Low doses of the quaternary ammonium salt Cetyltrimethylammonium bromide can be used as a pesticide to control grazers in microalgal cultures

© 2019 Elsevier B.V. Contamination of large-scale microalgal cultures by grazers can cause huge losses in biomass productivity. Here we propose the use of a quaternary ammonium salt cetyltrimethylammonium bromide (CTAB) to eradicate three types of commonly occurring grazers in microalgal cultures: the rotifer Brachionus, the ciliate Sterkiella and the flagellate Paraphysomonas. Low, premicellar doses (≤3 μM) of CTAB rapidly eradicated (within 1–2 d) all three tested grazers from microalgal cultures without significant losses (p < 0.05) in microalgal productivity. However, doses exceeding 5 μM also negatively affected microalgal growth. The optimal dose of CTAB that resulted in complete eradication of the grazers with minimum impact on microalgal productivity was 3 μM for Brachionus, 2 μM for Sterkiella and 3 μM for Paraphysomonas. Thus, being a readily available chemical, CTAB has the potential to be used as a fast-acting, low-cost control agent against a range of frequently occurring grazer types in large-scale microalgal cultures.status: publishe

Модель професійної культури юриста: критерії та підходи

В статті визначається модель професійної культури

Modeling the impact of rotifer contamination on microalgal production in open pond, photobioreactor and thin layer cultivation systems

© 2018 Elsevier B.V. Contamination of microalgal cultures by rotifers is known to cause large losses in productivity. The factors that control population dynamics of rotifers in microalgal cultures were studied in controlled contamination experiments in laboratory cultures. These experiments revealed that rotifer growth rates increase with microalgae biomass at low rotifer population densities and declines with rotifer biomass as the rotifer population approaches a carrying capacity. Experimental results were used to construct a model that describes the impact of rotifer contamination on three types of large-scale microalgal cultures. The results of this model indicate that rotifer contamination causes a complete loss in productivity in open pond and closed photobioreactor cultivation systems. In contrast, losses in productivity are limited in thin layer cascade reactors because the rotifer population cannot achieve a sufficiently high population density to cause a crash of the culture. These results suggest that different cultivation systems respond differently to rotifer contamination.status: publishe

Grazers: the overlooked threat to sustained microalgae biomass production

status: publishe

Natural chemicals produced by marine microalgae as predator deterrents can be used to control ciliates contamination in microalgal cultures

Large-scale production of microalgae for biofuels is often hampered by contamination of cultures with predators that feed on microalgae. An important group of predators are ciliates. Some species of marine microalgae in natural ecosystems are known to produce chemicals that act as deterrents against predators. In this study, we tested whether these chemicals (trans,trans-2,4-decadienal, dimethyl sulfoniopropionate (DMSP), glycine betaine and proline) as well as a chemical analogue (methyl 3-(methylthio)propionate or MMP) can be used to control contamination of cultures of the microalga Chlamydomonas by the predatory ciliate Sterkiella. All chemicals were capable of rapidly eradicating the ciliates from a contaminated Chlamydomonas culture, but at a higher dose also had a negative effect on the microalga. For each chemical an optimal dose was determined at which ciliates were controlled and losses in microalgal biomass productivity were minimized (0.13 mM decadienal, 4.75 mM DMSP, 10 mM MMP, 250–300 mM proline and 250–300 mM glycine betaine). In the case of DMSP, MMP and proline, biomass productivity was even the same as that of a non-contaminated culture. The chemicals were also effective against other ciliates (Stylonychia notophora, Oxytricha sp. and 2 different Paramecium species). These chemicals therefore have potential to be used as natural pesticides to control contamination of microalgal cultures by ciliates. Of all chemicals tested, DMSP and MMP are the most promising because they are effective at a relatively low dose and have a limited negative effect on microalgal productivity.status: publishe

Radiogenomics Consortium Genome-Wide Association Study Meta-Analysis of Late Toxicity After Prostate Cancer Radiotherapy

Background: A total of 10%–20% of patients develop long-term toxicity following radiotherapy for prostate cancer. Identification of common genetic variants associated with susceptibility to radiotoxicity might improve risk prediction and inform functional mechanistic studies.Methods: We conducted an individual patient data meta-analysis of six genome-wide association studies (n=3871) in men of European ancestry who underwent radiotherapy for prostate cancer. Radiotoxicities (increased urinary frequency, decreased urinary stream, hematuria, rectal bleeding) were graded prospectively. We used grouped relative risk models to test associations with approximately 6 million genotyped or imputed variants (time to first grade 2 or higher toxicity event). Variants with two-sided Pmeta less than 5 X E-8 were considered statistically significant. Bayesian false discovery probability provided an additional measure of confidence. Statistically significant variants were evaluated in three Japanese cohorts (n=962). All statistical tests were two-sided.Results: Meta-analysis of the European ancestry cohorts identified three genomic signals: single nucleotide polymorphism rs17055178 with rectal bleeding (Pmeta = 6.2 X E-10), rs10969913 with decreased urinary stream (Pmeta = 2.9 X E-10), and rs11122573 with hematuria (Pmeta = 1.8 X E-8). Fine-scale mapping of these three regions was used to identify another independent signal (rs147121532) associated with hematuria (Pconditional = 4.7 X E-6). Credible causal variants at these four signals lie in gene-regulatory regions, some modulating expression of nearby genes. Previously identified variants showed consistent