Fractionation of somatic and sperm chromatin during spermatogenesis in fish

A new approach is suggested for studying changes in the interactions of protein with DNA in the cells. Measurements of the buoyant density of chromatin were performed in somatic cells and in cells undergoing meiosis in fish. During the process of spermatogenesis some of the somatic histones on the DNA are replaced by a new class of proteins; consequently, the mature sperm contains a unique type of protein having a low mol. wt and a high proportion of arginine.The chromatin obtained from mature sperm is composed of a single component with a density of 1.48–1.49 g/cm³ as measured by CsCl equilibrium sedimentation. On the other hand, somatic cells contain chromatin with lower densities. Chromatin obtained from erythrocytes contains a single component with a density of 1.41–1.42 g/cm³ while liver chromatin shows two components; a main component with a density of 1.45–1.46 and a more heterogeneous component with a lighter density (1.32–1.35). There is a correlation between the buoyant density of the chromatin, the type of its basic proteins and the level of biosynthetic activity in the cells.     

Regulation of Nitrogen Fixation in Klebsiella pneumoniae: Evidence for a Role of Glutamine Synthetase as a Regulator of Nitrogenase Synthesis

Mutations causing constitutive synthesis of glutamine synthetase (GlnC(-) phenotype) were transferred from Klebsiella aerogenes into Klebsiella pneumoniae by P1-mediated transduction. Such GlnC(-) strains of K. pneumoniae have constitutive levels of glutamine synthetase. Two of three GlnC(-) strains of K. pneumoniae studied, each containing independently isolated mutations that confer the GlnC(-) phenotype, continue to synthesize nitrogenase in the presence of NH(4) (+). One strain, KP5069, produces 30% as much nitrogenase when grown in the presence of 15 mM NH(4) (+) as in its absence. The GlnC(-) phenotype allows the synthesis of nitrogenase to continue under conditions that completely repress nitrogenase synthesis in the wild-type strain. Glutamine auxotrophs of K. pneumoniae, that do not produce catalytically active glutamine synthetase, are unable to synthesize nitrogenase during nitrogen limited growth. Complementation of K. pneumoniae Gln(-) strains by an Escherichia coli episome (F'133) simultaneously restores glutamine synthetase activity and the ability to synthesize nitrogenase. These results indicate a role for glutamine synthetase as a positive control element for nitrogen fixation in K. pneumoniae.     

Growth of Pseudomonas C on C1 Compounds: Continuous Culture

Pseudomonas C was grown in continuous culture on methanol, formaldehyde, or formate as sole carbon source. On methanol mu(max) = 0.49/h and yield constant (Y) = 0.54; on formaldehyde and on unsupplemented media, mu(max) was about 0.2/h and Y was 0.15, whereas addition of p-aminobenzoic acid, folic acid, serine, or glycine to the medium raised Y to about 0.26 to 0.29, and addition of p-aminobenzoic acid, folic acid, serine, nicotinamide adenine dinucleotide, and Tween 80 raised the yield to 0.35. On formate and on unsupplemented media, mu(max) = 0.2/h and Y = 0.02, whereas addition of 0.1 mM p-aminobenzoic acid increased mu(max) to about 0.47 and Y to about 0.23. At low cell concentrations or growth rates a beneficial effect of CO(2) was observed. Formaldehyde or formate, when added together with methanol, were utilized simultaneously with the methanol.     

Rapid Plate Method for the Isolation of Lysogenic Bacteriophages

We have devised a rapid plate method for the detection and isolation of lysogenic phages and have used the procedure to screen 15 strains of Staphylococcus aureus. This method should prove applicable to a wide variety of bacterial species and should be especially valuable for those pathogens for which no phage-typing system is available.     

Light-scattering and infrared-spectrophotometric studies of chitin and chitin derivatives

A sample of chitin isolated from the shell of the crab Scylla serrata had, when in lithium thiocyanate solution, an average, weight-average molecular weight (1) of 1.036 x 10⁶ daltons, an intrinsic dissymmetry (2) of 1.93, and a Z-average radius of gyration (3) of 64.14 nm. Carboxymethylchitin and glycol chitin, in 0.5M sodium chloride, had, respectively, (1) 1.896 and 1.819 x 10⁶ daltons, (2) 3.25 and 4.31. and (3) 143.49 and 251.57 nm. They had similar degrees of polymerization, they underwent dissociation as the concentration of sodium chloride was increased to 2.5M, and the molecular packing of the chains was essentially side-by-side. Chitin in 5.55M lithium thiocyanate and carboxymethylchitin in 2.5M sodium chloride had similar degrees of polymerization. It is concluded that a small but significient number of the amino groups in the chitin molecule are not acetylated.     

Laboratory Studies with a Selective Enterococcus Medium

Lancefield group D streptococci are involved with appreciable frequency in a variety of infectious processes. The presumptive recognition of these bacteria on initial culturing of clinical specimens is an objective not attained readily by selective media available in the clinical laboratory. Selective Enterococcus agar was evaluated with emphasis on its ability to sequester enterococci from specimens with many microbial components. In addition, the sensitivity of this new agar was compared with Trypticase Soy agar containing sheep blood and Mitis Salivarius agar. All enterococci isolated from clinical material were classified in accordance with accepted biochemical and immunochemical criteria. The enterococci grew on the new medium as distinctive colonies surrounded by a black zone. Only Listeria monocytogenes presented similar colonial morphology after 48 hr. Most other bacteria did not grow at all or appeared markedly different. The sensitivity of the new agar was of the same order of magnitude as on blood or Mitis-Salivarius agars, but its selectivity was superior.     

Ecology of Staphylococci in a General Medical Service

Investigation of the ecology of Staphylococcus aureus on the medical service of the Cincinnati General Hospital was carried out from 1964 to 1970. S. aureus was cultured from 1,442 patients. Overall, there was a progressive increase in the susceptibility of S. aureus to commonly used antibiotics, but not to penicillin. Hospital-acquired S. aureus remained highly resistant to all antibiotics except penicillinase-resistant penicillins. There was a progressive decline in the percentage of hospital-acquired infections from January 1964 to September 1969, followed by a rise during September 1969 to September 1970. No single bacteriophage group predominated among nosocomially acquired S. aureus. Major changes in the hospital environment did not appear to influence the prevalence of nasal carriage or hospital acquisition of S. aureus. This study identified the continuing problem of acquisition of S. aureus in the hospital, but no specific "epidemic strain."     

Nucleic Acid Hybridization Studies within the Genus Cucurbita

The DNAs of Cucurbita species were examined by several methods. All Cucurbita DNAs have a similar CsCl isopycnic banding pattern consisting of a major band at 1.695 g/cc and a well separated satellite band at 1.707 g/cc. Compared to other plant and animal genera, Cucurbita species have a large genomic proportion of rDNA; this value ranging from 1.4% to 3.1%. The genomic proportion of rDNA was found not to be useful as a characteristic indicating degree of relatedness of the various Cucurbita species. However, Cucurbita DNAs can be distinguished by the extent to which their repetitive sequences cross-hybridize to each other and an assessment of species relationships can be made on this basis.