Growth Of Algal Cells Research Articles

Transcriptomic and Metabolomic Analysis Reveal the Effects of Light Quality on the Growth and Lipid Biosynthesis in Chlorella pyrenoidosa.

Light quality has significant effects on the growth and metabolite accumulation of algal cells. However, the related mechanism has not been fully elucidated. This study reveals that both red and blue light can promote the growth and biomass accumulation of Chlorella pyrenoidosa, with the enhancing effect of blue light being more pronounced. Cultivation under blue light reduced the content of total carbohydrate in Chlorella pyrenoidosa, while increasing the content of protein and lipid. Conversely, red light decreased the content of protein and increased the content of carbohydrate and lipid. Blue light induces a shift in carbon flux from carbohydrate to protein, while red light transfers carbon flux from protein to lipid. Transcriptomic and metabolomic analysis indicated that both red and blue light positively regulate lipid synthesis in Chlorella pyrenoidosa, but they exhibited distinct impacts on the fatty acid compositions. These findings suggest that manipulating light qualities can modulate carbon metabolic pathways, potentially converting protein into lipid in Chlorella pyrenoidosa.

Inhibitory Effect of Combined Exposure to Copper Ions and Polystyrene Microplastics on the Growth of Skeletonema costatum

As two significant pollutants, the increased concentrations of copper ions and microplastics in coastal waters pose a substantial threat to the health of marine ecosystems. This study explored the individual and combined toxic effects of copper ions and microplastics on the marine diatom Skeletonema costatum. The results indicated that copper ions at a concentration of 0.05 mg/L exerted a negative impact on the growth of S. costatum; however, the influence of microplastics on algal cell growth was more complex: there was no significant inhibition of algal cell growth observed within the first 72 h of cultivation, but a pronounced negative effect on cell growth was noted between 72 and 96 h, with high concentrations (10.00 mg/L) of microplastics even causing a premature stagnation phase in algal cell growth. When both pollutants were present simultaneously, their impact on cell growth was similar to that of the microplastic pollution group, yet the growth condition was better than that of the copper ion pollution group. Through investigation of adsorption rates and toxicity mitigation rates, it was found that the adsorption of copper ions by microplastics was a significant reason for the improved growth condition of algal cells in the mixed pollution group compared to the copper ion pollution group. However, in the later stages of cultivation, the inhibitory effect of microspheres on algal cell growth counteracted their mitigating effect on copper ion toxicity. This study provides a reference for evaluating the impact of microplastics and heavy metals on coastal ecosystem health and for revealing the interactions between different pollutants.

Effects of aggregation and settling of photoactive TiO2 nanoparticles on Microcystis aeruginosa and extracellular matters release

Owing to their diverse applications, TiO2-nanoparticles have been extensively discharged into the aquatic environment, posing serious threats to aquatic life and human health. Meanwhile, the aquatic organisms such as cyanobacteria affect the mobility and fate of the nanoparticles, in turn, these aquatic organisms also may be influenced by the nanoparticles, and which further elicits more hazard to ecosystem. In this study, the different concentration of TiO2 nanoparticles were added into the algal solution to observe the status of TiO2 nanoparticles and assess their influences, especially for photocatalytic toxicity on algal growth. The results demonstrated that algal cells and extracellular polymeric substances (EPS) simultaneously affected the TiO2 aggregation and settling in algae culture. In addition, TiO2 NPs inhibited the growth of algal cells through the multiple effects on the light adsorption, photosynthetic activity, oxidative stress and lipid peroxidation. Particularly, the reactive oxygen species generated by photoactive TiO2 NPs caused the changes of EPS and microcystin-LR (MC-LR) release, and these extracellular matters were crucial intermediate to the state of TiO2 NPs and algal cells growth. This study will not only be significant for understanding TiO2 behavior in the real aquatic environment but also be helpful for exploring the effects of TiO2 nanoparticles on cyanobacteria, especially for the released extracellular matters.

Conversion of Retinoids along the Marine Food Chain Contributes to Adverse Impacts on the Spine, Liver, and Intestinal Health of the Marine Medaka (Oryzias melastigma).

Marine microalgae serve as an aquaculture bait. To enhance algal cell growth and breeding profits, high-intensity light conditions are standard for cultivating bait microalgae, potentially altering microalgal metabolite production. This research revealed that Thalassiosira pseudonana, when subjected to high-intensity light conditions, accumulated significant quantities of retinal (RAL) that transferred through the food chain and transformed into all-trans retinoic acid (atRA) in marine medaka. The study further explored the toxic effects on individual fish and specific tissues, as well as the mechanisms behind this toxicity. The accumulation of atRA in the liver, intestine, and spinal column resulted in structural damage and tissue inflammation, as well as oxidative stress. It also down-regulated the gene transcription levels of key pathways involved in immune function and growth. Furthermore, it disrupted the homeostasis of the intestinal microbial communities. The implications for wildlife and human health, which are influenced by the regulation of microalgal metabolite accumulation and their transfer via the food chain, require further investigation and could hold broader significance.

A high throughput array microhabitat platform reveals how light and nitrogen colimit the growth of algal cells

A mechanistic understanding of algal growth is essential for maintaining a sustainable environment in an era of climate change and population expansion. It is known that algal growth is tightly controlled by complex interactive physical and chemical conditions. Many mathematical models have been proposed to describe the relation of algal growth and environmental parameters, but experimental verification has been difficult due to the lack of tools to measure cell growth under precise physical and chemical conditions. As such, current models depend on the specific testing systems, and the fitted growth kinetic constants vary widely for the same organisms in the existing literature. Here, we present a microfluidic platform where both light intensity and nutrient gradients can be well controlled for algal cell growth studies. In particular, light shading is avoided, a common problem in macroscale assays. Our results revealed that light and nitrogen colimit the growth of algal cells, with each contributing a Monod growth kinetic term in a multiplicative model. We argue that the microfluidic platform can lead towards a general culture system independent algal growth model with systematic screening of many environmental parameters. Our work advances technology for algal cell growth studies and provides essential information for future bioreactor designs and ecological predictions.

Effects of clarithromycin exposure on the growth of Microcystis aeruginosa and the production of algal dissolved organic matter

Antibiotics are commonly found in the aquatic environment, which can affect microbial community compositions and activities, and even have potential adverse impacts on human and ecosystem health. The current understanding of the effects of antibiotics on microalgae growth and algal dissolved organic matter (DOM) remains indistinct. To understand the toxic effects of antibiotics on the microalgae, Microcystis aeruginosa was exposed to clarithromycin (CLA) in this study. Cell density determination, chlorophyll content determination, and organic spectrum analysis were conducted to show the effect of CLA exposure on the growth, photosynthetic activity, and organic metabolic processes of Microcystis aeruginosa. The findings revealed that the physiological status of algae could be significantly influenced by CLA exposure in aquatic environments. Specifically, exposure to 1 μg/L CLA stimulated the growth and photosynthetic activity of algal cells. Conversely, CLA above 10 μg/L led to the inhibition of algal cell growth and photosynthesis. Notably, the inhibitory effects intensified with the increasing concentration of CLA. The molecular weight of DOM produced by Microcystis aeruginosa increased when exposed to CLA. Under the exposure of 60 μg/L CLA, a large number of algal cells ruptured and died, and the intracellular organic matter was released into the algal liquid. This resulted in an increase in high molecular weight substances and soluble microbial-like products in the DOM. Exposure to 1 and 10 μg/L CLA stimulated Microcystis aeruginosa to produce more humic acid-like substances, which may be a defense mechanism against CLA. The results were useful for assessing the effects of antibiotic pollution on the stability of the microalgae population and endogenous DOM characteristics in aquatic ecosystems.

Uptake and cellular responses of Microcystis aeruginosa to PFOS in various environmental conditions

Although PFOS has been banned as a persistent organic pollutant, it still exists in large quantities within the environment, thus impacting the health of aquatic ecosystems. Previous studies focused solely on high PFOS concentrations, disregarding the connection with environmental factors. To gain a more comprehensive understanding of the PFOS effects on aquatic ecosystems amidst changing environmental conditions, this study investigated the cellular responses of Microcystis aeruginosa to varying PFOS concentrations under heatwave and nutrient stress conditions. The results showed that PFOS concentrations exceeding 5.0 µg/L had obvious effects on multiple physiological responses of M. aeruginosa, resulting in the suppression of algal cell growth and the induction of oxidative damage. However, PFOS concentration at levels below 20.0 µg/L has been found to enhance the growth of algal cells and trigger significant oxidative damage under heatwave conditions. Heatwave conditions could enhance the uptake of PFOS in algal cells, potentially leading to heightened algal growth when PFOS concentration was equal to or less than 5.0 µg/L. Conversely, deficiency or limitation of nitrogen and phosphorus significantly decreased algal abundance and chlorophyll content, inducing severe oxidative stress that could be mitigated by exposure to PFOS. This study holds significance in managing the impact of PFOS on algal growth across diverse environmental conditions.

Ecotoxicology Evaluation of a Fenton-Type Process Catalyzed with Lamellar Structures Impregnated with Fe or Cu for the Removal of Amoxicillin and Glyphosate.

Antibiotics and pesticides, as well as various emerging contaminants that are present in surface waters, raise significant environmental concerns. Advanced oxidation processes, which are employed to eliminate these substances, have demonstrated remarkable effectiveness. However, during the degradation process, by-products that are not completely mineralized are generated, posing a substantial risk to aquatic ecosystem organisms; therefore, it is crucial to assess effluent ecotoxicity following treatment. This study aimed to assess the toxicity of effluents produced during the removal of amoxicillin and glyphosate with a Fenton-type process using a laminar structure catalyzed with iron (Fe) and copper (Cu). The evaluation included the use of Daphnia magna, Selenastrum capricornutum, and Lactuca sativa, and mutagenicity testing was performed using strains TA98 and TA100 of Salmonella typhimurium. Both treated and untreated effluents exhibited inhibitory effects on root growth in L. sativa, even at low concentrations ranging from 1% to 10% v/v. Similarly, negative impacts on the growth of algal cells of S. capricornutum were observed at concentrations as low as 0.025% v/v, particularly in cases involving amoxicillin-copper (Cu) and glyphosate with copper (Cu) and iron (Fe). Notably, in the case of D. magna, mortality was noticeable even at concentrations of 10% v/v. Additionally, the treatment of amoxicillin with double-layer hydroxides of Fe and Cu resulted in mutagenicity (IM ≥ 2.0), highlighting the necessity to treat the effluent further from the advanced oxidation process to reduce ecological risks.

Sustainable Coating Based on Zwitterionic Functionalized Polyurushiol with Antifouling and Antibacterial Properties.

Zwitterionic polymer coatings facilitate the formation of hydration layers via electrostatic interactions on their surfaces and have demonstrated efficacy in preventing biofouling. They have emerged as a promising class of marine antifouling materials. However, designing multifunctional, environmentally friendly, and natural products-derived zwitterionic polymer coatings that simultaneously resist biofouling, inhibit protein adhesion, exhibit strong antibacterial properties, and reduce algal adhesion is a significant challenge. This study employed two diisocyanates as crosslinkers and natural urushiol and ethanolamine as raw materials. The coupling reaction of diisocyanates with hydroxyl groups was employed to synthesize urushiol-based precursors. Subsequently, sulfobetaine moieties were introduced into the urushiol-based precursors, developing two environmentally friendly and high-performance zwitterionic-functionalized polyurushiol antifouling coatings, denoted as HUDM-SB and IPUDM-SB. The sulfobetaine-functionalized polyurushiol coating exhibited significantly enhanced hydrophilicity, with the static water contact angle reduced to less than 60°, and demonstrated excellent resistance to protein adhesion. IPUDM-SB exhibited antibacterial efficacy up to 99.9% against common Gram-negative bacteria (E. coli and V. alginolyticus) and Gram-positive bacteria (S. aureus and Bacillus. sp.). HUDM-SB achieved antibacterial efficacy exceeding 95.0% against four bacterial species. Furthermore, the sulfobetaine moieties on the surfaces of the IPUDM-SB and HUDM-SB coatings effectively inhibited the growth and reproduction of algal cells by preventing microalgae adhesion. This zwitterionic-functionalized polyurushiol coating does not contain antifouling agents, making it a green, environmentally friendly, and high-performance biomaterial-based solution for marine antifouling.

Inhibition of growth for Microcystis aeruginosa by insertion of iron ion into biochar modified copper metal organic framework (Fe3O4-BC@Cu-MOF-74) under visible light

Microcystis aeruginosa (M. aeruginosa) was a kind of harmful algae in various aquatic ecosystems, which has caused much public concern. The existing algae removal methods showed disadvantages such as incomplete algae removal and excessive capital investment. Based on the specificity of algal cells, insertion of iron ion into biochar-modified copper metal organic framework (Fe3O4-BC@Cu-MOF-74) was synthesized by biochar and MOF with the introduction of Fe3O4. Fe3O4-BC@Cu-MOF-74 was thin, porous and stable. C, O, Fe, and Cu were mainly contained, and it was characterized by peaks (111), (220), (331), (111), (400), (331) and (024) in crystal planes and C–O bonds, Cu–O bonds and O–H bonds were contained. Algal cell growth was significantly inhibited, with a growth inhibition efficiency of 32.21 % by Fe3O4-BC@Cu-MOF-74 under visible light. Chlorophyll-a was reduced by nearly 60 %. The high concentration of oxygen and hydroxyl radicals in the complex accelerated the oxidative process in cells, leading to oxidative stress, which triggered an increase in the concentration of relevant antioxidant enzymes, leading to an increase in soluble protein content. The presence of Cu2+, Fe2+ and Fe3+ could also attack and damage the cell membrane surface, leading to cell rupture and death. Fe3O4-BC@Cu-MOF-74 showed a promising application in the problem of inhibiting the growth of M. aeruginosa under visible light.

Aquatic plant allelochemicals inhibit the growth of microalgae and cyanobacteria in aquatic environments.

Excess nitrogen and phosphorus nutrients in the aquatic environment result in the growth of algal cells and water eutrophication, which adversely affect the aquatic environment and human health. Therefore, discovering a safe and efficient algae suppression method is necessary to ensure the ecological safety of water. Recently, the allelopathic effects of aquatic plants on algae have attracted extensive attention from researchers. This review demonstrates the current research hotspot of allelopathic algal inhibition in aquatic plants and lists the common aquatic plant species and allelochemicals. In addition, the inhibition mechanism of allelochemicals from aquatic plants on algae is systematically discussed. Moreover, the key factors affecting the inhibition of allelopathy in algae, such as pH, temperature, algal cell density, and concentration of allelochemicals, are summarized. The present utilization modes of allelochemicals on algae are also presented. Finally, the problems existing in the study of allelopathic algal inhibition of aquatic plants are highlighted, and suggestions for further research are proposed.

High light and temperature enhancing astaxanthin production in Microcystis aeruginosa—Providing a potential thought for controlling cyanobacterial blooms through resource utilization

Artificial salvage is the common method to control cyanobacterial blooms that easily outbreak in summer, but the salvaged cyanobacteria are not effectively utilized. Microcystis aeruginosa is a typical species in cyanobacterial blooms and can accumulate astaxanthin. To promote cyanobacterial blooms control through producing astaxanthin as resource utilization manner, the algal cell growth, photosynthetic abilities, astaxanthin and its precursor levels as well as related gene expression in M. aeruginosa was investigated under high light (HL) and high temperature (HT), the typical conditions in summer. Under HL and HT conditions, M. aeruginosa cell growth and photosynthetic abilities were reduced, due to the declined chlorophyll content and down-regulated photosynthesis-related gene expression. During the 5 days, the astaxanthin content was gradually increased with elevating the light intensity and temperature, reaching the maximum level under HL at 1000 μmol·m−2·s−1 and HT at 35 °C. However, the precursor (β-carotene and zeaxanthin) levels were gradually decreased. This indicated that HL and HT can promote astaxanthin generation and the precursor transformation, as the expression of the genes related with methylerythritol-4-phosphate pathway and astaxanthin formation was up-regulated. Therefore, summer weather can promote astaxanthin accumulation in cyanobacteria by raising related gene expression. During cyanobacterial blooms in summer, their enormous biomass and high astaxanthin level provide a potential for astaxanthin production, while the cyanobacteria salvaged in other seasons can be cultured under HL (1000 μmol·m−2·s−1) and HT (35 °C) conditions to improve astaxanthin content for extracting the high-value compound, which are beneficial to promoting cyanobacterial blooms control through salvage and resource utilization.

The influence of spermidine on the build-up of fucoxanthin in Isochrysis sp. Acclimated to varying light intensities

Spermidine is a type of important growth regulator, which involved in the biosynthesis of photosynthetic pigments, and has the function of promoting cell proliferation. In this study, Isochrysis sp. was selected as the research object to explore the effects of spermidine supplementation on the growth of algal cells and fucoxanthin synthesis under different light intensities. The results showed that the cell density (5.40 × 106 cells/mL) of algae were the highest at 11 days under the light intensity of 200 μmol·m−2·s−1 and spermidine content of 150 μM. The contents of diadinoxanthin (1.09 mg/g) and fucoxanthin (6.11 mg/g) were the highest when spermidine was added under low light intensity, and the growth of algal cells and fucoxanthin metabolism were the most significant. In the carotenoid synthesis pathway, PDS (phytoene desaturase) was up-regulated by 1.96 times and VDE (violaxanthin de-epoxidase) was down-regulated by 0.95 times, which may promote fucoxanthin accumulation.

Elevated nano-α-Fe2O3 enhances arsenic metabolism and dissolved organic carbon release of Microcystis aeruginosa under a phytate environment.

Little information is available on the effects of nano-α-Fe2O3 on arsenic (As) metabolism of algae and potential associated carbon (C) storage in As-contaminated water with dissolved organic phosphorus (DOP) as a phosphorus (P) source. In this study, Microcystis aeruginosa (M. aeruginosa) was used to investigate impacts of nano-α-Fe2O3 on cell growth and As metabolism of algae under a phytate (PA) environment as well as potential associated C storage. Results showed that nano-α-Fe2O3 had a subtle influence on algal cell growth in a PA environment. Herein, algal cell density (OD680) and chlorophyll a (Chla) were inhibited at elevated nano-α-Fe2O3 levels, which simultaneously limited the decrease of Yield. As suggested, the complexation of PA with nano-α-Fe2O3 could alleviate the negative influence on algal cell growth. Furthermore, the elevated nano-α-Fe2O3 increased As methylation in the PA environment due to higher monomethylarsenic (MMA) and dimethylarsenic (DMA) concentrations in the test media. Additionally, microcystins (MCs) in the media changed consistently with UV254, both of which were relatively lower at 10.0 mg·L-1 nano-α-Fe2O3. Enhanced As(V) methylation of algal cells was found to simultaneously reduce the release risk of As(III) and MC while increasing dissolved organic carbon (DOC) content in media, suggesting unfavorable C storage. Three-dimensional fluorescence analysis revealed that the main DOC constituent was the tryptophan-like component in aromatic proteins. Correlation analysis showed that decreases in pH and the zeta potential and an increase in Chla may lead to metabolic As improvements in M. aeruginosa. The obtained findings highlight the need for greater focus on the potential risks of DOP combined with nano-α-Fe2O3 on algal blooms as well as the biogeochemical cycling processes of As and C storage in As-contaminated water with DOP as the P source.

Elevated pCO2 alleviates the toxic effects of polystyrene nanoparticles on the marine microalga Nannochloropsis oceanica

Concerns about the environmental effects of nanoplastics on marine ecosystems are increasing. Ocean acidification (OA) has also become a global environmental problem. Plastic pollution occurs concomitantly with anthropogenic climate stressors such as OA. However, the combined effects of NP and OA on marine phytoplankton are still not well understood. Therefore, we have investigated the behavior of ammonia (NH2) polystyrene nanoparticles (PS NP) in f/2 medium under 1000 μatm pCO2 and discussed the toxicity of PS NP (100 nm; 0.5 and 1.5 mg/L) on Nannochloropsis oceanica under long and short-term acidification (LA and SA; pCO2 ~ 1000 μatm). We observed PS NP suspended in pCO2 1000 μatm f/2 medium aggregated to a size greater than nanoscale (1339.00 ± 76.10 nm). In addition, we found that PS NP significantly inhibited the growth of N. oceanica at two concentrations, which also produced oxidative stress. Whereas, the growth of algal cells under the coupling of acidification and PS NP was significantly better than that of single PS NP exposure. This indicated that acidification significantly alleviated the toxic effects of PS NP on N. oceanica, and long-term acidification can even promote the growth of N. oceanica under low-density NP. To further understand the mechanism, we analyzed a comparative transcriptome. The results showed that PS NP exposure inhibited the expression of genes involved in the TCA cycle. The acidification was possibly reflected in ribosomes and corresponding processes, which alleviated the negative effects of PS NP on N. oceanica by promoting the synthesis of related enzymes and proteins. This study provided a theoretical basis for assessing the damage of NP to marine phytoplankton under OA. We propose that future studies evaluating the toxicology of NP to marine ecology should consider the changing ocean climate.

Mixotrophic culture of Chaetoceros sp. and its response to circadian rhythm

Chaetoceros sp. is widely used in aquaculture due to its high nutritional value. However, the low growth rate and poor light adaptability of Chaetoceros sp. limit their applications as aquatic food. In this study, the effects of different carbon and nitrogen sources on the growth of algal cells were studied. The highest algal cell density was 5.25*l06 cells/mL when glycerol concentration was 5.0 g/L in the mixotrophic culture. Correspondingly, the maximum algal cell density was 6.23*106 cells/mL when the concentration of nitrogen urea was 0.075 g/L. The lipid content was significantly increased to 156.5 mg/L under the mixotrophic culture. The characteristics of the response of Chaetoceros sp. to circadian rhythm were further studied. The dynamic analysis of cell volume showed that algal cell volume varied greatly under various culture conditions. Compared with the autotrophic model, the algal cell volume of the mixotrophic culture had a faster growth rate in the dark stage, with a peak at 8 h, which confirmed that there was sufficient energy for further cell growth in the dark stage under the mixotrophic culture.

The effects of exogenous amino acids on production of microcystin variants in Microcystis aeruginosa

Dissolved free amino acids are a significant component of dissolved organic nitrogen (DON) in natural waterbodies. The effects of four amino acids (glutamic acid, phenylalanine, leucine, and arginine) on the growth and microcystins (MCs) production of Microcystis aeruginosa were studied in batch culture. The profiles of five MCs variants and the expression levels of target genes involved in MCs biosynthesis and nitrogen metabolism were measured. When amino acids were used as the sole nitrogen source instead of nitrate at different levels (0.5, 2.0 and 8.0 mg/L based on N) in BG-11 medium, algal cell growth and intracellular MCs quotas were inhibited slightly by the treatments with glutamic acid and arginine. The treatments with phenylalanine and leucine, on the other hand, had a strong inhibitory effect on algal cell growth and MCs production. Moreover, the concentrations of Chlorophyll a, phycocyanin and allophycocyanin in cells cultured in glutamic acid, leucine and phenylalanine were lower than those in the control group with nitrate as nitrogen source. The existence of leucine or phenylalanine can lead to a significant increase in the relative abundance of MCs variants structured with the corresponding amino acids. The expression of microcystin-producing gene mcyD was downregulated while the gene pipX associated with nitrogen metabolism was upregulated during the cultivation of M. aeruginosa with amino acids as sole nitrogen source. M. aeruginosa undergoes significant alterations due to exogenous amino acids and exhibits advanced strategies for MCs production.

Bioremoval efficiency and metabolomic profiles of cellular responses of Chlorella pyrenoidosa to phenol and 4-fluorophenol

Abstract We examined the growth tolerance, bioremoval efficacy, and metabolomic profiles of the cellular responses of Chlorella pyrenoidosa to phenol and 4-fluorophenol. We found that C. pyrenoidosa can tolerate exposure to 100 mg/L of phenol and 4-fluorophenol, and the growth of algal cells had a significant hormesis of inhibition first and then promotion. Up to 70% bioremoval of phenol and 4-fluorophenol may occur after 240 h of treatment. Superoxide dismutase (SOD) and CAT activities, malondialdehyde (MDA) content, and reactive oxygen species (ROS) in algal cells in the phenol- and 4-fluorophenol-treated groups were similar or lower than in the control group. Furthermore, photosynthetic pigment and glycerophospholipid contents were significantly upregulated in both phenol- and 4-fluorophenol-treated groups, as indicated by the metabolomic analysis of C. pyrenoidosa, resulting in the vigorous growth of algal cells compared to the control group. Therefore, C. pyrenoidosa can be an excellent biosorbent for phenol and 4-fluorophenol.

Isolation and characterization of algicidal bacteria from freshwater aquatic environments in China.

Algicidal bacteria can inhibit the growth of algae or lyse algal cells, thus playing roles in shaping aquatic microbial communities and maintaining the functions of aquatic ecosystems. Nevertheless, our understanding of their diversities and distributions remains limited. In this study, we collected water samples from 17 freshwater sites in 14 cities in China and screened a total of 77 algicidal bacterial strains using several prokaryotic cyanobacteria and eukaryotic algae as target strains. According to their target-specificities, these strains were classified into three subgroups, cyanobacterial algicidal bacteria, algal algicidal bacteria, and broad-target algicidal bacteria, each displaying distinctive compositions and geographical distribution patterns. They are assigned to Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes bacterial phyla, of which Pseudomonas and Bacillus are the most abundant gram-negative and gram-positive genus, respectively. A number of bacterial strains, such as Inhella inkyongensis and Massilia eburnean, are suggested as new algicidal bacteria. The diverse taxonomies, algal-inhibiting abilities and distributions of these isolates have suggested that there are rich algicidal bacterial resources in these aquatic environments. Our results provide new microbial resources for algal-bacterial interaction studies, and shed new insights into how algicidal bacteria can be used in the control of harmful algal blooms, as well as in algal biotechnology.

The ecotoxicological effects of chromium (III) oxide nanoparticles to Chlorella sp.: perspective from the physiological and transcriptional responses.

Extensive application of nanomaterials enlarges its concentrations in the aquatic environments and poses a threat to algae. This study comprehensively analyzed the physiological and transcriptional responses of Chlorella sp. after being exposed to chromium (III) oxide nanoparticles (nCr2O3). The nCr2O3 at 0-100mg/L presented adverse effects on cell growth (96h EC50 = 16.3mg/L), decreasing the photosynthetic pigment concentrations and photosynthetic activity. Moreover, more extracellular polymeric substances (EPS), especially polysaccharides in soluble EPS, were produced in algae cell, which mitigated the damage of nCr2O3 to cells. However, with the increase of nCr2O3 doses, the EPS protective responses were exhausted, accompanied by toxicity in the form of organelle damage and metabolic disturbance. The enhanced acute toxicity was closely related to the physical contact of nCr2O3 with cells, oxidative stress, and genotoxicity. Firstly, large amounts of nCr2O3 aggregated around and were attached to cells, causing physical damage. Then, the intracellular reactive oxygen species and malondialdehyde levels were significantly increased that led to lipid peroxidation, especially at 50-100mg/L nCr2O3. Finally, the transcriptomic analysis further revealed that the transcription of ribosome, glutamine, and thiamine metabolism-related genes were impaired under 20mg/L nCr2O3, suggesting nCr2O3 inhibited algal cell growth through metabolism, cell defense, and repair, etc.