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1.
Maris G. N. Hartmanis Henrik Åhlman Sten Gatenbeck 《Applied microbiology and biotechnology》1986,23(5):369-371
Summary
Clostridium acetobutylicum ATCC 824 was submitted to repeated subculturing at 24-hour intervals for 218 days. The organism retained its ability to form solvents, although the fermentation slowly became increasingly acidogenic during the first 200 days. Except for the initial spore inoculum, the cultures were not subjected to heat shocking between the serial transfers. When the inoculum volume was doubled from 3.3% to 6.7% after 200 days of subculturing, the product formation pattern quickly shifted back from acids to primarily butanol. Acetone production also resumed after being undetectable for more than 50 days. The relative formation of acetate and ethanol remained nearly constant throughout the experiments, while the formation of butyrate mirrored that of butanol. 相似文献
2.
The presence of species and their cover values together with soil and topographic characteristics were recorded at 40 sites along an altitudinal gradient of the Puna Belt at Pozuelos, in the High Andes in northwest Argentina. Classification and ordination of plant assemblages showed that soil and topography were the best predictors of the variation in species distribution. The different plant assemblages which occur along the topographic gradient follow the geographic variation in rainfall in this Andean region. Perennial bushes and grasses colonize the plains and slopes with fine textured soils which retain their water content. In contrast, deciduous bushes and cactuses grow on steep, rocky, dry slopes. Open woods also occur on east-facing steep, rocky slopes which are sheltered from winds. 相似文献
3.
P.C. Maris N.N. Joosten R.W. Goldbach & D. Peters 《Entomologia Experimentalis et Applicata》2004,113(3):149-155
The effect of thrips resistance in pepper (Capsicum annuum L.) – previously shown to result in impeded thrips population development (Maris PC, Joosten NN, Goldbach RW & Peters D (2003a) Restricted spread of Tomato spotted wilt virus in thrips‐resistant pepper. Phytopathology 93: 1223–1227. Maris PC, Joosten NN, Goldbach RW & Peters D (2003b) Spread of Tomato spotted wilt virus and population development of Frankliniella occidentalis in pepper resistant to thrips. Proceedings of the Section Experimental and Applied Entomology Netherlands Entomological Society (NEV) Amsterdam 14: 95–101.) – on thrips’[Frankliniella occidentalis Pergande (Thysanoptera: Thripidae)] reproduction, mortality, host preference, and behaviour was investigated. Reproduction, studied by oviposition and larval survival, was negatively affected by the thrips‐resistant (TR) phenotype, whereas the offspring's developmental rate did not differ on TR and the thrips‐susceptible (TS) phenotype. While thrips’ behaviour was hardly affected by thrips resistance, a significant preference for TS plants over the TR plants was found in different tests. When released on either a TR or a TS plant, thrips dispersed at significantly higher rates from the TR plants, demonstrating that not only an impeded reproduction, but also a reduced residence time adds to the reported lower thrips numbers on TR plants. 相似文献
4.
Two genetically engineered microorganisms (GEMs), Pseudomonas sp. strain B13 FR1(pFRC20P) (FR120) and Pseudomonas putida KT2440(pWWO-EB62) (EB62), were introduced into activated sludge microcosms that had the level of aeration, nutrient makeup, and microbial community structure of activated sludge reactors. FR120 contains an experimentally assembled ortho cleavage route for simultaneous degradation of 3-chlorobenzoate (3CB) and 4-methyl benzoate (4MB); EB62 contains a derivative TOL plasmid-encoded degradative pathway for toluene experimentally evolved so that it additionally processes 4-ethyl benzoate (4EB). Experiments assessed survival of the GEMs, their ability to degrade target substrates, and lateral transfer of plasmid-encoded recombinant DNA. GEMs added at initial densities of 10(6) to 10(7) bacteria per ml of activated sludge declined to stable population densities of 10(4) to 10(5) bacteria per ml. FR120 degraded combinations of 3CB and 4MB (1 mM each) following 3 days of adaptation in the microcosms. Indigenous microorganisms required an 8-day adaptation period before degradation of 4MB was observed; 3CB was degraded only after the concentration of 4MB was much reduced. The indigenous microbial community was killed when both compounds were present at concentrations of 4.0 mM. However, in parallel microcosms containing FR120, the microbial community maintained a normal density of viable cells. Indigenous microbes readily degraded 4EB (2 mM), and EB62 did not significantly increase the observed rate of degradation. In filter matings, transfer of pFRC20P, which specifies mobilization but not transfer functions, from FR120 to P. putida UWC1 was not detectable (< 10(-7) transconjugants per donor cell).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
Evolutionary variants of simian virus 40 which are impaired in early lytic functions but transform nonpermissive cells 总被引:3,自引:1,他引:2
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From an undiluted passaged virus stock, two size classes of defective simian virus 40 (SV40) DNA were isolated from which two evolutionary variants were cloned. By means of restriction enzyme and heteroduplex analysis, physical maps of the mutants have been constructed. Both mutants contained the region of SV40 DNA coding for the early proteins plus some adjacent sequences (the region from 0.120 to 0.685 map unit, clockwise, on the standard SV40 DNA map). Furthermore, each mutant contained, in the form of two inverted repeats, four times the sequences from the region 0.625 to 0.685 map unit, clockwise. Some biological properties of the mutant DNA were examined, and we found that the mutant DNA (i) has, as compared with SV40 DNA, an impaired ability to induce T antigen in permissive and nonpermissive cells; (ii) does not complement a thermosensitive A mutant of SV40; (iii) replicates very inefficiently without a helper; and (iv), as an apparent contradiction, transforms nonpermissive baby rat kidney cells as well as SV40 DNA. A hypothetical mechanism for the expression of the mutant DNA that might explain the observed biological properties is presented. 相似文献
6.
Expression and transfer of engineered catabolic pathways harbored by Pseudomonas spp. introduced into activated sludge microcosms. 总被引:2,自引:0,他引:2
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Two genetically engineered microorganisms (GEMs), Pseudomonas sp. strain B13 FR1(pFRC20P) (FR120) and Pseudomonas putida KT2440(pWWO-EB62) (EB62), were introduced into activated sludge microcosms that had the level of aeration, nutrient makeup, and microbial community structure of activated sludge reactors. FR120 contains an experimentally assembled ortho cleavage route for simultaneous degradation of 3-chlorobenzoate (3CB) and 4-methyl benzoate (4MB); EB62 contains a derivative TOL plasmid-encoded degradative pathway for toluene experimentally evolved so that it additionally processes 4-ethyl benzoate (4EB). Experiments assessed survival of the GEMs, their ability to degrade target substrates, and lateral transfer of plasmid-encoded recombinant DNA. GEMs added at initial densities of 10(6) to 10(7) bacteria per ml of activated sludge declined to stable population densities of 10(4) to 10(5) bacteria per ml. FR120 degraded combinations of 3CB and 4MB (1 mM each) following 3 days of adaptation in the microcosms. Indigenous microorganisms required an 8-day adaptation period before degradation of 4MB was observed; 3CB was degraded only after the concentration of 4MB was much reduced. The indigenous microbial community was killed when both compounds were present at concentrations of 4.0 mM. However, in parallel microcosms containing FR120, the microbial community maintained a normal density of viable cells. Indigenous microbes readily degraded 4EB (2 mM), and EB62 did not significantly increase the observed rate of degradation. In filter matings, transfer of pFRC20P, which specifies mobilization but not transfer functions, from FR120 to P. putida UWC1 was not detectable (< 10(-7) transconjugants per donor cell).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
van Leeuwen BN van der Wulp AM Duijnstee I van Maris AJ Straathof AJ 《Applied microbiology and biotechnology》2012,93(4):1377-1387
Isobutene (2-methylpropene) is one of those chemicals for which bio-based production might replace the petrochemical production
in the future. Currently, more than 10 million metric tons of isobutene are produced on a yearly basis. Even though bio-based
production might also be achieved through chemocatalytic or thermochemical methods, this review focuses on fermentative routes
from sugars. Although biological isobutene formation is known since the 1970s, extensive metabolic engineering is required
to achieve economically viable yields and productivities. Two recent metabolic engineering developments may enable anaerobic
production close to the theoretical stoichiometry of 1isobutene + 2CO2 + 2H2O per mol of glucose. One relies on the conversion of 3-hydroxyisovalerate to isobutene as a side activity of mevalonate diphosphate
decarboxylase and the other on isobutanol dehydration as a side activity of engineered oleate hydratase. The latter resembles
the fermentative production of isobutanol followed by isobutanol recovery and chemocatalytic dehydration. The advantage of
a completely biological route is that not isobutanol, but instead gaseous isobutene is recovered from the fermenter together
with CO2. The low aqueous solubility of isobutene might also minimize product toxicity to the microorganisms. Although developments
are at their infancy, the potential of a large scale fermentative isobutene production process is assessed. The production
costs estimate is 0.9 € kg−1, which is reasonably competitive. About 70% of the production costs will be due to the costs of lignocellulose hydrolysate,
which seems to be a preferred feedstock. 相似文献
8.
F. A. Maris E. Dingler S. Niehues 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,721(2):145
A validated HPLC method for the simultaneous quantitative analysis of the antidepressant mirtazapine and its demethyl metabolite in human plasma is described. The active constituents including internal standard were extracted from 1 ml of plasma with hexane and separated on a μBondapak Phenyl column with fluorescence detection. The lower limit of quantification was 0.5 ng/ml, without significant interferences with endogenous or exogenous components. Inter- and intra-assay accuracy determined at quality control levels of 2, 10 and 80 ng/ml were, respectively, 104.6–113.7% and 105.1–117.7% for mirtazapine, and 91.7–99.3% and 89.9–103.7% for demethylmirtazapine. In all cases the precision was below 6.8%. 相似文献
9.
10.
Nicky D'Haene Sébastien Sauvage Calliope Maris Ivan Adanja Marie Le Mercier Christine Decaestecker Linda Baum Isabelle Salmon 《PloS one》2013,8(6)