An apparatus for the continuous culture of bacteria at constant generation times

Summary An apparatus for continuous culture of bacteria at constant generation times is described, analogous toNovick andSzilard's “chemostat” and the apparatus ofMonod. Detailed instructions for the use of the apparatus are given and a method for the determination of the vessel constant is described. The theory and the interesting possibilities of the apparatus for a number of fundamental problems in bacteriology are shortly discussed.     

Molecule-size distribution of soluble hiunic compounds from different natural waters

It this study the use of Sephadex G-25, Sephadex LH-20 and CPG-10-75 for the separation of soluble humic compoutids frotn fresh water is tested. It is shown by Sephadex G-25 gel filtration that differences in molecule-size distribution of soluble humic compounds in one lake at different titnes and between lakes can be predicted by E₂₅₀ and E₃₆₅ measurements.     

Numerical variation of nucleolar organizer regions after silver staining in domestic and wild Suidae (Mammalia)

Selective silver staining was used to investigate the cellular distribution of numbers of nucleolar organizer regions (NORs) in domestic pigs (Sus scrofa) of eight different breeds, the European wild boar (S. scrofa scrofa), Indonesian wild boar (S. scrofa vittatus), Javan warty pig (S. verrucosus), Sulawesi warty pig (S. celebensis), and pigmy hog (S. salvanius). In the domestic pig as well as in the wild (sub)species of Sus, actively transcribing ribosomal RNA genes were found to be present in the secondary constrictions of chromosome pairs 10 and 8. Chromosomes 10 were consistently Ag-positive. Chromosomes 8 less frequently showed Ag-NORs, resulting in different mean numbers of Ag-NORs per individual animal. Mean Ag-NOR numbers per breed or (sub)species were generally higher in the wild representatives of Sus than in the domestic breeds. The highest mean numbers of Ag-NORs were observed in the Meishan breed and in S. celebensis and S. salvanius. The Meishan breed appears to be conservative in Ag-NOR staining pattern, being more comparable to the Asian wild Suidae than to the European breeds.     

Phage reproduction in relation to bacterial growth rate

Summary The reproduction of bacteriophages T₁–T₇ inE. coli B growing in a continuous culture apparatus at constant generation times of 50′ and 150′ was studied in a defined medium with a high concentration of glucose and in a medium with glucose as a limiting factor. It was shown that the propagation rate (as measured by the latent period) of phages T₂, T₄, T₆ and T₇ decreased with longer bacterial generation times and with reduced energy- and carbon-supply. In contrast the reproduction of phages T₁, T₃ and T₅ (which are mainly synthesized from the contents of the host cell) was unaffected by the slowing down of bacterial metabolism.