Ploidy levels and reproductive behaviour in invasive Hieracium pilosella in Patagonia

Within a population of invasive Hieracium pilosella in Chilean Patagonia we found two ploidy levels, pentaploid and hexaploid. Each ploidy level was represented by one clone. Their reproductive system was apomictic (and thus replicating the maternal genome), with a low degree of residual sexuality. It is necessary to prevent the evolution of new biotypes via hybridisation with different clones of H. pilosella or other Hieracium species introduced into Patagonia

Stepwise metabolic adaption from pure metabolization to balanced anaerobic growth on xylose explored for recombinant Saccharomyces cerevisiae

BACKGROUND: To effectively convert lignocellulosic feedstocks to bio-ethanol anaerobic growth on xylose constitutes an essential trait that Saccharomyces cerevisiae strains normally do not adopt through the selective integration of a xylose assimilation route as the rate of ATP-formation is below energy requirements for cell maintenance (m(ATP)). To enable cell growth extensive evolutionary and/or elaborate rational engineering is required. However the number of available strains meeting demands for process integration are limited. In this work evolutionary engineering in just two stages coupled to strain selection under strict anaerobic conditions was carried out with BP10001 as progenitor. BP10001 is an efficient (Y(ethanol) = 0.35 g/g) but slow (q(ethanol) = 0.05 ± 0.01 g/g(BM)/h) xylose-metabolizing recombinant strain of Saccharomyces cerevisiae that expresses an optimized yeast-type xylose assimilation pathway. RESULTS: BP10001 was adapted in 5 generations to anaerobic growth on xylose by prolonged incubation for 91 days in sealed flasks. Resultant strain IBB10A02 displayed a specific growth rate μ of 0.025 ± 0.002 h(-1) but produced large amounts of glycerol and xylitol. In addition growth was strongly impaired at pH below 6.0 and in the presence of weak acids. Using sequential batch selection and IBB10A02 as basis, IBB10B05 was evolved (56 generations). IBB10B05 was capable of fast (μ = 0.056 ± 0.003 h(-1); q(ethanol) = 0.28 ± 0.04 g/g(BM)/h), efficient (Y(ethanol) = 0.35 ± 0.02 g/g), robust and balanced fermentation of xylose. Importantly, IBB10A02 and IBB10B05 displayed a stable phenotype. Unlike BP10001 both strains displayed an unprecedented biphasic formation of glycerol and xylitol along the fermentation time. Transition from a glycerol- to a xylitol-dominated growth phase, probably controlled by CO(2)/HCO(3)(-), was accompanied by a 2.3-fold increase of m(ATP) while Y(ATP) (= 87 ± 7 mmol(ATP)/g(BM)) remained unaffected. As long as glycerol constituted the main by-product energetics of anaerobic growth on xylose and glucose were almost identical. CONCLUSIONS: In just 61 generation IBB10B05, displaying ~530% improved strain fitness, was evolved from BP10001. Its excellent xylose fermentation properties under industrial relevant conditions were proven and rendered it competitive. Based on detailed analysis of growth energetics we showed that m(ATP) was predominantly determined by the type of polyol formed rather than, as previously assumed, substrate-specific

Process intensification through microbial strain evolution: mixed glucose-xylose fermentation in wheat straw hydrolyzates by three generations of recombinant Saccharomyces cerevisiae

BACKGROUND: Lignocellulose hydrolyzates present difficult substrates for ethanol production by the most commonly applied microorganism in the fermentation industries, Saccharomyces cerevisiae. High resistance towards inhibitors released during pretreatment and hydrolysis of the feedstock as well as efficient utilization of hexose and pentose sugars constitute major challenges in the development of S. cerevisiae strains for biomass-to-ethanol processes. Metabolic engineering and laboratory evolution are applied, alone and in combination, to adduce desired strain properties. However, physiological requirements for robust performance of S. cerevisiae in the conversion of lignocellulose hydrolyzates are not well understood. The herein presented S. cerevisiae strains IBB10A02 and IBB10B05 are descendants of strain BP10001, which was previously derived from the widely used strain CEN.PK 113-5D through introduction of a largely redox-neutral oxidoreductive xylose assimilation pathway. The IBB strains were obtained by a two-step laboratory evolution that selected for fast xylose fermentation in combination with anaerobic growth before (IBB10A02) and after adaption in repeated xylose fermentations (IBB10B05). Enzymatic hydrolyzates were prepared from up to 15% dry mass pretreated (steam explosion) wheat straw and contained glucose and xylose in a mass ratio of approximately 2. RESULTS: With all strains, yield coefficients based on total sugar consumed were high for ethanol (0.39 to 0.40 g/g) and notably low for fermentation by-products (glycerol: ≤0.10 g/g; xylitol: ≤0.08 g/g; acetate: 0.04 g/g). In contrast to the specific glucose utilization rate that was similar for all strains (q(Glucose) ≈ 2.9 g/g(cell dry weight (CDW))/h), the xylose consumption rate was enhanced by a factor of 11.5 (IBB10A02; q(Xylose) = 0.23 g/g(CDW)/h) and 17.5 (IBB10B05; q(Xylose) = 0.35 g/g(CDW)/h) as compared to the q(Xylose) of the non-evolved strain BP10001. In xylose-supplemented (50 g/L) hydrolyzates prepared from 5% dry mass, strain IBB10B05 displayed a q(Xylose) of 0.71 g/g(CDW)/h and depleted xylose in 2 days with an ethanol yield of 0.30 g/g. Under the conditions used, IBB10B05 was also capable of slow anaerobic growth. CONCLUSIONS: Laboratory evolution of strain BP10001 resulted in effectively enhanced q(Xylose) at almost complete retention of the fermentation capabilities previously acquired by metabolic engineering. Strain IBB10B05 is a sturdy candidate for intensification of lignocellulose-to-bioethanol processes

Stage Center Theatre Newsletter- Feb. 2012

https://neiudc.neiu.edu/stagecenter/1036/thumbnail.jp

Stage Center Theatre Newsletter- Apr. 2012

https://neiudc.neiu.edu/stagecenter/1037/thumbnail.jp

Optimization of proprioceptive stimulation for echo-planar and inverse magnetic resonance imaging

In echo-planar imaging (EPI), the optimal passive movement parameters (rate and duration) for studying proprioceptive brain responses are unknown. The aim of this thesis was to test the effect of stimulus rate on brain responses evoked by proprioceptive stimulation in EPI. In addition, we attempted to develop a measurement protocol for experiments focused on proprioception in ultrafast inverse magnetic resonance imaging (InI) and investigate the amplitude of blood oxygen level-dependent (BOLD) signal at varying stimulus duration. This experimental setup was supposed to be applied in future connectivity studies of the proprioceptive brain network. We found that the optimum rate for right index finger proprioceptive stimulation in EPI varies from 3 to 6 Hz. While we managed to sample the BOLD responses every 100 ms (a 20-fold increase in temporal resolution compared to EPI), the experimental design in InI is challenging due to methodological constraints. Thus, the appropriate stimulation parameters for InI still remain a topic for further research

Variación citotípica y diversidad clonal en poblaciones poliploides y apomícticas de Pilosella (Compositae, Cichorieae) introducidas en el sur de la Patagonia

Introduction and objectives: The members of the genus Pilosella are native in Europe and Asia, but they are successful invasive species on most continents. These species form an agamic complex with common apomixis. Apomictic species hybridize, they have different degree of residual sexuality. Main aim of this paper was to determine if the interspecific hybridization already occurred in Patagonia. M&M: This study is based on analysis of seed progeny collected at thirteen populations of Pilosella in southern Argentina and Chile. The plants were examined for their taxonomic identity, DNA ploidy level (using flow cytometry), chromosome number, reproduction, formation of parthenogenetic seeds and clonal identity (using isozyme phenotypes). Results: No mixed-species population was recorded. Two apomictic clones of P. officinarum (one pentaploid and the other hexaploid) were found in populations: eight were hexaploid and one was mixed in cytotype composition. A new species for Patagonia, the apomictic pentaploid P. caespitosa, was represented by plants from two populations in Argentina. Some of the progeny plants cultivated from seeds sampled at three localities represented seed-fertile aneuploids the morphology of which implied a hybrid origin and indicated P. officinarum as one of the parents.  Conclusions: The presence of seed-fertile, aneuploid and parthenogenetic hybrids among the cultivated plants signifies an increased risk of the formation of new hybridogeneous genotypes of Pilosella in southern Patagonia. Introducción y objetivos: El género Pilosella es nativo de Europa y Asia, pero sus especies son plantas invasoras exitosas en la mayoría de continentes. Éstas especies forman un complejo agámico en el que la apomixis es común. Las especies apomícticas hibridan y presentan diferentes grados de sexualidad residual. El principal objetivo de este trabajo fue determinar la existencia de hibridación interespecífica en poblaciones del sur de la Patagonia. M&M: Este estudio está basado en el análisis de la descendencia de semillas de Pilosella recolectadas en trece poblaciones del Sur de Argentina y Chile. Las plantas fueron examinadas para determinar su identidad taxonómica, el nivel de ploidía de su ADN (empleando citometría de flujo), el número de cromosomas, el tipo de reproducción, la formación de semillas partenogenéticas y su identidad clonal (caracterizando fenotipos isoenzimáticos). Resultados: No se registró ninguna población mixta entre especies. Dos clones apomícticos de P. officinarum (uno pentaploide y otro hexaploide) fueron encontrados en varias poblaciones: ocho de ellas fueron determinadas como hexaploides; mientras que una presentó ambos citotipos. La presencia de la especie apomíctica y pentaploide P. caespitosa en dos poblaciones de Argentina supone el primer registro de esta especie en la Patagonia. Algunas semillas muestreadas en tres localidades mostraron una descendencia aneuploide fértil, cuya morfología indicó un origen híbrido con P. officinarum como una de las especies parentales. Conclusiones: La presencia de híbridos partenogenéticos, aneuploides y con semillas fértiles entre las plantas cultivadas, implica un aumento del riesgo de formación de nuevos genotipos híbridos de Pilosella en el sur de la Patagonia.