Continuous growth on a substrate consisting of a mixture of glucose and fructose was studied. Growth below the critical dilution rate was measured as purely respiratory and both sugars were utilized equally and completely. At dilution rates greater than the critical, growth by fermentation and respiration was observed. Incomplete utilization of glucose and fructose was measured at dilution rates greater than approximately 0.40h-1. Batch studies using fructose, glucose and fructose, and sucrose with total initial concentrations of 20g/l, showed no significant differences compared to those carried out with initial sugar concentrations of 10g/l. However, in chemostat culture, washout of the sugars occurred at high dilution rates when the feed was 20g/l (of total sugar) but did not occur when the feed was 10g/l (of total sugar). Apparently this was indicative of the saturation of the sugar uptake mechanism rather than substrate repression. High inlet sugar concentration may cause less than complete utilization of sugars encountered industrially. There were two types of sugar uptake profile in batch cultures: uptake of glucose in preference to fructose, and equal uptake of the two sugars. The ability of the yeast to convert from one sugar uptake profile to the other during the course of a batch experiment over a small time period implies a pseudo-instantaneous switch in transport mechanisms and not new protein synthesis.
To trace the fate of heterologous rRNA operons in vivo, a complete rrn operon from P. vulgaris was transferred into the chromosome of E. coli. This was done by phage λgt11 and by plasmid pOM40 which promotes the integration of the cloned insert into the malP locus. As derived from oligonucleotide analysis of 16S rRNA isolated from ribosomal 30S subunits the amount of heterologous 16S rRNA in the ribosomes of corresponding clones was determined to be about 5% of the homologous E. coil 16S rRNA.
The effect of phenol on the growth and oxygen uptake rate was studied in several strains in the genus Rhodotorula, and the degradation route of phenol by two yeast strains of Rhodotorula rubra was examined. Rhodotorula rubra IFO 0870, 0889, 0892, 1100 and 1101 grew well in medium containing 250mg/l phenol. Rhodotorula rubra IFO 0870 still showed a small growth even in medium containing 1, 000mg/l phenol. It was found that oxidation of phenol in the cells of Rhodotorula rubra was partially inhibited by bipyridyl. Phenol metabolites were separated and identified using high performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS). The two phenol metabolites were identified as catechol and cis, cis-muconic acid. These findings suggest that phenol is hydroxylated prior to ring-cleavage and that a catechol branch in β-ketoadipate pathway exists in the yeast strains. Catechol may be oxidized by the "ortho type" of ring fission.
Glucose metabolism in Corynebacterium glutamicum was investigated using 13C nuclear magnetic resonance (13C NMR) spectroscopy. L-Glutamic acid and L-lysine producers were cultivated in medium containing [1-13C]- or [6-13C] glucose, and the 13C NMR spectrum of the culture filtrate was measured. In each fermentation, the ratio of the contributions of the Embden-Meyerhof pathway (EMP) and the hexosemonophosphate pathway (HMP) (EMP/HMP) was calculated on the basis of the 13C population at each carbon in the products. The EMP/HMP was estimated as 80/20 in glutamic acid fermentation; in contrast, it was 30-40/60-70 in lysine fermentation. These results indicate that HMP contributes much more in lysine fermentation, probably because of the greater requirement of NADPH in lysine formation from glucose.
This paper presents the inhibition of photosynthetic electron transport chain of Nostoc muscorum by divalent Ni2+ and monovalent Ag+. PS I (DCPIP/ASC→MV) and PS II (H2O→PBQ) activities were markedly inhibited by Ni2+ and Ag+ in a concentration-dependent fashion but PS II was more susceptible than PS I to Ni2+. Ag+ was more toxic to PS I than PS II. The greater sensitivity of PS II to Ni2+ was further confirmed by the inhibition of DCPIP photoreduction and Chl a fluorescence. Restoration of Ag+ -induced inhibition of DCPIP photoreduction and Chl a fluorescence by artificial electron donors (DPC, NH2OH, MnCl2) and their failure to restore Ni2+-induced inhibition suggests that Ni2+ inactivates PS II by causing alteration and destruction of photosynthetic membranes, but Ag+ inhibits the electron flow at the oxidizing side of PS II. Nevertheless, the suppression of the fluorescence intensity at low concentrations of both metal cations points to the involvement of phycobilisomes in the inhibition of PS II activity.
A new genus Kockovaella Nakase, Banno et Yamada in the Hyphomycetes is described for yeasts that reproduce by non-ballistosporous stalked conidia, ballistospores and budding yeast cells. Strains in this genus have Q-10 as the major isoprenologue of ubiquinones, contain xylose in the cells, and are positive to diazonium blue B reaction. Two new species, Kockovaella thailandica (type species) and K. imperatae, are described in the genus. Kockovaella thailandica has a G+C content of DNA of 49.5 mol% (from Tm) or 47.7-48.4mol% (by HPLC) and forms asymmetrical kidney-shaped or ellipsoidal ballistospores, whereas K. imperatae has a G+C content of DNA of 52.3mol% (from Tm) or 49.0mol% (by HPLC) and forms symmetrical globose to napiform ballistospores. Electrophoretic comparison of eight enzymes and DNA similarity indicated that K. thailandica and K. imperatae are distinct species from each other. The partial sequencing study on 18S ribosomal RNA suggested a close relationship among species of Kockovaella, Fellomyces and Sterigmatosporidium. The latter two genera resemble Kockovaella in the production of non-ballistosporous stalked conidia and the presence of xylose in the cells but produce neither ballistospores nor budding yeast cells.
The partial base sequences of 18S and 26S rRNAs of six strains of species in the genera Holleya, Nematospora, and Metschnikowia (Spermophthoraceae) were determined. The determinations of the partial base sequences (positions 1451 through 1618, 168 bases) of 18S rRNA have demonstrated that the genus Holleya is phylogenetically separable from the genera Nematospora and Metschnikowia, although the partial base sequences (positions 493 through 625, 133 bases; positions 1685 through 1835, 151 bases) of 26S rRNA in the genera Holleya and Nematospora were similar. Some discussions are presented from the taxonomic and phylogenetic points of view.
Differential scanning calorimetry (DSC) was used to study the interaction of platinum complexes with the linearized plasmid pJL3-TB5 DNA. An effective antitumor drug, cis-dichlorodiammineplatinum(II) (cis-DDP), caused the positions of DSC peaks to shift to a lower temperature range, showing that the heat stability of DNA decreases due to the adduct formed by the cis-DDP; the antitumor-inactive geometrical isomer trans dichlorodiammineplatinum(II) (trans-DDP) caused a larger variation in the melting profile than cis-DDP did. With another antitumor platinum complex, 1, 2-cyclohexanediamine(dach)platinum chloride (PtCl2(dach)), a complex with higher antitumor activity, the effect on the melting profile was smaller than that of others with less antitumor activity. These results show that the antitumor activity of platinum complexes is inversely proportional to their ability to disrupt DNA structure.
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Edited and published by : Applied Microbiology, Molecular and Cellular Biosciences Research Foundation/Center for Academic Publications Japan Produced and listed by : TERRAPUB, Center for Academic Publications Japan/Shobi Printing Co., Ltd. (-Vol.60,No12), Center for Academic Publications Japan/InternationalAcademic Printing Co., Ltd.(-Vol.54,No1)