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81.
82.
Schäfer F Schuster J Würz B Härtig C Harms H Müller RH Rohwerder T 《Applied and environmental microbiology》2012,78(17):6280-6284
The Rieske nonheme mononuclear iron oxygenase MdpJ of the fuel oxygenate-degrading bacterial strain Aquincola tertiaricarbonis L108 has been described to attack short-chain tertiary alcohols via hydroxylation and desaturation reactions. Here, we demonstrate that also short-chain secondary alcohols can be transformed by MdpJ. Wild-type cells of strain L108 converted 2-propanol and 2-butanol to 1,2-propanediol and 3-buten-2-ol, respectively, whereas an mdpJ knockout mutant did not show such activity. In addition, wild-type cells converted 3-methyl-2-butanol and 3-pentanol to the corresponding desaturation products 3-methyl-3-buten-2-ol and 1-penten-3-ol, respectively. The enzymatic hydroxylation of 2-propanol resulted in an enantiomeric excess of about 70% for the (R)-enantiomer, indicating that this reaction was favored. Likewise, desaturation of (R)-2-butanol to 3-buten-2-ol was about 2.3-fold faster than conversion of the (S)-enantiomer. The biotechnological potential of MdpJ for the synthesis of enantiopure short-chain alcohols and diols as building block chemicals is discussed. 相似文献
83.
Differential regulation by organic compounds and heavy metals of multiple laccase genes in the aquatic hyphomycete Clavariopsis aquatica 总被引:2,自引:0,他引:2
Solé M Müller I Pecyna MJ Fetzer I Harms H Schlosser D 《Applied and environmental microbiology》2012,78(13):4732-4739
To advance the understanding of the molecular mechanisms controlling microbial activities involved in carbon cycling and mitigation of environmental pollution in freshwaters, the influence of heavy metals and natural as well as xenobiotic organic compounds on laccase gene expression was quantified using quantitative real-time PCR (qRT-PCR) in an exclusively aquatic fungus (the aquatic hyphomycete Clavariopsis aquatica) for the first time. Five putative laccase genes (lcc1 to lcc5) identified in C. aquatica were differentially expressed in response to the fungal growth stage and potential laccase inducers, with certain genes being upregulated by, e.g., the lignocellulose breakdown product vanillic acid, the endocrine disruptor technical nonylphenol, manganese, and zinc. lcc4 is inducible by vanillic acid and most likely encodes an extracellular laccase already excreted during the trophophase of the organism, suggesting a function during fungal substrate colonization. Surprisingly, unlike many laccases of terrestrial fungi, none of the C. aquatica laccase genes was found to be upregulated by copper. However, copper strongly increases extracellular laccase activity in C. aquatica, possibly due to stabilization of the copper-containing catalytic center of the enzyme. Copper was found to half-saturate laccase activity already at about 1.8 μM, in favor of a fungal adaptation to low copper concentrations of aquatic habitats. 相似文献
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85.
86.
Variable Responses of Lowland Tropical Forest Nutrient Status to Fertilization and Litter Manipulation 总被引:2,自引:0,他引:2
Emma J. Sayer S. Joseph Wright Edmund V. J. Tanner Joseph B. Yavitt Kyle E. Harms Jennifer S. Powers Michael Kaspari Milton N. Garcia Benjamin L. Turner 《Ecosystems》2012,15(3):387-400
Predicting future impacts of anthropogenic change on tropical forests requires a clear understanding of nutrient constraints
on productivity. We compared experimental fertilization and litter manipulation treatments in an old-growth lowland tropical
forest to distinguish between the effects of inorganic nutrient amendments and changes in nutrient cycling via litterfall.
We measured the changes in soil and litter nutrient pools, litterfall, and fine root biomass in plots fertilized with nitrogen
(N), phosphorus (P), or potassium (K), and in litter addition and litter removal treatments during 7 years. Soil inorganic
N and litter N increased in double-litter plots but not in N-fertilized plots. Conversely, litter P and soil pools of P and
K increased in fertilized plots but not in the double-litter plots. Soil and litter pools of N and K decreased in the no-litter
plots. Changes in litterfall with added nutrients or litter were only marginally significant, but fine root biomass decreased
with both the litter and the K addition. Differences between the two experiments are mostly attributable to the coupled cycling
of carbon and nutrients in litter. Increased nutrient inputs in litter may improve plant uptake of some nutrients compared
to fertilization with similar amounts. The litter layer also appears to play a key role in nutrient retention. We discuss
our findings in the context of possible impacts of anthropogenic change on tropical forests. 相似文献
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88.
The concept of "design space" has been proposed in the ICH Q8 guideline and is gaining momentum in its application in the biotech industry. It has been defined as "the multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters that have been demonstrated to provide assurance of quality." This paper presents a stepwise approach for defining process design space for a biologic product. A case study, involving P. pastoris fermentation, is presented to facilitate this. First, risk analysis via Failure Modes and Effects Analysis (FMEA) is performed to identify parameters for process characterization. Second, small-scale models are created and qualified prior to their use in these experimental studies. Third, studies are designed using Design of Experiments (DOE) in order for the data to be amenable for use in defining the process design space. Fourth, the studies are executed and the results analyzed for decisions on the criticality of the parameters as well as on establishing process design space. For the application under consideration, it is shown that the fermentation unit operation is very robust with a wide design space and no critical operating parameters. The approach presented here is not specific to the illustrated case study. It can be extended to other biotech unit operations and processes that can be scaled down and characterized at small scale. 相似文献
89.
Günther S Hübschmann T Rudolf M Eschenhagen M Röske I Harms H Müller S 《Journal of microbiological methods》2008,75(1):127-134
Analysis of environmental bacteria on the single cell level often requires fixation to store the cells and to keep them in a state as near life-like as possible. Fixation procedures should furthermore counteract the increase of autofluorescence, cell clogging, and distortion of surface characteristics. Additionally, they should meet the specific fixation demands of both aerobically and anaerobically grown bacteria. A fixation method was developed based on metal solutions in combination with sodium azide. The fixation efficiencies of aluminium, barium, bismuth, cobalt, molybdenum, nickel, and tungsten salts were evaluated by flow cytometric measurement of the DNA contents as a bacterial population/community stability marker. Statistical equivalence testing was involved to permit highly reliable flow cytometric pattern evaluation. Investigations were carried out with pure cultures representing environmentally important metabolic and respiratory pathways as controls and with activated sludge as an example for highly diverse bacterial communities. A mixture of 5 mM barium chloride and nickel chloride, each and 10% sodium azide was found to be a suitable fixative for all tested bacteria. The described method provided good sample stability for at least 9 days. 相似文献
90.
Kleinsteuber S Schleinitz KM Breitfeld J Harms H Richnow HH Vogt C 《FEMS microbiology ecology》2008,66(1):143-157
The microbial communities of in situ reactor columns degrading benzene with sulfate as an electron acceptor were analyzed based on clone libraries and terminal restriction fragment length polymorphism fingerprinting of PCR-amplified 16S rRNA genes. The columns were filled with either lava granules or sand particles and percolated with groundwater from a benzene-contaminated aquifer. The predominant organisms colonizing the lava granules were related to Magnetobacterium sp., followed by a phylotype affiliated to the genera Cryptanaerobacter/Pelotomaculum and several Deltaproteobacteria. From the sand-filled columns, a stable benzene-degrading consortium was established in sand-filled laboratory microcosms under sulfate-reducing conditions. It was composed of Delta- and Epsilonproteobacteria, Clostridia, Chloroflexi, Actinobacteria and Bacteroidetes. The most prominent phylotype of the consortium was related to the genus Sulfurovum, followed by Desulfovibrio sp. and the Cryptanaerobacter/Pelotomaculum phylotype. The proportion of the latter was similar in both communities and significantly increased after repeated benzene-spiking. During cultivation on aromatic substrates other than benzene, the Cryptanaerobacter/Pelotomaculum phylotype was outcompeted by other community members. Hence, this organism appears to be specific for benzene as a growth substrate and might play a key role in benzene degradation in both communities. Based on the possible functions of the community members and thermodynamic calculations, a functional model for syntrophic benzene degradation under sulfate-reducing conditions is proposed. 相似文献