Search results for "algae"
showing 10 items of 403 documents
Lichen microalgae are sensitive to environmental concentrations of atrazine
2017
The identification of new organisms for environmental toxicology bioassays is currently a priority, since these tools are strongly limited by the ecological relevance of taxa used to study global change. Lichens are sensitive bioindicators of air quality and their microalgae are an untapped source for new low-cost miniaturized bioassays with ecological importance. In order to increase the availability of a wider range of taxa for bioassays, the sensitivity of two symbiotic lichen microalgae, Asterochloris erici and Trebouxia sp. TR9, to atrazine was evaluated. To achieve this goal, axenic cultures of these phycobionts in suspension were exposed to a range of environmental concentrations of …
The toxicity of Roundup® 360 SL formulation and its main constituents: Glyphosate and isopropylamine towards non-target water photoautotrophs
2010
The toxicity of commercial formulation of Roundup® 360 SL, widely used, nonselective herbicide and its main constituents, glyphosate (PMG), equimolar (1:1) isopropylamine salt of glyphosate (GIPA) and isopropylamine (IPA) was examined towards eight aquatic microphotoautotrophs; seven cyanobacterial strains representing either saline or freshwater communities, and common eukaryotic algae Chlorella vulgaris Beijerinck. Autotrophs were cultured 21 days in their appropriate standard media supplemented with various amounts of Roundup®, glyphosate, GIPA and IPA. The determination of the growth of examined photoautotrophs was performed by time-course measurements of total chlorophyll content in ex…
Microalgae cultivation in wastewater: nutrient removal from anaerobic membrane bioreactor effluent
2012
This study investigated the removal of nitrogen and phosphorus from the effluent of a submerged anaerobic membrane bioreactor (SAnMBR) by means of a lab-scale photobioreactor in which algae biomass was cultured in a semi-continuous mode for a period of 42 days. Solids retention time was 2 days and a stable pH value in the system was maintained by adding CO2. Nitrogen and phosphorus concentrations in the SAnMBR effluent fluctuated according to the operating performance of the bioreactor and the properties of its actual wastewater load. Despite these variations, the anaerobic effluent proved to be a suitable growth medium for microalgae (mean biomass productivity was 234 mgl(-1) d(-1)), achie…
Ultrasound-assisted green solvent extraction of high-added value compounds from microalgae Nannochloropsis spp.
2015
Abstract The aim of this work was to investigate ultrasound (US)-assisted green solvent extraction of valuable compounds from the microalgae Nannochloropsis spp. Individual green solvents (water, ethanol (EtOH), dimethyl sulfoxide (DMSO)) and binary mixture of solvents (water-DMSO and water-EtOH) were used for the extraction procedures. Maximum total phenolic compounds yield ( Y p ≈ 0.33) was obtained after US pre-treatment ( W = 400 W, 15 min), being almost 5-folds higher compared to that found for the untreated samples and aqueous extraction ( Y p ≈ 0.06). The highest yield of total chlorophylls ( Y c ≈ 0.043) was obtained after US ( W = 400 W, 7.5 min), being more than 9-folds highe…
Assessing and modeling nitrite inhibition in microalgae-bacteria consortia for wastewater treatment by means of photo-respirometric and chlorophyll f…
2022
Abstract Total nitrite (TNO2 = HNO2 + NO−2) accumulation due to the activity of ammonia-oxidizing bacteria (AOB) was monitored in microalgae-bacteria consortia, and the inhibitory effect of nitrite/free nitrous acid (NO2-N/FNA) on microalgae photosynthesis and inhibition mechanism was studied. A culture of Scenedesmus was used to run two sets of batch reactors at different pH and TNO2 concentrations to evaluate the toxic potential of NO2-N and FNA. Photo-respirometric tests showed that NO2-N accumulation has a negative impact on net oxygen production rate (OPRNET). Chlorophyll a fluorescence analysis was used to examine the biochemical effects of NO2-N stress and the mechanism of NO2-N inhi…
The molecular architecture of the thylakoid membrane from various classes of eukaryotic algae
1990
There is convincing consensus that the photosynthetic apparatus is of prokaryotic origin. The wide variety of algal plastids is mostly assumed to be the result of different endocytological events. Chloroplasts surrounded by two membranes as in rhodophytes and chlorophytes were considered as the association of a prokaryotic symbiont and a eukaryotic host, whereas algae having a chloroplast surrounded with more than two membranes can be delineated from an endocytological event of two eukaryotes (see S. Gibbs in this volume). Since chlorophyll b was neither combined with chlorophyll c nor with phycobiliproteins it was proposed that all present day chloroplasts can be integrated in three lines.…
Calvin-Benson Cycle
2015
A carbon dioxide fixation pathway where a molecule of CO2 condenses with a 5-C compound (ribulose 1,5-bisphosphate) to yield two molecules of a 3-C compound (3-phosphoglycerate). These 3-C molecules serve both as precursors for biosynthesis and, through a cyclic series of enzymatic reactions, to regenerate the 5-C molecule necessary for the first carboxylating step (Fig. 1). The pathway is present in several bacterial lineages (e.g., cyanobacteria), and its acquisition by eukaryotic cells (chloroplast in algae and plants) was through the endosymbiotic association with ancient cyanobacteria.
Nitrate uptake rates in freshwater plankton: the effect of food web structure
2008
9 pages, 3 figure, 1 table
UV-C as an Efficient Means to Combat Biofilm Formation in Cultural Heritage Monument. Biodiversity and Impact on Prehistoric Pigments?
2018
Caves are considered oligotrophic habitats exhibiting constant temperature and relative humidity throughout the year. While darkness inhibits photosynthetic microorganism growth, introducing artificial lights to promote touristic activity can induce algae and cyanobacteria proliferation. Besides the aesthetic problem, microorganisms are responsible of physical and chemical degradation of limestone wall with possibly a degradation of prehistoric painting of cultural value. In our studies, we identified lampenflora with new-generation sequencing (NGS) in five French show caves and also on a 180, 000 years old contaminated bear bones (Ursus deningeroides). Afterward, we attempted to find an ec…
Biocoenosis and induration of freshwaterRivulariastromatolites in a temperate climate
1997
Freshwater Rivularia haematites (D.C.) Agardh and Rivularia biasolettiana Menegh‐ini stromatolites were collected from the Plateau de Langres and Lac d'Annecy (France) and investigated experimentally. In addition to cyanobacteria, the community of organisms consists of Desmococcus (green algae) and many bacteria including Agrobacterium tumefaciens and Pseudomonas diminuta for Rivularia haematites, and Achromobacter group B and Pseudomonas acidovorans for Rivularia biasolettiana. Stromatolite induration is not confined to calcification and may locally exhibit apatite or gypsum crystals, with the latter appearing only in cultures exposed to light. The effect of certain microorganisms of the b…