Mountains play an important role in providing water resources from snow and ice to downstream urban population centers. In Utah, USA, nearly 86% of the state's population resides in the rapidly growing urban corridor along the Wasatch Front. Water along the Wasatch Front is stored in several deep reservoirs in the Provo River Watershed. Additions of nutrients, into these reservoirs, may stimulate the growth of primary producers (e.g., total phytoplankton and cyanobacteria) potentially attenuating water quality. To determine the influence of nutrients on primary producers in the Provo River's reservoirs, identify whether cyanobacteria are transported downstream, and quantify nutrient thresholds that regulate phytoplankton responses, we monitored and experimentally manipulated total phytoplankton and cyanobacteria in rivers and reservoirs. We found that total phytoplankton biomass (measured as chlorophyll a concentrations) was correlated with the total phosphorus (TP) in the Jordanelle Reservoir and the outflow from the Jordanelle Reservoir. Cyanobacteria biomass (measured as phycocyanin concentration) was correlated with dissolved inorganic N (DIN):SRP in the Deer Creek Reservoir and river sites below the Deer Creek Reservoir. Based on next generation sequencing 16S rDNA of all waters evaluated, the relative abundance of cyanobacteria within bacterial communities was extremely low, with the highest relative abundance of cyanobacteria present in the reservoirs being 10.7% for Deer Creek and 5.5% in Jordanelle during the late summer. Of the 25 genera of cyanobacteria that were found across all waters, five species have the ability to produce cyanotoxin: Microcystaceae; Aphanizomenon MDT14a; Aphanizominon NIES81; and Planktothrix NIVA-CYA. Season determined bacterial community composition in the river and reservoir over the almost two years of sampling with bacterial communities being distinct between the limnetic location in Deer Creek Reservoir to the outflow into the river immediately below the dam. We found no difference between the bacterial communities in the limnetic zone in Jordanelle and the river site directly below Jordanelle Dam. In the nutrient starvation bioassays, cyanobacteria and total phytoplankton responded to the nutrient additions, but there were no specific nutrient thresholds where pigment concentrations leveled out even as nutrient concentration increased. However, when P was added as SRP treatments both total phytoplankton and cyanobacteria concentrations increased, especially in the highest SRP treatment (0.08 mg/L) without any N addition. The addition of N alone did not influence total phytoplankton until there was at least 0.2 mg/L of P added. Further, cyanobacteria required at least 0.2 mg/L of SRP before responding to N levels above 0.8 mg/L. Thus, a nutrient threshold to maintain the reservoir at its current state would be 0.2 mg/L P and between 0.3 and 0.8 mg/L DIN. Our results identify that the water within the reservoirs and rivers are extremely clean and is in no immediate risk of extensive total phytoplankton or cyanobacterial blooms with P being the dominant driver of primary producer activity.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21470号 / 農博第2313号 / 新制||農||1064(附属図書館) / 学位論文||H31||N5165(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 北山 兼弘, 教授 本田 与一, 教授 舟川 晋也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(農学) / 甲第23617号 / 農博第2480号 / 新制||農||1088(附属図書館) / 学位論文||R4||N5365(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 德地 直子, 教授 北島 薫, 教授 舘野 隆之輔 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

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Les bétaïne lipides (BL) sont des lipides polaires qui se distinguent des phospholipides (PL)par l’absence de phosphore (P). La réorientation métabolique induite par une limitation en P chez des microalgues produisant des BL (Tisochrysis lutea et Diacronema lutheri, Haptophytes) ou en produisant peu (Phaeodactylum tricornutum, Bacillariophyte) a été comparée à celle induite par une limitation en azote (N). Le devenir et le flux de carbone dans différentes voies de biosynthèse ont été étudiés par une approche pluridisciplinaire.La limitation nutritive en P ou en N affecte différemment le métabolisme du carbone selon les espèces microalgales. La limitation en P réduit fortement l’activité photosynthétique et la respiration chez P. tricornutum et T. lutea. Par conséquent, l’accumulation de carbone est plus élevée que sous limitation en N chez ces deux espèces. Les deux limitations stimulent en particulier la synthèse des lipides neutres et / ou des glucides. Le remplacement des PL par les BL a été observé chez P. tricornutum en condition de limitation en P. Ce résultat est en accord avec une augmentation de la transcription du gène codant la bétaïne lipide synthase. En revanche, cette limitation ne modifie pas les teneurs en BL rapportées au carbone chez T. lutea et D. lutheri. La composition en acides gras des différentes classes lipidiques est modifiée selon l’espèce microalgale et l’élément nutritif limitant. Une attention particulière a été portée aux acides gras de la série oméga-3, notamment l’acide eicosapentaénoïque (EPA, 20:5 ω3) et l’acide docosahexaénoïque (DHA, 22:6 ω3) dont les proportions varient en fonction de l’élément limitant,de l’espèce et de la classe lipidique. L’augmentation de la production des lipides neutres et / ou des lipides polaires, notamment des bétaïne lipides, riches en DHA et/ou EPA induite par un stress nutritif laisse envisager une valorisation de ces molécules d’intérêt dans différents domaines dont la nutrition et la santé. / Betaine lipids (BL) are P-free polar lipids, conversely to phospholipids (PL). The metabolic reorientation induced by phosphorus (P) limitation in microalgae producing BL (Tisochrysis lutea and Diacronema lutheri, Haptophyta) or producing low levels of BL (Phaeodactylum tricornutum, Bacillariophyta) was compared to that induced by nitrogen (N) limitation. The carbon destiny and flow in different biosynthetic pathways were studied with a multidisciplinary approach. P or N limitation differently affected carbon metabolism according to microalgal species. P limitation highly decreased photosynthetic activity and respiration of P. tricornutum and T. lutea. Consequently, carbon accumulation was higher than under N limitation in these two species. Both limitations stimulated the synthesis of neutral lipids and / or carbohydrates. Replacement of PL by BL was observed in P. tricornutum under P limitation. This result is in agreement with a transcription increase of the gene encoding BL synthase. On the other hand, this limitation did not modify BL contents in reference with carbon in T. lutea or D. lutheri. Fatty acid composition of the different lipid classes was modified according to the microalgal species and the limiting nutrient. Particular attention was paid to the fatty acids of the omega-3 series, notably eicosapentaenoic acid (EPA, 20:5 ω3) and docosahexaenoic acid (DHA, 22:6 ω3), the proportions of which vary according to the limiting element, species and lipid class. The increase in the production of neutral lipids and / or polar lipids, especially betaine lipids, rich in DHA and / or EPA induced by nutritive stress suggests a valorization of these molecules of interest in various areas including nutrition and health.

As homeostatic organisms, rotifers have to use the mechanism to cope with nutrition unbalance in their food. The regulation of digestive enzyme activities as a possible physiological mechanism involved in maintaining of rotifer homeostasis was studied. This study further explored the effect of food quantity and quality on rotifer population growth rate and reproduction.

Phosphorus is frequently a limiting factor for phytoplankton in freshwater ecosystems, because algae and cyanobacteria are able to incorporate it only in a dissolved inorganic form. Phytoplankton evolved several mechanisms to overcome phosphorus limitation. One of them is the production of extracellular phosphatases. These enzymes are excreted on the surface of cells or released to the environment. They hydrolyze organic molecules containing phosphorus, which can be then incorporated by cells. This mechanism can influence the competitiveness of algae living in environments that are characterised by long-term phosphorus limitation (that is caused e.g. by the effect of low pH). In this study the influence of phosphorus concentration and form on extracellular phosphatase activity under laboratory conditions was investigated. The two experimental strains of the genus Coccomyxa (Chlorophyta) were isolated from acidified localities with different phosphorus availability  Plešné Lake and Hromnické Lake. Extracellular phosphatase activity on a single-cell level was measured using the FLEA technique and fluorescence microscopy. The FLEA technique allows direct visualization of phosphatases on the cell surface by incubating the samples with the artificial substrate ELF® 97 phosphate. Extracellular...

L’accumulation de lipides chez une espèce levurienne Yarrowia lipolytica souche sauvage a été caractérisée par l’analyse dynamique et systémique des différents états métaboliques identifiés lors des cultures sous conditions environnementales parfaitement maitrisées, à hautes densités cellulaires selon deux stratégies bien distinctes. En premier lieu sur substrat osidique avec le phosphore comme élément inducteur de l’accumulation de lipides, stratégie originale pour déclencher l’accumulation de lipides chez cette souche. Et deuxièmement sur co-susbtrats glucose et oléate et sans aucune limitation nutritionnelle.Ces stratégies de conduites ont permis de dégager les points suivants :- La limitation phosphore déclenche une accumulation en lipides mais aussi en polysaccharides de réserves mobilisables mais non transitoire contrairement à la limitation azote.- La teneur en phosphore de la biomasse catalytique est très variable. De ce fait, le taux de croissance de la biomasse catalytique n’est pas contrôlable par le débit en phosphore.- Le phosphore joue un rôle dans la régulation de l’entrée de glucose dans la cellule, et permet d’éviter la production de citrate lorsque les voies de production de biomasse et de lipides sont en débordement sur une large gamme de rapport C/P (de 0 à 8000 Cmole.mole-1).- La capacité maximale d’accumulation en réserves carbonées chez Y. lipolytica wT est identique quelle que soit la méthode d’accumulation (limitation azote, limitation phosphore, co-substrats glucose / oléate) et est égale à 0,5 Cmole/CmoleX-1. Il existe donc un phénomène de régulation de la levure encore inconnu et limitant l’accumulation en réserves carbonées chez cette souche.Ces résultats ont permis d’identifier des points clés dans l’accumulation en réserves carbonées de cette espèce levurienne et de proposer un mode de conduite original faisant l’objet d’un dépôt de brevet / Lipid accumulation by the yeast Yarrowia lipolytica wT was characterized by dynamic and systemic analysis of different metabolic states in a microbial culture under fully controlled environmental conditions with high cell concentration and under two different strategies:Glucose as the substrate and phosphorus limitation as an inducer of lipid accumulation, an original strategy for lipid accumulation in Y. lipolytica wT.A co-substrate strategy with glucose and oleic acid and without any nutritional limitation.These strategies allowed showing the following points:- Phosphorus limitation triggers a lipid accumulation and a non-transient accumulation of reserve polysaccharide that can be consumed by biomass when necessary, contrary to nitrogen limitation- Phosphorus rate in catalytic biomass shows great variations. Catalytic growth rate cannot be governed by phosphorus input. - Phosphorus has a role in regulating cellular glucose uptake and allows avoiding citric acid production due to overflow of carbon input over a large range of C/P ratios (0 to 8000 Cmol.mol-1)- Maximum capacity of reserve carbon accumulation in Y. lipolytica wT is similar for any culture strategy tested (under nitrogen limitation, phosphorus limitation or with glucose and oleic acid co-substrates) and is equal to 0,5 Cmol/CmolX-1. There is an unknown phenomenon of carbon regulation limiting reserve carbon accumulation in Y. lipolytica wT. Results allowed identifying key points in reserve carbon accumulation in this particular yeast strain and suggesting an original process, claim of a patent