Search Results (31)

The growth of microalgae poses a significant threat to the preservation of stone heritage, particularly in ornamental fountains and water-related architecture. Traditional chemical cleaning methods, such as quaternary ammonium compounds and chlorine-based solutions, are often ineffective and can be harmful to both the environment and cultural properties. In response, biocleaning, which involves the use of live microorganisms and is part of biorestoration, is gaining prominence in cultural heritage conservation, offering a sustainable alternative to conventional methods. The use of microorganisms antagonistic to microalgae growth has been extensively studied in environmental biotechnology to eliminate harmful algae, though its application in heritage conservation remains limited. This review summarizes current knowledge on bacteria capable of inhibiting microalgae growth, discussing their mechanisms, effectiveness, and potential applications, alongside the environmental and economic benefits and challenges of these methods. By collating and critically assessing available information, this paper aims to serve as a comprehensive resource for conservators, restorers, and researchers interested in innovative and sustainable approaches to combat biodeterioration in stone heritage, thereby fostering the development of effective and environmentally sustainable treatments for such culturally significant properties. Full article

Harmful cyanobacterial blooms (HABs), primarily composed of toxic cyanobacteria like Microcystis aeruginosa, pose a significant threat to aquatic ecosystems and human health. Algicidal bacteria had emerged as a promising strategy for HAB control due to their safety and efficacy. In this study, the algicidal bacterium Streptomyces violaceorubidus lzh-14, isolated from Cha Lake in Dezhou, China, exhibited strong algicidal activity against M. aeruginosa. When bacterial culture was added to algal cultures at a final volume ratio of 10% (v/v), the algicidal activity reached 94.5% ± 1.8% after 72 h. Moreover, S. violaceorubidus lzh-14 showed varying degrees of algicidal activity against other tested cyanobacterial species. Microscopic observation revealed that M. aeruginosa cells treated with lzh-14 became deformed and ruptured, resulting in the leakage of cellular contents. The algicidal substance extracted from S. violaceorubidus lzh-14 demonstrated strong stability under varying temperatures and pH conditions. Based on these findings, algicidal powder was preliminarily developed. This study confirms that S. violaceorubidus lzh-14 and its active substance have potential as effective biocontrol agents against HABs. Full article

The effect of periodical heatwaves and related thermal stratification in freshwater aquatic ecosystems has been a hot research issue. A large dataset of samples was generated from samples exposed to temporary thermal stratification in mesocosms mimicking shallow eutrophic freshwater lakes. Temperature regimes were based on IPCC climate warming scenarios, enabling simulation of future warming conditions. Surface oxygen levels reached 19.37 mg/L, while bottom layers dropped to 0.07 mg/L during stratification. Analysis by FlowCAM revealed dominance of Cyanobacteria under ambient conditions (up to 99.2%), while Cryptophyta (up to 98.9%) and Chlorophyta (up to 99.9%) were predominant in the A2 and A2+50% climate scenarios, respectively. We identified temperature changes and shifts in nutrient concentrations, particularly phosphate, as critical factors in microbial community composition. Furthermore, five distinct Microcystis morphospecies identified by FlowCAM-based analysis were associated with different microbial clusters. The combined use of imaging flow cytometry, which differentiates phytoplankton based on morphological parameters, and nanopore long-read sequencing analysis has shed light into the dynamics of microbial communities associated with different Microcystis morphospecies. In our observations, a peak of algicidal bacteria abundance often coincides with or is followed by a decline in the Cyanobacteria. These findings highlight the importance of species-level classification in the analysis of complex ecosystem interactions and the dynamics of algal blooms in freshwater bodies in response to anthropogenic effects and climate change. Full article

Certain microalgae species have gained traction in the biofuel and food/feed sectors due to their ability to accumulate large amounts of intracellular lipids. However, the extraction of lipids from microalgae is hindered by the presence of complex and recalcitrant cell walls that act as a barrier to mass transfer. This paper examines the intricate details of microalgae cell walls of species belonging to three genera—Nannochloropsis, Scenedesmus, and Schizochytrium—known for their high total lipid contents and omega-3 polyunsaturated fatty acid contents, thus having dual potential for both biofuel and food/feed application. An overview of the techniques used to analyse the cell walls, followed by a detailed description of the cell wall architecture of the three genera and the growth conditions that affect the ultrastructure and composition of their cell walls, is presented. Since cell wall disruption is a crucial step in recovering intracellular products from microalgae biomass, different cell-disruption technologies are also reviewed, focusing specifically on approaches that can be applied directly to wet biomass without the need for biomass drying, thus exerting a low-energy footprint. Enzymatic treatment is operated under mild conditions and offers a promising wet route for targeted recovery of intracellular products from microalgae with minimal side reactions and risk of product degradation. The high cost of enzymes can be mitigated by reducing enzyme requirements through the adoption of a minimal design approach that uses the cell wall composition as the basis to direct enzyme choice and dosage. Different enzyme-recycling and immobilisation strategies to reduce enzyme requirements and improve commercial scalability are also reviewed. Finally, the paper provides a summary of the current state-of-the-art in direct biological approaches using algicidal bacteria and fungi to achieve cell disruption. Overall, the paper provides a roadmap for a more efficient cell disruption of microalgae. Full article

The development of sustainable alternatives to chemical and mechanical biofilm removal for submerged technical devices used in freshwater and marine environments represents a major technical challenge. In this context, the antibiotic impact of blue light with its low absorption underwater provides a potentially useful alternative. However, former technical limitations led to hours of treatment. Here, we applied high-power blue laser irradiation (1500 W) with a wavelength of 448 nm to demonstrate its strong antibiotic and algicidal effect on different bacteria and algae in seconds. High-power blue light treatment (139 W/cm²) for only 8.9 s led to the efficient deactivation of all tested organisms. Analyses of the underlying biological mechanisms revealed the absorption of the blue light by endogenous chromophores (flavins, tetrapyrroles) with the generation of reactive oxygen species (ROS). In agreement, Escherichia coli transcriptome analyses demonstrated a stress response at the level of DNA damage repair, respiration, and protein biosynthesis. Spectroscopic measurements of the irradiated algae indicated the irreversible damage of chlorophyll by photooxidation with the formation of singlet oxygen. In conclusion, high-power blue laser radiation provides a strong sustainable tool for the removal of biofouling in a very short time for applications in aquatic systems. Full article

Ammonium and polyamines are essential nitrogen metabolites in all living organisms. Crosstalk between ammonium and polyamines through their metabolic pathways has been demonstrated in plants and animals, while no research has been directed to explore this relationship in algae or to investigate the underlying molecular mechanisms. Previous research demonstrated that high concentrations of ammonium and putrescine were among the active substances in bacteria-derived algicide targeting dinoflagellates, suggesting that the biochemical inter-connection and/or interaction of these nitrogen compounds play an essential role in controlling these ecologically important algal species. In this research, putrescine, ammonium, or a combination of putrescine and ammonium was added to cultures of three dinoflagellate species to explore their effects. The results demonstrated the dose-dependent and species-specific synergistic effects of putrescine and ammonium on these species. To further explore the molecular mechanisms behind the synergistic effects, transcriptome analysis was conducted on dinoflagellate Karlodinium veneficum treated with putrescine or ammonium vs. a combination of putrescine and ammonium. The results suggested that the synergistic effects of putrescine and ammonium disrupted polyamine homeostasis and reduced ammonium tolerance, which may have contributed to the cell death of K. veneficum. There was also transcriptomic evidence of damage to chloroplasts and impaired photosynthesis of K. veneficum. This research illustrates the molecular mechanisms underlying the synergistic effects of the major nitrogen metabolites, ammonium and putrescine, in dinoflagellates and provides direction for future studies on polyamine biology in algal species. Full article

The role of microorganisms in effectively terminating harmful algal blooms (HABs) is crucial for maintaining environmental stability. Recent studies have placed increased emphasis on bio-agents capable of inhibiting HABs. The bacterium Pseudoalteromonas sp. strain FDHY-MZ2 has exhibited impressive algicidal abilities against Karenia mikimotoi, a notorious global HAB-forming species. To augment this capability, cultures were progressively scaled from shake flask conditions to small-scale (5 L) and pilot-scale (50 L) fermentation. By employing a specifically tailored culture medium (2216E basal medium with 1.5% soluble starch and 0.5% peptone), under precise conditions (66 h, 20 °C, 450 rpm, 30 L/min ventilation, 3% seeding, and constant starch flow), a notable increase in algicidal bacterial biomass was observed; the bacterial dosage required to entirely wipe out K. mikimotoi within a day decreased from 1% to 0.025%. Compared to an unoptimized shake flask group, the optimized fermentation culture caused significant reductions in algal chlorophyll and protein levels (21.85% and 78.3%, respectively). Co-culturing induced increases in algal malondialdehyde and H₂O₂ by 5.98 and 5.38 times, respectively, leading to further disruption of algal photosynthesis. This study underscores the unexplored potential of systematically utilized microbial agents in mitigating HABs, providing a pathway for their wider application. Full article

The dinoflagellate Prorocentrum triestinum forms high biomass blooms that discolor the water (red tides), which may pose a serious threat to marine fauna and aquaculture exploitations. In this study, the algicidal effect of a bacterial strain (0YLH) belonging to the genus Shewanella was identified and evaluated against P. triestinum. The algicidal effects on the dinoflagellate were observed when P. triestinum was exposed to cell-free supernatant (CFS) from stationary-phase cultures of the 0YLH strain. After 24 h exposure, a remarkable reduction in the photosynthetic efficiency of P. triestinum was achieved (55.9%), suggesting the presence of extracellular bioactive compounds produced by the bacteria with algicidal activity. Furthermore, the CFS exhibited stability and maintained its activity across a wide range of temperatures (20–120 °C) and pH values (3–11). These findings highlight the algicidal potential of the bacterium Shewanella halifaxensis 0YLH as a promising tool for the environmentally friendly biological control of P. triestinum blooms. Full article

Harmful cyanobacterial blooms occur worldwide and pose a great threat to aquatic ecosystems and public health. The application of algicidal bacteria represents an eco-friendly strategy for controlling harmful cyanobacterial blooms; thus, searching for a high efficiency of algicidal bacteria has been becoming an important and continuous task in science. Herein, we identified a bacterial strain coded Streptomyces sp. HY with a highly algicidal activity, and investigated its algicidal efficiency and mechanism against Microcystis aeruginosa. The strain HY displayed high algicidal activity toward Microcystis aeruginosa cells, with a removal rate of 93.04% within 2 days via indirect attack. Streptomyces sp. HY also showed the ability to lyse several genera of cyanobacterial strains, including Dolichospermum, Pseudanabaena, Anabaena, and Synechocystis, whereas it showed a minor impact on the green alga Scenedesmus obliquus, demonstrating its selectivity specially for targeting cyanobacteria. Its algicidal mechanism involved damages to the photosynthesis system, morphological injury of algal cells, oxidative stress, and dysfunction of the DNA repair system. Furthermore, HY treatment reduced the expression levels of genes (mcyB and mcyD) related to microcystin biosynthesis and decreased the total content of microcystin-leucine-arginine by 79.18%. Collectively, these findings suggested that the algicidal bacteria HY is a promising candidate for harmful cyanobacterial bloom control. Full article

Algicidal bacteria are important in the control of toxic dinoflagellate blooms, but studies on the environmental behavior of related algal toxins are still lacking. In this study, Bacillus subtilis S3 (S3) showed the highest algicidal activity against Alexandrium pacificum (Group IV) out of six Bacillus strains. When treated with 0.5% (v/v) S3 bacterial culture and sterile supernatant, the algicidal rates were 69.74% and 70.22% at 12 h, respectively, and algicidal substances secreted by S3 were considered the mechanism of algicidal effect. During the algicidal process, the rapid proliferation of Alteromonas sp. in the phycosphere of A. pacificum may have accelerated the algal death. Moreover, the algicidal development of S3 released large amounts of intracellular paralytic shellfish toxins (PSTs) into the water, as the extracellular PSTs increased by 187.88% and 231.47% at 12 h, compared with the treatment of bacterial culture and sterile supernatant at 0 h, respectively. Although the total amount of PSTs increased slightly, the total toxicity of the algal sample decreased as GTX1/4 was transformed by S3 into GTX2/3 and GTX5. These results more comprehensively reveal the complex relationship between algicidal bacteria and microalgae, providing a potential source of biological control for harmful algal blooms and toxins. Full article

Prorocentrum donghaiense is a harmful-algal-bloom-forming species of planktonic dinoflagellates widely distributed around the world, which threatens the marine environment and human health. Bacteria are promising biological agents to control algal growth in HABs. Previously, we isolated an Alteromonas sp. FDHY-03, a P. donghaiense-lysing bacteria strain, from Xiapu Sea area of China. In order to improve the algicidal activity of this strain, we optimized the medium composition and culture conditions. Based on single-factor method experiment design, the optimum medium component of algicidal effect for strain FDHY-03 was sucrose and peptone. The result of Plackett–Burman design indicated that three significant factors (sucrose, peptone, and rotational speed) appeared. Finally, the concentrations of key factors were confirmed by central composite design (CCD) and response surface methodology (RSM). Under the optimized medium, the algicidal rate of strain FDHY-03 against P. donghaiense improved by 67.15%, and the OD₆₀₀ value increased by 2.86-fold. The optimal source and condition were sucrose 0.46% (w/v), peptone 4.25% (w/v) addition, and rotation speed 255 rpm. Overall, this study provides an optimized method and optimum medium for improving the algicidal activity against P. donghaiense, and has a positive influence on algae-lysing bacteria for controlling the blooms of the algae in the environment. Full article

It is widely accepted that eutrophication has played an important role in the formation of harmful cyanobacterial blooms in recent decades, which impacts water quality and ecological environment and causes huge economic losses. Algicidal bacteria have a promising application prospect in controlling cyanobacterial blooms in aquaculture water. Here, the process of the algicidal bacterium Brevibacillus laterosporus strain Bl-zj acting on Microcystis aeruginosa was explored using transcriptome analysis to elucidate the algicidal mechanism. The results of the co-culture of bacterium and alga showed a strong alga-lysing effect of B. laterosporus against M. aeruginosa with an extreme morphology deformation of the algal cells. A total of 2744 differentially expressed genes of B. laterosporus were identified, which were mainly involved in the metabolism of amino acid, carbohydrate, and lipid. In the co-cultured group, the expression of genes mainly enriched in valine, leucine and isoleucine degradation, and fatty acid degradation were significantly increased. However, the expression of the genes related to ribosome were mainly inhibited. Transcriptome analysis showed that B. laterosporus obtained ATP and energy by the degradation of valine, leucine, isoleucine, and fatty acids, and destroyed algal cells by efflux pump transporters, secretion of hydrolytic enzymes, antibiotics, proteases, and other secondary metabolites, resulting in algal death and achieving the algicidal effect. Full article

Algicidal bacteria combined with the ability of aerobic denitrification is considered to be a promising way to control harmful cyanobacterial bloom and remove nitrogen. However, the effect of these bacteria on the vertical distribution of colonial cyanobacteria and nutrients remained unknown. In this study, two algicidal and denitrifying bacteria were respectively co-cultured with the colonial Microcystis aeruginosa to construct the microcosm systems, and then the cyanobacteria number, the ratio of bacterial to cyanobacterial abundance, the content of dissolved nitrogen, phosphorus and organic carbon in different water layers were investigated. The results showed that the distribution difference of Microcystis among the vertical water layers was further enlarged due to the short-term influence of algicidal bacteria Brevundimonas diminuta and Pseudomonas stutzeri. The number of Microcystis in the lower layer was further reduced by the inhibitory effect of the algicidal bacteria. However, there was a dramatic increase in the number of Microcystis in the upper layer, even when the ratio of algicidal bacteria to cyanobacteria increased significantly. B. diminuta and P. stutzeri both greatly promoted the removal of dissolved total nitrogen in the upper and middle layers of cyanobacteria blooming water, but they also boosted the release of dissolved phosphorus in all layers. These results enable us to better understand the possible limitations of algicidal bacteria in their application to control cyanobacteria blooms. Full article

Eutrophication has become an increasingly serious environmental issue and has contributed towards an explosion in harmful algal blooms (HABs) affecting local development. HABs can cause serious threats to ecosystems and human health. A newly isolated algicidal strain, Enterobacter hormaechei F2, showed high algicidal activity against the typical HAB species Microcystis aeruginosa. Potential algicides were detected through liquid chromatograph–mass spectrometer analysis, revealing that prodigiosin is an algicide and PQS is a quorum sensing molecule. RNA-seq was used to understand the algicidal mechanisms and the related pathways. We concluded that the metabolism of prodigiosin and PQS are active at the transcriptional level. The findings indicate that E. hormaechei F2 can be used as a potential biological agent to control harmful algal blooms to prevent the deterioration of the ecological and economic value of water bodies. Full article

The fermentation processes of algicidal bacteria offer an eco-friendly and promising approach for controlling harmful algae blooms (HABs). The strain Ba3, previously isolated and identified as Bacillus sp., displays robust algicidal activity against HABs dinoflagellate in particular. Microbial fermentation products have also been found to provide metabolites with multiple bioactivities, which has been shown to reduce harmful algae species’ vegetative cells and thus reduce red tide outbreaks. In this study, the microbial fermentation of algicidal bacterium Ba3 was analyzed for its potential ability of algicidal compounds. A treatment time increased the algicidal efficiency of the fermentation products against Prorocentrum donghaiense (91%) and Alexandrium tamarense (82%). Among the treatment groups, the changing trend for the 2% treatment group was faster than that for the other treatments, showing that the inhibition rate could reach 99.1% in two days. Active components were separated by organic solvent extraction and macroporous resin, and the molecular weight of the active components was analyzed by LC-MS. The result shows that the microbial fermentation products offer a potential, not practical use for controlling the outbreaks of dinoflagellate blooms. As a result of its potential application for inhibiting HABs, these findings provide an encouraging basis for promoting large-scale fermentation production and the controlling the outbreaks of red tide. Full article