Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.     

Literature on archaeological remains of cultivated plants (1992/1993)

Publications on archaeological remains of cultivated plants have been collected, mainly from 1992 and 1993, with some earlier and later ones. A list is given of the finds according to taxon, country, site and age.     

Comparison of ccd of F, parDE of RP4, and parD of R1 using a novel conditional replication control system of plasmid R1

A number of plasmid-encoded gene systems are thought to stabilize plasmids by killing plasmid-free cells (also termed post-segregational killing or plasmid addiction). Here we analyse the mechanisms of plasmid stabilization by ccd of F, parDE of RP4 and parD of R1, and compare them to hok/sok of R1. To induce synchronous plasmid loss we constructed a novel plasmid replication-arrest system, which possesses the advantage that plasmid replication can be completely arrested by the addition of IPTG, a non-metabolizable inducer. Using isogenic plasmid constructions we have found, for the first time, consistent correlation between the effect on steady-state loss rates and the effect on cell proliferation in the plasmid replication-arrest assay for all three systems. The parDE system had the most pronounced effect both on plasmid stabilization and on plasmid retention after replication arrest. In contrast, ccd and parD both exhibited weaker effects than anticipated from previously published results. Thus, our results indicate that the function and efficiencies of some of the systems should be reconsidered. Our results are consistent with the previously postulated hypothesis that ccd and parDE act by killing plasmid-free segregants, whereas parD seems to act by inhibiting cell division of plasmid-free segregants.     

Is hydrogen peroxide a second messenger of salicylic acid in systemic acquired resistance?

Elevated levels of salicylic acid (SA) are required for the induction of systemic acquired resistance (SAR) in plants. Recently, a salicylic acid-binding protein (SABP) isolated from tobacco was shown to have catalase activity. Based on this finding elevated levels of hydrogen peroxide (H₂O₂) were postulated to act as a second messenger of SA in the SAR signal transduction pathway. A series of experiments have been carried out to clarify the role of H₂O₂ in SAR-signaling. No increase of H₂O₂ was found during the onset of SAR. Induction of the SAR gene, PR-1, by H₂O₂ and H₂O₂-inducing chemicals is strongly suppressed in transgenic tobacco plants that express the bacterial salicylate hydroxylase gene, indicating that H₂O₂ induction of SAR genes is dependent on SA accumulation. Following treatment of plants with increasing concentrations of H₂O₂, a dose-dependent accumulation of total SA species was found, suggesting that H₂O₂ may induce PR-1 gene expression through SA accumulation. While the results do not support a role for H₂O₂ in SAR signaling, it is suggested that SA inhibition of catalase activity may be important in tissues undergoing a hypersensitive response.     

Hydrophobic interaction of soluble 3′:5′ cyclic nucleotide phosphodiesterase with octyl-sepharose

Summary Soluble cyclic nucleotide 3:5 monophosphate phosphodiesterase (PDE) (EC 3.1.4.17) obtained from beef adrenal cortex as the 100,000 g/1.5 h supernatant is usually regarded as a very hydrophilic protein. However, when subjected to hydrophobic chromatography on Octyl-Sepharose CL 413 it reveals strong hydrophobic interaction with the column matrix. The chromatographic procedure leads to multiple but distinct forms of PDE which degrade cAMP beyond 5AMP to inosine, via adenosine. The same metabolic pathway was previously observed with a membrane bound multienzyme sequence. Even the soluble PDE forms separated by gel chromatography (Sephadex G 200, Sepharose S 200 and Sepharose 6B) and soluble PDE of other tissue (heart) displayed the same metabolic pattern. These findings indicate a linkage between PDE, nucleotidase and deaminase activities. The intimate association of the enzyme is additionally supported by the phenomenon of kinetic advantage clearly observed with the most hydrophobic PDE form. Its end product, inosine, is formed more rapidly from CAMP than from the intermediate 5AMP. This paradoxical phenomenon is explained by close physical proximity between the enzymes involved in the metabolic pathway. Furthermore, when the most hydrophobic PDE form was immobilized on Octyl-Sepharose, rather than loss of catalytic activity even higher enzyme activities were measured. It is suggested that the so-called multiple forms of soluble PDE-at least in part-represent more or less preserved forms of a native, membrane bound, multienzyme sequence which degrades cyclic nucleotides.     

Mass spectrometry of silylated flavonol O-glycosides

The electron impact mass spectra of 19 trimethyl silylated flavonol mono-, di- and -triglycosides are reported for the first time. All spectra show wel     

Heteropycnosis of an underreplicating chromosome

Drosophila nasutoides has an extraordinary genome since 62% of its DNA resides in chromosome4. This element mainly consists of constitutive heterochromatin which does not polytenize. Earlier studies of heterochromatin attributed little attention to the fact that condensed chromosomes often vary in condensation. This paper reports that chromosomes of the same complement display different degrees and kinetics of condensation. InD. nasutoides, even sex specific differences can be observed. The results of a comparative microphotometric study on neuroblast metaphases in both sexes revealed the following picture. The process of chromosome condensation is not restricted to mitotic prophase but continues into the metaphase. The mean condensation is not equal for all chromosomes. In the metaphase of the female, Feulgen density increases from theX chromosome, via3 and2, to chromosome4. In the male, the order isX, 2, 3, Y, and4. During the metaphase of the male, chromosomes condense with similar kinetics. In contrast, chromosomes of the female display asynchrony as monitored by area and length determinations. TheX chromosomes of the female probably have enhanced shortening during prophase. This would explain the metaphase of the female where theX chromosomes shorten less than the autosomes, and why each of theX chromosomes is 15% shorter than theX chromosome in the metaphase of the male. Further differences were observed in the longitudinal and lateral compaction of the chromosomes in males and females. The sex chromosomes and chromosome3 condense by shortening, while chromosomes2 and4 preferentially reduce their diameter. The large amount of DNA engaged in heteropycnosis and the isochromosome nature allow the identification of chromosome4 during interphase. At this stage, a new category of extreme DNA packaging was detected. The interphase density of chromosome4 can exceed that of metaphase by a factor of up to 8. Two events account for this high degree of condensation:(1) the homologues are particularly associated due to somatic pairing and (2) the arms are further tightened as a result of pericentric folding. The features of the isochromosome suggest that the interaction of chromatids during interphase is essentially caused by specific DNA sequences. The data confirm that heteropycnosis not only interferes with gene expression but also strongly inhibits DNA synthesis in endocycles.     

Continuous production of L-alanine from fumarate in a two-stage membrane reactor

Summary L-alanine was produced continuously from fumaric acid by means of soluble aspartase and L-aspartate--decarboxylase. The two reaction steps were carried out in two membrane reactors in series at different pH and temperature. The retention of the soluble enzymes within the reactor vessels was achieved by means of ultrafiltration membranes.     

Sequence complexity of poly(A) RNA fromPhysarum polycephalum

Summary Poly(A) RNA from S phase, G₂ phase and starved macroplasmodia of Physarum contain mRNA sequences which when translated in vitro, yield similar patterns of polypeptides after fluorography.Reassociation of nick-translated DNA (Cot) allows the isolation of highly labeled single copy DNA which, after saturation hybridization with poly(A) RNA, gives values of 23% for growth and 17% for starvation.Homologous cDNA/poly(A) RNA hybridization reactions (Rot) indicate that 22–28% of the genome is transcribed during growth and 12% during starvation and that about half of the cDNA reacts with 0.1% of the genome and could represent 50–80 RNA species, each present in about 1,000 copies per nucleus. Up to 25,000 different RNA species, 1–5 copies each per nucleus, are estimated to be present during growth, and about 15,000 during starvation. Heterologous cDNA/poly(A) RNA hybridization reactions (Rot) indicate that the RNA sequences in S and G₂ phase of the cell cycle are similar, with RNA sequences being more abundant in G₂ phase.During starvation about 25% of the sequences present during growth cannot be detected and those sequences present during growth have become diluted during starvation.