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31.
Host-controlled Restriction of T-even Bacteriophages: Relation of Four Bacterial Deoxyribonucleases to Restriction 总被引:4,自引:7,他引:4
Escherichia coli strains B and K-12, which restrict growth of nonglucosylated T- even phage (T(*) phage), and nonrestricting strains (Shigella sonnei and mutants of E. coli B) were tested for levels of endonuclease I and exonucleases I, II, and III, by means of in vitro assyas. Cell-free extracts freed from deoxyribonucleic acid (DNA) were examined with three substrates: E. coli DNA, T(*)2 DNA, and T2 DNA. Both restricting and nonrestricting strains had comparable levels of the four nuclease activities and had similar patterns of preference for the three substrates. In addition, mutants of E. coli B and K-12 that lack endonuclease I were as effective as their respective wild types in restricting T(*) phage. 相似文献
32.
Madritsch Silvia Bomers Svenja Posekany Alexandra Burg Agnes Birke Rebekka Emerstorfer Florian Turetschek Reinhard Otte Sandra Eigner Herbert Sehr Eva M. 《Plant molecular biology》2020,104(4-5):379-380
Plant Molecular Biology - In the above mentioned publication, part of Fig. 6B was distorted (extra diagonal lines appeared). The original article has been corrected and the proper version... 相似文献
33.
Assortative mating preferences between colour morphs of the endemic Lake Tanganyika cichlid genus Tropheus 总被引:1,自引:1,他引:0
Bernd Egger Beate Obermüller Eva Eigner Christian Sturmbauer Kristina M. Sefc 《Hydrobiologia》2008,615(1):37-48
Female mate preferences effectuate reproductive isolation among and sexual selection within species. Both mechanisms have
been associated with the diversification and speciation of cichlid species flocks of the East African Great Lakes. In Lake
Tanganyika, the endemic genus Tropheus has diversified into >100 geographic colour morphs. Although distributed allopatrically at present, water level fluctuations
have repeatedly displaced and merged the benthic, rock-dwelling populations. Tests for assortative mating were performed to
explore the potential for reproductive isolation between morphs in secondary contact, and to assess the importance of sexual
selection for the diversification of this group. In contrast to other haplochromine cichlids, Tropheus is a sexually monochromatic, territorial and maternally mouthbrooding fish, which establishes temporary pair bonds prior
to spawning. Female mate preference trials involved two-way choices between a homotypic and a heterotypic male and were conducted
on allopatric populations of red and blue morphs from the southern part of Lake Tanganyika. Female affiliation time near each
male’s compartment did not predict the mate preferences subsequently expressed in unrestrained interactions after removal
of the compartment separators (spawning, pseudospawning and courtship). Consequently, mate preferences were inferred from
unrestrained interactions with one test male at a time in replicate observation sessions. Of the 23 females tested, 13 courted,
pseudospawned or spawned with the homotypic male, one blue female courted a red male, and nine females expressed no sexual
motivation. The assortative mate preferences in the experiments (P < 0.01) suggest that colour differentiation between Tropheus populations can effectuate reproductive isolation, and is consistent with the notion that sexual selection contributed to
the diversification of the genus.
Guest editors: T. Wilke, R. V?in?l? & F. Riedel
Patterns and Processes of Speciation in Ancient Lakes: Proceedings of the Fourth Symposium on Speciation in Ancient Lakes,
Berlin, Germany, September 4–8, 2006 相似文献
34.
Thomas Homann Carmen Tag Hanno Biebl Wolf-Dieter Deckwer Bernhard Schink 《Applied microbiology and biotechnology》1990,33(2):121-126
Summary Glycerol-fermenting anaerobes were enriched with glycerol at low and high concentrations in order to obtain strains that produce 1,3-propanediol. Six isolates were selected for more detailed characterization; four of them were identified as Citrobacter freundii, one as Klebsiella oxytoca and one as K. pneumoniae. The Citrobacter strains formed 1.3-propanediol and acetate and almost no by-products, while the Klebsiella strains produced varying amounts of ethanol in addition and accordingly less 1,3-propanediol. Enterobacterial strains of the genera Enterobacter, Klebsiella, and Citrobacter from culture collections showed similar product patterns except for one group which formed limited amounts of ethanol, but no propanediol. Seven strains were grown in pH-controlled batch cultures to determine the parameters necessary to evaluate their capacity for 1,3-propanediol production. K. pneumoniae DSM 2026 exhibited the highest final concentration (61 g/l) and the best productivity (1.7 g/l h) whereas C. freundii Zu and K2 achieved only 35 g/l and 1.4 g/l h, respectively. The Citrobacter strains on the other hand gave somewhat better yields which were very close to the theoretical optimum of 65 mol %.
Offprint requests to: H. Biebl 相似文献
35.
Tyrosine Hydroxylase Activity in Caudate Nucleus from Parkinson''s Disease: Effects of Iron and Phosphorylating Agents 总被引:1,自引:0,他引:1
Wolf-Dieter Rausch Yoko Hirata Toshiharu Nagatsu Peter Riederer† Kurt Jellinger‡ 《Journal of neurochemistry》1988,50(1):202-208
Tyrosine hydroxylase (TH) activity of human postmortem brain tissues from controls and patients with Parkinson's disease (PD) was examined in the presence of Fe2+ and phosphorylation agents, such as cyclic AMP, exogenous protein kinase, calcium plus calmodulin (Ca2+-CaM), and ATP. TH activity from parkinsonian tissue was increased by 48% with statistical significance in the presence of exogenous protein kinase. Cyclic AMP alone had no effect, whereas Ca2+-CaM increased the activity by only 10%. The presence of acetylcholine resulted in a slight decrease in enzyme activity. Human TH was stimulated 13.17-fold in the presence of 1 mM Fe2+. For iron dependence, no significant differences could be shown for the Km values of TH in striata of PD, while the activity of TH was half of that of controls. Here stimulation with 1 mM Fe2+ raised the activity of TH 11-fold. Stimulation of rat, gerbil, pig, and human caudate nucleus TH with Fe2+ shows remarkable species differences. In particular, the sensitivity of human TH to stimulating processes is noteworthy. H2O2 decreases TH activity only at high concentrations. Species differences are noted for the combined incubation of Fe2+ and H2O2. In the gerbil caudate nucleus, H2O2 does not prevent the stimulating properties of Fe2+, while the pig shows a dose-dependent decline of TH activity. In conclusion, there are no significant changes in the stimulating properties of human caudate nucleus TH activity with Fe2+ in PD, while such differences are noted by using exogenous protein kinase. Furthermore, experimental evidence shows that TH activity declines at high concentrations of H2O2 only. Potentiation of this effect by Fe2+ seems to be species-dependent. 相似文献
36.
37.
Yang Yang Rebekka Biedendieck Wei Wang Martin Gamer Marco Malten Dieter Jahn Wolf-Dieter Deckwer 《Microbial cell factories》2006,5(1):36-14
Background
During the last years B. megaterium was continuously developed as production host for the secretion of proteins into the growth medium. Here, recombinant production and export of B. megaterium ATCC14945 penicillin G amidase (PGA) which is used in the reverse synthesis of β-lactam antibiotics were systematically improved. 相似文献38.
High cell density cultivations were performed under identical conditions for two Bacillus megaterium strains (MS941 and WH320), both carrying a heterologous dextransucrase (dsrS) gene under the control of the xylA promoter. At characteristic points of the cultivations (end of batch, initial feeding, before and after induction) the proteome
was analyzed based on two dimensional gel electrophoresis and mass spectrometric protein identification using the protein
database "bmegMEC.v2" recently made available. 相似文献
39.
Pectic cell wall polysaccharides owe their high negative charge to the presence of D-galacturonate, a monosaccharide that appears to be present only in plants and some prokaryotes. UDP-D-galacturonate, the activated form of this sugar, is known to be formed by the 4-epimerization of UDP-D-glucuronate; however, no coding regions for the epimerase catalyzing this reaction have previously been described in plants. To better understand the mechanisms by which precursors for pectin synthesis are produced, we used a bioinformatics approach to identify and functionally express a UDP-D-glucuronate 4-epimerase (GAE1) from Arabidopsis. GAE1 is predicted to be a type II membrane protein that belongs to the family of short-chain dehydrogenases/reductases. The recombinant enzyme expressed in Pichia pastoris established a 1.3:1 equilibrium between UDP-D-galacturonate and UDP-D-glucuronate but did not epimerize UDP-D-Glc or UDP-D-Xyl. Enzyme assays on cell extracts localized total UDP-D-glucuronate 4-epimerase and recombinant GAE1 activity exclusively to the microsomal fractions of Arabidopsis and Pichia, respectively. GAE1 had a pH optimum of 7.6 and an apparent Km of 0.19 mm. The recombinant enzyme was strongly inhibited by UDP-D-Xyl but not by UDP, UDP-D-Glc, or UDP-D-Gal. Analysis of Arabidopsis plants transformed with a GAE1:GUS construct showed expression in all tissues. The Arabidopsis genome contains five GAE1 paralogs, all of which are transcribed and predicted to contain a membrane anchor. This suggests that all of these enzymes are targeted to an endomembrane system such as the Golgi where they may provide UDP-D-galacturonate to glycosyltransferases in pectin synthesis. 相似文献
40.
Stalz WD Greie JC Deckers-Hebestreit G Altendorf K 《The Journal of biological chemistry》2003,278(29):27068-27071
The addition of a His6 tag to the N terminus of subunit a of the F0 complex of the Escherichia coli ATP synthase allowed the purification of an ab2 subcomplex after solubilization of membranes with n-dodecyl-beta-d-maltoside and subsequent nickel-nitrilotriacetic acid affinity chromatography. After co-reconstitution of the ab2 subcomplex with purified subunit c, passive proton translocation rates as well as coupled ATPase activities after binding of F1 were measured that were comparable with those of wild type F0. The interaction between subunits a and b, which has been shown to be stoichiometric and functional, is not triggered by any cross-linking reagent and therefore reflects subunit interactions occurring within the F0 complex in vivo. 相似文献