Microzooplanktonic grazers – A potentially devastating threat to the commercial success of microalgal mass culture

Day, John; Gong, Yingchun

doi:10.1016/j.algal.2017.08.024

Cited by 124 publications

(82 citation statements)

References 88 publications

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“…Euplotids, one of the most common families of free‐living ciliates, play important roles as both predators of microalgae and preys of multicellular eukaryotes in global waters (Dhanker, Kumar, Tseng, & Hwang, ; Sheng, He, Zhao, Shao, & Miao, ; Zhao, Yi, Warren, & Song, ). They have been widely used for decades as model organisms in studies of predator/prey relationships (Kusch, ; Wiąckowski & Szkarłat, ), cell signalling (Hadjivasiliou, Iwasa, & Pomiankowski, ; Jerka‐Dziadosz, Dosche, Kuhlmann, & Heckmann, ), toxicology of marine pollutants (Trielli et al, ) and experimental ecology (Day, Gong, & Hu, ; Walton, Gates, Kloos, & Fisher, ; Xu, Song, & Warren, ). Euplotids are notable for their ability to survive under extreme environmental stresses.…”

Section: Introductionmentioning

confidence: 99%

Genome analyses of the new model protist Euplotes vannus focusing on genome rearrangement and resistance to environmental stressors

Chen

Jiang

Gao

et al. 2019

Molecular Ecology Resources

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As a model organism for studies of cell and environmental biology, the free‐living and cosmopolitan ciliate Euplotes vannus shows intriguing features like dual genome architecture (i.e., separate germline and somatic nuclei in each cell/organism), “gene‐sized” chromosomes, stop codon reassignment, programmed ribosomal frameshifting (PRF) and strong resistance to environmental stressors. However, the molecular mechanisms that account for these remarkable traits remain largely unknown. Here we report a combined analysis of de novo assembled high‐quality macronuclear (MAC; i.e., somatic) and partial micronuclear (MIC; i.e., germline) genome sequences for E. vannus, and transcriptome profiling data under varying conditions. The results demonstrate that: (a) the MAC genome contains more than 25,000 complete “gene‐sized” nanochromosomes (~85 Mb haploid genome size) with the N50 ~2.7 kb; (b) although there is a high frequency of frameshifting at stop codons UAA and UAG, we did not observe impaired transcript abundance as a result of PRF in this species as has been reported for other euplotids; (c) the sequence motif 5′‐TA‐3′ is conserved at nearly all internally‐eliminated sequence (IES) boundaries in the MIC genome, and chromosome breakage sites (CBSs) are duplicated and retained in the MAC genome; (d) by profiling the weighted correlation network of genes in the MAC under different environmental stressors, including nutrient scarcity, extreme temperature, salinity and the presence of ammonia, we identified gene clusters that respond to these external physical or chemical stimulations, and (e) we observed a dramatic increase in HSP70 gene transcription under salinity and chemical stresses but surprisingly, not under temperature changes; we link this temperature‐resistance to the evolved loss of temperature stress‐sensitive elements in regulatory regions. Together with the genome resources generated in this study, which are available online at Euplotes vannus Genome Database (http://evan.ciliate.org), these data provide molecular evidence for understanding the unique biology of highly adaptable microorganisms.

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Section: Introductionmentioning

confidence: 99%

Genome analyses of the new model protist Euplotes vannus focusing on genome rearrangement and resistance to environmental stressors

Chen

Jiang

Gao

et al. 2019

Molecular Ecology Resources

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“…, the higher biomass concentration in these PBRs has been reported to strengthen microalgae culture and protect it against grazers(Day et al, 2017;Fernández et al, 2016), making it more consistent. However, increasing biomass concentration in the 10-cm MPBR plant involved a rise in sCOD concentration from 76 ± 39 mg CODꞏL -1 in the 25-cm MPBR plant to 197± 114 mg CODꞏL -1 in the 10-cm MPBR plant.…”

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confidence: 76%

Improving membrane photobioreactor performance by reducing light path: operating conditions and key performance indicators

et al. 2020

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Microalgae cultivation has been receiving increasing interest in wastewater remediation due to their ability to assimilate nutrients present in wastewater streams. In this respect, cultivating microalgae in membrane photobioreactors (MPBRs) allows decoupling the solid retention time (SRT) from the hydraulic retention time (HRT), which enables to increase the nutrient load to the photobioreactors (PBRs) while avoiding the wash out of the microalgae biomass. The reduction of the PBR light path from 25 to 10 cm increased the nitrogen and phosphorus recovery rates, microalgae biomass productivity and photosynthetic efficiency by 150, 103, 194 and 67%, respectively. The areal biomass productivity (aBP) also increased when the light path was reduced, reflecting the better use of light in the 10-cm MPBR plant. The capital and operating operational expenditures (CAPEX and OPEX) of the 10-cm MPBR plant were also reduced by 27 and 49%, respectively. Discharge limits were met when the 10-cm MPBR plant was operated at SRTs of 3-4.5 d and HRTs of 1.25-1.5 d. At these SRT/HRT ranges, the 2 process could be operated without a high fouling propensity with gross permeate flux (J20) of 15 LMH and specific gas demand (SGDp) between 16 and 20 Nm 3 airꞏm-3 permeate, which highlights the potential of membrane filtration in MPBRs. When the continuous operation of the MPBR plant was evaluated, an optical density of 680 nm (OD680) and soluble chemical oxygen demand (sCOD) were found to be good indicators of microalgae cell and algal organic matter (AOM) concentrations, while dissolved oxygen appeared to be directly related to MPBR performance. Nitrite and nitrate (NOx) concentration and the soluble chemical oxygen demand:volatile suspended solids ratio (sCOD:VSS) were used as indicators of nitrifying bacteria activity and the stress on the culture, respectively. These parameters were inversely related to nitrogen recovery rates and biomass productivity and could thus help to prevent possible culture deterioration.

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“…Currently, selection or screening of microalgal strains with resistance to biological pollutants is considered as the most practicable approach to reducing contamination (Day et al. ; Wang et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…However, these methods have not been applied widely owing to the difficulties involved in their operation, or the high cost or damage they can cause to the microalgae. Currently, selection or screening of microalgal strains with resistance to biological pollutants is considered as the most practicable approach to reducing contamination (Day et al 2017;Wang et al 2013). In order to select or screen resistant strains, understanding the factors that affect the impact of P. malhamensis grazing on Chlorella cells is a critical first step.…”

Section: How Does Poterioochromonas Malhamensis Select Chlorella?mentioning

confidence: 99%

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Factors Affecting the Mixotrophic Flagellate Poterioochromonas malhamensis Grazing on Chlorella Cells

Wei

Wang

et al. 2019

J Eukaryotic Microbiology

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Grazing behaviour between protozoa and phytoplankton exists widely in planktonic ecosystems. Poterioochromonas malhamensis is a well‐known and widespread mixotrophic flagellate, which is recognized to play an important role within marine and freshwater planktonic ecosystems and regarded as the greatest contamination threat for mass algal cultures of Chlorella. In this study, a comprehensive range of factors, including morphological characters, biochemical compositions, and specific growth rate of ten species or strains of Chlorella, were evaluated for their effect on the feeding ability of P. malhamensis, which was assessed by two parameters: the clearance rate of P. malhamensis on Chlorella spp. and the specific growth rate of P. malhamensis. The results showed that the clearance rate of P. malhamensis was negatively correlated with cell wall thickness and specific growth rate of Chlorella spp., while the specific growth rate of P. malhamensis was positively correlated with carbohydrate percentage and C/N ratio and negatively correlated with protein, lipid percentage, and nitrogen mass. In conclusion, the factors influencing feeding selectivity include not only the morphological character and chemical composition of Chlorella, but also its population dynamics. Our study provides useful insights into the key factors that affect the feeding selectivity of P. malhamensis and provides basic and constructive data to help in screening for grazing‐resistant microalgae.

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Microzooplanktonic grazers – A potentially devastating threat to the commercial success of microalgal mass culture

Cited by 124 publications

References 88 publications

Genome analyses of the new model protist Euplotes vannus focusing on genome rearrangement and resistance to environmental stressors

Genome analyses of the new model protist Euplotes vannus focusing on genome rearrangement and resistance to environmental stressors

Improving membrane photobioreactor performance by reducing light path: operating conditions and key performance indicators

Factors Affecting the Mixotrophic Flagellate Poterioochromonas malhamensis Grazing on Chlorella Cells

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