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991.
The growth of Gracilaria gracilis (Stackhouse) Steentoft, Irvine et Farnham was examined by studying the effect of organismic
determinants such as thallus length, position along the thallus and branching. Knowledge of these factors is essential in
order to increase production from suspended seaweed rafts seeded with vegetative G. gracilis fragments. Seeding netlons with
seaweed material freshly collected from subtidal populations provided up to 30% higher relative growth rates than seaweed
maintained on the netlons for successive months. Initial seedstock length greatly affected growth rates and yields such that
30-cm thalli fragments resulted in growth rates 14% higher than for 10-cm fragments. This difference is suggested to be due
to the higher contribution to overall biomass by growth of lateral branches. Comparisons of the growth of apical and basal
fragments suggest that growth takes place over the entire length of the thallus, but that the apex contributes more to overall
elongation than does the proximal part. The removal of apical meristems resulted in an enhanced branching frequency with production
of four times as many branches as intact fragments. Evidence is also provided for extensive morphological differentiation
following long periods of rapid growth. These thalli have very high frequency of branching, are hollow due to the disintegration
of medullary cells and are considered to be completely senescent. These factors have implications for the successful cultivation
of G. gracilis on commercial mariculture systems.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
992.
Martin E. de Swaaf Theo C. de Rijk Gerrit Eggink Lolke Sijtsma 《Journal of biotechnology》1999,70(1-3):185-192
The heterotrophic micro alga Crypthecodinium cohnii was cultivated in media containing glucose, yeast extract and sea salt. Increasing amounts of yeast extract stimulated growth but influenced lipid accumulation negatively. Sea salt concentrations above half the average seawater salinity were required for good growth and lipid accumulation. C. cohnii was able to grow on a glucose concentration as high as 84.3 g l−1, although concentrations above 25 g l−1 decreased the growth rate. Comparison of growth at 27 and 30°C showed that the higher incubation temperature was more favourable for growth. However, lipid accumulation was higher at the lower incubation temperature. In a bioreactor the biomass concentration increased from 1.5 to 27.7 g l−1 in 74 h. In the final 41 h of the process the lipid content of the biomass increased from 7.5 to 13.5%. In this period the percentage of docosahexaenoic acid of the lipid increased from 36.5 to 43.6%. The total amounts of lipid and docosahexaenoic acid after 91 h were 3.7 and 1.6 g l−1, respectively. 相似文献
993.
Characterization of a Novel β-Galactosidase from Bifidobacterium adolescentis DSM 20083 Active towards Transgalactooligosaccharides 下载免费PDF全文
Katrien M. J. Van Laere Tjakko Abee Henk A. Schols Gerrit Beldman Alphons G. J. Voragen 《Applied microbiology》2000,66(4):1379-1384
This paper reports on the effects of both reducing and nonreducing transgalactooligosaccharides (TOS) comprising 2 to 8 residues on the growth of Bifidobacterium adolescentis DSM 20083 and on the production of a novel β-galactosidase (β-Gal II). In cells grown on TOS, in addition to the lactose-degrading β-Gal (β-Gal I), another β-Gal (β-Gal II) was detected and it showed activity towards TOS but not towards lactose. β-Gal II activity was at least 20-fold higher when cells were grown on TOS than when cells were grown on galactose, glucose, and lactose. Subsequently, the enzyme was purified from the cell extract of TOS-grown B. adolescentis by anion-exchange chromatography, adsorption chromatography, and size-exclusion chromatography. β-Gal II has apparent molecular masses of 350 and 89 kDa as judged by size-exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively, indicating that the enzyme is active in vivo as a tetramer. β-Gal II had an optimal activity at pH 6 and was not active below pH 5. Its optimum temperature was 35°C. The enzyme showed highest Vmax values towards galactooligosaccharides with a low degree of polymerization. This result is in agreement with the observation that during fermentation of TOS, the di- and trisaccharides were fermented first. β-Gal II was active towards β-galactosyl residues that were 1→4, 1→6, 1→3, and 1↔1 linked, signifying its role in the metabolism of galactooligosaccharides by B. adolescentis. 相似文献
994.
Composition of Soil Microbial Communities Enriched on a Mixture of Aromatic Hydrocarbons 总被引:3,自引:1,他引:2 下载免费PDF全文
E. Anne Greene Jason G. Kay Karim Jaber Les G. Stehmeier Gerrit Voordouw 《Applied microbiology》2000,66(12):5282-5289
Soil contaminated with C5+, which contained benzene (45%, wt/wt), dicyclopentadiene (DCPD) plus cyclopentadiene (together 20%), toluene (6%), styrene (3%), xylenes (2%), naphthalene (2%), and smaller quantities of other compounds, served as the source for isolation of 55 genomically distinct bacteria (standards). Use of benzene as a substrate by these bacteria was most widespread (31 of 44 standards tested), followed by toluene (23 of 44), xylenes (14 of 44), styrene (10 of 44), and naphthalene (10 of 44). Master filters containing denatured genomic DNAs of all 55 standards were used to analyze the community compositions of C5+ enrichment cultures by reverse sample genome probing (RSGP). The communities enriched from three contaminated soils were similar to those enriched from three uncontaminated soils from the same site. The compositions of these communities were time dependent and showed a succession of Pseudomonas and Rhodococcus spp. before convergence on a composition dominated by Alcaligenes spp. The dominant community members detected by RSGP were capable of benzene degradation at all stages of succession. The enrichments effectively degraded all C5+ components except DCPD. Overall, degradation of individual C5+ hydrocarbons followed first-order kinetics, with the highest rates of removal for benzene. 相似文献
995.
The RING‐in‐between‐RING (RBR) E3s are a curious family of ubiquitin E3‐ligases, whose mechanism of action is unusual in several ways. Their activities are auto‐inhibited, causing a requirement for activation by protein‐protein interactions or posttranslational modifications. They catalyse ubiquitin conjugation by a concerted RING/HECT‐like mechanism in which the RING1 domain facilitates E2‐discharge to directly form a thioester intermediate with a cysteine in RING2. This short‐lived, HECT‐like intermediate then modifies the target. Uniquely, the RBR ligase HOIP makes use of this mechanism to target the ubiquitin amino‐terminus, by presenting the target ubiquitin for modification using its distinctive LDD region. 相似文献
996.
Effect of nitrate and nitrite on sulfide production by two thermophilic,sulfate-reducing enrichments from an oil field in the North Sea 总被引:1,自引:0,他引:1
Kaster KM Grigoriyan A Jenneman G Jennneman G Voordouw G 《Applied microbiology and biotechnology》2007,75(1):195-203
Thermophilic sulfate-reducing bacteria (tSRB) can be major contributors to the production of H2S (souring) in oil reservoirs. Two tSRB enrichments from a North Sea oil field, NS-tSRB1 and NS-tSRB2, were obtained at 58°C
with acetate-propionate-butyrate and with lactate as the electron donor, respectively. Analysis by rDNA sequencing indicated
the presence of Thermodesulforhabdus norvegicus in NS-tSRB1 and of Archaeoglobus fulgidus in NS-tSRB2. Nitrate (10 mM) had no effect on H2S production by mid-log phase cultures of NS-tSRB1 and NS-tSRB2, whereas nitrite (0.25 mM or higher) inhibited sulfate reduction.
NS-tSRB1 did not recover from inhibition, whereas sulfate reduction activity of NS-tSRB2 recovered after 500 h. Nitrite was
also effective in souring inhibition and H2S removal in upflow bioreactors, whereas nitrate was similarly ineffective. Hence, nitrite may be preferable for souring prevention
in some high-temperature oil fields because it reacts directly with sulfide and provides long-lasting inhibition of sulfate
reduction. 相似文献
997.
Metabolic engineering of lactic acid bacteria for the production of nutraceuticals 总被引:14,自引:0,他引:14
Hugenholtz J Sybesma W Groot MN Wisselink W Ladero V Burgess K van Sinderen D Piard JC Eggink G Smid EJ Savoy G Sesma F Jansen T Hols P Kleerebezem M 《Antonie van Leeuwenhoek》2002,82(1-4):217-235
Lactic acid bacteria display a relatively simple and well-described metabolism where the sugar source is converted mainly to lactic acid. Here we will shortly describe metabolic engineering strategies on the level of sugar metabolism, that lead to either the efficient re-routing of the lactococcal sugar metabolism to nutritional end-products other than lactic acid such as L-alanine, several low-calorie sugars and oligosaccharides or to enhancement of sugar metabolism for complete removal of (undesirable) sugars from food materials. Moreover, we will review current metabolic engineering approaches that aim at increasing the flux through complex biosynthetic pathways, leading to the production of the B-vitamins folate and riboflavin. An overview of these metabolic engineering activities can be found on the website of the Nutra Cells 5th Framework EU-project (www.nutracells.com). Finally, the impact of the developments in the area of genomics and corresponding high-throughput technologies on nutraceutical production will be discussed. 相似文献
998.
Johannes Betge Grainne Kerr Thilo Miersch Svenja Leible Gerrit Erdmann Christian L. Galata Tianzuo Zhan Timo Gaiser Stefan Post Matthias P. Ebert Karoline Horisberger Michael Boutros 《PloS one》2015,10(5)
Next generation sequencing (NGS) is an emerging technology becoming relevant for genotyping of clinical samples. Here, we assessed the stability of amplicon sequencing from formalin-fixed paraffin-embedded (FFPE) and paired frozen samples from colorectal cancer metastases with different analysis pipelines. 212 amplicon regions in 48 cancer related genes were sequenced with Illumina MiSeq using DNA isolated from resection specimens from 17 patients with colorectal cancer liver metastases. From ten of these patients, paired fresh frozen and routinely processed FFPE tissue was available for comparative study. Sample quality of FFPE tissues was determined by the amount of amplifiable DNA using qPCR, sequencing libraries were evaluated using Bioanalyzer. Three bioinformatic pipelines were compared for analysis of amplicon sequencing data. Selected hot spot mutations were reviewed using Sanger sequencing. In the sequenced samples from 16 patients, 29 non-synonymous coding mutations were identified in eleven genes. Most frequent were mutations in TP53 (10), APC (7), PIK3CA (3) and KRAS (2). A high concordance of FFPE and paired frozen tissue samples was observed in ten matched samples, revealing 21 identical mutation calls and only two mutations differing. Comparison of these results with two other commonly used variant calling tools, however, showed high discrepancies. Hence, amplicon sequencing can potentially be used to identify hot spot mutations in colorectal cancer metastases in frozen and FFPE tissue. However, remarkable differences exist among results of different variant calling tools, which are not only related to DNA sample quality. Our study highlights the need for standardization and benchmarking of variant calling pipelines, which will be required for translational and clinical applications. 相似文献
999.
Diel movements of Orange–Vaal smallmouth yellowfish Labeobarbus aeneus (Burchell, 1822) in the Vaal River, South Africa, were determined by externally attaching radio transmitters to 11 adult fish and manually tracking them between March and May 2012. Twenty-four radio telemetry monitoring surveys produced 2 304 diel tracks. At night, yellowfish displayed a preference for slow shallow (<0.3?m s?1, <0.5?m) and fast shallow habitats (>0.3?m s?1, <0.3?m), whereas by day they avoided these habitats, preferring fast deep areas (>0.3?m s?1, >0.3?m). The average total distance of 272?m moved per 24-hour period was three times greater than the diel range, and the average maximum displacement per minute was significantly higher in daytime (4?m) than at night (1.5?m). These findings suggest that L. aeneus is active primarily during the day in fast-flowing, deeper waters, and relatively inactive at night, when it occupies shallower habitats. This behaviour should be further explored to identify causal mechanisms underlying the diel habitat shifts in this species such as water temperature, foraging tactics and/or predator avoidance. 相似文献
1000.
The genetic code in mRNA is redundant, with 61 sense codons translated into 20 different amino acids. Individual amino acids are encoded by up to six different codons but within codon families some are used more frequently than others. This phenomenon is referred to as synonymous codon usage bias. The genomes of free-living unicellular organisms such as bacteria have an extreme codon usage bias and the degree of bias differs between genes within the same genome. The strong positive correlation between codon usage bias and gene expression levels in many microorganisms is attributed to selection for translational efficiency. However, this putative selective advantage has never been measured in bacteria and theoretical estimates vary widely. By systematically exchanging optimal codons for synonymous codons in the tuf genes we quantified the selective advantage of biased codon usage in highly expressed genes to be in the range 0.2–4.2 x 10−4 per codon per generation. These data quantify for the first time the potential for selection on synonymous codon choice to drive genome-wide sequence evolution in bacteria, and in particular to optimize the sequences of highly expressed genes. This quantification may have predictive applications in the design of synthetic genes and for heterologous gene expression in biotechnology. 相似文献