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16 pages, 1658 KiB

Open AccessFeature PaperArticle

Auxin Regulates Apical Stem Cell Regeneration and Tip Growth in the Marine Red Alga Neopyropia yezoensis

by Kensuke Taya, Shunzei Takeuchi, Megumu Takahashi, Ken-ichiro Hayashi and Koji Mikami

Cells 2022, 11(17), 2652; https://doi.org/10.3390/cells11172652 - 26 Aug 2022

Cited by 2 | Viewed by 2269

Abstract

The red alga Neopyropia yezoensis undergoes polarized elongation and asymmetrical cell division of the apical stem cell during tip growth in filamentous generations of its life cycle: the conchocelis and conchosporangium. Side branches are also produced via tip growth, a process involving the [...] Read more.

The red alga Neopyropia yezoensis undergoes polarized elongation and asymmetrical cell division of the apical stem cell during tip growth in filamentous generations of its life cycle: the conchocelis and conchosporangium. Side branches are also produced via tip growth, a process involving the regeneration and asymmetrical division of the apical stem cell. Here, we demonstrate that auxin plays a crucial role in these processes by using the auxin antagonist 2-(1H-Indol-3-yl)-4-oxo-4-phenyl-butyric acid (PEO-IAA), which specifically blocks the activity of the auxin receptor TRANSPORT INHIBITOR RESPONSE1 (TIR1) in land plants. PEO-IAA repressed both the regeneration and polarized tip growth of the apical stem cell in single-celled conchocelis; this phenomenon was reversed by treatment with the auxin indole-3-acetic acid (IAA). In addition, tip growth of the conchosporangium was accelerated by IAA treatment but repressed by PEO-IAA treatment. These findings indicate that auxin regulates polarized tip cell growth and that an auxin receptor-like protein is present in N. yezoensis. The sensitivity to different 5-alkoxy-IAA analogs differs considerably between N. yezoensis and Arabidopsis thaliana. N. yezoensis lacks a gene encoding TIR1, indicating that its auxin receptor-like protein differs from the auxin receptor of terrestrial plants. These findings shed light on auxin-induced mechanisms and the regulation of tip growth in plants. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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13 pages, 2190 KiB

Open AccessArticle

How to Verify Non-Presence—The Challenge of Axenic Algae Cultivation

by Leo Pokorny, Bela Hausmann, Petra Pjevac and Michael Schagerl

Cells 2022, 11(16), 2594; https://doi.org/10.3390/cells11162594 - 20 Aug 2022

Cited by 6 | Viewed by 3385

Abstract

Many phycological applications require the growth and maintenance of pure algae cultures. In some research areas, such as biochemistry and physiology, axenic growth is essential to avoid misinterpretations caused by contaminants. Nonetheless, axenicity—defined as the state of only a single strain being present, [...] Read more.

Many phycological applications require the growth and maintenance of pure algae cultures. In some research areas, such as biochemistry and physiology, axenic growth is essential to avoid misinterpretations caused by contaminants. Nonetheless, axenicity—defined as the state of only a single strain being present, free of any other organism—needs to be verified. We compare the available methods to assess axenicity. We first purified unialgal Limnospira fusiformis cultures with an established series of axenicity treatments, and by including two additional treatment steps. The presumable axenic cultures were then tested for their axenic state by applying conventional tests on LB (lysogeny broth) agar-plates, 16S rRNA gene amplicon sequencing, flow-cytometry and epifluorescence microscopy. Only the plate tests indicated axenic conditions. We found a linear relationship between total cell counts of contaminants achieved by flow cytometry and epifluorescence microscopy, with flow cytometry counts being consistently higher. In addition, 16S rRNA gene amplicon sequencing demonstrated its superiority by not only being an efficient tool for axenicity testing, but also for identification of persistent contaminants. Although classic plate tests are still commonly used to verify axenicity, we found the LB-agar-plate technique to be inappropriate. Cultivation-independent methods are highly recommended to test for axenic conditions. A combination of flow-cytometry and 16S rRNA gene amplicon sequencing complement each other and will yield the most reliable result. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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17 pages, 4523 KiB

Open AccessArticle

Estimating Biomass and Vitality of Microalgae for Monitoring Cultures: A Roadmap for Reliable Measurements

by Michael Schagerl, Rainer Siedler, Eliška Konopáčová and Sameh Samir Ali

Cells 2022, 11(15), 2455; https://doi.org/10.3390/cells11152455 - 8 Aug 2022

Cited by 24 | Viewed by 4026

Abstract

Estimating algal biomass is a prerequisite for monitoring growth of microalgae. Especially for large-scale production sites, the measurements must be robust, reliable, fast and easy to obtain. We compare the relevant parameters, discuss potential hurdles and provide recommendations to tackle these issues. The [...] Read more.

Estimating algal biomass is a prerequisite for monitoring growth of microalgae. Especially for large-scale production sites, the measurements must be robust, reliable, fast and easy to obtain. We compare the relevant parameters, discuss potential hurdles and provide recommendations to tackle these issues. The focus is on optical density and in vivo autofluorescence of chlorophyll, which have proven to be ideal candidates for monitoring purposes. Beyond biomass, cell vitality is also crucial for maintaining cultures. While maximizing biomass yield is often the primary consideration, some applications require adverse growth conditions for the synthesis of high-quality compounds. The non-invasive technique of pulse-amplified modulated (PAM) fluorescence measurements provides an ideal tool and is increasingly being employed due to ever more affordable devices. We compared three devices and studied the robustness of the dark fluorescence yield of photosystem II (Fv/Fm) at various cell densities. Although the so-called inner filter effects influence the fluorescence signal, the resulting Fv/Fm remain stable and robust over a wide range of cell densities due to mutual effects. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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31 pages, 17296 KiB

Open AccessArticle

Phylogeny and Fatty Acid Profiles of New Pinnularia (Bacillariophyta) Species from Soils of Vietnam

by Elena Kezlya, Yevhen Maltsev, Sergei Genkal, Zinaida Krivova and Maxim Kulikovskiy

Cells 2022, 11(15), 2446; https://doi.org/10.3390/cells11152446 - 7 Aug 2022

Cited by 8 | Viewed by 2875

Abstract

We studied the morphology, ultrastructure, and phylogeny of eight soil diatom strains assigned to the Pinnularia genus. Six of these strains, identified by us as new species, are described for the first time. We provide a comprehensive comparison with related species and include [...] Read more.

We studied the morphology, ultrastructure, and phylogeny of eight soil diatom strains assigned to the Pinnularia genus. Six of these strains, identified by us as new species, are described for the first time. We provide a comprehensive comparison with related species and include ecological data. Molecular phylogeny reconstruction using 18S rDNA and rbcL affiliates the new strains with different subclades within Pinnularia, including ‘borealis’, ‘grunowii’ and ‘stomatophora’. We also studied the fatty acid profiles in connection with the emerging biotechnological value of diatoms as a source of lipids. Stearic (36.0–64.4%), palmitic (20.1–30.4%), and palmitoleic (up to 20.8%) acids were the dominant fatty acids in the algae cultured on Waris-H + Si medium. High yields of saturated and monounsaturated fatty acids position the novel Pinnularia strains as a promising feedstock for biofuel production. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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17 pages, 5482 KiB

Open AccessArticle

Regulation of Light Spectra on Cell Division of the Unicellular Green Alga Haematococcus pluvialis: Insights from Physiological and Lipidomic Analysis

by Kuo Zhao, Yanhua Li, Hailong Yan, Qiang Hu and Danxiang Han

Cells 2022, 11(12), 1956; https://doi.org/10.3390/cells11121956 - 17 Jun 2022

Cited by 8 | Viewed by 2269

Abstract

Commercial scale production of natural astaxanthin is currently conducted through cultivation of the green alga Haematococcus pluvialis. This study comprehensively investigated the impact of seven different light spectra on the growth, morphology and photosynthesis of H. pluvialis vegetative cells. Further, the lipidomes [...] Read more.

Commercial scale production of natural astaxanthin is currently conducted through cultivation of the green alga Haematococcus pluvialis. This study comprehensively investigated the impact of seven different light spectra on the growth, morphology and photosynthesis of H. pluvialis vegetative cells. Further, the lipidomes of vegetative H. pluvialis grown under various light spectra were qualitatively and quantitatively analyzed using liquid chromatography/mass spectrometry (LC/MS). The results showed the existence of blue light—alone or with red light—promoted cell division, while pure red light or white light enabled increased cell sizes, cellular pigment, starch and lipid contents, and biomass production. Although the photosynthetic performance of H. pluvialis measured as chlorophyll a fluorescence was not significantly affected by light spectra, the lipid profiles, particularly chloroplast membrane lipids, showed remarkable changes with light spectra. The contents of most lipid species in the blue/red light 1/2 group, which showed the fastest cell division, remained at a moderate level compared with those under other light spectra, indicating the fastest dividing cells were featured by a fine-tuned lipid profile. From biotechnical perspective, this comprehensive study can provide insights into the development of appropriate light regimes to promote the cell density or biomass of H. pluvialis mass culture. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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8 pages, 1549 KiB

Open AccessCommunication

Improving Microalgal Biomass Productivity Using Weather-Forecast-Informed Operations

by Song Gao, Hongxiang Yan, Nathan Beirne, Mark Wigmosta and Michael Huesemann

Cells 2022, 11(9), 1498; https://doi.org/10.3390/cells11091498 - 29 Apr 2022

Cited by 2 | Viewed by 1649

Abstract

The operation of microalgal cultivation systems, such as culture dilution associated with harvests, affects biomass productivity. However, the constantly changing incident light and ambient temperature in the outdoor environment make it difficult to determine the operational parameters that result in optimal biomass growth. [...] Read more.

The operation of microalgal cultivation systems, such as culture dilution associated with harvests, affects biomass productivity. However, the constantly changing incident light and ambient temperature in the outdoor environment make it difficult to determine the operational parameters that result in optimal biomass growth. To address this problem, we present a pond operation optimization tool that predicts biomass growth based on future weather conditions to identify the optimal dilution rate that maximizes biomass productivity. The concept was tested by comparing the biomass productivities of three dilution scenarios: standard batch cultivation (no dilution), fixed-rate dilution (harvest 60% of the culture every three days), and weather-forecast-informed dilution. In the weather-forecast-informed case, the culture was diluted daily, and the dilution ratio was optimized by the operation optimization tool according to the future 24 h weather condition. The results show that the weather-forecast-informed dilution improved the biomass productivity by 47% over the standard batch cultivation and 20% over the fixed-rate dilution case. These results demonstrate that the pond operation optimization tool could help pond operators to make decisions that maximize biomass growth in the field under ever-changing weather conditions. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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17 pages, 3772 KiB

Open AccessFeature PaperArticle

Membrane-Fluidization-Dependent and -Independent Pathways Are Involved in Heat-Stress-Inducible Gene Expression in the Marine Red Alga Neopyropia yezoensis

by Ho Viet Khoa and Koji Mikami

Cells 2022, 11(9), 1486; https://doi.org/10.3390/cells11091486 - 28 Apr 2022

Cited by 2 | Viewed by 2103

Abstract

Heat stress responses are complex regulatory processes, including sensing, signal transduction, and gene expression. However, the exact mechanisms of these processes in seaweeds are not well known. We explored the relationship between membrane physical states and gene expression in the red alga Neopyropia [...] Read more.

Heat stress responses are complex regulatory processes, including sensing, signal transduction, and gene expression. However, the exact mechanisms of these processes in seaweeds are not well known. We explored the relationship between membrane physical states and gene expression in the red alga Neopyropia yezoensis. To analyze heat-stress-induced gene expression, we identified two homologs of the heat-inducible high temperature response 2 (HTR2) gene in Neopyropia seriata, named NyHTR2 and NyHTR2L. We found conservation of HTR2 homologs only within the order Bangiales; their products contained a novel conserved cysteine repeat which we designated the Bangiales cysteine-rich motif. A quantitative mRNA analysis showed that expression of NyHTR2 and NyHTR2L was induced by heat stress. However, the membrane fluidizer benzyl alcohol (BA) did not induce expression of these genes, indicating that the effect of heat was not due to membrane fluidization. In contrast, expression of genes encoding multiprotein-bridging factor 1 (NyMBF1) and HSP70s (NyHSP70-1 and NyHSP70-2) was induced by heat stress and by BA, indicating that it involved a membrane-fluidization-dependent pathway. In addition, dark treatment under heat stress promoted expression of NyHTR2, NyHTR2L, NyMBF1, and NyHSP70-2, but not NyHSP70-1; expression of NyHTR2 and NyHTR2L was membrane-fluidization-independent, and that of other genes was membrane-fluidization-dependent. These findings indicate that the heat stress response in N. yezoensis involves membrane-fluidization-dependent and -independent pathways. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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19 pages, 3211 KiB

Open AccessArticle

Multi-Fold Enhancement of Tocopherol Yields Employing High CO₂ Supplementation and Nitrate Limitation in Native Isolate Monoraphidium sp.

by Rabinder Singh, Asha Arumugam Nesamma, Alka Narula and Pannaga Pavan Jutur

Cells 2022, 11(8), 1315; https://doi.org/10.3390/cells11081315 - 13 Apr 2022

Cited by 11 | Viewed by 2781

Abstract

Tocopherols are the highly active form of the antioxidant molecules involved in scavenging of free radicals and protect the cell membranes from reactive oxygen species (ROS). In the present study, we focused on employing carbon supplementation with varying nitrate concentrations to enhance the [...] Read more.

Tocopherols are the highly active form of the antioxidant molecules involved in scavenging of free radicals and protect the cell membranes from reactive oxygen species (ROS). In the present study, we focused on employing carbon supplementation with varying nitrate concentrations to enhance the total tocopherol yields in the native isolate Monoraphidium sp. CABeR41. The total tocopherol productivity of NR_HC (Nitrate replete + 3% CO₂) supplemented was (306.14 µg·L⁻¹ d⁻¹) which was nearly 2.5-fold higher compared to NR_VLC (Nitrate replete + 0.03% CO₂) (60.35 µg·L⁻¹ d⁻¹). The best tocopherol productivities were obtained in the NL_HC (Nitrate limited + 3% CO₂) supplemented cells (734.38 µg·L⁻¹ d⁻¹) accompanied by a significant increase in cell biomass (2.65-fold) and total lipids (6.25-fold). Further, global metabolomics using gas chromatography-mass spectrometry (GC-MS) was done in the defined conditions to elucidate the molecular mechanism during tocopherol accumulation. In the present study, the Monoraphidium sp. responded to nitrogen limitation by increase in nitrogen assimilation, with significant upregulation in gamma-Aminobutyric acid (GABA). Moreover, the tricarboxylic acid (TCA) cycle upregulation depicted increased availability of carbon skeletons and reducing power, which is leading to increased biomass yields along with the other biocommodities. In conclusion, our study depicts valorization of carbon dioxide as a cost-effective alternative for the enhancement of biomass along with tocopherols and other concomitant products like lipids and carotenoids in the indigenous strain Monoraphidium sp., as an industrial potential strain with relevance in nutraceuticals and pharmaceuticals. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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16 pages, 4948 KiB

Open AccessArticle

The Effect of Variable Light Source and Light Intensity on the Growth of Three Algal Species

by Vitali Bialevich, Vilém Zachleder and Kateřina Bišová

Cells 2022, 11(8), 1293; https://doi.org/10.3390/cells11081293 - 11 Apr 2022

Cited by 31 | Viewed by 5175

Abstract

Light is the essential energy source for autotrophically growing organisms, including microalgae. Both light intensity and light quality affect cell growth and biomass composition. Here we used three green algae—Chlamydomonas reinhardtii, Desmodesmus quadricauda, and Parachlorella kessleri—to study the effects [...] Read more.

Light is the essential energy source for autotrophically growing organisms, including microalgae. Both light intensity and light quality affect cell growth and biomass composition. Here we used three green algae—Chlamydomonas reinhardtii, Desmodesmus quadricauda, and Parachlorella kessleri—to study the effects of different light intensities and light spectra on their growth. Cultures were grown at three different light intensities (100, 250, and 500 µmol m⁻² s⁻¹) and three different light sources: fluorescent lamps, RGB LEDs, and white LEDs. Cultures of Desmodesmus quadricauda and Parachlorella kessleri were saturated at 250 µmol m⁻² s⁻¹, and further increasing the light intensity did not improve their growth. Chlamydomonas reinhardtii cultures did not reach saturation under the conditions used. All species usually divide into more than two daughter cells by a mechanism called multiple fission. Increasing light intensity resulted in an increase in maximum cell size and division into more daughter cells. In Parachlorella kessleri cells, the concentration of photosynthetic pigments decreased with light intensity. Different light sources had no effect on algal growth or photosynthetic pigments. The results show a species-specific response of algae to light intensity and support the use of any white light source for their cultivation without negative effects on growth. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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13 pages, 1445 KiB

Open AccessArticle

Application of Liquid Waste from Biogas Production for Microalgae Chlorella sp. Cultivation

by Egle Sendzikiene and Violeta Makareviciene

Cells 2022, 11(7), 1206; https://doi.org/10.3390/cells11071206 - 3 Apr 2022

Cited by 4 | Viewed by 2425

Abstract

Microalgae biomass is a viable feedstock for a wide range of industries. Recently, there has also been interest in the ability of microalgae biomass applications for biofuel production. In the meantime, the cultivation of microalgae biomass requires high energy costs, and the application [...] Read more.

Microalgae biomass is a viable feedstock for a wide range of industries. Recently, there has also been interest in the ability of microalgae biomass applications for biofuel production. In the meantime, the cultivation of microalgae biomass requires high energy costs, and the application of microalgae for technical purposes is still problematic. A significant part of the cost of biomass arises from the nutrients used for cultivation. Chemical compounds included in the microalgae cultivation media can be replaced by suitable wastes containing nitrogen, phosphorus, and other elements. This could reduce the microalgae biomass cultivation price and allow cheaper biomass to be used for biofuel production. The aim of this work was to comprehensively investigate and optimize the growth process of microalgae using liquid waste (liquid waste after biogas production from sewage sludge and distillers’ grain) as a source of nitrogen and phosphorus, and technical glycerol as a carbon source. It was found that higher levels of waste in the cultivation media were found to inhibit the accumulation of microalgal biomass, with the optimum level corresponding to a nitrogen concentration of 0.08 g/L. The influence of technical glycerol from biodiesel production on the yield of microalgal biomass was investigated, and it was found that the addition of 6% glycerol allows an increase in the concentration of microalgal biomass in the cultivation media, from 18.1 to 20.6%. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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Review

Jump to: Research

17 pages, 944 KiB

Open AccessReview

Cross Talk between Hydrogen Peroxide and Nitric Oxide in the Unicellular Green Algae Cell Cycle: How Does It Work?

by Wojciech Pokora, Szymon Tułodziecki, Agnieszka Dettlaff-Pokora and Anna Aksmann

Cells 2022, 11(15), 2425; https://doi.org/10.3390/cells11152425 - 5 Aug 2022

Cited by 11 | Viewed by 2459

Abstract

The regulatory role of some reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as hydrogen peroxide or nitric oxide, has been demonstrated in some higher plants and algae. Their involvement in regulation of the organism, tissue and single cell development can [...] Read more.

The regulatory role of some reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as hydrogen peroxide or nitric oxide, has been demonstrated in some higher plants and algae. Their involvement in regulation of the organism, tissue and single cell development can also be seen in many animals. In green cells, the redox potential is an important photosynthesis regulatory factor that may lead to an increase or decrease in growth rate. ROS and RNS are important signals involved in the regulation of photoautotrophic growth that, in turn, allow the cell to attain the commitment competence. Both hydrogen peroxide and nitric oxide are directly involved in algal cell development as the signals that regulate expression of proteins required for completing the cell cycle, such as cyclins and cyclin-dependent kinases, or histone proteins and E2F complex proteins. Such regulation seems to relate to the direct interaction of these signaling molecules with the redox-sensitive transcription factors, but also with regulation of signaling pathways including MAPK, G-protein and calmodulin-dependent pathways. In this paper, we aim to elucidate the involvement of hydrogen peroxide and nitric oxide in algal cell cycle regulation, considering the role of these molecules in higher plants. We also evaluate the commercial applicability of this knowledge. The creation of a simple tool, such as a precisely established modification of hydrogen peroxide and/or nitric oxide at the cellular level, leading to changes in the ROS-RNS cross-talk network, can be used for the optimization of the efficiency of algal cell growth and may be especially important in the context of increasing the role of algal biomass in science and industry. It could be a part of an important scientific challenge that biotechnology is currently focused on. Full article

(This article belongs to the Special Issue Growth and Division in Algae)

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