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https://www.readbyqxmd.com/read/28092732/enhancement-of-lipid-productivity-by-adopting-multi-stage-continuous-cultivation-strategy-in-nannochloropsis-gaditana
#1
Min-Gyu Sung, Bongsoo Lee, Chul Woong Kim, Kibok Nam, Yong Keun Chang
In the present study, a novel process-based cultivation system was designed to improve lipid productivity of Nannochloropsis gaditana, an oleaginous microalga that has high potential for biofuel production. Specifically, four flat-panel photobioreactors were connected in series, and this system was subjected to continuous chemostat cultivation by feeding fresh medium to the first reactor at dilution rates of 0.028 and 0.056day(-1), which were determined based on Monod kinetics. The results show that the serially connected photobioreactor system achieved 20...
December 30, 2016: Bioresource Technology
https://www.readbyqxmd.com/read/28079055/intestinal-microbiota-as-a-tetrahydrobiopterin-exogenous-source-in-hph-1-mice
#2
Jaques Belik, Yulia Shifrin, Erland Arning, Teodoro Bottiglieri, Jingyi Pan, Michelle C Daigneault, Emma Allen-Vercoe
Tetrahydrobiopterin (BH4) is a cofactor of a number of regulatory enzymes. Although there are no known BH4 exogenous sources, the tissue content of this biopterin increases with age in GTP cyclohydrolase 1-deficient hyperphenylalaninemia-1 (hph-1) mice. Since certain bacteria are known to generate BH4, we hypothesize that generation of this biopterin by the intestinal microbiota contributes to its tissue increase in hph-1 adult mice. The goal of this study was to comparatively evaluate hph-1 mice and wild-type C57Bl/6 controls for the presence of intestinal BH4-producing bacteria...
January 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28074222/regulation-of-membrane-fixation-and-energy-production-conversion-for-adaptation-and-recovery-of-zno-nanoparticle-impacted-nitrosomonas-europaea
#3
Junkang Wu, Huijie Lu, Guangcan Zhu, Lianghui Chen, Yan Chang, Ran Yu
The ZnO nanoparticle (NP) effects on typical ammonia-oxidizing bacteria, Nitrosomonas europaea in a chemostat bioreactor, and the cells' toxicity adaptation and recovery potentials were explored. Hardly any inhibition was observed when the NP concentration was high up to 10 mg/L. The cells exposed to 50 mg/L ZnO NPs displayed time-dependent impairment and recovery potentials in terms of cell density, membrane integrity, nitrite production rate, and ammonia monooxygenase activity. The 6-h NP stress impaired cells were nearly completely restored during a 12-h recovery incubation, while the longer exposure time would cause irretrievable cell damage...
January 10, 2017: Applied Microbiology and Biotechnology
https://www.readbyqxmd.com/read/28073397/identification-of-new-members-of-the-escherichia-coli-k-12-mg1655-slya-regulon
#4
Thomas Curran, Fatima Abacha, Stephen Hibberd, Matthew Rolfe, Melissa Lacey, Jeffrey Green
SlyA is a member of the MarR family of bacterial transcriptional regulators. Previously, SlyA has been shown to directly regulate only two operons in Escherichia coli K-12 MG1655, fimB and hlyE (clyA). In both cases SlyA activates gene expression by antagonizing repression by the nucleoid associated protein H-NS. Here the transcript profiles of aerobic glucose-limited steady-state chemostat cultures of E. coli K-12 MG1655, slyA mutant and slyA over-expression strains are reported. The transcript profile of the slyA mutant was not significantly different to that of the parent; however, that of the slyA expression strain was significantly different from that of the vector control...
January 10, 2017: Microbiology
https://www.readbyqxmd.com/read/28072422/the-fitness-costs-and-trade-off-shapes-associated-with-the-exclusion-of-nine-antibiotics-by-ompf-porin-channels
#5
Katherine Phan, Thomas Ferenci
The trade-off relationship between antibiotic exclusion and nutrient access across the Gram-negative outer membrane is determined by structural constraints in porin channels. The precise nutritional cost of exclusion is unknown for different antibiotics, as are the shapes of the nutrition-susceptibility trade-off. Using a library of 10 engineered isogenic Escherichia coli strains with structural modifications of OmpF porin expressed at a constant level, susceptibilities were measured for nine antibiotics and the nutritional fitness costs estimated by competitions in chemostats...
January 10, 2017: ISME Journal
https://www.readbyqxmd.com/read/27995610/growth-rate-and-resource-imbalance-interactively-control-biomass-stoichiometry-and-elemental-quotas-of-aquatic-bacteria
#6
Casey M Godwin, Emily A Whitaker, James B Cotner
The effects of resource stoichiometry and growth rate on the elemental composition of biomass have been examined in a wide variety of organisms, but the interaction among these effects is often overlooked. To determine how growth rate and resource imbalance affect bacterial carbon (C): nitrogen (N): phosphorus (P) stoichiometry and elemental content, we cultured two strains of aquatic heterotrophic bacteria in chemostats at a range of dilution rates and P supply levels (C:P of 100:1 to 10,000:1). When growing below 50% of their maximum growth rate, P availability and dilution rate had strong interactive effects on biomass C:N:P, elemental quotas, cell size, respiration rate, and growth efficiency...
December 19, 2016: Ecology
https://www.readbyqxmd.com/read/27986600/effect-of-culture-residence-time-on-substrate-uptake-and-storage-by-a-pure-culture-of-thiothrix-ct3-strain-under-continuous-or-batch-feeding
#7
Francesco Valentino, Mario Beccari, Marianna Villano, Valter Tandoi, Mauro Majone
A pure culture of the filamentous bacterium Thiothrix, strain CT3, was aerobically cultured in a chemostat under continuous acetate feeding at three different culture residence times (RT 6, 12 or 22 d) and the same volumetric organic load rate (OLR 0.12gCOD/L/d). Cells cultured at decreasing RT in the chemostat had an increasing transient response to acetate spikes in batch tests. The maximum specific acetate removal rate increased from 25 to 185mgCOD/gCOD/h, corresponding to a 1.8 to 8.1 fold higher respective steady-state rate in the chemostat...
December 13, 2016: New Biotechnology
https://www.readbyqxmd.com/read/27974391/quantifying-in-situ-growth-rate-of-a-filamentous-bacterial-species-in-activated-sludge-using-rrna-rdna-ratio
#8
Vivi L Nguyen, Xia He, Francis L de Los Reyes
If the in situ growth rate of filamentous bacteria in activated sludge can be quantified, researchers can more accurately assess the effect of operating conditions on the growth of filaments and improve the mathematical modeling of filamentous bulking. We developed a method to quantify the in situ specific growth rate of Sphaerotilus natans (a model filament) in activated sludge using the species-specific 16S rRNA:rDNA ratio. Primers targeting the 16S rRNA of S. natans were designed, and real-time PCR and RT-PCR were used to quantify DNA and RNA levels of S...
November 2016: FEMS Microbiology Letters
https://www.readbyqxmd.com/read/27933040/dnra-and-denitrification-coexist-over-a-broad-range-of-acetate-n-no3-ratios-in-a-chemostat-enrichment-culture
#9
Eveline M van den Berg, Marissa Boleij, J Gijs Kuenen, Robbert Kleerebezem, Mark C M van Loosdrecht
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) compete for nitrate in natural and engineered environments. A known important factor in this microbial competition is the ratio of available electron donor and elector acceptor, here expressed as Ac/N ratio (acetate/nitrate-nitrogen). We studied the impact of the Ac/N ratio on the nitrate reduction pathways in chemostat enrichment cultures, grown on acetate mineral medium. Stepwise, conditions were changed from nitrate limitation to nitrate excess in the system by applying a variable Ac/N ratio in the feed...
2016: Frontiers in Microbiology
https://www.readbyqxmd.com/read/27916804/growth-phase-sterigmatocystin-formation-on-lactose-is-mediated-via-low-specific-growth-rates-in-aspergillus-nidulans
#10
Zoltán Németh, Ákos P Molnár, Balázs Fejes, Levente Novák, Levente Karaffa, Nancy P Keller, Erzsébet Fekete
Seed contamination with polyketide mycotoxins such as sterigmatocystin (ST) produced by Aspergilli is a worldwide issue. The ST biosynthetic pathway is well-characterized in A. nidulans, but regulatory aspects related to the carbon source are still enigmatic. This is particularly true for lactose, inasmuch as some ST production mutant strains still synthesize ST on lactose but not on other carbon substrates. Here, kinetic data revealed that on d-glucose, ST forms only after the sugar is depleted from the medium, while on lactose, ST appears when most of the carbon source is still available...
November 28, 2016: Toxins
https://www.readbyqxmd.com/read/27853594/homeostasis-of-metabolites-in-escherichia-coli-on-transition-from-anaerobic-to-aerobic-conditions-and-the-transient-secretion-of-pyruvate
#11
Nur Adeela Yasid, Matthew D Rolfe, Jeffrey Green, Mike P Williamson
We have developed a method for rapid quenching of samples taken from chemostat cultures of Escherichia coli that gives reproducible and reliable measurements of extracellular and intracellular metabolites by (1)H NMR and have applied it to study the major central metabolites during the transition from anaerobic to aerobic growth. Almost all metabolites showed a gradual change after perturbation with air, consistent with immediate inhibition of pyruvate formate-lyase, dilution of overflow metabolites and induction of aerobic enzymes...
August 2016: Royal Society Open Science
https://www.readbyqxmd.com/read/27833909/a-comparative-proteome-analysis-of-escherichia-coli-%C3%AE-rela-mutant-cells
#12
Sónia Carneiro, Silas Villas-Bôas, Eugénio C Ferreira, Isabel Rocha
The bacterial RelA-dependent stringent response exerts a strong influence over various processes. In this work, the impact of the relA gene mutation in Escherichia coli cells was evaluated by a quantitative proteomics analysis, employing stable-isotope labeling and high-resolution mass spectrometry. Chemostat cultures of E. coli W3110 and ΔrelA mutant strains were performed at two dilution rates (0.1 and 0.2 h(-1)) to assess the influence of the relA gene mutation in steady-state protein levels. A total of 121 proteins showed significant alterations in their abundance when comparing the proteome of mutant to wild-type cells...
2016: Frontiers in Bioengineering and Biotechnology
https://www.readbyqxmd.com/read/27807274/diverse-drug-resistant-subpopulations-of-mycobacterium-tuberculosis-are-sustained-in-continuous-culture
#13
Diepreye Ayabina, Charlotte Hendon-Dunn, Joanna Bacon, Caroline Colijn
Drug resistance to tuberculosis (TB) has become more widespread over the past decade. As such, understanding the emergence and fitness of antibiotic-resistant subpopulations is crucial for the development of new interventions. Here we use a simple mathematical model to explain the differences in the response to isoniazid (INH) of Mycobacterium tuberculosis cells cultured under two growth rates in a chemostat. We obtain posterior distributions of model parameters consistent with data using a Markov chain Monte Carlo (MCMC) method...
November 2016: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/27775385/competition-between-a-nonallelopathic-phytoplankton-and-an-allelopathic-phytoplankton-species-under-predation
#14
Jean-Jacques Kengwoung-Keumo
We propose a model of two-species competition in the chemostat for a single growth-limiting, nonreproducing resource that extends that of Roy [38]. The response functions are specified to be Michaelis-Menten, and there is no predation in Roy's work. Our model generalizes Roy's model to general uptake functions. The competition is exploitative so that species compete by decreasing the common pool of resources. The model also allows allelopathic effects of one toxin-producing species, both on itself (autotoxicity) and on its nontoxic competitor (phytotoxicity)...
August 1, 2016: Mathematical Biosciences and Engineering: MBE
https://www.readbyqxmd.com/read/27775379/competition-for-a-single-resource-and-coexistence-of-several-species-in-the-chemostat
#15
Nahla Abdellatif, Radhouane Fekih-Salem, Tewfik Sari
We study a model of the chemostat with several species in competition for a single resource. We take into account the intra-specific interactions between individuals of the same population of micro-organisms and we assume that the growth rates are increasing and the dilution rates are distinct. Using the concept of steady-state characteristics, we present a geometric characterization of the existence and stability of all equilibria. Moreover, we provide necessary and sufficient conditions on the control parameters of the system to have a positive equilibrium...
August 1, 2016: Mathematical Biosciences and Engineering: MBE
https://www.readbyqxmd.com/read/27703070/cap0037-a-novel-global-regulator-of-clostridium-acetobutylicum-metabolism
#16
Ngoc-Phuong-Thao Nguyen, Sonja Linder, Stefanie K Flitsch, Bettina Schiel-Bengelsdorf, Peter Dürre, Philippe Soucaille
: An operon comprising two genes, CA_P0037 and CA_P0036, that encode proteins of unknown function that were previously shown to be highly expressed in acidogenic cells and repressed in solventogenic and alcohologenic cells is located on the pSOL1 megaplasmid of Clostridium acetobutylicum upstream of adhE2 A CA_P0037::int (189/190s) mutant in which an intron was inserted at position 189/190 in the sense strand of CA_P0037 was successfully generated by the Targetron technique. The resultant mutant showed significantly different metabolic flux patterns in acidogenic (producing mainly lactate, butyrate, and butanol) and alcohologenic (producing mainly butyrate, acetate, and lactate) chemostat cultures but not in solventogenic or batch cultures...
October 4, 2016: MBio
https://www.readbyqxmd.com/read/27696371/comprehensive-reconstruction-and-in-silico-analysis-of-aspergillus-niger-genome-scale-metabolic-network-model-that-accounts-for-1210-orfs
#17
Hongzhong Lu, Weiqiang Cao, Liming Ouyang, Jianye Xia, Mingzhi Huang, Ju Chu, Yingping Zhuang, Siliang Zhang, Henk Noorman
Aspergillus niger is one of the most important cell factories for industrial enzymes and organic acids production. A comprehensive genome-scale metabolic network model (GSMM) with high quality is crucial for efficient strain improvement and process optimization. The lack of accurate reaction equations and gene-protein-reaction associations (GPRs) in the current best model of A. niger named GSMM iMA871, however, limits its application scope. To overcome these limitations, we updated the A. niger GSMM by combining the latest genome annotation and literature mining technology...
October 3, 2016: Biotechnology and Bioengineering
https://www.readbyqxmd.com/read/27684991/procedure-for-adaptive-laboratory-evolution-of-microorganisms-using-a-chemostat
#18
Haeyoung Jeong, Sang J Lee, Pil Kim
Natural evolution involves genetic diversity such as environmental change and a selection between small populations. Adaptive laboratory evolution (ALE) refers to the experimental situation in which evolution is observed using living organisms under controlled conditions and stressors; organisms are thereby artificially forced to make evolutionary changes. Microorganisms are subject to a variety of stressors in the environment and are capable of regulating certain stress-inducible proteins to increase their chances of survival...
2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/27637876/in-vivo-analysis-of-nh4-transport-and-central-n-metabolism-of-saccharomyces-cerevisiae-under-aerobic-n-limited-conditions
#19
H F Cueto-Rojas, R Maleki Seifar, A Ten Pierick, W van Helmond, M Pieterse M, J J Heijnen, S A Wahl
: Ammonium is the most common N-source for yeast fermentations. Although, its transport and assimilation mechanisms are well documented, there have been only few attempts to measure the in vivo intracellular concentration of ammonium and assess its impact on gene expression. Using an isotope dilution mass spectrometry (IDMS)-based method we were able to measure the intracellular ammonium concentration in N-limited aerobic chemostat cultivations using three different N-sources (ammonium, urea and glutamate) at the same growth rate (0...
September 16, 2016: Applied and Environmental Microbiology
https://www.readbyqxmd.com/read/27555881/elucidation-of-the-co-metabolism-of-glycerol-and-glucose-in-escherichia-coli-by-genetic-engineering-transcription-profiling-and-13-c-metabolic-flux-analysis
#20
Ruilian Yao, Dewang Xiong, Hongbo Hu, Masataka Wakayama, Wenjuan Yu, Xuehong Zhang, Kazuyuki Shimizu
BACKGROUND: Glycerol, a byproduct of biodiesel, has become a readily available and inexpensive carbon source for the production of high-value products. However, the main drawback of glycerol utilization is the low consumption rate and shortage of NADPH formation, which may limit the production of NADPH-requiring products. To overcome these problems, we constructed a carbon catabolite repression-negative ΔptsGglpK* mutant by both blocking a key glucose PTS transporter and enhancing the glycerol conversion...
2016: Biotechnology for Biofuels
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