microalgae. This study demonstrates a circular bioeconomy model that can be applied to semiarid regions to provide water and food security for the local population. The potential of A. fusiformis has also been highlighted; however, it has not yet been explored in the field of microalgae culture. [ABSTRACT FROM AUTHOR]

Green seaweeds, particularly species of the genus Monostroma, have gained recognition for their health-promoting potential, attributed to their rich content of polysaccharides, polyphenols, carotenoids, flavonoids, vitamins, and macro- and micronutrients, all of which show a wide range of bioactive properties. This review encompasses a total of 72 articles, selected in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The compounds present in Monostroma spp., in addition to their nutritional and chemical compounds, are associated with a number of health-promoting activities. However, it is notable that among the literature reviewed for bio-functionalities, a considerable proportion of studies were conducted in vitro (66%), followed by in vivo studies (29%), with clinical trials accounting for a much smaller fraction (5%). The mechanisms underlying the health-beneficial effects in biological systems require further in-depth exploration and characterization to facilitate future translational research leading to clinical trials. These clinical trials are an essential step in advancing seaweed-based functional food ingredients into the industrial realm. As of now, research focusing on bioactive compounds derived from Monostroma is relatively scarce. This review serves as a resource, offering insights into the nutritional and functional properties of Monostroma species. It can be a valuable tool for food scientists and engineers as they embark on future research involving Monostroma and the development of seaweed-based food and nutraceutical products. [ABSTRACT FROM AUTHOR]

Marine algae are responsible for half of the world's primary productivity, but this critical carbon sink is often constrained by insufficient iron. One species of marine algae, Dunaliella tertiolecta, is remarkable for its ability to maintain photosynthesis and thrive in low-iron environments. A related species, Dunaliella salina Bardawil, shares this attribute but is an extremophile found in hypersaline environments. To elucidate how algae manage their iron requirements, we produced high-quality genome assemblies and transcriptomes for both species to serve as a foundation for a comparative multiomics analysis. We identified a host of iron-uptake proteins in both species, including a massive expansion of transferrins and a unique family of siderophore-iron-uptake proteins. Complementing these multiple iron-uptake routes, ferredoxin functions as a large iron reservoir that can be released by induction of flavodoxin. Proteomic analysis revealed reduced investment in the photosynthetic apparatus coupled with remodeling of antenna proteins by dramatic iron-deficiency induction of TIDI1, which is closely related but identifiably distinct from the chlorophyll binding protein, LHCA3. These combinatorial iron scavenging and sparing strategies make Dunaliella unique among photosynthetic organisms.

Chlamydomonas spp. and Chlorella spp. are plankton genera that can be used to determine the level of balance in the aquatic environment. The purpose of this study is to determine the abundance of plankton Chlamydomonas spp. and Chlorella spp. and its relation to the clinical performance of red tilapia in silvofishery ponds. The research method used is an ex post facto causal design with random sampling. The results showed that the water quality in the silvofishery ponds was very good, except for the nitrate parameters of 0.00-1.50 mg/L and salinity of 2-11 gr/L, which exceeded the quality standards. In the silvofishery ponds, 5 plankton classes were found, namely Chlorophyceae, Cyanophyceae, Chrysophyceae, Protozoa, and Dinophysis, consisting of 15 genera. The dominant class Chlorophyceae had an abundance of 2.88E+06 cells/ml. The class Chlorophyceae is dominated by Chlorella spp. (2.63E+06 cells/ml) and Chlamydomonas spp. (2.20E+05 cells/ml). The abundance of Chlamydomonas spp. in silvofishery ponds is closely related to phosphate solubility (0.988). Based on observations of clinical symptoms on the eyes, gills, and fins of fish, no disease infections or physical abnormalities were found in the fish cultured in silvofishery ponds. Fish tend to live well with a growth rate of 0.44 g/day. The aquatic ecosystem of the silvofishery pond, which is dominated by the plankton Chlorella spp. and Chlamydomonas spp., had a good effect on the performance and condition of the farmed fish. This study concludes that the abundance of Chlamydomonas spp. and Chlorella spp. was very dominant compared to other plankton genera. The presence of Chlamydomonas spp. and Chlorella spp. illustrates good and stable environmental conditions in silvofishery ponds, followed by no clinical signs of disease infection in the fish reared during the study period.

Caulerpa lentillifera has gained popularity among consumers and researchers in recent years due to its good nutritional profile. The objective of this study is to explore whether the incorporation of different levels of C. lentillifera powder (CLP) concentration in noodles could potentially improve the noodle nutrient profile. The sensory attributes and the nutrient content of the developed noodles were evaluated. Five formulations of noodles containing different percentages of CLP, 0% (F1), 2.5% (F2), 5.0% (F3), 7.5% (F4), and 9.0% (F5) were developed. A sensory evaluation based on a 9-point hedonic scale involving 50 untrained panellists was conducted to determine the best formulation of noodles incorporated with CLP. All formulations were subjected to proximate analyses. From the sensory evaluation, the noodle with the best formulation was F2 (2.5% CLP) as it has the highest score in all sensory attributes tested among all formulations with CLP. Nutrient comparisons between F1 (0% CLP, F2 (2.5% CLP) and a commercial noodle in Malaysia were also made based on its mandatory nutritional facts and mineral profile. The incorporation of 2.5% CLP increased the mineral and protein content of the noodles significantly at p < 0.05. In conclusion, CLP incorporation in noodles improves their nutrient profile, and the sensory attributes of noodles containing 2.5% CLP were found to be acceptable. [ABSTRACT FROM AUTHOR]

The cheese industry produces substantial amounts of raw cheese whey wastewater (RW), which requires effective treatment prior to environmental disposal. This study presents an innovative sequential batch system that combines macrophyte and microalgal cultivation for RW remediation. The efficacy of Lemna minor MO23 in first-line photobioreactors (PBR-1) and Chlorella sp. MC18 (CH) or Scenedesmus sp. MJ23-R (SC) in second-line photobioreactors (PBR-2) for pollutant removal was evaluated. The nutrient removal capacity of L. minor, CH, and SC was assessed at optimal tolerance concentrations, alongside nutrient recovery from treated RW (TRW) by PBR-1 for microalgae biomass production. The results demonstrate that all three species effectively purified the cheese whey wastewater. L. minor efficiently removed COD, nitrate, phosphate, and sulfate from RW, producing TRW effluent suitable for microalgal growth. CH and SC further purified TRW, enhancing biomass production. CH outperformed SC with a 4.79% higher maximum specific growth rate and 20.95% higher biomass yield. Biochemical analyses revealed the potential of CH and SC biomass for applications such as biofuels and aquaculture. After treatment, the physicochemical parameters of the effluent were within the regulatory limits. This demonstrates that the PBR-1 and PBR-2 series-coupled system effectively purifies and recovers dairy effluents while complying with discharge standards.

The supplementation of nutrients from agro-industrial residues is a sustainable strategy to improve cost-benefit microalgae production; nonetheless, developing the appropriate supplementation of residue for each microalgal strain is necessary. In this study, a supply strategy of fruit residue (such as mango, banana, apple, tomato, plum, melon, orange, tangerine, grape, strawberry, cherimoya, pear, pineapple, peach and cucumber) was developed to enhance Chlorella sp. CM18 growth and lipid production in a 5-L photo-bioreactor and simultaneously maximize the efficiencies of nutrient removal processes (chemical oxygen demand [COD], NO3−, PO43−, and SO42−) by this alga. This study demonstrates that the microalga attained the highest removal efficiencies when this residue was diluted at 10% (v/v) with MN medium, attaining 89.07 ± 0.31% (COD), 91.55 ± 0.94% (NO3−), 93.82 ± 0.61% (PO43−), and 76.01 ± 0.68% (SO42−). Under this condition, the highest growth rate of Chlorella sp. was 1.35 ± 0.004 day−1 with a lipid production of 15.60 ± 3.17 mg L−1, demonstrating the feasibility of the culture process with Chlorella sp. CM18 to obtain an effluent possessing characteristics that were below the regulatory limits for the concerned parameters and emphasizing the concept of the sustainable circular economy. Overall, this study establishes a method to valorize the nutrients of fruit residues with the aim of producing biomass and lipids through the cultivation of the microalga Chlorella sp. CM18. [ABSTRACT FROM AUTHOR]

Different populations of the same species may have different physiological responses to environmental factors due to the adaptation to their environment. We tested interactive effects of temperatures (10,15, 20, 25, and 30 ℃) and nutrients (low nutrients: 5 μM NO3− and 0.5 μM PO4− (LN); medium nutrients: 50 μM NO3− and 5 μM PO4− (MN); high nutrients: 500 μM NO3− and 50 μM PO4− (HN)) in three different Ulva prolifera strains (one Chinese and two Korean strains). The results showed that all three strains of Ulva survived within the temperature range of 10 to 30 ℃. The photosynthetic rates of all strains increased with increasing temperature from 10 to 30 ℃ under MN. However, at the higher temperature (30 ℃) there was a significant reduction in the photosynthetic rate under HN in all three strains. A positive relationships between tissue nitrogen (N) and chlorophyll or soluble protein were observed in all three strains. The Chinese strain showed the lowest C:N ratio but the highest photosynthetic rate and tissue N contents. Our results show that the bloom forming Chinese strain may have higher nutrient uptake and assimilation ability, leading to higher photosynthetic activity. The Ulva strains may have lower tolerance to higher temperature at high nutrients conditions. These results suggest that the physiological responses of U. prolifera to different temperature and nutrients conditions can be population-specific. [ABSTRACT FROM AUTHOR]

Excess inorganic nitrogen in offshore estuarine areas can adversely affect coastal water quality. To explore the bioremediation potential of Ulva lactuca in low-salinity and high-nutrient water, the dissolved inorganic nitrogen (DIN) removal under different low salinities (0, 0.5, 1.0, 1.5, 2.0% NaCl) and high nutrients was studied. Static culture experiments exhibited a maximum DIN removal efficiency of 73.74% with U. lactuca in the 1.0% salinity system. The differences in DIN removal efficiency at 1.0, 1.5 and 2.0% NaCl salinity were not significant (p > 0.05 and could reach above 65%. High-throughput sequencing, scanning electron microscopy (SEM) and excitation emission matrix (EEM) analysis demonstrated that the diversity of microorganisms decreased with increasing salinity with Proteobacteria and Bacteroidota the main phyla, revealing the synergistic effect of U. lactuca and microbes. Response surface curves showed that the conditions affecting DIN removal efficiency from high to low were salinity, density, and C/N ratio. By simulating the fluctuation of salinity and water level in the offshore estuarine environment, the efficient DIN removal was more than 60% and dissolved oxygen (DO) concentration was about 8 mg L−1 with U. lactuca at salinity above 1.0% NaCl. In conclusion, this study explored the DIN removal pattern of U. lactuca in different low-salinity and high-nutrient water environments, which is of great importance for the ecological restoration of estuarine and coastal environments. [ABSTRACT FROM AUTHOR]

Common Bean (Phaseolus vulgaris) is considered one of the most affordable sources to tackle hunger in underdeveloped countries. However, its cultivation takes place in regions that suffer from water deficiency, which limits plant growth and crop yield. Therefore, it is necessary to seek sustainable alternatives that mitigate the deleterious effects of water shortage. The aim of this study was to evaluate the potential for mitigating the effects of water deficit with the application of the chlorophyte microalga Asterarcys quadricellularis (CCAP 294/1) in two bean cultivars (IAC 1850 and BRS ESTEIO). The plants were grown in pots, with foliar application of microalgae at stage of third fully expanded trefoil at concentrations of 0.5 mL L−1 and 1.0 mL L−1. The water deficit lasted for 7 days and, after that, the rehydration of the plants was performed. Evaluations were carried out in three periods: i. on the third day after the start of water restriction, ii. one day after rehydration, iii. 10 days after rehydration. The levels of chlorophyll, sugars, protein and antioxidant enzymes were increased in plants treated with microalgae. At ten days after rehydration, there was an increase in leaf area, fresh mass, and leaf thickness in the treated plants, characterizing the biostimulant effect of microalgae. Our results demonstrate the effects of A. quadricellularis in mitigating the deleterious effects of water deficit, accelerating the recovery of the two common bean cultivars, which demonstrates its potential as a sustainable alternative to support food production under changing environment. [ABSTRACT FROM AUTHOR]

Endogenous phytohormones play a vital role in the growth and secondary metabolism performance of microalgae and their secretion is significantly affected by external environmental conditions. In this study, the combined influences of three carbon sources (glucose, sodium pyruvate, and sodium acetate) and three pH levels (6, 8 and 10) on growth, astaxanthin accumulation, and contents of four endogenous phytohormones (indole-3-acetic acid, IAA; zeatin riboside, ZR; gibberellic acid 3, GA3; abscisic acid, ABA) of Haematococcus pluvialis were investigated. The results showed that carbon source and pH level had significant isolated and interactive effects on growth, astaxanthin accumulation, and endogenous phytohormone secretion. The cell density, specific growth rate and cell dry weight reached the highest levels in the glucose treatment at pH 8. The maximum astaxanthin concentration and productivity occurred in the glucose treatment with pH 10. The contents of IAA, ZR and GA3 significantly increased at the green stage (vegetative cell stage), indicating their potential involvement in cell proliferation. ABA contents, in contrast, significantly increased at the red stage (red cyst cell stage), probably contributing to astaxanthin accumulation. This experiment provided valuable insights for optimizing the mixotrophic cultivation conditions of H. pluvialis and successfully developing biological regulators. [ABSTRACT FROM AUTHOR]

Microalgae are a natural source of valuable compounds with a wide range of applications. Given their physiological plasticity, strategies aiming at increasing the content of biomolecules have been proposed. In this study, low-dose copper and blue/red lights were combined and used as a manipulative strategy to induce biomolecule accumulation in Kirchneriella contorta. Cultures were exposed to a 1.6 × 10–9 to 1.7 × 10–8 mol L−1 free copper (Cu2+) concentration range under white light for 48 h. Afterwards, the white light was replaced with blue or red lights for up to 96 h. We evaluated population growth through growth rates, photosynthesis through pulse amplitude modulated fluorescence (PAM) and biomolecules by quantifying chlorophyll a, carotenoids, carbohydrates and proteins. The results showed that at 3.8 × 10–9 mol L−1 Cu2+ and blue light, 2 × more carotenoids, 4 × more carbohydrates and 3 × more proteins were accumulated in the cells compared to the control. Among the light colors, the blue light most significantly interfered with the algal metabolism compared to the other colors. Although growth rates and maximum and operational quantum yields were not affected, non-photochemical quenching (NPQ) increased under blue light, showing that its higher energy compared to red and white lights may have impacted the photosynthetic apparatus. This study contributes to the biotechnology of microalgae by proposing a manipulative strategy that triggered the build-up of biomolecules in K. contorta. [ABSTRACT FROM AUTHOR]

Thrombosis is characterized by the pathological formation of fibrin clots within a blood vessel, leading to the obstruction of blood flow. Fibrinolytic enzymes from microorganisms have been shown to be more efficient and safer in dissolving clots. Then, this study aimed to evaluate the cell growth and fibrinolytic enzyme production of Tetradesmus obliquus under different cultivation conditions. T. obliquus grew under autotrophic and mixotrophic conditions using different concentrations of corn steep liquor (0.25 ≤ CSL ≤ 4.00%). The cells were concentrated and lysed via two different methods (sonication or homogenization) to trigger the release of the enzyme. It was precipitated via acetone or ammonium sulfate additions and purified using ion exchange chromatography. The highest biomass productivity (Px = 130 ± 12.8 mg∙L−1day−1), specific growth rate (µmax = 0.17 ± 0.00 day−1), and fibrinolytic activity (391 ± 40.0 U∙mg−1) was achieved on a mixotrophic cultivation at a 0.25% CSL concentration. The results showed that the homogenizing method had better performance in the release of enzyme, and the precipitation with acetone obtained the highest fibrinolytic activity (567 ± 49.3 U∙mg−1). The purified enzyme showed a specific activity of 1221 ± 31 U∙mg−1 and a molecular mass of 97 kDa. So, the fibrinolytic enzyme from T. obliquus had higher activity when compared to the other fibrinolytic enzymes, being a potential source for the development of therapeutic agents in thrombosis treatment. Additional studies are needed to investigate the biochemical properties and biological profile of this enzyme. [ABSTRACT FROM AUTHOR]

The present study shows the characterization of the bacterial communities associated with different systems during the cultivation of the microalga Tetradesmus obliquus. For that, sequential cultivation was performed in three different systems: (1) Photobioreactor bench‐scale; (2) flat‐panel photobioreactor; and (3) thin‐layer cascade. Cultures were monitored daily for growth parameters and biomass samples were collected for characterization of bacterial communities using metagenomic. A total of 195,177 reads were produced, resulting in the identification of 72 OTUs. In the grouping of bacterial communities, 3 phyla, 6 classes, 28 families, and 35 taxa were found. The bacteria Brevundimonas and Porphyrobacter had a higher relative abundance compared with other taxa found. These taxa were present in all cultivation systems forming a possible core community. Bacterial communities associated with different cultivation systems of the microalga T. obliquus showed an increase in taxa richness and diversity in the super‐intensive and intensive systems. [ABSTRACT FROM AUTHOR]

Thrombosis is characterized by the pathological formation of fibrin clots within a blood vessel, leading to the obstruction of blood flow. Fibrinolytic enzymes from microorganisms have been shown to be more efficient and safer in dissolving clots. Then, this study aimed to evaluate the cell growth and fibrinolytic enzyme production of Tetradesmus obliquus under different cultivation conditions. T. obliquus grew under autotrophic and mixotrophic conditions using different concentrations of corn steep liquor (0.25 ≤ CSL ≤ 4.00%). The cells were concentrated and lysed via two different methods (sonication or homogenization) to trigger the release of the enzyme. It was precipitated via acetone or ammonium sulfate additions and purified using ion exchange chromatography. The highest biomass productivity (Px = 130 ± 12.8 mg∙L−1day−1), specific growth rate (µmax = 0.17 ± 0.00 day−1), and fibrinolytic activity (391 ± 40.0 U∙mg−1) was achieved on a mixotrophic cultivation at a 0.25% CSL concentration. The results showed that the homogenizing method had better performance in the release of enzyme, and the precipitation with acetone obtained the highest fibrinolytic activity (567 ± 49.3 U∙mg−1). The purified enzyme showed a specific activity of 1221 ± 31 U∙mg−1 and a molecular mass of 97 kDa. So, the fibrinolytic enzyme from T. obliquus had higher activity when compared to the other fibrinolytic enzymes, being a potential source for the development of therapeutic agents in thrombosis treatment. Additional studies are needed to investigate the biochemical properties and biological profile of this enzyme.

Premise: Chaetopeltidales is a small, understudied order of the green algal class Chlorophyceae, that is slowly expanding with the occasional discoveries of novel algae. Here we demonstrate that hitherto unrecognized chaetopeltidaleans also exist among previously described but neglected and misclassified species. Methods: Strain SAG 40.91 of Characium acuminatum, shown by previous preliminary evidence to have affinities with the orders Oedogoniales, Chaetophorales, and Chaetopeltidales (together constituting the OCC clade), was investigated with light and electron microscopy to characterize its morphology and ultrastructure. Sequence assemblies of the organellar and nuclear genomes were obtained and utilized in bioinformatic and phylogenetic analyses to address the phylogenetic position of the alga and its salient genomic features. Results: The characterization of strain SAG 40.91 and a critical literature review led us to reinstate the forgotten genus Hydrocytium A.Braun 1855, with SAG 40.91 representing its type species, Hydrocytium acuminatum. Independent molecular markers converged on placing H. acuminatum as a deeply diverged lineage of the order Chaetopeltidales, formalized as the new family Hydrocytiaceae. Both chloroplast and mitochondrial genomes shared characteristics with other members of Chaetopeltidales and were bloated by repetitive sequences. Notably, the mitochondrial cox2a gene was transferred into the nuclear genome in the H. acuminatum lineage, independently of the same event in Volvocales. The nuclear genome data from H. acuminatum and from another chaetopeltidalean that was reported by others revealed endogenized viral sequences corresponding to novel members of the phylum Nucleocytoviricota. Conclusions: The resurrected genus Hydrocytium expands the known diversity of chaetopeltidalean algae and provides the first glimpse into their virosphere. [ABSTRACT FROM AUTHOR]

A survey was conducted at two sampling sites in the river Torsa for the study of Chlorophyceae from March 2014 to February 2016. A total of 12 chlorophyceae under the seven orders, such as Chlorococcales (with 4 species), Chlamydomonodales and Desmidiaceae (with 2 species) and Oedogoniales, Zyggnematales, Ulotrichales, and Zygnemales (with 1 species) were recorded. The values of the Shannon diversity index and Margalef species richness index indicate the water of the river is of good quality. The seasonal values of the number of taxa and diversity indices were at their maximum in the winter season due to favourable water quality. [ABSTRACT FROM AUTHOR]

Food production is facing challenging times due to the pandemic, and climate change. With production expected to double by 2050, there is a need for a new paradigm in sustainable animal feed supply. Seaweeds offer a highly valuable opportunity in this regard. Seaweeds are classified into three categories: brown (Phaeophyceae), red (Rhodophyceae), and green (Chlorophyceae). While they have traditionally been used in aquafeed, their demand in the feed market is growing, parallelly increasing according to the food demand. Additionally, seaweeds are being promoted for their nutritional benefits, which contribute to the health, growth, and performance of animals intended for human consumption. Moreover, seaweeds contain biologically active compounds such as polyunsaturated fatty acids, antioxidants (polyphenols), and pigments (chlorophylls and carotenoids), which possess beneficial properties, including antibacterial, antifungal, antiviral, antioxidant, and anti-inflammatory effects and act as prebiotics. This review offers a new perspective on the valorization of macroalgae biomass due to their nutritional profile and bioactive components, which have the potential to play a crucial role in animal growth and making possible new sources of healthy food ingredients. [ABSTRACT FROM AUTHOR]

Seaweed farming is an interesting technique to meet the future global food demand. However, it is essential to increase productivity in order to reduce the land surface required and make tank-based production more cost competitive with other food systems. Seaweed productivity is strongly dependent on irradiance, stocking density and nutrients. When nutrients are non-limiting, culture management to increase the productivity has to include the handling of the stocking densities and irradiance at the tanks surface. In this work the light distribution and the average irradiance (named seaweed irradiance Iav,Ulva) in aerated tanks with and without the green alga Ulva ohnoi were studied. Two tanks with opaque walls (small and large tank, 42 and 64 cm diameter, 35 and 30 cm deep, respectively) with stocking densities (SD) from 1 to 5.6 kg m−3, different incident irradiances I0 (from 66 to 696 μmol photons m−2 s−1 at the tank surface) and U. ohnoi with different chlorophyll content (from 77 to 154 µmol chlorophyll m−2) were studied. In the measuring of the Iav,Ulva, statistically significant differences between the different stocking densities, incident irradiances and chlorophyll contents were detected with variance tests. The Iav,Ulva increased with the incident irradiance I0, and decreased with stocking density and chlorophyll content. The percentage of the incident irradiance experienced by the seaweed (%Iav,Ulva) is less than 27% of the incident irradiance in all the configurations and this percentage decreases with increasing stocking density and chlorophyll content. Also, it is shown that Iav,Ulva is much lower than the one predicted with the Lambert–Beer law, the commonly used equation to determine it in tanks with algae. Multiple regression analysis was used to fit a model with three continuous predictors (I0, SD and chlorophyll content), their interactions and polynomial terms of second order to obtain Iav,Ulva in the small and large tank with U. ohnoi. The standardized effects of the terms involving chlorophyll content in the multiple regression model have been greater than the standardized effects of the terms involving SD. The overall evaluation of this final model showed a high goodness-of-fit, with a standard deviation of the distance between the data values and the fitted values equal to 0.4, R2 = 0.994 and R2(adjusted) = 0.992. The inspection of residual plots showed an adequate fit to the data. Furthermore, the value of the predicted R2 equal to 0.981 showed a good predictive capability of the model. The continuous variables stocking density, incident irradiance and chlorophyll content proved to be significant variables to explain and predict the average irradiance Iav,Ulva for the macroalga U. ohnoi. [ABSTRACT FROM AUTHOR]

The taxonomic diversity of the algal genus Meyerella is difficult to study because of its very simple morphology. Within the Chlorella-clade Meyerella members are distinguished from the others by the absence of the pyrenoid. However, it is not possible to identify them only on the basis of light microscopy data without the involvement of molecular genetic analysis methods. Some Meyerella representatives have high biotechnological potential, because they are able to accumulate valuable metabolites, including polyunsaturated fatty acids. As a rule, water bodies are the main habitats for these green microalgae. However, strains ACSSI 428 and ACSSI 429, which described in detail in this study, were isolated from peat cryozems (Sakha Republic, Russia). In this study, a detailed comparative analysis of the morphology, phylogeny and fatty acid profiles of these strains isolated from soil and representatives of other planktonic species, primarily Myerella similis, was carried out. Based on the results obtained, it was found that the studied strains are representatives of a new species with high biotechnological potential – Myerella krienitzii sp. nov. [ABSTRACT FROM AUTHOR]

Green algae of the genus Ulva have been identified as suitable organisms for biomass production and good candidates for the development of seaweed blue-biotech industries. The fluctuation of chemical composition during the growth of the algae, which depends largely on environmental factors, makes the development of rapid phenotyping protocols necessary. In this work the efficacy of Near Infrared Spectroscopy (NIRS) to predict dry matter, mineral fraction, nitrogen, and carbon contents directly from wet untreated samples and from dried samples was studied. Partial least square (PLS) models from spectra recorded on 80 samples were used to predict dry matter, and 44 samples to predict carbon, nitrogen and mineral fraction on a wet and dry weight basis. NIR models developed from spectra acquired on wet samples had good accuracy (R2>0.9) for the prediction of N (on a ww and dw basis) and C (on a ww basis). Models with lower R2 scores have been obtained for dry matter (R2=0.610) and MF (R2=0.506-0.693). The models developed to predict carbon and nitrogen directly on wet and untreated samples present NIRS as a valuable tool to determine these parameters in a rapid and low-cost way, allowing making decisions about the optimal harvesting time. [ABSTRACT FROM AUTHOR]

The genus Ulva is globally distributed and has been thoroughly studied because of its functional biochemical composition, rapid growth rates and opportunistic features, and interest in Ulva cultivation is growing worldwide. In Europe, mostly near- and on-shore flow-through cultivation systems are used and land-based recirculating aquaculture systems (RAS) using fresh water or artificial seawater have not been developed for Ulva. While RAS provides quality control and can be located inland, maintenance costs are high. Using selected strains adapted to low-salinity could reduce seawater production costs and improve the economic feasibility. Therefore, our study assessed how salinity can be used as a tool for strain selection and optimization of functional traits. Growth rates and antioxidant activity of three species (four strains) of tubular and foliose Ulva from the NE-Atlantic and Mediterranean (foliose: Ulva lacinulata – two geographical strains, tubular: Ulva linza and Ulva flexuosa) were followed for three weeks at salinities ranging from 10 to 30 PSU. The tubular strains achieved optimal growth at a lower salinity than U. lacinulata. However, growth rates of both foliose strains were higher than of tubular strains, even at sub-optimal salinity. Therefore, U. lacinulata is a good candidate for RAS with artificial seawater, and the cost of salt can be reduced by up to 33.3% (20 PSU) without significantly reducing the growth rate of U. lacinulata. Higher antioxidant activity was achieved by reducing the salinity to 10 PSU for 10 days, suggesting that the functional traits of cultivated Ulva lacinulata can be optimized prior to harvest. [ABSTRACT FROM AUTHOR]

The ongoing climate changes have resulted from high levels of anthropogenic CO2 being released into the atmosphere in the past decades. Carbon-cutting measures have been proposed to reduce global warming by 2 °C, bringing it back to preindustrial levels. There are several options on hand to meet the need for carbon reduction on a global basis, and one such option refers to CO2 sequestration via the photosynthesis of macroalgae. Species of the green seaweed Ulva are ubiquitous throughout the world oceans; they can maintain fast growth during most seasons thanks to their unique photosynthetic capacity combined with high nitrogen and phosphorous uptake rates. High commodity productions of seaweeds, such as green species of Ulva, can also deliver important additional benefits and ecosystem services, including human food, animal feed, proteins, minerals, or active natural molecules, therefore alleviating human needs shortly. Still, whether seaweeds, in general, can trap CO2 for long periods (100 years) is controversial. Technical and biological gaps need to be resolved before an effective and sustainable seaweed-based mass production intended for the sequestration of CO2 is established. This study elaborates on the potential global use of seaweeds in sequestering carbon and addresses the efficient inorganic carbon uptake and fixation traits of Ulva species. This study also overviews the photosynthetic traits and growth of seaweeds in offshore, semi-controlled, and land-based cultivation settings, focusing on total carbon budgets and footprints for Ulva sp. from the Israeli Mediterranean Sea. Altogether this work addresses the potential use of Ulva sp. as a valuable tool to moderate climate changes. [ABSTRACT FROM AUTHOR]

The article discusses the challenges of studying the biodiversity of algae and other protists. While these organisms are larger than bacteria and archaea, they still require microscopy for identification, and there are few structural characteristics that can be used for diagnosis. Metagenomic analysis, which has been successful for bacteria and archaea, is still developing for algae. The article focuses on the biodiversity of the Klebsormidiophyceae, a group of green algae, and highlights the difficulties in identifying species within this group. The study also explores the evolutionary history and genomic diversity of the Klebsormidiophyceae, revealing discrepancies between genetic and morphological evidence. The article emphasizes the importance of biodiversity discovery and the urgent need to study and describe novel or poorly known taxa before they are lost. [Extracted from the article]

Carbon dots are a new type of carbon-based material with some unique properties which are attractive for agricultural, biological, medical and nanotechnological applications. The widespread production of graphene for composite materials as well as the formation of carbon dots as by-products (industry, food heat treatment etc.) leading to inevitable environmental pollution. However, the environmental impact posed by them on living organisms is still insufficient investigated. We studied the effects of carbon dots synthesized in our laboratory via electrochemical (classified as graphene quantum dots), hydrothermal and microwave (classified as carbon nanodots) methods on the green microalga Scenedesmus quadricauda. The microalgae were exposed to different concentrations of carbon dots for 6 days. Our results showed that carbon dots did not induce oxidative stress and affect the photosynthetic activity of microalgae. However, carbon dots could decrease the growth rate of microalgae mainly due to reducing light, which occurred via the shading of microalgae by nanoparticles. The obtained results contribute to the understanding of the interaction of carbon dots and microalgae. [ABSTRACT FROM AUTHOR]

Microalgae produce a wide range of biomolecules with commercial applications and thus maximizing algal productivity in these systems is of central importance. Although, photosynthesis requires light, microalgae have limited productivity when their photosystem is exposed to excessive light irradiance and become photoinhibited. Here, we perform adaptative laboratory evolution to improve the light harvesting efficiency of Chlamydomonas reinhardtii under high irradiance. In doing so, we also test whether manipulating the genetic variation of the lineages under selection, through UV mutagenesis, or creating mixed strains with a single, or five generations of recombination prior to selection, increases the evolutionary response. Our results indicate that selection under high light increases total pigment production and the ratios of carotenoids to chlorophyll-a and chlorophyll-a to chlorophyll-b. These changes likely increase photoprotection and make the photosystem more efficient by reducing the size of light-harvesting antennae. Measurements of the maximum potential quantum efficiency of Photosystem II suggest that high light intensity selected lines were more stressed under normal light conditions indicative of a trade-off between light environments. Contrary to expectations, we found that different strains responded equally to selection, irrespective of whether they were single or mixed strains or pre-treated with UV radiation. Our study provides further evidence of the utility of adaptative laboratory evolution as a tool for enhancing biomass production and high-light resistance in C. reinhardtii and suggests that significant evolutionary responses can be achieved without the need for mixing or inducing mutations through UV radiation. [ABSTRACT FROM AUTHOR]

Abstract Background Microalgae CO2 fixation results in the production of biomass rich in high-valuable products, such as fatty acids and carotenoids. Enhanced productivity of valuable compounds can be achieved through the microalgae’s ability to capture CO2 efficiently from sources of high CO2 contents, but it depends on the species. Culture collections of microalgae offer a wide variety of defined strains. However, an inadequate understanding of which groups of microalgae and from which habitats they originate offer high productivity under increased CO2 concentrations hampers exploiting microalgae as a sustainable source in the bioeconomy. Results A large variety of 81 defined algal strains, including new green algal isolates from various terrestrial environments, were studied for their growth under atmospheres with CO2 levels of 5–25% in air. They were from a pool of 200 strains that had been pre-selected for phylogenetic diversity and high productivity under ambient CO2. Green algae from terrestrial environments exhibited enhanced growth up to 25% CO2. In contrast, in unicellular red algae and stramenopile algae, which originated through the endosymbiotic uptake of a red algal cell, growth at CO2 concentrations above 5% was suppressed. While terrestrial stramenopile algae generally tolerated such CO2 concentrations, their counterparts from marine phytoplankton did not. The tests of four new strains in liquid culture revealed enhanced biomass and chlorophyll production under elevated CO2 levels. The 15% CO2 aeration increased their total carotenoid and fatty acid contents, which were further stimulated when combined with the starvation of macronutrients, i.e., less with phosphate and more with nitrogen-depleted culture media. Conclusion Green algae originating from terrestrial environments, Chlorophyceae and Trebouxiophyceae, exhibit enhanced productivity of carotenoids and fatty acids under elevated CO2 concentrations. This ability supports the economic and sustainable production of valuable compounds from these microalgae using inexpensive sources of high CO2 concentrations, such as industrial exhaust fumes.

A green alga, Chlorococcum sp. (Chlorococcales, Chlorophyceae), was grown from scrapings of the travertine rocks from the outlet stream of the Emerald Pool, Khlong Thom Nuea, Khlong Thom District Krabi province in Southern Thailand – a classic karstic stream habitat. It was a recalcitrant alga: organic solvents did not extract chlorophyll (Chl) from the algae very well but heated Dimethylsulphoxide (DMSO) was effective. Rapid light curve PAM experiments were used to quantify photosynthetic parameters: Eopt = 275 ± 9.7 µmol photons m–2 s–1, ETRmax = 277 ± 5.99 µmol e– g–1 Chl a s–1, photosynthetic efficiency (Alpha, α0) = 2.248 ± 0.112 e– g–1 Chl a. For Chlorococcum sp. deliberately grown in very low light, Eopt = 290 ± 4.89 µmol photons m–2 s–1 but ETRmax = 109 ± 0.97 µmol e– g–1 Chl a s–1, Alpha (α0) = 1.010 ± 0.192 e– g–1 Chl a. Overall, the amount of Chl b compared with Chl a was relatively low for most Chl a + b organisms (Chl b/a ≈ 0.21) but the ratio was not strongly affected by irradiance. The changes in ETRmax and α0 indicate that the Chlorococcum sp, responded to very low irradiance by increasing total Chl as Chl a, a marginal decrease in Chl b/a ratio but no substantial change in far-red absorption. The spectrum stripping technique confirmed Chlorococcum sp, is a Chl a + b organism albeit with a low Chl b content. Photosynthesis in this species was not very sensitive to pH in the range pH 5–9 but was inhibited at pH 10, indicating that it was very capable of using HCO3– as an inorganic carbon source. Chlorococcum has a carbon concentrating mechanism (CCM), however based on its insensitivity to the depolarizing effects of high [K+], it is unlikely to be dependent on the membrane potential across the cell membrane. The alga is homiochlorophyllous and recovers rapidly from dessication without synthesis of new chlorophyll.

Here, we evaluated the effect of culture depth on the growth and nutrient removal rate of Scenedesmus sp. grown in anaerobically digested abattoir effluent (ADAE) and cultivated semi-continuously in raceway ponds at depths of 14 cm, 17 cm, 20 cm, and 23 cm during Austral winter and summer. Culture medium pH was kept constant at pH 6.5 for all treatments throughout the experimental period using a pH–stat system. Algal cultures grown in summer had 2.3- 2.7 times higher biomass productivity than the same grown in winter. In both seasons, maximum volumetric productivity of this alga was achieved at 14 cm depth (14 cm depth⩾ 17 cm depth⩾ 20 cm depth⩾ 23 cm depth). However, areal biomass productivity of culture grown at 23 cm depth was 12% and 29% higher than that of culture grown at 14 cm depth in winter and summer, respectively. In addition, nitrogen, phosphorus and COD areal removal rates were significantly higher in cultures operated at 23 cm among all treatments in both seasons. The effective quantum yield (Fq'/Fm') in summer was 23 cm depth = 20 cm depth > 17 cm depth = 14 cm depth while it followed 14 cm depth⩾ 17 cm depth⩾ 20 cm depth⩾ 23 cm depth in winter, indicating significance of operational conditions on algal photosynthesis. The outcome of this study shows that, irrespective of the season, operating the culture in higher depths significantly increased areal biomass productivity as well as areal nutrient removal rates when treating ADAE. [ABSTRACT FROM AUTHOR]

The current study was carried out to isolate, identify and characterized fresh water green algae species from ecologically diverse habitats of Tehsil Gujar Khan, District Rawalpindi. A microscopic image data was used to identify algal species. A total of 30 species were recorded that belonged to 4 orders, 11 families, and 14 genera. Clamydomonas reinardtii, Acutodesmus obliquus and Cosmarium isthmocondrum are new record from Pakistan. Among identified taxa, Scenedesmus was the dominant genus with 8 species and their contribution was 26.6%. The 2nd most dominant genus was Cosmarium with 6 species and their contribution was 20%. The other genera Chlorococcum, Ankistrodesmus, Coelastrum, and Closterium were (6.6%). Some genera represented only one (3.3%) species that were Chlamydomonas, Eudorina, Tetraspora, Chlorella, Westella, Pediastrum, Acutodesmus, and Stigeoclonium. Hence, the current study reveals that Gujar Khan, District Rawalpindi is a rich source of green algae and an ideal place for their cultivation. [ABSTRACT FROM AUTHOR]

RESUMO Levantamento florístico do gênero Ulothrix (Ulotrichaceae, Chlorophyceae) no Estado de São Paulo, sudeste do Brasil. Foram identificadas cinco espécies com base em sua morfologia celular externa e interna, descritas em detalhes e ilustradas. Ulothrix tenerrima e U. tenuissima ocorreram em quatro municípios cada uma, U. aequalis var. aequalis f. aequalis em três, U. zonata em dois, e U. subtilissima apenas em um município; U. tenuissima foi presentemente citada pela primeira vez para o Estado de São Paulo.

Mitochondrial ATP synthases form dimers, which assemble into long ribbons at the rims of the inner membrane cristae. We reconstituted detergent-purified mitochondrial ATP synthase dimers from the green algae Polytomella sp. and the yeast Yarrowia lipolytica into liposomes and examined them by electron cryotomography. Tomographic volumes revealed that ATP synthase dimers from both species self-assemble into rows and bend the lipid bilayer locally. The dimer rows and the induced degree of membrane curvature closely resemble those in the inner membrane cristae. Monomers of mitochondrial ATP synthase reconstituted into liposomes do not bend membrane visibly and do not form rows. No specific lipids or proteins other than ATP synthase dimers are required for row formation and membrane remodelling. Long rows of ATP synthase dimers are a conserved feature of mitochondrial inner membranes. They are required for cristae formation and a main factor in mitochondrial morphogenesis.