The respiratory ubiquinones (coenzyme Q) have an important part in the modern taxonomy of the yeasts. The coenzyme Q of sixty-eight yeasts belonging to seven genera (Hansenula, Debaryomyces, Dekkera, Brettanomyces, Hanseniaspora, Kloeckera and Lipomyces) has been investigated by means of high performance liquid chromatography (HPLC). HPLC chromatograms have exhibited minor peaks of coenzyme Q beside the major coenzyme Q revealed by the usual paper chromatography. It appears that those minor components of coenzyme Q may have some importance in the taxonomy of the yeasts at a generic level.
The effect of dissolved oxygen concentrations on the rate of biological oxidation of sulfide and elemental sulfur by the A-type sulfur-turf was examined. The rate of sulfide oxidation markedly increased concomitant with the increase in dissolved oxygen. Accompanying the sulfide oxidation, elemental sulfur was formed only a few minutes after the addition of hydrogen sulfide to the culture medium at a dissolved oxygen concentration of about 6ppm. The catalase test of the A-type sulfur-turf was negative. As hydrogen peroxide is a very reactive intermediate inevitably accompanying the biological reduction of oxygen to water, it is probable that hydrogen sulfide was oxidized by hydrogen peroxide. Consequently, these results could be explained if the production of hydrogen peroxide was more active under oxic than the microoxic conditions. On the other hand, the rate of the elemental sulfur oxidation was suppressed both at low (0.2ppm) and at high (3 to 6ppm) dissolved oxygen concentrations. The optimum was about 1.5ppm (Fig. 5). Therefore, it was concluded that the elemental sulfur oxidation by the A-type sulfur-turf was a microaerophilic reaction. Due to the continuous supply of anoxic water from a hot spring source, dissolved oxygen concentrations of the effluents where the A-type sulfur-turf occurred were kept under 1ppm (1). Accordingly, at these low concentrations of dissolved oxygen, it seems likely that the oxidation of elemental sulfur was maximized, while the production of toxic hydrogen peroxide was minimized. These assumptions are sufficient to account for the preference of the A-type sulfur-turf for the microoxic habitat.
The influence of redox potential (Eh) on biomethanation from H2 and CO2 by Methanobacterium thermoautotrophicum ΔH was studied in pH- controlled anaerobic batch cultures at 65°C in which the Eh of the culture medium was regulated by the addition of titanium(III)-citrate or potassium ferricyanide at values ranging from -315 to -500mV. The specific growth rate μ and the specific methane production rate QCH4 were optimum under the Eh range from -370 to -500mV, while it sharply decreased at the higher Eh range of -315 to -350mV. The maximum values of QCH4 and μ under the optimum environments were 5 (l CH4) (g cell)-1 hr-1 and 0.36hr-1, respectively.
A β-xylosidase gene from Bacillus subtilis was cloned via the expression vector pKK223-3 into E. coli. The resulting recombinant strain E. coli [pKK223-300] produced a xylosidase which was cell-wall bound. The enzyme was dissociated from the cell wall with CHAPS detergent, and purified by affinity chromatography. The active form of the enzyme was a tetramer with subunit molecular weight 65, 000. p-Nitrophenyl β- xyloside and xylobiose were substrates while other glycosides and cellobiose were not. The enzyme was most active at 50°C and pH 7. Activity was enhanced at high sodium chloride concentration and inhibited by xylose. A unique amino-terminal amino acid sequence (30 residues) was found which indicates that the subunits are identical. The amino acid composition differed from that of a B. pumilus β-xylosidase determined previously (CLAEYSSENS et al., Biochim. Biophys. Acta, 405, 475 (1975)). The two enzymes also differed in cell location, subunit activity, and inhibition characteristics.
Anaerobic growth of Saccharomyces carlsbergensis LAM 1068 was inhibited completely at the ethanol concentration of Pmg=95g/l. However, carbon dioxide still produced in a Warburg flask at the ethanol concentration higher than 95g/l. The minimum ethanol concentration for complete inhibition of fermentation was Pmf=195g/l. Based on this experimental observation a new kinetic equation is presented, in which the inhibitory effect of ethanol concentration (P) on the specific fermentation rate (q) is evaluated separately at both ranges of ethanol concentration. q/q0=a(1-P/Pmg)+b(1-P/Pmf) The above equation closely represented the experimental results. Comparison with the several kinetic models in the literature is discussed.
Dual coenzyme-specific glutamate dehydrogenase (GDH) is regulated by extracellular concentrations of ammonia in members of the Bacteroidesfragilis group, including B. fragilis, B. ovatus, B. distasonis, and B. vulgatus, as shown previously in B. fragilis (YAMAMOTO et al., J. Gen. Appl. Microbiol., 30, 499 (1984); J. Gen. Microbiol., 133, 2773 (1987)). High specific activities of GDH were observed in extracts prepared from the respective species grown with limited amounts of ammonia, and GDHs were inactivated by adding NH4Cl at high concentrations to cultures growing with limited amounts of ammonia. The values of Km of GDHs from the bacterial species were in ranges of 1-5mM, 0.14-0.7mM, and 0.006-0.02mM for NH4Cl, 2-oxoglutarate, and NADPH, respectively, and the optimum pHs were around 8.0 in the reductive amination. GDH activities in the four species were inhibited to the same extent by an antiserum prepared against the B. fragilis GDH, and immunoprecipitin bands fused with each other without a spur in a double immunodiffusion test. Activities of glutamine synthetase and glutamate synthase were also found but were 1% of the NADPH-activities of GDH in all the bacterial species.
The a-mating type cells of the basidiomycetous yeast Rhodosporidiumtoruloides were able to form mating tubes in response to the mating hormone, rhodotorucine A, given during 10min after the initiation of the bud emergence. The cells lost the susceptibility to the hormone after this period, and initiated DNA synthesis. It was indicated that commitment to mitosis occurred late in the G1 phase, prior to DNA replication, and that this commitment coincided with termination of the stage when the cells were morphologically susceptible to the hormone.
Nine strains of ballistospore-forming yeasts were isolated from dead leaves of various kinds of plants in Japan and were found to comprise a single, hitherto undescribed species of the genus Sporobolomyces. The species is described here as Sporobolomyces yamatoanus Nakase, Suzuki et Itoh. Sporobolomyces yamatoanus produces large, sickle-shaped to kidney- shaped ballistospores, produces pale colored colonies, has Q-9 as the major isoprenologue of the ubiquinones, and does not contain xylose in the cells. These characteristics coincide well with those of species placed in the intermedius group, a group of atypical species in the genus Sporobolomyces. This is the seventh species in the intermedius group.