Virustat, a device for continuous production of viruses

Methods for continuous production of viruses, and operation of the virustat, an apparatus in which such production was accomplished, were studied. Continuous production requires a separate continuous host growth chamber, such as the chemostat, and a multiunit virus growth chamber into which the virus-inoculated host cells are led. Successful continuous output of MS-2 and ϕX174 viruses, the latter in lysates, over periods of several days and at titers approximating those of batch lysates, was observed. Design problems include chamber sizes and flow rates, growth of resistant mutants within both virus and host growth chambers, clogging by lysis debris, and the phenomenon of self-inoculation. The latter represents virus growth in the first section of the chamber in excess of the washout rate, leading to lack of need for virus inoculation after an initial period. Use of the virustat for production and research purposes will require some attention to the formation of resistant bacterial colonies at pockets and surface sites of limited washout. With the virustat as a continuous virus production device, continuous purification methods are desirable. Research use of the virustat in continuous mutagenic population studies would require suppression of self-inoculation by use of many sections in the chamber, and improved servo control of host populations at low concentrations.     

Conversion of C-labeled substrates to volatile Fatty acids by the rumen microbiota

The fermentation of uniformly labeled glucose-C¹⁴, glucose-1-C¹⁴, -2-C¹⁴, and -6-C¹⁴, xylose-1-C¹⁴, cellulose-1-C¹⁴, -2-C¹⁴, and -6-C¹⁴, and lactate-2-C¹⁴ by rumen fluids from cows fed all-hay, hay and concentrate (50:50), and all-concentrate diets was investigated. The results obtained suggested that the Embden-Meyerhof glycolytic pathway is the major pathway of hexose utilization, that the major pathway of xylose fermentation involves hexose synthesis, and that the contributions of the nonrandomizing (acrylate) pathway of propionate formation during glucose, xylose, and cellulose fermentations are 4.5, 8.0, and 10.5%, and 24.6, 25.8, and 17.2%, respectively, by rumen fluids from the cows fed all-hay and all-concentrate rations.     

Changes in fungi with age. II. Respiration and respiratory enzymes of Rhizoctonia solani and Sclerotium bataticola

Van Etten, James L. (University of Illinois, Urbana), H. Peter Molitoris, and David Gottlieb. Changes in fungi with age. II. Respiration and respiratory enzymes of Rhizoctonia solani and Sclerotium bataticola. J. Bacteriol. 91:169-175. 1966.-The rate of respiration of Rhizoctonia solani and Sclerotium bataticola decreased with age. This decrease in respiratory rate might be produced by a decrease in the specific activity of one or more enzymes involved in carbohydrate metabolism. Specific activities in cell-free extracts were measured for most of the enzymes in the hexose monophosphate shunt, Embden-Meyerhof-Parnas pathway, tricarboxylic acid cycle, and terminal electron-transport system. In addition, glucose oxidase, isocitritase, and malic enzyme were measured. In R. solani, increases in activity with age occurred for hexokinase, alpha-glycerolphosphate dehydrogenase, malic dehydrogenase, and cytochrome oxidase. Decreases occurred for phosphohexokinase, aconitase, nicotinamide adenine dinucleotide-specific isocitric dehydrogenase, reduced nicotinamide adenine dinucleotide oxidase, and at least one of the enzymes between 3-phosphoglycerate and pyruvate. In S. bataticola, increases in activity with age were observed for phosphohexokinase, pyruvic dehydrogenase, fumarase, malic dehydrogenase, and malic enzyme, whereas none of the enzymes decreased. The specific activities of the remaining enzymes did not change with age in either fungus.     

Feedback regulation of arginine biosynthesis in blue-green algae and photosynthetic bacteria

Hoare, D. S. (The University of Texas, Austin), and S. L. Hoare. Feedback regulation of arginine biosynthesis in blue-green algae and photosynthetic bacteria. J. Bacteriol. 92:375-379. 1966.-A number of blue-green algae and photosynthetic bacteria synthesize arginine from glutamate via acetylated intermediates. Cell-free extracts of these photosynthetic microorganisms contain an N-acetyl glutamate phosphokinase, which is specifically inhibited by arginine. They also contain a transacetylase which forms ornithine from alphaN-acetyl ornithine and glutamate. The transacetylase appears to be specific for l-glutamate. Arginine synthesis and its regulation by feedback inhibition in photosynthetic microorganisms differ from that in Escherichia coli and other Enterobacteriaceae.     

Ribonucleic acid and ribosomes of Bacillus stearothermophilus

Saunders, Grady F. (University of Illinois, Urbana), and L. Leon Campbell. Ribonucleic acid and ribosomes of Bacillus stearothermophilus. J. Bacteriol. 91:332-339. 1966.-The ability of some thermophilic bacteria to grow at temperatures as high as 76 C emphasizes the remarkable thermal stability of their crucial macromolecules. An investigation of the ribonucleic acid (RNA) and ribosomes of Bacillus stearothermophilus was conducted. Washed log-phase cells were disrupted either by sonic treatment or by alumina grinding in 10(-2)m MgCl(2)-10(-2)m tris-(hydroxymethyl)aminomethane buffer, pH 7.4 (TM buffer). Ultracentrifugal analysis revealed peaks at 72.5S, 101S, and 135S, with the 101S peak being the most prominent. By lowering the Mg(++) concentration to 10(-3)m, the ribosome preparation was dissociated to give 40S, 31S, and 54S peaks. These in turn were reassociated in the presence of 10(-2)m Mg(++) to give the larger 73S and 135S particles. When heated in TM buffer, Escherichia coli ribosomes began a gradual dissociation at 58 C, and at 70 C underwent a large hyperchromic shift with a T(m) at 72.8 C. In contrast, B. stearothermophilus ribosomes did not show a hyperchromic shift below 70 C; they had a T(m) of 77.9 C. The thermal denaturation curves of the 4S, 16S, and 23S RNA from both organisms were virtually identical. The gross amino acid composition of B. stearothermophilus ribosomes showed no marked differences from that reported for E. coli ribosomes. These data suggest that the unusual thermal stability of B. stearothermophilus ribosomes may reflect either an unusual packing arrangement of the protein to the RNA or differences in the primary structure of the ribosomal proteins.