Curing of the killer deoxyribonucleic acid plasmids of Kluyveromyces lactis.

Ultraviolet irradiation gave rise to frequent curing of killer plasmids pGKl1 and pGK12 of Kluyveromyces lactis. Almost all of the nonkillers obtained lost both plasmids, but one of them lost only pGKl1. The disappearance of pGKl1 was accompanied by the simultaneous loss of the killer activity and of the resistance to the killer factor. A new plasmid, pGKl1S, was obtained, which arose from a deletion in the central region of pGKl1. Genetic analysis suggested that pGKl1S has the killer gene lost by the deletion and the resistance gene intact and that pGKl1S shares the same replication control with pGKl1.     

Does the rate of ribosomal RNA synthesis vary depending on the number of nucleoli in a nucleus?

Cultured kidney cells of Xenopus laevis were pulse-labeled with [³H]uridine for 10, 20 and 30 min during their logarithmic growth phase and then processed for autoradiography. The labeled cells were assigned into two categories, one- and two-nucleolated cells, and the rate of ribosomal RNA (rRNA) synthesis was measured by counting the number of grains in nucleoli. The results obtained revealed that a two-nucleolated cell incorporated significantly much more radioactivity into its nucleoli than did a one-nucleolated partner for all the periods examined. Cells of these different nucleolar types, however, contained essentially the same amount of rDNA (DNA complementary to rRNA) as estimated by in situ hybridization with [¹²⁵I]rRNA.Although it remains to be proved that the observed increase in incorporation represents the increased rate of rRNA synthesis in two-nucleolated cells, the present findings seem to be very interesting, since they might indicate that the activity of rRNA genes is in some way regulated or affected by their spatial relationship in a cell nucleus.     

Microbiological leaching of a chalcopyrite concentrate by Thiobacillus ferrooxidans

The microbiological leaching of a chalcopyrite concentrate has been investigated using a pure strain of Thiobacillus ferrooxidans. The optimum leaching conditions regarding pH, temperature, and pulp density were found to be 2.3, 35°C, and 22%, respectively. The energy of activation was calculated to be 16.7 kcal/mol. During these experiments the maximum rate of copper dissolution was about 215 mg/liters/hr and the final copper concentration was as high as 55 g/liter. This latter value is in the range of copper concentrations which may be used for direct electrorecovery of copper. Jarosite formation was observed during the leaching of the chalcopyrite concentrate. When the leach residue was reground to expose new substrate surface, subsequent leaching resulted in copper extractions up to about 80%. On the basis of this experimental work, a flow sheet has been proposed for commercial scale biohydrometallurgical treatment of high-grade chalcopyrite materials.     

Enzymatic synthesis of oligonucleotides of defined sequence. The "single addition" of 2(3)-O-dihydrocinnamoyl-nucleoside 5'-diphosphate to a primer oligonucleotide catalyzed by a thermophilic polynucleotide phosphorylase.

Several oligonucleotides of defined sequence were synthesized using 2'(3')-O-dihydrocinnamoyl-nucleoside 5'-diphosphates (DHC-NDP) as substrates for polynucleotide phosphorylase [EC 2.7.7.8] from Thermus thermophilus. The enzyme catalyzed the transfer of one nucleotidyl residue from each of the 2'(3')-O-dihydrocinnamoyl esters of CDP, UDP, and GDP to the 3'-terminus of the primer triadenosine diphosphate, (Ap)2A. The products were shown to be (Ap)3C, (Ap)3U, and (Ap)3G by enzymatic analysis.     

A case report on human type B botulism

A case of type B human botulism was found in Tochigi Prefecture in November, 1984. Botulinum type B toxin was detected in the serum and feces of the patient. The serum toxin was activated by trypsinization. Type B toxin was demonstrated in cooked meat medium cultures of the fecal specimens. The patient recovered after administration of type A, B, E and F quadrivalent antitoxin.     

Oxygen concentration-dependent induction of a 140-kDa protein in magnetic bacterium Magnetospirillum magnetotacticum MS-1

Abstract The magnetic bacterium Magnetospirillum magnetotacticum prefers a microaerobic habitat and should be able to sense oxygen. Therefore, the bacterium was cultured under atmospheres containing 0–5% O₂ and analyzed for oxygen-dependent changes in the levels of its protein components by sodium dodecyl sulfate-polyccrylamide gel electrophoresis (SDS-PAGE). The analysis revealed a marked anaerobic induction of a 140-kDa protein, which was suppressed when M. magnetotacticum was switched from microaerobic (<1% O₂) to aerobic (>1% O₂) growth conditions. Although its function remains to be determined, the 140-kDa protein may serve as a useful tool to gain insight into the physiology of the organism.